Lightweight patch antennas suited for space applications

By Chunwei Min, Nick Howland & Nick Potts of Printech Circuit Laboartories.

Introduction

Patch antennas are commonly used in space applications. They are typically fabricated on fibre-glass reinforced resin or polytetrafluoroethylene -based laminates using standard PCB process. Reinforcements with higher relative permittivity (εr) are usually needed to offer adequate mechanical strength for rigid laminates. This degrades radiation efficiency of patch antennas due to the fact that less fringing fields can be coupled to the space.

The use of low-εr materials may be unavoidable for applications where antenna designs with either high gain or broadband is required. Nevertheless, low-εr materials are, in many cases, soft and structurally weak, and may deform when bonded into PCBs, resulting in lower tolerance and higher risk of failure. The composite PCB is therefore introduced to address the trade-offs to ensure an efficient design with adequate mechanical strength.

One reliable configuration is the integration of Nomex honeycomb and PCBs. The Nomex honeycomb is made of resin-infused fibre papers, and formed into honeycomb structure. Given the mechanical requirements, cavities of the structure can be either filled with resin, or left as hollow with air when bonded with other reinforcements. Patterns can be deposited on standard PCBs for planar designs, or flexible ones for conformal structures. Antenna design requirements, such as miniaturisation, bandwidth enhancement, gain improvement, polarisation control, multi-band techniques, mutual coupling reduction, can be achieved and implemented using the proposed configuration. The antenna can be readily integrated with 3D conformal structures, such as radomes, polarisers and high-impedance surfaces into a single module for various requirements and applications.

In this work, a series of microstrip patch antennas for small satellite platforms are fabricated on both PTFE laminates and the proposed composite configuration using air-filled honeycomb and flexible PCBs to investigate their performance at GPS, GLONASS and S-bands. Analysis and designs of patch antennas on composite PCBs are given, followed by their applications of miniaturised techniques. The proposed designs are considerably light weight, yet providing rigidity and good thermal strength. The measured results of both builds are compared and improvements noted have shown that the proposed configuration is found to be rather suitable for the application.

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