A stacked square microstrip antenna with shorting plates is proposed for wide band operation. The vswr 2 with gain at θ=0 0 dBi is achieved in the frequency range between the first and second resonant frequencies by loading the two shorting plates. The proposed antenna has bandwidth of approximately 60%.

Comparison of the electromagnetic characteristics of a monopole-type wire antenna (MTWA) and an inverted-F wire antenna (IFWA) is performed based on numerical and experimental results. Radiation characteristics, when the handset model is located in the vicinity of a head phantom or in free space, are also investigated. The gain of 8.27 dBi is achieved at 3.4 GHz for the MTWA with the head phantom.

In this letter, the influence of the downlink average ratio of the other cell interference to other-user interference in the serving cell (DARI) on the distributed repeater system (DRS) performance is analyzed. It is found that the improvement of DARI depends on a propagation path loss environment. Applying the computed DARI to a 3-RS DRS cell, as high as 13.9% capacity enhancement was obtained when the path loss exponent is 4.5. In addition, by using the power allocation equation, it is expected that a hexagonal DRS cell without coverage holes or excessive coverage overlap can be realized.

A design method is proposed for a low-profile dual-shaped reflector antenna for the mobile satellite communications. The antenna is required to be low-profile because of mount restrictions. However, reduction of its height generally causes degradation of antenna performance. Firstly, an initial low-profile reflector antenna with an elliptical aperture is designed by using Geometrical Optics (GO) shaping. Then a Physical Optics (PO) shaping technique is applied to optimize the gain and sidelobes including mitigation of undesired scattering. The developed design method provides highly accurate design procedure for electrically small reflector antennas. Fabrication and measurement of a prototype antenna support the theory.

Vector precoding is a nonlinear broadcast precoding scheme in the downlink of multi-user MIMO systems which outperforms linear precoding and THP (Tomlinson-Harashima Precoding). This letter discusses the problem of joint receive antenna selection in the multi-user MIMO downlink with vector precoding. Based on random matrix analysis, we derive a simple heuristic selection criterion using singular value decomposition (SVD) and carry out an exhaustive search to determine for each user which receive antenna should be used. Simulation results reveal that receive antenna selection using our proposed criterion obtains the same diversity order as the optimal selection criterion.

A multiband T-shaped monopole antenna for WLAN/WiMAX applications is presented. The T-shaped monopole is comprised of two horizontal arms of different lengths, which generate two separate resonant modes for 2.5/5.5 GHz WLAN/WiMAX bands, and with a shortened parasitic element, which generates a middle resonant mode for 3.5 GHz WiMAX band, for seamless wireless network access applications. The proposed antenna has been successfully simulated and implemented. Both results of simulation and measurement show good agreement. For the lower band from 2.3 to 2.7 GHz, the gain varies in the range of 2.5-3.3 dB, while the radiation efficiency is from 72% to 85% over the band. As for the middle band from 3.3 to 3.7 GHz, the gain varies from 1.5 to 2.0 dB, and the radiation efficiency is from 62% to 70%. As for the upper band from 5.2 to 5.8 GHz, the antenna gain varies from 5.4 to 5.9 dB, and the radiation efficiency is from 63% to 66%.

A lightweight and high gain planar antenna for space use is realized with radial waveguide slotted array and honeycomb structure with the weight of 1.16 kg and the diameter of 920.5 mm. The slot coupling is analyzed by method of moments considering the hybrid mode in the multi-layer waveguide structure. The propagation constant of the honeycomb structure is measured and the low-loss property is obtained at the frequency range of 8 GHz. The fabricated RLSA is measured and the reflection is around -10 dB in 8 GHz band. The measured aperture fields agree with the calculation in the radial direction. In the azimuthal direction, on the other hand, the fields show ripples of 6 dB and 60 degree. The gain of 35.9 dBi with the efficiency of 58.7% is obtained at 8.6 GHz.

