Flexible Analog Front Ends of Reconfigurable Radios Based on Sampling and Reconstruction with Internal Filtering
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Flexible Analog Front Ends of Reconfigurable Radios Based on Sampling and Reconstruction with Internal Filtering Yefim S. Poberezhskiy Rockwell Scientific Company, Thousand Oaks, CA 91360, USA Email: [email protected]
Gennady Y. Poberezhskiy Raytheon Company, El Segundo, CA 90245, USA Email: [email protected] Received 27 September 2004; Revised 4 April 2005 Bandpass sampling, reconstruction, and antialiasing filtering in analog front ends potentially provide the best performance of software defined radios. However, conventional techniques used for these procedures limit reconfigurability and adaptivity of the radios, complicate integrated circuit implementation, and preclude achieving potential performance. Novel sampling and reconstruction techniques with internal filtering eliminate these drawbacks and provide many additional advantages. Several ways to overcome the challenges of practical realization and implementation of these techniques are proposed and analyzed. The impact of sampling and reconstruction with internal filtering on the analog front end architectures and capabilities of software defined radios is discussed. Keywords and phrases: software defined radios, reconfigurable and adaptive transceivers, sampling, analog signal reconstruction, antialiasing filtering, A/D.
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INTRODUCTION
Next generation of software defined radios (SDRs) should be reconfigurable to support future wireless systems operating with different existing and evolving communication standards while providing a wide variety of services over various networks. These SDRs should also be extremely adaptive to achieve high performance in dynamic communication environment and to accommodate varying user needs. Modern radios, virtually all of which are digital, do not meet these requirements. They contain large analog front ends, that is, their analog and mixed-signal portions (AMPs) [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]. The AMPs are much less flexible and have much lower scale of integration than the radios’ digital portions (DPs). The AMPs are also sources of many types of interference and signal distortion. It can be stated that reconfigurability, adaptivity, performance, and scale of integration of modern SDRs are limited by their AMPs. Therefore, only radical changes in the design of the AMPs allow development of really reconfigurable SDRs. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
It is shown in this paper that the changes in the AMP design have to be related first of all to the methods of sampling, reconstruction, and antialiasing filtering. It is also shown that implementation of novel sampling and reconstruction techniques with internal filtering [17, 18, 19, 20, 21, 22, 23] will make the AMPs of SDRs almost as flexible as their DPs and significantly improve performance of SDRs. To this end, conventional architectures of the radio AM
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