1 UAT Test Procedure and Report

Transcription

1 1 UAT Test Procedure and Report These tests are performed to ensure that the UAT Transmitter will comply with the equipment performance tests during and subsequent to all normal standard operating conditions of, as defined by UAT_A3_TX_Prototype_SOW: Rev- B_6. The associated data sheets will include limits that comply with specific requirements identified in RTCA DO- 282A. Apparatus Break out the AC power leads. Connect the test equipment as illustrated in Figure 1 VNA HP89441A PS PS +28v -12v 20dB 30dB USB Port UAT Transmitter 20dB Coupler 1 watt 50 ohm Termination 30dB 30dB Figure Test Setup for Transmitter Test 1.1 Design Assurance (DO-282A section ) The UAT Transmitter design is RTCA/DO-178B compliant 1.2 Antenna Diversity (DO-282A section Table 2-1) Requirements 1. Transmitter shall have full diversity alternating between top/bottom antenna ports 2. The unselected antenna port shall be greater than 20dB below the level of the selected antenna port. 3. Antenna switching shall occur during the non active state Conditions Reference DO-282A section step 5 for test setup and procedure

2 1.2.3 Measurement Data 1. Measure the output to the selected antenna. 2. Measure the output to the non selected antenna and verify that the power is 20dB below the selected antenna. 3. Select the other antenna and repeat steps 1 and 2. The measured attenuation to the HP89441A was 68.0dB. Antenna Power- Selected(dBm) Power-Not Selected(dBm) Difference Top Bottom HP89441A Pictures Figure Top Antenna with Top antenna Selected

3 Figure Top Antenna with Bottom Antenna Selected Figure Bottom Antenna with the Bottom Antenna Selected

4 Figure Bottom Antenna with the Top Antenna Selected 1.3 Transmitter Power (DO-282A section ) Requirements 1. Minimum power at the antenna shall be 100 w (+50 dbm) 2. Maximum power at the antenna shall be 250 w (+54 dbm) 3. Power shall remain between the minimum and maximum limits for the duration of the pulse Conditions Reference DO-282A section for test setup and procedure Measurements 1. Measure the power throughout the pulse at the output to the top antenna. Record the minimum and maximum values. 2. Measure the power throughout the pulse at the output to the bottom antenna. Record the minimum and maximum values.

5 1.3.4 Data The measured attenuation to the HP89441A was 68.0dB. Antenna Power-Rising Edge(dBm) Power-Falling Edge(dBm) Difference Top Bottom Note: The pulses max power is at the rising edge and the min power is at the falling edge HP89441A Pictures Figure Top Antenna Rising Edge

6 Figure Top Antenna Falling Edge Figure Bottom Antenna Rising Edge

7 Figure Bottom Antenna Falling Edge 1.4 Transmission Frequency (DO-282A section ) Requirements Transmission frequency shall be 978 MHz +/- 20 ppm (+/ KHz) Conditions Configure the vector analyzer a specified in DO-282A section Measurements 1. Measure and record the transmission frequency offset Data The carrier offset measured 169.7Hz.

8 1.4.5 HP89441A Pictures Figure Carrier Offset 1.5 Modulation Rate (DO-282A section ) Requirements The nominal modulation rate shall be megabits per second Conditions Test setup as specified in DO-282A section Measurements 1. Measure the modulation rate as specified on the vector analyzer Data The modulation rate measured 78.0%.

9 1.5.5 HP89441A Pictures Figure Modulation Rate 1.6 Modulation Type (DO-282A section ) Requirements Data shall be modulated onto the carrier using binary Continuous Phase Frequency Shift Keying. The modulation index shall be 0.6. A binary 1 shall be a shift up in frequency by KHz and binary 0 shall be a shift down in frequency by KHz Conditions Reference DO-282A section for test setup and test procedures Measurements 1. Measure the modulation type as specified on the vector analyzer Data + Offset(kHz) - Offset(kHz)

