Advances in EMI Receiver Architecture

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Loraine Ball
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1 Advances in EMI Receiver Architecture

2 Agenda EMI Receiver Requirements Architecture Improvements Digital IF 2dB Attenuation Improved Upgradability Processor, I/O storage Enhanced Diagnostic capability Enhanced Application capability

3 What is an EMI Receiver? Let s begin with a spectrum analyzer Spectrum Analysis Display and measure amplitude versus frequency for RF & MW signals Separate or demodulate complex signals into their base components (sine waves) 3

4 Theory of Operation Swept Spectrum Analyzer Block Diagram RF input attenuator mixer IF gain IF filter (RBW) envelope detector Input signal Pre-Selector Or Low Pass Input Filter local oscillator Log Amp video filter sweep generator Crystal Reference Oscillator ADC, Display & Video Processing 4

5 Compliance EMI receiver requirements A CISPR receiver must have the following functionality in the range 9 khz - 18 GHz: A normal +/- 2 db absolute accuracy CISPR-specified resolution bandwidths (-6 db) Peak, quasi-peak, EMI average, and RMS average detectors Specified input impedance with a nominal value of 50 ohms; deviations specified as VSWR Be able to pass product immunity in a 3 V/m field Be able to pass the CISPR pulse test (implies pre-selector below 1 GHz) Other specific harmonic and intermodulation requirements

6 Receiver requirements above 1 GHz Above 1 GHz regulations require: 1 MHz bandwidth for measurements No quasi-peak detector No CISPR pulse test, meaning no additional pre-selector required excellent sensitivity According to current FCC regulations, the maximum test frequency is the fifth harmonic of the highest clock frequency for an unintentional radiator (for example, computers without wireless connectivity) and the tenth harmonic for an intentional radiator (such as a cellular phone or wireless LAN). 6

7 MXE Preselector Simplified Block Diagram RF In 1 Bypass Switch RF In 2 Limiter Attenuators Input Switch Conducted Filter Assembly (13 filter paths) Conducted Band Preamp & Overload Detector * Limiter and Pre-Filters Band Switch * Band Switch * Radiated Filter Board (7 filter paths) Radiated Band Preamp & Overload Detector * * On Input Assembly 7

8 LB 20 Hz -1GHz CFB INB DDS RFB Noise Source

RF Pre-selection (RF input filtering) Purpose of RF pre-selection Help to prevent overload by reducing the total energy at the input mixer The RF preselector tracks the center

9 RF Pre-selection (RF input filtering) Purpose of RF pre-selection Help to prevent overload by reducing the total energy at the input mixer The RF preselector tracks the center frequency of the EMI receiver The bandwidth of the RF preselector is wider that the widest RBW used Useful in measuring broadband signals Narrow band signals Broadband signals

10 Modern spectrum analyzer Resolution BW Selectivity or Shape Factor 3 db 3 db BW 60 db 60 db BW Selectivity = 60 db BW 3 db BW Determines resolvability of unequal amplitude signals 10

11 CISPR Bandwidth Requirements Bandwidth -6dB -20dB Measurement Range CISPR Band CISPR Bandwidth 9 KHz 150KHz A 200 Hz 150 KHz 30 MHz B 9 KHz 30 MHz 1 GHz C/D 120 KHz > 1GHz E 1 MHz 11

12 MIL-STD-461 Bandwidth Requirements Measurement Range 30Hz - 1 KHz -6dB Bandwidth 10 Hz 1 KHz -10 KHz 100 Hz 10 KHz KHz 1 KHz 150 KHz - 30MHz 10 KHz 30 MHz - GHz 100 KHz > 1GHz 1 MHz 12

13 Detectors: Convert IF Samples to Display Bins or Buckets Multiple simultaneous detectors Peak, Neg Peak, Sample Display points or buckets Peak Normal, Average, Neg Peak Volts Sample Neg Peak Screen Shot Detector 3types Time 13

14 Classic Super Heterodyne Receiver Architecture Analog IF Structure Input Signal RF Input Attenuator 5 or 10 db Steps Downconversion IF Filter IF Gain Log Amp Video Filter Log ADC Pre-selector Local Oscillator Reference Oscillator Step/Sweep Generator Video Display

Receiver Architecture w/ Digital IF Digital Conversion at IF instead of Video Offers Improved: Improved Accuracy Improved BW filter shape Increased usable Dynamic Range ADC Signal Digitized After RF

15 Receiver Architecture w/ Digital IF Digital Conversion at IF instead of Video Offers Improved: Improved Accuracy Improved BW filter shape Increased usable Dynamic Range ADC Signal Digitized After RF Down- Conversion DSP Log Amplification RBW Filtering Detection Video Filtering Averaging Display Scaling Downconversion IF Filter IF Gain Log Amp Video Filter Input Signal Log ADC RF Input Attenuator 5 or 10 db Steps Pre-selector Local Oscillator Reference Oscillator Step/Sweep Generator Video Display

