Research On The Key Technologies Of Radar Transceiver Components

Radar(radio detection and ranging)is a wireless equipment which actively transmits electromagnetic waves.It could detects,ranges and even images targets through the reflected electromagnetic waves.In general,the wireless transceiver components of radar have higher requirments than the components of communication and navigation.The main differences are the high transmission power,wide operating band and complex frequency conversion(local oscillator and mixer)method.If the radar involves electronic countermeasure function,the linearity requirment of radar transmitter will not be lower than the high performance communication transmitter.Besides,radar equipment,especially the phased array radar with many channels,often has strict requirements in integration and miniaturization.Ka band,as the first low loss atmospheric window in millimeter wave band,is facilitated for radar to get farther detection range.And many radar applications crowd in this band.The ultra-wideband application is conducive to improve the accuracy of the radar ranging and imaging.It is a research focus in the field of radar.In this paper,our study is developed around power amplifier(PA)and filter.The two are key devices in radar transceiver components.Our study refers to two-tone nonlinearity analysis of PA with its behavior model,the MMIC(Monolithic Microwave Integrated Circuit)design focused on Ka band PA,and the ultra-wideband filter with high selectivity and compact size.The main contents and innovations of this paper are as follows:1 The two-tone nonlinearity and memory effects of power amplifier are studied in this paper.First,the PA circuits with two-tone excitation are analyzed by the Volterra series approach.Under the limitation of nonlinear order ?3 and number of mixing times ?2,the complete analytical formula of PA IM3(3rd order intermodulation distortion)products is derived in this paper.This IM3 products formula includes the gate memory,drain memory and cross memory of gate-drain.Then,this IM3 circuit analysis is transformed into a simplified GMP(Generalized Memory Polynomial)behavior model and a 10 Watts GaN HEMT PA is designed,measured and modeled.The normalized RMSE(root mean square error)of modeling is only 0.6145%,which proves that the IM3 products formula in this paper has high accuracy.Finally,the relationship between the PA bias circuit and the number of time delay taps in digital predistortion(DPD)circuit is pointed out.In these series of analyses,the complete evolvements are shown from PA bias circuit,to IM3 products,and then to PA behavior model,even refer to the scale of DPD circuit.These analyses could deepen the understanding of PA circuit designers in the relative mechanism,guide the design of linearity PA,especially the design of high linearity PA with DPD,and avoid that a fabricated PA can not be corrected by a scale-limited DPD circuit to meet the linearity requirements.2.Based on the GaAs pHEMT processes,the design of MMIC foucsed on Ka band PA is studied.These studies refer to the matching skill of wideband PA,the chip size compression of PA,the design of linearity PA,low frequency stability and nonlinear stability in PA,and the transistor model correction in the used processes.A wideband matching skill based on the capacitive coupled double resonators is proposed.A high efficiency wideband PA with the 32-40 GHz operating band is designed by this skill.And the measured results show this chip has high PAE performance(30%-35.5%)in its operating band.Besides,the design skills of linearity PA is analysed by the the IM3 formula presented in this paper,and a 2 watts linearity PA of 28-31 GHz is designed by this skill.The sensitivity between the gate 2rd harmonic impedance and PA linearity(IM3)performance is explained and emphasized.In the first round of tapeout of this PA chip,the 31-33.6dBm onchip output power is obtained with the deduction of 0.8dB waveguide and gold wire loss.3.The design methods of high selectivity ultra-wideband filters with compact size is discussed in this paper,and how to realize the ultra-wideband filter with deep attenuation notched band is also studied.Four filters are designed in total.An ultrawideband filter based on the defected microstrip structure is proposed.This filter is very compact size(0.51?_g×0.12?_g)and its 3dB fractional bandwidth is very wide(129%).In these very compact size ultra-wideband filters,its selectivity is also good with the S.F.(skirt factor)=0.7.Besides,an ultra wideband filter based on CPW-microstrip transition of balun mechanism is proposed.It has the good performances in size and selectivity simultaneously.Its size is only 0.25?_g×0.36?_g and its selectivity is S.F.=0.9.In addition,an improved type with notched band of this filter is realized.The deep attenuation of the notched band is 41 dB in measured results.