Analysis and Design of a Wideband Coaxial Transition to Metal and Printed Ridge Gap Waveguide

In this paper, a wideband coaxial to ridge gap transition is proposed and implemented. The transition has a compact size, wide bandwidth, and simple structure. It can be used to excite ridge gap waveguides implemented by the printed circuit board or computer numerical control (CNC) technologies. A similar circuit model for a coax-to-microstrip junction is proposed and used to establish a systematic design procedure for the proposed transition. Perfect electric conductor and perfect magnetic conductor (PMC) boundaries are used to make the procedure independent of the fabrication technology. The PMC is replaced by a bed of nails for ridge gap realized by CNC technology and mushroom-shaped structure in the case of PCB technology. The proposed transition based on the PCB technology is fabricated and measured. There is a good agreement between simulated and measured results which validates the proposed design. The transition has a 59.22% bandwidth with S11−0.5 dB

Wideband Printed Ridge Gap Rat-Race Coupler for Differential Feeding Antenna

In this paper, a wideband 3 dB hybrid 180° rat-race coupler is introduced in the printed ridge gap waveguide technology. It has simultaneous wide matching and isolation bandwidth with low output amplitude imbalance. It operates in the millimeter wave band from 25.8 to 34.2 GHz (27.96%) with 15 dB return loss and isolation, and ±0.5 dB output amplitude imbalance. The proposed design employing an open stub at the middle of the 3λ/4 branch line and quarter wavelength lines at all the ports of the coupler. The objective of the added open stub is to separate the output ports amplitudes around the -3 dB level by certain values depending on the required amplitude imbalance. The analytical derivation for the role of the added open stub is presented along with a parametric study on its effect on amplitude imbalance, matching, and isolation. This results in having two intersection points for the output ports instead of one of the conventional coupler and hence the amplitude imbalance bandwidth increases. The objective of the added quarter wavelength lines is to improve the matching and isolation bandwidths. First, the conventional rat-race coupler is presented and a bandwidth of 14.25% at 30 GHz is achieved. After that the rat-race with the added quarter wavelength lines is presented to illustrate the objective of the added quarter wavelength lines and a bandwidth of 19.44% is achieved. Finally, the rat-race with the quarter wavelength lines and the added stub is presented and a prototype is fabricated and measured. The s-parameters measurements are in a good agreement with the simulated ones

30 GHz Broadband Bow-tie Printed Ridge Gap Waveguide Antennas

The development of wireless and satellite communication systems has led to high demand for microwave and millimeter wave application components, which play an essential role in the upcoming 5G communication. The coverage area of such systems is control by transmitted power as well as the antenna gain of the system. Hence, it is essential to design a high gain antenna that can mitigate the losses and extend the system coverage area. Higher frequencies lead to smaller sizes of RF components including antennas. However, the implementation of passive components and guiding structure becomes difficult based on traditional guiding structures such as microstrip lines, and waveguides at millimeter wave bands. Microstrip line suffers from cavity modes, which leads to surface waves and has more losses at higher frequencies. The rectangular waveguide has high power handling capability, low losses, and high Q-factors which makes it very attractive for high-frequency applications. On the other hand, at high frequencies, the wavelengths become challenging to construct with current machining techniques as ensuring good electrical contact become very challenging. In this thesis, planar high gain antennas are designed based on Printed Ridge Gap Waveguide (PRGW). The primary objective of this work is to develop high gain, wideband antennas that can support the future demand for high data transmission. Therefore, a detailed analysis for PRGW has been introduced as well as featured designs of the high gain antenna. This antenna array can perform for future 5G communication purpose, and it fulfills all the requirements of mm-wave bands. In this work, a groove-based wideband bow-tie slot antenna array is designed at 30 GHz based on printed ridge gap waveguide technology (PRGW). A two-section T-shaped ridge is designed to feed a bow tie slot placed on the upper ground of PRGW. The gain of the proposed slot antenna is enhanced by using a horn-like groove. Then, the proposed high gain element is deployed to build up a 1 x 4 bow-tie slot antenna array loaded with three-layer groove antenna. The proposed antenna array is fabricated and measured, where the measured results show a -10 dB impedance bandwidth from 29.5 to 37 GHz (22%). The fabricated prototype achieves a high gain of 15.5 dBi and a radiation efficiency higher than 80% over the operating frequency bandwidth. Besides, to reduce the edge diffraction in the E-plane, an artificial corrugation ring is deployed with a certain depth so that it can improve the overall antenna performance

Millimeter-Wave Components and Antennas for Spatial and Polarization Diversity using PRGW Technology

