The Research On RF Power Amplifier

Compared to LF and HF RFID, UHF RFID has the advantages of long distance, good continuity, high reading card speed and especially adapt to fast-moving objects. But the reader in UHF RFID system is still in the stage of research, the RF power amplifier (RFPA) is the core component in the reader, it's property has important influence on transmission distance and stability of the reader. The UHF RFID reader's property determines it's RFPA must have higher requirement in the design.In this thesis a three stage RFPA is designed based on the simulation in ADS, which working from 902 MHz to 928MHz, it's center frequency is 915MHz and the gain at 915MHz is up to 46dB, the VSWR is below 1.4. The relevant theories, main performance index, classification and design methods of RFPA were introduced firstly, Secondly each stage RFPA is designed according to the design steps: determine design indexs, device selection and simulation optimization, the gain and other performance index are analyzed using S-parameters. The RFPA is comprised by Pre-stage, Driver stage and Final stage. Each stage is designed according to the reader's performance requirements. The Pre-stage amplifier has critical influence in linearity of the whole RFPA, therefore a highest linearity design method was adopted in the design. The Driver stage amplifier requires the highest gain while keeping the linearity, the small signal s-parameters design method was adopted in the design. The Final stage realized flat power gain in the working frequency band, so a balanced power amplifier comprised by ALM-32120 and 1E1304-3 was adopted in the design. The three stage amplifiers were connected by -4dBÏ€attenuator and 3dB quadrature coupler. The simulation results At last, Altium Designer 9.0 was used in the PCB layout design according to PCB layout , lining and EMC principle.