Band 69, Heft 7-8 -

In this letter, a compact monopole planar antenna with inverted F- and L-shaped strips is presented for WLAN and WiMAX applications. By adjusting the geometries and the sizes of the strips, the proposed antenna can achieve triple-band performance covering three separated impedance bandwidths of 300 MHz (2.2–2.5 GHz), 400 MHz (3.3–3.8 GHz), and 800 MHz (5.1–5.9 GHz), which are well applied for both 2.4/5.2/5.8-GHz WLAN bands and 3.5/5.5-GHz WiMAX bands. The overall dimension of the proposed antenna can reach 20 × 25.5 mm 2 . Measured S11 and radiation patterns show good agreement with the simulated ones.

Two compact zeroth-order resonant antennas employing short-ended mu-negative transmission line (MNG-TL) are presented. Both antennas are fed by asymmetric coplanar strip (ACPS), so strong miniaturization and simple structure can be achieved. Proposed antenna 1 operates at 2.38–2.47 GHz (fractional bandwidth is 3.7%), with a size of 0.093 λ 0 × 0.145 λ 0 × 0.008 λ 0 at center frequency. In order to extend the bandwidth further, a tapered structure (using parabola curves) is designed in proposed antenna 2. Then an operating band of 2.41–2.97 GHz (fractional bandwidth is 20.8%) is obtained with a size of 0.095 λ 0 × 0.225 λ 0 × 0.009 λ 0 at center frequency. Finally both antennas are fabricated and measured; measurements and EM (electromagnetic) simulations are in good agreement. And the results demonstrate that the proposed antennas have satisfactory omnidirectional radiation patterns with reasonable gains and extended efficiencies within the operating bands.

In this paper, a novel miniaturized wide stop-band branch-line coupler operating at 2.5 GHz is presented. Two different structures, by combination of a microstrip resonant cell with T-shaped stubs, are formed and hence embedded as horizontal and vertical branches of the hybrid coupler. The ultimate structure of the coupler offers 52% of miniaturization efficiency as compared with its conventional counterpart. The performance of the coupler is verified by measurements in a very good agreement with simulation results and moreover it has been revealed that the coupler is capable to broadly suppress harmonics of the operating frequency from third to seventh, corresponding to a stop-band of 6–18 GHz.

This paper presents a new design of a compact Gysel power divider with harmonic suppression. It comprises six similar low-pass filters in lieu of six conventional transmission lines in the Gysel power divider. Not only does the proposed power divider extremely reduce the occupied area to 22.7% of the conventional Gysel power divider at 900 MHz, but also it features the higher order harmonic rejection. Simulation and measurement results show good insertion loss, return loss, isolation, and wide stopband bandwidth, while maintaining high-power handling capability over the Wilkinson power divider.

A novel compact ultra-wideband (UWB) bandpass filter (BPF) with a quad band-notched function using S-SCRLHs (splitted simplified composite right/left-handed) resonator is presented. The S-SCRLHs resonator, which exhibits quadruple resonance, is realized by coupling double S-SCRLH resonator. The S-SCRLHs resonator is integrated into a conventional UWB BPF. The notched frequencies can be adjusted according to specification by altering the S-SCRLHs resonator. Band-rejected filtering properties around the C-band satellite communication band, 5.2 GHz WLAN band and the X-band satellite communication band are generated. The notching frequencies are located at 4.2/5.2/6.3/7.8 GHz. Both simulated and measured results are provided with good agreement. Compared with other BPFs, the proposed BPF has the advantages of compact size, multi-stopband and good selectivity.

In this paper, we consider a wireless multi-antenna system using a promising technique, i.e., spatial modulation, and propose an adaptive spatial modulation (ASM) scheme embedded Alamouti space-time block coding (STBC). Instead of selecting one active antenna in each transmission in conventional ASM, we activate two antennas as one antenna group simultaneously to encode the information bits into Alamouti code blocks, each of which needs two channels used. Two detection schemes are presented in different channel conditions, i.e., the maximum likelihood (ML) detection and an adaptive modulation-order selection algorithm. Simulation results show that the proposed scheme improves the error performance and provides larger diversity gain compared to conventional spatial modulation and adaptive spatial modulation.

