Twisted Inductor VCO for Supressing On-chip Interferences

Fully-symmetrical on-chip twisted inductor VCO has been studied to suppress interferences from on-chip driver amplifier in transmitter chain of integrated ETC transceivers and compared with conventional inductor VCO. Similar transceiver chips with either conventional inductor VCO or twisted inductor VCO are fabricated and are measured and the transmitter spectra of ASK modulated signals are measured. The ASK modulated 5.8 GHz transmission spectrum of the transceiver chip with the conventional inductor VCO shows USB/LSB asymmetry of 2.8 dB however, that of the transceiver chip with the twisted inductor VCO is perfectly balanced. This result shows that the twisted inductor VCO has a significant advantage in suppressing interference of integrated transceiver chip. The phase noise of 1 MHz offset from 5.8 GHz carrier, after frequency doublers, is -117 dBc/Hz, the current consumption is 4.1 mA, and FOM is 183 dB.