RF Component & Device Test Series: RF Power Amplifier Testing
Power Amplifiers (PAs) are essential components in most RF, microwave, and millimeter-wave sensing, communications, electronic warfare (EW), and directed energy weapons. PAs are used within a signal chain to add significant gain to the signal, typically within the transmit signal chain near the RF antenna. Many applications require extreme signal power levels at the antenna ports to reach the necessary range or throughput levels. To address this, we offer high power amplifiers in addition to a line of medium power amps. Given the large signal power levels of PAs and the importance of efficiency and linearity at these power levels, there are several test techniques and methods specifically dedicated to effectively characterizing and testing PA performance at the device and system level.
Important Power Amplifier Performance Parameters
- Operational bandwidth/frequency range
- Small signal gain
- Efficiency/power added efficiency (PAE)
- Gain flatness
- Input power
- Noise figure
- Input voltage standing wave ratio (VSWR)
- Stability
- Input and output impedance
- Output 1dB compression point (P1dB)
- Output third-order intercept point (IP3)
- Saturation Power (Psat)
- Peak power handling (pulsed operation)
- Reverse isolation
- Harmonics
- Spurious suppression
- Operating temperature range and thermal management system/requirements
- Supply voltage & bias conditions
Hence, power amplifiers require a substantial amount of testing, beyond that of many other RF devices. Power amplifiers are typically tested in a small signal sense, for linearity, and under varying load impedances over wide operating parameters. Most of this testing is done during characterization and quality control testing, but power amplifiers must often also be regularly testing to ensure they still meet specification over certain intervals depending on how they are operated. The reason for this is that the power levels and thermal dynamics of operating a power amplifier lead to high sustained temperatures while being energized, which can result in rapid degradation of the amplifier materials and structures.
Many of the small signal parameters, such as gain, bandwidth, gain flatness, VSWR, impedances, etc. can be tested using traditional VNA and S-parameter measurements. However, many of the nonlinear aspects of power amplifiers require additional measurements and techniques, possibly including X-parameters as an extension of S-parameters to account for nonlinearity. Load-pull testing is also performed on power amplifiers to better determine the output behavior of the power amplifier facing various load conditions. Harmonic and spurious testing using signal generators and power meters/spectrum analyzers (often protected by couplers and attenuators) is also often performed. To better determine pulsed power performance of a power amplifier, peak power meters may be used with adequate bandwidth to capture the signal envelope of amplifiers output.
Learn more about Fairview Microwave’s line of power amplifiers (PAs) and amplifier test equipment/accessories:
