摘要:

The basic polarisation properties of spiral antennas are considered by means of circularly polarised spherical waves (CPSW). At first, specific properties of the CPSW and their impact on the antenna polarisation are discussed and conditions for the radiation of pure circular polarisation are identified. Then, symmetrical multi-arm structures are introduced as a general class of antennas which permits an optimisation of the polarisation performance by a suitable control of the CPSW spectra. Finally, the specific CPSW spectra of planar spirals - one member of this class - are discussed. An explanation of the polarisation properties of planar spirals and some design guidelines are derived from this discussion.

ISSN:0272-6343    

DOI:10.1080/02726349408908386

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Multi-arm spiral antennas can be considered as antenna arrays where the spiral arms constitute the array elements. The proximity of the arms over the full length of the spiral and their direct coupling make such arrays unique in the sense that they operate with very strong mutual coupling. As a consequence, the array performance is dominated by the array configuration, rather than the array elements. In particular, the phase mode concept that is used successfully for the analysis of circular arrays can be used also for investigation of these arrays.

ISSN:0272-6343    

DOI:10.1080/02726349408908387

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

An extensive parametric analysis of conductor-backed square Archimedean spiral antennas has been conducted numerically by the method of moments. The results show that, at a near quarter wavelength above the ground plane, the square spiral yields a 1:1.21 bandwidth of the boresight axial ratio less than 3 dB. It also demonstrates that the axial ratio of the square spiral is controlled not only by its outer perimeter but also by its arm length. Design charts on the selection among wire radius, arm spacing, and spiral ground-plane height are presented as general guidelines for the design of circularly polarized conductor-backed square Archimedean spiral antennas.

ISSN:0272-6343    

DOI:10.1080/02726349408908388

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A two-arm Archimedean spiral antenna operating in the second mode is investigated numerically and experimentally. The effects of the presence of the Infinite plane conducting reflector on the radiation characteristics are studied using an integral equation technique. A traveling-wave type current is realized due to the mutual coupling between the real and image spirals, provided the antenna height is appropriately chosen, in spite of the fact that in the absence of the reflector a standing wave is appreciable in the current distribution. The operating bandwidth of the spiral antenna is discussed in detail. Experimental results are also presented to verify the numerical results.

ISSN:0272-6343    

DOI:10.1080/02726349408908389

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:0272-6343    

DOI:10.1080/02726349408908390

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A method of moments formulation for the current on arbitrarily shaped planar conductors in layered media is utilized to study the characteristics of printed spiral antennas. This algorithm permits the use of distributed and lumped impedance loads on the conductor. Also, it takes advantage of the discrete rotational symmetry exhibited by certain structures, thus reducing the matrix storage requirements. Numerical results are presented for two-arm and four-arm spiral antennas. Resistive loading along the outer portions of the spiral is used to eliminate reflected current contributions. For conductor-backed printed spirals, the presence of the ground plane reduces the amount of mode 1 radiation, allowing for the radiation of higher order spiral modes. Increasing the number of the spiral arms is shown to alleviate this problem by increasing the order of the first contributing higher order mode.

ISSN:0272-6343    

DOI:10.1080/02726349408908391

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The derivation process of a pair of H-type integral equations is reviewed for a system composed of curved wires and slots. The integral equations are characterized by two kernels Π and Π#, each being expressed in closed form. The integral equations are applied to a two-arm slot spiral antenna fed by two wires. Each feed wire is not in contact with the edge of the slot. The magnetic current distribution on the slot spiral, the radiation pattern, and the axial ratio are presented. The 3-dB axial ratio bandwidth is calculated to be 18%.

ISSN:0272-6343    

DOI:10.1080/02726349408908392

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A monofilar Archimedean spiral is adopted as a circularly polarized slot radiator which is electromagnetically coupled to a feed line. Numerical analysis of the coupling between the slot and the feed line reveals that, when the slot arm length is properly chosen, a traveling-wave magnetic current is distributed along the slot, leading to the radiation of a circularly polarized wave. On the basis of this radiation mechanism, a spiral slot printed antenna fed by a triplate transmission line is experimentally designed to obtain a unidirectional radiation beam. It is found that an axial ratio of 0.6 dB is achieved, and that the spiral slot is matched to the transmission line with a VSWR of less than 1.5. An array antenna composed of 32 printed spiral slots is constructed, attaining a 5 % bandwidth for a 3-dB axial ratio criterion. The formation of several tilted beams is also demonstrated.

ISSN:0272-6343    

DOI:10.1080/02726349408908393

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor