Design of Millimeter-wave Planar Antenna Arrays

毫米波平面天線陣列的設計

Student thesis: Doctoral Thesis

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Award date11 Sep 2018

Abstract

The wide spectrum in millimeter-wave (MMW) bands supporting multigigabit data rates is attractive. During the past decade, various MMW antennas have been proposed for point-to-point wireless communications and among them, planar antenna arrays with virtues of low profile and good performance in gain and bandwidth demonstrate them a superior candidate. In this thesis, three designs of planar antenna arrays are proposed to operate in the 60 GHz band.

The first design is a linearly-polarized antenna array with a wide bandwidth and high gain. The proposed array has a double-layered structure composed of a PCB on the top layer and an air-filled-waveguide feed network on the bottom layer. On the front surface of the first layer, 16×16 radiating elements are etched and connected by hybrid series/parallel microstrip lines to form sixteen 4×4-element subarrays. Then through the H-shaped slots on the back surface of the first layer, the subarrays are fed by the waveguides underneath. To verify the design, a prototype is fabricated and tested. The experimental results show a maximum gain of 31.6 dBi and a wide bandwidth of 15.8 %. The radiation patterns are symmetrical and unidirectional with cross polarizations less than -25 dB. Our antenna array has only two layers, which is simple in configuration and easy to produce. This antenna can be extended into larger arrays without additional layers to achieve higher gains. 

By reviewing the published studies of high gain planar antenna arrays, it is found that most of the designs are focused on single polarized antennas. The design of arrays with dual polarization properties has not been well explored. In this thesis, a novel dual polarized feed network is proposed and based on it, we design our second and third planar antenna arrays. 

The second antenna array in this thesis is a dual linearly-polarized planar antenna array. The array is composed of cross-slot-coupled cavity-backed square patch antenna elements and a novel substrate integrated waveguide (SIW) network. The advantage of the proposed configuration is that the two polarizations share the common radiating elements and most portions of the feed network so that they exhibit similar performance in terms of the bandwidth, gain and radiation patterns. A 16×16-element array is designed, and the simulated results achieve an overlapped bandwidth (impedance bandwidth and 3dB gain bandwidth) of about 24% from 54 GHz to 69 GHz, a port-to-port isolation exceeding 55 dB and a maximum gain of 31 dBi for both polarizations.

The third design in this thesis is a dual circularly-polarized planar antenna array modified from the second one. An 8×8-element array is designed to demonstrate its function and the simulated data exhibits an overlapped bandwidth (SWR<2, 3-dB-down gain bandwidth and AR<3) of approximately 23%, a gain up to 25.8 dBic for both ports, and a port-to-port isolation larger than 14 dB. Good unidirectional and symmetrical radiation patterns are observed. A prototype is fabricated and the measured results agree with the simulated ones with acceptable disparities. The reported structure is built by conventional PCB technology which is cost-effective. With these advantages, the proposed scalable antenna design is a good candidate for millimeter-wave wireless communications.