Flexible Frequency Discrimination Subsystems for Reconfigurable Radio Front Ends
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Flexible Frequency Discrimination Subsystems for Reconfigurable Radio Front Ends Bruce E. Carey-Smith Centre for Communications Research, University of Bristol, Bristol BS8 1UB, UK Email: [email protected]
Paul A. Warr Centre for Communications Research, University of Bristol, Bristol BS8 1UB, UK Email: [email protected]
Phill R. Rogers Centre for Communications Research, University of Bristol, Bristol BS8 1UB, UK Email: [email protected]
Mark A. Beach Centre for Communications Research, University of Bristol, Bristol BS8 1UB, UK Email: [email protected]
Geoffrey S. Hilton Centre for Communications Research, University of Bristol, Bristol BS8 1UB, UK Email: geoff[email protected] Received 8 October 2004; Revised 14 March 2005 The required flexibility of the software-defined radio front end may currently be met with better overall performance by employing tunable narrowband circuits rather than pursuing a truly wideband approach. A key component of narrowband transceivers is appropriate filtering to reduce spurious spectral content in the transmitter and limit out-of-band interference in the receiver. In this paper, recent advances in flexible, frequency-selective, circuit components applicable to reconfigurable SDR front ends are reviewed. The paper contains discussion regarding the filtering requirements in the SDR context and the use of intelligent, adaptive control to provide environment-aware frequency discrimination. Wide tuning-range frequency-selective circuit elements are surveyed including bandpass and bandstop filters and narrowband tunable antennas. The suitability of these elements to the mobile wireless SDR environment is discussed. Keywords and phrases: software-defined radio, tunable antenna, reconfigurable front end, MEMS, tunable bandpass filter, tunable bandstop filter.
1.
INTRODUCTION
The intention of software-defined radio (SDR) is to provide a flexible radio platform capable of operating over a continuously evolving set of communications standards and modes. In contrast to the majority of currently available
mobile telephones, which are predefined to operate on a fixed number of standards, SDR must be capable of adapting to both current and future mobile telecommunications standards [1]. The SDR concept imposes demanding requirements on the transceiver front end.1 Current spectrum allocations and recent regulatory reforms (e.g., [2]) suggest
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1 The front end is that part of the radio which performs channelisation and up- and down-conversion. These functions may be performed in either the analogue or digital domain.
Flexible Subsystems for Radio Front Ends that transceiver operation from 600 MHz to 6 GHz will be required to cover existing and emerging telecommunication services.2 The front end must not only be capable of operating across th
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