Even harmonic quadrature modulator with low vector modulation error and low distortion for microwave digital radio

An even harmonic quadrature modulator (EHQMOD) with a low vector modulation error (VME) and low distortion characteristics is presented for small sized digital radio transmitters in microwave. Relationships between modulation characteristics and circuit parameters in the EHQMOD are described by analytical and experimental approaches. In addition, this paper presents an improved configuration of the EHQMOD for a low VME and low distortion characteristics. Developed X-band EHQMOD with root cosine roll-off shaped /spl pi//4 DQPSK achieved 6% of VME without any adjustable circuits and -11 dBm of output power with -50 dBc of leakage power at an adjacent channel. These experimental results verify the effectiveness of analyzed results. The EHQMOD technique indicated in this paper is effective for future high speed digital communications especially in millimeter wave band.