Experimental study of wideband printed annular slot antenna with cross-shaped feedline

A annular slot antenna with cross-shaped feedline has been investigated experimentally to obtain a large bandwidth enhancement. The voltage standing wave ratio (VSWR), radiation pattern, and antenna gain of this configuration are presented. Although the use of a high relative permittivity (/spl epsiv//sub r/=4.3) substrate usually restricts the operation bandwidth, the radiation resistance also was a low value. The measured bandwidth is /spl sim/ 108.4% (2.0 /spl ges/ VSWR).     

Effect of soft and softer handoffs on CDMA system capacity

The effect of soft and softer handoffs on code-division multiple-access (CDMA) system capacity is evaluated for unsectorized and sectorized hexagonal cells according to an average bit energy-to-interference power spectral density, which corresponds to a bit-error rate (BER) of 10^-3. The effect of imperfect sectorization on sectorization efficiency is also considered. On the reverse link, there is no capacity loss as no extra channels are needed to perform soft handoff, while the macrodiversity provided by soft handoff can improve the reverse-link quality and extend the cell coverage. On the forward link, when soft handoff is employed in unsectorized cells, the capacity loss due to two traffic channels assigned to a user in the handoff zone is 0.2% or 1.1% for a voice activity factor of 3/8 or 1/2, respectively. As the forward-link capacity is higher than that of the reverse link, this small capacity loss does not affect the system capacity. For sectorized cells having three sectors per cell, there are overlapping coverage areas between sectors, where mobiles in these areas are subjected to an increase in cochannel interference. For an overlapping angle of 5°, the sectorization efficiency is 0.96 and 0.7 for the reverse-link and forward-link systems, respectively. When soft and softer handoffs are employed, the forward-link sectorization efficiency is improved to 0.97. We find the application of soft and softer handoff improves not only the forward-link capacity, but also the signal-to-interference ratio (SIR) for mobiles near the cell and sector boundaries     

Reverse-link capacity of power-controlled CDMA systems with beamforming

In this paper, reverse-link capacity, in terms of user capacity and Erlang capacity, of a direct-sequence code-division multiple-access (DS-CDMA) system with the use of beamforming is investigated. Signal-to-interference ratio (SIR)-based power control is assumed and both transmit and receive beamforming are considered. Instead of using tedious iterative methods to evaluate user capacity, a simple closed-form capacity expression with respect to antenna gains, a target SIR, and the CDMA processing gain is derived. Numerical results indicate significant capacity improvement with beamforming. The impact of the estimation errors of arrival angles on the capacity is examined. The joint use of a RAKE receiver and beamforming is investigated and the capacity expression for CDMA systems with multiclass services is also derived.     

5.8-GHz circularly polarized rectifying antenna for wireless microwave power transmission

This paper reports a new circularly polarized (CP) high-gain high-efficiency rectifying antenna (rectenna). The CP rectenna can be rotated and still maintain a constant dc output voltage. The high-gain antenna has an advantage of reducing the total number of rectenna elements to cover a fixed area. The rectenna is etched on Rogers Duroid 5870 substrate with /spl epsi//sub r/=2.33 and 10 mil thickness. A high-gain dual-rhombic-loop antenna and a reflecting plane are used to achieve a CP antenna gain of 10.7 dB and a 2:1 voltage standing-wave ratio bandwidth of 10%. The rectenna's pattern has an elliptical cross section with orthogonal beamwidths of 40/spl deg/ and 60/spl deg/. The rectenna circuit has a coplanar stripline band-reject filter that suppresses the re-radiated harmonics by 20 dB. A highly efficient Schottky diode is used for RF-to-dc conversion with an efficiency of approximately 80% for an input power level of 100 mW and a load resistance of 250 /spl Omega/.     

Millimeter-wave twin tapered-slot antenna

A millimeter-wave twin tapered-slot antenna on standard substrate is presented. The twin antenna is constructed by single tapered slot antennas (TSA), printed on opposite sides of a low dielectric constant (/spl epsiv//sub r/=2.2) substrate. The structure is fed by a rectangular waveguide followed by a broadband finline-to-slotline power splitter. The radiation pattern of the single TSAs is improved by corrugating the taper contour by a series of short-circuited stubs. With this method, antennas three times thicker compared with conventional TSA designs can be realized with an almost unchanged performance. Experimental radiation patterns of a 65-GHz twin TSA in comparison to both simulation results and corresponding single TSA measurements are presented. A measured twin antenna gain of 17.5 dB indicates efficient radiation.     

