MIXED TECHNOLOGY MEMS/BICMOS LC BANDPASS SIGMA-DELTA FOR DIRECT RF SAMPLING

An improved sigma-delta modulator is disclosed. The sigma-delta modulator (100) utilizes Micro Electro Mechanical System (MEMS) technology coupled with on-chip LC networks (110, 118). MEMS switches are used to switch capacitors and inductors in and out of the network to alter the center frequency and tuning range of the sigma-delta modualtor (100), thus eliminating active components in each LC network (110,118). Furthermore, the use of MEMS switches improves the Q of each LC network (110,118) relative to previous on-chip sigma-delta modualtor designs. The increased Q of each LC network (110,118) reduces or eliminates the need for active Q-enhancement circuitry and improves the inherent filter shape within the loop of the sigma-delta modulator (100). In addition, the distortion of active compoenmtns with the loops (146,146', 148, 148') of the sigma-delta modulator (100) also is improved. The addition of a decimator 252 to the chip presents a complete single chip LC sigma-delta analog-to-digital converter 250.