Committee: Technical Sotware Deined Radio Forum Contribution Title: VITA-49 Drat Speciication Appendices Source Lee Pucker SDR Forum 604-828-9846 Lee.Pucker@sdrorum.org Date: 7 March 2007 Distribution: Post on Web Site, Members Only Document Summary: This provides appendices to the VITA speciication or moving data between an RF Front end and signal processing subsystem Notes o importance: None Impacts/Eects: Use o this document is expected to impact the work done by the Transceiver API Task group. Action Desired: None Action Required or Closure : None NOTICE This document has been prepared by VITA to assist the SDR Forum (or its successors or assigns). It is intended or discussion purposes only. It may be amended or withdrawn at a later time and it is not binding on any member o the SDR orum or on VITA. Use o this document is governed by the SDR Forum/VITA MOU.
VITA Radio Transport (VRT) Drat Standard VITA-49.0 2006 Drat 0.16 8 December 2006 This standard is being prepared by the VITA Standards Organization (VSO) and is unapproved. Do not speciy or claim conormance to this document. VSO is the Public Domain Administrator o this drat speciication, and guards the contents rom change except by sanctioned meetings o the task group under due process. VITA Standards Organization PO Box 19658 Fountain Hills, AZ 85269 Ph: 480-837-7486 Fax: Available upon request URL: www.vita.com
TABLE OF CONTENTS 1 Introduction... 6 2 VITA Inormation... 6 3 Reerences... 6 4 VRT Overview... 6 5 Compliance... 6 6 Data Packet Classes and Streams... 6 7 Context Packet Classes and Streams... 6 8 Inormation Classes and Streams... 6 Appendix A Inormation Stream Speciication Example... 7 Appendix B Context Field Examples... 8 Appendix B.1 Reerence Point Identiier Example...10 Appendix B.2 Spectral Fields Example...11 Appendix B.3 RF Reerence Frequency Oset Example...13 Appendix B.4 Bandwidth Frequency Oset Example...16 Appendix B.5 Frequency Translation Example...18 Appendix B.6 Reerence Level and Gain Example...24 Appendix B.7 Timestamp Adjustment Example...26 Appendix B.8 Data Packet Payload Format Examples...28 Appendix B.9 ECEF and Relative Ephemeris Example...36 Appendix B.10 Input Source Stream Association List Example...39 Appendix B.11 Vector Component Stream Association List Example...41 Appendix B.12 System Stream Association List Example...43 Appendix B.13 Extension Context Packet Stream Example...45
LIST OF FIGURES Figure B.1-1: Example block diagram with VRT Packet Stream generator symbols shown...8 Figure B.1-2: Example block diagram with VRT Packet Stream details shown...9 Figure B.1-1: Reerence Point Identiier Example...10 Figure B.2-1: Block diagram or Spectral Fields example...11 Figure B.2-2: Original and Translated Spectra and Spectral Parameters...11 Figure B.2-3: Context Packet Stream contents or Spectral Fields Example...12 Figure B.3-1: Block diagram or RF Reerence Frequency Oset Example...13 Figure B.3-2: Original and Translated Spectra or a single DDC...14 Figure B.3-3: Context Packet Stream contents or RF Reerence Frequency Oset Example...15 Figure B.4-1: Block diagram or Bandwidth Frequency Oset Example...16 Figure B.4-2: Original and Translated Spectra or Bandwidth Frequency Oset Example...16 Figure B.4-3: Context Packet Stream contents or Bandwidth Frequency Oset Example...17 Figure B.6-1: Block diagram or Gain and Reerence Level Example...24 Figure B.6-2: Level o Digital Receiver samples...25 Figure B.6-3: Level o DDC samples...25 Figure B.7-1: Block diagram or Timestamp Adjustment Example...26 Figure B.7-2 : Timing diagram or Timestamp Adjustment Example...27 Table B.8-1: Complex Polar Component Formats...28 Figure B.8-1: Data Packet Payload Format Field...28 Figure B.8-3: 32-bit Format...29 Figure B.8-4: 32-bit Complex Format...29 Figure B.8-5: 16-bit Format...30 Figure B.8-6: 16-bit Complex Format...30 Figure B.8-7: 8-bit Format...31 Figure B.8-8: 8-bit Complex Format...31 Figure B.8-9: Link-Eicient Packing...32 Figure B.8-10: Processing-Eicient Packing...32 Figure B.8-11: 14-bit Data Items in 16-bit Packing Fields...33 Figure B.8-12: Event Tags...33 Figure B.8-13: Sample Vector...34 Figure B.8-14: Sample Vector with Channel Tags...34 Figure B.8-15: Channel Repeating...35 Figure B.8-16: Sample Component Repeating or Complex Data Formats...35 Figure B.9-1: Location and attitude o antenna in the Relative Ephemeris Coordinate System...36 Figure B.9-2: Location and attitude o antenna in the ECEF Coordinate System...37 Figure B.9-3: Block diagram or ECEF and Relative Ephemeris Example...38 Figure B.10-1: Block diagram or Input Source List Example...39 Figure B.10-2: Representation o Input Source Stream Associations...39 Figure B.10-3: Association Diagram or the Input Source List Example...40 Figure B.11-1: Block diagram or Vector Component List Example...41 Figure B.11-2: Context Packet contents or the Vector Component List Example...41 Figure B.11-3: Association Diagram or the Vector Component List Example...42 Figure B.12-1: Block diagram or System List Example...43 Figure B.12-2: Representation o System Stream Associations...43 Figure B.12-3: Association Diagram o System List Example...44
LIST OF TABLES Error! No table o igures entries ound. SDR Forum Document Number SDRF-07-I-0007-V0.0.0
1 Introduction 2 VITA Inormation 3 Reerences 4 VRT Overview 5 Compliance 6 Data Packet Classes and Streams 7 Context Packet Classes and Streams 8 Inormation Classes and Streams
Appendix A Inormation Stream Speciication Example
Appendix B Context Field Examples The sections in this appendix contain examples that illustrate the use o several ields in the IF Context Packet Class. Each example contains a block diagram o the system begin described. The blocks in these diagrams that correspond to VRT packet stream generators contain symbols that are a visual shorthand or VRT packet stream generators. An example o this shorthand is shown in Figure B.1-1. Figure B.1-1: Example block diagram with VRT Packet Stream generator symbols shown The presence o a yellow (green) rectangle in the upper (lower) right hand corner o a process indicates that this process generates Context (Data) Packet Streams. In this example there are three processes that generate VRT packet streams. Process 1 does not generate any Data Packet Streams, it has an analog input and analog output. But it does generate an IF Context Packet Stream with a Stream Identiier that is represented by the characters S1. In the block diagram, this Context Packet Stream is represented by the yellow rectangle containing S1 in the upper right corner o the Process 1 block. Process 2 is composed o two sub-processes. Neither o these sub-processes generates VRT packet streams. However, the encapsulating Process 2 sends an IF Context Packet Stream that contains context about both subprocesses. As beore, this is represented by the yellow rectangle containing S2 in the upper right corner o the Process 2 block. This block also generates an IF Data Packet Stream. This is represented by the green rectangle containing S2 in the lower right corner o the Process 2 block. Note that both the yellow Context rectangle and the green Data rectangle have the same Stream Identiier, S2. This indicates that the Data and Context packet streams rom this process are directly associated as described in Section 7.1.2. Process 2 may also orward the Context packets it receives rom Process 1, or it may absorb this contextual inormation and present it in its own Context packet stream. Finally, Process 3 generates both IF Context and IF Data Packet Streams, indicated by the two rectangles containing S3. In the examples in the ollowing sections, the symbolic Stream Identiiers S1, S2, and S3 are replaced with actual 32-bit numbers. Sometimes it is not only useul to show which types o packet streams a process is generating, but to also show some o the details o the packet streams. In these cases, the block diagram is augmented with representations o the packet streams as shown in Figure B.1-2.
