Wideband and low return loss coplanar strip feed using intermediatemicrostrip

A wideband and low return loss coplanar strip feed has been achieved using an intermediate microstrip line between coax and coplanar strip lines. The measured and calculated return loss are below 13 dB up to 18 GHz. An extended calculation using TDR data shows the return loss below 10 dB up to 30 GHz. This coplanar strip feed is very practical for feeding wideband electro-optic devices which use coplanar strip as the electrodes     

宽带毫米波全向天线研究

介绍了一种宽带毫米波不对称双锥喇叭全向天线。采用脊波导－同轴线过渡结构馈电网络，既解决了毫米波段双锥喇叭的电问题，又满足了天线输入端口必须为波导形式的实际工程要求。测试结果表明在２６－４０ＧＨｚ频带内，天线的全方向性和输入皮比均满足设计要求。     

一种星载UHF 频段小型化螺旋馈源设计

设计了一种应用于星载UHF频段小型化螺旋馈源，通过在每圈螺旋采用4个U型支节加载部分，使螺旋馈源周长变半径减小，通过减小螺距使得螺旋高度较低，与传统螺旋馈源相比，其纵向高度和径向尺寸减小了1/3和1/5，仿真和测试结果表明馈源具有良好的阻抗匹配特性和辐射特性，满足了设计要求。     

Ported coax intrusion detection sensor

A ported coax intrusion sensor is a perimeter line sensor that utilizes VHF leaky coaxial cable(s) to generate guided waves for detecting an object near the cable(s). The theory of operation for ported coax intrusion sensors is described, including: 1) the basic mechanism of generating guided waves, 2) the propagation characteristics of these guided waves, 3) the scattering mechanism of the guided wave by a target, 4) the scattered signal formulation at the receiver, and 5) the signal processing techniques for detecting a moving target.     

一种L波段背射模螺旋馈源

螺旋天线具有较好的宽频带圆极化特性,在L或S波段体积和增益都很适中,加工制造公差要求较低,因此在该频段螺旋天线得到了广泛的应用。由背射模螺旋构成的L波段宽带馈源具有结构简单,馈电、调试方便,口面遮挡小,频带宽(大于25%),可以承受大功率等优点,可以满足L或S波段测控系统对天线的要求。用该背射模螺旋馈源研制的前馈天线的口径效率超过了53%,第一副瓣小于-20 dB,在工程中得到了很好的应用。     

Comments on "Input Impedance of Coaxial Line to Circular Waveguide Feed" (Letters)

The author read with interest the above paper in conjunction with the correction to it. While attempting to apply Harrington's well-known development for a coax/rectangular waveguide transition to the coax/circular waveguide transition case, the authors arrived at results and conclusions which are highly erroneous and misleading. As explained below, (4b) and the expression for X/sub 1/ in (6), the reactance part of the input impedance, are both incorrect. Even if the expression for X/sub 1/ in (6) is corrected, the reactance series is clearly divergent.     

A 50-ohm input impedance for helical beam antennas

A helical beam antenna with uniform conductor size has a nominal impedance of 140 ohms. This may not be convenient for some applications. The purpose of this note is to call attention to the fact that the impedance can be adjusted to 50 ohms by increasing the conductor size close to the feed point at the ground plane. This lowers the characteristic impedance of the conductor-ground plane combination (acting as a transmission line) and transforms the helix impedance to a lower value over a substantial bandwidth     

HFC系统的业务量模型及分析

在HFC系统结构中，终端用户可以通过网络请求不同的业务服务，对于用户的网络接口单元（NIU），同轴电缆是其共用的传输介质。因此同轴电缆的业务传送能力，对于确定系统的规模，保证阻塞性能达到一个令人满意的水平，都是至关重要的。利用分析和仿真两种方法对同轴电缆的业务传送能力进行了研究。     

Green's function calculations on circular microstrip patch antennas

Green's function calculations have been applied to solve the radiation problem of circular microstrip patch antennas. The patch is fed by either a microstrip line or a coax line to be approximated as delta-function-like sources. The resultant Galerkin elements involve only one-fold Sommerfeld-type integrals. The resonant frequency, impedance, and far-field pattern have thus been calculated, which compared nicely with measurements     

Radiation of a coaxial line into a half-space

We present a new approach to the problem of radiation by a coaxial line into a half-space. We obtain boundary-integral equations for the current densities over the walls of the coax and its opening to the half-space. Using the modes of the coax for basis and testing functions, we convert the integral equations to an infinite system of linear equations, the unknowns being the coefficients of the current density expansions. We demonstrate how, by solving a small subsystem, we can obtain the fields everywhere in space.     

