Single-conductor strip leaky-wave antenna

This paper presents a leaky-wave antenna with only a single-conductor strip on a substrate without a practical ground plane. The full-wave integral equation method is used to investigate the EH/sub 01/ leaky mode of this single-conductor strip structure. When this single-conductor strip is on a thin substrate with a low dielectric constant, a broad-band radiation regime can exist for the EH/sub 01/ leaky mode. The balanced microstrip lines and the inverted balanced microstrip lines are used to excite this EH/sub 01/ leaky mode. This work presents both the numerically simulated and measured data. The measured bandwidth of a voltage standing-wave ratio /spl les/2 is from 6.55- 13.75 GHz (2.34:1). In this case, the normalized phase constant is very close to 1 and this results in a fixed main-beam radiation pattern in the end-fire direction. This leaky-wave antenna with only a single rectangle stripline of length 110 mm can achieve the same broad-band performance as a tapered microstrip leaky wave antenna with a length 310 mm, as previously reported by the authors.     

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     

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     

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.     

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     

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     

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.     

FDTD analysis of a metal-strip-loaded dielectric leaky-wave antenna

The finite-difference time-domain (FDTD) method is used to analyze a dielectric leaky-wave antenna comprising metal strips etched on a rectangular dielectric rod. The radiation patterns of the leaky-wave antenna with and without the transition are determined by using FDTD. The effects of the launching discontinuity on the performance of the antenna are discussed. In addition, the application of the perfectly matched layer (PML) technique to the three-dimensional (3-D) dielectric waveguide and its performance, compared to those of the Mur's (1981) first-order and super-absorbing Mur's first-order absorbing boundary conditions (ABCs) are described. In addition, the effects caused by perturbation on the wave propagation characteristics of dielectric waveguide are also discussed. The FDTD results are verified by a W-band experiment and found to be in good agreement     

An integrated quasi-planar leaky-wave antenna

A new quasi-planar leaky-wave antenna is presented. It consists of microstrip line on one side of the substrate and uniplanar circuit on the other side placed in a partially opened waveguide. The leakage is produced by the excitation of the first higher order (odd) microstrip mode coupled electromagnetically through a slotline on the opposite side of the substrate. Theoretic results based on rigorous Green's impedance integral equation method show that the new microstrip-slotline-coupled leaky-wave antenna has a broadband tuning range via structure parameters and is insensitive to the microstrip line width variation. Measured relative power absorbed (RPA) results indicate that the useful frequency bandwidth agrees with that predicted by rigorous field theory. The measured antenna radiation patterns also agree very well with the approximate theoretic computations. The theory and experiments show that the proposed leaky-wave antenna can interface to feeding structure easily and directly. The new antenna may become a good candidate for microwave and millimeter-wave integrated antenna design     

一种新型定频波束可调微带漏波天线的仿真研究

提出了一种新型的定频波束可调微带漏波天线.通过在微带漏波天线的辐射边缘周期性地加载微带电感,可减小微带漏波天线的相位常数,进而减小微带漏波天线的主波束方向角.微带电感是一末端短路的短微带线.应用时域有限差分法(FDTD)对这种加栽微带电感的微带漏波天线进行仿真分析得出,当频率为10.5GHz,未加载微带电感的微带漏波天线主波束方向角为53.,加载微带电感可使得微带漏波天线主波束方向角减小到11.,当减小微带电感的长度或减小微带电感间的距离时,微带漏波天线主波束方向角会减小.本文FDTD仿真结果与软件HFSS仿真结果十分吻合.     

Aperture field of a leaky-wave antenna of finite length

An anomaly in the radiation field of a leaky-wave slot antenna is apparent when experimental and theoretical results are compared. An investigation of the field along the aperture of the antenna, in which experiment is supported by theory, indicates that this is probably due to the continuous excitation of a TEM wave along the slot itself.     

94 GHz dielectric slab-line leaky-wave antenna

A leaky-wave planar antenna for millimetre-wave frequencies is described using a dielectric slab line, fed by a slotted waveguide array. The radiation of the planar antenna is induced by line discontinuities such as metallic discs on the guide surface.     

A broad-band coupled-strips microstrip antenna

A coupled-strip microstrip antenna with increased bandwidth and increased polarization purity is presented. We have demonstrated the underlying principle of its operation using even/odd modes of the coupled strips. An optimized parameter set for three coupled strips is obtained. The VSWR=2, impedance bandwidth of this antenna is 23% for antenna thickness of 0.083λ₀     

Periodically slotted dielectrically filled parallel-plate waveguideas a leaky-wave antenna: E-polarization case

The analysis of a periodically slotted dielectrically filled parallel-plate waveguide as a leaky-wave antenna for infinite and finite periodic structures for the E-polarization case is discussed. For the analysis of the infinite periodic structure, an integral equation in which Floquet's modes and the strip electric current satisfying the edge condition are used and Bloch wave analysis using the single-slot equivalent circuit parameters are employed. An integro-differential equation with moment-method and transmission-line analysis with equivalent circuit representation are used to analyze the finite N-periodic structure. Results of interest such as complex propagation constant and the radiation pattern for the finite slot number case are observed to be in good agreement with those of the infinite geometry case for the appropriately chosen values of slot numbers, slot width, period, and waveguide height     

Periodic receiving broad-band antenna arrays

The principle of the periodic receiving antenna array composed of arbitrary antenna units has been developed. A generalization of the well-known principle of log-periodic antennas is presented and applied also to antenna units formed by the system of dipoles with active networks. This reveals the potentialities for the exploitation of this principle in the miniaturization of directional antenna systems.     

A leaky-wave antenna in nonradiative dielectric waveguide

A leaky-wave mechanism in a nonradiative dielectric (NRD) waveguide is described. The antenna used in the analysis consists of a long slot in one ground plane of the NRD guide; the currents present in the side walls cause the slot to radiate as a traveling-wave antenna. The antenna was designed to operate at 9.5 GHz to reduce the costs involved in working at high frequencies. The analysis of the slot follows the procedure outlined by L.O. Goldstone and A.A. Oliner (1959). A simple expression for the amount of coupling from the guide is derived under certain assumption made because information on the reactances necessary to model the slot is not as yet available. The theoretical coupling values verified by measurement and the design, construction, and performance of both leaky-wave antennas are described     

A novel two-beam scanning active leaky-wave antenna

A novel two-beam scanning active leaky-wave antenna (LWA) has been developed. This LWA with a two-terminal feeding microstrip line structure is integrated with a varactor-tuned X-band high-electron mobility transistor (HEMT) voltage-controlled oscillator (VCO). The signal of the VCO is injected via a T-divider into the radiating element. To excite the first higher order mode, the designed antenna is fed asymmetrically at both ends of the microstrip line. Compared with single-terminal feeding leaky-wave antennas, this configuration offers the advantages of dual-direction and suppression of the reflected wave caused by the open end of the radiating element. The scanning angle is steered over a range of 24-46° for the right beam and 128-150° for the left beam. The effective isotropic radiated power (EIRP) is calculated to be 17.5 and 16.67 dBm at 10.4 GHz, respectively. The measured return loss S₁₁ is less than -10 dB in the range of 9-11.5 GHz. The transmission coefficient S₂₁ indicates that the power radiates into the space     

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)     

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