Figure B.1-2: Example block diagram with VRT Packet Stream details shown Details o the Context Packet Streams are shown in yellow boxes. Details o the Data Packet Streams are shown in green boxes. Here Context Packet Streams are represented with yellow boxes and Data Packet Streams are represented with green boxes. In this igure, the Stream Identiier or each o the packet streams is shown. Other ields will be shown as necessary.
Appendix B.1 Reerence Point Identiier Example Figure B.1-1 shows a block diagram o a VRT system that uses the Reerence Point Identiier ield. In this example there are three processes, a Digital Receiver, a DDC, and a Demodulator, each o which generates a Data Packet Stream and a Context Packet Stream. The Context Packet Streams coming rom the Tuner, DDC, and Demodulator, have Stream Identiiers 100, 200, and 300 respectively, and each orm a direct association with their respective Data Packet Streams. Figure B.1-1: Reerence Point Identiier Example The reerence point or the Digital Receiver and DDC Data is the Receiver input. The reerence point or the Demodulator is the Demodulator input. Each o the Context Packet Streams contains a Reerence Point ID ield that speciies the reerence point or each process. In this example, both the Receiver and DDC Context Packet Streams include a Reerence Point IDs equal to 100. This speciies that the reerence point or both the Receiver and DDC are at the input to the Digital Receiver. The Demodulator, however, has 300 as its Reerence Point ID, which speciies its own input as its reerence point. Thereore, the RF Reerence Frequency ield in the Digital Receiver s Context Packet Stream will indicate the requency at the input to the Digital Receiver that was translated to the IF Reerence Frequency. Also, the Reerence Level ield in the DDC s Context Packet Stream will indicate the power o a tone at the input to the Digital Receiver that will create a unit-scale sinusoid in the payload o the DDC s Data Packet. Similarly, the sum o the Timestamp in the Demodulator s Data Packet and the Timestamp Adjustment in the Demodulator s Context Packet Stream will indicate the time that the irst sample o the Data Packet was present at the input to the Demodulator.
Appendix B.2 Spectral Fields Example This section presents an example using the Bandwidth, IF Reerence Frequency, RF Reerence Frequency, and Spectral Inversion Indicator ields. This example also illustrates how context inormation can relate to analog signals. Subsequent examples will illustrate how these same ields relate to digital signals. The block diagram or this example contains only one process, an analog tuner, as shown in Figure B.2-1. The tuner translates spectral energy rom a high requency RF band to a lower requency IF band. Figure B.2-1: Block diagram or Spectral Fields example In this example the tuner generates an IF Context Packet Stream, with a Stream Identiier value o 100. The Context Packet contains the Reerence Point Identiier ield which also has value 100 to indicate that the reerence point is at the input to the tuner. The Context Packet also contains Bandwidth, IF Reerence Frequency, and RF Reerence Frequency ields. The Bandwidth Frequency Oset and RF Reerence Frequency Oset ields are not present in the Context Packet Stream (examples using these two ields are given in subsequent sections). Bandwidth Spectrum at Tuner input (Reerence Point) Bandwidth Spectrum at Tuner output IF Reerence Frequency RF Reerence Frequency Figure B.2-2: Original and Translated Spectra and Spectral Parameters The spectrum o the analog signals at the input and output o the Tuner. The Bandwidth ield gives the bandwidth o the output signal. The IF Reerence Frequency marks the center o the output band, and the RF Reerence Frequency marks the requency that was translated to the IF Reerence Frequency. Figure B.2-2 shows the RF spectrum at the tuner input (the reerence point) and the IF spectrum at the tuner output. In this example the Bandwidth ield contains the 3dB bandwidth at the tuner output. The IF center requency, which is the nominal center o the output band the tuner, is marked with a wide bar in the igure. The IF Reerence Frequency ield in the Context Packet speciies this value. The requency at the tuner input that translates to the IF Reerence Frequency would be speciied by the RF Reerence Frequency ield. Assuming the spectrum is not inverted rom the RF to the IF band, the Spectral Inversion Indicator bit in the State and Event Indicator ield would be zero.
