Uncoupled Matching for Active and Passive Impedances of Coupled Arrays in MIMO Systems

Abstract

Abstract-Impedance matching for coupled antenna arrays has received considerable attention in the research community. Because optimal matching requires implementation of a coupled network, leading to high complexity and often narrow operation bandwidth, new research has focused on the development of uncoupled matching networks with good performance. This paper explores traditional uncoupled impedance matching techniques for coupled arrays, specifically matching to the array active and passive impedances, within the context of multiple-input multiple-output communication. The concept of matching to the array active impedance is extended to the case where the propagating field is specified stochastically, and the performance of this solution is compared to that of traditional solutions using simulations. While emphasis is placed on matching for maximum power transfer, the paper concludes with a discussion on matching for minimum amplifier noise figure.

Capacity maximisation of handheld MIMO terminal with adaptive matching in indoor environment

“…Earlier studies have confirmed that uncoupled matching networks for multiple antennas (i.e. one matching network per antenna) can be used to enhance the capacity of closely-spaced half-wavelength dipole antennas in a given propagation environment (see [3] and references therein). In particular, the capacity improvement results from an optimal trade-off between received power and correlation.…”

Impact of Antenna Design on MIMO Performance for Compact Terminals With Adaptive Impedance Matching

“…A number of other contributions deal more explicitly with the propagation environment as part of the MIMO system performance evaluation [7]- [9]. In [7], reception of correlated fields from two closely spaced dipoles was studied in terms of received power, correlation and capacity.…”

“…The simulation study showed that capacity gains from several matching conditions differed significantly for two different propagation channels, with uniform 2D angular power spectrum (APS) and a Laplacian 2D APS, respectively. Further studies in [8] and [9] that involved three-element arrays revealed that allowing the matching states to differ across the antenna elements can offer substantially larger performance gains. Moreover, simulation results of capacity using different propagation environments in [9] showed that for low SNR or high mutual coupling, active matching outperforms passive (or fixed) matching due to beamforming gains.…”

“…Further studies in [8] and [9] that involved three-element arrays revealed that allowing the matching states to differ across the antenna elements can offer substantially larger performance gains. Moreover, simulation results of capacity using different propagation environments in [9] showed that for low SNR or high mutual coupling, active matching outperforms passive (or fixed) matching due to beamforming gains. However, for moderate coupling or high SNR, passive impedance matching enables better use of the multiple communication modes.…”

Antenna design challenges and solutions for compact MIMO terminals

“…First, the focus is on the problem of coupling [1]- [3] and a new metric to characterize the system performance of MIMO antennas [4]. Then, we outline strategies to mitigate the problem of coupling, i.e., decoupling the antennas [5]- [8] or matching the antenna to the environment [9], [10]. This is followed by the use of the theory of characteristic mode to analyze the negative impact of ground plane excitation on the performance of MIMO antennas [11], [12].…”