Ding-Bing Lin

Performance analysis of two-branch transmit diversity block-coded OFDM systems in time-varying multipath Rayleigh-fading channels

Based on Alamouti code, Lee and Williams proposed two-branch transmit diversity block-coded orthogonal frequency-division multiplexing (TDBC-OFDM) systems, namely, space-time block-coded OFDM (STBC-OFDM) and space-frequency block-coded OFDM (SFBC-OFDM). However, they employed the simple maximum-likelihood (SML) detector, which was designed under the assumption that the channel is static over the duration of a space-time/frequency codeword. Therefore, STBC-OFDM/SFBC-OFDM suffers from the high time/frequency selectivity of the wireless mobile fading channel. In this paper, besides the original SML detector, three detectors proposed by Vielmon et al. are applied to improve the two-branch TDBC-OFDM systems. Additionally, assuming sufficient cyclic prefix, the performances of all systems in spatially uncorrelated time-varying multipath Rayleigh-fading channels are evaluated by theoretical derivation and computer simulation, as well. According to the derived bit-error rate (BER), we further derive the bit-error outage (BEO) to provide a more object judgment on the transmission quality within a fading environment. Numerical results have revealed that significant performance improvement can be achieved even when the systems are operated in highly selective channels.

Interference management of femtocell in macro-cellular networks

This paper investigates the impact of femtocell interference on existing macrocells with fractional frequency reuse (FFR). Instead of using complicated transmission techniques by coordinating multiple base stations (BSs), this paper adaptively configures FFR pattern to avoids interference caused by femtocells, depending on density and locations of femtocells. Simulation results show that the proposed femtocell BS deployment can effectively reduce downlink interference to macro-cellular networks.

Investigation in Open Circuited Metal Lines Embedded in Defected Ground Structure and Its Applications to UWB Filters

A novel method for notch implementation in ultrawideband (UWB) bandpass filter (BPF) using open circuited metal lines embedded in a defected ground structure (DGS) is proposed. Distinct from traditional notch implementation, the proposed method uses the additional metal lines with half waveguide length embedded in defected ground structure to produce additional notch band behavior based on the DGS bandpass behavior. Furthermore, the equivalent circuit model of the proposed UWB BPF with notch implementation is established for explaining the circuit behaviors more explicitly. In this way, the proposed circuit has a very small size, only amounting to 0.41 by 0.22 guided wavelength at the center frequency of 6.85 GHz. The experimental filter has a notch band frequency of 5.5 GHz, with two observable attenuation poles at 1.65 and 11.36 GHz, respectively. The measured BPF insertion loss is less than 1.0 dB throughout the passband of 3.1 to 10.6 GHz, and the variation of group delay is less than 0.2 ns in this band, except for the notched band.

All Polarization Receiving Rectenna With Harmonic Rejection Property for Wireless Power Transmission

In this paper, a high conversion efficiency rectenna for wireless power transmission at 2.45 GHz is proposed. The rectenna is fabricated on a low-cost FR-4 substrate. The proposed design contains a dual circularly polarized patch antenna in which a high-order harmonic rejection property is embedded, and a pair of rectifying circuits without harmonic rejection filters. The dimension for the proposed rectenna design is 100×100×3.8 mm3. The proposed rectenna collects waves in all polarization senses simultaneously with a suitable air gap width, chosen to maximize antenna gain, and provide high isolation between the rectifying circuits. The rectifying circuits are fed by the wave power of orthogonally polarized waves. The conversion efficiency is improved by blocking the second and the third harmonic noise from reemission without suffering loss from filters: the second harmonic noise is rejected with a T-shape slot, while the third is rejected by a U-shape resonator. The measured conversion efficiency of the proposed rectenna reaches 82.3% when the inputs of the rectifying circuits are fed at 22 dBm, surpassing the majority of existing rectenna designs in the current literature. The functionality of reception at all polarizations is also verified, distinguishing our design from other proposals.

