The Performances of the Antennas in Active/Passive Compounded Guidance Part I: Broad-Band Antennas and Passive Direction-Finding Schemes

Part one of a two-part paper analyses the performances of the ultra broad-band antennas which are the key components in the broadband passive guidance in details. Two kinds of passive direction-finding schemes which have wide fields of vision are raised and analyzed in this part. Because of the uncertainty of the phase-centers of the antennas, the usual amplitude sun-subtraction monopulse technique can not be used to find the direction of a radiative source in a wide frequency range. A beam-operation network which can be used to form two secant beams from single broad-band spiral antenna is able to applied in the amplitude-monopulse system. An algorithm to eliminate the angle-confusion in the amplitude-phase monopulse direction-finding system is also studied.     

宽带被动导引头天线系统性能分析

详细讨论了宽带被动导引头中的关键部件－超宽频带天线的性能，并在此基础上分析了三种具备大视角特性的被动测角方法。由于宽带天线没有确定的相位中心，因此不能采用通常的振幅和差式单脉冲法进行宽频带测角。本文提出的波束运算网络可用于一个宽带螺旋天线同时得到两个交叉波束的振幅－振幅式单脉冲系统中。此外，对比幅相干测向法中的测角模糊问题也进行了研究。     

可见光多天线空分键控技术研究

空分键控是一种新型的空间复用技术,每个时刻只有一个发送天线工作,携带信息的是天线的位置而非发送符号本身,因此该种方法频带利用率较低。为了提高频带利用率,基于广义空间调制的概念,提出了光多天线空分键控调制方法,这种调制方式中每个时刻有多个天线同时工作。首先建立了可见光通信中的多天线空分键控系统模型,并对其误码率性能进行了分析,然后由此为依据提出了一种基于最小距离最大化准则的天线选择算法以获得误码率性能的增益,最后通过蒙特卡罗仿真验证了该天线选择方法的有效性。      

低成本有源相控阵天线研究

研究了有源相控阵天线的低成本设计思路和数字技术新方法。首先详细地分析了有源相控阵天线的系统构架和成本组成;然后从系统总体的角度,探讨了低成本数字阵列相控阵天线设计方法;最后提出了采用宽带宽角扫描的可重构设计技术来降低有源相控阵天线的成本。提出的有源相控阵天线低成本设计新方法具有很好的工程实用价值和科学意义。     

Non-Foster Impedance Matching of Electrically-Small Antennas

Electrically-small antennas present high-Q impedances characterized by large reactances and small radiation resistances. For such antennas, the effectiveness of passive matching is severely limited by gain-bandwidth theory, which predicts narrow bandwidths and/or poor gain. With receivers, the inability to resolve this impedance mismatch results in poor signal-to-noise (S/N) ratio, as compared to using a full-size antenna. With transmitters, the consequence is poor power efficiency. However, in many applications full-size antennas are impractical, and a means is required to effectively match their electrically-small counterparts. This paper presents the technique of non-Foster impedance matching, which employs active networks of negative inductors and capacitors to bypass the restrictions of gain-bandwidth theory. We first review the origins and development of non-Foster impedance matching, and then present experimental results for the non-Foster impedance matching of electrically-small dipoles and monopoles. For receivers, our best measurements on the antenna range demonstrate up to 20 dB improvement in S/N over 20–120 MHz; for transmitters, we show a power efficiency improvement which exceeds a factor of two over an 5% bandwidth about 20 MHz with an average signal power of 1 W to the radiation resistance.      

Active Stabilization of Vehicle-Mounted Phased-Array Antennas

In this paper, a novel hybrid tracking method for mobile active phased-array antenna systems is developed. The proposed technique consists of a mechanical stabilization loop and a direction-of-arrival (DOA) estimation algorithm, which is based on electronic beamforming. Compared with other tracking methods, the proposed method requires only one low-cost yaw rate sensor. The method utilizes electronic feedback from the phased-array antenna to compensate for the low-cost sensor irregularities. The effectiveness of the proposed tracking method is demonstrated by measured performance of a fast-moving ultra-low-profile phased-array satellite terminal, which uses the proposed approach. The field test results confirm that the hybrid tracking mechanism can nullify the base vehicle yaw disturbances up to $60^{circ}/hbox{s}$ and $85^{circ}/hbox{s}^{2}$ and keep the azimuth angle error at less than the permissible bound of $[-1^{circ}, +1^{circ}]$. Although performance of the proposed tracking system is verified in the context of a mobile satellite television reception system, the basic principles can be applied to any tracking system that employs phased-array antennas. The mobile satellite Internet terminal is an important example.      

