1. Using RF Power Sensors and Noise Sources for EMI/EMC/OTA
November 15, 2018
Matthew Diessner
Director of Business Development

2. Agenda RF Power Meter Basics Noise Sources Over the Air Testing
Types of Sensors
Applications
Amplifier testing
Noise Sources
Basics of a Noise Source
Over the Air Testing
Using Noise Sources for Verification and Calibration
Using RF Power Meters for Over the Air Measurement
Supporting Material
Open

3. Before we Continue - Questions
Who uses RF Power Sensors?
Average Power
Peak Power
What do you use it for
Familiar with Noise Sources?
Used for Noise Figure
Calibration and Verification
Unintentional radiators
Over the Air Testing?

4. RF Power Sensors Thermal RF Power Sensor
The Diode Detector for RF Power Sensor
The Peak Power Sensor / Meter
Oscilloscopes and Detectors

5. Thermal RF Power Sensors
Thermocouple based
RF applied to terminated load of a thermocouple sensor and temp rise is measured
Relatively long time constant due to heat flow delays
Accurately measure average power of modulated signals
Handles rare peaks (pulse) well - 20 dB above average power limit
Limited sensitivity around -20 dBm

6. Detector Diode RF Power Sensors
Voltage detectors
Dual diode detector capture both positive and negative carrier cycles
Insensitive to even harmonic distortion
High Frequency diodes detect RF Voltage across a load resistor
At Low input levels: Vout ~ Power
At High input levels Vout ~ Peak RF Voltage

7. Detectors Diode RF Power Sensors
How does it work:
< -20 dBm (30 mV)
Acts as non-linear resistor
Generates Vout ~ square of applied V, this region is called square-law
Vout ~ Pavg even if it is modulated as long as peak power < -20 dBm
> 0 dBm (300 mV peak voltage)
Diode in forward conduction
Smoothing capacitors hold peak RF voltage
Peak detecting region
Vout ~ peak RF Voltage

8. Detector Diode RF Power Sensors
Although very sensitive and easily linearized with digital techniques, diode sensors are challenged by modulation when the signal’s peak amplitude exceeds the upper boundary of the square-law region. In a case where high-level modulation is present, the RF amplitude enters the peak detecting region of the diode detector. In this situation, the detector’s output voltage will rapidly slew towards the highest peaks, then slowly decay once the signal drops. Since the input signal could be at any amplitude during the time the capacitor voltage is decaying, it is no longer be possible to deduce the actual average power of a modulated signal once the peak RF power gets into this peak-detecting region of the diode.
One solution to this problem is to load the diode detector in such a way that the output voltage decays more quickly, and follows the envelope fluctuations of the modulation. This is normally done by reducing the load resistance and capacitance that follows the diodes (RL and CL in figure XXX above). If the sensor’s output faithfully tracks the signal’s envelope without significant time lag or filtering effect, then it is generally possible to properly linearize the output in real time, and perform any necessary filtering on this linearized signal. This allows a sufficiently fast diode sensor to accurately measure both the instantaneous and average power of modulated signals at any power level within the sensor’s dynamic range. This type of sensor is commonly referred to as a Peak Power Sensor, and is discussed in greater detail in Section 4.2.

9. Diode RF Power Sensors – Peak Sensors/Broadband
High dynamic range
-60 dBm to + 20 dBm
Typical max. input power 1 W. (diode - 1 us, thermal – 10W)
High power modules integrating high-power attenuators achieve 50W, the detector and attenuator are calibrated as a unit to maximize accuracy
What about different response in different regions?
The transfer function of the diode through square-law, transitional and peak detecting regions can be calibrated in modern power meters using CW signals

10. Detector Diode RF Power Sensors – Peak Sensors
What about envelope / pulse modulated signals?
Detects average power accurately, peak <-20 dBm.
Peaks above -20 dBm can not handle modulated signals accurately.
Capacitors charged when peaks occur but decay slowly.
During decay time the detector cannot follow the signal, creating erroneous average power readings.
Solution: Reduce RL and CL to allow the detector track the signal envelope (not so low that carrier bleeds through)

11. Envelope of Modulated Signal
Sensor output is DC or baseband signal representing the input signal’s envelope.
Power meter amplifies and conditions, and linearize the received signal from the sensor.
Calibrated for amplitude and frequency linearity and often temperature stabilization as well.

12. Video bandwidth and modulation defined
Peak Power Solution
Video bandwidth and modulation defined
Frequency range of the power envelope fluctuation, AM component of the modulation only
FM or phase modulation, considered CW. No direct effect on the VBW. Sensitive to only the amplitude of an RF signal, and not to its frequency or phase
Square-law region revisited, isn’t it still a diode detector?
Still nonlinear. Detector output sampled, linearity correction preformed on each sample before signal integration or averaging, hence possible to calculate average and peak power even outside the square-law region of the diode

13. Importance of Video Bandwidth
CW too slow to follow the envelope, measurement error can be in either direction depending upon the signal and detector characteristics.
Not only instantaneous power is wrong, average power of the pulse will be incorrect as well.

14. Amplifier Measurements in a Pulsed World
Pulsed Signals are every where
Radar Signals
Defense
Weather
Automotive
Communication Signals
Wi-Fi MIMO
Bluetooth
Cellular
Amplifiers Design and Development Changing
GaN

15. Pulsed Power Measurements
Pulse width Pulse rise-time
Pulse fall-time Pulse period
Pulse repetition frequency Pulse duty cycle
Pulse off-time Peak power
Pulse “on” power Pulse overshoot (dB or %)
Waveform Average power Top level power (IEEE spec)
Edge delay Edge skew
Bottom level power (IEEE spec)

16. Pulsed Power Measurements
Why Average Power Sensors are not accurate for Pulsed Signals

17. Amplifiers Typical Pulsed Radar

18. GaN Amplifiers GaN Provide Higher Efficiency Smaller Physical Size
Wide Bandwidths
Used for:
Radar
Communications
Issues
Thermal
Linearity Caused by Thermals from Small Signal’s
RF Sensors can be used for Linearity Measurement

19. GaN and Small Signals Create Thermal Issues
Fixed Bias
Envelope Modulation
*Qualcomm Presentation

20. Amplifiers Typical Figures of Merit
Gain- P1
Dynamic Range
Linearity
Bandwidth (5, 10, 100 MHz)
Stability
Rise Time, Overshoot, Droop
Average Power
Peak to Average Power ( Crest Factor )

21. Broadband Amplifiers Demand
Lower Power Consumption
Increased OFDM Video Bandwidths
Device Diversity
Base Stations
Small Cell
Portable Devices
Communications Automotive
Linearity

22. OFDM Signals
Wireless comms market driven by hand-held device data transfer rates
All OFDM signals have high Crest Factor power amplifier requirements
High Crest Factor signals can easily saturate linear amplifiers
Peak Power Meter with statistics is a cost effective tool to measure Crest Factor

23. Linear Testing
Example of clipped OFDM waveform

24. Wideband Signal - Peak and Average Power

25. Wideband Signal

26. Complementary Cumulative Distribution Function CCDF

27. CCDF Input vs. Output of Amplifier with Data

28. Return Loss Measurements Scalar Like Measurements
Measure gain and return loss / reflected power – not just average but peak

29. Noisecom How is Noise Generated Noise Source Capabilities
Frequencies
Levels
Noise Source Applications
Amplifier Performance
Over the Air Testing

30. Defining Noise
AWGN is recognized as a basic noise model which mimics the combined effect of many random processes occurring in nature

31. Noise Generation
Practical AWGN is generated by using a Zener diode in a reverse biased circuit
The selection of quality components and careful biasing provides high performance noise sources

32. Noise Sources Questions
Frequency
10 HZ to 110 GHz
Power Levels
-168 dBm to +20 dBm
Bandwidths
KHz to GHz
Package
Diodes
Modules
Bench Top
Manual / Remote controlled

33. Amplifier & System Performance – Noise Figure Measurement
Products: Noise Modules and Instruments
Function: Generate accurate noise levels with calibrated ENR
Application: Calibrate VNA and spectrum analyzers for reliable, repeatable measurements
Complementary Products:
Spectrum Analyzer, VNA
Measurements:
Noise Figure/Noise Floor

34. EMC Application – Wireless Co-Existence Testing
ANSI C63.27:  Evaluation of Wireless Coexistence
An evaluation process and supporting test methods to quantify the ability of a wireless device to coexist with other wireless services in its intended radio frequency (RF) environments
IEC/EN :2017: Industrial communication networks - Wireless communication networks - Part 2: Coexistence management
AS06066 System
30V/m w/80%AM (54V/m CW) at a 3m test distance from 80MHz to 6GHz.

35. Co-Existence Testing Using Carrier to Noise Generator
Adding C/N to Signal
Yellow is input Signal
Blue is Carrier and Noise floor
manipulated

36. Co-Existence Testing
Two chamber method – One chamber, one antenna method with a second chamber for the companion device
Four test methods
Conducted (wired)
Chamber/Hybrid method (setup shown)
Radiated – anechoic method (semi or fully lined anechoic chamber
Radiated Open Environment method

37. Over the Air Calibration/Verification Testing
Product: Modules and Instruments
Function: Generate accurate noise levels with calibrated ENR
Applications: Calibrate measurement chamber, quantify path loss
Complementary Products: VNA, Spectrum Analyzer, Power Meter, Power Sensor
Measurements: DUT RSSI, Radiated Power, Mapping of Radiated RF Field

38. More Detail for OTA Noise sources for: RF Power Sensor Measurements
Verification of Equipment
Verification of Interconnects
Verification of Antennae
Verification of Chambers
RF Power Sensor Measurements
Return Loss
Complementary Measurements

39. Calibration Popular Equipment Used
Verification of VNA’s and Spectrum Analyzers
Noise source wide Frequency Bandwidth (10Hz to 110GHz)
Wide VBW
Normalize the VNA and Spec A response
Calibrate Cable used for Interconnects
Cables have frequency response
Noise sources connected to cables to test gear
VNA’s and Spec A’s normalized then cable inserted in Path.
Frequency Response can be determined
Loss determined
Noise source is a simple, fast and inexpensive source.

40. More Calibration Antenna Calibration
Transmit and Receive have frequency responses
Using a Noise source connected to Transmit antennae
Receive Antenna connected to Test Equipment
Compare the normalized data to the receive for response
Chamber Calibration and Verification
Noise source can be hooked to Reference Antenna and Transmit to Receive
Provides Repeatable Reference Levels
Traditional Calibration is: slow sweeps, long dwell times
Receivers can be calibrated at a fraction of the time

41. What RF Peak Power Sensors Brings to the Table
Peak Power Sensors can be used for OTA Measurements
Return Loss Measurements of Transmit Antennae
Determines transmit levels into the chamber
Power Levels of Device Under Test
Multiple Sensors can be Synchronized for Accurate composite power
Very fast measurements in real time
Values in Average and Peak Power
Devices under development are OFDM
Can be used in conjunction with Spectrum Analyzers and VNA’s

42. Benefits Review
Noise sources a fraction of the cost of a high frequency generator
Noise sources output is OFDM high Crest Factor
Extreme Wide Video Bandwidth
Can dramatically reduce the time of calibration
Can reduce the cost of calibration system
Power Meters can provide important Crest Factor Information
Can be synchronized for composite power measurements of Peak and Average, Crest Factor
Potential production system

43. Solutions Guides for 5G and mmWave
Principles of Power Measurement Guide
Solutions Guides for 5G and mmWave

44. Support Material OTA Video On Boonton and Noisecom Page
5G Solutions Guide on Noisecom Web Page along with others guides:
Principles of Power Measurement Guide
Boonton Labview Driver available:
Memory buffer Software Lab View based Automated Measurement

45. Wrap Up Thank You Material Support Questions?
Qualcomm – GaN Thermal and Envelope modulation
AR RF/Microwave Instrumentation - Co-Existence Testing Material
R&S – Noise Figure
DVTest – OTA Chamber
National Instruments – Interconnect Verification
The Ohio State and Colorado University - Envelope Modulation
Questions?