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a compact size and lightweight planar ultra-wideband (UWB) antenna with an omnidirectional radiation pattern and a stable gain in the frequency range 3.1-10.6 GHz is proposed and investigated. The antenna consists of an elliptical shaped slot which is fed by a 50-Ω microstrip line that is beveled and has fork-shaped is designed. Attaching two inverted U-shape strips at the upper part of the slot, two additional bands are realized covering GPS, upper part of GSM (1770–1840 MHz), and Bluetooth (2385–2490 MHz) bands. The calculated return loss, omni-directional radiation pattern, and peak gain are in good agreement with the measurement results. The antenna can provide high-performance wireless communications over different frequency bands. This structure has a compact size (27×24 mm²), is lightweight, and can be easily fabricated.    According, the proposed antenna is expected and normal to be a good candidate in various applications in portable and lightweight communication system.
 

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 Energy detector is one of the non-coherent receivers for impulse radio ultra-wideband (IR-UWB) systems using on-off keying (OOK) modulation. Energy detection for IR-UWB OOK systems gets accomplished based on a threshold value. In these systems, the threshold value depends on several parameters that should be determined in the receiver.  In this paper, we propose a blind approach to estimate proper thresholds for the symbol decision. The performance of the proposed method turns out to be asymptotically comparable to that of the optimal threshold selection. The proposed algorithm was also improved using an optimum integration interval. By using a blind estimating of the channel time delay spread, the integration interval was adjusted. Simulation results show that this method improves the performance about 1.5 dB in BER of 10^-4.