Murli Dhar Singh

Study of the non-planar dipole antenna with transversely displaced feed-points †

A generalized analysis of the non-planar dipole antenna with transversely displaced feed-points is presented. This configuration is obtained by combining the two concepts. namely (a) the concept of inclined antenna and (b) the concept of displaced feed-points. The specific features of this antenna configuration is that it acts as a source of complex radiation, i.e. the field radiated by the antenna has three E vectors along the three orthogonal axes. Further, the effect of balanced and unbalanced feed as well as that of the displacement of the feed-points on the far-field radiation pattern radiation resistance, power gain, effective aperture and efficiency is evaluated. Typical plots and tables are given to elucidate the theoretical results. Some of the important applications of this configuration are also pointed out.

Log periodic antenna with loop elements

Abstract An idea of log periodic antenna with loop elements is presented. The electrical properties (radiation patterns, radiation resistance and efficiency, etc.) of this configuration are discussed. The merits and demerits of the proposed configuration are pointed out.

On the Theory of Axial Mode Helix

Considering the effect of ground plane, an expression for the far field radiation pattern has been derived. Due to the ground plane an image of the helix is formed. The helix and its image thus form an array of two identical sources in phase opposition. Theoretical pattern on this basis are compared with the existing measured patterns. It is concluded that there is a reasonably good agreement between the theoretical and experimental results. The effect of varying the phase centre with frequency has also been investigated.

Medium Gain Antenna for Ship-Satellite-ship Communication Link

Design details and performance of backfire antennas for use at ship terminal of the ship-satellite-ship communication link are discussed. Important applications and advantages of backfire antennas are pointed out.

A Note on the Suitability of Shipboard Terminal Antenna and Tracking Scheme for MARSAT System

After realizing the shipboard terminal antenna problem, associated constraints, performance and design considerations, a comparative study of various antenna suitable for satellite-ship-satellite communications has been presented. On the basis of their electrical properties, merits and demerits, the best configuration has been pointed out. Various tracking schemes have been compared and the appropriate cost effective scheme is sorted out.

A new log-periodic dipole antenna

Abstract A log-periodic antenna having triangular dipoles as its constituent elements is presented. The design criterion and its electrical properties are discussed. The proposed configuration is compared with the conventional log-periodic dipole antenna. It is shown that this configuration offers a better frequency transition, bettor gain and a reduction in the axial length over the conventional log-periodic dipole array.

Investigations on the electrical properties of the unbalanced non-planar dipole antenna†

Abstract A generalized analysis of the unbalanced centre-fed non-planar dipole antenna is presented. The specific feature of this antenna configuration is that it acts as a source of complex radiation, i.e. the radiated field has three E vectors along the three orthogonal axes. Further, the electrical properties such as radiation patterns, radiation resistance, power gain, aperture, and radiation efficiency are investigated as a function of unbalance ratio and the angle of inclinations. The variation of the electrical properties is illustrated by typical plots and tables.

Investigations on the Non-planar Log-periodic Antenna, having Tilted Dipoles

This paper presents theoretical and experimental investigations on the non-planar log-periodic dipole antenna, whose upper and lower halves contain dipoles, inclined by angles α1 and α2 respectively. Using the fact that a tilted dipole is capable of receiving horizontally as well as vertically polarized signals, it is mathematically shown that the utility of the log-periodic dipole antenna (LPDA) can be increased by tilting the constituent dipoles. Using the linear antenna array theory, the expressions for the far field radiation patterns, power gain and aperture, are derived. Calculations were made to predict the effect of Ψ (angle between the two halves of the LPDA) and the tilt angles (α1, and β2) of the dipoles on the radiation pattern, power gain and aperture of the non-planar log-periodic dipole antenna. Comparison is made between the theoretical and experimental results. It is concluded that both the results agree reasonably.

Modified log periodic dipole antenna with plane reflector

Abstract A theoretical analysis of the modified log periodic dipole antenna (MLPD) with plane reflector at its apex is presented. The half-power beam widths of E and H-pIane patterns are compressed and the beam compression varies with the parameters of the MLPD. Due to reflector and MLPD a gain improvement of the order of 4 to 5 dB may be achieved. It is also shown that the placement of the reflector at the apex of MLPD does not affect the wide-band performance of the MLPD.

A new technique for increasing the gain of the log periodic dipole antenna

Abstract A technique for increasing the gain of the log periodic dipole antenna is presented. An axially displaced half-wave dipole antenna provides a narrower half-power beam width and gives slightly increased gain as compared to the conventional half-wave dipole antenna. Using this fact it is theoretically shown that the gain of the log periodic dipole antenna can be increased by axially displacing the feed points of the constituent dipoles of the log periodic dipole antenna. Typical theoretical results are given for different values of the axial feed displacement.