I the tuner were tuned to 2 GHz and downconverted a 30 MHz band to a 70 MHz IF, without inverting its spectrum, then the spectral ields would contain the ollowing values: Figure B.2-3: Context Packet Stream contents or Spectral Fields Example
Appendix B.3 RF Reerence Frequency Oset Example The example in this section expands upon the example given in Appendix B.2, to illustrate how the RF Reerence Frequency Oset ield is used to eiciently convey requency translation inormation in channelized systems. This ield is typically used with channelizers, where a large number o narrowband signals are created rom portions o a wideband input signal. Figure B.3-1 shows such a system, where a Digital Receiver is ollowed by a bank o 64 DDCs. In this example, the digital receiver is dynamically tuned across a spectral region o interest. The DDCs are conigured to examine portions o the receiver s output band in greater detail. The tuning requency o each DDC channel remains ixed as the receiver s tuning requency is changed. Figure B.3-1: Block diagram or RF Reerence Frequency Oset Example The RF Reerence Frequency Oset ield is typically used with channelizers The Context Packet Stream or the Digital Receiver contains a Reerence Point ID that speciies the input to the receiver as the reerence point. The Receiver s Context Packet Stream also contains entries or IF Reerence Frequency and RF Reerence Frequency, as explained in Appendix B.2. The DDC Context Packet Streams each contain a Reerence Point ID and an Input Source Stream Association List. The Reerence Point ID speciies the input to each DDC as its reerence point. An entry in each o the Input Source Stream Association Lists contains Stream ID 100, which denotes that the receiver is the input source or each o the DDCs. The DDC Context Packet Streams also contains entries or IF Reerence Frequency and RF Reerence Frequency, and RF Reerence Frequency Oset.
Figure B.3-2: Original and Translated Spectra or a single DDC The red and green bars indicate which requencies get translated to the IF Reerence Frequency or the Digital Receiver, and DDC 2, respectively. Figure B.3-2 illustrates how the DDC s RF Reerence Frequency Oset ield is used. The original spectrum at the input to the digital receiver is shown in the top axis. The bands or several DDC channels are shown overlaid upon the RF spectrum. In addition, a red bar (letmost bar) is shown at the receiver s RF Reerence Frequency. This is the requency that gets converted to the receiver s IF Reerence Frequency. Also shown is a green bar (rightmost bar) at the requency that gets translated to the DDC s IF Reerence Frequency. The calculation to determine this original requency is discussed shortly. The middle axis shows the spectrum o the receiver s Data Packet Stream, which is also the input to each o the DDCs. The same channel bands and colored bars are shown with this translated spectrum. The bottom axis shows the spectrum o a single DDC s Data Packet Stream. The original requency marked by the green bar is translated to DC, and the spectrum or all other channels, including the one marked by the red bar, is iltered out. As stated in Section 7.1.5.5, the sum o the DDC s RF Reerence Frequency Oset and the some RF Reerence Frequency gets translated to the DDC s IF Reerence Frequency. Additionally, the RF Reerence Frequency or any associated upstream process can be used in this calculation. The RF Reerence Frequency or the DDC or the receiver can be used in this example. When the DDC s RF Reerence Frequency Oset is summed with the DDC s RF Reerence Frequency, this sum speciies a requency at the Reerence Point related to that RF Reerence Frequency. In this case, the reerence point
is the input to the DDC itsel. At this location, the ollowing relationship holds. Note that the let hand side o this relationship reers to the green bar in the middle axis. When the DDC s RF Reerence Frequency Oset is summed with the receiver s RF Reerence Frequency, the relationship holds at the receiver s reerence point, which is the input to the receiver. At this location, the ollowing relationship holds. In this case, the let hand side o this relationship reers to the green bar in the top axis. Consider this system when the receiver translates a 320 MHz band centered at 9 GHz down to an IF requency o 1 GHz and the bank o 64 DDCs breaks this band into 5 MHz-wide channels with a channel spacing that is also 5 MHz. I DDC 2 converted the band centered at 1005 MHz down to baseband, then the ollowing parameters would be sent in their respective Context Packet Streams. Figure B.3-3: Context Packet Stream contents or RF Reerence Frequency Oset Example Given these Context Packet Streams, a VRT processor could calculate that, o the spectrum at the DDC input, the band centered at 1005 MHz was translated to 0 Hz at the DDC output, and that, o the spectrum at the receiver input, the band centered at 9005 MHz was translated to 0 Hz at the DDC output. To see why the additional computation required by the RF Reerence Frequency Oset is useul, note that i the receiver sweeps its tuned requency to 9032 MHz, then 9064 MHz, and so on, that only one Context Packet or the receiver needs to be sent per requency step. The 64 Context Packets or the 64 DDCs do not need to be sent at each requency step. This could signiicantly reduce the chance o link congestion in some systems.
Appendix B.4 Bandwidth Frequency Oset Example The Bandwidth ield is used to describe the amount o usable signal spectrum at the output o a process. For many systems, the center o this signal band will be at the IF Reerence Frequency. For those systems where the IF Reerence Frequency is not at the center o the signal band, the Bandwidth Frequency Oset ield is used to speciy the dierence between the true center o the band and the IF Reerence Frequency. For example, or the digital receiver shown in Figure B.4-1, assume that it is necessary to have the IF Reerence Frequency describe the lower band edge. Figure B.4-1: Block diagram or Bandwidth Frequency Oset Example Figure B.4-2 shows the signal spectrum at the input and output o the receiver. The IF Reerence Frequency is at the lower band edge, and the Bandwidth Frequency Oset speciies the amount to add to the IF Reerence Frequency value to get the true center o the band described by the Bandwidth ield. Bandwidth Spectrum at Receiver input (Reerence Point) Bandwidth Spectrum at Receiver output IF Reerence Frequency Bandwidth Frequency Oset RF Reerence Frequency Figure B.4-2: Original and Translated Spectra or Bandwidth Frequency Oset Example The IF Reerence Frequency marks the lower band edge. The sum o the IF Reerence Frequency and Bandwidth Frequency Oset gives the band center requency.
