Combining prefiltering and predistortion in a high power direct PSK modulator

Predistortion linearizes a high-power direct-PSK (phase-shift keying) modulator. A digital method of combining the filtering and predistortion for the modulator is proposed. In particular, a design outline of a microwave circuit and a versatile digital memory-based method of combining prefiltering and predistortion are given. It is shown that a microwave circuit represented by the branchline hybrid, transformation network, p-i-n diodes, and baseband-RF isolation can be integrated with the compact baseband digital memory circuit consisting of shift register, PROM (programmable read-only memory) smoothing filter, and driver using the state-of-the-art MMIC (monolithic microwave integrated circuit) techniques. The technique can be used in the design of transmission-type PSK and FSK (frequency-shift keying) modulators.<>