The Designs of Printed Antennas for Millimeter Wave Band from 30 to 300 GHz

Abstract

This thesis intends to provide the comprehensive investigation on printed antenna technologies for the frequency spectrum from 30 to 300 GHz. Printed circuit broad (PCB) technologies have been employed and developed for low frequency antenna manufacturing. The manufacturing accuracy of PCBs is sufficient for implementation in microwave band antennas both in terms of functionality and low-cost. When the operating frequency of the antenna moves to the millimeter-wave spectrum, antenna fabrications are required to have high precision tools and low-loss materials. However, the drawbacks are low-yield rate and high cost. In this thesis, we showcase four antenna designs using low-cost microwave substrate and fabricated with the use of generic PCB fabrications to realize millimeter-wave radiating elements with excellent electrical characteristics such as wideband, high gain, low cross polarization, and low back radiation. The contents of this thesis are as follows.
In Chapter 1, introduces the background of the investigation on millimeter-wave antennas and arrays. It also provides a review of previous studies on antenna technologies relevant to the work of this thesis. It also describes the importance of gain enhancement for a single element in which and how to manipulate the proposed gain enhancement methods in the design. Three different gain methods are proposed. It discusses how to achieve the proposed antenna design using generic printing substrate techniques.
In Chapter 2, a printed vertical patch antenna is introduced. By using plated-through-hole (PTH) technology, a vertical conductive via hole is embedded into the microwave substrate functions as a radiating element that successfully demonstrates and operates at millimeter- wave band level. This proposed work is further extended to feature 33, 60 and 100 GHz antenna elements. Simulated and measured results show that 33GHz and 60 GHz proposed antennas have wide impedance bandwidths, stable radiation patterns across the operating bandwidth, and good broadside gains.
In Chapter 3, a new complementary sources technique applied to millimeter-wave antennas is introduced. The proposed technique can widen the impedance bandwidth of the antenna and enhance the antenna gain for a single antenna element through the combination of two complementary sources. A planar electric dipole (source 1) is printed on a microwave substrate and a vertically-oriented shorted patch (source 2) is realized by PTH on the substrate. These two sources are excited by a V-type SMA launcher such that equivalent electric and magnetic radiations are generated. Simulated and measured results of the characteristics of the input impedance, SWR and the gain are then presented. The result shows that the antenna has an impedance bandwidth of 33%. Stable radiation patterns with low cross polarizations are achieved across the entire operating bandwidth. The antenna has a maximum gain of 7.5 dBi on its broadside direction.
In Chapter 4, the scope of complementary sources technique is extended. A new stacked structure of complementary antenna is proposed which utilizes a coplanar waveguide (CPW) -fed slot antenna to act as a magnetic source and a parasitic dipole acts as an electric source. Detailed studies for element spacing, dipole shapes, slot width and substrate thickness are given. Simulated and measured results of the input impedance, SWR and the gain are presented. The antenna can achieve a peak gain of 12.2 dBi at 65 GHz and an average gain of 10 dBi across the passband.
In Chapter 5, another form of complementary source in the form of a feed is applied to a printed reflector-backed Fresnel zone plate antenna. Firstly, a characterization of dielectric properties of microwave substrate in terahertz range is conducted. This antenna operates at 300 GHz with equal E- and H- plane radiation patterns. It has a rotationally symmetric radiation pattern. Its measured peak gain is 24.8 dBi at 287 GHz. Moreover, under the same F/D ratio, we re-design the reflector with the addition of a circular grating pattern. We see a 0.8 dB gain enhancement in peak-to-peak gain comparison. The measured gain is 25.88 dBi at 308.7 GHz.

Date of Award	25 Jan 2016
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Chi Hou CHAN (Supervisor)