The ollowing numerical example is the same as that given in Appendix B.2, but with the IF Reerence Frequency at the lower band edge instead o the band center. I the tuner were tuned to 2 GHz and downconverted a 30 MHz band to a 70 MHz IF, without inverting its spectrum, then the spectral ields would contain the ollowing values: Figure B.4-3: Context Packet Stream contents or Bandwidth Frequency Oset Example
Appendix B.5 Frequency Translation Example In many applications, equipment rom dierent vendors will connected together to perorm a particular task. For some systems, the context rom each individual component may not be useul, but the combined settings o the entire system are o interest to the end user. Thereore the system designer may choose to aggregate the context rom each component and generate a summary context packet stream or the entire system, to be sent along with the system s inal data packet stream. Aggregating context rom a cascade o components is generally a straight-orward procedure. For the system delay parameter, the sum o the individual Timestamp Adjustment ields will usually suice. For the system level parameter, the gain o each component can be added to the Reerence Level o the digitizer. The system bandwidth will typically be the bandwidth o the inal bandlimiting process. The determination o the original RF requency, however, is complicated when the input and output center requencies o neighboring process are mismatched, or spectral inversion is encountered. Consider the VRT-enabled components shown in Figure B.5-1 which were combined to orm a surveillance system. The tuner downconverts a 500 MHz band rom a center requency o 10 GHz to an IF center requency o 1200 MHz. The UHF tuner converts a 30 MHz portion o this band centered at 1400 MHz down to an IF center requency o 20 MHz. There the signal is digitized and a DDC is used to downconvert a 1 MHz band rom a center requency o 30 MHz to baseband. Figure B.5-1: Surveillance System Components or Frequency Translation Example VRT Context Packet Streams are generated by each o these components (or their controllers) and VRT Data Packet Streams are generated by the ADC and DDC. The end user o the system, however, would like to be presented with only the DDC data packet stream and a context packet stream that describes the settings o the combined system, as shown in Figure B.5-2. In other words, the end user would like the data and context or only the DDC process, but with the reerence point or the DDC context moved up to the antenna.
Figure B.5-2: Surveillance System As shown in Figure B.5-2, several context parameters or the aggregate surveillance system are easy to determine. The Bandwidth, IF Reerence Frequency, and Sample Rate ields or the system are the same as those or the inal DDC process. There are two spectral inversions (in the and UHF tuners) between the original DDC input reerence point and the desired antenna reerence point. Thereore the spectral inversion indicator or the system is the same as that or the DDC. The inal parameter to determine is the RF Reerence Frequency, which requires calculation. This calculation is made simpler by irst determining the translation requency or each process in the signal path. The translation requency is the dierence between the requency o the original RF signal and the requency o the upright spectral image ater requency conversion. In terms o VRT parameters, shown in Figure B.5-3, the translation requency is the dierence between the RF Reerence Frequency and the IF Reerence Frequency i no spectral inversion occurs, and the dierence between the RF Reerence Frequency and the negative IF Reerence Frequency i spectral inversion does occur during the requency conversion.
Figure B.5-3: VRT Parameters and Frequency Conversion The translation requency is shown graphically or the spectrally inverting and non-inverting cases in Figure B.5-4. Figure B.5-4: The translation requency or spectral inversion and non-inversion The translation requency is the dierence between the original spectra at the reerence point and the upright spectra ater requency conversion. For the non- inverting downconversion shown on the let, the translation requency is simply the dierence between the RF and IF Reerence Frequencies. For the inverting downconversion, it is the dierence between the RF Reerence Frequency and the negative IF Reerence Frequency. The equation relating these VRT ields is RF Re + Δ = I (1) IF Re where Δ is the translation requency and I is related to the Spectral Inversion Indicator. I is +1 or non-inverting translations, and -1 or inverting translations. Once the translation requencies or each process is known, it is straight-orward to determine the relationship between the IF Reerence Frequency and the RF Reerence Frequency or any reerence point in the signal path. For the example shown in Figure B.5-1, the translation requencies are:
Δ Δ Δ Δ UHF ADC DDC = I = I = 0Hz = I UHF DDC IF Re UHF IF Re DDC IF Re SDR Forum Document Number SDRF-07-I-0007-V0.0.0 RF Re UHF RF Re DDC RF Re = ( 1) ( 1) = = 1200MHz 10GHz = 11,200MHz 20MHz 1400MHz = 1,420MHz ( + 1) 0MHz 30MHz = 30MHz Figure B.5-1 has ive triangle symbols at the inputs and outputs o the system components. The relationships between these ive points can be expressed using equation (1) as: B C D E = I = I = I = I DDC ADC UHF A B C D Δ Δ Δ Δ DDC ADC UHF Using substitution, the requency relationship between points A and E is: E E = I = I ( I ( I ( I Δ ) Δ ) Δ ) I UHF UHF I ADC ADC I DDC DDC A A I I DDC UHF I ADC Δ ADC DDC I UHF I Δ UHF Δ ADC I Δ UHF Δ Points A and E are the IF and RF Reerence Frequency points or the aggregate system. Thereore the RF Reerence Frequency or the system is calculated as: System RF Re System RF Re System RF Re = I I UHF I DDC System IF Re I Δ = 0Hz + 30MHz 1,420MHz + 11,200MHz = 9,810MHz I UHF DDC I Δ UHF Δ The translation requency or the entire system can be ound as: System RF Re I Δ System System = I = I = I System I I UHF UHF System IF Re I DDC Δ DDC Δ = + 1 + I System Δ UHF = I + Δ I UHF I DDC System IF Re = 9810MHz I I UHF Δ DDC I Δ UHF Δ The requency translations and spectral inversions are also be shown graphically in Figure B.5-5.
