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Important Characteristics of Digital Oscilloscopes and

and Southeastern Michigan present…. Important Characteristics of Digital Oscilloscopes and RADAR Pulse Measurements with Digital Oscilloscopes. Vince Woerdeman, Agilent Technologies. Marty Gubow, Agilent Technologies.

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Important Characteristics of Digital Oscilloscopes and

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  1. and Southeastern Michigan present… Important Characteristics of Digital Oscilloscopes and RADAR Pulse Measurements with Digital Oscilloscopes Vince Woerdeman, Agilent Technologies Marty Gubow, Agilent Technologies 5:30 – 6:00 Pizza and Refreshments6:00 – 7:00 Technical PresentationThis is a FREE event. Non-Members Welcome!

  2. Agenda Evaluating a Scope’s Performance Characteristics • What Bandwidth is needed? • What Sample Rate is needed? • How does Nyquist’s Theorem and aliasing apply to oscilloscopes? • Acquisition Errors and Interleave Distortion • What are other important characteristics?

  3. Evaluating Performance Characteristics • Is Full Scope Functionality Retained? • Required Number of Channels? • Required Bandwidth/Acquisition Performance? • Waveform Update Rate, Decode Update Rate, Probing, Ease-of-use, Display Quality, Triggering, etc.?

  4. “Rule-of-thumb” Bandwidth Suggestion Scope Bandwidth Suggested Bandwidth = 5X Highest Clock Rate Allows capture of the 5th harmonic with minimum attenuation.

  5. Accurate Bandwidth Determination Step #1: Determine fastest rise/fall times of device-under-test. Step #2: Determine highest signal frequency content (fKnee). fKnee = 0.5/RT (10% - 90%) fKnee = 0.4/RT (20% - 80%) Step #3: Determine degree of required measurement accuracy. Step #4: Calculate required bandwidth. Source: Dr. Howard W. Johnson, “High-speed Digital Design – A Handbook of Black Magic”

  6. System Bandwidth Calculation Example Determine the minimum required bandwidth of an oscilloscope with an approximate Gaussian frequency response to measure a 500ps rise-time (10-90%): fKnee = (0.5/500ps) = 1GHz 3% Accuracy: Scope Bandwidth = 1.9 x 1GHz = 1.9GHz 20% Accuracy: Scope Bandwidth = 1.0 x 1GHz = 1.0GHz 3% Accuracy: Scope Bandwidth = 1.4 x 1GHz = 1.4GHz

  7. Analog Bandwidth Comparisons Rise Time = 495ps 2GHz Rise Time = 550ps Scope 1GHz Scope Rise Time = 750ps 500MHz Scope What does a 100 MHz clock signal really look like? Rise Time = 2.5ns 100MHz Scope

  8. How Much Sample Rate is Required? Engineer Fred has total trust in Dr. Nyquist and says: “2X over the scope’s bandwidth.” Engineer Betty doesn’t trust Dr. Nyquist and says: “10X to 20X over the scope’s bandwidth.” The truth lies somewhere in between!

  9. Nyquist’s Sampling Theorem Nyquist’s sampling theorem states that for a limited bandwidth (band-limited) signal with maximum frequency fmax, the equally spaced sampling frequency fs must be greater than twice of the maximum frequency fmax, i.e., fs > 2·fmax in order to have the signal be uniquely reconstructed without aliasing. The frequency 2·fmax is called the Nyquist sampling rate (fS). Half of this value, fmax, is sometimes called the Nyquist frequency (fN). Dr. Harry Nyquist

  10. Nyquist’s Basic Rules… But not-so-simple for DSO technology • fMAX < fS/2 • The highest frequency sampled MUST be less than fS/2… • This is NOT the same as oscilloscope bandwidth. • Samples MUST be equally spaced • The forgotten rule!