10 1.6.5 HP89441A Pictures Figure Offset Figure Offset

11 1.7 Modulation Distortion (DO-282A section ) Requirements The minimum opening of the eye diagram of the transmitted signal shall not be less than 560 KHz when measured over an entire Long ADS_B Message containing pseudorandom payload data Conditions Reference DO-282A section for test setup and test procedures Measurements 1. Measure the Modulation Distortion as specified on the vector analyzer Data The vertical opening of the eye was 586.6kHz HP89441A Pictures Figure Modulation Distortion

12 1.8 Transmitter Power Output (DO-282A section Requirements The Time/Amplitude profile of an ADS-B Message Transmission shall fall within the following limits relative to a reference to a reference time defined as 0.48 microseconds prior to the center of the first bit of the synchronization sequence appearing at the output port of the equipment. All power measurements for subparagraphs a through f below apply to the selected antenna port. The RF power output on the non-selected antenna port shall be at least 20 db below the level on the selected port. a. Prior to 8 bit periods before the reference time, the average RF output power shall not exceed -80 dbm. b. Between 8 and 6 bit periods prior to the reference time, the RF output power shall remain at least 20 db below the minimum power requirements of 100 watts (+50 dbm) at the antenna. c. During the Active state, defined as beginning at the reference time and continuing for the duration of the message, the RF output power shall be 100 watts(+50 dbm) minimum and 250 watts (+54 dbm) maximum. d. The RF output power shall not exceed the maximum limits of 250 watts (+54 dbm) at any time during the ADS-B Message Transmission Interval. e. Within 6 bit periods after the end of the Active state, the RF output power shall be at a level at least 20 db below the minimum power requirement of 100 watts (+50 dbm). f. Within 8 bits periods after the end of the Active state, the average RF output power shall fall to a level not to exceed -80 dbm Conditions Reference DO-282A section for test setup and test procedures Measurements 1. Measure the average RF output power prior to 8 bit periods before the reference time. Ensure the power bandwidth is 2MHz. Record the results. 2. Measure the average RF output power between 8 and 6 bit periods before the reference time. Ensure the power bandwidth is 300kHz. Record the results. 3. Measure the average RF output power during the active state. Ensure the power bandwidth is 300kHz. Record the results. 4. Measure the average RF output power between 6 and 8 bit periods after the active state. Ensure the power bandwidth is 300kHz. Record the results.

13 5. Measure the average RF output power greater than 8 bit periods after the active state. Ensure the power bandwidth is 2MHz. Record the results Data Edge >8uS(dBm) 6-8uS(dBm) Active State(dBm) >20dB Difference Rising Falling HP89441A Pictures Figure Prior to 8 Bit Periods Before Reference Time

14 Figure to 6 Bit Periods Before Reference Time Figure Active State Near the Rising Edge

15 Figure Active State Near the Falling Edge Figure to 8 Bit Periods After Active State

16 Figure >8 Bit Periods After Active State 1.9 In Band Transmission Spectrum (DO-282A section ) Requirements The average spectrum of a UAT message transmission modulated with pseudo-random payload data shall fall with in the limits specified in the Table and Figure when measured in a 100 KHz bandwidth Conditions Reference DO-282A section for test setup and test procedures Measurements Measure and record the power versus frequency specified in the table below Frequency Offset (MHz) Relative Max Power (db) ± ± ± ± ± ±

17 1.9.4 Data HP89441A Pictures Frequency(MHz) Power(dBm) Difference Figure In Band Spectrum 1.10 Out of Band Emissions (DO-282A section ) Requirements Out of band emissions shall comply with applicable FCC regulations beyond 250% of the authorized bandwidth that is 3.25 MHz from the center frequency. Reference 47 CFR, paragraph and ICAO SARPs section Note that the SARPs adds specific requirements in the band of 1020 to 1040 MHz.

