The 5 GHz band was recently exploited globally for multimedia wireless access systems with transmission rates of many tens of Mb/s. The Japanese version, multimedia mobile access communication system (MMAC) includes wireless LAN (W-LAN) based on IEEE 802.11 standard and high-speed public wireless access systems. The 3 to 5 GHz Si-bipolar quadrature modulator and demodulator use a wideband frequency-doubling 90/spl deg/ phase shifter with self-correction of phase errors from the original 90/spl deg/ phase-shift network. At half the carrier frequency. High image rejection, and small phase and amplitude errors are obtained without trimming or tuning.
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