Tuner Input UHF Tuner Input Inversion (I ) UHF ADC Input DDC Input Inversion (I UHF ) DDC DDC Output Figure B.5-5: Frequency Translations within System The requency translation or the entire system simpliies to that shown in Figure B.5-6. Figure B.5-6: Frequency Translation or cascaded System The RF and IF Reerence Frequencies within the system are shown in Figure B.5-7
Figure B.5-7: RF and IF Reerence Frequencies within System
Appendix B.6 Reerence Level and Gain Example This section contains an example illustrating the use o the Reerence Level and Gain ields. Figure B.6-1 shows an example system with a microwave tuner, a digital receiver, and a DDC. Microwave Tuner Context Packet Stream Digital Receiver Context Packet Stream DDC Context Packet Stream Stream ID: 100 Stream ID: 200 Stream ID: 300 Re Point ID: 100 Re Point ID: 200 Re Point ID: 300 Gain = 15 db Reerence Level = -30 dbm Gain = -6 db 100 200 300 Analog Mircowave Tuner Analog Digital Receiver VRT DDC VRT 100 200 300 Digital Receiver Data Packet Stream Stream ID: 200 Digital Receiver Data, Fixed Point 12-bit 2's complement DDC Data Packet Stream Stream ID: 300 DDC Data Complex, Fixed-Point I&Q each 16-bit 2's complement Figure B.6-1: Block diagram or Gain and Reerence Level Example The microwave tuner has an analog input and an analog output, and the gain between the input and output is 15 db. The digital receiver has an analog input, and generates IF Data Packets with 12-bit two s-complement real samples. A -30 dbm tone at the input to the digital receiver will cause the signal within the IF Data Packet Stream to range rom positive to negative ull scale. Thereore a -45 dbm signal at the input to the microwave tuner will also generate a ull-scale signal at the digital receiver output. Figure B.6-2 shows the ull-scale output o the Digital Receiver Need rules regarding behavior o Gain ield or digital processes? (See next page)
Two's Complement Fractional dbfs Digital Receiver Output + Full Scale +2 11 +½ 0 0 0 t - Full Scale -2 11 -½ Figure B.6-2: Level o Digital Receiver samples When stimulated with a -30 dbm tone at its input, the Digital Receiver will generate a sample stream where the signal ranges the ull 12-bit scale. The DDC processes the 12-bit real samples rom the receiver and generates complex samples, where both the real and imaginary components use a 16-bit two s-complement ormat. The DDC has a gain o -6 db because a tone that is ull-scale at its input will cause it to generate a packet stream with complex samples where both the real and imaginary components have peak amplitudes 6 db below ull-scale (-6 dbfs). Figure B.6-3 shows the -6 dbfs output o the DDC. Two'sCompleme nt Fractional dbfs DDC Output, + Full Scale +2 15 +½ 0 +2 14 +¼ -6 0 0 t -2 14 +¼ - Full Scale -2 15 -½ Two's Complement Fractional Number dbfs DDC Output, Imaginary + Full Scale +2 15 +½ 0 +2 14 +¼ -6 0 0 t -2 14 +¼ - Full Scale -2 15 -½ Figure B.6-3: Level o DDC samples When stimulated with a ull-scale tone at its input, such as that in Figure B.6-2, the DDC will generate a complex sample stream where the real and imaginary components range one-hal o ull-scale, or 6 db below ull-scale.
Appendix B.7 Timestamp Adjustment Example The example in this section illustrates the use o the Timestamp Adjustment ield to make corrections to the value contained in the Timestamp ield, and to enable the correlation o events at dierent reerence points in the system. Figure B.7-1 shows a system with an antenna ollowed by a digital receiver and a DDC processor. In this system, the group delay rom the input o the antenna to the digital receiver input is 10 ns, the group delay rom the input o the digital receiver to the its digitizer is 5 ns, and the group delay through the DDC ilter is 1 μs. 1 Figure B.7-1: Block diagram or Timestamp Adjustment Example Note that in the above igure, each process speciies its own input as its reerence point or the Timestamp Adjustment. Consider this system where the end user is interested in determining the timing o eatures o a signal in the DDC data packet at the input to the antenna. In this system, each process may take the Timestamp Adjustment o the process that precedes it and use this value to determine a new value o Timestamp Adjustment or the antenna input reerence point. For example, the Digital Receiver adds its internal 5 ns o delay to the -10 ns Timestamp Adjustment o the Antenna process and generates an IF Context Packet with a Timestamp Adjustment o -15ns and a Reerence Point ID that is the Stream ID o the Antenna, 100. Likewise, the DDC generates an IF Context Packet with a Timestamp Adjustment o -1015 ns and a Reerence Point ID o 100. Another option or this system is or the Timestamp in the IF Data Packets to be adjusted to account or the group delay in each process. Figure B.7-2 shows several o these options or the DDC process. 1 Note that though group delay varies with requency, the Timestamp Adjustment ield can only convey a single delay value. It is thereore most useul in those applications where the group delay can be considered constant over a particular band o interest.
Figure B.7-2 : Timing diagram or Timestamp Adjustment Example The signal at the top o this igure shows the signal as it was at the input o the antenna. An impulse is shown near the beginning o this signal trace. The second signal shows the sample stream at the output o the digital receiver, which is delayed 15 ns rom the input o the antenna. The Data and Context Packet Streams or the digital receiver are shown below the digital receiver sample stream. The data packets shown contain the samples displayed directly above them. The irst sample o the receiver data packet corresponds to the time the impulse was digitized, T 0, which is 15 ns ater the impulse arrived at the antenna input. Thereore the timestamp o the irst packet is T 0, and the Timestamp adjustment sent in the receiver s Context Packet is -15 ns. The DDC process ilters and decimates the signal. The Timestamp and Timestamp Adjustment ields or the DDC can be arranged in several ways. First, the DDC data packets can be timed to account or the group delay o the DDC, as shown in the irst row. Here the impulse becomes the irst sample o the DDC packet, and the Timestamp plus Adjustment is T 0 15 ns. The second and third rows show options where the DDC packets are not retimed. In these cases, the impulse occurs 1 μs later in the data packet than it did in the irst case. Thereore the Timestamp plus Timestamp Adjustment is T 0-1015 ns.
