Designer's Notebook Research Articles

A New Design Approach for a Hybrid Monopole to Achieve Increased Ultrawide Bandwidth [Antenna Designer's Notebook

A design approach has been explored and successfully demonstrated to achieve an improved gain of a hybrid monopole maintaining its optimum achievable bandwidth. This challenge has been resolved based on the knowledge acquired in earlier investigations. A three-segment composite dielectric ring resonator (DRR) has been designed and fabricated. This, along with a vertical monopole, promises about 137% (5.4:1) matching bandwidth with consistent monopolelike radiation and 6-10-dBi gain over the entire band. Two sets of customized prototypes have been realized and experimentally validated to furnish the predicted characteristics in transmit and receive modes, both in frequency and time domain.

Reply to "Comments on 'Loss Mechanisms in the Electrically Small Loop Antenna'\" [Antenna Designer's Notebook

Presents a reply to comments on “Loss mechanisms in the electrically small loop antennas,” (Austin, B.A., et al, IEEE Antennas Propagat. Mag., vol. 56, no. 4, pp. 142–147, Aug. 2014.

Comments on \"Loss Mechanisms in the Electrically Small Loop Antenna\" [Antenna Designer's Notebook

Presents comments on “Loss mechanisms in the electrically small loop antennas,” (Austin, B.A., et al, IEEE Antennas Propagat. Mag., vol. 56, no. 4, pp. 142–147, Aug. 2014.

Pencil Beams and Flat-Topped Beams with Asymmetric Sidelobes from Circular Arrays [Antenna Designer's Notebook

Given a circular antenna array, and a requirement for the sidelobes surrounding a pencil beam or flat-topped beam to have a specified ϕ dependence, it can be advantageous to optimize the array excitations for the best fit between the far field and a pattern synthesized for a continuous circular aperture of the same size.

Ideas for Antenna Deigner's Notebook [Antenna Designer's Notebook

Ideas for Antenna Deigner's Notebook [Antenna Designer's Notebook

Ideas for Antenna Deigner's Notebook [Antenna Designer's Notebook

Ideas for Antenna Deigner's Notebook [Antenna Designer's Notebook

Center Wavelength Design Frequency [Antenna Designer's Notebook

This study describes a design frequency for designing resonant antennas and microwave structures. Antenna design at the center frequency is a common method for designing resonant antennas. When the designers begin an antenna design, they start to fi nd the center frequency by just taking the average of the target frequency-range boundaries. In fact, the dimensions are inversely proportional to the frequency, and directly proportional to the wavelength. This paper explains that the frequency of the center wavelength must be used as the design frequency.

Design Approach for Robust UHF RFID Tag Antennas Mounted on a Plurality of Dielectric Surfaces [Antenna Designer's Notebook

A design approach is presented for passive UHF RFID tag antennas to function efficiently when mounted on a wide variety of dielectric materials of arbitrary thickness. It is well understood that the presence of materials can detune an antenna by shifting its operational band. It is therefore important to design tags that can accommodate such a shift in frequency due to material effects. In this paper, we propose a way to modify existing classical tag designs to enable them to operate over a wide range of materials (3 < εr < 13 ) and arbitrary thickness. Experimental results showed that when compared to commercially available tags, the modified tags achieved better performance when mounted on a wide range of materials.

Loss Mechanisms in the Electrically Small Loop Antenna [Antenna Designer's Notebook

The characteristics of an electrically small loop antenna are readily calculable. Being an inherently high-Q device, it requires careful tuning. Its performance as a transmitting antenna is sometimes limited by low radiation efficiency because of inherent losses, combined with a radiation resistance that varies as the fourth power of frequency. An apparent anomaly, frequently encountered in practice, is that the measured Q factor differs significantly from that calculated or obtained by computer simulation. This finding has led some to believe that the loop has a higher radiation resistance than conventional analytical techniques would imply. However, this conclusion is unfounded. Experimental evidence presented here indicates that Q factors close to those predicted can be achieved when appropriate consideration is given to reducing the loss associated with the tuning-capacitor mechanism, in particular. The ground loss (another significant factor) is also calculable, but since it decreases rapidly with increasing loop height above ground, its effect can readily be reduced. Vital to the experimental program that accompanied this work was an effective method - using a toroidal transformer - of measuring the total resistance of the loop.

