Integrated CMOS wide tuning range integer-N frequency synthesiser for spectrum monitoring functions in cognitive radio systems

An integrated frequency synthesiser is designed and implemented in standard 130 nm complementary metal-oxide semiconductor (CMOS) technology for spectrum monitoring receiver function needed in an associated cognitive radio system. This function demands very wide continuous tuning range albeit with only moderate phase noise performance, although low-power consumption and small die area are high priorities. To meet these unusual specifications, a ring oscillator is used as the frequency source, and a novel high-speed low-power integer-N programmable divider is developed to achieve the tuning range. Using a 25 MHz reference frequency, the ring oscillator-based synthesiser tunes continuously from 5 to 7.3 GHz with 100 MHz steps, maintaining the measured phase noise and reference spur levels below 80.5 dBc/Hz at any frequency offset between 100 kHz and 100 MHz for all output frequencies. The power consumption of the complete frequency synthesiser (excluding the output buffer and the reference crystal oscillator) is 9.98 mW from a 1.2 V supply.