18 Conditions Connect the spectrum analyzer to the selected antenna port with enough in line attenuation to limit the input power into the spectrum analyzer < 0 dbm Measurements Verify that the emissions are below the specified limits in FCC regulation Reference 47 CFR; paragraph Pass Fail Verify that the emissions are below the specified limits in ICAO SARPS section Pass Fail Spectrum Analyzer Plots Figure MHz to 3GHz

19 Figure GHz to 6GHz

20 This report needs to be completed from this point on for Unit 3, the data is for Unit 2. Prior data is good for Unit Broadcast Message Characteristics ( DO-282A section 2.2.3) Requirements General Message requirement Conditions N/A Measurements N/A 1.12 ADS-B Message Format ( DO-282A section ) Requirements UAT ADS-B message shall contain the elements of bit synchronization, payload, and FEC parity, in that order Conditions N/A Measurements As illustrated in Figure 1.6-1, and the Figure noisy header, quiet repeating payload data, and noisy FEC parity. ADSB message contains bit synchronization, payload, and FEC. Pass X Fail 1.13 Synchronization ( DO-282A section ) Requirements The payload message shall include a 36 bit synchronization sequence. For the ADS-B Messages the sequence shall be: with the left-most bit transmitted first Conditions Reference DO-282A section for test setup and test procedures Measurements Verify that the first 36 bit synchronization sequence is the same as the sequence called out in paragraph Pass Fail

21 1.14 Payload ( DO-282A section ) Requirements 144 bit or 272 bit payload sequence shall be as defined in DO-282A section Conditions No specific test procedure is required to validate section Measurements The payload sequence was observed on the test equipment numerous times with quick verifications possible by transmission of payloads containing easily recognized repeating patterns (ie , , and as examples). Figure 1-3 Transmission capture showing the " " pattern of the 272 bit payload data 1.15 FEC Parity ( DO-282A section ) Requirements FEC Parity generation shall be based on a systematic Reed-Solomon (RS) 256-ary code with 8 bit code word symbols Conditions Appropriate test procedures required to validate the requirements are found in DO-282A section

22 Measurements Verified in section Code Type ( DO-282A section ) Requirements FEC Parity generation shall be per the following code: a. Basic ADS-B message: Parity shall be per a RS (30, 18) code. b. Long ADS-B message: Parity shall be per a RS (48, 34) code Conditions Reference DO-282A section for test setup and test procedures Measurements Verified in section Generation and Transmission Order of FEC Parity ( DO-282A section ) Requirements FEC Parity bytes are ordered most significant to least significant in terms of the polynomial coefficients they represent. The ordering of bits within each byte will be most significant to least significant. FEC Parity bytes will follow the message payload Conditions Reference DO-282A section for test setup and test procedures Measurements a. Verify that the ADS-B UAT Transmitting System properly generates the associated FEC Parity sequence as given in column 3 Table 2-73 of DO-282A for the Basic ADS-B message for line items 3, 13, and 23. Pass X Fail b. Verify that all of the FEC symbol sequences generated in column 3 of Table 2-73 of DO- 282A follow the trailing end of the associated transmitted messages in left to right order for line items 3, 13, and 23. Pass X Fail c. Verify that the ADS-B UAT Transmitting System properly generates the associated FEC Parity sequence as given in column 3 Table 2-74 of DO-282A for the Long ADS-B message for line items 1, 11, 21, 31, 41, and 51. Pass X Fail

23 d. Verify that all of the FEC symbol sequences generated in column 3 of Table 2-74 of DO- 282A follow the trailing end of the associated transmitted messages in left to right order for line items 1, 11, 21, 31, 41, and 51. Pass X_ Fail (refer to capture files in delivery disk directory: \Test Data\FEC Parity check ) 1.18 ADS-B Message Payload ( DO-282A section 2.2.4) Requirements a. Payload shall be structurally consistent with DO-282A section , , and b. Per note 6 of S.O.W.: Message Payloads for the prototype transmitter shall be in accordance with the requirements provided in section of this document. c. Per SOW: section [1] Selectable length (payload 144 or 272 bits) [2] Repeating alternating pattern ( ) [3] Pseudo-random [4] Pre-determined payload (tables 2-73 and 2-74 of RTCA/DO-282) Conditions No specific test procedure is required to validate section Payload is implicit in the message data transferred to the UAT transmitter via the PC serial interface. An external method is expected to be used to generate payload data from desired State Vector values Measurements Payload is per SOW section Pass X Fail 1.19 Procedures for Processing of Time Data ( DO-282A section 2.2.5) Requirements Provide input and monitoring of GPS Time Tag for transmission timing determination Conditions Provide an input 1 PPS GPS Time Tag, and select this external GPS Time Tag source via PC interface. Verify that the transmission time corresponds with the currently selected MSO value as referenced from the provided GPS Time Tag rising edge.

