Synthesis of multi-radial line antenna for HIPERLAN

A new antenna concept - the multi-radial travelling wave line antenna - that achieves a broadband conical radiation pattern suitable for use in multiple C-band wireless computer networks is presented.     

Miniaturised microstrip antenna for MMIC applications

A novel miniaturised quarter wavelength, H-shaped antenna which will find applications in monolithic microwave integrated circuit (MMIC) design is presented. The antenna occupies approximately one tenth of the substrate area of a half wavelength patch antenna. The effect on the resonance frequency, bandwidth and gain of the antenna are reported     

An adaptive technique for transmit antenna diversity with feedback

Transmit antenna diversity (TAD) has been employed for third-generation wireless systems. We propose an adaptive technique for TAD with feedback. It is shown that the proposed adaptive technique can efficiently increase the number of transmit antennas without significantly increasing the feedback bit rate under ideal conditions. As a result, we can increase the number of transmit antennas and expect a performance improvement. Unfortunately, the proposed adaptive technique suffers from channel variation and error propagation due to feedback error. From this, the use of the adaptive technique shall be limited: it can be effective for indoor communications and for pedestrians with a reliable feedback channel     

毫米波矢量调制器及其在有源相控阵天线中的应用

矢量调制器芯片作为一种可以同时对载波进行相位和幅度调制的新型电路,能够替代传统的数字移相器和数字衰减器用在有源相控阵系统中.先设计了一款工作在Ka波段毫米波单片矢量调制器,在片测试结果显示可以实现- 12～-40 dB的幅度调制与360°的相位调制.然后设计了一个Ka波段1×8阵有源相控阵天线,改变矢量调制器的控制电压...     

70-GHz-band MMIC transceiver with integrated antenna diversity system: application of receiver-module-arrayed self-heterodyne technique

Our proposed millimeter-wave self-heterodyne transmission technique is a simple and cost-effective solution to frequency stability problems in millimeter-wave access systems. In addition, this technique enables integration of a high-sensitivity receiver with a combining antenna diversity system that is approximately as effective as a maximal-ratio-combining antenna diversity system for all directions of signal arrival. We explain how our newly developed 70-GHz-band transceiver using the millimeter-wave self-heterodyne transmission technique with a receiver-module array can greatly improve receiver sensitivity for all directions of signal arrival i.e., without affecting the signal reception beam pattern and how this can solve the signal-fading problem in a multipath signal propagation environment. We also theoretically demonstrate that receiver sensitivity improves in proportion to the number of elements in a receiver-module array, and experimentally confirm this using an experimental 70-GHz-band monolithic microwave integrated circuit transceiver with a 4/spl times/2 receiver-module array. We show that millimeter-wave signal propagation can be modeled using a two-path model, and that serious signal fading depends on the transceiver height and transmission distance. Carrier and modulated signal transmission experiments using our developed transceiver have revealed that use of a receiver-module array greatly reduces the signal-fading problem in a multipath signal propagation environment. In the signal transmission experiment, we succeeded in transmitting an orthogonal frequency-division multiplexing signal over a 4-m transmission distance with bit-error-free performance.     

An AlGaAs/InGaAs pseudomorphic HEMT modulator driver IC with lowpower dissipation for 10-Gb/s optical transmission systems

An optical modulator driver integrated circuit (IC) has been developed for 10-Gb/s optical communication systems. To achieve both high-frequency (HF) operation and low power dissipation, 0.2-μm T-shaped gate AlGaAs/InGaAs pseudomorphic high electron-mobility transistors (HEMTs) have been employed for their large transconductance g_m of 610 mS/mm and high cutoff frequency f_T of 67.5 GHz. In addition, optimizing input logic swing, switching transistor size in the output driver, and using cascode-current mirror circuits with small output conductance enable power dissipation as low as 1 W to be achieved at a 10-Gb/s nonreturn-to-zero (NRZ) signal output with 3 V_p._p. This is the lowest value ever reported for power dissipation. As an additional function, the output-voltage swing can be controlled in the range from 2 to 3.3 V_p._p. by the current mirror circuit for the purpose of adjusting the optical-output-signal duty factor through an optical modulator     

分组旋转矢量法校正大规模相控阵天线

基于基本的旋转矢量法,提出了用于大规模相控阵天线校正的分组旋转矢量法.该方法同时旋转多个天线单元的信号源的相位,能够使被测信号的起伏显著增加.误差估计和仿真校正结果显示,该方法能够提高测量精度,改善校正效果.     

