Unique challenges arise when measuring and characterizing the pulsed RF signals used in radar applications. With pulsed radar signals turned on, the amount of power transmitted by a system can range from kilowatts to megawatts. Such high-power pulsing, however, may stress power amplifiers (PAs). Thus, it’s best practice to thoroughly test and evaluate a PA’s behavior. In the application note, “GaN or GaAs, TWT or Klystron—Testing High Power Amplifiers for RADAR Signals using Peak Power Meters,” Boonton Electronics explains why peak power meters are a necessity when characterizing the behavior of pulsed PAs used in radar systems.
The application note begins with an overview of PAs for radar applications. It then explains that the most critical analysis of the pulsed RF signal occurs in the time domain. Because peak power meters measure, analyze, and display the power envelope of an RF signal in the time domain, they are considered an essential tool for measuring the PAs used in pulsed radar applications. To provide further insight, the app note presents a simplified block diagram of a peak power meter. Each of its stages is then explained in detail.
In addition, the note describes two different setups, each with the ability to make pulsed radar measurements. The first setup is used to test a modulating amplifier. While the amplifier’s input is a continuous-wave (CW) signal, the output is pulsed because of a gating signal that modulates the incoming signal. The second setup can be used to test an amplifier that has a pulsed input with no gating signal. It uses three peak power meters and a directional coupler to make scalar-like gain and return loss measurements.
The document describes the calculations required to compute gain and return loss when using the second setup. Subsequently, three waveforms were measured: the input, reflected, and output waveforms. The application note concludes with a description of some of Boonton’s peak power measurement solutions.
Boonton Electronics, 25 Eastmans Rd., Parsippany, NJ 07054; (973) 386-9696