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     

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     

An asymmetric feeding X-band active frequency-scanning leaky-wave antenna

An asymmetric feeding X-band active leaky-wave antennas is developed, to excite the first high order mode of the microstrip leaky wave antenna. One is the asymmetric feeding leaky-wave antenna which integrated with a HEMT oscillator, and the other is the frequency-tuned leaky-wave antenna which integrated with a varactortuned HEMT VCO. The microstrip leaky-wave antenna is operated in the first higher mode. To excite the first higher mode, the microstrip leaky-wave antenna is fed asymmetrically. The dominant mode excitation has been successfully suppressed by adding a sequence of covered wire in the center of the microstrip leaky wave antenna. The design of these active leaky-wave antennas is discussed and the beam scanning phenomena of the antenna is presented. The HEMT oscillator frequency is controlled by tuning the varactor DC bias and the beam scanning is demonstrated. The measured scanning angle agree with prediction, it is close to 30° as the VCO frequency tuned from 8.06 GHz to 9GHz.     

A new two-terminal feeding active leaky-wave antenna

A new two-terminal feeding active-integrated leaky-wave antenna design is demonstrated. The X-band microstrip two-terminal feeding leaky-wave antenna is integrated with an active high-electron mobility transistor (HEMT) oscillator to produce a two-beam radiation pattern. The antenna is fed asymmetrically at both sides to excite the first higher order mode. This configuration, as compared to a single-terminal feeding leaky-wave antenna, has the advantage of the multidirection and the reduction of the reflected wave caused by the open end of the radiating element. Measured results show that the radiation directions of two beams are approximately at 34° and 140°, the effectively isotropic radiated power (EIRP) is close to 17.5 dBm, and the return loss is almost less than -10 dB between 9 and 11.5 GHz     

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     

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)     

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 Gunn-Diode Active Leaky-Wave Frequency Scanning Antenna

A frequency tunable active leaky-wave scanning antenna using Gunn-diode voltage control oscillator (VCO) as source is developed. The frequency tuning controlled by changing either the varactor diode dc bias or the Gunn diode dc bias is demonstrated. The measured scanning angle of active antenna is close to 15 degree as the Gunn VCO frequency tuned from 12.58GHz to 12.98GHz. To excite the first higher order mode of the microstrip leaky-wave antenna is fed asymmetrically. The dominant mode excitation has been successfully suppressed by adding a sequence of covered wire in the middle line of the microstrip leaky wave antenna. This is a prototype of frequency scanning antenna using two terminal device, which can be easily scaled up to millimeter wave frequency region.     

Active Frequency-Tune Beam-Scanning Leaky-Wave Antenna Arrays

X-band active beam-scanning leaky-wave antenna arrays, including 1 × 1,1 × 2 and 1 × 4 prototypes, have been demonstrated. These antennas integrated one or several microstrip leaky-wave antenna elements with a single varactor-tuned HEMT VCO as an active source. Measured results on experimental antennas indicate that the beam scanning angle of the 1 × 1 antenna close to 40° can be achieved and the scanning range of 1 × 2 and 1 × 4 antenna arrays are both close to 32°. Furthermore, reflected wave due to the open end of each leaky-wave antenna element has been suppressed by the symmetric configuration of this antenna array and the antenna efficiency increases. When comparing with the measured radiation pattern of the single element antenna, we found that the 1 × 2 and 1 × 4 antenna arrays can effectively suppress the reflected power by more than 5.5 dB and 10.5 dB, respectively, at 10.2GHz. The power gain are more than 2 dB and 3.16 dB higher than the single element antenna with a measured EIRP of 18.67 dBm.     

An aperture-coupled linear microstrip leaky-wave antenna array withtwo-dimensional dual-beam scanning capability

This paper describes an X-band 4×1 aperture-coupled series-fed electronically steerable microstrip leaky-wave antenna (LWA) array design, which has dual-beam radiation pattern and two-dimensional (2-D) beam-scanning capability. The LWA array is operated in the first higher order mode and excited by center-fed aperture coupled for dual-beam operation. The varactor-tuned phase shifters are placed between the antenna elements. The measured half-power beamwidth of the H-plane and quasi-E-plane radiation patterns are less than 30°. By tuning the reverse dc bias of the varactor diodes, the main beam can be scanned in azimuth plane from -13° to +13° off broadside. In the elevation plane, the beam-scanning angle is close to 20° as the operating frequency tuned from 11.58-12.5 GHz. Taking into account each phase-shifter insertion loss and phase progression, the measured results compared closely with the theoretical prediction. The proposed antenna array is suitable for wireless communication and collision warning radar systems     

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.     