A K-band bi-phase modulator MMIC for UWB application

A 24-GHz-band, three-dimensional microwave monolithic integrated circuit (MMIC) bi-phase modulator, that is a combination of an active 0//spl pi/ splitter and a SPDT switch, is proposed and demonstrated. Comparing conventional K-band bi-phase modulators, this modulator is broadband, significantly MMIC compatible, and shrinks its chip area. A fabricated bi-phase modulator exhibits an area of 1.0/spl times/0.7mm/sup 2/ and a 1-dB bandwidth of nearly 10GHz. The SPDT switch is optimized in control-gate's time constant so that a very clear bi-phase modulated waveform can be generated from 1Gbps PN code. The insertion loss and the phase imbalance are 6.4 dB+/-0.6 dB and within 10/spl deg/, respectively, between 22GHz and 32GHz.     

一种高可靠性、低功耗单节锂电池保护电路

A single lithium-ion battery protection circuit with high reliability and low power consumption is proposed.The protection circuit has high reliability because the voltage and current of the battery are controlled in a safe range.The protection circuit can immediately activate a protective function when the voltage and current of the battery are beyond the safe range.In order to reduce the circuit’s power consumption,a sleep state control circuit is developed.Additionally,the output frequency of the ring oscillation can be adjusted continuously and precisely by the charging capacitors and the constant-current source.The proposed protection circuit is fabricated in a 0.5 m mixed-signal CMOS process.The measured reference voltage is 1.19 V,the overvoltage is 4.2 V and the undervoltage is 2.2 V.The total power is about 9 W.     

An accurate absolute gain calibration of an antenna for radio astronomy

The methods used to determine the absolute gain of an 80-square foot aperture horn-reflector antenna over a frequency range from 2.8 to 14.0 Gc, and in the absence of a high-level test range, are described. A "mirror" range, in which the size of the smooth reflecting surface required was relatively small, was used and the measurements were performed in the Fresnel zone of the antenna with corrections applied for the resulting gain reduction. These and other provisions reduced the probable error in the final values to about one per cent.     

Model based antenna array calibration for smart antenna systems

Model based antenna array calibration is used to remove the antenna array errors or predict the element patterns from the array manifold measured at a small number of directions. The experimental results show that this works very well for one sector angle region even in the presence of modelling errors     

Digital-to-RF conversion for a vector modulator

Digital technology lacks sufficient speed to support many high data rate applications at microwave frequencies. This is unfortunate since areas such as higher order modulation, predistortion, equalization, and demodulation could benefit in flexibility, modularity, and performance from digital architectures. However, use of radio frequency microwave technology permits the implementation of digital functions at these higher speeds and frequencies. This paper describes the implementation of a nonrecursive (finite-impulse response) filter in microwave technology     

110 GHz vector modulator for adaptive software-controlledtransmitters

A 110 GHz MMIC vector modulator for use in low-cost, high-performance, radar and communication transmitters is presented. The circuit consists of two push-pull (bi-phase) attenuators arranged in phase quadrature and has dimensions of 1.7× 1.4 mm². The fabricated MMIC has been characterized by means of static S-parameter measurements and shows a minimum insertion loss of 12 dB at 110 GHz, Using these measurements, the required baseband input levels for a 64-QAM static constellation were determined. These levels were then applied at 10 MSample/s, by an arbitrary waveform generator, to demonstrate a 60 Mb/s data rate transmitter operating at 110 GHz. To date, this represents the highest reported RF frequency for direct multilevel carrier modulation using monolithic technology     

An image-reject down-converter for 802.11a and HIPERLAN2 wireless LANs

An image-reject down-converter for IEEE 802.11a and ETSI HIPERLAN2 wireless local area networks was implemented in a low-cost 46-GHz-f _T silicon bipolar process. The circuit integrates a variable-gain low noise amplifier and a double-balanced mixer along with passive image rejection filters. It exhibits a 4-dB noise figure and a power gain of 23 dB. By reducing the low noise amplifier gain by 9 dB (thanks to a 1-bit gain control), the down-converter achieves an input 1-dB compression point of –14 dBm, while drawing only 23 mA from a 3-V supply voltage. The adopted filtering approach provides an image rejection ratio higher than 60 dB.     