双向同轴光纤混合网介绍

双向同轴光纤混合 (HFC)网络是传统有线电视广播走向双向化的一种很好的实现方式。本文对其网络结构、工作频带划分、网络特点进行了介绍和分析。     

Waveguide or Coax for Five Megawatts

The maximum visual effective radiated power now permitted by the FCC for UHF TV is 5 000 000 watts. All manufacturers now have available 110-to 150-kilowatt transmitters with antennas having power gains of 35 to 60. Stations contemplating an increase to the maximum permitted power are faced with the difficult problem of selecting the type and size of transmission line to be used. The choice is between 6 ?-inch, 8 3/16-inch, or 9 3/16-inch coax line or WR-1500 or WR-1150 waveguide. This paper discusses some of the cost and technical tradeoff considerations that must be evaluated in selecting the proper type and size of transmission line.     

Open technical issues in provisioning high-speed interactive dataservices over residential access networks

This article is intended as an overview of high-speed data services delivery over residential access networks. The author identifies and lists some of the most important open technical issues that deserve further investigation by members of the global technical community prior to a truly large-scale deployment of a wide variety of high-speed interactive multiple-media services over state-of-the-art residential broadband access networks. The target access options include hybrid fiber/coax, fiber in the loop, digital subscriber line, digital satellite, broadband wireless, and so forth     

一种新型双频宽波束四臂螺旋天线的设计

根据移动卫星通信和卫星导航定位中对天线宽波束、圆极化和低仰角增益等要求,设计了一种新型的双频四臂螺旋天线,通过将工作于不同频段的两副结构类似的天线以内外共轴的方式形成一个整体来实现双频工作。天线通过开槽线巴伦实现平衡馈电,利用四臂螺旋自身的结构特点构造了90°自相移结构,获得了较好的宽波束圆极化特性。测试结果表明。实测和仿真结果基本一致,天线在两个频段都实现了较好的宽波束圆极化特性。     

一种新式背射天线

本文提出一种新式背射天线，它把单线背射螺旋作为短背射天线的馈源。这种天线具有结构简单，馈电方便，频带宽，增益中等，易于产生圆极化波等特点，较相同直径接地板的螺旋天线有更优的性能。     

A comparison of QAM and VSB for hybrid fiber/coax: digitaltransmission

There are two competing transmission systems for downstream digital transmission on hybrid fiber/coax cable networks: quadrature amplitude modulation (QAM), and vestigial sideband modulation (VSB). Both QAM and VSB are bandwidth efficient, and have the same bandwidth efficiency. Detailed calculations and simulations of QAM and VSB transmission on hybrid fiber/coax are reported here. It is shown that, since VSB has a higher symbol rate, it has at most 1/2 dB less received SNR than QAM at low frequencies because of dispersion and symbol timing jitter. This difference is negligible. Vendors proposing VSB recover the carrier with a pilot tone and a PLL, and vendors proposing QAM use all-digital data-directed carrier recovery. Simulations reported here show that QAM and VSB have very similar carrier recovery performance. It is concluded that for hybrid fiber/coax, VSB and QAM have practically the same overall performance, and the choice between these transmission systems should be based on considerations other than performance     

Laser clipping distortion in analog and digital channels

The exact carrier-to-nonlinear distortion (C/NLD) ratio, resulting from laser clipping, is computed for the low, center, and high channels of the analog and digital bands of a hybrid fiber/coax system. The computed results indicate that high capacity digital channels can be added to present analog systems without affecting the high performance analog channels     

HFC上行信道噪声及其抑制方法

分析了 Ｈ Ｆ Ｃ 网络上行信道噪声的来源和分类,针对不同的噪声提出几种有效的抑制方法,同时结合上行信道多址接入方式和调制解调方式的选择来抑制噪声。     

Slot Line Application to Miniature Ferrite Devices

This paper presents preliminary results and conclusions of experimental investigation of the potential usefulness of slot transmission line. Measurement of phase constant, insertion loss, and other general characteristics are presented and compared with theoretical predictions. Transitions from slot to coax and slot to microstrip are described.One of the more interesting characteristics of slot line, the existence of an elliptically polarized H field, is applied in planar ferrite phase shifter design. Experimental data are presented including preliminary latched phase shift results.     

An Efficient FDTD Model for Resistively Loaded Cylindrical Antennas With Coaxial Lines

A full coarse-grid based finite-difference time-domain (FDTD) model is proposed for an efficient analysis of resistively loaded cylindrical antennas driven by coaxial feed lines. In the case of the electrically thin resistive antenna, the thin-wire approximation is applied to the near fields around the antenna. The resistive antenna is equivalently represented by a series connection of piecewisely lumped resistors along the antenna axis. And the coaxial line is replaced by an equivalent source over the feed aperture of the line. Then the corresponding FDTD update equations make it possible to implement the full coarse-grid model without additional grid refinements for the antenna and the feed line. The transient reflected feed voltage and the input impedance of resistive antennas are calculated numerically and compared with those of a full fine-grid.