Use of Adaptive Sectorisation for Capacity Enhancement in CDMA Cellular Systems with Non-Uniform Traffic

This paper discusses the application of adaptive sectorisation in the capacity enhancement of a CDMA cellular system dealing with non-uniform traffic. It considers the particular case where the traffic distribution consists of isolated areas of congested traffic called Hot Spots (HS). It is envisaged that the traffic density inside a HS is many more times that outside the HS. A more even traffic distribution among sectors is attempted by re-adjustment of sector boundaries using finite antenna beam switching. System capacity is estimated on the basis of tolerable interference in a sector taking into account of both intrasector and intersector interference in a multicell environment. Interference is evaluated under the assumption of perfect power control in the uplink. Normal propagation environment is assumed in the cell that allows path losses and shadowing losses in the mobile radio signal. Variation in the antenna gain is also accommodated by taking appropriate radiation pattern into account. It is shown that successive sector adjustment with increasing HS traffic intensity can deter call blocking in the HS sector. It is also shown that a significant improvement in system capacity could be obtained with adaptive sectorisation particularly when the HS user density is several orders of magnitude higher than that outside the HS.     

Performance of wireless CDMA with M-ary orthogonal modulation andcell site antenna arrays

An antenna array-based base station receiver structure for wireless direct-sequence code-division multiple-access (DS/CDMA) with M-ary orthogonal modulation is proposed. The base station uses an antenna array beamformer-RAKE structure with noncoherent equal gain combining. The receiver consists of a “front end” beamsteering processor feeding a conventional noncoherent RAKE combiner. The performance of the proposed receiver with closed loop power control in multipath fading channels is evaluated. Expressions for the system uncoded bit-error probability (BEP) as a function of the number of users, number of antennas, and the angle spread are derived for different power control scenarios. The system capacity in terms of number of users that can be supported for a given uncoded BEP is also evaluated. Analysis results show a performance improvement in terms of the system capacity due to the use of antenna arrays and the associated signal processing at the base station. In particular, analysis results show an increase in system capacity that is proportional to the number of antennas. They also show an additional performance improvement due to space diversity gain provided by the array for nonzero angle spreads     

Antenna selection in a multisector packet radio system

To improve performance on the inbound (mobile-to-base-station) channel of a packet radio system consisting of a base station and a number of mobile users, the area around the base station is divided into M sectors. Signals originating from users in different sectors are received by different directional antennas at the base station. It is shown that, if the number of receivers at the base station is less than M, the selection of the antennas to be connected to the receivers becomes an issue. A number of antenna selection schemes are compared for three different channel models, assuming an ideal antenna pattern. It is found that the scheme that selects the antennas with the largest received signal powers is nearly optimum. The effects of a more practical nonideal antenna pattern are discussed     

CLIP antenna for wireless bluetooth applications

In this paper, a novel design for a coplanar waveguide antenna is developed that consists of two U-shaped slots. The antenna is named CLIP. The antenna was designed for a central frequency of 2.4 GHz, with an input impedance of 50 /spl Omega/. The antenna dimensions represent a 72% size reduction compared to a conventional microstrip rectangular-patch antenna. The measured antenna bandwidth was about 11%, while its gain was about 17 dB. These values are fairly acceptable in all wireless communication systems. The antenna configuration has a bidirectional radiation pattern, while a unidirectional radiation pattern was achieved by using a /spl lambda//sub 0//4 reflector with a metal plate. A 2/spl times/2 multi-element sub array was implemented to widen the application area. The mutual coupling between adjacent elements was low. Orthogonal-plane coupling between adjacent elements was introduced to increase the reduction in the mutual coupling. The mutual coupling level was reduced to less than -23 dB in all coupling planes. The CLIP antenna element and arrays were fabricated. Experimental measurements showed very good performance, which agreed well with simulation results.     

