Yingsong Li

Norm-adaption penalized least mean square/fourth algorithm for sparse channel estimation

A type of norm-adaption penalized least mean square/fourth (NA-LMS/F) algorithm is proposed for sparse channel estimation applications. The proposed NA-LMS/F algorithm is realized by incorporating a p-norm-like into the cost function of the conventional least mean square/fourth (LMS/F) which acts as a combination of the l0- and l1-norm constraints. A reweighted NA-LMS/F (RNA-LMS/F) algorithm is also developed by adding a reweighted factor in the NA-LMS/F algorithm. The proposed RNA-LMS/F algorithm exhibits an improved performance in terms of the convergence speed and the steady-state error, which can provide a zero attractor to further exploit the sparsity of the channel by the use of the norm adaption penalty and the reweighting factor. The simulation results obtained from the sparse channel estimations are given to verify that our proposed RNA-LMS/F algorithm is superior to the previously reported sparse-aware LMS/F and the conventional LMS/F algorithms in terms of both the convergence speed and the steady-state behavior. HighlightsNorm-adaption penalized LMS/F (NA-LMS/F) algorithm is proposed for channel estimation.Reweighting NA-LMS/F (RNA-LMS/F) algorithm is proposed and analyzed in detail.Simulations verify the performance of the proposed NA-LMS/F and RNA-LMS/F algorithms.RNA-LMS/F algorithm has fastest convergence and best channel estimation performance.

A Reconfigurable Triple-Notch-Band Antenna Integrated with Defected Microstrip Structure Band-Stop Filter for Ultra-Wideband Cognitive Radio Applications

A printed reconfigurable ultra-wideband (UWB) monopole antenna with triple narrow band-notched characteristics is proposed for cognitive radio applications in this paper. The triple narrow band-notched frequencies are obtained using a defected microstrip structure (DMS) band stop filter (BSF) embedded in the microstrip feed line and an inverted π-shaped slot etched in the rectangular radiation patch, respectively. Reconfigurable characteristics of the proposed cognitive radio antenna (CRA) are achieved by means of four ideal switches integrated on the DMS-BSF and the inverted π-shaped slot. The proposed UWB CRA can work at eight modes by controlling switches ON and OFF. Moreover, impedance bandwidth, design procedures, and radiation patterns are presented for analysis and explanation of this antenna. The designed antenna operates over the frequency band between 3.1 GHz and 14 GHz (bandwidth of 127.5%), with three notched bands from 4.2 GHz to 6.2 GHz (38.5%), 6.6 GHz to 7.0 GHz (6%), and 12.2 GHz to 14 GHz (13.7%). The antenna is successfully simulated, fabricated, and measured. The results show that it has wide impedance bandwidth, multimodes characteristics, stable gain, and omnidirectional radiation patterns.

Analysis and Investigation of a Cantor Set Fractal UWB Antenna with a Notch-Band Characteristic

A coplanar waveguide (CPW) fed ultra-wideband (UWB) antenna with a notch band characteristic is presented in the paper. The radiation patch of the proposed UWB antenna is designed using cantor set fractal technology. The bandwidth is broadened by setting two symmetrical triangular tapered corners at the bottom of the wide slot of the proposed UWB antenna. The notched band characteristic is achieved by employing a T-shaped tuning stub at the top of the wide slot. The notched band can be controlled by adjusting the length and the width of the T-shaped tuning stub to give tunable notched band function. The proposed cantor set fractal wide slot UWB antenna has been designed in details and optimized. Experimental and numerical results show that the proposed antenna, with compact size of 26 £ 21mm 2 , has an impedance bandwidth range from 2.8GHz to 11GHz for voltage standing-wave ratio (VSWR) less than 2, except the notch band frequency 5.0GHz{6.3GHz for HIPERLAN/2 and IEEE 802.11a (5.1GHz{5.9GHz).

Two UWB-MIMO antennas with high isolation using sleeve coupled stepped impedance resonators

Two printed ultra wideband (UWB) antennas integrated with stepped impedance resonators for Multiple Input Multiple Output (MIMO) communications applications are proposed in this paper. The proposed MIMO antennas consist of two simple printed microstrip-fed monopole antennas. The high isolations are obtained by using sleeve coupled rectangle stepped impedance resonator (R-SIR) and sleeve coupled roundness stepped impedance resonator (RD-SIR) on the ground plane, respectively. The proposed antennas operate over a wide impedance bandwidth ranging from 3.1GHz to 10GHz. And the antennas have high isolation over 23dB. The return loss and the isolation of the antenna are investigated by means of HFSS. The results show that the proposed UWB-MIMO antennas have high isolation and good impedance match characteristic.

