Abstract
This paper explores passive switched capacitor based RF receiver front ends for spectrum sensing. Wideband spectrum sensors remain the most challenging block in the software defined radio hardware design. The use of passive switched capacitors provides a very low power signal conditioning front end that enables parallel digitization and software control and cognitive capabilities in the digital domain. In this paper, existing architectures are reviewed followed by a discussion of high speed passive switched capacitor designs. A passive analog FFT front end design is presented as an example analog conditioning circuit. Design methodology, modeling, and optimization techniques are outlined. Measurements are presented demonstrating a 5 GHz broadband front end that consumes only 4 mW power.
Highlights
With the growth of the wireless industry, the spectral congestion caused by wireless user traffic has become a significant concern that threatens further growth of the technology [1, 2]. This congestion is a result of suboptimal frequency usage arising from the inflexibility of the spectrum licensing process. This inefficiency in spectrum allocation can be solved by allowing spectrum sharing using the concept of a cognitive radio (CR), an intelligent device that is able to dynamically adapt and negotiate wireless frequencies and communication protocols for efficient communications
Stitching the frequency domain information from several scans is imperfect in the face of multipath; signals spanning across multiple scan bandwidths are imperfectly reconstructed
This use of RF samplers and subsequent discrete time processing provide a number of advantages in deep submicron CMOS processes [17]
Summary
With the growth of the wireless industry, the spectral congestion caused by wireless user traffic has become a significant concern that threatens further growth of the technology [1, 2] This congestion is a result of suboptimal frequency usage arising from the inflexibility of the spectrum licensing process. We focus on the spectrum sensing aspect of the cognitive radio. The spectrum sensor remains a challenging aspect of cognitive radio design. The cognitive radio spectrum sensor needs to detect signals at all frequencies of interest instantaneously. We demonstrate the suitability of passive switched capacitor signal processing techniques for spectrum sensing applications. New measurement results are presented to corroborate the suitability of this design for spectrum sensing applications
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