Liquid-crystal-based reflectarray antenna with electronically switchable monopulse patterns

A printed reflectarray antenna, which generates a beam that can be electronically switched from a sum to a difference radiation pattern, is presented. This is achieved by applying a bias voltage of 20 V to one- half of the aperture, which is constructed above a 500 mum cavity containing liquid crystals. Simulated results are shown to be in good agreement with measurements at X-band.     

An electronically scanned beacon antenna

An electronically scanned cylindrical array having a minimum number of active devices has been designed. A saving of over 3 to 1 in diode elements as compared to conventional approaches has been achieved. In addition to providing instantaneous positioning to any azimuth direction, a constant azimuth beamwidth for an elevation fan beam has been realized. Extremely low azimuth sidelobes are obtained, and a straightforward synthesis procedure can provide elevation aperture designs to meet typical elevation pattern requirements. A modified Myer geodesic lens combined with a diode sequencing switch for coarse steering and a phased matrix feed for fine steering form the basis of the system. Sum and difference patterns show virtually no variation with scan or elevation angle and an omni-pattern is also available. Detailed pattern calculations as well as measured data on prototypes of key elements of the system are presented to verify the feasibility of the approach.     

基于FDTD的微带缝隙漏波天线分析

应用时域有限差分法(FDTD)对微带缝隙漏波天线进行分析,直观地得到了微带缝隙漏波天线内部的电场分布。提出了一条有效的经验公式,成功地计算了微带缝隙漏波天线的漏波传播系数,与实验数据吻合较好。比较了不同缝隙宽度和微带宽度对微带缝隙漏波天线性能的影响。证明了在微带漏波天线上开缝可以有效地减少天线尺寸及降低天线的工作频率。     

Aperture-coupled microstrip line leaky wave antenna with broadsidemainbeam

A microstrip first higher order leaky wave antenna (LWA), centre-fed by an aperture-coupled microstrip with a broadside mainbeam, is presented. The measured bandwidth (23% for VSWR<2:1) is in agreement with the leaky radiation band predicted. The experimental gain patterns, compared with those of a patch antenna fed by the same type of structure, reveal the difference between these two kinds of antenna. With increasing frequency, the radiation field of the LWA spreads into the H-plane, forming a flatter broadside pattern, which can be applied to long rectangular area communication     

IMPROVED PERTURBATION ANALYSIS OF MILLIMETER-WAVE DIELEC TRIC GRATING LEAKY WAVE ANTENNA

An improved perturbation procedure is used for analyzing the radiation character-istics of the millimeter wave dielectric grating leaky wave antenna. The electromagnetic fields aredescribed in terms of an active transverse transmission line network, which brings considerablephysical insight into the overall behavior of the antenna. The analysis is simple and practical. Itsaccuracy is as high as the rigorous method.     

Transverse resonance solutions for a long slot leaky wave antenna

Exact solutions of the transverse resonance equation for a long slot leaky wave antenna have been obtained by numerical analysis and verified by practical results.     

Ku band pattern reconfigurable substrate integrated waveguide leaky wave horn antenna

A dual band substrate integrated waveguide H plane sectoral horn antenna with reconfigurable radiation characteristics has been proposed in this paper. Designed antenna acts as a perfect broadside radiator at 16.1 GHz and perfect endfire radiator at 14.4 GHz frequency. Broadside radiation has been achieved by etching rectangular slots in the flared section of horn exhibiting a gain of 8.87 dBi. To achieve perfect endfire radiation, dielectric loading is done at the edge of horn and at this frequency antenna shows a gain of 11.3 dBi. The horn and the loaded dielectric are integrated by using the same single substrate resulting in easy fabrication and low cost. The proposed design has been fabricated and measured results are in good agreement with the simulated results.     

An HF array antenna electronically scanned in elevation

An HF receiving array antenna, consisting of ten 12 to 25 MHz horizontally-polarized log-periodic-dipole element antennas, spaced vertically 16 meters apart on the side of a 152-meter (500-foot) tower, has been erected near Boulder, Colo. It is capable of electronically scanning a sector in elevation ranging from3.5degto51degat 12 MHz, to1.7degto22degat 25 MHz. The sector was scanned with a single major lobe which had a vertical plane half-power beamwidth that varied from7degat 12 MHz to3degat 25 MHz. This array was a part of a system designed for studying the angle-of-arrival of downcoming radio waves from the ionosphere. A sinusoidal current distribution formed a single major lobe which was scanned in elevation by varying the period of the sinusoid. Scanning was accomplished electronically at an intermediate frequency; therefore, the increase in bandwidth of the received signal, caused by the rapid scanning, took place after conversion and did not necessitate an increase in bandwidth of the RF input circuitry. The scanning rate was 524 Hz with the sector scanned by an upgoing lobe and a downgoing lobe in each scanning cycle. Photographs of the oscilloscope display are presented which show the vertical angle-of-arrival of 10 and 20 MHz signals from WWV. Comparison of sinusoidal distribution with conventional shows that the sinusoidal distribution results in half the beamwidth of the latter, 3 dB higher gain, and a lower minimum angle above horizon.     

基于FDTD的微带漏波天线分析的新方法

使用时域有限差分法对微带漏波天线进行数值仿真,得到了微带漏波天线TE01模下的电场分布,对微带漏波天线的电波传播特性进行初步的讨论.提出新的经验计算公式微带漏波天线漏波传播系数,所得漏波传播系数曲线与实测数据以及比较数据十分吻合.     

