Analytical Design Procedures for the Odd Mode of Ridge Gap Waveguide Devices and Antennas

The millimeter-wave (mm-wave) band has attracted attention due to its wideband characteristics that make it able to support multi-gigabit per second data rate. Nevertheless, the performance of mm-wave wireless communication systems is restricted due to attenuation loss. Design of mm-wave components and antennas is rapidly growing with the current evolution in the wireless communication systems. However, the traditional waveguide structures such as microstrip, coplanar, substrate integrated waveguide, and rectangular waveguide either suffer from high losses or difficulty in manufacturing at mm-wave band. The ridge gap waveguide (RGW) technology is considered as a promising waveguide technology for the mm-wave band. RGW technology overcomes the conventional guiding structure problems as the wave propagates in an air gap region which eliminates the dielectric loss. Moreover, RGW does not need any electrical contacts, unlike traditional rectangular waveguides. Also, the RGW can be implemented in the printed form (PRGW) for easy integration with other planer system components. In this thesis, the use of the odd mode (TE10 (RGW)) RGW to design mm-wave components and antennas is presented. First, a systematic design methodology for the RGW using hybrid PEC/PMC waveguide approximation is presented. This reduces the design time using full wave simulators. The concept has been verified by simulation and experimental measurements. Second, two different methods to excite the odd mode in RGW are studied and investigated. In the first method, a planar L-shape RGW is used where less than -10 dB reflection coefficient is achieved, from 28 to 36 GHz, and more than 93% of the input power has been converted into the odd mode at the output port. The second method uses a magic tee with a shorted sum port and provides a wideband pure odd mode at the output port with reflection coefficient less than -10 dB from 28 GHz to 39 GHz. Other mm-wave components based on odd mode TE10 RGW are designed and presented including a Y-junction power divider and 3 dB forward coupler are designed for the first time in RGW technology. The Y-junction has a wideband matching from 28 to 34 GHz with a reflection coefficient less than -15 dB and the transmission output levels are about -3.3 dB. The usefulness of the odd mode RGW lies in the ability to increase the channel bandwidth that has been achieved by designing a dual-mode RGW. A magic tee is used to simultaneously excite the fundamental mode Q-TEM and the odd mode TE10 (RGW) on the ridgeline. The proposed dual-mode RGW performance is verified through simulation and measurement of a back-to-back configuration. The proposed design achieves a matching level less than -10 dB for the two modes over the frequency range from 29 GHz to 34.5 GHz with isolation better than 23 dB. The dual-mode RGW is then used to feed a reconfigurable Vivaldi horn antenna where two different radiation patterns can be obtained depending on the excited mode. The Q-TEM generates a single beam pattern, while the odd mode TE10 (RGW) generates a dual-beam pattern. The maximum gain for the single beam radiation is 12.1 dBi, while it is 10.43 dBi for the dual-beam pattern. The bandwidth of the dual-mode antenna is 25% at 32 GHz with impedance matching less than -10 dB and isolation better than 20 dB. Finally, several antennas are presented in this thesis based on the odd mode RGW. A novel differential feeding cavity antenna using the odd mode of RGW is presented. The measured results show good performance in terms of gain, bandwidth, sidelobe level, and cross-polarization. The maximum gain is 16.5 dBi, and the sidelobe level is -17 dB and -13.8 dB, for the E-plane and H-plane, respectively. Moreover, the proposed antenna has low cross-polarization levels of -35 dB in the E-plane and -27 dB in the H-plane. In addition, two 2x1 linear frequency scanning array antennas are designed and implemented using the proposed Y-junction to generate single beam and dual-beam patterns. The beam scan is from -11(degree) to -40(degree) at 28 GHz and 32 GHz, respectively

Analytical Design Procedure for Forward Wave Couplers in RGW Technology Based on Hybrid PEC/PMC Waveguide Model

In this paper, a systematic design methodology of a 0dB and a 3dB forward couplers based on the ridge gap waveguide (RGW) technology is presented. This methodology is based on exact theoretical formulations rather than any approximate or empirical equations. The procedure of the proposed design methodology is mainly to build a virtual equivalent waveguide model. This waveguide has two horizontal upper and lower perfect electric conductor (PEC) walls, while the left and the right walls are made of perfect magnetic conductors (PMC). A detailed analysis for this hybrid PEC/PMC waveguide, a common waveguide for coupling, is introduced as the starting phase for designing the RGW couplers. The equivalent RGW coupler that assures the same operation of the hybrid PEC/PMC waveguide at a specific frequency range is deduced based on detailed theoretical aspects. Moreover, a simple analyzing of transitional bends and phase shifters with accurate calculations is presented in this paper, which are the fundamental building blocks of several mmW components such as the six-port junction and the butler matrix. The possibility of tuning the coupler center frequency is introduced without the need of using any nonlinear elements. The resulting RGW couplers are implemented through well-known full wave simulator (Ansoft HFSS), with verification through prototype measurements in order to confirm the validity of the proposed methodology. A good agreement is achieved between measurement and simulation results

4×4 -Element Cavity Slot Antenna Differentially-Fed by Odd Mode Ridge Gap Waveguide

A differential feeding for a cavity slot antenna is presented. The proposed feeding is based on a simple mechanism rather than the traditional complex networks that suffer from high losses. It is based on exciting the first higher order mode (TE10) of the ridge gap waveguide (RGW) by enlarging the ridge width. This enlargement would excite some undesired even modes that are suppressed by inserting a vertical perfectly electric conducting (PEC) wall in the middle of the waveguide based on the concept of magic tee operation. The proposed 4 × 4 cavity slot antenna is implemented using substrate integrated waveguide (SIW) technology. Two horizontal slots on the top of proposed wide RGW, representing the differential feeding approach, are implemented to feed the cavity slot antenna. The slots couple the fields with same amplitudes and 1800 phase difference to the cavity. The electric fields of the two coupling slots have odd symmetry in the x-axis, and subsequently, uniform electric field distribution of the TE440 mode of a cavity can be excited. The 4/4 radiating slots are etched on the top of the cavity in a specific distribution to ensure having in-phase fields for broadside radiation with low-cross-polarization levels. The measurement and simulation results of the proposed cavity slot antenna are in a good agreement. The obtained results confirm that the proposed antenna achieves a relative bandwidth of 7.1% for -10-dB return loss, a gain of about 16.5 dBi, and a side lobe level about -17 dB in E-plane and -13.8 dB in H-plane. Moreover, the proposed antenna provides low cross-polarization levels (-35 dB in E-plane and -27 dB in H-plane) within the operating frequency band of 32.5 to 34.9 GHz. With this achieved low profile, high gain, and high efficiency of the proposed cavity slot antenna, it may have a great potential for millimeter-wave (MMW) applications