Radiation and scattering characteristics of microstrip antennas onnormally biased ferrite substrates

Radiation and scattering characteristics of microstrip antennas and arrays printed on ferrite substrates with a normal magnetic bias field are described. The extra degree of freedom offered by the biased ferrite can be used to obtain a number of novel characteristics, including switchable and tunable circularly polarized radiation from a microstrip antenna having a single feed point, dynamic wide-angle impedance matching for phased arrays of microstrip antennas, and a switchable radar cross section reduction technique for microstrip antennas. Results are obtained from full-wave moment method solutions for single microstrip antennas and infinite arrays of microstrip antennas. A cavity model solution for a circular patch antenna on a biased ferrite substrate is also presented, to aid in understanding the operation of these antennas     

A study of the isolation of two different feed networks for antennaarrays

The isolation of two different feed networks for antennas is presented. This is quantitatived by the reappearing voltage at the antenna elements due to the reflection at the network junctions. The voltage is formulated for the general case of antenna arrays. From the comparison of the isolation between the corporate and the modified corporate feed network a better isolation to the modified one is found     

Performance of a meandered line as an electrically smalltransmitting antenna

For antennas to radiate at maximum efficiency, their dimensions must be on the same order as the radiated wavelength. At frequencies below 30 MHz, antennas with efficient radiation are often too large for mobile and portable applications. Smaller antennas can be made to radiate efficiently by use of matching networks. For installation convenience and ease of adjustment, these networks are usually placed between the transmitter and the antenna input; but it has been found that for best radiation efficiency, matching network elements should be placed at points on the antenna structure. Unfortunately, such matching networks must be tuned for each transmitting frequency and, when mounted on the antenna, they cannot easily be tuned. A meander element antenna was found to present some electrical and mechanical properties allowing convenient placement of tuning elements when configured as an electrically small transmitting antenna. Some simplified design guidelines were derived from experimental data     

一种5G手机的紧凑型16单元多频MIMO天线

提出一种应用于5G智能手机中结构紧凑的16单元多频段多输入多输出(MIMO)天线阵列。该多天线系统由8个紧凑天线阵列对组成,为了预留2G/3G/4G天线的布局空间,这8个天线阵列印刷在智能手机的两侧边上。每个天线阵列对由2个紧凑的间隙耦合环路天线组成,分别布置在系统板的上、下两侧;其中上侧天线工作在LTE band 46(5 150~5 925 MHz),下侧天线覆盖LTE band 42/43(3 400~3 800 MHz)。测试结果表明该天线阵列具有良好的阻抗匹配和隔离性能。同时还对MIMO一些包络相关系数进行了研究分析。最后研究了人手和头对整个天线性能的影响,仿真结果表明,在日常各种使用情况下,该天线阵列也具有良好的辐射特性。     

Antenna research at the Communications Research Centre

An overview is presented of the antenna research carried out by the Directorate of Antennas and Integrated Electronics (DAIE) of the Communications Research Centre (CRC). The antenna research within the DAIE can be categorized into two groups: antenna-hardware development and electromagnetic-software development. Research in antenna hardware has focused on printed multi-layer arrays, dielectric-resonator antennas, ferrite antennas, active-circuit integration, and low-loss feed networks. Research in electromagnetic software includes the development of three-dimensional transmission-line-matrix (TLM) code, and the application of cellular automata (CA) techniques for the analysis and modeling of antennas, microwave circuits, and general electromagnetic phenomena, such as scattering. This article concentrates on the antenna-hardware research and development within the DAIE. Radiation patterns are considered     

Compact and contact quad-band (DVB-H UHF/L, WLAN 11a/b) antenna for PMP applications

The quad-band antenna, which is composed of two compact dual-band antennas, is presented for potable media player (PMP) applications. The antenna for the broadcasting dual-band (DVB-H UHF; 470 - 862 - MHz, L; 1452 - 1492 - MHz) is composed of a planar inverted F-shaped antenna with an input matching circuit. The antenna for the communication dual-band (WLAN 11b; 2.4 - 2.5 - GHz, 11a; 5.15 - 5.8 - GHz) is composed of a folded dipole antenna with enhanced mutual coupling. The proposed antennas are contact with the PMP case (?_r = 3.2) which is used as a substrate for size reduction and compact design.     