Capacity, throughput, and delay analysis of a cellular DS CDMAsystem with imperfect power control and imperfect sectorization

An analytical model is developed to evaluate the performance of a cellular slotted DS CDMA system in terms of user capacity, throughput, and delay for the reverse link, i.e., from mobile to base station, considering interference from both home cell and adjacent cells. The user capacity is studied for voice communications and the throughput and delay are investigated for data communications. The effect of both imperfect power control and imperfect sectorization on the performance is investigated. It is shown that the system is rather sensitive to small power control errors and that voice activity monitoring and sectorization are good methods to improve the performance of cellular DS CDMA systems     

Vertical sectorization in self-organizing LTE-advanced networks

Cellular radio networks continuously evolve to respond the exponential growth in data traffic volume in mobile communications. Active antenna technology contributes to this evolution by introducing vertical sectorization, which splits the horizontal sector into two subsectors with respect to the elevation plane and doubles the number of cells that can be deployed. However, in order to guarantee a reliable and near-optimal operation of vertical sectorization in a system that applies universal frequency reuse, such as LTE-advanced, co-channel interference mitigation is essentially needed. In this article we propose a decentralized self-optimization method that can be used to mitigate the undesirable inter-cell interference by self-tuning the electrical antenna downtilt toward the optimal antenna elevation angle. The performance evaluations for the proposed self-optimization method are carried out for both coordinated and uncoordinated subsector transmission scenarios within the LTE-advanced framework using a dynamic LTE-advanced compliant system level SON simulator. Based on the extensive performance evaluations carried out for a realistic urban scenario, it is found that self-optimization improves the vertical sectorization performance 25 % in terms of virtual load. Furthermore, the performance gain reaches up to 30 % when vertical vectorization is provided with dynamic point selection and muting feature. Therefore, the article concludes that in LTE-advanced networks vertical sectorization can largely benefit from the antenna self-optimization and outperform the traditional horizontal sectorization approach with low algorithmic complexity.     

A half-moon antenna

This work presents a half-moon antenna (HMA), which is composed of two semi-circular top and bottom conducting plates joined by a rectangular conducting plate. The HMA has a wide radiation beam. Radiation in the y-z plane (in the E plane) is hemispherical with a half-power beam width (HPBW) of more than 200/spl deg/. Radiation in the x-y plane (in the H plane) forms a sector beam with an HPBW of more than 100/spl deg/. To reduce the backward radiation and improve the gain, chokes are added to the HMA. An increase in the gain of approximately 1 dB is obtained. In order to obtain a tilted beam, the radius of the bottom plate is reduced. The maximum beam direction of the tilted beam /spl theta//sub max/ is not sensitive to frequency. Within a frequency range of 11 to 14 GHz (24%), /spl theta//sub max/=167/spl deg//spl plusmn/2/spl deg/. The gain is found to be G=9.5/spl plusmn/0.5 dBi within this same frequency range.     

Adaptive cell sectorization for CDMA systems

Given the user distribution in a cell, we investigate the two problems of how to appropriately sectorize the cell such that we minimize the total received power and the total transmit power of all the users, while giving each user acceptable quality of service in both cases. For the received power optimization problem, we show that the optimum arrangement equalizes the number of users in each sector. The transmit power optimization is formulated as a graph partitioning problem that is polynomially solvable. We provide an algorithm that finds the best sectorization assignment as well as the optimal transmit powers for all the users. The computational complexity of the algorithm is polynomial in the number of users and sectors. For both the received power optimization and the transmit power optimization, under nonuniform traffic conditions, we show that the optimum arrangement can be quite different from uniform cell sectorization (equal width sectors). We also formulate and solve the transmit power optimization and cell sectorization problem in a multicell scenario that would improve the capacity of a hot spot in the network. We observe that, with adaptive sectorization, where the sector boundaries are determined in response to users' locations, received and transmit power savings are achieved, and the number of users served by the system (system capacity) is increased compared to uniform sectorization of the cell     

Novel integrated GPS/RKES/PCS antenna for vehicular application

This letter presents the design of a novel integrated global positioning system (GPS)/remote keyless entry system (RKES)/personal communication system (PCS) antenna for vehicular application. The GPS (1575.42 /spl plusmn/ 1.023MHz) antenna element is a corner truncated microstrip patch providing circularly polarized broadside radiation pattern. The normal mode helical and monopole antennas are combined into one for RKES/PCS (447.7375MHz/1750-1870MHz) services. The proposed antenna satisfies all the bandwidth and gain requirements for GPS and RKES/PCS services. Good radiation characteristics for vehicular application have also been obtained.     

