A wideband neutralization line is proposed to reduce the mutual coupling of a compact ultrawideband (UWB) MIMO antenna. With the introduced decoupling method, the designed UWB MIMO antenna covers the band of 3.1-5 GHz with an isolation of higher than 22 dB. The proposed wideband neutralization line is not necessarily placed in the clearance area between two MIMO elements and can be put above the copper ground. A small clearance (antenna area) of 35 mm × 16 mm is achieved. The designed UWB MIMO antenna is fabricated. S parameters, radiation patterns, total efficiency and realized gain of the prototype are measured and compared with the simulations. Index Terms-MIMO, UWB antenna, mutual coupling 1536-1225 (c)

In analogy with the established discipline of room acoustics various aspects of diffuse wideband microwave propagation in a room are treated. It is shown that an equivalent to Sabine's equation for reverberation time in a room is valid for the completely diffused field, depending only on the volume, the surface area and an effective absorption coefficient. An exponential decay of the power versus delay is a consequence of the assumptions. Furthermore, the concept of a reverberation distance is also valid. This is the distance from a transmit antenna where the received diffuse, randomly scattered power equals the direct line-of-sight received power, such that the diffuse power dominates for distances larger than the reverberation distance. A number of measurements in a large room support the theory with an effective absorption coefficient of 0.5. The power delay profiles around the room from a transmitter in the ceiling vary only in the first arriving part of the impulse, whereas the tail being dominated by the diffuse field has the same power level for a given delay and the same decay rate all over the room. It is also a consequence of the theory that the incident diffuse fields on an antenna are uniformly distributed in angle. λ −))) 4ΙςΩΣΡΕΠ ΨΩΙ Σϑ ΞΛΜΩ ΘΕΞΙςΜΕΠ ΜΩ ΤΙςΘΜΞΞΙΗ 4ΙςΘΜΩΩΜΣΡ ϑςΣΘ −))) ΘΨΩΞ ΦΙ ΣΦΞΕΜΡΙΗ ϑΣς ΕΠΠ ΣΞΛΙς ΨΩΙΩ ΜΡ ΕΡ] ΓΨςςΙΡΞ Σς ϑΨΞΨςΙ ΘΙΗΜΕ ΜΡΓΠΨΗΜΡΚ ςΙΤςΜΡΞΜΡΚ ςΙΤΨΦΠΜΩΛΜΡΚ ΞΛΜΩ ΘΕΞΙςΜΕΠ ϑΣς ΕΗΖΙςΞΜΩΜΡΚ Σς ΤςΣΘΣΞΜΣΡΕΠ ΤΨςΤΣΩΙΩ ΓςΙΕΞΜΡΚ ΡΙ[ ΓΣΠΠΙΓΞΜΖΙ [ΣςΟΩ ϑΣς ςΙΩΕΠΙ Σς ςΙΗΜΩΞςΜΦΨΞΜΣΡ ΞΣ ΩΙςΖΙςΩ Σς ΠΜΩΞΩ Σς ςΙΨΩΙ Σϑ ΕΡ] ΓΣΤ]ςΜΚΛΞΙΗ ΓΣΘΤΣΡΙΡΞ Σϑ ΞΛΜΩ [ΣςΟ ΜΡ ΣΞΛΙς [ΣςΟΩ 4ΨΦΠΜΩΛΙΗ ΜΡ −))) %ΡΞΙΡΡΕΩ ΕΡΗ 4ςΣΤΕΚΕΞΜΣΡ 1ΕΚΕ⊥ΜΡΙ :ΣΠ 2Σ Τ ¥ %ΤςΜΠ (3− 1%4

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A transmission-line-based decoupling technique for dual-polarized multiple-input and multiple-output (MIMO)antenna arrays is presented and analyzed. The proposed scheme enables well-canceled coupling for the adjacent elements under co-polarization, without degrading the isolation of the cross-polarized ports. Firstly, a decoupling network based on the presented method for a 2×2 MIMO array is provided, along with a comprehensive design procedure. Calculations and simulations are operated to verify the decoupling performance. For further verification, a 2×2 dual-polarized patch array with the proposed decoupling method is developed. The decoupling network characterizes low profile, compact size, and low insertion loss, which is realized in a single layer. Measurements denote that the isolations between the co-polarized elements are improved from 16-20 dB to over 30 dB after decoupling at the center frequency of 2.45 GHz. Subsequently, based on the proposed 2×2 decoupling method, a decoupling network for large-scale dual-polarized MIMO arrays is presented. A design example of a 4×4 dual-polarized patch antenna array is established. Full-wave simulations indicate that the isolations are enhanced to better than 30 dB with a small insertion loss of less than 0.45 dB, and can widely be used for phased array and massive MIMO array systems.