Active feedback microstrip leaky wave antenna-synthesiser designwith suppressed back lobe radiation

The design of an active leaky-wave antenna which integrates the antenna with a feedback synthesizer is introduced. The measurement result shows that the antenna has very low back lobe radiation compared with that of traditional single-terminal feeding leaky-wave antennas. Single frequency measurement shows that the radiated power difference between the main beam and back lobe is >15 dB at 8.2 GHz. For the designed feedback synthesizer antenna, the measured radiated power difference between the main beam and back lobe is >15 dB at 9.25 GHz, and the scanning angle is ~5° as the synthesizer frequency sweeps from 9.25 to 9.37 GHz     

Microstrip Leaky-Wave Antenna With Control of Leakage Rate and Only One Main Beam in the Azimuthal Plane

An original leaky-wave antenna (LWA), conceived from a microstrip line which is laterally shielded by parallel plates, is presented in this paper. This structure shows, for the first time, that the leakage rate of a microstrip leaky-mode can be easily controlled while negligibly affecting the pointing direction. The antenna is based on the radiation from the second higher order mode of the microstrip line, which is perturbed by the addition of the two conductor walls to control the level of the leakage rate. The parallel-plates also serve as a mechanism to obtain a single main beam in the azimuthal plane, therefore improving the radiation pattern compared to common dual-beam second-higher order mode microstrip LWAs. The proposed antenna is analyzed by obtaining the corresponding leaky-mode complex propagation constant, which is calculated by a specific method of moments approach. The modal results obtained from the leaky-mode dispersion curves are validated with analysis performed on a three-dimensional structure using commercial finite element method solver. Also, a prototype is fabricated to experimentally confirm the advantages of this novel leaky-wave line source.     

Phase-shifterless beam-steering micro-slotline antenna

A novel beam-steering leaky-wave antenna that uses reactive loading capacitors along the leaky line is presented. The reactive loading varies the phase constant of the leaky line, altering the direction of the main beam. A prototype was constructed and tested, demonstrating that a beam scanning angle of 23° is obtained by periodically loading the 0.06527 pF capacitors along the leaky line at 4 GHz. An electronic beam-steering antenna of scanning angle 13° was established by replacing the metal-insulator-metal (MIM) capacitors with varactors     

漏波天线中阻带的应用及抑制

周期性结构会引入阻带.有些阻带对有些漏波天线有用,如可用于抑制某些不需要的传播模.但阻带对大部分周期性漏波天线是不利的,如边射阻带使得主波束在边射方向不能连续扫描.文中讨论了周期性结构阻带在漏波天线中的应用及抑制.给出了一个阻带应用实例:微带漏波天线一般工作于EH1模,在激励其EH1模时往往会激发不希望的EH0模,在微...     

On a Broadband Elevated Suspended-Plate Antenna with Consistent Gain

A design concept for elevating suspended-plate radiators is presented in this paper. The proposed antenna comprises two radiators connected by a folded feeding structure. The folded structure suppresses the occurrence of higher-order modes when the height of the antenna is elevated beyond 10% of the free-space wavelength, lambda₀ . The broadband radiating mechanism is explained. Both the simulation and measurement results show that a consistent gain of 7.2 dBi to 8.5 dBi is achieved over a frequency range of 2.3 GHz to 3.6 GHz, namely within a 44% impedance bandwidth for |S₁₁|< -10 dB. The concept is used to design two cost-effective broadband antennas covering both WLAN and WiMAX operations.     

Studies of suppression of the reflected wave and beam-scanning features of the antenna arrays

This paper describes a two-directional linear scanned design by integrating a short leaky-wave antenna (LWA) with aperture-coupled patch antenna arrays. This architecture proposes a technique not only having the advantage of suppressing the back-lobe due to the reflected wave in the short LWA but also producing two separate linearly scanned beams, each of them radiating in a different region of space (in both the front side and backside of the LWA). In this design, most of the reflected wave of the short LWA is coupled to the patch antenna arrays on the backside of the substrate. The phase of this coupled signal to each antenna element is adjusted by tuning the individual phase shifter in order to control electronically the patch antenna main beam in the cross plane (x<0). Meanwhile, on the front side, the main beam of the short LWA can be simultaneously scanned in the elevation plane (x>0) by changing the operating frequency. Hence, the two linear beam-scanning radiation patterns of individual direction can be created independently, including a narrow beam in the elevation plane (xy plane at x>0) at the front side and a broadside beam in the cross plane (xz plane at x<0) on the backside. The measured results show that the reflected wave of the short LWA in the proposed design is suppressed 8 dB as compared with a traditional short LWA without the aperture-coupled antenna arrays at 10.5 GHz. As a result, this novel architecture provides more flexibility both in the upward elevation plane (H plane) and the downward cross plane (backside-E plane) for possible beam-scanning applications in microwave communications and remote identification.     

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.     

振荡型有源集成天线

研制中心频率为18 GHz的振荡型有源集成天线,包括微带天线设计、单片压控振荡器(MMIC VCO)的设计及微带天线与单片压控振荡器二者的集成。微带天线的芯片面积为4.5 mm×3.5 mm,增益为3.67 dB,中心频率为18.032 GHz,最小输入驻波系数为1.098;单片压控振荡器芯片面积1.1 mm×1.0 mm,调谐范围为15.978～18.247 GHz,输出功率大于6 dBm。振荡型有源集成天线的方向图测试结果与微带天线的特性符合,该振荡型有源集成天线能够正常工作。     

Electronically scanned composite right/left handed microstrip leaky-wave antenna

A novel electronically scanned periodic microstrip leaky-wave (LW) antenna based on the concept of composite right/left-handed (CRLH) metamaterials is presented. This antenna includes varactors modulating the capacitive loading of the unit cell and therefore the propagation constant of the structure, which results in voltage scanning of the radiated beam. An accurate circuit model is proposed. The antenna is demonstrated experimentally to exhibit continuous scanning in the dominant mode from backward to forward angles. The scanning range is from -10/spl deg/ at 35 V to +7.5/spl deg/ at 0 V, and broadside occurs at 9 V, at the fixed frequency of 3.23 GHz.