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1.
Blind spots observed in structures consisting of a slot array and parasitic straight wire arrays are investigated. Each blind spot is found to be associated with either a pattern null or the excitation of a surface wave on the corrugated structure consisting of the parasitic wires and conducting screen, with the slots shorted. The plane-wave-expansion technique is used to evaluate the coupling between arrays. It is shown analytically that for structures consisting of a single wire array, the blind spot can exist only at broadside, where there is a pattern null for the parasitic wires. For structures with two-wire arrays, such as an array of Clavin elements, a surface wave can be excited at a particular scan angle provided a certain uniformity condition in the structure is satisfied. The information presented is relevant to the incorporation of parasitic wire arrays for scan compensation 相似文献
2.
The analysis of an endfire array of tunable parasitic slots is described. Self and mutual admittances between thin half-wavelength slots are found by an application of Babinet's Principle. To solve the circuit equations of the array, the condition is imposed that the phase velocity remain constant along the array. Then, by matrix inversion, the excitation amplitude and self-reactance of the parasitic elements are determined. The phase of the reflector is chosen to maximize the coupling between the driven element and the directors. Finally, experimental patterns are compared with computed results. 相似文献
3.
Crosspolarisation well below the prescribed side-lobe level of a travelling-wave array may be achieved, without using additional discriminating structures, by applying a circular, dielectric-filled waveguide with a sequence of circumferential gaps. Operated in the TM01 mode, a computer-designed X band prototype having a directivity of 27 dB was found to secure crosspolarisation of less than ?34 dB. 相似文献
4.
A new frequency notched ultra-wideband microstrip slot antenna with a parasitic tuning stub is proposed. The antenna is similar in configuration to a conventional microstrip slot antenna; by introducing a parasitic open-circuit tuning stub, flexible frequency notched function is achieved. Several properties of the antenna, such as frequency notched function, antenna transfer function and gain, have been investigated. As is reported, the operation bandwidth of the antenna is 2.91-11.16 GHz, in which a frequency notched band of 5.10-5.85 GHz has been achieved. Furthermore, good ultra-wideband linear transmission performance over the entire operation frequency range has also been achieved. 相似文献
5.
Analytic design of conformal slot arrays 总被引:1,自引:0,他引:1
Westerman C. Harrington V. Pyong Park 《Antennas and Propagation, IEEE Transactions on》1983,31(4):668-672
A completely analytic design process has been developed for small slot arrays which accounts for the varying effect of mutual coupling as a function of element position. A previously developed theory for the design of small arrays has been extended to include conformal dielectric-filled waveguide slot arrays. Computer software has been assembled which enables calculation of the slot geometries required to implement a specified aperture distribution and input impedance condition. The slot self- and mutual admittances are calculated numerically, thus eliminating the traditional measured slot data from the design process. This design technique has been applied to conformalX -band slot arrays on cylinders of a few wavelengths diameter. The arrays consist of multiple dielectric-filled waveguides, each of which is a narrow-band standing-wave linear array of longitudinal shunt slots. The computerized design process adjusts the length and offset of each slot in the total array until the desired aperture distribution and impedance match are achieved. A flow diagram of the design program and test results from experimental arrays are presented. 相似文献
6.
A novel ultra-wideband (UWB) circular slot antenna with a parasitic strip for immunity at 5.2/5.8 GHz is proposed. The antenna has an indented circular stub and an inverted C-shaped parasitic strip embedded inside the circular slot. The desired band-notched UWB operation can be obtained by choosing the size of the inverted C-shaped parasitic strip. The proposed antenna has advantages of low cost, compact size and easy design. Details of the proposed design and experimental results of the constructed antennas are presented. 相似文献
7.
The design of small slot arrays 总被引:13,自引:0,他引:13
The differences in mutual coupling for a central slot and a peripheral slot cannot be ignored in small arrays if good patterns and impedance are to be obtained. A theory has been developed whereby the length and offset of every slot in the array can be determined, in the presence of mutual coupling, for a specified aperture distribution and impedance match. The theory enlarges on Stevenson's method, and uses a modified form of Booker's relation based on Babinet's principle to treat nonresonant longitudinal shunt slots in the broad wall of a rectangular waveguide. A general relation between slot voltage and mode voltage is developed, and then formulas are derived for the active, self-, and mutual admittances among slots. These formulas result in a design procedure. Analogous treatments of inclined series slots in rectangular guide and of strip-line-fed slots are possible. Comparison between various experiments and the theory is presented. Tests of the theory include the resonant length of a zero offset slot, resonant conductance versus offset and resonant conductance versus frequency for a single slot, and self- and mutual admittances for two staggered slots. The design and performance of a two-by-four longitudinal shunt slot array is also described. 相似文献
8.
The radiation characteristics of microstrip antennas consisting of one centre-fed patch and several identical parasitic patches are studied experimentally. The configurations investigated include a five-element cross and three- and seven-element linear arrays. A significant increase in gain is obtained by using close interelement spacing, with no degradation in pattern characteristics. 相似文献
9.
The Elliot procedure for the design of a waveguide slot array is extended to the case of partially filled radiating waveguides. The dielectric slab lies on the top of the radiating waveguide, i.e. on the slotted wall. The proposed solution prevents some of the most common drawbacks of waveguide slot arrays. Results are validated against a commercial FEM software. 相似文献
10.
