Research On Millimeter-Wave Gap Waveguide Technology And FMCW Reflected Power Cancelation Systems

Gap waveguide is a newly emerged technology in microwave and millimeter wave circuits design.It uses parallel perfect-electric-conductor(PEC)plate and artificial-magnetic-conductor(AMC)plate as wave shielding structure.The two plates form a wide electromagnetic forbidden band between them without direct contact.The most commonly used gap waveguides are ridge gap waveguide,groove gap waveguide and inverted microstrip gap waveguide.The dominant modes of ridge gap waveguide and groove gap waveguide are respectively TEM mode and Quasi-TE 10 mode,which are similar to microstrip line and rectangular waveguide.The dielectric of ridge gap waveguide is air,which results in lower insertion loss compared to microstrip line.In addition,the grid gap waveguide is a closed form transmission line,which also has better EMC performance.In comparison of traditional waveguide,groove gap waveguide does not need direct contact,which results in better design and manufacturing flexibility without considering electric contact.Therefore,it is of extremely important significance to carry out researches on gap waveguide technology.By the way,the reflected power cancelation of single antenna FMCW radar system is an important issue.Combined with the gap waveguide technology,some researches on 35GHz FMCW reflected power cancelation and single target ranging are conducted.The main work of this dissertation is as follows:1.Researches on wideband gap waveguide array antenna are conducted.Ridge gap waveguide and vertically polarized groove gap waveguide are commonly used as feeding in gap waveguide array antennas.The maximum bandwidth is about 15%.Horizontally polarized groove gap waveguide is first used as feeding in this paper.A 8×8 gap waveguide slot array antenna with center frequency of 35GHz is proposed and successfully manufactured.The proposed antenna consists of four stacked metal layers.The bottom layer is the feeding layer realized by horizontally polarized groove gap waveguide.The feeding network is realized by cascaded T-type groove gap waveguide dividers.The second layer consists of 4x4 twisted waveguides.The anti-phase issue of T-type horizontally polarized groove gap waveguide divider is solve by waveguide twist arrays.The third and the top layer are the resonance layer and the radiation slot array layer.The measured bandwidth(S11<-10dB)is from 31.5GHz to 39.7GHz(23%),which is dramatically improved compared to similar work reported.The measured efficiency is better than 70%,which is equivalent to similar works.2.An improved groove gap waveguide referred to as full groove gap waveguide is proposed.The full groove gap waveguide consists of four contactless metal plates,which results in better design and manufacturing flexibility.Many circuits hard to be realized by traditional waveguide technology can be easily utilized by the proposed gap waveguide.In order to verify the performance of the proposed gap waveguide,a Ka-band full groove gap waveguide and an iris full groove gap waveguide filter are designed and tested.With the improved manufacturing flexibility,the electric performances of the proposed gap waveguide and the filter are equivalent to their waveguide counterparts.3.The key components of the gap waveguide circuits can be replaced with no need of reassembling the entire gap waveguide circuits.To verify this idea,a Ka-band gap waveguide coupler with tunable coupling coefficient is proposed.The specified coupling coefficient can be achieved by replaceing the common narrow-wall coupling plate with different inclined angles of coupling slots.4.Because of the contactless characteristic of gap waveguide circuit,relative motivation between its sub-components is impossible.A realtime rotatable rectangular waveguide twist based on contactless waveguide flange is proposed.Any angle between ±90°can be realized.Furthermore,a cylindrical contactless waveguide flange is proposed.A H-plane flexible rectangular waveguide and a realtime rotatable rectangular waveguide to coaxial line transition are proposed.If the rotatable transition is connected with another traditional transition,it forms a wideband rectangular waveguide rotary joint.5.A phase corrected H-plane horn antenna is proposed,simulated and tested.2-D bed of nails is an AMC surface which is also a slow wave structure.In the design of phase corrected horn antenna,1-D bed of nails is loaded as slow wave structure in the center region of the horn aperture.The loaded slow wave structure decreases the equivalent wavelength in the center region and therefore reduces the phase difference between the center and side regions.The length of the optimum H-plane horn antenna can be shortened significantly with its gain unchanged by using this technology.6.A Ka band high linearity millimeter-wave frequency-swept source based on DDS + multipler chain technique is designed and tested.A DDS,AD9915,from ADI and a DSP,TMS320VC5509A,from TI are used to design the wideband frequency-swept source,where the output band of the frequency-swept source is DC to 1 GHz,Cascaded by a ×2×8×3 multipler chain and a medium power amplifier,a Ka band high linearity frequency swept source is successfully manufactured.7.Theoretical and experimental researches on the FMCW RPC are studied.The bandwidth of the RPC is optimized by carefully design the time delay difference between the leakage path and the error detection path.On the other hand,a reasonable compromise between the leakage signal cancelation and the noise cancelation is achieved by optimizing the bandwidth of the loop control circuit.A 35GHz FMCW RPC is successfully designed and tested.Experiment results show that the operation bandwidth is wide and the cancelation performance of the RPC at single tune state and frequency-swept state are both very well.8.Researches on the receiver of the FMCW radar are studied.The SFC circuit,A/D converter circuit,communication circuit between AD and DSP are manufactured.Communication between A/D converter and the DSP through McBSP using EDA technique,data computation by DSP and communication between DSP and the information display screen are also finished.The receiver is integrated with the frequency-swept source,the high efficiency gap waveguide array antenna and the RPC to form a simple 35GHz FMCW radar system.The experimental FMCW radar has the ability of range detection of a single target.