Research Of Millimeter Wave Linearizer

With the continuous improvement of emerging technologies such as artificial intelligence,cloud computing,and autonomous driving,which are closely related to the Internet and the Internet of Things,the mobile communication technology is developing toward high transmission rates,low connection delays,and wide access.In order to meet this Communication requirements,the fifth-generation mobile communication system(5G)has extended the spectrum to the millimeter wave band.In the millimeter wave communication system,in order to reduce energy consumption and ensure good communication quality,the power amplifier in the communication system is required to have both high efficiency and high linearity.In order to improve the linearity of the power amplifier,modern mobile communication systems often use predistortion technology to improve the linearity.However,due to the high frequency and large bandwidth of the millimeter wave band,the application of narrow bandwidth digital predistortion technology in the millimeter wave band is greatly restricted,and the analog predistortion technology relies on low power consumption,high frequency and large The advantage of bandwidth has become the key technology for linearization of millimeter wave communication systems.Therefore,based on the analog predistortion technology,combined with the nonlinear distortion characteristics of the traveling wave tube amplifier(TWTA)and the solid-state power amplifier(SSPA),this paper focuses on the millimeter wave band linearizer.Firstly,in this paper,Schottky diodes are used as non-linear generating devices,and high-low impedance microstrip line is introduced to the traditional parallel transmission analog predistortion structure,then an improved parallel transmission linearizer which bandwidth is 3 GHz for Q-band TWTA is designed.Due to the design parameters of the traditional structure is simple,so varies of the predistortion curve is limited.By combining with high-low impedance microstrip line,the design parameters are increased,so that the richness of the predistortion curve is improved.The test results show that the designed linearizer can produce 2 dB gain expansion and 30° phase shift expansion,and the P1 dB improvement of TWTA is 1.21~1.58 dB,the phase shift has been improved by 2.38°~7.02°.Then,for some special amplitude distortion characteristics of double knee SSPA with gain convex hull,by combining with reflective and improved parallel transmission structure,a double knee linearizer suitable for K band double knee SSPA was designed.By experimenting and testing,the linearizer can provide a gain depression depth of 3 dB and a phase offset compression of 30° in the operating band of 19~22 GHz.The test with the target SSPA shows that the linearizer can suppress the SSPA's gain convex hull within 0.5 dB where the original gain convex hull is 1.64~2.53 dB.The improvement of P1 dB is 4.98~5.81 dB,and the phase shift is improved by 7.38°~9.89°.Under the condition of that the output saturation power returns 3 dB,the SSPA's IMD3 has been improved by 3.17~15.11 dBc.