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RF & Wireless Figure 8:

RF & Wireless Figure 8: The screenshot captures the input, output and reflected waveforms of the pulsed RF signal. Blue trace is output of the DUT1 (note overshoot and ringing), purple trace is the reflect signal from the input port of the load DUT2 path. The losses that need to be calibrated out in the test set-up of Figure 7 and calculations required to compute gain and return loss are provided below. L1: Loss from Signal Generator output to the FWD port of the directional coupler. L2: Loss from Signal Generator output to the power amplifier input. L3: Loss from amplifier output to the 40 dB attenuator output. L4: Loss from amplifier input into the REV port of the directional coupler. Once the losses are measured, input, output and reflected power measurements can be made: P1: Power reading at FWD port of the directional coupler. P2: Power measured at the 40 dB attenuator output. P3: Power measured at REV port of the directional coupler. PA input power = P1+L1-L2 PA output power = P2+L3 PA input reflected power = P3+L4 All Boonton peak power meters are capable of adding an offset to Figure 9: Droop Measurement using RTP5318 Real-Time Peak Power Sensors. Blue vertical lines 1 and 2 are markers placed for automated marker measurements. Yellow dashed horizontal lines are reference lines. Automated Pulse measurements are computed automatically based on pulse definition irrespective of marker or reference line placements the measurements, so the math above can be done by the meter once the losses are measured and entered to each channel as an offset. The input, output and reflected power measurements can be used to compute gain (S21) and input return loss (S11). PA Gain (dB) = PA output power (dBm) - PA input power (dBm) PA input return loss (dB) = PA input power (dBm) - PA input reflected power (dBm) The 4500C can perform these measurements in time domain using waveform math. It is important to note that in both test set-ups, Figure 6 and Figure 7, the directional couplers need to have excellent directivity in order to make accurate power measurements, especially for return loss calculations. Unused ports of the couplers must be terminated with 50 ohms during measurements. Measurements Figure 8 shows three waveforms measured using the test set-up in Figure 7 using the RTP5000 Series Real-Time Peak Power Sensors. The input waveform is displayed on CH1, reflected waveform on CH3 and the output on CH2. Note that automated measurements performed on all three channels are displayed to the left of the trace display window. The measurements can be transferred to a spreadsheet to perform the necessary gain and return loss calculations, as well as other parameters of interest. In an automated test environment, the same measurements can be accessed through remote programming to perform gain and return loss computations as well. Droop measurement capabilities are shown in Figure 9 using the Boonton RTP5318 Real-Time Peak Power Sensor. Power droop can be measured either using the automated pulse measurements or using automated marker measurements as well as horizontal markers. The automated marker measurements can display the droop placing markers at 70 hf-praxis 12/2018

RF & Wireless Figure 10: The 4500C Figure 11: RTP5000 Series Real-Time Peak Power Sensor the desired points on the waveform and using MkRatio. Alternatively, reference lines can be placed on the vertical axis at the desired high and low points of the pulse to measure the droop. Automated Pulse measurements are computed automatically based on pulse definition irrespective of marker or reference line placements. Conclusion VED based amplifiers have dominated the PAs used in the aviation and warfare radar systems for the past seven decades. However, new semiconductor based SSPAs, have made inroads to various radar applications, especially GaN based ones. Regardless of technology used in the radar PA, high resolution highly accurate time domain power measurements are critical to understand the amplifier performance and behavior. Peak power meters are an essential measurement tool for time domain power analysis to test radar power amplifiers for R&D, quality, manufacturing, field support and system calibration. Boonton Peak Power Meter Solutions The 4500C (Firure 10) is highest performing benchtop peak power analyzer. It is the instrument of choice for capturing, displaying, analyzing and characterizing RF power in both the time and statistical domains. The 4500C offers best-in-class time resolution, wider measurement and trigger ranges, the ability to measure the narrowest pulses at higher pulse repetition frequencies over orders of magnitude longer time periods versus the closest alternative all in a form factor that is half as tall and half the weight. The 4540 series combines a peak power meter, a CW power meter and a voltage meter, into a single 2U, half-rack instrument. It features a wide measurement range and rise time of less than 7 ns. 200 ps time resolution provides great detail for signal waveform analysis. It is ideal for capturing, displaying and analyzing RF power in time and statistical domains. 4540 meters are used widely by high power amplifier manufacturers in R&D and manufacturing test racks. The RTP5000 Series Real-Time Peak Power Sensors (Figure 11) deliver benchtop performance in an USB form factor. Powered by Real Time Power Processing, the sensor is able to make 100,000 triggered measurements per second virtually no gaps in signal acquisition and zero measurement latency - making it ideal for capturing high PRI/ PRR/PRF radar signals without missing a pulse or glitch events. Industry leading 3 ns risetime is meant to handle the most challenging radar signals. 195 MHz video bandwidth makes it ideal for making time gated power and crest factor measurements for broadband communication signals like 802.11ac WLAN, LTE, LTE-A and 5G. The solutions above are ideal for design, verification, and troubleshooting of pulsed and noise-like signals used in commercial and military radar, electronic warfare (EW), wireless communications (e.g., LTE, LTE-A, and 5G), and consumer electronics (WLAN), as well as education and research applications. References [1] RF Power Measurement Reference Guide, www.boonton.com/resource-library/powermeasurement-reference-guide [2] Importance of peak power measurements for radar systems, www.boonton.com/resourcelibrary/articles/the-importance- of-peak-power-measurements- for-radar-systems [3] Radar Testing, www.boonton.com/resource-library/application-briefs/radar-testing [4] Boonton 4540 RF Power Meter Application in a Transponder Type Pulsed Radar System by Michael Mallo, Rockee Zhang and Andrew Huston of Radar Innovations Laboratory, The University of Oklahoma, www.boonton.com/applications/ radar/4540-pulsed-radar [5] What Real Time Power Processing means – 100,000 triggered measurements/second, www.boonton.com/resourcelibrary/articles/real-time-usbpower-sensor [6] Characterizing radar interference immunity, www.boonton. com/resource-library/articles/ characterizing-radar [7] What trigger fidelity & high resolution timebase mean for radar, www.boonton.com/ resource-library/articles/4540- article [8] Application Note on definitions of automated pulse and marker measurements, www. boonton.com/applications/radar/ numerical-parameters-analysisof-boonton-4540-peak-powermeter [9] Advanced Trigger Capabilities of Peak Power Meters, www.boonton.com/applications/ communications/4500b-advanced-trigger-capabilities Videos on capabilities of Boonton peak power meters for radar and communications applications: [10] Why replace crystal detector with a peak power meter for radar, www.boonton.com/ resource-library/applicationbriefs/crystal-detector-sellsheet www.boonton.com/resourcelibrary?brand=Boonton&go= videos hf-praxis 12/2018 71