Research And Design Of Key Technologies Of Millimeter-Wave And Submillimeter-Wave Radar Radio-Frequency Front-End

With the rapid development of wireless technology,spectrum resources below sub-6 GHz are very crowded.People are gradually turning their attention to the millimeter wave（mm W）and sub-millimeter wave（sub-mm W）frequency bands.Compared with other sensing technologies,mm W and sub-mm W radar has been widely used in high-speed wireless communication transmission,auto driving and indoor imaging due to its features of long detection distance,strong anti-interference ability,good directivity and high spatial resolution,and has become the focus of research by the majority of scholars.Therefore,the radio frequency（RF）front-end modules of 24,77 and 300 GHz mm W and sub-mm W radar are researched and designed using CMOS technology with lower cost and easier integration.The main work is as follows:1)For the 24 GHz FMCW/Doppler dual-mode mm W radar receiver（RX）:Aiming at the serious problem of flicker noise at low intermediate frequency（IF）of RX due to the leakage of 24 GHz dual-mode radar chip transmitter（TX）to receiver,this paper innovatively proposes a multi-dimensional noise contribution mechanism analysis from the three aspects of RF path,local oscillator（LO）path and mixer.The modeling of mm W and sub-mm W devices and common techniques of amplifiers are also summarized.On the basis of the above theoretical and technical support,the low noise amplifier（LNA）,buffer amplifier and mixer in the RX module are designed to obtain excellent conversion gain and noise figure performance within the required bandwidth.The solution is also suitable for higher mm W and sub-mm W radar design.The 24 GHz dual-mode radar receiver chip has been successfully taped and measured.The measurement results show that: in Doppler mode,the conversion gain at 24.125 GHz is 18.27 d B,and the optimal noise figure is 23.67 d B@900 Hz.In FMCW mode,the maximum conversion gain is 17.46 d B@24.32 GHz,the intra-band gain is greater than 12 d B,and the optimal noise figure is 9.1 d B@128.3 k Hz.2)For 77 GHz FMCW phased array radar tripler chip: Compared with radars in the lower mm W band such as 24 GHz,the existence of multipliers is very important in77 GHz and sub-mm W radars to ensure the phase noise and chirp bandwidth performance of the radar chip.Therefore,this paper introduces the principle and classification of multipliers.In order to meet ther requirments of broadband chirp bandwidth of radar chips in the mm W and sub-mm W bands,harmonic multiplier is finally adopted to realize the required functions,and three harmonic enhancement techniques are proposed to enhance the conversion gain of the doubler and tripler respectively.On this basis,the design of 77 GHz FMCW radar tripler chip is completed.At present,the chip is in the state of being cast,and the simulation results show that the conversion gain in 76～81 GHz is greater than-8.5 d B,and the fundamental and second harmonic suppression ratio are better than 30 d Bc.3)For 300 GHz ultra-wideband FMCW radar transceiver（TRX）circuit: On the basis of the above research on the mm W radar RF front-end,this paper also completes the design of 300 GHz sub-mm W ultra-wideband radar transceiver front-end.Firstly,this paper discusses the problem that the single-channel TRX circuit cannot achieve the ultra-large bandwidth of 150 GHz in the sub-mm W frequency band,and finally decides to divide the entire frequency band from 250 to 400 GHz into eight channels,each of which occupies a bandwidth of 18.75 GHz to solve the problem.For TX module,the traditional PA-Last structure is difficult to obtain the required output power at such high frequencies,so this design adopts the combination of buffer amplifiers and multipliers,wherein the buffer amplifiers provide power gain at a relatively low frequency band,and the multipliers provide output power at a high frequency band.Due to the large difference in such frequency bands,this design innovatively proposes a " segmented " TX construction,in which the first four-channels（250～325 GHz）of TX adopts 3*2*2frequency multiplication scheme,and doubler in the last stage adopts push-push structure to transform the differential signal into a single-end and connect with the antenna.For the last four channels（325～400 GHz）,2*2*3 frequency multiplication scheme is adopted because the pre-frequency band of the last stage of 3*2*2 frequency multiplication scheme is close to 200 GHz,and it is difficult to design the buffer amplifier gain in this band.The RX module adopts Mixer-First structure,and cooperates with a single antenna configuration to use the transmit signal as a local oscillator signal,and post an IF low-noise amplifier to provide gain and suppress noise,thereby the gain insertion loss and noise problems caused by LNA in sub-mm W band can be avoided.In addition,this design also proposes a quarter-wavelength transmission line switching scheme for the switching of each channel of the TRX,and uses its impedance transformation and gradual change characteristics to achieve smooth connection between channels.At present,the sub-mm W radar transceiver front-end chip only completes the core layout of each channel.The post-core simulation results show that: under the TT process angle,the transceiver chip achieves an output power of-9.3～0.3 d Bm and-4～4 d B convertion gain within the 150 GHz bandwidth.and noise figure performance of 37.8～41.4 d B@390 k Hz,27.9～32.1 d B@3.9 MHz.