Thin-film HTS planar antennas

The “H” microstrip antenna is suitable for use as an efficient small antenna when it is constructed out of superconducting thin-film materials. An aperture feed and matching network is described which provides a convenient enhancement of the capabilities of the “H” antenna. Methods of prediction of the center frequency are given. In addition, an analytical expression is developed for the far field radiation pattern of the “H” antenna and the efficiency and Q of superconducting and copper antennas are described using this expression. It is likely that superconducting antennas will only have significant application when they are used in arrays. Three arrays are described demonstrating multiband self-diplexing multifrequency-enhanced bandwidth and multifrequency beam forming     

A wide-band circularly polarized antenna

The design construction and testing of a wide-band circularly polarized antenna suitable for ionospheric research is described. The antenna operates in the range 2 to 7 MHz. Simple design formulas are given for the required broad-band phase shifting networks. Broad-band dipole antennas are used and suitable "balancing networks" are developed to match these antennas to the phase shifting networks ever the frequency range. A satisfactory compromise solution is found to the problem of matching the networks to the receiver using a broad-band transformer. Measurements of the rejection ratio of the system show that it is always better than approximately 16:1 over the required frequency range.     

Back-to-back measurement for characterization of phased-arrayantennas

A back-to-back measurement method for characterizing phased-array antennas is described. The method yields the complex active impedance of an antenna in a large phased array at any desired frequency and scan angle without the need of a feed network to excite the antenna under test. This avoids the cost and de-embedding procedure associated with the feed network. Measurements are performed by using two different transmission networks to connect identical arrays in a back-to-back configuration. The new method is particularly well suited to printed antennas and is illustrated by using tapered-slot antennas. Back-to-back measurements in waveguide simulators compare well to traditional waveguide simulator measurements and measurements in an anechoic chamber compare well to results from computer codes based on the full-wave method of moments     

Characterization of tapered slot antenna feeds and feed arrays

A class of feed antennas and feed antenna arrays used in the focal plane of paraboloid reflectors and exhibiting higher than normal levels of cross-polarized radiation in the diagonal planes is addressed. A model which allows prediction of element gain and aperture efficiency of the feed/reflector system is presented. The predictions are in good agreement with experimental results. Tapered slot antenna (TSA) elements are used as an example of an element of this type. It is shown that TSA arrays used in multibeam systems with small beam spacings are competitive in terms of aperture efficiency with other, more standard types of arrays incorporating waveguide type elements     

Optimization of PIFA-IFA combination in handset antenna designs

As commercial needs have expanded the functions of the wireless cellular handsets, multiantenna development in one handset has become more and more common. This paper addresses a multiantenna solution for the wireless handset application. A planar inverted "F" antenna (PIFA) was designed as the main antenna of the handset to cover the 800 MHz band (824 MHz-894 MHz) and the 1900 MHz band (1850 MHz-1990 MHz). A side-mounted inverted "F" antenna (IFA) was designed as the 1575.42 MHz global positioning system (GPS) antenna. The location of the feed/ground pins of both antennas affected not only the total antenna efficiency, but also the polarization of the GPS IFA. The length of the GPS IFA affected the isolation between the two antennas and the specific absorption rate (SAR) of the PIFA at the 1900 MHz band. A three-dimensional efficiency measurement of the prototypes in both free space and against-head position will be presented. Measurement of SAR and its distribution will also be presented to demonstrate the impact of the IFA on the near field of the PIFA.     

Superconducting microstrip antennas: an experimental comparison oftwo feeding methods

The recent discovery of high-temperature superconductors (HTSs) has generated a substantial amount of interest in microstrip antenna applications. However, the high permittivity of substrates compatible with HTS causes difficulty in feeding such antennas because of the high patch edge impedance. Two methods for feeding HTS microstrip antennas at K- and Ka-band are examined. Superconducting microstrip antennas that are directly coupled and gas-coupled to a microstrip transmission line have been designed and fabricated on lanthanum aluminate substrates using Y-Ba-Cu-O superconducting thin films. Measurements from these antennas, including input impedance, bandwidth, efficiency, and patterns, are presented and compared with published models. The measured results demonstrate that usable antennas can be constructed using either of these architectures, although the antennas suffer from narrow bandwidths. In each case, the HTS antenna shows a substantial improvement over an identical antenna made with normal metals     

