Design of High-performance Planar Antenna Arrays for Millimeter-wave Applications


Student thesis: Doctoral Thesis

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Award date20 Aug 2021


This thesis presents a series of high-performance planar antenna arrays for millimeter-wave applications. High-gain antenna arrays are popular in millimetre-wave wireless communications since it can compensate for the high propagation attenuation in millimeter-wave frequencies. It is a challenge to design high-gain antenna arrays with a wide operating bandwidth, high radiation efficiency, stable unidirectional pattern, and a simple structure. In this thesis, novel feed networks and antenna elements are developed and combined to contribute to high-performance arrays. Several elements that contribute to a wide band and high gain, such as the combination of patches and a magneto-electric (ME) dipole, a C-shaped open slot, and an 11-element microstrip patch subarray, are proposed to develop the antenna arrays for the first time. The pillbox-distributed feed and full-corporate feed networks are used to excite these elements. The overall performance of the proposed arrays was significantly improved by introducing these novel antenna elements and feed networks.

Firstly, a planar millimeter-wave antenna array with a pillbox-distributed network is studied. The antenna element in this array is the combination of an ME dipole and microstrip patches; this pairing results in significant improvements in operating bandwidth and radiation gain. A pillbox transition is adopted as a part of the feed network to deliver equal-phase power distribution to 10x4 antenna elements. The time-domain analysis approach is applied to analyze the transmission loss in different sections of the feed network. The final prototype of the antenna array achieves an impedance bandwidth of 30.7% from 53 to 72.2 GHz where the reflection coefficient is smaller than -10 dB and a maximum gain of 25.1dBi at 68 GHz.

Secondly, a wideband and high gain antenna array with side-lobe suppression and multi-beam radiation is investigated. The pillbox-distributed network and the non-uniform full-corporate feed network are combined together to generate an unequal power distribution, which significantly reduces the side-lobe level in the E-plane. The slot-coupled ME dipole is used as an antenna element to integrate the feed network and enhance the impedance bandwidth. The multi-beam radiation of the array is demonstrated by placing feed ports at different positions in the focal plane of the parabolic reflector.

Thirdly, in order to establish a wide band and high gain antenna array with fewer printed circuit board (PCB) layers, a C-shaped open slot element is used to design the antenna array. The slot radiator consists of two C-shaped apertures that generate a pair of folded magnetic dipole radiations. From the simulated results, this slot radiator has an impedance bandwidth of 39.8% from 21.7 to 32.5 GHz with a peak gain of 12.5 dBi at 29 GHz. The 4x4 and 8x8 antenna arrays fed by the SIW full-corporate feed network are demonstrated on two-layer PCBs. The measured results show that the 8x8 array obtains a wide impedance bandwidth of 37.1% from 21.3 to 31 GHz and a maximum gain of 28.3 dBi at 29 GHz.

Finally, the hollow waveguide-fed microstrip patch antenna arrays are investigated for submillimeter-wave applications. The subarray technique is adopted to reduce the complexity of the feed network. The subarray consists of 11 patch elements, and it is fed using the coupling slot on the hollow waveguide. The 1-to-8 hollow waveguide feed network is used to excite eight subarrays with small transmission losses. The sensitivity analysis for the parameters is implemented to obtain the required fabrication tolerance. The measured results proved that the proposed MPA array can operate from 150 to 205 GHz with a reflection coefficient below -10 dB and with a maximum gain of 21.9 dBi. Additionally, an array consisting of 32 subarrays and a 1-to-32 hollow waveguide is designed at 270 GHz, which achieves a gain up to 29.8 dBi.