Abstract
On board of communication satellites, there are numerous RF filters in the payload used for guiding wanted signals as desired and for rejecting unwanted signals such as not to interfere with wanted signals. At present, satellites have a long lifetime (15 years at least for a typical geostationary communication satellite) and there is also time elapsing between its design and the start of in-orbit service (2 years at least). On the other hand, conventional RF filters for satellite applications are fixed frequency. Therefore, there is a growing demand for in-orbit tunable filters to be able to cope with changes in the market situation during that long time. Also, there are communication systems evolving that rely on tunable devices used for adaptive filtering or steering. This article reports on in-orbit tunable bandpass filters employing liquid crystal material and operating at 20 GHz, and especially on design aspects dealing with the harsh space environment, on the operating principles for commanding the filters on board the satellite, and on a qualification campaign passed successfully. A demonstrator unit is in manufacturing for in-orbit verification.
Highlights
The benefit of tunable filters in communication systems applies to satellite communications, and especially to the payload on the satellite itself
This article reports on in-orbit tunable bandpass filters employing liquid crystal material and operating at 20 GHz, and especially on design aspects dealing with the harsh space environment, on the operating principles for commanding the filters on board the satellite, and on a qualification campaign passed successfully
The test campaign described is a qualification test campaign that was performed on the filter
Summary
The benefit of tunable filters in communication systems applies to satellite communications, and especially to the payload on the satellite itself Such a payload contains numerous RF filters operating mostly in frequency ranges from the L-band (1–2 GHz) to the Ka-band (26–40 GHz) [1]. Dealing with signal strengths from low-RF power levels (in the order of mW) up to power levels as high as 100 W (as needed to transfer the signal back from the satellite to an earth-based receiver). Depending on those exact needs, various filter technologies have developed over the last decades and are routinely manufactured and employed in satellite missions [2]. Obstacles for the introduction of tunable filters are: The lifetime of a geostationary communications satellite is typically fifteen years, and a new technology will only be considered if sufficient confidence has been gained that it will remain functional over this period of time.
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