Research On Millimeter-wave Planar Form Phase Shifter

With the rapid development of wireless devices and wireless applications, there is a growing demand for high-speed data services. In order to meet the future demand for large-capacity communications, phase control technology, which is traditionally used in military and scientific fields, is applied to wireless communications. Phase shifter is the core component of phase control system. In this paper, we mainly study the planar form phase shifter and phase-shifting network which are applied to the millimeter-wave wireless communication frequency. Our research including the following three aspects:Firstly, based on the characteristics of millimeter-wave mobile communication, we proposed a succinct and effective design strategy for millimeter wave frequency applications. The design method is based on two simple loaded microstrip line structures for below 90° phase shift and 180° phase shift respectively. The method aims at achieving minimum phase error around center frequency. Theory analysis shows that up to fourth-order derivative of phase shift with respect to frequency can be 0 at center frequency, which means phase shift is very flat around center frequency. Besides, constant 90° and 180° phase shift can be achieved theoretically. By using the method, the designed 90° and 180° phase shifters have small phase shift deviations. The measurement shows good results: for the 90° phase bit, the measured return loss and insertion loss are better than 10 dB and less than 1.1 dB from 24.8 GHz to 35.7 GHz. The phase shift is 90.3° ± 3° over this operating bandwidth. For the 180° phase bit, the measured return loss and insertion loss are better than 10 dB and less than 1.48 dB from 24.4 GHz to 32.35 GHz. The phase shift is 181.6°±4.6°over this operating bandwidth.Secondly, a novel grounded dielectric waveguide (GDWG)combining substrate integrated waveguide (SIW) and traditional GDWG is presented and explored. Based on the theoretical results, a new phase shifter composed of a GDWG phase shift part and a simple SIW reference part is proposed. Two different types of waveguide are directly used to generate flat phase shifts creatively. Which makes the proposed phase shifter very concise and easy to design. To demonstrate the utility of the proposed technique, a 90° phase shifter is designed within the frequency band from 25GHz to 35GHz. The measurement results show that the designed 90° phase shifter has better than ±2.4° phase stability, less than 1.1 dB insertion loss and better than 13 dB return loss within the desired frequency range.Thirdly, through electromagnetic simulation, we designed and realized an orbital angular momentum (OAM) mode multiplexing antenna which is integrated on a single printed circuit board (PCB). The designed system consists of an 8×8 Butler matrix, a phase compensation structure and an 8-element circular antenna array. A total of seven OAM modes (0,±1,±2, and ±3) can be generated and multiplexed. The 8 × 8 Butler matrix is the core of this system. It is used to generate the phase gradient corresponding to different OAM modes. The designed 8 × 8 Butler matrix is a new SIW-based layout that was first proposed. By using two-layer 90°3dB directional coupler and two-layer layout, the crossovers and the last stage of directional couplers can be achieved at the same time. With this configuration, many crossovers can be avoided and flat 90 ° phase shift can be obtained. In addition, we also used self-compensation phase shift structure to achieve a flat phase shift. With this new Butler matrix, we have implemented the integration of the entire OAM mode multiplexing antenna on a single PCB board for the first time.