基于毫米波负载调制网络优化设计的26 GHz Doherty功率放大器MMIC

A 26 GHz Doherty Power Amplifier MMIC with Optimal Millimeter-wave Load Modulation Network Design

提出了一种毫米波Doherty放大器负载调制网络结构及优化设计方法。该方法在改善传统方案调制不充分的同时,去除影响工作带宽的四分之一波长线,有效降低输出网络的复杂度,减少匹配损耗,提高了Doherty放大器效率和工作带宽。基于提出的优化设计方法,采用0.15μm GaN HEMT工艺,研制了一款中心频率在26 GHz的Doherty功率放大器芯片。芯片采用对称式结构,主功放的输出网络直接选取50Ω作为最佳负载阻抗,实现了输出端到管芯本征参考平面的阻抗变换;辅功放的输出网络既实现了阻抗匹配,还确保了关断时的高阻状态。连续波测试结果表明,放大器在23.5~29.0 GHz频率范围内,饱和输出功率大于36 dBm,最大功率附加效率为35%,在26 GHz输出功率回退8 dB时,附加效率达到32%。

A kind of load modulation network topology in millimeter-wave Doherty power amplifier(PA)and its optimized design method were proposed,which not only improved the problem of insufficient modulation in traditional scheme,but also reduced the complexity of output network.Due to removing the quarter-wavelength line which limited the bandwidth,the matching loss is reduced,the efficiency and the working bandwidth of Doherty PA are improved.Based on this method,a Doherty PA chip with a center frequency of 26 GHz is developed using 0.15μm GaN HEMT technology.The MMIC utilizes symmetrical structure.The output matching network of main PA directly chooses 50Ωas the optimal load impedance,which realizes impedance transformation between output port and intrinsic reference plane of transistors.The output network of auxiliary PA not only realizes impedance matching,but also ensures the high impedance when it turns off.Continuous wave test results show that the saturated power is more than 36 dBm and the peak power added efficiency is 35%in 23.5~29.0 GHz frequency range.At 8 dB output back-off(OBO),the power added efficiency is up to 32%at 26 GHz.