| RF power amplifier is a very important circuit in the wireless base stations, which is used at theend of the base station transmitter in a wireless communication system to connect the antenna soas to send high-power radio signals. Meanwhile, the power amplifier is one of the largest circuitmodules of the power consumption in the base station, whose efficiency directly affects theoverall energy consumption of the base station. The third-generation wireless communicationsystems proposed higher requirements for high linearity of the wireless signal. The linearity of thepower amplifier directly impacts on the performance of the base station transmitter, andconsequently determines the communication quality of the users. Under the background of theincreasingly crowded wireless spectrum and global advocacy of green communication, theefficiency enhancement and linearization technologies for power amplifiers have become the keytechnologies of wireless communication base stations.This thesis firstly describes the classification and performance indexes of the RF poweramplifier, and summarizes the mature technologies to improve the linearity and efficiency of RFpower amplifier. Then, the nonlinear models of the RF power transistor are briefly reviewed. Twocommonly used matching methods (lumped matching and distributed matching) are analyzed, aswell as the stability theory of power amplifiers, so as to establish the theoretical basis for theactual high-power amplifier design.With the power amplifier theory and Freescale’s LDMOS power transistor, two drives poweramplifiers operate at 1.96GHz and 2.14GHz respectively are realized by the bias circuit, the inputand output matching network design and optimization, PCB producing, testing and debugging.The output 1 dB compression power (P1dB) of the two power amplifiers are 35.84dBm and40.53dBm, respectively. Meanwhile, the impact of the defect ground structure (DGS) on thepower amplifier performance is also studied. The two different metal ground plane etching DGSstructure (the Top-DGS etched on the both front sides of the microstrip line and the Bottom-DGSetched on the back of the microstrip line) are analyzed by electromagnetic field simulation. Themeasured results show that the DGS structure is able to suppress the second harmonic output, andthe Bottom-DGS has better suppression ability. However, the DGS structure changes thecharacteristic impedance of the microstrip line, the impedance matching, the power-addedefficiency (PAE) and output power of the power amplifier.Finally, this thesis designed a balance high-power amplifier which operates at 2.14 GHz,through the combination of individually designed a 100 W single amplifier, 3 dB hybrid couplerand driver amplifier. The measured P1dBreaches 52.29 dBm, and the corresponding PAE is about45%, the third-order intermodulation coefficient (IMD3) is about -19 dBc, the measured adjacentchannel power ratio (ACPR) of the WCDMA signal is about -21 dBc.In summary, this thesis has completed the design of a balanced amplifier circuit module. Themeasured results show that the output power and gain are high enough for the application inWCDMA base stations. The linearity of the power amplifer can be effectively improved bylinearization technologies such as analog predistortion, so as to meet the needs of actualapplications... |
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