| The traditional radio frequency band has gradually failed to meet the requirement for the rapidly developing wireless communication technology,and needs to be switched to a higher millimeter-wave frequency band,which brings challenges and opportunities to the design of radio frequency circuits.On the one hand,millimeterwave signals have high atmospheric loss,which hinders long-distance communication.On the other hand,the reduction of signal wavelength greatly reduces the antenna size,making it possible to miniaturize large-scale integrated systems.Phased-array is a technology based on antenna array,which has the ability of beam-forming and beamscanning.Phased-array technology has great advantages in spatial multiplexing,user tracking,and anti-interference,and has become one of the popular solutions for nextgeneration wireless systems.As one of the key modules in the phased array,the amplitude control module can perform array sidelobe suppression and beam shaping,so its research is of great significance to the development of phased array technology.This article starts from the basic working principle of the phased array,and discusses the function of the amplitude control module in the system.According to the phased-array sidelobe suppressing level,the influence of the amplitude adjustment range on the array performance and the necessity of phase error compensation of the amplitude control circuit are pointed out.The commonly used passive and active amplitude control circuits are summarized,their basic principles are briefly described and analyzed.Then,the generation mechanism and compensation method of the additional phase shift are summarized and proposed.Based on this,three amplitude control modules facing the phased array transceiver system are designed.Firstly,the transmission phase change of the traditional switch-type attenuator is analyzed,and the phase compensation network based on the filter structure is summarized.Then,a five-bit passive CMOS attenuator working in the Ka band is designed by using the phase compensation method of the filter tail capacitance.The attenuator unit adopts T-type attenuation network,which reduces the impedance fluctuation of the cascaded attenuator.Test results show that the attenuator has an RMS amplitude error of less than 0.5d B and an RMS phase error of less than 3°.In the channel measurement of phased-array system,the proposed attenuator can achieve a total attenuation range of 15.5d B in steps of 0.5d B under high and low temperature(85°C,-45°C)environments.The mechanism of amplifier gain and phase variation is analyzed,and the phase compensation structures based on common-source amplifier are summarized.The principle of low phase variation of cross-coupled variable gain amplifier(VGA)is analyzed.A K-band CMOS VGA with low phase variation is realized.The presented VGA has been tested.In the case of a single-stage variable gain circuit,the gain tuning range of 30 d B can be realized,and the phase error is less than 10°.The phase shifting mechanism of the cross-coupling VGA is analyzed based on the design experience,and the cross-capacitive phase compensation method is proposed.Based on the phasecompensated cross-coupled variable gain cell,a broadband low-noise variable gain amplifier operating in 25GHz～40GHz is designed.Simulation results show that the amplifier has a maximum gain of about 15 d B,a noise figure of less than 5,and a phase error of less than 3.5° in a gain adjustment range of 32 d B. |
PDF Full Text Request