  11. Ideal Brick-wall Response w/ BW @ Nyquist (fN) 0dB -3dB Attenuation fS fN Frequency

  12. Gaussian Response w/ BW @ fS/2 (fN) 0dB -3dB Attenuation Aliased Frequency Components fS fN Frequency

  13. 500MHz scope sampling @ 1GSa/s (BW = fS/2 = fN)

  14. Maximally-Flat Response w/ BW @ fS/2.5 (fN/1.25) Gaussian Response w/ BW @ fS/2 (fN) Gaussian Response w/ BW @ fS/4 (fN/2) Aliased Frequency Components fS/4 fS/2.5 0dB -3dB Attenuation Aliased Frequency Components fS fN Frequency

  15. 500-MHz scope (2 GSa/s vs. 4 GSa/s) Input = 100 MHz clock with 1 ns edge speeds 2 GSa/s (fBW = fS/4 = fN/2) 4 GSa/s (fBW = fS/8 = fN/4)

  16. 6-GHz scope (20 GSa/s vs. 40 GSa/s) Input = 1.25 GHz clock with 100 ps edge speeds 20 GSa/s (fBW = fS/3.3) 40 GSa/s (fBW = fS/6.6)

  17. Complying with Nyquist’s Rule #1 (fS > 2 x fMAX) • 2X sampling violates Rule #1 • 2.5X to 5X sampling sufficiently satisfies Rule #1 • > 5X sampling provides further compliance with Rule #1… IF additional error sources are not introduced that violate Rule #2 Engineers often overlook Rule #2… “Samples MUST be evenly spaced”

  18. Real-time Non-interleaved ADC System Input ACQ MEM ADC #1 To CPU Analog Amplifier Sample Clock

  19. Sample Rate > 4 x fBW (Non-interleaved) = Input Signal = Sample Clock = Sin(x)/x Interpolated Waveform = Real-time Digitized Point Sin(x)/x Interpolated Waveform Input Signal Sample Clock

  20. Real-time Interleaved ADC System Input Input ACQ MEM ADC #2 To CPU ½ Clock Delay ACQ MEM ADC #1 To CPU Analog Amplifier Sample Clock Accurate ADC interleaving requires: • Matched vertical response of each ADC • Precise phased-delayed clocking

  21. SR > 8 x fBW (Perfectly Interleaved) = Input Signal = Sample Clock = Sin(x)/x Interpolated Waveform = Real-time Digitized Point Sin(x)/x Interpolated Waveform Input Signal Clock #1 Clock #2

  22. SR > 8 x fBW (Poorly Interleaved) = Input Signal = Sample Clock = Sin(x)/x Interpolated Waveform = Real-time Digitized Point Sin(x)/x Interpolated Waveform Input Signal Clock #1 Clock #2

  23. Testing for Interleave Distortion Interleave distortion violates Nyquist’s Rule #2: “Samples must be evenly spaced” • Effective bits analysis using sine waves • Visual sine wave test • Spectrum analysis • Measurement stability/repeatability

  24. 1-GHz Sine Wave on 1-GHz BW Scopes 4 GSa/s (non-interleaved) 20 GSa/s (interleaved) Interleave Distortion 4 GSa/s produces superior results compared to 20 GSa/s

  25. 2.5-GHz Sine Wave on a 3-GHz Scope 20 GSa/s (Single-chip ADC) 40 GSa/s (Dual-interleaved ADC chip-set) Vp-p (σ) = 2.4 mV Vp-p (σ) = 1.8 mV Precision ADC interleaving technology produces improved measurements

  26. 2.5-GHz Sine Wave on a 2.5-GHz Scope Interleave Sampling Distortion 10 GSa/s (Single-chip ADC) 40 GSa/s (Quad-interleaved ADC chip-set) Vp-p (σ) = 9.1 mV Vp-p (σ) = 12.0 mV Poor ADC interleaving technology produces degraded measurements

  27. FFT Analysis of 2.5-GHz Sine Wave at 40 GSa/s 3-GHz Scope 2.5-GHz Scope 10-GSa/s Distortion (-32 dB) 40-GSa/s Distortion

  28. 400-MHz Clock Sampled @ 40 GSa/s 3-GHz Scope 2.5-GHz Scope Rise Time (avg.) = 250ps Rise Time (range) = 35ps Rise Time (σ) = 3.3ps Rise Time (avg.) = 254ps Rise Time (range) = 60ps Rise Time (σ) = 10ps

