Visual observation of internal signal transmissions in a millimeter-wave amplifier module

The internal signal transmissions in a millimeter-wave module were visually observed for the first time. The module contains a 2-35 GHz GaAs travelling wave amplifier chip and microstrip lines on alumina substrates. In the frequency range of 10-35 GHz, visual observation was achieved using a live electrooptic imaging camera based on the optical magnification method. It was successfully demonstrated that the voltage-dependent performance of the amplifier and symptoms of parasitic cavity resonance effect were visualized.