A Broadband Power Amplifier With Multifrequency Impedance Matching

This letter proposes a multifrequency impedance matching broadband power amplifier (PA) design, which is different from the traditional PA impedance value changes with the change in the operating frequency. This method selects the impedance value of the transistor device through the load-pulling system. Then, matching networks composed of a cascade of microstrip lines are used to match the device impedance to 50 Omega. The matching networks are optimized to provide the desired impedance transfer characteristic at multiple frequencies. This design approach effectively reduces the amplifiers' output impedance variation over the covered frequency range. The overall structure of the PA is simple, and the bandwidth is expanded while ensuring performance. Based on this method, a broadband PA was designed and fabricated using the self-developed laterally-diffused metal-oxide semiconductor (LDMOS) transistor of the Institute of Microelectronics of the Chinese Academy of Sciences. The measurement results show that the saturated output power of the designed PA in the range of 0.5-23 GHz is greater than 41 dBm. The drain efficiency is 43.62%-55.38%. When the average output power is 34.3 dBm, the adjacent channel leakage ratio (ACLR) is also better than -31.58 dBc.