Phase shifters are components that play a very important role in microwave applications such as phase-array antenna systems, phase-modulation communications systems and others. The phase shifters are used to introduce phase tapers in the radiating elements of an array to scan the beam of the radiating elements in the desired direction. Phase shifter designs have a long history. The first differential phase shifter is the Schiffman phase shifter, which uses an edge-coupled strip line section (see O. Kramer, T. Djerafi, and K. Wu, “Dual-layered substrate-integrated waveguide six-port with wideband double-stub phase shifter,” IET Microw. Anten. Propag., vol. 6, no. 15, pp. 1704-1709, 2012). Later many researchers devoted their attention to enhancing the performance of phase shifters. In A. Tribak, A. Mediaville, J. Zbitou and J. L. Cano, “Novel ridged waveguide differential phase shifter for satellite application,” Inter. Jour. of Microw. and Opt. Techno., vol. 9, no. 6, pp. 409-414, November 2014, a wideband two-layered SIW six-port was designed to operate over the V-band. It exhibits good performance, but over a very narrow bandwidth. M. X. Xiaoao, S. W. Cheung, and T. I. Yuk, “A C-band wideband 360° analog phase shifter design,” Microw. and Opt. Techn. Let. vol 52, no 2, p. 355-359, February 2010 describes broadband differential phase shifters using bridged T-type bandpass networks. The proposed phase shifter network can improve the bandwidth of phase error while keeping good return loss. Another approach using a multi-layered phase shifters for 60 GHz WPAN applications and a mm-wave MEMS phase shifter based on a slow wave structure have been described in G. M. Rebeiz, G.-L. Tan, and J. S. Hayden, “RF MEMS phase shifters: design and applications,” IEEE Microw. Maga., vol 3, no 2, p. 72-81, June 2002, and P. Yaghmaee, O. H. Karabey, B. Bates, C. Fumeaux, and R. Jakoby, “Electrically Tuned Microwave Devices Using Liquid Crystal Technology,” Inter. Jour. of Anten. and Propag., vol. 2013, pp. 1-10, September 2013, respectively. Despite extensive research to improve the design and performance of the phase shifter, the search for low-cost phase shifters, which provide one- or two-dimensional scan capability to fixed-beam array antennas at millimeter waves that are finding widespread use at millimeter waves for fifth generation (5G) communication, continues unabated.
Phased array antennas are widely used for beam scanning applications in communication systems. It is well known that conventional phase shifters utilized in these applications are lossy, bulky and costly. Extensive research has been carried out in recent years for designing phased array antennas, especially in the context of satellite communication applications, and the design of civilian radar-based sensors. A number of different approaches have been proposed for scanning the beams of phased array antennas for these applications. Most of these approaches call for biasing configurations that are needed, either for activating certain switches, e.g., pin diodes or varactor diodes, or for modifying the electrical properties of materials, in order to realize the desired phase-shift when integrated with the antenna elements of the array.
As noted above, scanning arrays play a key role in 5G applications and satellite communication, and phase shifters are key components of these arrays. It is highly desired that the phase shifter be light weight, have low profile and that it provides a wide-angle scan capability. In Z. R. Omam, W. M. Abdel-Wahab, A. Raeesi, A. Palizaban, A. Pourziad, S. Nikmehr, S. Gigoyan, and S. Safavi-Naeini, “Ka-Band Passive Phased-Array Antenna With Substrate Integrated Waveguide Tunable Phase Shifter,” IEEE Transactions on Antennas and Propagation., vol. 68, no 8, pp. 6039-6048, August 2020, there is described a low-cost array antenna using a continuously tunable substrate integrated waveguide (SIW) phase shifter. In Y. Zhu, R. Lu, C. Yu, and_W. Hong, “Design and Implementation of a Wide band Antenna Subarray for Phased Array Applications,”. IEEE Transactions on Antennas and Propagation., vol. 68, no. 8, pp. 6059-6068, August 2020, there is proposed a multilayer structure to design a wideband antenna subarray for phased array applications. Additionally, K. Tekkouk, M. Ettorre, and R. Sauleau, “SIW Rotman Lens Antenna With Ridged Delay Lines and Reduced Footprint,” IEEE Transactions On Microwave Theory And Techniques, vol. 66, no. 6, pp. 3136-3144, June 2018 proposed a method based on SIW Rotman Lens Antenna to achieve results in scanning on an angular sector of about ±48°. But these proposed designs are still bulky, difficult to fabricate and they need many excitation ports.
An aspect of the invention is to provide low-cost phase shifters that help mitigate the problems of lossiness, bulkiness, and costliness. The inventors propose a phase shifter design which totally bypasses ferrite-based conventional phase shifters that are both costly and highly lossy at millimeter waves. Instead, embodiments of the invention use a new technique based upon the fact that the propagation constant in the waveguide varies as a function of the width of the guide.
According to an embodiment of the invention, a phase shifter is inserted between two radiating elements in a substrate integrated waveguide (SIW) in order to realize the desired phase taper between the elements. This enables the array to generate multiple beams which scan the space to cover the desired angular range.
A particular goal of this invention is to provide a new design for a beam scanning array antenna, which has the advantages of low cost, low profile and ease of manufacturing.
A lightweight, low profile array antenna with wide-angle scan capability is desired for the rising demands of 5G communication. To address the design challenge, the inventive phase shifter utilizes a curved substrate integrated waveguide. The proposed design utilizes physics which is totally different from the design that forms the basis of legacy phase shifting devices, e.g., ferrite phase shifters. The low-cost phase shifter may be integrated in 5G communication systems.
The effective width of the straight sections of the SIW waveguide is “a” (see
“a” and “b” are close to half wavelength to make an acceptable side lobe level and c and e are optimized to keep the reflexion coefficient under −10 dB for all phase shifters. The propagation constant in the waveguide varies as a function of the width of the guide. If the value of the width of the guide is changed, the resonance frequency varies because the propagation constant varies.
In
In the fabrication process the curved SIW with slots, but without any phase shifters, is preferably produced first as shown in
Another alternative phase shifter design is shown in
The proposed general design shown in
The proposed design utilizes physics which is totally different from the design that forms the basis of legacy phase shifting devices, e.g., ferrite phase shifters. A desired phase shift can be achieved by varying the configuration of the vias inserted in the curved sections of the waveguide. As noted above to have mutually exclusive combinations of being filled with a liquid metal or being devoid of filling by a liquid metal. Varying the configuration of the vias, in turn, changes the propagation constant within the guide and thus achieves different electrical lengths of the curved sections of the SIW guide, even though their physical lengths remain unchanged. The via patterns inside the curved web guide sections are reconfigured to realize different phase. It is possible after configuring the control mechanism of the wave propagation in the guide to have mutually exclusive combinations of being filled with a liquid metal or being devoid of filling by a liquid metal.
In some embodiments, as shown in
The novel proposed microwave scanning array system offers “low-cost” platforms that can be ground-based or mounted on mobile platforms, e.g., airplanes, ships and buses for SATCOM systems. The main beneficiary of the proposed scanning array system will be broadband mobile communication industry because the proposed “low-cost” platforms can be ground-based or mounted on mobile platforms, e.g., airplanes, ships and buses for SATCOM systems offering broadband, wide connectivity, high capacity, high speed data transfer, without using conventional ferrite type phase shifters that can be prohibitively costly as well as lossy. The phase shifting system can be fabricated relatively easily using existing electronic components and it is both low loss and relatively low cost.
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