A Hybrid Method of Moments?GTD Technique for Computing Electromagnetic Coupling Between Two Monopole Antennas on a Large Cylindrical Surface

The problem of analyzing the electromagnetic interference (EMI) between two electronic systems when their antennas are located on or near large scattering objects is a difficult one. In this paper, a hybrid technique for combining the method of moments with the geometrical theory of diffraction (GTD) is extended to account for the mutual coupling between two monopole antennas on a large circular cylinder by means of curved surface-wave diffraction. The results of this technique are compared to those of an analysis program used by the United States Air Force which predicts electromagnetic coupling between aircraft antennas. The close agreement between the results of these two different analysis techniques serves to validate both computer programs.     

A DSFBC-OFDM for a Next Generation Broadcasting System With Multiple Antennas

In this paper, we propose a differential space-frequency block code-orthogonal frequency division multiplexing (DSFBC-OFDM) scheme as a multiple-input multiple-output (MIMO) transmission technique for next generation broadcasting system. A linear decoding method for DSFBC, which performs comparably to the ML decoding method, is derived for the cases of two or four transmit antennas. A simple table lookup method is proposed to improve the efficiency of the encoding/decoding process of DSFBC for the case of non-constant modulus constellations. This not only reduces the computational load, but also removes the necessity of channel estimation. Also, synchronization techniques with a DSFBC-encoded phase reference symbol (PRS) are discussed. Finally, an MIMO channel model for the next generation broadcasting system is developed by extending the 3GPP MIMO model to fit broadcasting environments. The MIMO channel model is then used to compare BER performances of differential space block code schemes for various channel environments. Simulation results show that the DSFBC-16QAM scheme using either four transmit antennas with one receive antenna or two transmit antennas with two receive antennas achieves a performance gain of 12 dB, with a data rate twice faster than that of the conventional DQPSK scheme     

相控阵天线的设计与FDTD分析

基于工作频率在1.79 GHz的微带天线,首先研究了移相器的设计方法,然后利用两种不同方法实现的移相器,分别设计出了相控阵天线。通过FDTD进行建模和仿真实验,计算了相控阵天线在不同扫描角的远场辐射方向图,分析了实验误差,得出了结论,所设计的相控阵天线结构简约,主瓣尖锐,最大扫描角大于45°。     

Broadband Active Receiving Patch With Resistive Equalization

The active integrated antenna (AIA) concept has been applied to design a broadband receiver front-end. A design procedure for active broadband patch antennas based on resistive equalization is presented. The use of the AIA has allowed the design of efficient RF front-ends by increasing its effective gain, noise figure, and merit . In addition to improving the classical parameters, the resistive equalization technique allows enlarging the bandwidths of the active antenna parameters versus the corresponding ones in passive antennas. A receiving patch antenna (with one amplifying stage) with a measured noise figure lower than 0.6 dB in a bandwidth over 38% and an effective gain improvement of 13 dB over the corresponding passive antenna has been achieved. The -parameter has also been measured for both the active and passive antenna, resulting in a relative planar of 16 dB/K, with a ripple of 0.5 dB, over a 30% bandwidth for the active antenna versus a of 22 dB/K for a typical front-end with a passive antenna over 20% bandwidth.     