Accurate characterization of spatial multipath channels at millimeter wave bands has gained significant interest both in industry and academia. A channel measurement was conducted at three different frequency bands, i.e., 2 − 4, 14 − 16, and 28 − 30 GHz in a line-of-sight (LOS) and an obstructed-LOS (O-LOS) scenarios in an empty room environment. A vector network analyzer connected to a virtual uniform circular array and to a rotational directional horn antenna was used in the measurements, respectively. Angle-of-arrivals and delay-of-arrivals of the multipath components were obtained from the measurements for the three frequency bands. Room electromagnetic properties for the three different frequencies at different propagation scenarios were investigated as well.

This paper introduces a planar switchable 3D-coverage phased array for 28 GHz mobile terminal applications. In order to realize 3D-coverage beam scan with a simple planar array, chassis surface waves are efficiently excited and controlled by three identical slot subarrays. Three subarrays switch their beams to three distinct regions. Each subarray works as a phased array to steer the beam within each region. Large coverage efficiency is achieved (e.g., 80% of the space sphere has the realized gain of over 8 dBi). The proposed antenna covers a bandwidth of over 2 GHz in the band of 28 GHz. User effects on the switchable array are also studied in both data mode and talk mode (voice) at 28 GHz. In talk mode, good directivity and beam switching can be realized by placing the switchable array at the top of the chassis (close to the index finger). And the user shadowing can be significantly reduced by placing it at the bottom of the chassis (close to the palm). In data mode, the switchable array, mounted at the top, achieves less body loss and larger coverage than at the bottom. The proposed antenna is fabricated and measured. The array at the top in talk mode is measured with a real human. The measurements align well with simulations.

Mobile terminals are often used indoor with the base station outdoors. At the mobile terminal the major part of the signal energy comes through openings in the building such as windows. Typically, only one of the sides in a room has windows, and seldom does a room have windows on all sides. Hence, the dominating signal can be expected to arrive at the mobile terminal from a narrow range of angles. Mobile terminal antennas used next to the head in speaking position will be directional due to the fact that part of the radiation pattern facing the head will be attenuated and reflected. Having a directive antenna in a directive environment, performance will depend on the orientation of the antenna in the radio environment. A new statistical spherical outdoor to indoor power spectrum model has been proposed to be able to calculate the directional performance of mobile terminals with a single or multiple antennas. The model consists of a major scattering area in one direction and more uniformly distributed minor scatterers in the other directions. A verification of the proposed model was performed and 60 data sets of spherical power spectrum measurements were collected in a typical urban environment. Using the new model, the directional performance of mobile terminal antennas including a human operator has been investigated through directional mean effective gain, branch power ratio, and correlation calculations using spherical radiation pattern measurements of a mobile terminal including the effect of 42 different persons. The accuracy of the calculated values was verified by directly measured values using 200 persons walking with the mobile terminal in the same office-like environments as where the spherical power spectrum measurements were performed.Index Terms-Correlation, diversity, handset antenna performance, mean effective gain, mobile terminal, spherical power spectrum model.

With the severe spectrum congestion of sub-6GHz cellular systems, large-scale antenna systems in the millimeter-wave (mmWave) bands can potentially meet the high data rate envisioned for fifth generation (5G) communications. Performance evaluation of antenna systems is an essential step in the product design and development stage. However, conventional cable conducted test methods are not applicable for mmWave devices. There is a strong need for over-the-air (OTA) radiated methods, where mmWave device performance can be evaluated in a reliable, repeatable, and feasible way in laboratory conditions. In this article, radiated testing methods are reviewed, with a focus on their principle and applicability for beam steerable mmWave devices. To explore the spatial sparsity of mmWave channel profiles, a cost-effective simplified 3D sectored multi-probe anechoic chamber (MPAC) system with an OTA antenna selection scheme is proposed. This setup is suitable for evaluation of beam-steerable devices, including both base station (BS) and user equipment (UE) devices. The requirements for the test system design are analyzed, including the measurement range, number of OTA antennas, number of active OTA antennas and amount of channel emulator resource. Finally, several metrics to validate system performance are described for evaluation of mmWave devices.