Resource pooling and effective bandwidths in CDMA networks withmultiuser receivers and spatial diversity

Much of the performance analysis on multiuser receivers for direct-sequence code-division multiple-access (CDMA) systems is focused on worst case near-far scenarios. The user capacity of power-controlled networks with multiuser receivers are less well-understood. Tse and Hanly (see ibid., vol.45, p.541-657, 1999) have shown that under some conditions, the user capacity of an uplink power-controlled CDMA cell for several important linear receivers can be very simply characterized via a notion of effective bandwidth. We show that these results extend to the case of antenna arrays. We consider a CDMA system consisting of users transmitting to an antenna array with a multiuser receiver, and obtain the limiting signal-to-interference (SIR) performance in a large system using random spreading sequences. Using this result, we show that the SIR requirements of all the users can be met if and only if the sum of the effective bandwidths of the users is less than the total number of degrees of freedom in the system. The effective bandwidth of a user depends only on its own requirement. Our results show that the total number of degrees of freedom of the whole system is the product of the spreading gain and the number of antennas. In the case when the fading distributions to the antennas are identical, we show that a curious phenomenon of “resource pooling” arises: the multiantenna system behaves like a system with only one antenna but with the processing gain the product of the processing gain of the original system and the number of antennas, and the received power of each user the sum of the received powers at the individual antennas     

A cavity-backed rectangular aperture antenna with application to a tilted fan beam array antenna

A rectangular aperture of A/sub x//spl times/A/sub y/, cut in the top conducting plate of a triplate transmission line and backed by a cavity, radiates a tilted beam off the direction normal to the aperture. The mechanism of the radiation is explained using the Poynting vector distribution above the aperture and the phase distribution of the electric field over the aperture. The tilt angle is calculated as a function of side length A/sub x/ for a representative value of A/sub y/=18 mm=0.747/spl lambda//sub 12.45/, where /spl lambda//sub 12.45/ is the wavelength at a test frequency of 12.45 GHz. A tilted beam of approximately 27/spl deg/ is realized at A/sub x//A/sub y/=8/9 with a gain of approximately 8 dB. Using this value of A/sub x//A/sub y/, an array antenna composed of rectangular cavity-backed aperture elements is investigated. The array forms a tilted fan beam without phase shifters. The frequency responses of the gain and input impedance are discussed.     

一种利用相控天线阵综合扇区波束的方法

提出一种利用遗传算法优化得到的阵列天线综合扇区方向图的方法，并分析了其性能及对误差的敏感度。该阵列可用于TD-SCDMA系统实现分扇区技术和波束赋形技术的结合使用。     

Design of small and low-profile antenna for satellite digital audio radio system

The design and optimisation of a small and low-profile antenna for the satellite digital audio radio system using a nondominated sorting genetic algorithm is presented. A fairly omnidirectional elevation gain pattern over -60/spl deg/相似文献   

Low profile diversity antenna for MIMO applications

A low profile diversity antenna for MIMO application is introduced. The design is based on a double folded dipole antenna filled with a slab of ceramic of /spl epsiv//sub r/=6. Two diversity antennas operating at 5.2 GHz are designed and implemented on a handset for IEEE.11a wireless systems. The isolation is found to be better than 20 dB in both measurement and simulation and measured bandwidth is about 250 MHz at -10 dB. Simulated and measured radiation patterns are close to each other. The envelope cross-correlation is calculated to be much less than 0.1 and the ratio of the mean effective gain between the antennas is close to unity.     

Phase Diversity for an Antenna-Array System With a Short Interelement Separation

This paper presents a simple procedure of obtaining a diversity gain in an antenna-array system with a short interelement separation, typically less than the carrier wavelength. The new technique provides a diversity gain through a noncoherent combination of received signals at each antenna element. The diversity gain arises because, as the number of signal components of the received signal at each antenna element becomes large enough and as the arrival angle of each signal component is distinct from one another, which is a general signal circumstance in most practical code division multiple access (CDMA) signal environments, the amplitudes of the received signals become nearly independent due to the phase difference among the received signals. The diversity gain was referred to as ldquophase diversityrdquo in this paper. The proposed technique is first theoretically analyzed to estimate the performance in terms of pseudorandom-noise-code acquisition, which is verified through extensive computer simulations. Then, through the experimental results that are obtained from a CDMA array-antenna base station system, it has been shown that the performance of noncoherent detection is proportionally improved to the number of antenna elements.