主被动导引头数字中频接收机设计与实现

针对目前复杂的战场环境和数字化技术的发展，提出了数字化主被动复合制导这一新方向。文中首先分析了主被动导引头数字中频接收机的设计难点，提出了一种主被动导引头数字中频接收机的设计方案，详细介绍了其功能结构，最后分别论述了主被动导引头数字中频接收机的硬件设计和软件设计。该方案已应用于某型主被动复合导引头样机。     

两种宽缝超宽带天线的脉冲波形保真度比较

设计了两种小型宽缝结构超宽带天线,一种采用接地CPW馈电方式,另一种采用带状线馈电方式。结果表明这两种天线都有较宽的阻抗带宽。分析了两种天线的特性参数,并比较两种天线的增益和辐射特性,给出两种天线在远区场的脉冲波形比较,并得出不同天线结构对脉冲波形的保真度的影响,这对实际超宽带脉冲天线的设计与应用意义重大。     

基于微带天线的能量传输技术及其性能研究

对于安装在旋转部件上的监测系统来说,供能问题一直是一个难点。该文提出了一种基于微带天线的非接触式的能量传输技术,以代替传统的滑环或光电池等能量传输方法。该文以扭矩监测为应用背景,提出了能量传输系统的总体结构和天线馈源方案,并对天线的各种能量传输情况进行了研究,同时分析了旋转速度对能量传输的影响。     

Array Modeling for MM-Wave Active Integrated Antennas

The design of active integrated antennas operating in the millimeter-wave (mm-wave) range requires a two-fold analysis: on one hand, the electromagnetic modeling of large planar arrays; on the other hand, the characterization of the active devices. In this paper we face the former task, by presenting an efficient method for the calculation of the voltages induced on all the elements of a planar array by the input (gaussian) beam, and the evaluation of the impedance matrix of the array. These parameters, together with the modeling of the active devices, allow for a full characterization of the active integrated antenna.     

双频贴片天线研究与设计

无线通信的发展对天线(尤其是贴片天线)的各项性能提出了新的要求。与此同时，双频天线的应用也愈为广泛。总结了贴片天线的主要双频解决方案，包括正交模、多贴片、电抗性加载以及空气缝隙双频贴片等方式，并提出了相应双频贴片天线的适用场合。最后，结合HFSS仿真设计了一个双频双贴片天线，讨论了该天线特性，并对双频天线未来的发展趋势进行了展望。     

有源集成天线的谐波平衡法分析

本文首先利用矩量法计算平面馈电型微带贴片天线的输入阻抗,并对其进行实验测量;其次,使用谐波平衡法分析了以Ｃｕｎｎ管为振荡源的有源微带天线电路。在求解谐波平衡方程时采用Ｐｏｗｅｌｌ优化法,得出整体电路的振荡频率和振荡电压;再次,仍使用谐波平衡法对肖特基二极管与微带贴片天线集成的接收型有源天线进行大信号的小信号分析,同样经过优化,得出其在本振电压作用下,非线性部分的谐波电压以及在小信号电压作用下的变频     

平面左手结构在微波器件及天线设计中的应用

自从2001年首次实现人工左手媒质以来，人们一直致力于制作大带宽、低损耗、易集成且具有左手特性的微波器件与天线．本文着重介绍两种基本的左手结构在平面微波电路中的应用，其一是左右手复合结构，其二为互补开口谐振环结构．近年来，这两种结构在微波器件及天线设计中得到广泛研究与应用．本文总结了国内外在这两个方面的研究进展，并结合我们在这方面所取得的成果，对平面左手电路的原理和应用进行了详细分析和说明。     

Passive intermodulation on large reflector antennas

In this work, an analytical model for the study of passive intermodulation (PIM) on large reflector antennas is presented. Passive intermodulation, in the scattered field, arises when the scatterer is nonlinear, or when it presents junctions connecting linear materials. Its presence causes a degradation of some antenna parameters and, especially, the cross-polar level, which may rise by several tens of dB. It would then be useful to develop a technique to predict its influence, in order to take appropriate steps during antenna design. A heuristic model for the junction problem has previously been derived and validated with measurements in a time-domain physical optics (TD-PO) framework. These results are applied here to a TD-PO analysis of reflector antennas, in particular, for a satellite-communication antenna and for a radio-astronomy antenna.     

A Time/Frequency Model of Ultrawideband Antennas

A new approach to model ultrawideband (UWB) antennas is proposed. A mathematical analysis of transmission through an UWB system in terms of transfer function and impulse response is proposed. The analysis allows the separation of the transmitting and receiving antenna characteristics, using a consistent treatment with other UWB and earlier narrowband analysis techniques. A parametric modeling is added to provide efficient directional time-frequency models of UWB antennas. The technique is demonstrated through simulation and experiment.