Dual Polarisation High Power L-Band Feed Chain

Objectives

RUAG Space L-band antenna array elements have been a successful product the last ~15 years. Recently we have noticed that the power requirements on the L-band feed chain will be more stringent in the near future. It is mandatory to secure our role as a supplier in the future and therefore we need to continue the development of our antenna element.

The primary objectives with the proposed ARTES 5.2 developments are:

  • To secure RUAG’s antenna array element product market share for the future,
  • To extend RUAG’s product portfolio by a diplexer, to give a possibility to expand our market with a complete feed chain (antenna element plus diplexer).

For many years, RUAG has delivered circularly polarised patch exited cup (PEC) antenna elements for mobile communication in the L- and S-bands. These PEC antennas have excellent features, such as dual polarisation, low losses, low mass, extremely low PIM levels and good power handling capabilities.

The PEC elements are well adapted to the current system requirements. However, future systems will have increased TX power levels. The issues with the new requirement drivers are challenging.

Challenges

PEC:
The design of the feed network will be the main challenge during the development of the high power PEC element. Increased power levels will cause multipaction and too high thermo-elastic stress. PIM also gets even more critical at higher power levels, especially since the transmit and receive bands shall be somewhat wider than previously.

Diplexer:
There are four major issues to be considered for the diplexer:

  • The need to create a filter structure that efficiently generates adjacent channel rejection to the desired level (up to 120 dB) whilst meeting power requirements.
  • To achieve a practical level of isolation between the two channels so that the high level of rejection is not compromised due to leakage.
  • The need to package the diplexer so that two diplexers can fit within the footprint of the PEC element.
  • To meet the challenges listed above while keeping a mass low enough for a component that shall be used in an array with hundreds of units.

Benefits

Our L-band antenna array elements have been a successful product the last ~15 years. It is mandatory to secure our role as a supplier in the future and therefore we need to continue the development of our antenna element.

The ability to provide diplexers, in addition to the antenna elements, has so far not been that much requested by our customer since they are satisfied with their present supplier. However, taking into account the new power requirements, there is a possibility to aim on the diplexers for us as well. The reason is that the tougher power requirements very much affect not only the antenna element but also the diplexer and the interface between.

The package with a high power version of the L-band antenna array elements and high power diplexers, designed specifically to be used with the antenna elements, reduces the risks and workload for the customer and increases the value for us. It is thus a win-win situation for the parties concerned.

Features

The system contains a PEC element and behind each PEC there is one or two diplexers in order to separate the bands of common receive/transmit port(s) on the antenna. It is also known that future requirements for the diplexer will include increased power levels, more stringent PIM requirements, and lower mass and volume.

The aim for the final product is an L-band PEC element equipped with up to two diplexers. The total footprint shall not be larger than the minimum square that contains the circular rim of the antenna, i.e. approximately 1.10 - 1.25 wavelengths. The product shall be capable of simultaneous RX/TX dual circular polarisation with flexible power allocation, maximum 200 W in total. With such a product in the portfolio, RUAG will be well equipped to meet the needs of its mobile communication array element customers also in the future.

The PEC antenna and the diplexers shall be possible to mount on opposite sides of a common customer interface plate as shown in the figure below.


click for larger image

The ARTES 5.2 activities include design, analysis, and testing of critical components as well as testing of the separate antenna and diplexer elements on EM level.

Plan

The total duration of the ARTES 5.2 program is scheduled to 16 months.

The review plan is as follows:

  • Kick-Off – September 19, 2012 To clarify outstanding issues and clarifications / Formal kick-off of the project.
  • BDR – May 2013 RUAG to present and for ESA to approve the preliminary assessment of equipment performance.
  • MTR – September 2013 RUAG to present and ESA to agree to the design of the equipment.
  • FR – January 2014 Main objective is to present the results of the EM elements test campaign and the outcome of the project.

Current status

We have defined the requirements for the different parts of the assembly and started with the preliminary design of the diplexer as well as the PEC. The preliminary design includes RF performance, mechanical, thermal, PIM and power handling assessments / analyses.

Preparation for the BDR is on-going.

After the BDR a detailed design and BB phase will start with power handling testing of critical components.

Status date

Thursday, December 17, 2015 - 11:35