Novel Quasi-Hermetic Photodiode Module Featuring an E-Band Rectangular Waveguide (WR-12) Output

A quasi-hermetic photodiode module featuring a WR-12 rectangular waveguide (RW) output has been developed for operation in the E-band. The module makes use of a grounded coplanar-waveguide-to-rectangular-waveguide transition implemented on a Rogers RT/duroid 5880 laminate that does not require any mechanical modifications of the RW. Simulations show that the transition has excellent radio frequency (RF) characteristics (return loss larger than 30 dB, insertion loss smaller than 2 dB, maximum group delay deviation smaller than 1 ps). Measurements confirm the simulated results and highlight the importance of via-holes to reduce the overall loss. The maximum output power delivered by the module, at a DC photocurrent of 10 mA, is -12.5dBm. At 73 GHz, the 1-dB compression point is found to be at a photocurrent of ~ 9mA, with an RF output power of ~ -13.5dBm . The measured output power has less than 1 dB ripple in the frequency range of interest.