The RF Circuit Research And Design Of 915MHz SAW Reader

Radio Frequency Identification technology has been the rapid development and promotion in many areas of modern society, which uses radio signals to finish the automatic identification through space coupling without accessing to target, and can also fast identify multiple RFID tags, in addition,which is easy to use. Thus it has great potential and prospects and will become a basic technology in the future information society. Surface acoustic wave passive tag is a research hotspot in recent years, it hasn't circuit effect at all due to there aren't circuitry and electronic components in the tag, so that it has strong anti- electromagnetic interference ability and high reliability, so it is especially useful for working in a environment of strong electric and strong magnetic. It can also work on the metal or liquid surface, which can't be compared by the conventional electronic tag. It is called SAW RFID to use the surface acoustic wave technology for identification, it is the latest research focus in the world.The paper carries out a depth analysis for a variety of factors which can influence the performance of reader, the use of ADS simulation software conduct a system design and simulation for the front-end RF circuits in the SAW reader, including a complete design of the receiver, the transmitter and the isolation circuit. The reader's center frequency is 915MHz, the sensitivity is -84dBm, and the maximum identification distance is 8.49m. Specific works includes the following:(1)An improved IF receiver scheme is put forward to overcome the DC drift and low frequency noise of the single quadrature zero IF receiver, then basing on the program, it creates a complete receiving and transmitting RF circuit model of SAW reader in the ADS environment. And the use of ADS carries out the harmonic balance simulation, envelope simulation, bit error rate simulation, the gain budget simulation for the reader model.(2)The low noise amplifier is a key component in the front-end RF circuits of the reader, it is designed by ADS software in the paper, it is produced and tested, and the good test results are acquired. In addition, it also designs a Butterworth BPF whose center frequency is 915MHz.(3)It designs a 915MHz local oscillator through taking advantage of phase-locked loop technology.(4)It has selected the variety of chips which are required in the reader through researching market, and it analyzes their relevant parameters and characteristic. Then both the specific RF circuit implementation scheme and the circuit diagram of active devices also are given.The paper has finished the theoretical design and simulation of the RFID circuits and acquired the stage achievement of project. The design exerts great directive significance in the next step such as producing the real reader as well as designing the RF receiver chip. At last, the paper estimates some problems and limitations which will be faced for the project, and makes an outlook for the RF chip industry in our country.