Appendix B.8 Data Packet Payload Format Examples This section presents several examples o the Data Packet Payload Format ield and shows the corresponding packing o the Data Packet payload. There are a very large number o permutations o payload ormats. The aim o this section is to show the use o each subield within the Data Packet Payload Format rather than show every permutation o subields. The igures in the remainder o this section have two parts. The (a) part at the top o each igure contains valid values o the Data Packet Payload Format ield or a variety o Data Item Formats. The (b) part at the bottom o each igure shows a the irst ew packing ields in the resulting Data Packet Payload. Figure B.8-2 through Figure B.8-7 show the payload packing or the common 32, 16 and 8-bit data item sizes, or both real and complex ormats. In these irst ew examples, note that there are several permutations o the Complex Polar ormat. They are summarized in Table B.8-1. Data Sample Type Data Item Type Format o the Amplitude Component Format o the Phase Component Any unsigned ixed-point ormat Unsigned ixed-point Signed ixed-point or normalized phase as per Rule 6.1.5.4-12 Complex Polar, Signed Phase Any signed ixed-point ormat Signed ixed-point (but always positive) Signed ixed-point or normalized phase as per Rule 6.1.5.4-12 Any loating-point ormat Floating-point (but always positive) Floating-point value in radians in the range [-π, π) Any unsigned ixed-point ormat Unsigned ixed-point Unsigned ixed-point or normalized phase as per Rule 6.1.5.4-13 Complex Polar, Unsigned Phase Any signed ixed-point ormat Signed ixed-point (but always positive) Unsigned ixed-point or normalized phase as per Rule 6.1.5.4-13 Any loating-point ormat Floating-point (but always positive) Floating-point value in radians in the range [0, 2π) Table B.8-1: Complex Polar Component Formats Figure B.8-1 shows the organization o the Data Packet Payload Field, which is a useul reerence when analyzing the ormat codes given in this section. Word 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Item Packing Data Item Event- Channel- Vector 1 Reserved Field Size Size Tag Size Tag Size Size 2 Pack Repeat Count Rpt Reserved Figure B.8-1: Data Packet Payload Format Field / Cmplx Data Item Format
Data Packet Payload Format 3EF80000 00000000 3EF80000 00000010 3EF80000 0000001E /Complex (a) Format Unsigned Fixed Pt. Signed Fixed Pt. Double-Precison Floating Pt. 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Data Item 1 (Sample 1) Data Item 2 (Sample 2) Data Item 3 (Sample 3) Data Item 4 (Sample 4) (b) Figure B.8-2: 32-bit Format Data Packet Payload Format 3EF80000 00000030 3EF80000 00000060 3EF80000 00000040 3EF80000 0000007E 3EF80000 0000005E /Complex Complex Cartesian Complex Polar Complex Polar Complex Polar Complex Polar Cartesian Format Signed Fixed Pt. n/a n/a n/a n/a (a) Polar Amplitude Format n/a Unsigned Fixed Pt. Unsigned Fixed Pt. Double-Precision Floating Pt. Double-Precision Floating Pt. Polar Phase Format n/a Unsigned Fixed Pt. Signed Fixed Pt. Double-Precision Floating Pt. (Unsigned) Double-Precision Floating Pt. (Signed) 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Data Item 1 (Sample 1 /Ampl) Data Item 2 (Sample 1 Imag/Phase) Data Item 3 (Sample 2 /Ampl) Data Item 4 (Sample 2 Imag/Phase) (b) Figure B.8-3: 32-bit Complex Format
Data Packet Payload Format 1E780000 00000000 1E780000 00000010 1E780000 0000001D /Complex (a) Format Unsigned Fixed Pt. Signed Fixed Pt. Single-Precison Floating Pt. 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Data Item 1 (Sample 1) Data Item 2 (Sample 2) Data Item 3 (Sample 3) Data Item 4 (Sample 4) Data Item 5 (Sample 5) Data Item 6 (Sample 6) Data Item 7 (Sample 7) Data Item 8 (Sample 8) (b) Figure B.8-4: 16-bit Format Data Packet Payload Format 1E780000 00000030 1E780000 00000060 1E780000 00000040 1E780000 0000007D 1E780000 0000005D /Complex Complex Cartesian Complex Polar Complex Polar Complex Polar Complex Polar Cartesian Format Signed Fixed Pt. n/a Polar Amplitude Format n/a Unsigned Fixed Pt. Polar Phase Format n/a Unsigned Fixed Pt. n/a Unsigned Fixed Pt. Signed Fixed Pt. n/a Single-Precision Single-Precision Floating Pt. Floating Pt. (Unsigned) n/a Single-Precision Single-Precision Floating Pt. Floating Pt. (Signed) (a) 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Data Item 1 (Sample 1 /Ampl) Data Item 2 (Sample 1 Imag/Phase) Data Item 3 (Sample 2 /Ampl) Data Item 4 (Sample 2 Imag/Phase) Data Item 5 (Sample 3 /Ampl) Data Item 6 (Sample 3 Imag/Phase) Data Item 7 (Sample 4 /Ampl) Data Item 8 (Sample 4 Imag/Phase) (b) Figure B.8-5: 16-bit Complex Format
Data Packet Payload Format 0E380000 00000000 0E380000 00000010 /Complex (a) Format Unsigned Fixed Pt. Signed Fixed Pt. 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Data Item 1 (Sample 1) Data Item 2 (Sample 2) Data Item 3 (Sample 3) Data Item 4 (Sample 4) Data Item 5 (Sample 5) Data Item 9 (Sample 9) Data Item 13 (Sample 13) Data Item 6 (Sample 6) Data Item 10 (Sample 10) Data Item 14 (Sample 14) (b) Data Item 7 (Sample 7) Data Item 11 (Sample 11) Data Item 15 (Sample 15) Figure B.8-6: 8-bit Format Data Item 8 (Sample 8) Data Item 12 (Sample 12) Data Item 16 (Sample 16) Data Packet Payload Format 0E380000 00000030 0E380000 00000060 0E380000 00000040 /Complex Complex Cartesian Complex Polar Complex Polar Cartesian Format Polar Amplitude Format Polar Phase Format Signed Fixed Pt. n/a n/a n/a Unsigned Fixed Pt. Unsigned Fixed Pt. n/a Unsigned Fixed Pt. Signed Fixed Pt. (a) 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Data Item 1 (Sample 1 /Ampl) Data Item 2 (Sample 1 Imag/Phase) Data Item 3 (Sample 2 /Ampl) Data Item 4 (Sample 2 Imag/Phase) Data Item 5 (Sample 3 /Ampl) Data Item 9 (Sample 5 /Ampl) Data Item 13 (Sample 7 /Ampl) Data Item 6 (Sample 3 Imag/Phase) Data Item 10 (Sample 5 Imag/Phase) Data Item14 (Sample 7 Imag/Phase) (b) Data Item 7 (Sample 4 /Ampl) Data Item 11 (Sample 6 /Ampl) Data Item 15 (Sample 8 /Ampl) Figure B.8-7: 8-bit Complex Format Data Item 8 (Sample 4 Imag/Phase) Data Item 12 (Sample 6 Imag/Phase) Data Item 16 (Sample 8 Imag/Phase)
