The Novel Parallel Plate Waveguide Antennas And Its Application

The parallel plate waveguide(PPW)has the advantages of simple structure,low profile and low loss.These typical characteristics have many potential applications in antenna design.Several new antennas based on the PPW structure have been designed in this dissertation,including:beam-scanning antennas,dual-polarized antenna,terahertz(THz)Pillbox beam scanning antenna,and a set of imaging experiment system was built based on the THz Pillbox beam scanning antenna.The details are introduced as follows:Firstly,most current beam scanning antennas are implemented with phase shifters,which are costly and complicated in structure.In order to achieve low-cost and high-performance beam scanning characters,a beam-scanning antenna combining a parallel Continuous Transverse Stub(CTS)radiation array and a new feed system was proposed.The PPW based CTS array serves as a radiation aperture.The ridge waveguide slot linear array serves as a feed system.By mechanically rotating the linear feed,the phase of the plane wave in the PPW is deflected.Thereby beam scanning antenna can be achieved.The characteristics of the plane wave excited by the linear feed under different rotation states are analyzed.It is demonstrated that the structure is a good choice for realizing the plane wave excitation of the PPW.Finally,the beam scanning CTS antenna system was simulated and tested.In the±30~o beam scanning range,the radiation efficiency at the center frequency was higher than 60%.Secondly,in order to achieve low profile,low-cost and high-performance beam scanning characters.Based on the previous design,a novel beam scanning antenna combining the beam scanning feed system and the waveguide slot array was proposed.The waveguide slot array acts as the radiate aperture in antenna system,which can greatly reduce the profile of the antenna compared to the parallel CTS array.Through the Taylor distribution design of the radiating waveguide slot array and the feed line slot array,two-dimensional low side lobes of the scanning beam are realized.The 24×10-element array antenna simulation and test results show that the antenna has good beam scanning characteristics within a range of±30~o,and the aperture radiation efficiency is high.Thirdly,aiming at the contradiction between miniaturization and high efficiency of dual-polarization array antenna,a new dual-polarized antenna array based on PPW and2×2 subarrays was proposed.The antenna adopts a new type of 2×2 sub-array as the radiating aperture.The 2×2 subarray units are fed by the PPW through coupling cross-slot.A pair of H-plane waveguide arrays feeds the dual-polarized PPW.Due to the adoption of this new 2×2 subarray and low profile PPW structure,the dual-polarized antenna array structure is very compact.The measured results of the 8×8-element array show that the bandwidths of the two polarizations are 6.2%(11.94-12.7GHz)and 5.1%(12-12.63GHz),respectively.The isolation is better than 25dB,and the radiation efficiency is higher than60%.Fourthly,aiming at the great demand of fast THz imaging for civil market and military applications,a THz beam scanning imaging system based on focused real aperture and synthetic aperture was proposed.The system uses a frequency scanning Pillbox antenna based on the PPW structure as a transceiver module.The Pillbox antenna has a typical fan beam,the horizontal narrow beam combines frequency scanning to achieve fast real-aperture imaging,and the vertical wide-beam combines vertical motion to achieve synthetic aperture high-resolution imaging.The feed and the radiation aperture of the frequency scanning Pillbox antenna are in the form of a rectangular waveguide array fed in parallel and a pyramidal horn,respectively.The feed antenna can achieve a beam scan range of-21.8~o to 20.2~o in the bandwidth of 186GHz to 202GHz.The main structure of the Pillbox antenna is PPW and parabolic reflector.The parameters design of the PPW structure is mainly based on Gaussian beam theory.Fifthly,in order to verify the imaging capability of the system,a THz beam scanning imaging system was built based on the Agilent vector network analyzer and THz expansion modules.Since the bandwidth of the antenna is mainly used for fast beam scanning,the imaging system has no distance resolution capability.Through the two-dimensional imaging experiments on typical targets such as metal strips,metal and ceramic knife,the potential application of this system in security inspection was demonstrated.