On optimum MIMO with antenna selection

Wireless communication systems with transmit and receive antenna arrays are studied when antenna selection is used. A case with very limited feedback of information from the receiver to the transmitter is considered, where the only information fed back is the selected subset of transmit antennas to be employed. It is shown that the optimum signaling, for largest ergodic capacity with antenna selection, is generally different from that which is optimum without antenna selection for some range of signal-to-noise ratios.     

共轴双反射光学天线系统的优化设计

本文介绍一个共轴光学天线系统的计算机自动优化设计软件,此软件可使设计者方便、快速地设计各种优化的共轴双反射镜系统。     

The wave antenna for transmission and reception

The traveling-wave horizontal-wire antenna over the earth is analyzed in its original form with vertical ground connections (the Beverage antenna) and with these replaced by horizontal terminations. For transmission, the electromagnetic field of an antenna with optimum length is determined, both along the surface of the earth in air and in the earth, in an accurate but simple form that takes full account of the proximity of the earth (lake, sea) on the distribution of current. For reception, the induced currents in the antenna and in the load are determined for a field incident along the surface of the earth. The two types of termination are compared and their contributions shown to be small when the horizontal wire has a length near the optimum.     

A two-beam slotted leaky waveguide array for mobile reception ofdual-polarization DBS

A two-beam slotted leaky waveguide array for mobile reception of dual-polarization direct broadcast from satellite (DBS) is realized in a single-layer structure. Two feed waveguides attached at both ends of cross-slotted radiating waveguides excite the leaky waves propagating in opposite directions. Each of them radiates either of two circularly polarized waves in symmetrical beam directions. Balanced design of two beams for each polarization imposes symmetry in the array design of slots. The slot coupling distribution is optimized for the maximum gain under this symmetry condition. A model antenna in about a 300-mm square is fabricated for experiments in the 12-GHz band. Antenna efficiency of 71% and 64% is obtained for each beam in different polarizations     

Low-cost approach for steerable flat-plate antenna design withapplication to reception of broadcasting from satellite

A novel design approach for circularly polarised flat-plate antennas has been developed. The proposed antenna is of multilayer construction, rotatable about its normal axis, and comprises a polarisation convertor, an array of elements and a beamforming network. In one potentially large application, the reception of satellite broadcast signals in the 12 GHz band, it can be mounted flat on the most suitable wall of an arbitrarily orientated house and be readily aligned     

Slot-monopole antenna system for energy-density reception at UHF

A new type of energy-density antenna is proposed for mobile telephony in the 800-1200-MHz range using a slot-monopole antenna (SMA) configuration. To mount the antenna on a mobile two orthogonally crossed slot antennas backed by a shallow cavity placed on the roof were found to be most suitable for receiving the magnetic field components, whereas a monopole attached to the base of the cavity and designed as a sleeve antenna is utilized to probe the electric field component. A prototype of the SMA system is manufactured, and its dimensions and design characteristics are presented. The radiation pattern, the input impedance of each of the three sections of the antenna system, and the isolation characteristics between all the sections of the SMA are measured and discussed.     

A notch-wire composite antenna for polarization diversity reception

This paper presents a notch-wire composite antenna for polarization diversity reception in an indoor base-station system. A three-notched disk antenna and a wire antenna are proposed as component antennas for the horizontal and the vertical polarization, respectively. These component antennas are unified as a single composite diversity antenna by mounting the wire antenna on the notched disk. Antenna characteristics are calculated using the method of moments (MoM), with wire grid models and examined in terms of component arrangement, and terminal isolation. It is found that maximum isolation is obtained when the current path of the wire antenna is where the current exciting the H-pol element is cancelled. Consequently, both component antennas may work independently even in the composite form. The quasi-monopole pattern is also confirmed for each polarization     

On the design of optimum radar waveforms for clutter rejection

The problem to be considered in this paper is that of designing radar signals and receivers that are optimum for detecting a point target masked by a background of clutter returns and thermal noise. The problem of choosing an optimum signal when no constraints are placed on the type of signals allowed is discussed briefly, but the remainder of the paper is restricted to signals and receiver impulse responses that are uniformly spaced, phase and amplitude-tapered pulse trains. Expressions for the signal-to-interference ratio obtained when a signal is used with its matched filter (pm/) and with the optimum filter or clutter filter(rho_{cf})are then derived together with an explicit expression for the clutter filter. An iterative technique for maximizingrho_{cf}is devised. This scheme has the useful property that it generates a sequence of signals whoserho_{cf}'s form a monotone, nondecreasing sequence. This is followed by an application of the calculus of variations to derive the Euler equations for the stationary points ofrho_{cf}andrho_{mf}. The form of the Euler equations suggests iterative techniques for their solution; in fact, the technique suggested for the solution of the Euler equation associated withrho_{cf}is essentially the iterative technique that was described above.     

On the optimum directivity of antenna consisting of arbitrarily oriented dipoles

The optimum directivity of antennas consisting of arbitrarily oriented dipoles is examined. This is done with the help of formulas found by the Gram-Schmit method of orthonormalization of the base, which includes the intensity of the electric field. Some examples follow.     

Earpiece cord antenna for DVB-H reception in wireless terminals

A modified earpiece cord is proposed and evaluated as a wideband antenna for DVB-H reception. By winding the cord into a high-impedance RF choke at one-quarter wavelength distance from the handset connection, a stable wideband input impedance is achieved. Using two-chip components for impedance matching, the complete UHF band can be covered with >35% antenna efficiency. Measured and simulated results are presented with good agreement.     