Switched parasitic elements for antenna diversity

Switched parasitic elements provide a useful implementation of antenna pattern diversity. The basic principle is presented with some examples of wire antennas computed using the method of moments. The modeled diversity gain available from selection combining of uncorrelated signals is used to quantify the expected improvement relative to nondiversity antennas. The advantage of the switched parasitic concept is that it is a relatively simple system, which can give the adaptive antenna performance of many branch selection or switched diversity     

GaAs MMIC control functions for 3.7-4.2 GHz band active antenna

Annals of Telecommunications - This paper describes the realization of gain and phase control function in GaAs microwave monolithic integrated circuit (mmic.). The measured performances are...     

A high-speed adaptive antenna array with simultaneous multibeam-forming capability

A new type of adaptive beamforming antenna system architecture is proposed for multichannel wireless communications. Multibeam communication with high data throughput is accomplished using the proposed beamformer architecture. The system consists of analog mixers, a multitone direct digital synthesizer (DDS), and a digital signal processor (DSP) controller. The essential idea of multibeam forming is based on a multitone weighting scheme combined with analog-digital hybrid signal processing. While the real-time multibeam construction is realized by the analog mixer circuits and a DDS, the complicated adaptive beamforming and direction-of-arrival estimation algorithms are carried out by the DSP. In this architecture, only one beamformer circuit is required to handle multiple beams, leading to significant reduction in hardware counts. A 5.8-GHz eight-element adaptive beamforming array successfully demonstrates two-beam simultaneous beamforming with less than three degrees of peak and steering errors and more than 20-dB interference suppression. The test-bed exhibits successful two-channel data recovery at 25-Mb/s data throughput in each channel with binary phase-shift keying modulation, for simultaneous dual-beam reception. The bit-error-rate measurement validates the robustness of the communication quality under strong interferences.     

Performance analysis for transmit antenna diversity with/withoutchannel information

Transmit antenna diversity (TAD) for the downlink channel has been investigated to improve the performance of wireless communications using multiple transmit antennas. We present a performance analysis for TAD with/without channel information. For performance analysis, we use the pairwise error probability and cutoff rate. For the closed-loop TAD in frequency-division duplex (FDD) mode, the downlink channel information should be transmitted to the base station from the mobile station. The feedback channel information may be imperfect because of the feedback delay, quantization error, and feedback error. The impact of imperfect channel information has been considered to analyze the performance of the TAD. We also present a performance analysis for a TAD technique that does not use the channel information, called space-time transmit diversity (STTD). Looking at the cutoff rates for the TAD techniques, the trellis-coded modulation (TCM) has been considered for better performance. Simulation results are shown to see the impact of the TCM on TAD systems     

Single feed antenna with radiation pattern diversity

A vehicle diversity antenna system comprising a single-fed element together with a loaded parasitic element is described. Different termination loads on the parasitic element give rise to variations in the radiation patterns that are comparable with a four-element diversity system. There was good agreement between measured parameters and simulations.     

一种具有三阻带和高频截止特性的超宽带天线

为了有效抑制超宽带(UWB)通信系统和窄带通信系统之间潜在的干扰,设计了一款具有三阻带特性和高频截止特性的超宽带天线。天线总尺寸为33 mm×19 mm×1 mm。该天线的辐射单元由一个椭圆形的单极子和一个倒梯形结构组成,由50的矩形微带线馈电,接地板由一个矩形和一个开槽梯形结构构成。对天线进行加工并测试。结果表明,该天线在3.3~3.6 GHz处的阻带由辐射单元上的凹形槽产生,5.15~5.35 GHz和5.725~5.825 GHz处的阻带由微带馈线两旁的U形寄生单元产生,10.8 GHz高频处的截止特性是由微带线两旁对称的凹形寄生单元共同决定的。天线的测试结果与仿真结果吻合良好。