Technical Field

The present disclosure relates to a broadband quasi-Yagi antenna with a ceramic substrate providing high heat dissipation and low loss.

Background

Quasi-Yagi antennas have been widely used for wireless communications for their properties such as low-cost, easy fabrication process, compact size, lightweight and end fire radiation pattern. A conventional Yagi-Uda antenna consists of a dipole driver in the centre, a single reflector on one side, one or more directors on the other side and a feeding structure. There is always a tradeoff between the gain and bandwidth, with the bandwidth narrowing as more elements are used. To obtain a high gain (~6.5dBi), the typical bandwidth of a conventional quasi-Yagi antenna is relatively narrow (10-20% for VSWR<2), limiting their applications for broadband wireless communications. A wider bandwidth (40-50% for VSWR<2) can be achieved at the cost of reduced gain.

Heat dissipation in small spaces can cause problems for antenna applications with high temperature. Fans, cooler gels etc. are used for removing heat from antenna. Substrate materials have also specific heat and dissipation capacities that determine heat absorbing and dissipating level of the material. Therefore, many different materials are used as a substrate in Yagi antenna applications. Some of them provides high gain in bandwidths out of broadband with low heat dissipation. On the other hand, high temperature may adversely affect, including stopping or causing them to draw excessive current, integrated circuits and chips in antenna system.

The application numbered WO2016155393A1 offers a dielectric antenna element, such as Yagi, for emitting or receiving radio frequencies. In an embodiment the dielectric antenna element includes a substrate, a microstrip element supported by the substrate, and at one first dielectric superstrate disposed over the substrate and spaced apart from the substrate. However, this structure has similar flaws explained above such as high temperature, stopping working risk etc. Summary

The invention aims to use a ceramic substrate that has high dielectric constant brings high heat dissipation and gain properties to broadband quasi-Yagi antenna applications.

On the other hand, coating can be well adhere to ceramic substrate and thus side lobe signals are avoided.

In a preferred embodiment, ceramic substrate is an Alumina (AI203), in other words Aluminum oxide, one of the most cost effective and widely used material in the family of engineering ceramics.

Brief Description of the Drawings

Figure 1 shows the measured simulated and measured return loss of four-element array and measure total gain of four-element array respectively.

Detailed Description

The detailed information is presented on the design and performance of a broadband quasi- Yagi antenna onto the ceramic Alumina (AI203 - %99,6), which provides availability in high temperature applications and compact size. Broad bandwidth (measured 52% for VSWR < 2), good radiation profile (front-to-back ratio >12db) and total gain (4-5 dbi) have been achieved with a single antenna element. It should be noted the qualities are maintained across the entire bandwidth. In addition, the mutual coupling characteristics of the quasi-Yagi elements in the array is observed to be very low.

A thin layer of sputtered Titanium Tungsten (TiW) is used as an adhesive interlayer between upper layer and alumina in thin film application. The thicknesses approximately Titanium Tungsten is 50 nm. For the resistor layer, Tantalum Nitride (TaN) is used with thickness 150 nm approximately. This production method is a special technique that helps to produce lines and devices with sensitivity of 500nm by using devices such as sputter coater, argon plasma for the minimum width of the whole structure drawings while working on the ceramic wafers. These are the reasons for using Thin Film technology.

The current design consists of two director elements. In preferred embodiments, additional elements are used for improving gain or bandwidth. Flowever, this also increases the number of design parameters as well as the complexity of design optimization and additional spaces that is the most significant parameter for thin ceramic substrates. Additional directors provide more gain for the system however on the understanding that bandwidth.

A simple equal amplitude four-element linear array is used to supply maximum gain requirements. Total producible area of one ceramic substrate is 80mm by 80mm so this is the restriction. One array antenna has been designed only for one phase the results are calculated. Measuring and simulated results were compared between. Each element and the divider designed and fabricated onto the same substrate, Alumina AI203. The measured S parameters of the structure are shown in Figure 1.

In a light weight planar design and performance at high temperature applications antenna printed on a ceramic substrate has great advantages. The great radiation properties and compact size of this antenna make it ideal. A single quasi Yagi antenna and four-element array are fabricated on an Alumina substrate. The final size of the antenna array is 75mm x 30mm with the thickness is about 0.635mm. The antenna can be made by a both side printed circuit with simple structure with thin film manufacturing technology. The number of array elements can be increased and controlled all the phases in the radar applications.