  29. FFT Analysis of 400-MHz Clock at 40 GSa/s 3-GHz Scope 2.5-GHz Scope 10-GSa/s Distortion (27 dB below 5th harmonic) 40-GSa/s Distortion

  30. Other Oscilloscope Characteristics to Consider • Waveform Update Rate • Advance Analysis • Display Quality • Ease-of-use • Probing • Price

  31. InfiniiMax Active Probe Extension Allows for environmental chamber testing up 105 degrees C.

  32. Questions and Answers Q & A

  33. Oscilloscope Radar Measurement Basics

  34. Agenda • Introduction • Pulsed Power and Power Spectrum Measurements • Noise Measurements • Component Measurements • Evaluating I/Q Demodulator Errors • Pulsed Component Measurements • Time Domain Measurements • Jitter Measurements Radar Measurement Basics

  35. Introduction Radar Measurement Basics

  36. Surveillance Search and track Fire control Navigation Missile guidance Proximity fuses Altimeter Terrain avoidance Weather mapping Space Some Typical Radar Applications Radar Measurement Basics

  37. ParameterTypical Range Frequency………………………………..100MHz - 95GHz Pulse Width (PW)……………………….10nsec to Infinite (CW) Pulse Repetition Frequency …………30Hz to 300KHz Rise Time………………………………...1nsec - 100nsec Duty Cycle……………………………….0.01% - 100% Peak Power………………………….…..1W - 50MW Pulse Compression…………………….FM, Phase Coded Frequency Agility……………………….100MHz - 2GHz (BW) The Wide Range of Measurement Requirements Radar Measurement Basics

  38. Simplified Pulse Doppler Radar Block Diagram Antenna PULSED RF DUPLEXER PREDRIVER POWER AMP COHO BPF AMP BPF TRANSMITTER STALO PULSE PRF RECEIVER MODULATOR GENERATOR PROTECTION Transmitter/Exciter LNA VIDEO FREQUENCY ADC S/H LPF AMP AGILE L.O. o 0 Doppler SPLITTER LPF COHO LIMITER DISPLAY and Range FFT o 1st 2nd IF IF 90 Processor IFA IFA BPF BPF 2nd L.O. VIDEO LPF S/H ADC AMP Receiver/Signal Processor Radar Measurement Basics

  39. Active Electronically Steered Antenna Wave Front Transceiver Animation Radar Measurement Basics

  40. Agenda • Introduction • Pulsed Power and Power Spectrum Measurements • Noise Measurements • Component Measurements • Evaluating I/Q Demodulator Errors • Pulsed Component Measurements • Jitter Measurements • Time Domain Measurements Radar Measurement Basics

  41. Pulsed Power and Power Spectrum Measurements Radar Measurement Basics

  42. Why Measure Power? 4 P  t R • High peak power influences the expense of the system $ $ Modulator, Output PFN, etc. Stage • Power determines the absolute range R Radar Measurement Basics

  43. Instruments Used to Measure Power • Vector Signal Analyzer • Power Meter • Spectrum Analyzer Radar Measurement Basics

  44. Agenda • Introduction • Pulsed Power and Power Spectrum Measurements • Noise Measurements • Component Measurements • Evaluating I/Q Demodulator Errors • Pulsed Component Measurements • Time Domain Measurements • Jitter Measurements Radar Measurement Basics

  45. Noise Figure S N S N G -the degradation in the signal-to-noise ratio as the signal passes through the network in out (S/N)in Noise Figure, F = (S/N)out T= 290°K Radar Measurement Basics

  46. N8975A Noise Figure Analyzer • Wide frequency range (1.5GHz/3GHz/26.5GHz) • Graphical data display • Ease of use • Variable IF bandwidths • Intuitive user interface • Smart Noise Source (cal files stored in EEPROM and internal temperature sensor) Radar Measurement Basics

  47. Agenda • Introduction • Pulsed Power and Power Spectrum Measurements • Noise Measurements • Component Measurements • Evaluating I/Q Demodulator Errors • Pulsed Component Measurements • Jitter Measurements • Time Domain Measurements Radar Measurement Basics

  48. Component Test Radar Measurement Basics

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