The feasibility of obtaining arbitrary polarization in both one- and two-dimensional arrays of slots in dual mode bifurcated Waveguides has been demonstrated. The radiating element consists of a pair of crossed slots in the sidewall of a bifurcated rectangular waveguide that couple to even and odd waveguide modes. One linear polarization is excited by the even or "sum" mode and the orthogonal linear polarization is excited by the odd or "difference" mode. By superposing the sum and difference modes in the proper amplitude and phase, any arbitrary polarization can be realized. A two-dimensional array consisting of eight waveguide linear arrays, ferrite phase shifters for scanning in the plane normal to the linear arrays, and a feed network for power distribution and polarization control was constructed. Good radiation performance for various polarizations was obtained. In the case of linear polarization, the cross polarization component was on the order of -25 dB and in the case of circular polarization, the axial ratio was on the order of 1 dB. The polarization was controlled with a ferrite phase shifter. Close-in sidelobes of better than 20 dB were obtained for all polarizations. The preceding performance characteristics were obtained over a scan range ofpm20deg and over a 6 percent frequency band. 相似文献
11.
12.
Internal higher-order mode coupling between adjacent longitudinal radiating slots cut in a broad wall of a rectangular waveguide is examined rigorously. Method-of-moments solutions to pertinent coupled integral equations are investigated. Higher-order mode coupling effects on the amplitude and phase of the aperture electric field are studied as a function of waveguide and slot parameters. It is shown that higher-order mode coupling effects are accounted for, to a substantial extent in standard-height waveguides and almost completely in reduced-height waveguides, by including the TE20 mode coupling in the analysis 相似文献
13.
Sidelobe suppression is demonstrated for 76-GHz post-wall waveguide fed parallel-plate slot arrays for car radar applications. Taylor distribution illumination control is successfully confirmed experimentally in the slot array on the parallel-plate waveguide. The amplitude distribution in the transverse direction is controlled by shaping a quasi-TEM mode and that in the longitudinal direction is realized by the slot coupling control, both in an oversized waveguide. Measured sidelobes are below -22 dB for one-dimensional (1-D) Taylor tapering while those for two-dimensional (2-D) Taylor distribution are below -18 dB. The gain reduction in comparison with that for uniform illumination is less than 1 dB both in the experiment. All these verify the potential of aperture illumination control of the parallel-plate slot arrays 相似文献
14.
15.
By using an appropriate objective function, simulated annealing is found to prevent the presence of weakly excited slots in feedmatched waveguide slot arrays designed to produce demanding power patterns 相似文献
16.
Gonzalez Picazo J.J. Calvo M. Besada J.L. Sahalos J.N. 《Antennas and Propagation, IEEE Transactions on》1990,38(11):1780-1783
A technique for the design of nonuniformly spaced waveguide slot arrays is proposed. The slots are in active resonance, and their position is adjusted so that the sources of the array will have the desired amplitudes and phases. The conductances of the slots depend on the desired pattern and the efficiency. Applications on Taylor and cosec 2&thetas; patterns have shown the validity of the method 相似文献
17.
A uniplanar leaky-wave antenna (LWA) suitable for operation at millimeter-wave frequencies is introduced. Both unidirectional and bidirectional versions of the antenna are presented. The proposed structure consists of a coplanar waveguide fed linear array of closely spaced capacitive transverse slots. This configuration results in a fast-wave structure in which the n=0 spatial harmonic radiates in the forward direction. Since the distance, d, between adjacent elements of the array is small d/spl Lt//spl lambda//sub o/, the slot array essentially becomes a uniform LWA. A comprehensive transmission line model is developed based upon the theory of truncated periodic transmission lines to explain the operation of the antenna and provide a tool for its design. Measured and simulated radiation patterns, directivity, gain, and an associated loss budget are presented for a 32-element antenna operating at 30 GHz. The uniplanar nature of the structure makes the antenna appropriate for integration of shunt variable capacitors such as diode or micro-electromechanical system varactors for fixed frequency beam steering at low-bias voltages. 相似文献
18.
A detailed analysis of infinite slot arrays excited by delta-function current sources is presented. The existence of severe array blindness is proved for most of the cases of slots without metallic cavity separators. 相似文献
19.
Varlamos P.K. Papakanellos P.J. Panagiotou S.C. Capsalis C.N. 《Antennas and Propagation Magazine, IEEE》2005,47(4):92-97
The,design of modified Yagi-Uda arrays with additional parasitic elements in the area of the radiating dipole, acting either as reflectors or directors, is presented. The genetic algorithms are employed, and various objective functions concerning gain, front-to-back ratio, and the latter combined with desired input impedance, are examined. Comparisons are made among the modified and conventional Yagi-Uda configurations for different weighting coefficients of the fitness functions. The modified Yagi-Uda array outperforms the conventional Yagi-Uda array, because it achieves higher performance standards over an extended bandwidth around 2.4 GHz. 相似文献
20.
Optical heterostructures composed of alternating three-dimensional dielectric layers are designed to have the same transmission and traversal time characteristics as quantum wire structures. In this manner, the time and transmission behavior of a quantum wire, very difficult to measure directly, can be determined from conventional optical measurements 相似文献