Using RF Power Sensors and Noise Sources for EMI/EMC/OTA November 15, 2018 Matthew Diessner Director of Business Development mdiessner@wtcom.com 201-919-7467

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

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?

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

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

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

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

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.

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

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)

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.

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

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.

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

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)

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

Amplifiers Typical Pulsed Radar

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

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

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 )

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

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

Linear Testing Example of clipped OFDM waveform

Wideband Signal - Peak and Average Power

Wideband Signal

Complementary Cumulative Distribution Function CCDF

CCDF Input vs. Output of Amplifier with Data

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

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

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

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

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

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

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 62657-2:2017: 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.

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

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

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

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

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.

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

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

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

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

Support Material OTA Video On Boonton and Noisecom Page http://noisecom.com/resource-library/videos/over-the-air-testing-5g-and-mmwave 5G Solutions Guide on Noisecom Web Page along with others guides: http://noisecom.com/resource-library?brand=Noisecom&go=solutions_guide Principles of Power Measurement Guide https://boonton.com/forms/principles-of-power-measurement-form Boonton Labview Driver available: http://www.boonton.com/service-and-support/software-and-drivers/rtp5000-lab-view-driver Memory buffer Software Lab View based Automated Measurement

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?