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Experimental results for a novel transmission system using self-wrapped optical code division multiplexed signals to achieve enhanced data security at the physical layer of the optical network are presented. Key distribution is performed by encoding and time-spreading, thus allowing for both cryptographic and steganographic security in the public network. [ABSTRACT FROM AUTHOR]

A 3–5 GHz low power BPSK modulated impulse radio ultra-wideband (IR-UWB) transmitter is presented. In this design, the amplitude and spectrum of the output impulses are both tunable to solve the special problem, which is the difficulty in controlling the spectrum in IR-UWB. The total power consumption is only 4.44 mW at 100 MHz data rate. [ABSTRACT FROM AUTHOR]

This study mainly describes the fractal property of the frequency spectrum of the sea clutter and the application of the obtained fractal characteristic in frequency domain to the constant-false-alarm-rate (CFAR) target detection within sea clutter. First, this study takes fractional Brownian motion (FBM) for example, and the spectrum of the FBM is proved to be fractal theoretically on condition that the time series of the FBM is fractal. This argument lays the foundation for the application of fractal theory to the frequency spectrum. Next, X- and S-band real radar data are used for the verification of the fractal property of the real sea clutter frequency spectrum. Finally, the effects of the length of the time series and fast Fourier transform (FFT) are analysed in detail. The results show that the frequency spectrum of the real sea clutter is fractal in the statistical sense and the frequency Hurst exponents of clutter range bins and target range bins are distinguishable. Therefore the frequency Hurst exponent is used for the CFAR target detection within sea clutter. [ABSTRACT FROM AUTHOR]