Investigations On Some Key Millimeter Wave Passive Elements And Antennas

The social and economic development of humankind has changed the way wireless communication is used today.The digitalization of almost everything,from banking to entertainment industry is leading to an avalanche of mobile and wireless traffic volume.However,on other hand the integration of multiple devices on single chip is taking place.Now the mobile phone is not just the device to connect people-to-people rather,it connect anything-to-everything;to handle the growing wireless traffic effectively and to cope with the challenges of high-integration at system level,there is urgent need of modern radio-frequency(RF)components.Passive devices and antennas are the one took most space in any wireless communication system's integrated circuit(IC).Previously the "transverse electric(TE)mode"operation based components were used to be designed using metallic waveguide however,their huge size and different nature from rest of the elements in IC,spoil the integrity of communication system,in total.Owning to the merits of hybrid "planar and waveguide" nature,smaller size,light-weight,and low radiation and surface wave losses,substrate integrated waveguides(SIW)based components catch much attention in recent years.Nevertheless,the high quality factor of SIW limits the operating bandwidth of components,based on it.Meanwhile,the research and development(R&D)on passive components is internationally on developing stage than ever.Aiming at the frequency bands,recently allocated for future wireless communication in millimeter-wave such as,Q-band for Q-LINKPAN and IEEE 802.11aj standards,28 and 31 GHz band for local multipoint distribution service(LMDS),and E-band for satellite communication,this dissertation investigates the alternative structures and techniques to design the wideband cavity-backed antennas,the multilayer-slot-fed antenna with stable gain wide-bandwidth,the high gain single-feed single/dual-polarized cavity-backed circularly-polarized antenna,a dual-band SIW-cavity based bandpass-filter(BPFs),and an orthomode-transducer(OMT)on metallic slab.The dissertation is organized as follows:Chapter one briefly reviews the backgrounds of some key RF passive components and antennas at first.Then,the current challenges on wireless communication are introduced,furthermore,the research objectives and main contents of the dissertation are elaborated.Chapter two proposed a cavity backed triangular-complimentary-split-ring-slot(TCSRS)antenna,which have wideband and high gain characteristics.Substrate integrated waveguide(SIW)cavity is used to excite the TCSRS antenna;the proposed antenna have been designed and implemented at both 28GHz and 45GHz frequencies for fifth-generation(5G)wireless communication.Firstly,the proposed antenna element has been investigated in principle,then the antenna array with two and four elements are designed.Furthermore,the prototypes of the antenna and its arrays are fabricated with standard Printed Circuit Board(PCB)process on Rogers RT/Duroid 5880 with substrate height of 0.508mm at both frequencies.Measured results show that 16.67%impedance bandwidth at 28GHz band and 22.2%impedance bandwidth at 45 GHz band are achieved,respectively.The measured peak gains of the 2×2 antenna arrays at 30 and 50 GHz are 13.5 and 15 dBi,respectively.The study on TCSRS has been further extended and high-gain 2×4 antenna array in two-layer structure is designed using aperture coupling.This two-layer structure have maximum gain of 16.28 dBi at 48 GHz,with wideband wide-beam polarization purity.The problem with conventional cavity-backed antenna,in array application,is the large-size of its power-divider,here the attempts are made to solve the problem using two layer structure.Part of the research from this chapter is published in IEEE Trans.Antennas Propag.Chapter three proposed the two layer aperture coupled 2×2 and 4×4 microstrip antenna array for large phased array application at 45 GHz.The Sn?-10 dB impedance bandwidth or 1-dB stable gain bandwidth(Simulated)of the proposed two-layer antenna arrays is beyond 25%or 15%,respectively.Moreover,the peak gain of the 4 x 4 array is 17.1-dBi.To verify the above mentioned results prototypes of the 2×2 and 4×4 patch antennas array are fabricated with PCB process,at 45 GHz band.The measured results shows that the 2 x 2 antenna array have 25%impedance bandwidth and 19%3-dB gain bandwidth with peak gain of 14-dBi moreover,the 4×4 antenna array have more than 30%impedance bandwidth with larger than 18%3-dB gain bandwidth and peak gain of 17.4-dBi.Chapter four proposed the cavity-backed circularly-polarized,circular-patch(CB-(CP)2)antenna,based on substrate integrated waveguide(SIW)technology.Proposed antenna consist of,a circular patch resonating at its dominant-mode TM11,a rectangular SIW-cavity resonating at its dominant mode TE101,and a SIW feed-line.For the purpose of generating a circular-polarization(CP)wave the circular-patch of the antenna is shorted to the top metal layer of SIW-cavity through an orthogonally(almost)oriented metallic-strips.Proposed antenna have impedance bandwidth of 9.5%,with 2%overlapped 3-dB axial ratio(AR)bandwidth.The peak-gain of the antenna is 8.1 dBi at 33.8 GHz.This work has been further extended and the dual-band dual-polarized CP antenna has been designed by adding three more resonating slots at the top metallic ground within the cavity,and an additional shorting via at the vertex,also within the cavity.The part of the research from this chapter has been submitted in Wiley Interscience,Microwave and Optical Technology letters.Chapter five proposed the simple three-port orthomode transducer(OMT)structure for wide-band operation.The proposed OMT is free of shorting pin,metallic septum,or pyramid—to achieve the better bandwidth performance.The three port junction includes the square waveguide port with cross-section of 2.54 mm x 2.54 mm,and the two orthogonally oriented rectangular waveguide ports with cross-section of 2.54 mm × 1.27 mm.This three port transition make the proposed OMT simpler,without braking the design's planar symmetry.The OMT have been simulated,designed and tested practically for WR-10 waveguide band.The operating band of the OMT is 70-95 GHz,and bandwidth(BW)is wider than 30%,simulated insertion loss of the OMT is also better than-0.3 dB moreover,the cross polarization level is below-35 dB.The part of the research of this chapter is presented in IEEE International Wireless Symposium 2015,Shenzhen.Chapter six proposed the novel technique to design a dual-band bandpass filter,by exploiting the second order degenerated modes of SI W-cavity.The second order filter has been designed using proposed technique at Ka-band.The ratio of the two bands center frequencies[frequency ratio(FR)]is 1.073.The prototype of the proposed second-order filter is fabricated on Rogers RT/Duroid 5880,with substrate height of 0.508 mm.The measured return-loss of the filter in both bands is better than 15-dB,moreover,the isolation between two bands is also better than 40-dB.The part of the research from this chapter has been presented in IEEE 2015 Asia-Pacific Microwave Conference,Nanjing.