稳定转台传动系统优化设计及试验研究

稳定转台传动系统是雷达产生转动、维持平衡、传递数据和信号的重要部分,它的质量好坏直接影响到雷达的性能。本文从几个方面对稳定转台传动系统优化设计问题进行了研究和分析,有针对性地提出了解决方法,并通过试验进行了验证。试验表明,本文提出的方法对解决这些问题切实有效。     

一种可用于北斗卫星信号接收的微带天线设计

基于微带天线技术提出一种应用于北斗导航系统的新型天线设计。该天线采用FR-4衬底上的弯曲微带和含有通孔的微带贴片实现。天线的小型化设计可使其更好地应用于北斗导航之中。与此同时,与常规的天线相比,该天线拥有更好的反射系数。实验结果表明,这里设计的天线非常适用于北斗导航系统,进而可应用于车辆导航系统之中。     

Compact varactor-tuned meander line monopole antenna for DVB-H signal reception

A compact varactor-tuned meander line monopole antenna for DVB-H signal reception is presented. The operating frequency of the antenna is continuously tuned over the frequency range of the DVB-H standard 470-702 MHz. The antenna has an omnidirectional radiation pattern and covers the frequency range with requisite impedance bandwidth and gain level. The antenna element occupies a very small volume (0.7 cm³ ) and can be used in 40 x 100 x 10 mm devices.     

The performance of antenna amplifiers used for terrestrial DTV reception

Measurements were made on currently available commercial antenna-mounted amplifiers to ascertain their effects on DTV reception. Data regarding amplifier gain and noise figure is presented, followed by data illustrating the effects of intermodulation within the tested amplifiers as shown by the change in the D/U interference ratio of a control DTV receiver, and ending with observations regarding amplifier environmental sensitivity. Also presented are the inconsistencies between the performance of commercially available amplifiers, advertised to the public for use with television, and the performance claims made by the manufacturers of such amplifiers.     

A novel scheme for reception using an active microstrip antenna

An unique aspect of the injection-locked active microstrip antenna incorporating a Gunn diode, i.e., the variation of the device current within the lock band, is exploited for the demodulation of an FM microwave signal. A simple experimental arrangement has been presented to demonstrate the demodulation performance of the receiver even in a multichannel environment. Using two such separate antennas as transmitter and receiver, a two-way short-range communication system has been demonstrated that may be suited for certain commercial and military applications     

Noise measure for the optimum design

Using the new circuit parameter, noise measure (N.M.), a circuit has been designed for the minimum noise figure and maximum gain by matching networks. Furthermore using the Smith chart and numerical values of the scattering parameters for a given microwave MESFET the values of matching elements have been determined and it is demonstrated that this approach yields an optimum design.     

Constraints for maximally flat optimum broadband antenna arrays

Frequency response shaping for the direct form pre-steered broadband (PB) antenna array processor is often achieved by imposing look direction constraints on the weights of the processor. This results in a linearly constrained optimization problem. To ensure a maximally flat spatial response of a specified order in the look direction of the PB processor, additional constraints known as derivative constraints can be further imposed on the weights. In general, derivative constraints corresponding to necessary and sufficient (NS) conditions for a maximally flat spatial power response can result in a quadratic equality constrained optimization problem. We transform the quadratic NS derivative constraints to parameterized linear forms. These parameterized linear forms allow the global optimum of the quadratic equality constrained optimization problem to be obtained easily. They also provide a general framework for deriving new sets of derivative constraints which correspond only to sufficient conditions for a maximally flat spatial power response. These sufficient derivative constraints are useful for real-time processing because of their reduced computational requirements and because they ran deliver performance comparable to the NS derivative constraints     

Performance bounds for optimum and suboptimum reception under Class-A impulsive noise

The transmission over the memoryless additive white Class-A noise (AWCN) channel is considered. For uncoded transmission, an exact expression for the symbol error rate is derived. For coded transmission, the Chernoff bound on the pairwise error probability is calculated and the performance achieved on the real and the complex AWCN channels is compared. Moreover, a low-complexity, suboptimum decoding metric is derived and analyzed employing the cutoff rate as a performance criterion.     

A new active phased array antenna for mobile direct broadcastingsatellite reception

This paper represents a new active phase array antenna for a Ku-band mobile service that will be possible with satellite broadcasting. The main idea for the antenna is to use minimum active array elements with cost-effective one-dimensional subarrays with an inclined pencil beam structure for a 34 dBi gain. For this antenna, we also used the squint beam tracking algorithm. This tracking gives a different way to the traditional monopulse tracking method in tracking capability. The electronic scanning angle of the beam peak in this antenna is over ±12° wide only with 20 phase shifter elements for its scan ranges. This antenna with the attractive hybrid-tracking concept has about 142 times less array elements than antennas with a two-dimensional array     

Blind reception of multicarrier DS-CDMA using antenna arrays

An asynchronous, multicarrier direct-sequence code-division multiple-access (DS-CDMA) array receiver is proposed based upon blind, composite channel vector estimation. Due to the fact that the combined effect of all received paths is estimated, the total number of paths can be greater than the number of antennas in the receiver array. Furthermore, the proposed approach is not limited by multipath coherency. The receiver is classified as an interference cancelling zero-forcing receiver, and multicarrier operation in a frequency-selective channel means that its performance can exceed that of a single-carrier array DS-CDMA. The effectiveness of the proposed approach, even in the presence of strong interference, is demonstrated by computer simulation studies.