A direct conversion receiver utilizing a novel FSK demodulator and a low-power-consumption quadrature mixer

Two novel technologies of direct conversion are introduced. One is an FSK demodulator based on a new architecture, and the other is a quadrature mixer for direct conversion. The FSK demodulator is composed of relative 90 degrees phase shifters and frequency multipliers suitable for digital circuit implementation, and it has shown a wide allowance for offsets of the local frequency. In designing the quadrature mixer IC, structural and numerical optimization was carried out for low power consumption. The demodulator and the quadrature mixer, including the surrounding circuits, have been integrated. In order to realize smaller size and advanced performance, the authors adopt appropriate silicon processes for each of these two ICs. The FSK direct conversion radio data receiver with a bit rate of 1200 b/s developed utilizing the above ICs has achieved excellent performance, as expected.<>