Design Of RF Receive Front End Circuit In The UHF RFID Reader

The thesis mainly studies a novel RF front end circuit in the UHF RFID reader. Firstly, it introduces the development and character of the RFID system,the UHF RFID system and the UHF RFID reader; Afterwards, the development and character of the RF front end circuit of the UHF RFID reader are introduced. Then, a novel RF front end circuit with low consumption and high linearity is firstly proposed after reading a lot of papers about UHF RFID system, UHF UFID reader, LNA and mixer with the project supported by the Science and Technology Project of Changsha City (No.K0902012-11).Then, the two unit circuits of the UHF RFID RF front end circuit LNA and mixer are firstly proposed; At last, the layouts of all the circuits are designed with Cadence. The main contents are as follows:1) A novel LNA with low voltage, low consumption, high linearity and frequency adjustable is presented in this paper. The proposed circuit is well capable of eliminating the common mode (CM) signals because of the differential input and output configurations, it improves the linearity by using the 2nd-intermodulation injection structure at the input terminal, and achieves the operating frequency adjustable by using switch capacitor at the output terminal, it realizes the capacitor feature at the output terminal through the conduction and cut-off of the MOS transistor so as to change the value of the capacitor, and makes the frequency adjustable, which makes up the defect that the traditional LNA structure can not be achieved; the working voltage of the proposed LNA is 1.2V, the current of the circuit is low, so it consumes low power consumption,Finally, the circuit is simulated by Cadence with 0.18μm technology in order to verify the efficiency and stability.2) A novel 900 MHz down-mixer with low voltage, low consumption, high linearity and frequency adjustable is presented in this paper. The proposed circuit is well capable of eliminating the common mode (CM) signals because of the differential input and output configurations, the circuit structure is strictly symmetrical, it improved the linearity by using the 2nd-intermodulation injection structure at the input terminal, and eliminated the noise by using dynamic current injection structure at the output terminal. The function of dynamic current injection structure is similar to the structure of transconductance complementary; they are both enhancing the mixer gain by increasing the transconductance, and decreasing the noise so as to eliminate the defect of relatively higher noise figure of the traditional double-balanced Gilbert mixer. On this basis, transconductance of the dynamic current injection structure is increased through "dynamic" control to the switch transistors, in the circuit design, the mobility of the structure is better; At the same time, it maintains high gain; the supply voltage of the circuit is 1.2V, the power consumption is very low; At last, the layout is done and the circuit is simulated by Cadence with 0.18μm technology in order to verify efficiency and stability.3) In this paper, the RF front-end circuit is proposed on the basis of the proposed novel LNA and down-mixer by connecting the two unit circuits. The circuit has high linearity and realizes frequency adjustable, and it contains the characteristics of the proposed mixer of high linearity and low noise, the working voltage of the circuit is 1.2V, so the RF front end circuit has low power consumption and high linearity characteristics, and the circuit is simulated by Cadence with 0.18μm technology in order to verify the efficiency and stability.