An Experimental MM-Wave Path Length Modulator

The availability of mm-wave silicon I M P A T T diodes 1 with several hundred milliwatts of output power makes practical the construction of reliable all-solid-state mm-wave communication systems. Several candidate schemes have been proposed. 2-9 They can be divided into two broad categories, depending on whether the modulation is achieved within the oscillator circuit or separately. The varactor tuned oscillator and the direct deviator are examples of achieving the modulation within the oscillator. A method by which the path length of the mm-wave is modulated by a P I N diode switch is described in this paper and is an example of externally modulating a fixed-frequency oscillator. It represents the best compromise with respect to the required driving power, insertion loss, speed, and power handling capability at mm-wave frequencies. In particular, we have concentrated on two-level Path Length Switched Differentially Coherent Phase Shift Keying, in short, PLS-DCPSK. This paper describes the development of an experimental mm-wave PLS-DCPSK transmitter in the 50 ~ 60-GHz range. The model is 2917