16 Input Connector Digital IF Improves Amplitude Accuracy RF Input Attenuator 5 or 10 db Steps Pre-selector Downconversion ADC DSP Discuss in ter what the impr bring the cust Input connector (mismatch) Calibrator RF input attenuator flatness and switching Mixer and input filter frequency response Frequency Dependent Frequency Independent Digital IF improves Amplitude Accuracy: Ref Level switching uncertainty (IF gain) Level correction digitally synthesized RBW filter switching uncertainty RBWs all digitally synthesized Display scale fidelity (Log Amp) Log response & display scaling digitally synthesized IF Filter IF Gain Log Amp Video Filter Log ADC

17 Digital IF Resolution BWs Offer Higher Selectivity Better shape factor, biggest selectivity benefit for different signal levels Equivalent selectivity at a wider, faster-sweeping RBW ANALOG FILTER Typical Selectivity Analog ~12:1 Digital 5:1 DIGITAL FILTER RES BW 100 Hz SPAN 3 khz

18 Digital Filter Shape Better shape factor, biggest selectivity benefit for different signal levels Equivalent selectivity at a wider, faster-sweeping RBW digital filters swept an additional 3-4x faster 30 khz Digital Filter 18

19 Digital RBWs Reduce Required Sweep Time 8563E Analog RBW PXA Digital RBW PXA FFT RBW 280 sec 134 sec 10.7 sec

20 Digital IF Gain Improves Usable Dynamic Range 50dB change in Reference Level - virtually no change in measured value - simplifies measurement procedures - reduces measurement errors Confidentiality Label May 9, 2012

.useful when measuring on an open site with large ambient signals

21 2dB Step Attenuation: Improves Accuracy in the Presence of Large Ambient Signals..useful when measuring on an open site with large ambient signals 2dB/division. 10dB/division. Large ambient signal 3-4 db diff. Input Attn. 10dB 6dB 2dB 0dB Confidentiality Label May 9, 2012

22 2dB Step Attenuation: Enhances Dynamic Range Optimization DR DANL 2 db Step Attenuator 3rd Order Worst case DR due to insufficient Atten step size Potential DR Given Up Optimum DR Mixer Level Dynamic Range Vs. Distortion and Noise Lost Dynamic Range (db) Attenuator Step Size (db) Simplistic View CW Distortion Noise-like Distortion Loss of Dynamic Range

23 Improved Upgradability: Replaceable CPU, I/O, Storage You can upgrade your processing capability as: - Commercial processor technology evolves - Evolution of I/O connectivity/speed - Stay current with CPU upgrade vs. new instrument purchase Removeable solid-state drives convenient for secure environments Confidentiality Label May 9, 2012

24 Enhanced Diagnostic Capability: Spectrum Analysis Agilent has a long history of blending the diagnostic capability of Spectrum Analysis with Compliance Receivers Confidentiality Label May 9, 2012

25 Enhanced Diagnostic Capability: New Functionality Features Strip Chart Capability - Track detector values vs. time simultaneously - 20 minutes of gapless data Spectrogram - View time-varying signals Confidentiality Label May 9, 2012

26 T R A C E Z OOM Enhanced Diagnostic Capability: New Functionality Trace Zoom Allows you to zoom in on your trace data Same trace in both screens but bottom screen shows close up view with fewer points Great to look more closely at high-density traces Zone Span Two different sweeps in the two windows Bottom window provides detail view of span indicated in top window

27 P X A S I G N A L A N A LY Z E R A P P L I C AT I O N S Improved Application Capability Expand Receiver Functionality with Optional Measurement Applications IQ Analyzer (included) External Source Control 89600B VSA SW Analog Demod Noise Figure Phase Noise 27

28 Introducing the New Agilent N9038A MXE EMI Receiver Blending World-Class EMI Receiver and Diagnostic Signal Analysis Capabilities

29 N9038A MXE EMI Receiver Offers World-Class EMI Receiver Performance Excellent accuracy GHz Excellent sensitivity GHz Two inputs - 1 full frequency range input - 1 surge protected input to 1 GHz - RF Preselection - Available on both inputs 20 Hz to 1 GHz surge protected 20 Hz to 8.4 GHz or 20 Hz to 26.5 GHz

30 N9038A MXE EMI Receiver Blends World-Class EMI Measurement Functionality... Simultaneous updates for up to three detectors Built-in amplitude correction Built-in limit lines Automatic testing to limit lines and user-defined margins Automated signal list collection Automated signal list measurement

31 with State of the Art EMI Diagnostic Capability Extensive set of built-in diagnostic tools Signal Analysis Strip Chart Spectrogram Zone Span Global frequency linkage More than just an EMI receiver.the MXE includes Agilent s X-Series signal analysis capability!

32 Q&A More information can be found at:

Jeff Thomas Tom Holmes Terri Hightower. Learn RF Spectrum Analysis Basics

Jeff Thomas Tom Holmes Terri Hightower Learn RF Spectrum Analysis Basics Learning Objectives Name the major measurement strengths of a swept-tuned spectrum analyzer Explain the importance of frequency