ISSN:0272-6343    

DOI:10.1080/02726340050082119

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

ISSN:0272-6343    

DOI:10.1080/02726340050082128

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

An array composed of spiral elements, each having a small number of turns, is numerically analyzed. The spiral elements are circularly arrayed above a ground plane and are excited by a single vertical feed wire. As the number of the spiral elements increases, the copolarization component of the radiation becomes omnidirectional. The maximum variation in the copolarization component as a function of azimuth angle is 0.8 dB for four spiral elements. Attention is also paid to an improvement in the axial ratio. A technique of using parasitic wires around the feed wire is presented. Calculations show that, when the distance between the feed wire for four spiral elements and the parasitic wires is appropriately chosen, the axial ratio is improved. The 3-dB axial ratio frequency bandwidth evaluated in the maximum beam direction is found to be 10%. Within this bandwidth, the gain is more than 5 dB.

ISSN:0272-6343    

DOI:10.1080/02726340050082137

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

An N-spiral array antenna mounted on a finite-length conducting cylinder of length 2Lyc and radius rcyis numerically analyzed using the method of moments (MoM). The analysis is performed with 2Ly

ISSN:0272-6343    

DOI:10.1080/02726340050082146

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

The spiral has been limited to applications for receive only because it is invariably loaded dissipatively, with a typical 3-dB loss and the resulting low efficiency. In this article, we treat the spiral as a traveling-wave (TW) structure that has unique ultra-broadband, complex, multi-facet radiation characteristics, and report development of spirals with efficient transmit performance suitable for all applications such as telecommunications and radar. Its excellent form factor and its size reduction potential are discussed. The spiral's unique geometry is also shown to allow easy and powerful switching, control and various manipulations, etc., to achieve performance and special features that are difficult or even impossible by antennas of other geometries. These unique multimode, multi-polarization, and inherent phase patterns are utilized to achieve ultra-broadband phased arrays and smart antennas for applications involving multifunction, real-time switched modes, among others.

ISSN:0272-6343    

DOI:10.1080/02726340050082155

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

A two-arm spiral antenna printed on a finite-sized dielectric substrate backed by an infinite-sized conducting plane is analyzed using the finite-difference time-domain method (FDTDM). The antenna is fed by a vertical probe located at the center of the antenna. The antenna height above the ground plane is 0.147 wavelength. The FDTDM analysis reveals that the antenna forms an elliptically polarized conical beam. Based on this investigation, two parasitic elements are introduced near the vertical feed probe to obtain a circularly polarized conical beam. It is found that the current on the vertical feed probe is approximately 180 out of phase with the currents on the two parasitic elements. This results in a reduction in the radiation from the feed probe, with a corresponding improvement in the axial ratio. The frequency response of the antenna with the parasitic elements is also calculated. The angle of maximum radiation is approximately θmax54 for a bandwidth of m 6.2% (0.982f to 1.044f). Within this frequency band, the axial ratio is less than 3 dB, and 0 0 the gain is approximately 3.2 dBi.

ISSN:0272-6343    

DOI:10.1080/02726340050082164

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

Previously, the broadband spiral class of antennas primarily consisted of the wire (or "printed")spiral and spirals with approximately complementary geometry. While both are very broadband radiators, they are still somewhat band-limited due to their associated balun structures, and bulky as a result of their absorbing cavities. A new type of spiral antenna utilizing slot radiating elements is presented that eliminates these drawbacks, relying instead on several new approaches to guarantee its frequency-independent operation over extremely broad bandwidths. The design and integration of a planar infinite balun/feed structure and very shallow reflecting cavity is presented and discussed, as is a new termination technique. Gain, axial ratio, and pattern measurements for both a 6" (15.24 cm)diameter spiral, with flow= 750 M Hz and 6.25:1 bandwidth, and an 18" (45.72lcm) diameter spiral, with flow= 250 M Hz and 15:1 bandwidth, are also given and reviewed.

ISSN:0272-6343    

DOI:10.1080/02726340050082173

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor

摘要:

Asimplified integral equation for a dielectric-coated antenna composed of arbitrarily connected straight-wire segments is formulated in a Hallen-type form. The derived integral equation contains only a single integral for numerical procedures. The current distribution obtained for a short helical antenna coated with dielectric material agrees with that for previously published results. As an application of the integral equation, a rectangular spiral antenna is analyzed to show the effects of dielectric coating on the radiation fields.

ISSN:0272-6343    

DOI:10.1080/02726340050082182

出版商:Informa UK Ltd    

年代:2000

数据来源: Taylor