CMOS Fractional-N Frequency Synthesizer for UHF RFID Reader Applications With Transformer-Based ISF Manipulation VCO

This brief presents the CMOS fractional-N frequency synthesizer for UHF RFID reader applications. With stringent phase noise (PN) specifications for UHF RFID transceiver, our proposed synthesizer is designed to have a narrow loop bandwidth and 2nd-order loop filter as the optimum solution paired with low noise VCO. Then, we propose the transformer-based impulse sensitivity function (ISF) manipulating VCO that supports the target PN of the frequency synthesizer, albeit with large pass-band characteristic. Compared to conventional ISF manipulating VCO, our proposed solution improves the PN by 11.3 and 14.7 dB at 10 kHz and 1 MHz offset frequencies, respectively. Figure of merit (FOM) is also superior to conventional one by 7.4 and 10.9 dB at aforementioned offset frequencies. The frequency synthesizer is implemented in a 55nm CMOS technology as a part of the UHF RFID transmitter and consumes 38.4 mW power with 0.413 mm(2) active area. With comparison to the state-of-the-art frequency synthesizer at sub-6GHz operating frequency, only our solution satisfies the target PN for EPC global standard and various local regulations across the entire UHF RFID operating frequency range.

Automated summary

This brief introduces a CMOS fractional-N frequency synthesizer designed for UHF RFID reader applications. The synthesizer is designed with a narrow loop bandwidth and a 2nd-order loop filter, paired with a low noise VCO, to meet the stringent phase noise specifications of UHF RFID transceivers. A transformer-based impulse sensitivity function (ISF) manipulating VCO is proposed to support the target PN of the frequency synthesizer, with large pass-band characteristics. Compared to conventional ISF manipulating VCOs, the proposed solution improves PN and has superior figure of merit (FOM). The frequency synthesizer is implemented in a 55nm CMOS technology as part of the UHF RFID transmitter, satisfying the PN requirements of EPC global standard and various local regulations across the UHF RFID operating frequency range.