Research And Design Of Quadrature Modulator And Voltage Controlled Oscillator For UHF RFID Readers

Compared to conventional magnetic card technologies, RFIDs are much more suitable for harshconditions. The UHF RFID has the features of reading several labels at one time, strongpenetrability, reading and writing repeatedly, large amount of memory, low cost of passive digitallabels, small volume, using conveniently and long lifetime as well. The widely use of UHF RFIDhas promoted the research and development of the chips for UHF RFID readers, which has got bigattention by academia and industry.Based on the ISO18000-6Type C protocol, the specific requests on the entire system of UHFRFID readers have been analyzed in this thesis. The solution of the entire system and transmitterstructure has been proposed after comparing several common system structures. The key RFfront-end circuits including a QVCO and a quadrature modulator have been designed. Standard0.18μm RF CMOS process has been used for simulation, layout, post-simulation and measurement.Two types of QVCOs are designed: one is composed of a frequency doubling VCO and afrequency divider; the other is composed two coupled VCOs. The former uses the switchedcapacitor array, which enlarges the frequency band range and reduces phase noise; the latter mainlyuses the splitting switched biasing and the capacity coupling technique, which has better phasenoise and good phase error. The former chip test results show that tuning frequency between1.59GHz to2.37GHz, the phase noise is-114.7dBc/Hz@1MHz; the latter achieves a frequencytuning range from896.5MHz to1.068GHz,the phase noise is-113dBc/Hz@1MHz, which meetsthe system requests.Quadrature modulator has been designed based on the entire system requirement of thefront-end, including an I/Q up mixer and a driver amplifier. The designed quadrature modulator iscomposed of the transconductance stage, the switch stage, the output load, the current injectionstage and the tail current source. The DA can realize seven-level gain adjustable, to control thetransmitting power of signal flexibly. The post-simulation tells that I/Q up mixer circuit can realizethree kinds of modulation including DSB-ASK, SSB-ASK and PR-ASK, the noise of which is20.98dB, the compression point of1dB output is4.85dBm and the gain is4dB. The DA gain is upto7.8dB, the noise factor is18dB, and the compression point of1dB output is4.93dBm. The bothmeet the design requirements.