Several papers published by prestigious Journals on Antennas and Microwave Techniques have disseminated misconceptions about total active reflection coefficient (TARC), a meaningful metric to characterize multiple‐input multiple‐output antenna arrays, and the misapprehension has been spread over the years. In this article, an extrapolation to calculate TARC for N‐antennas systems is derived and applied to published results for illustration purposes. Moreover, the inaccurate and correct TARC equations are put in context by means of its physic and mathematical insight, demonstrating the divergence of results when the interport RF isolation is comparable or higher than the port matching. The importance of assessing multiantenna systems using TARC is explained.
A multiple‐input–multiple‐output (MIMO) microstrip patch antenna array of four elements is proposed to cover the 5.8 GHz WLAN band. The characteristic mode analysis is carried out to design a defected ground structure that improves the MIMO performance without impacting negatively the radiation characteristics of the four‐element array. Simulations and measurements demonstrate that the implemented prototype reaches a maximum mutual coupling of −32 dB and a gain‐per‐element of 5.3 dB with good MIMO attributes, surpassing many other proposals in the antenna literature: maximum envelope correlation coefficient of 0.0001, diversity gain very close to 10 dB, capacity loss false(Clossfalse) near to 0.0023 bps/Hz at the resonant frequency, multiplexing efficiency )(ηmunormalxij of 0.935, and a total active reflection coefficient weakly dependent on the excitation phases. The presented design is proposed for operation on the IEEE 802.11a/n standard.
In this paper, a novel structure of two interlaced antenna arrays for MIMO applications is presented. It consists of two 2 1 triangular patch array antennas, which have all elements separated by a short distance among them (0.22λ 0), where mutual coupling can be very poor (S 21 =-7.81 dB). To overcome such weakness, a simple and efficient method is used: one neutralization line (NL) is introduced to increase the decoupling between both ports, reaching up to-29 dB at the central frequency, and below-20 dB over a large bandwidth. The whole MIMO antenna array has dimensions of 1.56λ 0 × 0.3λ 0 and has a gain of 9.11 dBi. Its diversity parameters describe it as a useful radiator for MIMO communications systems.
In this paper, a very low‐profile two‐port ultra‐wideband antenna for multiple input‐multiple output applications is proposed. The antenna is implemented by using two orthogonal quasi‐circular slot dipole radiators fed by coaxial lines. The antenna performs from 2 to 10 GHz, with an average peak‐gain of 4 dB, and high port isolation, with values around S21 = −20 dB and below. The radiation patterns of both antennas are opposite to each other and hence, the diversity gain reaches values around 20 dB. The low inter‐port coupling and low correlation are verified by obtaining the envelope correlation coefficient, which is lower than 0.003. These calculations were made by the S‐parameter and far‐field methods. The total active reflection coefficient shows that the antenna operative bandwidth does not change for different input signals with random phases, preserving the operation from 2 to 10 GHz. The antenna performance is compared to different state of the art slot configurations, showing advantages to previously published work.
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