Janne Ilvonen

In this paper, a dual-polarized end-fire antenna array is proposed for the 5G smartphone applications. The antenna covers all five defined millimeter-wave (mm-wave) frequency bands, namely n257, n258, n259, n260, and n261, which are used for mobile communications. Electrical dipole antenna is used to achieve the horizontal polarization, and a parasitic element is included for bandwidth enhancement. A shorted-patch antenna functions as a magnetic dipole facilitating the vertical polarization. Additionally, the broadband operation is realized by a novel stacked structure consisting of two different shorted patches. A four-element antenna array is implemented with overall size of 22.6 × 5 × 1.6 mm ³ . The operating frequency band of the proposed antenna array spans from 24 to 44 GHz with −10-dB reflection coefficient for both polarizations. The isolation between the array elements remains above 13 dB across the entire frequency band of interest. The peak realized gain varies from 8.4 to 10 dBi, and the spherical coverage at CDF= 100% and CDF= 50% of EIRP are 22.5 and 12.5 dBm, respectively. The measurement results of the fabricated antenna array agree well with the simulation results.

In this paper, a dual-polarized frequency-reconfigurable mm-wave patch antenna array is described. The design incorporates varactor diodes symmetrically loaded onto the four corners of a square patch. Parallel plate series capacitors are constructed to achieve the required low total capacitance by moving the square patch to an inner layer. Additionally, novel dual-function shorting vias are implemented into the structure, which serve as RF choke for providing dc-bias voltage to the varactors, and behave as shunt inductive loadings to improve radiation efficiency. A four-element antenna array is implemented, and placed into a 21×4.5mm ² cavity. The proposed antenna array can be tuned from 23.2 to 30.2 GHz by adjusting the varactor capacitance from 0.22 to 0.033 pF. The array achieves over 20-dB isolation between the orthogonal-polarized antenna elements, and more than 15-dB isolation between the same-polarized antenna elements. Total efficiency exceeds -2.5 dB across the tuning range. Peak gain varies from 8.9 to 10.5 dBi. The proposed dual-polarized antenna array offers notable advantages including a wide frequency-tuning range, high efficiency, compact size, and beam-forming capability.

Additional antennas are needed in smart phones to support 5G bands. The metal rim, which is the most attractive position for antennas, is already fully occupied by antennas supporting legacy bands. Therefore, there is a growing interest in new, more challenging antenna locations, such as the back cover of the phone. In this paper, we introduce a dual-polarized frequency reconfigurable wideband planar multiport antenna to the back cover of a mobile phone. The antenna has a height of only 0.5 mm. The simulations show that the introduced antenna achieves better than 5.8 dB efficiency from 3.3 GHz to 4.2 GHz.

This article presents an extremely low-profile tunable antenna design for smartphones with height of only 0.75 mm. The proposed antenna is integrated into the back cover of the device to utilize the existing gap between the battery and the back cover as efficiently as possible. By utilizing both tunable components and adjustable feeding weights, the designed multiport antenna system covers 3300–4200 MHz frequency range with 100 MHz instantaneous bands. In addition to just frequency tuning, these tunable elements can be utilized to adapt the antenna for different operation environments, such as changes in the structure of the device or the user effect. We show that the proposed antenna can be extended for two- and four-element multiple-input multiple-output (MIMO) operation. The proposed design is manufactured and measured, and the results confirm good antenna performance with average total efficiencies of 35% and 25% in free space and with a hand phantom, respectively.

This article describes a dual-polarized end-fire antenna array for millimeter-wave frequencies. The antenna consists of a chain-slot-shaped pattern on a mobile phone metal frame. The antenna is fed using a transmission line, which would cause only a negligible capacitive loading of the sub- 6 GHz antenna realized on the same metal frame and, therefore, would not significantly degrade its perfomance. This makes colocating the sub-6GHz and mm-wave antennas in the same, shared volume possible. Measurements indicate that a 4-element array placed within a mobile phone provides a realized gain between 8 and 12.6 dBi for both polarizations across the entire band from 24.5 to 29.5 GHz. The total efficiency of a single element is better than -2 and -3 dB for the whole band for horizontal and vertical polarizations, respectively.

This article presents a dual-polarized millimeterwave end-fire antenna array for mobile devices. The antenna array is integrated inside a metal-framed mobile phone and radiates through a 20 × 3.5mm2 window in the metal frame. Measurement results show a realized gain above 6 dBi for the frequency band of 28 to 33 GHz for a 3-element array. Beamsteering up to ±40° is possible. The array is physically offset from the metal frame, thus minimizing the capacitive loading effect on the sub-6GHz antennas. Moreover, due to the lack of mechanical contact between the frame and the antenna module, the antenna is robust against external impacts or hits to the phone. The design of the antenna module facilitates integration in mobile devices for mm-wave operation.

This paper introduces an S-parameter-based method for characterizing and improving the electromagnetic (EM) isolation between antennas in handsets. Eight different antenna placements are investigated across a frequency range of 400- 6000MHz covering all possible LTE-A bands. Simulations of realistic antenna elements validate the theoretical results. The results show that at least three antennas are needed in order to find a well-isolated pair at a given frequency.

Ranking different nonresonant antenna structures is impossible, if their achievable potential with a matching circuit is ignored when designing the radiating parts. Novel bandwidth estimators offer an efficient tool to seek optimal antenna structures. This letter systematically analyzes a certain representative set of capacitive coupling element antennas and gives guidelines for finding the best antenna structures. The obtained results for one-element structures are applied to design a two-element antenna for the bands 0.7-0.96 and 1.71-3.5 GHz. A prototype demonstrates that the choices made based on the theoretical study and ideal simulations steer the antenna solution to produce the required performance. Consequently, the presented systematic approach may promote the development of antennas in future.

Bendable mobile terminal antenna structures are analysed using computer simulations, both in free space and in the presence of the user's wrist. The purpose of the study is to see how the performance of the antenna changes in the presence of the user compared to the changes already occurring due to the altered shape of the device. Based on the obtained results, frequencies below 1 GHz pose the most stringent requirements on the choice of ground plane dimensions in terms of performance in the presence of the user. Also, the same ground plane size is not the best one taking into account the different frequencies and parameters such as frequency detuning and radiation efficiency.