基于谐波抑制与补偿线技术的非对称Doherty功放设计

为了提高WiMAX信号下doherty功率放大器（doherty power amplifier，DPA）回退点的效率，提出一种基于谐波抑制和补偿线技术的非对称doherty功放（asymmetric doherty power amplifiers，ADPA）结构。该结构在传统ADPA结构的基础上，首先对主功放（carrier）和辅功放（peak）输出匹配电路加入2次、3次谐波电路进行匹配设计，减少晶体管漏极电压电流的重合；然后通过添加补偿线（offset line）的方式，改变carrier和peak的功率分配比，使得整体电路获得更高的效率和输出功率。基于上述谐波抑制和补偿线理论，设计了一款工作在3.4 GHz~3.6 GHz，增益约为13 dB的ADPA。实测结果表明，当饱和输出功率达到48.75 dBm，功率回退9.5 dB时，功率附加效率（power added efficiency，PAE）达到41.8%，5 MHz偏移量的相邻信道功率比（adjacent channel power ratio，ACPR）优于-35 dBc，10 MHz偏移量的ACPR优于-48 dBc。满足WiMAX基站对功放线性度和效率的要求。

Design of ADPA based on harmonic suppression and compensation line

In order to improve the efficiency of the Doherty power amplifier (DPA) at the back off point in the WiMAX signal, this paper proposes an asymmetric Doherty power amplifier (ADPA) based on harmonic suppression and offset line technology. Based on the traditional asymmetric Doherty power amplifier design, the output matching circuit of the Carrier and Peak is designed with second or third harmonic circuit matching in order to reduce the coincidence between the drain voltage and current at the transistor; The power allocation ratio is optimized by adding in Offset line to improve the efficiency and output power performance. Based on the theory of harmonic suppression and offset line, this paper proposes an asymmetric Doherty power amplifier with a gain of about 13dB, which operates at 3.4~3.6GHz. The experimental results show that when the saturation output power reaches 48.75dBm and the power return amounts 9.5dB, power added efficiency (PAE) is 41.8%, the 5MHz offset of adjacent channel power ratio (ACPR) is better than -35dBc and the 10MHz offset of ACPR is better than -48dBc. The design satisfies the requirements of WiMAX base station on the linearity and efficiency of power amplifier.