基于CRLH传输线的微带漏波天线的研究与设计

提出了一种基于谐振频率的等效电路参数提取方法,该方法可以精确地描述多节复合左右手传输线结构,并通过仿真软件研究了其物理模型及等效电路模型的一致性,从而验证了这种新的参数提取方法。根据此种新的等效模型设计制作了复合左右手传输线型微带漏波天线,并利用网络分析仪对它的S参数进行了测量。结果表明,所设计的平衡状态下的微带漏波天线波束方向随着频率的变化而变化,并且改变传统漏波天线仅能实现前半空间扫描的局限性,并拓展漏波天线扫描范围至全空间,同时在各个波束方向上的能量也较为均匀,相比于传统漏波天线,尺寸缩小接近50%。     

A reconfigurable slot antenna with switchable polarization

A novel reconfigurable slot antenna architecture allowing polarization switching is presented. The antenna shape consists of a slot-ring with perturbations which are switched on and off using pin-diodes. Two antennas allowing switching either between linear and circular polarization or between two circular polarizations are demonstrated. The antenna architecture is interesting for commercial wireless applications because it is compatible with modern fabrication processes and can be realized on low cost dielectric materials.     

A reconfigurable microstrip antenna for switchable polarization

A novel reconfigurable microstrip antenna with switchable polarization sense is proposed. The proposed antenna has a simple structure, consisting of a corner-truncated square radiating patch, four small triangular conductors, and a microstrip line feed. Using independently biased PIN diodes on the patch, it can produce linear polarization, or left- or right-hand circular polarization according to bias voltages. From the measured results, low cross-polarization levels when operated in the linear state and good axial ratios in the circular state are observed.     

Dual-frequency electronically tunable CPW-fed CPS dipole antenna

A CPW-fed coplanar strip (CPS) dipole antenna is presented which operates at dual frequencies. A wideband CPW-to-CPS balun was designed and used. Dual-frequency operation of the CPS dipole antenna was realised by introducing a small gap in the length of the dipole. Varactors were integrated with CPS dipoles to form integrated antennas. The CPS dipole antenna was electronically tuned by varying the varactor bias voltages. Measurements showed good results of dual operating frequencies, frequency range, and antenna pattern     

Circularly polarised antenna with switchable polarisation sense

The authors present the design of a wideband circularly polarised antenna with switchable polarisation sense. The basic antenna is a circularly polarised aperture coupled patch antenna with a slot excitation located along the diagonal of a rectangular patch. A second slot is added along the other diagonal and beam-lead pin diodes are inserted in both slots to allow a dual sense operation for a compact structure in a 4% CP bandwidth     

Broadband circularly-polarised microstrip antenna with switchable polarisation sense

A circularly-polarised microstrip antenna capable of switching polarisation sense is presented. The proposed microstrip antenna has a circular radiating patch and is excited by an open-loop microstrip line through the coupling of a ring slot in the ground plane. Two ends of the open-loop microstrip line can be taken for the input ports to excite right-hand and left-hand circular polarisations, respectively. A prototype using PIN diodes to electrically switch the input ports is implemented, and the measured results show the 3 dB axial ratio bandwidth of more than 10% can be obtained at the two polarisation senses     

Crossed dipole antenna with switchable circular polarisation sense

A crossed dipole antenna with a reconfigurable circular polarisation (CP) is proposed. This antenna consists of a pair of L-shape elements with λ_g/4 phase delay lines and DC bias circuits for pin diodes. As the state of the pin diodes mounted between the feeding points and the L-shape elements is changed, the phase sequence of the crossed dipole can be varied. The CP sense of the proposed antenna can be switched with excellent electrical controllability.     

Aperture-coupled antenna with switchable polarisation and frequency agility

The design of an aperture-coupled microstrip antenna with switchable polarisation and frequency agility is studied. Switching between two orthogonal linear polarisations (LPs) is realised by mounting two switching pin diodes on the antenna. To achieve multi-operating frequency (frequency agility) on one of the LPs, a voltage-controlled varactor diode is loaded between the top-loaded square patch and the ground plane. From the measured results, a good cross-polarisation level is observed when operated in both linear states at around 2 GHz.     

Multipassband electronically tunable magnetostatic wave filter

A new design for a multipassband microwave filter based on magnetostatic waves propagating in a multilayer planar ferrite structure is described. The experimentally realised filter had two passbands of 10 MHz bandwidth and 5-6 dB insertion loss separated by 400 MHz, and was tuned with an external magnetic field over the 2.5-4 GHz range.<>     

Polarisation switchable microstrip array antenna using proximity feeding technique

A polarisation switchable microstrip array antenna is presented. This array consists of square patch antennas coupled in close proximity to a microstrip line. The polarisation state can be switched electrically by short- or open-circuiting the end of the feedline using a PIN diode. Fundamental characteristics of the proposed array are investigated by measurements performed at S-band to demonstrate the proposal.     

The leaky lens: a broad-band fixed-beam leaky-wave antenna

A novel type of leaky-wave antenna is presented. Differently from previously reported leaky-wave antennas, it is characterized by a constant beam direction over a very wide range of frequencies. The radiation originates at a slot etched at the interface between air and a dense dielectric, which is shaped to form a cylinder of elliptical cross sections of decreasing dimensions. Two prototypes have been designed, manufactured, and tested. The measurements are in very good agreement with the expectations, demonstrating the potentials of the leaky lens concept to realize integrated transmitters or receivers that are extremely broadband and directive.