High-power photonic microwave generation at K- and Ka-bands using a uni-traveling-carrier photodiode

A K- to Ka-band photonic microwave generator (PMG) consisting of a uni-traveling-carrier photodiode (UTC-PD) and a monolithically integrated bias circuit utilizing a 1/4-wavelength coplanar waveguide is presented. The device exhibits a high-saturation-output power of +14 dBm at 26 GHz for a bias voltage of -4 V. The output power is almost constant within a frequency range from 23 to 29 GHz. The 3-dB down bandwidth of the generator is as wide as 20 GHz, which is in good agreement with the circuit model calculation. Two types of devices, one with and one without a dc-cut capacitor, exhibit almost the same input-output characteristics. The device for the operation in the 38-GHz band is also fabricated, and it shows a maximum millimeter-wave (mm-wave) output power of +9 dBm. The PMG is suitable for the broad-band high-output fiber-radio applications.