Research On Millimeter-wave Broadband Power Combining And Mixing Techniques

With the rapid development of modern electronic systems such as millimeter-wave radars,broadband communication systems,test instruments and electronic countermeasure(ECM)syetems,the demand for millimeter-wave broadband power source has been increasing in recent years.Microwave and millimeter-wave power combining techniques are efficient approaches to enhance the output power of solid-state sources.They are usually divided into three categories: chip-level,circuit-level and spatial-level power combining,all of which have been widely concerned and explored for quite a few decades.Based on the current MMIC amplifier chip technology and product status,the objective of this paper is to develop E-band and W-band solid-state power sources with broadband,high output power,high combining efficiency and compact structure.Relevant theory and key techniques of waveguide-based and microstrip-based circuit-level power combining have been studied in-depth and applied to the design of E-band and W-band broadband quasi-coplanar waveguide power dividing/combining networks,E-band and Q-band microstrip double-probe ringtype combining networks and the corresponding solid-state power combining amplifier modules and assemblies.Meanwhile,in order to expand the operation frequency band of noise figure testing system to full W-band,a cost-effective W-band sub-harmonic mixer with a wide intermediate frequency(IF)band and low conversion loss is developed by using commercially available Schottky diodes.The mixer is integrated with the Q-band power combined amplifier module as its LO source,a W-band broadband high-precision noise figure test system is realized.The main progress reported in this thesis is as follows:1.The modeling,simulation and optimization techniques have been intensively studied for the design of quasi-coplanar waveguide power divider/combiners in E-band and W-band.In this quasicoplanar structure,power dividing/combining is realized by a T-junction in E-plane of the stepped reduced height waveguides.The unbalanced wave is coupled out by a microstrip probe inserted in the center of the common waveguide and absorbed by a matching load of the microstrip line,leading to the isolation between two dividing ports.A microstrip double-probe quasi-coplanar waveguide power dividing/combining network is proposed to improve isolation.The full-wave simulation model of the E-band and W-band quasi-coplanar waveguide power divider/combiner are established by means of HFSS.And the electrical characteristics of the power divider/combiner in these two frequency bands are simulated and analyzed,and the optimization of key parameters such as window width of the probe is carried out.The complex process of precision machining,precision assembly of structural parts and microstrip circuits are fulfilled and the prototypes of the E and W-band broadband quasi-coplanar waveguide power dividers/combiners are fabricated and tested.The measurement results show that the typical insertion loss of the E-band power divider in the 60-90 GHz frequency band is 3.25 d B,and the amplitude imbalance of the two output branches is less than 0.11 d B,and the isolation between the output ports is better than 10 d B;the insertion loss of the W-band power divider is less than 3.4d B over 90-100 GHz,the amplitude imbalance is less than 0.05 d B,and the isolation is greater than 14.8d B.The objective of wide-band,low insertion loss,high isolation and structural compactness has been fulfilled.2.Using E-band and W-band commercially available MMIC chips,single-chip power amplifier modules of these two frequency bands are designed and fabricated.Experimental study of E-band and W-band power combining amplifier assemblies has been completed combined with the abovementioned quasi-coplanar waveguide power divider/combiner.Firstly,HFSS is applied to optimize the E-band waveguide-microstrip transition structure with broadband and low insertion loss,and the parasitic resonance characteristics of microstrip line and cavity structure are investigated,the structural parameters of shielding cavity are optimized.The assembling of the MMIC chip to microstrip circuit and the optimizing of DC power supply circuits are completed.The measured results show that in 70-77 GHz frequency band,the saturated output power of the two E-band power amplifiers is 25.1～27.1d Bm and 24.9～26.9d Bm respectively,with the amplitude imbalance less than0.3d B.The W-band power amplifiers are developed using domestic high-power chips.The test results show that the saturated output power of the two power amplifiers is 31.0～32.8d Bm and31.1～32.8d Bm respectively over 92-96 GHz.The amplitude imbalance is less than 0.5d B,being excellent in their consistency.By assembling the above-mentioned power amplifiers with the broadband quasi-coplanar waveguide power dividing/combining networks respectively,the E-band and W-band two-way power combining modules are developed.The measured results show that in the 70-77 GHz frequency band,the saturated output power of the E-band power combining assembly is 27.7d Bm～29.3d Bm,and the power combining efficiency is 80%～92%;the saturated output power of the W-band power combining assembly is above 33.6d Bm with the peak power being 35.4d Bm,and the combining efficiency is 81.4%～95.1% over 92-96 GHz.3.A compact microstrip ring-type power dividing/combining network is designed based on the anti-phase double-probe microstrip-waveguide conversion structure.By analyzing the influence of structural parameters such as the size of the microstrip probe and the location of the waveguide short road surface on the coupling performance of the probe,the return loss of the optimized E-band power dividing/combining network is more than 15 d B and the insertion loss is less than 1.2d B over 60-90 GHz.A compact two-way power combining amplifier is designed by using the E-band MMIC chip g APZ0051,and the experimental debugging is completed.The test results show that the power combining amplifier has an output power of 26.6～28.7d Bm in the frequency band of 70-77 GHz,which is comparable to the power combining assembly based on the quasi-coplanar waveguide power dividing/combining network,but has the obvious advantage of miniaturization of the structure size.The Q-band full-band power dividing/combining network is also optimized by using the double-probe microstrip-waveguide conversion structure,with the insertion loss less than 0.8d B over 33-50 GHz.Using the XD1001 broadband MMIC chip,a Q-band two-way power combining amplifier circuit is developed,and used as the final stage power amplifier of the quadrupler.The test results show that the output power is 18.65±1.35 d Bm within 33-50 GHz,which features flat output power over wide frequency band.It provides a good candidate for LO sources and low-power signal sources.4.A W-band wide-IF sub-harmonic mixer is designed based on the low-cost Schottky diodes MA4E1310 delivered by M/A-COM Inc.Firstly,the corresponding relationship between the valley point of the transmission coefficient of the LO and RF signal to the Schottky junction and the peak point of the conversion loss is analyzed.By optimizing the size of the key parameters on the cancellation path of the mixer,the IF concave point problem caused by RF cancellation effect in the wide frequency range is solved,and the IF frequency band of the mixer is effectively broadened.The down-conversion experiment of the broadband mixer is carried out with the Q-band quadrupler as LO source.When the LO frequency is fixed at 45 GHz,the conversion loss of RF in the frequency range of 75GHz-110 GHz is 14.5～23.2d B,and the frequency response curve is relatively smooth without obvious resonance point.Based on noise figure analyzer(N8975A)and W-band noise source(NC5110A),a W-band noise figure test system is constructed with the developed W-band wide-IF sub-harmonic mixer and Q-band quadrupler,the test of the W-band LNA sample is carried out.