Development Of Ka-band Miniaturized Broadband Transceiver Front-end

With the development of the technology,the imaging precision,volume and other requirements of imaging radar in the fields of resource exploration,environmental monitoring,telemetry and remote control are becoming increasingly high,which promotes the development of imaging radar towards miniaturization,high frequency and broadband.The characteristics of short wavelength and wideband make the MMW system miniaturized and broadband,which makes the MMW wideband radar get more attention and develop rapidly in recent years.Based on the research background and development status,this paper presents the design process of a Ka-band miniature wideband transceiver front-end.The system consists of a power module,a frequency synthesizer and an RF link module.The frequency synthesizer includes two phase-locked loops for up and down frequency conversion and its FPGA control circuit.The RF link module is composed of transmitting link and receiving link.The transmitting link includes an up-conversion mixer,a frequency multiplier,a power amplifier,and Ku,Ka-band filters.The transmitting intermediate frequency signal range from 730 MHz to 870 MHz.The local oscillator signal needs frequency hopping for six times.The receiving link is composed of an RF switch,a low noise amplifier,a Ka-band filter,a downconverter mixer,and the intermediate frequency amplifying link.The frequency range of the receiving intermediate frequency signal is 500 MHz to 700 MHz.The local oscillator signal needs frequency hopping for twelve times.The operating frequency range of the whole transceiver front-end is 34.4GHz to 36.8GHz and the size of the whole wideband radar transceiver front-end is 10cm×10cm×3cm.Miniaturization of passive devices is the key to miniaturization of transceiver frontend.For Ku-band filters design,two filters with a passband range of 11.4GHz to 12.3GHz are designed using a quarter-wavelength(?4)stepped impedance resonator(SIR)and a three-mode substrate integrated Waveguide(SIW)resonator.For Ka-band filters design,rectangular and 90° fan-shaped SIW resonators are used to design third-order and fourthorder filters with a passband range of 34.4GHz to 36.8GHz.Through testing,the size and performance of the filters are comprehensively considered.The ?4 SIR filter(size: 8mm×8.2mm)and the rectangular SIW filter(size: 10mm×10.92mm)are adopted.Finally,the key indexes of the whole broadband transceiver front-end are tested.According to the results,the phase noise of the local oscillator of the transmitting link and receiving link is-84 dBc /Hz@100Hz and-78 dBc /Hz@100Hz respectively.The frequency hopping time of the local oscillator is 23 us.The 1dB compression point of transmission link is 20.5dBm,and the in-band gain flatness is 1.05 dB.Without VGA attenuation,the gain of the receiving link is 55.1dB while the in-band flatness is less than 1dB.