The Earth will require sustainable electricity sources equivalent to 3 to 5 times the commercial power presently produced by 2050. Solar Power Satellite (SPS) is one option for meeting the huge future energy demand. SPS can send enormous amounts of power to the Earth as the form of microwave (MW). A highly efficient microwave power transmission (MPT) system is needed for SPS. A critical goal of SPS is to maintain highest Beam Efficiency (BE) because the microwaves from SPS will be converted to utility power unlike the MW from communication satellites. Another critical goal of SPS is to maintain Side Lobe Levels (SLL) as small as possible to reduce interference to other communication systems. One way to decrease SLL and increase BE is the edge tapering of a phased array antenna. However, tapering the excitation requires a technically complicated system. Another way of achieving minimum SLL is with randomly spaced element position but it does not guarantee higher BE and the determination of random element position is also a difficult task. Isosceles Trapezoidal Distribution (ITD) edge tapered antenna was studied for SPS as an optimization between full edge tapering and uniform amplitude distribution. The highest Beam Collection Efficiency (BCE) and lowest SLL (except maximum SLL) are possible to achieve in ITD edge tapering and ITD edge tapered antenna is technically better. The performance of ITD is further improved from the perspective of both Maximum Side Lobe Level (MSLL) and BE by using unequal spacing of the antenna elements. A remarkable reduction in MSLL is achieved with ITD edge tapering with Unequal element spacing (ITDU). BE was also highest in ITDU. Determination of unequal element position for ITDU is very easy. ITDU is a newer concept that is experimented for the first time. The merits of ITDU over ITD and Gaussian edge tapering are discussed.

The combination of Multiple-Input Multiple-Output (MIMO) and Orthogonal Frequency Division Multiplexing (OFDM) technologies gives wireless communications systems the advantages of lower bit error rate (BER) and higher data rate in frequency-selective fading environments. However, the main drawbacks of MIMO systems are their high complexity and high cost. Therefore, antenna selection in MIMO systems has been shown to be an effective way to overcome the drawbacks. In this paper, we propose two receive antenna selection methods for a MIMO-OFDM system with radio frequency (RF) switches and polarization antenna elements at the receiver side, taking into consideration low computational complexity. The first method selects a set of polarization antenna elements which gives lower correlation between received signals and larger received signal power, thus achieves a lower BER with low computational complexity. The second method first selects a set of polarization antenna elements based on the criterion of the first method and another set of polarization antenna elements based on the criterion of minimizing the correlation between the received signals; it then calculates the signal-to-interference-plus-noise power ratio (SINR) of the two sets and selects a set with larger SINR. As a result, the second method achieves a better BER than the first one but it also requires higher computational complexity than the first one. We use the measured channel data to evaluate the performance of the two methods and show that they work effectively for the realistic channel.

LSI on-chip optical interconnections are discussed from the viewpoint of a comparison between optical and electrical interconnections. Based on a practical prediction of our optical device development, optical interconnects will have an advantage over electrical interconnects within a chip that has an interconnect length less than about 10 mm at the hp32-22 nm technology node. Fundamental optical devices and components used in interconnections have also been introduced that are small enough to be placed on top of a Si LSI and that can be fabricated using methods compatible with CMOS processes. A SiON waveguide showed a low propagation loss around 0.3 dB/cm at a wavelength of 850 nm, and excellent branching characteristics were achieved for MMI (multimode interference) branch structures. A Si nano-photodiode showed highly enhanced speed and efficiency with a surface plasmon antenna. By combining our Si nano-photonic devices with the advanced TIA-less optical clock distribution circuits, clock distribution above 10 GHz can be achieved with a small footprint on an LSI chip.

In a Cognitive Radio system, it is essential to recognize and avoid sources of interference signals. This paper describes a study on a location sensing scheme for interference signals, which utilizes multi-beam phased array antenna for cognitive wireless networks. This paper also elucidates its estimation accuracy of the interference location for the radio communication link using an OFDM signal such as WiMAX. Furthermore, we use the frequency spectrum of the received OFDM interference signal, to create a method that can estimate the propagation status. This spectrum can be monitored by using a software defined radio receiver.

To obtain a broad circular-coverage beam with low sidelobe, this paper proposes optimization design based on the quadratic programming approach for circular horns. The desired excitation coefficients of higher-order modes are pre-determined and also evaluated by calculating universal radiation patterns. We show a design example of a multimode horn which has circular-coverage beam with low sidelobe level of about -30 dB. The effectiveness of the designed horn is discussed by evaluating VSWR and radiation characteristics in X-band numerically and experimentally.

Outage performance of cognitive radios is analyzed in this paper. The scenario under consideration requires the cognitive radio to sense whether the primary user (PU) link is free (i.e. a spectrum hole exists) before making an active transmission using that link. Multiple antennas are available at the cognitive radio link to provide array gains at the sensing stage. We derive a closed-form expression of the outage probability for cognitive transmission by classifying it into several cases. A sensing threshold is deduced according to the PU arrival model illustrated in this paper. Simulation results verify our analysis.