In this paper analysis of various fading statistics of generic fading distribution, termed as N product of Generalized Gamma distribution is done to model multihop relay fading channels. Generalized gamma (GG) model being a versatile, flexible and multi-parameter model has been selected here as it can generalize commonly used fading models such as Weibull, Nakagami-m, etc. Exact closed expressions of probability density function (PDF) and Cumulative Distribution Function (CDF) are obtained here for the product of multiple GG random variables (RV)s. Based on the derived expressions performance analysis of multihop relay links has been done here in terms of coefficient of variation (CV), amount of fading (AF) and spectral efficiency and outage probability. The closed-form expressions obtained here are tractable and easy to evaluate as validated through extensive numerical evaluations.

Cognitive radios (CRs) observe their environment, learn from it and take their findings into account when dealing with signal reception or transmission. Until now, essentially spectral observations are under discussion in the CR context. Smart spectrum sensing may allow secondary or opportunistic use of spectrum and lead to dynamic spectrum access. In this paper we investigate a CR that also employs spectrum sensing but additionally may take results of modulation recognition as well as bit stream recognition into account when tuning its receiver. Bit stream analysis as an essential prerequisite to bit stream recognition is introduced as well. In data communications, bit streams play a prominent role in burst and frame structures, scrambling, synchronization, error correction coding or ciphering. Since modulation recognition found reasonable attention in recent publications, we here concentrate on bit stream recognition and analysis in a CR.

In this paper, we propose a hybrid scheme called transmit antenna selection and receiver’s artificial noise (TAS–rAN) for security enhancement in multiple-input single-output (MISO) wiretap channels. In this scheme, by using TAS protocol, the transmitter selects a single antenna that maximizes the instantaneous signal-to-noise ratio (SNR) at the full-duplex receiver. While the transmitter uses this antenna to transmit secrecy data, the full-duplex receiver would send artificial noise (AN) to confuse the potential eavesdropper. For the proposed protocol, we consider Rayleigh fading channels with different parameters for the main channel and the eavesdropper’s channel, and derive new closed-form expressions for the exact secrecy outage probability and the asymptotic secrecy outage probability. We demonstrate that the proposed TAS– r AN protocol can offer higher secure performances than both existed single TAS and TAS–Alamouti schemes. Comparing to the existing schemes with AN-aided by full-duplex receiver, our TAS– r AN strategy considers the multi-antenna transmitter with TAS protocol, and the secrecy outage probability is improved with increasing the antenna number. The numerical simulation results verify our analysis.

Orthogonal frequency division multiplexing (OFDM)-based ground penetrating radar (GPR) has been proved to have a number of advantages. To improve the performance of a GPR system, time domain non-periodic autocorrelation (AC) of the transmitted OFDM signal should be designed to have similar shape to an ideal pulse. Challenge in OFDM signal design for GPR is that there is little pertinent literature and the design should be different from that in communication and air radar fields. In this paper, we propose a design scheme of OFDM signal with good AC for GPR. We divide the AC into main lobe and side lobe with proving that the main lobe is dominated with the functionality of the modulating amplitudes while the side lobe’s main function is modulating phases. Thus, modulating amplitudes and phases can be designed, respectively. Performance of this proposed approach is demonstrated by numerical examples. The results show that the designed OFDM signal yields a better AC and fewer false alarms for GPR systems.

This paper presents a beyond state-of-the-art, sweeping microwave asphalt radar mounted on a small radio controlled four-wheel-drive rover. The quasi-monostatic, remote-controllable radar operates at Ku-band and has an output power of +10 dBm. Detection follows the zero intermediate frequency principle. The sweep width allows for a depth resolution better than 10 mm. With its four microprocessors and laptop computer processing, the radar system can provide pavement permittivity data with an uncertainty close to 0.1. This is a considerable advancement when applying electromagnetic measurement techniques for applications where near surface or thin surface layer measurements are needed.