Suppression of Crosstalk Using Serpentine Guard Trace Vias

The reliability of circuits on printed circuit boards (PCBs) in many modern electronic products is afiected by severe noise caused by high-speed and low-voltage operation as well as layout constraints compounded by limited space and high circuit density. Crosstalk is a major noise source that interferes with the signal integrity (SI) in poor PCB layout designs. One common method of reducing crosstalk is the three-width (3-W) rule. The serpentine guard trace (SGT) approach has also been used to reduce crosstalk using two terminal matching resistors on the SGT between the aggressor and victim. Although the SGT approach suppresses far-end crosstalk (FEXT) at the expense of more layout space, it also neglects interference caused by near-end crosstalk (NEXT). In this study, we propose the SGT via (SGTV) approach in which grounded vias are added to the SGT at appropriate locations, and the ratio between the lengths of the horizontal and vertical sections of the guard trace is adjusted to minimize NEXT and FEXT. Frequency domain simulated (measured) results showed that the SGTV approach reduced NEXT by 3.7 (7.65) and 0.83 (1.6)dB as well as FEXT by 5.11 (7.22) and 0.1 (1.98)dB compared to the 3-W and SGT approaches, respectively. In the time domain, simulated (measured) results showed that SGTV reduced NEXT by 34.67% (49.8%) and 27.5% (26.65%) as well as FEXT by 46.78% (56.52%) and 6.91% (24.8%) compared to the 3-W and SGT approaches, respectively.

A Compact Quad-Band PIFA by Tuning the Defected Ground Structure for Mobile Phones

The development of compact antennas plays an important role in the rapidly growing mobile communication market. This paper presents a novel design technique of the quad-band small internal antenna covering GSM-900/DCS-1800/PCS-1900/IMT-2000 bands. The innovative quad-band built-in handset antenna is developed within the limit of a 44×25×4mm3 volume. The following document describes a new idea of increasing operational bandwidth for the compact planar inverted F antenna (PIFA). The proposed compact antenna introduces the open-end slots in the ground plane almost all under the radiating patch. The size reduction method is attractive for practical antenna implementations. In addition, the end user’s hand handling effects on the performances of the proposed antenna are studied. Received 6 July 2010, Accepted 7 August 2010, Scheduled 13 August 2010 Corresponding author: I-T. Tang (tangitseng@gmail.com). 174 Lin, Tang, and Hong

A New Approach of Dual-Band Filters by Stepped Impedance Simplified Cascaded Quadruplet Resonators with Slot Coupling

This paper presents novel approaches for dual-band bandpass fllter design utilizing stepped impedance simplifled cascaded quadruplet resonators (SI-SCQRs) with slot coupling. A pair of SI- SCQRs forms a cross coupled dual-band flltering path to provide high selectivity passband response, and a slot coupling structure provides SI-SCQRs with another flltering path for improving and controlling the performances of the dual-band fllter such as insertion loss and bandwidth. Measured insertion losses are 0.26dB and 1.2dB, and return losses are better than 16.3dB and 15.2dB at the flrst and second

Hybrid SADOA/TDOA mobile positioning for cellular networks

A signal attenuation difference of arrival (SADOA) scheme is proposed to combine with the time difference of arrival (TDOA) method for mobile location estimation. On the basis of ratio of distances between the mobile and base stations derived from differences of signal attenuations, each SADOA measurement yields a circle on which the mobile may lie. Meanwhile, each TDOA measurement defines a hyperbola on which the mobile may reside. The proposed hybrid SADOA/TDOA scheme uses Taylor-series expansion to linearise the circles and hyperbolas and iteratively computes the mobile position based on least-squares estimation. Without perfect path loss modelling and hardware modification, the proposed scheme reduces location errors compared with either technique separately. Simulations demonstrate encouraging performance with 50% improvement over the conventional TDOA method in shadowing and non-line-of-sight propagation environments.

Mobile location estimation based on differences of signal attenuations for GSM systems

Radio location by time advance for GSM systems had been published. However, the resolution of time advance in GSM systems is too coarse to locate a mobiles position. The paper proposes a mobile location estimation based on the differences of downlink signal attenuations. This provides a possible mobile location method if the relationship between distance and signal attenuation is determined. Then, the mobile location can be estimated from those possible locations. The error of the proposed method is much smaller than the error of the cell-ID method in the practical microcell system. The greatest advantage of this method is the non-necessity of a known and accurate path loss model and the reduction of the shadowing effect.

Microwave density imaging of perfectly conducting objects in the near-field region

Analytical and numerical studies of microwave diversity imaging of continuous and discrete conducting objects in the near-field region are presented. Analytical results show that the image of the scattering object can be reconstructed by Fourier inversion of the data acquired from the recorded scattered field using angular and frequency diversity techniques. Different feature information of the scattering object can be obtained using a polarization diversity technique. Various scattering arrangements are studied and compared on the basis of the reconstructed image quality and practical considerations. Numerical results show that the described frequency, angular, and polarization diversity techniques in the backward scattering arrangement can result in a cost-effective approach in near-field microwave imaging systems. >