Broadband 20-$\Omega$ 20-W Load Suitable for Characterization of Switch-Mode Amplifiers

This paper reports on a broadband dc ground isolated 20-Ω absorber for powers of up to 20 W. The realized absorber achieves reflections (referenced to 20 Ω) below -10 dB over almost two frequency decades from less than 50 MHz to 2 GHz. It can be used as load resistor in the characterization of power amplifiers, particularly switch-mode ones, where broadband non-50-Ω loads are required for measurement purposes. An additional advantage is that no bias-T is needed with this solution. This reduces measurement uncertainties due to the parasitics of the bias-T. Using the distributed concept offers a generic technique to realize such loads and also for other impedance values and other applications.