24 Measurements MSO transmit timing was visually inspected to verify that it is referenced from the externally supplied GPS Time Tag rising edge. Pass X Fail 1.20 Procedures for ADS-B Message Transmission ( DO-282A section 2.2.6) Requirements a. Section : NOT Implemented. MSO is either Pseudo-Random, or explicitly provided via the PC interface. b. Section : Relationship of MSO to the Modulated Data: Time TX = (250*MSO) +/- 500 ns following the 1PPS GPS Time Tag rising edge Conditions c. From the currently selected GPS Time Tag signal, measure the time from the rising edge of the GPS pulse to the start of the transmit message. This start is 3.84 us BEFORE the 1 st bit of the synchronization sequence (4-bit periods). d. Measure this time for each of the following MSO values: a us b us c us Measurements MSO transmit timing is ns +3.8 us +/- 500 ns at MSO = 752 MSO transmit timing is ns +3.8 us +/- 500 ns at MSO = 2352 MSO transmit timing is ns +3.8 us +/- 500 ns at MSO = 3951 Pass X Fail 1.21 UAT Transmitter Message Data Characteristics (DO-282A section 2.2.7) Requirements Per note 7 Table 2-1 of SOW: RTCA/DO-282 section requirements not implemented Conditions The UAT Transmitter A3 prototype will not be directly responsible for the processing of data as specified in the DO-282A section

25 Measurements N/A 1.22 Self Test and Monitors ( DO-282A section ) Requirements Output power monitor shall annunciate the loss of power via the serial digital output interface. Loss of Lock monitor shall annunciate the loss of synthesizer lock via the serial digital output Conditions While transmitting 1/sec pulses, apply a ground to pin 3 of U25 (+ input to OP291 Operational Amplifier) to simulate a low/loss of transmit power. While transmitting 1/sec pulses, apply a ground to pin 1 of Q5 (base of PNP transistor) to simulate a loss of lock error condition Measurements Verify that the loss of power error message is not displayed while pin 3 of U25 IS NOT grounded, and is generated and displayed by the UAT digital interface link application during the time that pin 3 of U25 IS grounded. Pass X Fail Verify that the loss of lock monitor error message is not generated while pin 1 of Q5 IS NOT grounded, and is generated and displayed by the UAT digital interface link application during the time that pin 1 of Q5 IS grounded. Pass X Fail 1.23 Interfaces ( DO-282A section ) Requirements MOPS section # Requirement Sufficient update rate to support the UAT Message update Rates of section (1 per second transmission) Discrete inputs provide appropriate protection (ie: diode isolation) Approved Avionics Digital Communication interfaces, and appropriate error control techniques for input interfaces Input processing capable of satisfying the UAT Message update Rates of section

26 outputs implement appropriate protection (ie: diode isolation) Approved Avionics Digital Communication interfaces, and appropriate error control techniques for output interfaces Conditions By inspection of schematic and system design Measurements and PC to UAT communication rate is sufficient to allow updating of transmit data payload quickly enough to implement the update rates of section However, the interface utilizes user input which degrades the update rate. UAT software and PC software provides for selection of random or repeating data which allows UAT transmissions without constant data update from the PC interface and By inspection the discrete I/O signals are proided with diode protection to Ground and +5 VDC. Serial digital interfaces utilize standard hardware protocols and Interfaces and error control employ standard serial interface protocols for RS232 and USB implementations.

27 2 Software Load UAT unit #2 is loaded with the software load 5509boot_UNIT2_FINAL.hex. This software build has a specifically measured timer set value for timeout of the MSO counter on the final count before transmission. Differences in the Prototype designs required this optimization to meet the GPS to MSO transmit timing specifications. The code difference is expressly limited to the following variable within the timer.c source file. The variable PRD1 in timer.c is set to the value of 47384, corresponding to a final timer count time of us.