Browsing by Author "Khripkov, Alexander"

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  • Capacitively-Loaded Feed Line to Improve mm-Wave and Sub-6 GHz Antenna Co-Existence
    (2020) Kurvinen, Joni; Montoya Moreno, Resti; Lehtovuori, Anu; Ala-Laurinaho, Juha; Khripkov, Alexander; Ilvonen, Janne; van Wonterghem, Jari; Viikari, Ville
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The co-existence of millimeter-wave (mm-wave) and sub-6GHz antennas in a smartphone presents many performance-limiting aspects. When both antennas are attached to the metal frame, the feed lines of the mm-wave antennas might short-circuit the sub-6GHz antennas, and thus, may significantly affect their performance. This paper presents a method to design feed lines that function as transmission lines at mm-wave frequencies but correspond to open circuits at sub-6GHz. This study determines, in theory, the smallest achievable capacitive loading with different line types and experimentally validates the approach. The capacitive loading due to the feed line is small enough to maintain the sub-6GHz performance. At the mm-wave band, the insertion loss of the line is 1dB with a measured reflection coefficient below −10dB. The introduced common-mode capacitive load of the feed line on the sub-6GHz antennas corresponds to 0.19pF capacitance.
  • Connected Dipole Antenna Cluster of Enhanced Spherical Coverage CDF for mm-Wave Applications
    (2023) Chen, Quangang; Ala-Laurinaho, Juha; Khripkov, Alexander; Ilvonen, Janne; Moreno, Resti Montoya; Viikari, Ville
     A4 Artikkeli konferenssijulkaisussa
    In this paper, we present an antenna cluster concept operating in millimeter-wave (mm-Wave) frequency bands for 5G applications. Unlike conventional arrays made up of identical elements, a cluster array is constructed using non-identical dipoles with high coupling that are placed in a 2-mm wide slot. The cumulative distribution function (CDF) of the spherical coverage gain is used to evaluate the beam-forming capability. High coverage gain over a wide band can be achieved by adjusting the amplitudes and phases of excitation vector. To further enhance the spherical coverage, reactive elements are loaded into the gaps between adjacent dipoles. These reactive elements are selected from a pre-defined database using genetic algorithm-based optimization. The proposed connected dipole cluster demonstrates hemispherical coverage gains greater than 4 dB in the low band (24 to 29.5 GHz) and greater than 6 dB in the high band (37.5 to 43.5 GHz) at the 50%-tile CDF.
  • Dual-Polarized mm-Wave End-Fire Chain-Slot Antenna for Mobile Devices
    (2021-01) Moreno, Resti Montoya; Kurvinen, Joni; Ala-Laurinaho, Juha; Khripkov, Alexander; Ilvonen, Janne; van Wonterghem, Jari; Viikari, Ville
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This article describes a dual-polarized endfire antenna array for millimeter-wave (mm-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 performance. This makes colocating the sub-6 GHz and mm-wave antennas in the same, shared volume possible. Measurements indicate that a four-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.
  • Dual-polarized mm-wave endfire antenna for mobile devices
    (2020-08) Montoya Moreno, Resti; Ala-Laurinaho, Juha; Khripkov, Alexander; Ilvonen, Janne; Viikari, Ville
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This article presents a dual-polarized millimeter-wave endfire antenna array for mobile devices. The antenna array is integrated into a metal-framed mobile phone and radiates through a 20 × 3.5 mm2 window in the metal frame. The measurement results show a realized gain above 6 dBi for the frequency band of 28-33 GHz for a three-element array. Beam-steering up to ±40 is possible. The array is physically offset from the metal frame, thus minimizing the capacitive loading effect on the sub-6 GHz 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.
  • Dual-polarized Patch Antenna of Large Frequency Tuning Range at mm-Wave Frequency Bands
    (2023) Chen, Quangang; Ala-Laurinaho, Juha; Khripkov, Alexander; Ilvonen, Janne; Moreno, Resti Montoya; Viikari, Ville
     A4 Artikkeli konferenssijulkaisussa
    In this paper, we present a dual-polarized frequency-reconfigurable patch antenna working at millimeter wave frequency bands for 5G applications. A square patch is surrounded by four metallic L-shaped walls. Four ideal varactor diodes are placed between the corners of the square patch and L-shaped walls. Frequency tunability is achieved by adjusting the capacitances of the varactor diodes. Two 50-Ω probes are used to feed the square patch which can excite two orthogonal polarizations. Operating frequency can vary from 23 GHz to 45 GHz with a 10-dB return loss when the capacitance decreases from 0.05 pF to 0.005 pF. The isolation between two polarizations is better than 13 dB over the operating frequency bands. Cross-polarization level is lower than -15 dB. In addition, the quality factor of varactor diodes is studied to demonstrate its influence on antenna efficiency.
  • A Dual-Polarized Wideband Planar Multiport Mobile Antenna
    (2022) Kormilainen, Riku; Luomaniemi, Rasmus; Lehtovuori, Anu; Khripkov, Alexander; Ilvonen, Janne; Viikari, Ville
     A4 Artikkeli konferenssijulkaisussa
    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.
  • Extremely Low-Profile Tunable Multiport Handset Antenna
    (2022-02-01) Luomaniemi, Rasmus; Lehtovuori, Anu; Ilvonen, Janne; Khripkov, Alexander; Viikari, Ville
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    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.
  • Varactor-based Frequency-reconfigurable Dual-polarized mm-Wave Antenna Array for Mobile Devices
    (2023-08-01) Chen, Quangang; Laurinaho, Juha Ala; Khripkov, Alexander; Ilvonen, Janne; Moreno, Resti Montoya; Viikari, Ville
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    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 21×4.5mm2 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.
  • A Wideband Dual-polarized End-fire Antenna Array for 5G mm-Wave Smartphones
    (2024-02-01) Chen, Quangang; Laurinaho, Juha Ala; Khripkov, Alexander; Ilvonen, Janne; Moreno, Resti Montoya; Viikari, Ville
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    In this article, a dual-polarized (DP) endfire 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 (HP), and a parasitic element is included for bandwidth enhancement. A shorted-patch antenna functions as a magnetic dipole facilitating the vertical polarization (VP). 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××1.6 mm3. 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.