RF Measurements You Didn't Know Your Oscilloscope Could Make

Transcription

1 RF Measurements You Didn't Know Your Oscilloscope Could Make January 21, 2015 Brad Frieden Product Manager Keysight Technologies

2 Agenda RF Measurements using an oscilloscope (30 min) When to use an Oscilloscope vs Spectrum Analyzer? What RF measurement capability exists on your scope? (FFT) Advances in scope-based FFTs (annotation, gating, multiple FFT) Using Functions for Additional RF analysis Determining how good of RF your scope will make (RF characterization all scopes are not created equal) Complimenting the Scope with Additional RF analysis software (15 min) Wideband EVM, & modulation examples Page 2

3 Why is this so important? Increase your debug and validation efficiency through oscilloscope frequency domain views Where is that noise coming from in the power distribution system? Quick, convenient view of expected DUT spectral content May be one of the few ways to perform validation analysis of wideband RF signals Practical understanding of the limits of test with new oscilloscope technology help you choose the right tools to complete validation Learn techniques and tools to allow long target capture time, necessary to evaluate prototypes Why is this so important? What valuable thing will you take away/learn that will save you time/money or improve productivity Page 3

4 # Channels 90000A Series X Series Z Series Up to 4 The challenge of signal spectral bandwidth and number of channels needed S-Series Oscilloscope 1 PXA 160 MHz UXA 510 MHz 0 MHz BW 160 MHz BW 510 MHz BW 8 GHz BW 13 GHz BW 32 GHz BW 63 GHz BW RF Signal Spectral Bandwidth Page 4

5 Product Strengths For RF Spectrum / signal analyzers In-band Oscilloscopes In-band Out of band Widest analysis bandwidth Automated RF More than one channel Best dynamic range Fast throughput with narrow Resolution Bandwidth Segmented memory to maximize target capture time Also offers sophisticated time domain analysis tools Page 5

6 Oscilloscope Functions Advanced Math - Every modern scope includes a variety of math functions - Math functions can: Help you view waveforms in unique and meaningful ways Can be a huge debug/test productivity boost Included are FFTs - # of functions vary by oscilloscope - Some scopes allow Matlab.m import for more complex functions Measurements - Fundamental to scope usage. - Can be made on FFTs and other functions Page 6

7 Frequency Domain Function Examples Clock signal & harmonics Coupling from unexpected sources Wideband FFTs Page 7

8 More Memory with Fixed Sample Rate Better RBW Tradeoff = processing speed 20Kpts RBW=1.5 MHz 1 Mpts RBW= 7.5 khz Page 8

9 Live: 1 GHz sine input example Page 9

10 Hot application today is power integrity Power distribution noise translates into various clock jitter New Power Rail probe, 2 GHz BW, 50k ohm, 1:1, +/- 24V offset Can apply offset to allow a close zoom onto the power noise The FFT can yield very important clues for noise sources Customizable in Footer Page 10

11 Live: Power supply noise measurement example Page 11

12 10 GHz coupled clock seen in the FFT view Then can trigger on that clock, average out all other noise Power rail Time gate zoom 10 GHz clock Time gate zoom on clock 10 GHz coupled clock seen amidst power supply switching noise Customizable in Footer Page 12

13 Live: wideband pulse RF Page 13

14 Use Functions for Advance RF Measurements 1 GHz Wide Chirp Example using 5 scope functions Meas Trend of Clock TIE to see inverse of phase shift Time view of single RF pulse in pulse train Meas Trend of Frequency to see frequency shift across the RF pulse (1 GHz linear shift) FFT of an RF pulse (variety of FFT window options) Example: 1 usec wide RF pulses, linear FM 3.5 GHz to 4.5 GHz, 10 usec PRI Page 14

15 Multiple FFTs Multiple gates Multiple FFTs on same waveform with different Start/Stops FFT per input channel Page 15

16 Live demo: Gated FFTs Time gate of 80 us Page 16

17 Gated FFTs for Time/Frequency Correlation Page 17

18 How Good of RF Measurements Will Your Scope Make? Not all scopes are created equally Scope datasheet typically doesn t include RF characterization Scopes with better signal integrity technology blocks (low-noise front end, correction filters, higher ENOB) will have higher quality RF Find out Do a conversion from time-based specs Ask scope manufacturer for this info Page 18

