Broadband Decoupling and Matching of a Superdirective Two-Port Antenna Array

Abstract

Decoupling and matching networks may be used to improve the performance of compact antenna arrays where mutual radiator coupling has caused a degradation of the diversity capabilities. A popular network consists of a 180deg rat-race directional coupler, which decouples the antenna ports, followed by impedance matching networks at each port. Researchers, however, usually neglect the presence of losses both within the antenna array and the decoupling and matching network. For this reason, we have built various narrowband and broadband matching networks and compare their performances with the help of calibrated far-field measurement data

Electromagnetic decoupling and complexity

“…. , θ N in (13) and (14) 6) The lower-triangular Cholesky factorization in step (4) can be replaced by an upper-triangular factorization. This results in a decoupling network whose topology is "flipped" relative to Figure 3.…”

“…Decoupling networks are shown to achieve the maximum channel capacity among all lossless matching networks when they are utilized in multiple-antenna communication systems [3]. When used in multiple-antenna systems, decoupling network designs fall into two main categories: those based on microwave couplers include [4]- [8]; those based on reactive components and transmission lines include [2], [9]- [16]. Examples for two antennas include [4], [5], [9]- [12]; three antennas include [6], [13]- [15]; four antennas include [7], [8].…”

“…When used in multiple-antenna systems, decoupling network designs fall into two main categories: those based on microwave couplers include [4]- [8]; those based on reactive components and transmission lines include [2], [9]- [16]. Examples for two antennas include [4], [5], [9]- [12]; three antennas include [6], [13]- [15]; four antennas include [7], [8]. Example papers using reactive components for N antennas include [2], [16], where particular antenna structures are considered, and [8], where imperfect decoupling is considered.…”

Antenna design challenges and solutions for compact MIMO terminals

“…The even mode (S 11 ) is observed to give significantly larger bandwidth than the odd mode (S 22 ), which implies that the approach may be suitable for systems (e.g., LTE) which only require MIMO operation in the downlink. One drawback in using decoupling circuits is the relatively low measured total efficiency of one or more of the decoupled ports (e.g., [6]), though no detailed analysis has yet been performed.…”

A Broadband Technique for a Decoupling Network in a Compact Antenna Array in a Mimo System

“…In [19,20], broadband performance was obtained using a hybrid coupler, but these couplers required too much space. In order to overcome the problems associated with their large size, an LCbased hybrid coupler was used [21], but it had a narrow bandwidth performance.…”