Sparse Adaptive Channel Estimation Based on -Norm-Penalized Affine Projection Algorithm

We propose an -norm-penalized affine projection algorithm (LP-APA) for broadband multipath adaptive channel estimations. The proposed LP-APA is realized by incorporating an -norm into the cost function of the conventional affine projection algorithm (APA) to exploit the sparsity property of the broadband wireless multipath channel, by which the convergence speed and steady-state performance of the APA are significantly improved. The implementation of the LP-APA is equivalent to adding a zero attractor to its iterations. The simulation results, which are obtained from a sparse channel estimation, demonstrate that the proposed LP-APA can efficiently improve channel estimation performance in terms of both the convergence speed and steady-state performance when the channel is exactly sparse.

An Improved Proportionate Normalized Least-Mean-Square Algorithm for Broadband Multipath Channel Estimation

To make use of the sparsity property of broadband multipath wireless communication channels, we mathematically propose an lp-norm-constrained proportionate normalized least-mean-square (LP-PNLMS) sparse channel estimation algorithm. A general lp-norm is weighted by the gain matrix and is incorporated into the cost function of the proportionate normalized least-mean-square (PNLMS) algorithm. This integration is equivalent to adding a zero attractor to the iterations, by which the convergence speed and steady-state performance of the inactive taps are significantly improved. Our simulation results demonstrate that the proposed algorithm can effectively improve the estimation performance of the PNLMS-based algorithm for sparse channel estimation applications.

A Novel UWB Filter with Notch-band Characteristic Using Radial-UIR/SIR Loaded Stub Resonators

This paper presents a novel approach for designing compact ultra-wideband (UWB) bandpass filter with a good notched band characteristic. A notch band characteristic is obtained by using the radial-uniform impedance resonators (UIR)/stepped impedance resonators (SIR) loaded stub resonator. The main advantage of the proposed filter is that the frequency of the notched band can be tuned easily in a wide frequency range. Current density and equivalent model is also given depending on the odd/even excitation resonance condition. The characteristics of the filter are analyzed. To verify the proposed methods, two filters are designed and fabricated. Measured results show that the proposed UWB properties from 3 to 10.8 GHz and the notch band can be changed optionally from 4 GHz to 10 GHz. These filters can be integrated in UWB radio systems and efficiently enhance the interference immunity from undesired signals such as wireless local area network (WLAN) and WiMAX.

Smooth approximation l(0)-norm constrained affine projection algorithm and its applications in sparse channel estimation.

We propose a smooth approximation l 0-norm constrained affine projection algorithm (SL0-APA) to improve the convergence speed and the steady-state error of affine projection algorithm (APA) for sparse channel estimation. The proposed algorithm ensures improved performance in terms of the convergence speed and the steady-state error via the combination of a smooth approximation l 0-norm (SL0) penalty on the coefficients into the standard APA cost function, which gives rise to a zero attractor that promotes the sparsity of the channel taps in the channel estimation and hence accelerates the convergence speed and reduces the steady-state error when the channel is sparse. The simulation results demonstrate that our proposed SL0-APA is superior to the standard APA and its sparsity-aware algorithms in terms of both the convergence speed and the steady-state behavior in a designated sparse channel. Furthermore, SL0-APA is shown to have smaller steady-state error than the previously proposed sparsity-aware algorithms when the number of nonzero taps in the sparse channel increases.

A printed diversity Cantor set fractal antenna for ultra wideband communication applications

In this paper, a printed diversity Cantor set fractal antenna for ultra wideband (UWB) applications is proposed. The antenna consists of two identical wide slot antennas and the radiation patches are designed by using Cantor set fractal technology. The proposed antenna operates over a wide band spanning from 4.5 GHz to 10.6 GHz. The diversity antenna has a high isolation over 20dB. The high isolation is obtained using multiple slots etched in its CPW ground plane. The return loss and the isolation of the antenna are investigated by means of HFSS. The diversity performance of the antenna is assessed by isolation and radiation patterns. The results show that the proposed antenna provides stable patterns diversity, which enables the designed antenna to combat multi-path in wireless channels used in UWB systems.

Compact reconfigurable UWB antenna integrated with SIRs and switches for multimode wireless communications

A kind of reconfigurable wide slot UWB antenna integrated with stepped impedance resonators (SIRs) and ideal switches is presented. The proposed antenna 1 has dual notch band functions which are obtained by using two stepped impedance stub loaded SIRs. The three reconfigurable models are investigated and discussed. The measurement results with ideals switches demonstrate the performances of proposed reconfigurable antennas. The designed reconfigurable antennas can be suitable for future multi-mode wireless communications systems.