Abstract
AbstractSevere RF spectrum limitations imposed by international regulations make filtering, and principally channel filtering, a key parameter of the mobile satellite service. About 30 MHz is available at L‐band for maritime, aeronautical and land mobile users, and must be shared between all potential service providers! Furthermore, this band must also accommodate signals with characteristics as dissimilar as: data at low and high bit rates, digital and analogue voice. Even worse, the transmissions are to be done with different categories of users, having terminals with G/T in the range of −4 to −24 dB/K.If the satellite payload provides a global earth coverage the RF spectrum will have to be channelized so that the various types of signals can be efficiently handled. This is what happens in the return transponder of the INMARSAT second‐generation satellite.If, as anticipated for future mobile satellite systems, spot beams are implemented, further channelization becomes necessary to provide the maximum of flexibility in the channel to beam allocation.In either case, a minimum of bandwidth can be wasted in the guardbands, while at the same time hardly any distortion is to be tolerated in the useful passband.The present article will illustrate, with two examples, how these drastic filtering requirements can be best fulfilled with surface acoustic wave technology.
Published Version
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