The next three examples illustrate several methods o link-eicient and processing-eicient payload packing. Figure B.8-8 shows 14-bit real data with link-eicient packing, Figure B.8-9 shows 14-bit data with processingeicient packing, and Figure B.8-10 shows 14-bit data placed in 16-bit packing ields. This last example would have the same payload packing regardless o whether link- or processing-eicient packing was speciied. Note that all packing ields are let-justiied, so unused bits appear at the lsbs o the 32-bit word or the lsbs o the packing ield. Data Packet Payload Format 9A680000 00000000 9A680000 00000010 /Complex (a) Format Unsigned Fixed Pt. Signed Fixed Pt. 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Data Item 1 (Sample 1) Data Item 2 (Sample 2) Data Item 3 (Sample 3) Data Item 4 (Sample 4) Data Item 5 (Sample 5) Data Item 6 (Sample 6) Data Item 7 (Sample 7) Data Item 8 (Sample 8) Data Item 9 (Sample 9) (b) Figure B.8-8: Link-Eicient Packing Data Packet Payload Format 1A680000 00000000 1A680000 00000010 /Complex (a) Format Unsigned Fixed Pt. Signed Fixed Pt. 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Data Item 1 (Sample 1) Data Item 2 (Sample 2) U U U U Data Item 3 (Sample 3) Data Item 4 (Sample 4) U U U U Data Item 5 (Sample 5) Data Item 6 (Sample 6) U U U U Data Item 7 (Sample 7) Data Item 8 (Sample 8) U U U U (b) Figure B.8-9: Processing-Eicient Packing
Data Packet Payload Format 1E680000 00000000 1E680000 00000010 /Complex (a) Format Unsigned Fixed Pt. Signed Fixed Pt. 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Data Item 1 (Sample 1) U U Data Item 2 (Sample 2) U U Data Item 3 (Sample 3) U U Data Item 4 (Sample 4) U U Data Item 5 (Sample 5) U U Data Item 6 (Sample 6) U U Data Item 7 (Sample 7) U U Data Item 8 (Sample 8) U U (b) Figure B.8-10: 14-bit Data Items in 16-bit Packing Fields Figure B.8-11 illustrates the use o event tags. In this example, 8-bit data is packed into 10-bit packing ields. The two remaining bits are declared as event tags, denoted with E. This example also illustrates processing-eicient packing or 10-bit packing ields, where 3 packing ields can it in a single 32-bit word. Data Packet Payload Format 123A0000 00000000 123A0000 00000010 /Complex (a) Format Unsigned Fixed Pt. Signed Fixed Pt. 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Data Item 1 (Sample 1) Data Item 4 (Sample 4) Data Item 7 (Sample 7) Data Item 10 (Sample 10) Data Item 2 Data Item 3 E E E E E E U U (Sample 2) (Sample 3) Data Item 5 Data Item 6 E E E E E E U U (Sample 5) (Sample 6) Data Item 8 Data Item 9 E E E E E E U U (Sample 8) (Sample 9) E E Data Item 11 Data Item 12 E E (Sample 11) (Sample 12) E E U U (b) Figure B.8-11: Event Tags
Figure B.8-12 demonstrates the use o sample vectors. In this example, 8-bit data is simultaneously collected rom our sources. The irst samples rom each source are grouped at the beginning o the payload, ollowed by the group o second samples, and so on. This orms a 4-dimensional sample vector. Data Packet Payload Format 0E380003 00000000 0E380003 00000010 /Complex (a) Format Unsigned Fixed Pt. Signed Fixed Pt. 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Data Item 1 (Sample 1, Component 1) Data Item 2 (Sample 1, Component 2) Data Item 3 (Sample 1, Component 3) Data Item 4 (Sample 1, Component 4) Data Item 5 (Sample 2, Component 1) Data Item 9 (Sample 3, Component 1) Data Item 13 (Sample 4, Component 1) Data Item 6 (Sample 2, Component 2) Data Item 10 (Sample 3, Component 2) Data Item 14 (Sample 4, Component 2) (b) Data Item 7 (Sample 2, Component 3) Data Item 11 (Sample 3, Component 3) Data Item 15 (Sample 4, Component 3) Figure B.8-12: Sample Vector Data Item 8 (Sample 2, Component 4) Data Item 12 (Sample 3, Component 4) Data Item 16 (Sample 4, Component 4) Figure B.8-13 shows the use o channel tags with a 4-dimensional sample vector. This example is the same as the sample vector in example shown in Figure B.8-12, but each 8-bit sample is placed in a 10-bit packing ield, with the remaining two bits used as channel tags. In this example the channel tags are used to identiy each vector component. Data Packet Payload Format 12382003 00000000 12382003 00000010 /Complex (a) Format Unsigned Fixed Pt. Signed Fixed Pt. 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Data Item 1 Data Item 2 Data Item 3 0 0 0 1 (Sample 1, Component 1) (Sample 1, Component 2) (Sample 1, Component 3) 1 0 U U Data Item 4 Data Item 5 Data Item 6 1 1 0 0 (Sample 1, Component 4) (Sample 2, Component 1) (Sample 2, Component 2) 0 1 U U Data Item 7 Data Item 8 Data Item 9 1 0 1 1 (Sample 2, Component 3) (Sample 2, Component 4) (Sample 3, Component 1) 0 0 U U Data Item 10 Data Item 11 Data Item 12 0 1 1 0 (Sample 3, Component 2) (Sample 3, Component 3) (Sample 3, Component 4) 1 1 U U (b) Figure B.8-13: Sample Vector with Channel Tags
Figure B.8-14 demonstrates Channel Repeating with a 4-deimensional sample vector, where several consecutive samples rom the one source are grouped and packed in the payload beore the same samples rom the next source are grouped and packet in the payload. In this example, 4 consecutive samples rom each source are repeated. Data Packet Payload Format 0E380003 00030000 0E380003 00030010 /Complex (a) Format Unsigned Fixed Pt. Signed Fixed Pt. 