A single-chip FM modem baseband CMOS LSI for land mobile telephone radio units

A single-chip FM modulator/demodulator (modem) based LSI for the 800-MHz band land mobile radio unit has been developed. This LSI contains both digital and analog function blocks. The digital function block consists of high-speed digital PLL circuits such as a dual modulus prescaler, a programmable counter, and a phase frequency comparator for a 145 MHz direct FM modulator. The analog one consists of transmit and receive analog baseband circuits such as a voice limiter and various kinds of filters. In order to realize a high-speed and low power dissipation LSI, the pulse swallow method and switched capacitor technology have been used in the digital and analog circuits, respectively. The LSI chip is fabricated using a double polysilicon gate CMOS process with an effective channel length of 2 /spl mu/m. The chip size is 5.2 mm/spl times/5.8 mm. The circuit operates with a single voltage supply of 5 V. Typical power dissipation is 90 mW.