19 Keysight Characterization Example TOI & EVM MSO-S 804A Third Order Intercept (TOI) Power of one tone (0 dbm) + ½ Delta marker = db = 22.5 db PSG Signal Generator MSOS804A EVM W-LAN 2.4 GHz 20 MHz wide 0.47% EVM rms PSG Signal Generator + VSA Page 19

20 Oscilloscope Improvements over 1 Generation Amplitude and phase flatness Amplitude Amplitude 1 db/div 1 db/div Phase Phase 20 deg/div 20 deg/div 0 Hz 10 GHz 4 GHz BW 9000 Series --- no acquisition correction 0 Hz 10 GHz 8 GHz BW S-Series --- using acquisition correction Page 20

21 Oscilloscope Improvements over 1 Generation Phase Noise Example DSO db/hz S Series -120 dbm/hz Page 21

22 Example: Getting Noise Density from V rms Noise From S-Series Data Sheet V/div dbm Ref Level dbm/hz Noise 50 mv/div and 8 GHz BW 1mV/div -28 dbm -158 dbm/hz ** 2mV/div -28 dbm -158 dbm/hz 5mV/div -24 dbm -156 dbm/hz 10mV/div -18 dbm -154 dbm/hz 20mV/div -12 dbm -150 dbm/hz 50mV/div -4 dbm -143 dbm/hz 100mV/div +2 dbm -136 dbm/hz 200mV/div +6 dbm -130 dbm/hz 500mV/div +16 dbm -124 dbm/hz 1V/div +22 dbm -118 dbm/hz 1.4mV rms noise = 8GHz = -44dBm 10log(8E09) = -143dBm/Hz noise density Page 22

23 Ask Your Oscilloscope Manufacturer Keysight Infiniium S-Series example Page 23

24 Agenda RF Measurements using an oscilloscope (30 min) When to use an Oscilloscope vs Spectrum Analyzer? What RF measurement capability exists on your scope? (FFT) Advances in scope-based FFTs (annotation, gating, multiple FFT) Using Functions for Additional RF analysis Determining how good of RF your scope will make (RF characterization all scopes are not created equal) Complimenting the Scope with Additional RF analysis software (15 min) Wideband EVM, & modulation examples Page 24

25 Additional Analysis VSA (Vector Signal Analysis) App can run on the scope, or on a PC Additional analysis Spectrum math EVM Channel power PSD ACP OBW Constellation diagrams Page 25

26 Demo of VSA with Scope QAM demod 3 GHz wide Page 26

27 Wideband QAM16 Example 3 GHz carrier, 1 GHz wide modulation QAM16 signal Measure of: Constellation diagram Time domain signal Spectrum EVM = 0.58% Page 27

28 Demo of Chirp Radar analysis GHz wide 2 GHz linear FM chirp Measure of: Spectral content Pulse Real Frequency across pulse Unwrapped phase across pulse Page 28

29 Demo of VSA 19 pulse option BHQ Use segmented memory in scopes for long captures Up to 64k segments Full suite of RF pulse Statistical analysis Page 29

30 What have we seen? Scopes for RF New scopes make great, wideband RF receivers, that translate into excellent in-band RF Be careful to consider ResBW / throughput tradeoffs in scope-based FFT Oscilloscopes offer the widest analysis bandwidth to address the latest pulse and communications oriented applications The noise density of new scopes is better than you might have realized, making them applicable to small signal applications Scopes with FFTs are not a replacement for vector signal analyzers Scopes combined with VSA software become a powerful wideband RF measurement suite Page 30

31 Keysight Oscilloscopes for High-Quality RF Measurements S-Series with up to 8 GHz bandwidth 90000A Series with up to 13 GHz bandwidth 90000X Series with up to 32 GHz bandwidth Z-Series with up to 63 GHz bandwidth Page 31

32 Page 32

33 Questions? Page 33

34 Backup Page 34

35 Time and Frequency Domain Translation When you say Time hears Frequency hears Bandwidth DC to a BW Bandwidth around a center frequency Wideband 1GHz or more 10MHz or more DC DC (like a battery) Anything less than 9KHz Channel Connector on front of instrument Communication medium Port Simulation term Connector on front of instrument Decimate Downsample Filter and then downsample Realtime >Nyquist max sample rate. Post processing OK. 50 Ohm termination 50 Ohms to ground- or (for BERTs and some probes) to a Vterm. Gap free processing. 50 Ohms AC coupled. Page 35