A 0.9–2.6 GHz Cognitive Radio Receiver With Spread Spectrum Frequency Synthesizer for Spectrum Sensing

In this paper, 0.9–2.6 GHz receiver with spread spectrum frequency synthesizer is proposed for spectrum sensing cognitive radio system. With the presence of spread spectrum window generated by local synthesizer, the bandwidth of low-pass filter for spectrum sensing can be fixed, which alleviates the complexity of energy detection block, making it easily embedded into a transceiver chip. The proposed coherent sampling quickens energy detection under negative signal-to-noise ratio. The proposed direct conversion receiver with wideband interference rejection includes a low noise amplifier and mixer, which achieves a NF of 5 dB and gain of 30 dB over the entire bandwidth with 20 mW power consumption. The ultra-wideband voltage controlled oscillator with loss compensation is designed to cover 0.9–2.6 GHz. A prototype chip has been fabricated in
$0.18~\mu \text{m}$
CMOS technology consuming 130 mW in sensing mode with 1.8 V power supply. The total chip area including pads is approximately 2.75 mm
²
. The proposed CR receiver achieves wide operation frequency range from 900 MHz to 2.6 GHz with minimum detection sensitivity of −93.2 dBm and adjustable detection window of 35~70 MHz.