The evolution of the wireless communication systems to the future generation is accompanied by a huge improvement in the system performance through providing a high data rate with low latency. These systems require access to millimeter wave (mmWave) bands, which offer several advantages such as physically smaller components and much wider bandwidthcomparedtomicrowavefrequencies. However, mmWavecomponentsstillneed a significant improvement to follow the rapid variations in future technologies. Although mmWave frequencies can carry more data, they are limited in terms of their penetration capabilities and their coverage range. Moreover, these frequencies avoid deploying traditional guiding technologies such as microstrip lines due to high radiation and material losses. Hence, utilizing new guiding structure techniques such as Printed Ridge Gap Waveguide (PRGW) is essential in future mmWave systems implementation. ThemainpurposeofthisthesisistodesignmmWavecomponents,antennasubsystems and utilize both in beam switching systems. The major mmWave components addressed in this thesis are hybrid coupler, crossover, and differential power divider where the host guidingstructureisthePRGW.Inaddition,variousdesignsfordifferentialfeedingPRGW antennas and antenna arrays are presented featuring wide bandwidth and high gain in mmWave band. Moreover, the integration of both the proposed components and the featured antennas is introduced. This can be considered as a significant step toward the requirements fulfillment of today's advanced communication systems enabling both space and polarization diversity. The proposed components are designed to meet the future ever-increasing consumer experience and technical requirements such as low loss, compact size, and low-cost fabrication. This directed the presented research to have a contribution into three major parts. The first part highlights the feeding structures, where mmWave PRGW directional couplers and differential feeding power divider are designed and validated. These components are among the most important passive elements of microwave circuits used in antennabeam-switchingnetworks. Different3-dBquadraturehybridcouplersandcrossover prototypes are proposed, featured with a compact size and a wide bandwidth beyond 10 % at 30 GHz. In the second part, a beam switching network implemented using hybrid couplers is presented. The proposed beam switching network is a 4 × 4 PRGW Butler matrix that used to feed a Magneto-electric (ME) dipole antenna array. As a result, a 2-D scanning antenna array with a compact size, wide bandwidth, and high radiation efficiency larger than84%isachieved. Furthergainenhancementof5dBiisachievedthroughdeployinga hybridgainenhancementtechniqueincludingAMCmushroomshapesaroundtheantenna array with a dielectric superstrate located in the broadside direction. The proposed scanning antenna array can be considered as a step toward the desired improvement in the data rate and coverage through enabling the space diversity for the communication link. The final activity is related to the development of high-gain wide-band mmWave antenna arrays for potential use in future mmWave applications. The first proposed configuration is a differential feeding circular polarized aperture antenna array implemented with PRGW technology. Differential feeding antenna designs offer more advantages than single- ended antennas for mmWave communications as they are easy to be integrated with differential mmWave monolithic ICs that have high common-mode rejection ratio providing an immunity of the environmental noise. The proposed differential feeding antenna array is designed and fabricated, which featured with a stable high gain and a high radiation efficiency over a wide bandwidth. Another proposed configuration is a dualpolarized ME-dipole PRGW antenna array for mmWave wireless communication. Dual polarizationisconsideredoneofthemostimportantantennasolutionsthatcansavecosts and space for modern communication systems. In addition, it is an effective strategy for multiple-input and multiple-output systems that can reduce the size of multiple antennas systems by utilizing extra orthogonal polarization. The proposed dual- polarized antenna array is designed to achieve a stable gain of 15 ± 1 dBi with low cross- polarization less than -30 dB over a wide frequency range of 20 % at 30 GHz

High Gain Broadband mm-wave Antennas and Beamforming for Wireless Communication Systems

Generating multi-beams along with having broadband and beam steering capability in the mm-waves band are of crucial importance for diverse applications such as remote piloted vehicles, satellites, collision-avoidance radars, and ultra-wideband communications systems. Besides, the propagation environment at millimeter wave (mm-wave) frequencies—suggested for the next generation of wireless networks (5G)—lends itself to a beamforming structure wherein antenna arrays are required in order to obtain the necessary link budget and to overcome the associated strong attenuation. Therefore, the design of high gain antennas (to focus the directive beam to a user) and beamforming networks (to reduce interference) are essential and are needed to address many challenges associated with 5G wireless communications. This work addresses the design and development of high-performance Quasi-Yagi antenna and Rotman lens-based beamforming networks. Accordingly, several issues are addressed in this thesis. A Quasi-Yagi antenna with a perturbed dielectric lens that is broadband and has high gain is designed, optimized, fabricated and tested at 30 GHz. The antenna provides 95% aperture efficiency with a measured gain of 15 dBi as well as a radiation efficiency of ~90% at 30 GHz and a broadband (24-40 GHz) for |S_11 |<-10 dB. The designed end-fire antenna, with its low-profile and compact size, is a good candidate for many applications in the mm-wave band. An optimum and accurate methodology for designing Rotman lens-based mm-wave analog beamforming network (BFN) is presented. The simulation and measurement results showed good beamforming capabilities as well as a scanning range of 80° in the azimuth plane, and, also, good matching at the array ports. The maximum phase error is ±6.6°, and the main beam of the proposed BFN points at seven different angular directions that cover the range of ±40°. The maximum achieved realized gain is 14 dBi at 28 GHz for the center beam. An analog Rotman lens-based BFN using RWG technology, integrated with the excitation ports and the antenna array elements, was designed, simulated, manufactured, and measured. The proposed integrated system is realized using the metallized 3D-printing technology, in order to reduce the implementation cost of the full metal RGW Rotman lens. The measured results demonstrate that the system scan range equals ±39.5º over a wideband 27.5-37 GHz decreases to 30º in the band 37-40 GHz. The BFN bandwidth for VSWR < 2 is larger than 38% and is limited by its single antenna element