Design Guidelines for the Cylindrical Dielectric Resonator Antenna Using the Recently Proposed HEM12d Mode [Antenna Designer's Notebook

Excitation of the higher-order HEM12d mode in a cylindrical dielectric resonator antenna (CDRA) was a big challenge, which was recently resolved by the present authors, nearly 30 years after the invention of the dielectric resonator antenna (DRA). Significantly, the radiation characteristics of this mode closely follow those due to the HEM11d mode, but with relatively higher gain. This breakthrough was made possible by introducing a new concept of feeding, and this was experimentally verified using a single prototype. Here, we have thoroughly investigated the design opportunities and limitations in terms of the material properties and dielectric resonator antenna's dimensions. Based on acquired knowledge, a comprehensive design guideline is provided to facilitate future designers estimating the best possible configuration for any specified application. As a significant part of this, the feed design has also been addressed. For practical verification, a customized dielectric resonator antenna was fabricated and measured, indicating excellent agreement with the proposed guidelines.

Ideas for Antenna Deigner's Notebook [Antenna Designer's Notebook

Ideas for Antenna Deigner's Notebook [Antenna Designer's Notebook

Antenna Designer's Notebook

Antenna Designer's Notebook

Direct radiating array design via convex aperture synthesis, pareto front theory, and deterministic sampling [antenna designer's notebook

A deterministic method for the design of direct radiating arrays for multibeam satellite applications is presented in the current work. The method embodies the following steps: First, we consider the problem of continuous aperture synthesis, subject to directivity-pattern mask constraints. We succeed in stating the problem as a convex magnitude antenna design that exhibits a second-order cone program form. The solution provides the optimum continuous aperture current-density distribution. Second, exploiting the optimum solution, analytical formulas, in the form of the Pareto front, are presented through which the proposed method determines the minimum number of radiating elements that must be used in the process of transforming the continuous aperture to an antenna array. Third, an effective deterministic sampling approach is contributed to produce a discrete array with the desired characteristics. Armed with the above, the current work provides a generalized framework for the design of direct radiating arrays for multibeam satellite applications. The method is validated by the provided design examples.

Comment on the definition of antenna half-power and impedance-matching bandwidths [antenna designer's notebook

There are two antenna-bandwidth def nitions that are sometimes confused. These def nitions are for the antenna half-power bandwidth (HPBW) and the antenna impedance-matching bandwidth (IMBW). These are def ned below.

Antenna Designer's Notebook

Tom Milligan is this month's editor of the Antenna Designer's Notebook.

Ideas for Antenna Deigner's Notebook [Antenna Designer's Notebook

Ideas for Antenna Deigner's Notebook [Antenna Designer's Notebook

A Cautionary Note on Optimization [Antenna Designer's Notebook

It is always nice to be told that one's to a problem is optimal. We like to think we have the solution, even though as engineers, we should be aware that for very few problems is the quality of the really a uni-dimensional variable with a unique maximum. In the real world, a best solution is usually the result of painstaking exploration of a Pareto frontier, the dimensions of which do not in general lend themselves to being neatly bundled a priori in some scalar function.

Antenna Designer's Notebook [Introduction

Presednts a summar abstract for the paper Determination of Antenna Q from the Reflection-Coefficient Data.

Determination of Antenna Q from the Reflection-Coefficient Data [Antenna Designer's Notebook

Equivalent circuits containing frequency-variable radiation resistances are postulated for small monopole and small loop antennas above a ground plane. The equivalent circuits are valid below the first natural resonance frequency. By adding an external series inductance or a parallel capacitance, the antenna's Q is evaluated with the use of an invariant form for the reflection coefficient. The antenna's Q obtained this way accurately predicts the maximum obtainable bandwidth for either a single- or double-tuned matched antenna. At frequencies above the first resonance, the Q is evaluated by approximating the impedance or the reflection coefficient with polynomials within a narrow frequency range.

Ideas for Antenna Deigner's Notebook [Antenna Designer's Notebook

Ideas for Antenna Deigner's Notebook [Antenna Designer's Notebook