Novel broadband double pitch cylindrical helical antenna for satellite and ground applications

For spacecraft applications, the ability to predict the electrical characteristics of such an antenna is essential for the optimization of its size and weight. This paper investigates the effect of varying the length of uniform helical antennas made up of a thin copper tape, wound with a constant pitch angle, 12.8 degrees, on a Styrofoam core. It presents the analysis and modeling of uniform antenna with lengths varying from 1.5λ to 5.5λ wavelengths, at 1 GHz. It provides theoretical performance prediction for helices working in the axial mode in near circular polarization with an axial ratio between 1 dB and 2 dB and a return loss better than 20 dB. The tape is modeled with an equivalent wire. The antenna wire-grid models are created and then analyzed using the Lawrence Livermore Laboratory “Numerical Electromagnetic Code” (NEC) software package[1]. NEC computes the currents flowing on an interconnection of thin wires and evaluates the current flow on the helix and ground cup, and hence the far field radiation patterns, axial ratio, gain and beamwidth, as a function of frequency. The electrical characteristics of the helices are then imported into a relational database for comparison with the experimental results on helices already measured[3]. The simulated results are found in good agreement with the experimental ones, thus providing a reliable design tool for helical antennas.

Design and validation of uniform helical antennas, with varying lengths, using NEC

This paper is about the validation of modeling software that was developed to analyze and predict the theoretical performance of helical antennas in general and in particular those antennas using a metallic strip or tape as radiating elements. This was applied to uniform cylindrical helices as well as tapered helices with a single pitch angle and novel dual pitch antennas. Corresponding helices were built and tested. The experimental performances are in very good agreement with the theoretical results. This was investigated for helices working in the axial mode in near circular polarization with axial ratios between 1 and 2 dB and return loss better than 20 dB. This validation of the software, using Kraus' (1988) criteria for the equivalence of a tape element to a wire, against experimental results is providing a new, powerful, and accurate tool for reliably designing helical antennas, a much needed tool. This validation for tape helical antennas is particularly significant for space applications where deployability is required and optimization of the mass, site and gain of the antenna are essential.

Experimental validation of NEC analysis of software models of tape wound helical satellite antennas

The paper presents the results of a study of the main characteristics of coaxial antennas used for receiving and transmitting circularly polarized waves in two separate frequency bands. The method of determining the geometric parameters of these antennas under given requirements is introduced.

The characteristics of coaxial spiral antennas

Two cylindric helical antennas (CHA) being exited in an axial radiation mode at different frequencies have different helix diameters, and they can be placed in a coaxial manner one inside the other To obtain electrical characteristics of a coaxial helical antenna (COHA) similar to the characteristics of the single CHA in the required frequency band, it is necessary in the design to ensure an improvement in the isolation between the helices In this work the band properties of a COHA and ways to improve the isolation between helices are considered

Coaxial helical antenna with improved isolation

Design of concentric helical antennas for maximum gain and isolation over wide frequency separation

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Design of concentric helical antennas for maximum gain and isolation over wide frequency separation