Differential Colpitts VCO for Enhancing Transceiver Performance in Specified UHF Mobile RFID Environment Conditions

In this paper, we introduce a differential Colpitts voltage-controlled oscillator (VCO), performing a signal oscillation with low phase noise. The proposed VCO is a part of our RF integrated circuit (IC) transceiver design project; some transceiver components are also introduced. VCO performance is verified both in simulation and practical measurement using the proposed RF IC transceiver, communicating with a commercial passive UHF RF identification tag in a small-scale area. The measured phase-noise level at the frequency divider output port is nearly -106 and -135 dBc/Hz at 40-kHz and 1-MHz offset, respectively. A good figure-of-merit of 1.93 dB is obtained. The paper also highlights some important components [e.g., phase-locked loop, low-noise amplifier, dc offset canceller (DCOC)], and their performance. We configure the reader system, which consists of the proposed transceiver on board and a patch antenna, to use frequency hopping in 15 channels at a 200-kHz interval. The transceiver power amplifier supports 22 dBm of power. Configuring the interrogation range to 1 m, we measure received backscatters at the DCOC output port (the regenerated tag data level is 8 mV). Finally, we verify satisfactory states of the tag data process in the receiver.