Active dual-beam aperture-coupled leaky-wave antenna

An active aperture-coupled leaky-wave antenna (LWA) with excellent dual-beam scanning capability is presented. An X-band varactor-tuned HEMT VCO is integrated on the other plane through an aperture with the LWA. This antenna has the advantages of multi-functionability, interference shielding, and a scanning main beam. The measured main beam in the elevation plane can be continuously scanned for 20° for each beam as the HEMT VCO frequency is varied from 8.97 to 9.5 GHz. An effective isotropic radiation power of 18.89 dBm for the right beam and 19.06 dBm for the left beam is achieved     

Active aperture-coupled leaky-wave antenna

An active aperture-coupled leaky-wave antenna which is integrated with a varactor-tuned high electron mobility transistor voltage-controlled oscillator (HEMT VCO) is presented. To excite the first higher mode of the microstrip, the aperture-coupled structure is used and a sequence of covered wire is added at the centre of this antenna to suppress the dominant mode. The measured H-plane main beam can be continuously scanned 10° as the HEMT VCO frequency is varied from 9.05 to 9.5 GHz. This feeding structure is very suitable for active phase antenna array applications     

A dual-beam asymmetrically scanning leaky-wave antenna by utilizinga HEMT resistive upconverter

A dual-beam asymmetrical scanning microstrip leaky-wave antenna (LWA) has been demonstrated in this paper. A HEMT resistive upconverter output is connected to one terminal of the LWA, and a local oscillator (LO) signal is connected to the other terminal. In this experiment, we set the LO frequency at 9.5 GHz so that the right beam is fixed at 48°. By changing the IF frequency from 0.7 GHz to 1.5 GHz, the module of the LWA can steer the left main beam of the far-field pattern from 136° to 158° (the total scanning angle of 22°). Comparisons between the measured and theoretical results indicate that the design can achieve the asymmetrically scanning capability and agree well over the tuning bandwidth of 0.8 GHz     

Dominant mode leaky-wave antenna with backfire-to-endfire scanning capability

A novel dominant mode leaky-wave antenna is proposed. This antenna is a transmission line structure with radiating wavenumber increasing from negative to positive values, providing backward to forward scanning capability as the frequency is increased. The characteristics and performances of the antenna are demonstrated by full-wave simulation and measurement results.     

Circularly-polarised microstrip leaky-wave antenna

A novel circularly polarised microstrip leaky-wave antenna is proposed and tested. Two linear polarised orthogonal dual-terminals feeding microstrip leaky-wave antennas are fed with equal amplitude and 90deg phase difference to generate the two orthogonal modes. The measured results show that the antenna achieves circular polarisation efficiently.     

Active dual-beam leaky-wave antenna with asymmetrically scanningcapability

An active microstrip leaky-wave antenna possessing asymmetrically dual-beam scanning capability is demonstrated. An active HEMT up-converter is integrated at the right terminal of the two-terminal feeding microstrip leaky-wave antenna. This approach creates dual-beam asymmetrically scanning radiation patterns. When the right beam is fixed in one position, the other beam can be scanned electronically by varying the IF frequency. The measured results show that when the position of the right beam was fixed (48°), a scanning angle of 22° for the left beam could be achieved as the IF input frequency was varied from 0.7 to 2 GHz (UHF band)     

Planar double-layer leaky-wave microstrip antenna

This paper presents a double-layer leaky-wave microstrip antenna that is entirely planar for easy fabrication. The cavity model and the full-wave spectral domain method are used to analyze the proposed structure. The results from these two approaches agree well with experimental data. The planar structure makes the leaky-wave antenna convenient for implementation in a monolithic microwave integrated circuit (MMIC) environment. Also, due to the flexibility of the microstrip structure, the geometrical shape can be modified for other desirable radiation patterns     

Two-dimensional scanning leaky-wave antenna by utilizing the phased array

An aperture-fed patch antenna array is connected to the open end of a short leaky-wave antenna (LWA) to demonstrate the two-dimensional beam-scanning capability in this paper. This design not only offers another radiation path of the reflected wave, but also creates another scanning radiation pattern on the back plane of the substrate. The reflected wave of the LWA is equally separated by a power divider, modulated by each varactor-tuned phase shifter, and injected into two radiating aperture-coupled antennas. The operated frequencies are tuned to control the LWA main position in the elevation plane; meanwhile, by tuning the phase difference between two phase shifters, the main beam of the aperture-coupled antenna array can be scanned in the backside E plane. Experimental result shows that the suppression of the reflected wave can be 7 dB at 10.0 GHz with a short LWA length of 6 cm (two wavelengths). The H-plane and backside E-plane scanning radiation patterns have great potential in many applications and provide more flexibility to traditional designs.     

Broadband tapered microstrip leaky-wave antenna

This study proposes a novel scheme based on the characteristics of leaky-wave antennas for the empirical design of broadband tapered microstrip leaky-wave antennas. This scheme can explain and approximately model the radiation characteristics of a linearly tapered leaky-wave microstrip antenna. A broadband feeding structure that uses the balanced and the inverted balanced microstrip lines to form a pair of broadband baluns is also presented. The measured return loss of the inverted balanced microstrip lines has a VSWR/spl les/2 from dc to 18.6 GHz and that of the back-to-back feeding structures has a VSWR/spl les/2 from 2.2 to 18.6 GHz. This feeding structure can be used to feed a broadband planar leaky-wave antenna with a fixed mainbeam that uses the tapered microstrip structure. The measured bandwidth of the antenna for a VSWR/spl les/2 exceeds 2.3:1.     

