Research And Design Of Miniaturized And High Performance Microwave Filters In Multi-Function Integrated Communication Systems

With the rapid development of wireless communication technology,the communication systems with different frequency bands and functions are emerging vigorously.In order to meet users' diversified communication demands,it has become the inevitable trend for the wireless communication system to develop towards the integration of multi-bands,multi-standards and multi-functions.To meet the development demands of multi-standards,multi-functions,miniaturization and low power consumption of wireless communication system,this thesis studies the design methods of miniaturized and high performance microwave filters which are based on metal cavity,printed circuit board and CMOS process,by using the theroy of generalized chebyshev filters,the coupling matrix synthesis theory,the multi-mode resonance theory and the method of odd-even mode analysis,respectively.The main research work of this thesis are organized as follows:1.Based on the synthesis theroy of generalized chebyshev filters and the coupling matrix,a miniaturized and high performance dual-frequency combiner is designed and implemented.The unit filter of the combiner adopts a coaxial resonator structure with high Q value and high selectivity.The combiner uses a back-to-back common port,which reduces the mutual interference between the unit filters.Finally,each unit filter is optimized by using the parameters extracted by the Cauchy method.The measured results show that the two unit filters of the combiner have a frequency band range of 1710-1880 MHz and 1920-2200 MHz,respectively.The insertion-loss is 0.7 dB and 0.55 dB.The return-loss over the passband are both better than 23 dB,and the isolation between the filters is greater than 34 dB.2.Based on the theory of multimode resonance,a folded multimode resonator loaded with stepped impedance short-circuited stubs is proposed.Based on this resonator,a miniaturized and high selectivity ultra-wideband bandpass filter is designed and implemented.The short-circuited stubs and the cross coupling introduced by the folded structure can generate transmission zeros on both sides of the passband,which improve the selectivity of the filter.The measured results show that the fractional bandwidth of the filter is 111.5%,the average insertion-loss is 0.8 dB,the return loss is better than 13 dB,and the two transmission zeros are located at 2.0 GHz and 12.2 GHz,respectively.3.A composite right/left-handed transmission line unit cell with two short-circuited stubs loaded is proposed.Then,based on the unit cell and the anti-coupled line structure,two ultra-wideband bandpass filters with compact sizes and high out-of-band performance are designed and implemented.The balanced composite right/left-handed transmission line unit cell can provide ultra wide passband,and the cascaded anti-coupled line structure can effectively improve the passband performance and suppress the upper stopband harmonics.The measured results show that the fractional bandwidths of the two filters are 113.9%and 110.9%,respectively.The average insertion-losses are 0.8dB and 0.7 dB.The two filters have a wide upper stopband from 14-30GHz and 11.4-30GHz with a high rejection level of 20dB and 18dB.Both of them have very compact sizes,only 14.4mm×10.2mm and 7.4mm×6.4mm,respectively.4.In order to meet the design requirements of multi-functional system for millimeter wave communication,a resonator based on three-parallel-coupled line structure is proposed.Based on the resonator,a miniaturized and high selectivity millimeter-wave bandpass filter is designed and implemented.The short-circuited line and the cross coupling introduced by the three-parallel-coupled line structure can generate transmission zeros on both sides of the passband,which improves the selectivity of the filter.Then the structure is folded to make the circuit compact.Finally,the filter is fabricated by standard 0.13 ?m RF CMOS process.The measured results show that the center frequency of the filter is 60 GHz,the insertion loss is 2.03 dB,and the return-loss is better than 21 dB.Two transmission zeros are located at 18 GHz and 100 GHz respectively.The whole size of the on-chip filter is 267 ?m × 376 ?m.