The Design of RF Receiver for Frequency Spectrum Sensing in Cognitive Radios

In this paper, a new architecture of RF receivers in the cognitive radios is proposed for sensing the spectral environment. The receiver has two mixer stages and a high intermediate frequency (IF) for up/down dual-converting signal frequency. In order to select the channels in UHF (470-870 MHz) band in TV broadcast, the range of frequency points in the first local oscillator is from 1640 MHz to 2040 MHz with a space of 8 MHz between two adjacent frequency points. The IF is 1166 MHz. The second local oscillator frequency is also 1166 MHz for down-converting the IF to baseband. The simulated results of the receiver show that the noise figure (NF) of the receiver is 6.4 dB, and the conversion gain is about 82.5 dB.