Two-dimensional beam-scanning microstrip leaky-wave antenna

A novel two-dimensional beam-scanning microstrip leaky-wave antenna (MLWA) is presented. The proposed antenna consists of two half-width MLWA with a phase-shifter. This new type of MLWA has the advantages of two-dimensional beam-scanning and suppressing back lobes. This reduced size MLWA is useful in automotive radar systems and air traffic control.     

一种天线馈源用宽带孔径耦合层叠微带贴片阵的设计

介绍了一种宽带孔径耦合层叠微带辐射单元的工作原理,着重分析了该辐射单元主要结构尺寸对其阻抗带宽的影响。该辐射单元阻抗带宽（VSWR≤2：1）在S波段达到了30％以上。作为某抛物反射面天线的馈源,由4个该辐射单元组成四单元微带贴片天线阵后,其性能满足天线系统要求。     

无表面波损耗的孔耦合贴片天线的设计

设计了一种新结构的孔耦合贴片天线。该天线结构将贴片连用制作贴片的介质基板一起放置在一个矩形金属框里，彻底阻断了表面波的传输，该天线结构的尺寸比一般贴片天线要小很多。但却具有更高的增益，还介绍了对该天线结构的数值模拟。样品制作和实验测量，测量数据显示矩形金属框使天线的增益在9GHz到11GHz的频率范围内平均提高了0.7dB，该天线的工作频带超过了20%，带内平均增益为8.3dBi，同时天线具有良好的辐射方向图。     

Beam-switchable scanning leaky-wave antenna

A beam-switchable scanning leaky-wave antenna (LWA) has been developed. This LWA with a two-terminal feeding microstrip line structure is integrated with a single port double throw (SPDT) switch as a control circuit. In dual-beam mode, the scanning angle is steered over a range of 36-64° for the right-hand beam and 144-116° for the left-hand beam. In one-beam mode, the scanning angle is measured over 20° for the right-hand beam. The measured result shows that we can change from the one-beam mode to the dual-beam mode electronically by controlling the on/off status of an SPDT switch, in contrast to the case for traditional leaky-wave antennas     

Miniature aperture-coupled microstrip antenna of very highpermittivity

A miniature aperture-coupled microstrip antenna of very high permittivity designed at 1.66 GHz is described. Superstrates of appropriate thickness are added on the substrate for gain enhancement. Its size is dramatically reduced and the electrical performance remains almost the same as compared with the conventional microstrip antenna of low dielectric constant. Experimental data for the return loss, radiation pattern and measured antenna gain are presented to validate the design     

Transmission line analysis of aperture-coupled microstrip antenna

The authors present an original analysis of a slot-coupled microstrip antenna. The transmission line model uses previous expressions of conductance and susceptance due to the fringing fields near the edges of the patch; moreover, a simple interpretation of the different impedance transformations is given. Results based on the transmission line model are compared with other theoretical analyses (cavity model, moment method) and measurements.<>     

A 94-GHz aperture-coupled micromachined microstrip antenna

This paper presents an aperture-coupled micromachined microstrip antenna operating at 94 GHz. The design consists of two stacked silicon substrates: (1) the top substrate, which carries the microstrip antenna, is micromachined to improve the radiation performance of the antenna and (2) the bottom substrate, which carries the microstrip feed line and the coupling slot. The measured return loss is -18 dB at 94 GHz for a 10-dB bandwidth of 10%. A maximum efficiency of 58±5% has been measured and the radiation patterns show a measured front-to-back ratio of -10 dB at 94 GHz. The measured mutual coupling is below -20 dB in both E- and H-plane directions due to the integration of small 50-μm silicon beams between the antennas. The micromachined microstrip antenna is an efficient solution to the vertical integration of antenna arrays at millimeter-wave frequencies     

Frequency-fixed beam-scanning microstrip leaky-wave antenna with multi-terminals

New frequency-fixed beam-scanning microstrip leaky-wave antennas are reported. The beam-scanning ability at a fixed frequency of the antenna can be achieved with novel feeding configurations. Simulation and measurement results show the new feeding structure can make the main lobe gradually scan from 50 to 80/spl deg/ in H-plane when the frequency fixes at 1.12 GHz     

Dual-beam array of microstrip leaky-wave antennas

The authors present a small series-fed array of microstrip leaky wave antennas (LWAs) operating at 6.85 GHz and showing a narrow dual-beam pattern (17°×22°). The excitation is provided by a slotted coplanar waveguide. This type of antenna could be used as a radar sensor in Janus systems for contactless measurements of velocity and distance     

Analysis of aperture-coupled microstrip antenna using cavity method

Presents an original analysis of aperture coupling of a microstrip antenna. The theory is based on the cavity model, and results are compared with the moment method and measurement.<>     

Analysis of aperture-coupled microstrip antenna using thesegmentation method

The authors present an original analysis of an aperture-coupled microstrip antenna. The theory is based on the segmentation method, which considers the patch as a multiport network whose impedance matrix is deduced from a hybrid matrix, and the use of analytical expressions of the cavity admittance at the slot centre. The theory is presented for the first time, and the theoretical results are in good agreement with previous published measurements