A Ku-Band Hybrid-Coupled 4-Phase Modulator in M.I.C. Technology

A hybrid-coupled 4-phase P.I.N. diode modulator can operate at frequencies as high as the upper Ku-band even on 25 mil alumina. Investigated are the theoretical constraints under which hybrid-coupled phase modulators, may be connected in series. It is shown, that large output reflexion coefficients are admissible for the series connection of such modulators. The theoretical results have been verified by measurements, which showed that with an optimized design, a single modulator will accept any load with 20 % reflexion coefficient and produce less than ± 2° phase error without using isolators; even at 50 % load reflexion coefficient it will not produce inadmissible large phase errors. With fast enough switching diodes, the 4-phase modulator will accept bit rates in excess of 200 Mbit/s. Excepting the P.I.N. diode chips, this modulator, including the complete bias networks, is manufactured photolithographically, thus allowing a economical production of the device.