CMOS Design > Analog Cell Design

Frequency Converter

Goal : To shift a high frequency in lower frequency

In many situations for radio frequency receivers, there is a need for shifting a high frequency input waveform into a low frequency waveform. The operation is called down conversion. In frequency domain, it consists in shifting a high frequency information contained in frequency fin to a lower frequency fout, as illustrated in the figure.

One very simple solution consists in using a transmission gate with a very accurate tuning of the gate clock. As an illustration, we use a 1.900 GHz sinusoidal wave, and a 1.818 Ghz sampling signal (550 ps period). The expected output frequency is therefore 1.900-1.818=0.082 GHz, that is 82MHz. The layout of the sample circuit is a simple transmission gate with an RC filter.

	Simple solution : Transmission gate followed by a RC filter

CMOS Design > Analog Cell Design > Frequency Converter