Shyam S. Somayajula

A CMOS IF transceiver with reduced analog complexity

Signal processing techniques are used to minimize the analog complexity in an intermediate-frequency (IF) transceiver. The receiver digitizes the IF signal directly by subsampling and complex bandpass delta-sigma modulation. A new loop filter is proposed for use in the complex delta-sigma. Digital demodulation and filtering are then used to extract the baseband information. The transmit section converts baseband to IF through an all-digital signal path. A bandpass delta-sigma modulator quantizes the digital IF signal to 1 bit in order to simplify the IF output digital-to-analog converter/driver. The output driver provides analog finite impulse response filtering for quantization noise.

CMOS IF transceiver for narrowband PCS

Integrated IF transceivers can be used to reduce the size and power consumption of portable radios. The IF transceiver described is designed for narrowband PCS applications, such as two-way paging. This design uses novel signal processing techniques in order to minimize power consumption and analog complexity. The receive section converts a 21.4 MHz IF signal (8 kHz BW) to a digital complex baseband signal. The transmit section accepts a digital complex baseband signal and outputs a 60.4 MHz IF signal (8 kHz BW). The IF transceiver also integrates several functions to control external RF circuitry. These functions include DACs for frequency control of the crystal reference and power control of the transmit PA, a temperature sensor, a general purpose ADC, and general purpose programmable digital inputs and outputs.