VLSI-implemented high speed digital burst modem applications for satellite video TDMA and wireless LAN

High speed (60 Mb/s) QPSK/OQPSK burst modem Very Large Scale Integrated Circuits (VLSICs), which are greatly useful for radio units to be compact, economical and maintenance-free, are introduced. These VLSICs enable modems to eliminate the analog devices such as mixers required for baseband modulation and zero-IF conversion in demodulation, an analog voltage controlled oscillator (VCO) for bit timing recovery and a voltage controlled attenuator for automatic gain control (AGC). In addition to the full-digital implementation, the demodulator VLSIC achieves fast carrier-acquisition for burst mode operation by employing a reverse-modulation carrier recovery scheme capable of operating for OQPSK signals, and fast clock-acquisition by using a bit-timing recovery scheme with bit-timing estimation and interpolation coupled with a pulse-shaping filter. Results of experiment on the assumption of a video time division multiple access (TDMA) system show that the developed VLSICs perform well at the high speed (60 Mb/s) and with the short preamble words (80 symbols).