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Data Item 1 (Sample 1, Component 1) Data Item 5 (Sample 1, Component 2) Data Item 9 (Sample 1, Component 3) Data Item 13 (Sample 1, Component 4) Data Item 17 (Sample 5, Component 1) Data Item 21 (Sample 5, Component 2) Data Item 2 (Sample 2, Component 1) Data Item 6 (Sample 2, Component 2) Data Item 10 (Sample 2, Component 3) Data Item 14 (Sample 2, Component 4) Data Item 18 (Sample 6, Component 1) Data Item 22 (Sample 6, Component 2) (b) Data Item 3 (Sample 3, Component 1) Data Item 7 (Sample 3, Component 2) Data Item 11 (Sample 3, Component 3) Data Item 15 (Sample 3, Component 4) Data Item 19 (Sample 7, Component 1) Data Item 23 (Sample 7, Component 2) Figure B.8-14: Channel Repeating Data Item 4 (Sample 4, Component 1) Data Item 8 (Sample 4, Component 2) Data Item 12 (Sample 4, Component 3) Data Item 16 (Sample 4, Component 4) Data Item 20 (Sample 8, Component 1) Data Item 24 (Sample 8, Component 2) Figure B.8-15 shows Sample Component Repeating or complex data ormats, where the real or amplitude component is or several consecutive samples is packed in the payload beore the imaginary or phase component is packed or the same samples. This example demonstrates a sample component repeat count o our. Data Packet Cartesian Polar Amplitude /Complex Payload Format Format Format Polar Phase Format 0E380003 Complex 00038020 Cartesian Signed Fixed Pt. n/a n/a 0E380003 Complex 00038060 Polar n/a Unsigned Fixed Pt. Unsigned Fixed Pt. 0E380003 Complex 00038040 Polar n/a Unsigned Fixed Pt. Signed Fixed Pt. (a) 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Data Item 1 (Sample 1 /Ampl) Data Item 2 (Sample 2 /Ampl) Data Item 3 (Sample 3 /Ampl) Data Item 4 (Sample 4 /Ampl) Data Item 5 (Sample 1 Imag/Phase) Data Item 9 (Sample 5 /Ampl) Data Item 13 (Sample 5 Imag/Phase) Data Item 6 (Sample 2 Imag/Phase) Data Item 10 (Sample 6 /Ampl) Data Item 14 (Sample 6 Imag/Phase) (b) Data Item 7 (Sample 3 Imag/Phase) Data Item 11 (Sample 7 /Ampl) Data Item 15 (Sample 7 Imag/Phase) Data Item 8 (Sample 4 Imag/Phase) Data Item 12 (Sample 8 /Ampl) Data Item 16 (Sample 8 Imag/Phase) Figure B.8-15: Sample Component Repeating or Complex Data Formats
Appendix B.9 ECEF and Relative Ephemeris Example This section presents an example where the Relative Ephemeris rom one IF Context Packet is combined with the ECEF Ephemeris rom another IF Context Packet. For simplicity, this example is limited to two dimensions. Consider the aircrat platorm shown in Figure B.9-1. The location o an antenna on the wing o this aircrat is known in the Relative Ephemeris Coordinate System (RCS). The origin o the RCS is chosen to be at the location o a GPS antenna near the rear o the aircrat. The x axis is directed along the heading o the aircrat. The y axis is at a right angle to the x axis in the plane o the aircrat. The antenna in question is located at the point P =(x 1, y 1 ) in the RCS. The antenna itsel is directed at an angle α rom the x axis. Figure B.9-1: Location and attitude o antenna in the Relative Ephemeris Coordinate System The antenna is at coordinates (x 1, y 1 ) with respect to the aircrat GPS. The GPS antenna is a convenient location or the RCS origin because the location o the GPS antenna can be determined in the ECEF Coordinate System (ECS). Consider the arrangement shown in Figure B.9-2 where the origin o the ECS is at the center o the earth. Because this is a two-dimensional example, aircrat is in the plane o the earth s equator. The GPS is located at the point P 0 =(x 0, y 0 ) in the ECS and the aircrat heading is at an angle o θ with respect to the prime meridian. With this inormation, the location o the antenna on the aircrat wing can be calculated with the proper transormation equation.
Figure B.9-2: Location and attitude o antenna in the ECEF Coordinate System The GPS o the aircrat is at (x 0, y 0 ) and the aircrat has a heading o θ. This aircrat platorm carries the VRT system shown in Figure B.9-3. Here the coordinates o the antenna in the RCS are given in the IF Context Packet o the antenna. The coordinates or the GPS and heading o the aircrat in the ECS are given in the IF Context Packet or the GPS. To link the two coordinate systems together, the Antenna IF Context Packet Stream also contains the Ephemeris Reerence ID ield that contains the Stream ID o the GPS. The transormation between the RCS and ECS must also be provided in the Inormation Class documentation. For this two-dimensional example, the transormation equations could be expressed as: ( ) ( ) ( ) = = 1 1 0 0 1 0 0 1 1 0 0 0 cos sin 0 sin cos 1 0 0 1 0 0 1 1 0 0 0 0 0 0 y x y x y x y x P P T R P T P θ θ θ θ θ and α θ α + =
which rotates the point P =(x, y ) an angle o θ about the point P 0 =(x 0, y 0 ), where P and P are the location o the antenna in question in the RCS and ECS, respectively, P 0 is the location o the GPS in the ECS, and α is the heading o the aircrat in the ECS. T() is a translation matrix, and R() is a rotation matrix. Figure B.9-3: Block diagram or ECEF and Relative Ephemeris Example The Ephemeris Reerence ID ield o the Antenna contains a value o 901, the Stream ID o the GPS.
Appendix B.10 Input Source Stream Association List Example The example in this section illustrates the use o the Input Source Stream Association List, also reerred to as the Input Source List. Figure B.10-1 shows a system with three cascaded VRT processes: a digital receiver, a DDC, and a demodulator. The receiver is the source or the data the DDC uses as an input, and the DDC is the input source or the demodulator. Figure B.10-1: Block diagram or Input Source List Example Clearly the settings o the receiver, DDC, and demodulator would aect the interpretation o the data at the output o the demodulator. Thereore, one Inormation Stream or this system would contain the demodulator s Data Packet Stream and the Context Packet Streams o the upstream processes. Figure B.10-2 shows the content o the Data and Context Packets in this Inormation Stream. The Stream ID or the demodulator Context Packet Stream, 300, matches the Stream ID or the demodulator Data Packet Stream. Thereore the demodulator Context Packet Stream is directly associated to the demodulator Data Packet. The demodulator Context Packet Stream also contains an entry o 200 in its Input Source List, shown in blue, which is the Stream ID o the DDC Context Packet Stream. In this way, the Context Packet Stream o the DDC is associated to the Data Packet Stream o demodulator. Association through the Stream Association Lists is known as contextual association. Because contextual association is indirect, is not as strong as direct association. The Context Packet Stream or the receiver is also attached to the demodulator s Data Packet Stream through the Input Source List in the DDC. The entire chain o Data Packet Stream and associated Context Packet Streams comprises the Inormation Stream. Figure B.10-2: Representation o Input Source Stream Associations