| The wavelength of millimeter wave is between the light wave and the centimeter wave,and combine the advantages of photoelectric guidance and microwave guidance.The millimeter wave radar has the characteristics of long distance,high reliability and less effect by light so that it can realize all-weather and all-day working.At the same time,it has certain penetrating ability and strong anti-interference ability to adapt to complex environments.The radar based on the frequency-modulated continuous wave(FMCW)can obtain the distance,velocity and azimuth of the target according to the frequency difference and phase difference between the transmitted signal and the received signal after frequency modulation of the continuous wave.The millimeter-wave FMCW wave radar can be used not only for airborne-loaded and missile-loaded millimeter-wave guidance in military applications,but also has been applied in civil applications such as unmanned obstacle avoidance and automotive radar.As a common atmospheric window band with high electromagnetic wave transmittance in millimeter waves,the Ka-band has a wide available bandwidth.But the large rain attenuation of Ka-band put forward higher requirements for devices and processes.As a crucial RF device,the concentrated application of Ka-band FMCW radar in military and missiles guidance puts higher requirements on performance and integration.However,the few researches in this field cannot effectively meet the requirements of low cost,high performance and high integration.And it is urgent to carry out further study.This paper studies the basic structures and working principles of the Ka-band FMCW radar,and designs a T/R module with a low-phase-noise,high-efficiency transmitting channel and eight high-sensitivity,large-dynamic-range receiving channels based on the architecture orthogonal of the transmitting channel and receiving channels.The transmitting channel is mainly composed of a voltage controlled oscillator,a frequency multiplier,a filter,a splitter,a driving amplifier and a power amplifier,and the transmitting signal is generated by an external triangular wave voltage after frequency modulation,and is output after frequency multiplication and power amplification.At the same time,a full LDO type regulated power supply is used in order to reduce the phase noise below-90dBc/Hz@100kHz.The receiving channel are mainly composed of a limiter,a low noise amplifier,a mixer,a filter,an intermediate frequency amplification.In order to improve the sensitivity and large dynamic range of the receiver,an alternating series combination of amplification and attenuation is used to ensure that the amplifier is in a linear working area with a dynamic range of up to 40 dB.In order to avoid transmission and reception coupling and signal crosstalk,the transmitting channel and the receiving channels and each receiving channel are respectively isolated by a metal cavity.The power supply of low-noise amplifier and the intermediate frequency amplifier are realizing by the through-wall insulator.And a specially designed debugging piece is used to obtain a component with amplitude consistency less than 1 dB and phase consistency less than 15°.In the RF channel,the whole die are designed with amplifiers,filters,etc.,and are processed by micro-assembly and metal packaging process with high integration and high reliability.In addition,based on the self-mixing architecture of transmitting channel and receiving channels,which integrated with the voltage-controlled oscillator,corresponding test schemes are proposed for complex problems such as the unstable local oscillator of VCO and image suppression of receiving channel integrated mixer,and the phase noise and receiving channels.This paper realized the accurate testing of the key indicators such as phase noise,noise figure,and the consistency of amplitude and phase.Besides,an automated test system consisting of DC power supplies,signal sources,and spectrum analyzers is developed,which is based on the object-oriented C#language.This test system can realize automatic operation of instrument control,result display,data processing,etc.and improve the test efficiency.The T/R module can meet the wide application requirements of direction finding and speed measuring of short-range and long-range target in military and civilian applications,and have wide application prospects. |
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