A study of microstrip array antennas with the feed network

The radiation and losses in microstrip antennas with a corporate feed network are studied. A surface current approach is applied in which the electrical currents in the feed lines are modeled as in ideal transmission lines. The free-space radiation and the surface-wave excitation of typical segments in printed feed networks are studied. A four-element array antenna with its printed feed network is analyzed and predicted radiation patterns, directivity, and gain are presented and compared with experimental results. The gain and directivity of large arrays of 16, 64, 256 and 1024 elements are calculated and measurements in the frequency range of 10 to 35 GHz are reported     

Advances in multibeam communications satellite antennas

The evolution of satellite antennas over the past quarter of a century is presented. Five major areas of advances in communications satellite antenna technology are reviewed: single offset reflectors with feed arrays, shaped reflector systems, active phased arrays, phased-array-fed dual reflector systems, and lightweight feed elements. Examples are given of existing systems and of the ongoing development of new technologies     

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.      

Design of RFID tag antennas using an inductively coupled feed

An inductively coupled feed method is explored to design UHF radio frequency identification tag antennas. An analytical model for the proposed feed structure is derived and used to perform simple and wideband impedance match between an antenna and a tag chip without any additional matching networks. The proposed design methodology is verified by comparing the calculations and measurements, which show good agreement.     

Electrically small self-resonant wire antennas optimized using agenetic algorithm

One of the major limitations of electrically small antennas is that as the size of the antenna is decreased its radiation resistance approaches zero and its reactance approaches plus or minus infinity. Most small antennas are inefficient, nonresonant and, thus, require matching networks. In this investigation, we use a genetic algorithm (GA) in conjunction with the numerical electromagnetics code to search for resonant wire shapes that best utilize the volume within which the antenna is confined. Antenna configurations, over a ground plane, having from two to ten wire segments, were optimized near 400 MHz and then built and tested. As the cube size deceased from a side length of 0.096λ to 0.026λ, the computed Qs increased from 15.8 to 590. The measured Qs increased from 16.0 to 134 for cubes of 0.093 to 0.037λ on edge. This process for designing small antennas using a GA produced new self-resonant antenna configurations     

Lens-coupled imaging arrays for the millimeter- andsubmillimeter-wave regions

The authors have been developing four kinds of lens-coupled antenna imaging arrays for operation at millimeter- and submillimeter-wave frequencies. Dipole antennas, Yagi-Uda trap-loaded antennas, and microstrip patches are compared from the viewpoint of matching with detectors and optical systems. The radiation patterns and input impedance of each antenna have been calculated and measured to attain the optimum matching using model experiments. The trap-loaded antenna arrays have been successfully applied to plasma diagnostics at the Tsukuba GAMMA 10 tandem mirror     

Analysis of infinite arrays of substrate-supported metal stripantennas

An electric field integral equation method is applied to a metal strip antenna on an electrically thick dielectric substrate of finite size in a uniform infinite array environment. An efficient solution is found using the method of moments. Metal strip folded dipole antennas are analyzed both with and without a coplanar strip feed line, and the effects of the substrate and feed line are investigated. A technique for minimizing the effect of feed line scattering is presented, and arrays of these elements are shown to be capable of good scanning performance over a wide range of beam-steer angles. A phased array simulator experiment is described and the measured results show good agreement with those obtained by analysis. The class of antenna elements studied may be fabricated using monolithic microwave integrated circuit (MMIC) technology, and the analysis described illustrates the expected characteristics for millimeter-wavelength phased arrays of this type     

Gain and G/T of multielement receive antennas with activebeamforming networks

A basic system-level model for the gain and G/T of active multielement receive antennas is presented that covers arbitrary beamforming networks and direct radiating arrays, as well as array-fed systems with one or more focusing elements (reflectors or lenses). Since the model is based on measurable parameters and uses definitions, which are consistent with conventional communication system analysis terms, it can be applied directly to the analysis and design of systems using such antennas and can be used to support the specification, design, and test of such antennas as well, measurement possibilities for the basic parameters are discussed and the characteristic parameters of generic active beamforming networks are derived and compared. Finally, the impact of the different parameters on the overall antenna gain and G/T is illustrated by one application example that covers a reconfigurable multifeed reflector antenna with selectable beamwidth. The presented theory has been verified successfully in the frame of a classified EHF antenna development whose details cannot be reported here