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The gain-bandwidth product of a conventional antenna is limited by its electrical size. Synchronous antenna tuning circumvents the limited bandwidth of a time-invariant resonant antenna by modifying the impedance match of the antenna in synchrony with the communications signal. This paper extends an investigation of tuning a VLF antenna in synchrony with a frequency shift keyed (FSK) signal to higher...
This paper explores using a rapidly tuned, narrowband device as an analog-to-information converter (AIC). This concept is applied to a rapidly tuned, instantaneously narrowband antenna. Such a setup is advantageous in cognitive radio, where an antenna designed for communicating over a portion of the spectrum may be used to meet the wideband spectrum sensing requirement. A method for reducing the bandwidth...
This paper presents the soft-input soft-output (SISO) linear programming (LP) decoder. It is shown that the soft information gleaned from a pseudo-codeword solution to the LP optimization is not only useful, but that it can be used to form a superior channel estimate compared to the output from a SISO belief propagation (BP) decoder in certain situations.
The modulated wideband converter (MWC) introduced in [1] enables a wide band of spectrum to be sensed using inexpensive components. The MWC spreads the received signal in frequency, which allows the spectral occupancy to be sensed from sub-Nyquist rate samples via compressive sensing techniques. This paper compares embedding the MWC into the tuning circuit of the antenna with placing it in the receive...
This paper presents the soft-input soft-output (SISO) linear programming (LP) decoder. It is shown that the soft information gleaned from a pseudo-codeword solution to the LP optimization is not only useful, but that it can be superior to the soft information output from a SISO belief propagation (BP) decoder in certain situations.
In this paper, we investigate applying linear turbo equalization techniques to underwater acoustic communications. First, we elaborate on two popular linear turbo equalizers (TEQ), a channel estimate-based minimum mean square error TEQ (CE-based MMSE-TEQ) and a direct-adaptive TEQ (DA-TEQ). We compare the behavior of both TEQ approaches in the presence of channel estimation errors and adaptation filter...
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