In our application targeted here, four on-glass antenna elements are set in an automobile to improve the reception quality of mobile ISDB-T receiver. With regard to the directional characteristics of each antenna, we propose and implement a joint Pre-FFT adaptive array antenna and Post-FFT space diversity combining (AAA-SDC) scheme for mobile ISDB-T receiver. By applying a joint hardware and software approach, a flexible platform is realized in which several system configuration schemes can be supported; the receiver can be reconfigured on the fly. Simulation results show that the AAA-SDC scheme drastically improves the performance of mobile ISDB-T receiver, especially in the region of large Doppler shift. The experimental results from a field test also confirm that the proposed AAA-SDC scheme successfully achieves an outstanding reception rate up to 100% while moving at the speed of 80 km/h.

The concept of placing enormous Solar Power Satellite (SPS) systems in space represents one of a handful of new technological options that might provide large scale, environmentally clean base load power to terrestrial markets. Recent advances in space exploration have shown a great need for antennas with high resolution, high gain and low side lobe level (SLL). The last characteristic is of paramount importance especially for the Microwave Power Transmission (MPT) in order to achieve higher transmitting efficiency (TE) and higher beam collection efficiency (BCE). In order to achieve low side lobe levels, statistical methods play an important role. Various interesting properties of a large antenna arrays with randomly, uniformly and combined spacing of elements have been studied, especially the relationship between the required number of elements and their appropriate spacing from one viewpoint and the desired SLL, the aperture dimension, the beamwidth and TE from the other. We propose a new unified approach in searching for reducing SLL by exploiting the interaction of deterministic and stochastic workspaces of proposed algorithms. Our models indicate the side lobe levels in a large area around the main beam and strongly reduce SLL in the entire visible range. A new concept of designing a large antenna array system is proposed. Our theoretic study and simulation results clarify how to deal with the problems of side lobes in designing a large antenna array, which seems to be an important step toward the realization of future SPS/MPT systems.

This letter presents a reconfigurable antenna with a microstrip patch that uses PIN-diode connections on slits to achieve frequency diversity. By switching the diodes on or off, a surface current path on the antenna is changed, which effectively results in shifting the operating frequency. Thus the antenna can select both WiBro and DMB bands.

In this paper we analyze the characteristics of vehicle mobility and propose a novel Mobility Prediction Progressive Routing (MP2R) protocol for Inter-Vehicle Communication (IVC) that is based on cross-layer design. MP2R utilizes the additional gain provided by the directional antennas to improve link quality and connectivity; interference is reduced by the directional transmission. Each node learns its own position and speed and that of other nodes, and performs position prediction. (i) With the predicted progress and link quality, the forwarding decision of a packet is locally made, just before the packet is actually transmitted. In addition the load at the forwarder is considered in order to avoid congestion. (ii) The predicted geographic direction is used to control the beam of the directional antenna. The proposed MP2R protocol is especially suitable for forwarding burst traffic in highly mobile environments. Simulation results show that MP2R effectively reduces Packet Error Ratio (PER) compared with both topology-based routing (AODV [1], FSR [2]) and normal progressive routing (NADV [18]) in the IVC scenarios.

This letter describes a millimeter wave slot array antenna using a rectangular waveguide and a ferrite. The radiation direction of the leaky wave from the slot array can be scanned by applying a dc bias magnetic field parallel to the ferrite. The radiation pattern of a prototype antenna has been measured at 40 GHz. The main beam direction changes from 10 to 3 degree by the bias magnetic field of 0.73 T.

A novel helix-monopole antenna is proposed which combines the helix and monopole together to form improved current distribution. The current magnitudes are computed with Moment Method (MM) and results show the current difference between helix-monopole and helix antenna. Two antennas are fabricated for comparison and measured on the same two-way portable radio with frequency band from 400-420 MHz. Measurements prove that the proposed antenna offers a significant improvement in gain.

For coherent detection, decoding Orthogonal Space-Time Block Codes (OSTBC) requires full channel state information at the receiver, which basically is obtained by channel estimation. However, in practical systems, channel estimation errors are inevitable and may degrade the system performance more as the number of antennas increases. This letter shows that, using fewer receive antennas can enhance the performance of OSTBC systems in presence of channel estimation errors. Furthermore, a novel adaptive receive antenna selection scheme, which adaptively adjusts the number of receive antennas, is proposed. Performance evaluation and numerical examples show that the proposed scheme improves the performance obviously.