Mutual Coupling In Antenna Arrays Research Articles

Mutual Coupling in Antenna Arrays

Mutual Coupling in Antenna Arrays

UC-EBG on LTCC for 60-GHz Frequency Band Antenna Applications

The relatively high dielectric constant of the low-temperature cofired ceramic (LTCC) substrate materials can reduce the antenna gain and increase the mutual coupling in antenna arrays due to the increased surface-wave power. We present a design of a uniplanar-compact electromagnetic band-gap (UC-EBG) structure on the Ferro A6-S LTCC tape system operating in the 60-GHz frequency band. The UC-EBG design is used with an aperture-coupled microstrip-line-fed patch antenna (ACMPA) and with a 16-element array to increase the antenna gain. The UC-EBG is also used to reduce the mutual coupling between antennas in the E- and H-planes. The performance of the antennas with and without UC-EBG are evaluated with the probe-station and radiation-pattern measurements. In addition, the reflection from the UC-EBG surface is measured using a WR-15 waveguide excitation. Good agreement is achieved between the simulations and the measurements. An increase of up to 4.5 and 2.3 dBi is achieved in the gain for a single element and for a 16-element array, respectively. A reduction of up to 11.8 dB is observed in the E-plane coupling between two patches. The presented design is suitable for electromagnetic shielding, reduction of coupling in integrated LTCC modules, and providing high gain antennas for low-cost millimeter-wave applications.

Mutual Coupling Mechanisms Within Arrays of Nonlinear Antennas

In this paper, mathematical analyses and physical interpretations for the mutual coupling mechanisms within a finite nonlinearly loaded antenna array are presented. These analyses are based on the method of nonlinear currents with the array mutual coupling effects treated by a power series expansion technique. Initially, the antenna input terminals in an antenna array are related by an equivalent multiport microwave circuit. Each port of this equivalent circuit network is then treated by the method of nonlinear currents. The antenna array mutual coupling effect is considered in this linear network and treated by a power series expansion technique. This study gives not only full analyses, but also physical insight into the mutual coupling mechanisms of nonlinearly loaded antenna arrays.

Comparison of mutual coupling compensation to dummy columns in adaptive antenna systems

Compensation for mutual coupling in antenna arrays by matrix multiplication is compared to the use of dummy elements. A least squares estimation of the coupling matrix is made, including co- and cross-polar coupling. We show that compensation for measurements off the phase center is important as well as a proper assumption of the ideal element pattern. We study the performance of a dual polarized patch array with respect to far-field phase error, signal-to-interference reduction, and cross-polarization level. In all aspects, the performance of the compensation method exceeds or equals the use of dummy elements.

An Efficient Algorithm for the Steady-State Analysis of a Nonlineraly Loaded Antenna Array

In this paper, an efficient algorithm is developed to analyze the steady state response of a nonlinearly loaded antenna array under multitones excitation. The problem is equivalent to a multiport nonlinear microwave network problem with the network parameters of antenna array obtained by the moment method. The antenna array mutual coupling effects are included in the equivalent multiport network. This resulting equivalent network is then solved using an efficient successive over-relaxation algorithm. Numerical examples are shown to illustrate the capability of the proposed method and the intermodulation effect of the nonlinear loads. The proposed method is suitable for nonlinearly loaded antenna array under multitones excitation.

A circuit model for mutual coupling analysis of a finite antenna array

Mutual coupling effects within an antenna array play a very important role in the areas of EMC (electromagnetic compatibility) and antenna array design. A circuit model is developed to represent the input admittance of an antenna array with a finite number of elements. This model consists of a component to represent the input admittance of an isolated antenna element and infinite shunt components with each to represent different degrees of antenna mutual coupling effects. Twersky's (1952) algorithm of multiple scattering analysis is used to illustrate the physical meaning of each circuit component. Numerical results show that good accuracy for the antenna input admittance calculation can be obtained by using this model to the second order approximation. As the array is large and sparse, a very small amount of computation can yield good accuracy. This model is shown not only to be numerically efficient compared to the full wave analysis using the moment method, but also to give a physical insight into the antenna array mutual coupling mechanism. Furthermore, this model has no limitation on antenna array geometry and excitation.