$4\times8$ Patch Array-Fed FR4-Based Transmit Array Antennas for Affordable and Reliable 5G Beam Steering

Yongyeon Kim,Jungsuek Oh,Hogyeom Kim,Inseop Yoon

doi:10.1109/access.2019.2926379

Yongyeon Kim, Jungsuek Oh + Show 2 more

Open Access

https://doi.org/10.1109/access.2019.2926379

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Abstract

This paper presents a novel method of designing affordable 28-GHz transmit array antennas utilizing FR4 substrates, which are low-cost but lossy. It is demonstrated that low insertion loss can be achieved by employing appropriate combinations of spatial filter unit cells, where each unit cell is selected to minimize the loss factors defined by lossy spatial filter modeling. The loss factor with inter-layer couplings was found to be more variable than that without inter-layer couplings, although inter-layer couplings have previously been utilized to increase the tunable range of the phase shift. Therefore, the number of metal layers in the low-pass spatial filter more affected by the inter-layer coupling is selected to be less than the number of metal layers used in the bandpass spatial filter for a given thickness in the proposed method. In addition, a novel transmits array in which some of the unit cells are sinusoidally arranged is described. This can achieve up to 1.6-dB gain enhancement at some steered angles compared with the conventional design. To simulate transmit arrays rapidly, an effective simple medium structure representing a transmit array is presented. Finally, the measured results confirm the effectiveness of the proposed design approaches for affordable transmit array antennas. Only a small difference of 0.8 dB between the simulated and measured results confirms the successful manipulation of the lossy characteristic of FR4.

Highlights

Researchers have been actively studying antenna solutions for new-type 5G equipment such as mmWave repeaters and bases stations [1], [2]–[7], and one of the recent 5G equipment receiving much attention from the industry is 5G outdoor customer premise equipment where a total of 64 (8 × 8) antenna elements is used and each antenna array has 32 (4 × 8) elements for 2 × 2 MIMO [8]
This paper presents novel design techniques employing lossy spatial filter modeling that enable affordable fabrication of transmit arrays made of lossy FR4 substrates
The dielectric loss at a metal layer is interpreted as a parasitic resistance in a capacitance or an inductance in the equivalent circuit of the spatial filter

Summary

INTRODUCTION

Researchers have been actively studying antenna solutions for new-type 5G equipment such as mmWave repeaters and bases stations [1], [2]–[7], and one of the recent 5G equipment receiving much attention from the industry is 5G outdoor customer premise equipment where a total of 64 (8 × 8) antenna elements is used and each antenna array has 32 (4 × 8) elements for 2 × 2 MIMO [8]. The requisite values of the capacitance and inductance for a specific resonant frequency can be obtained using the aforementioned FSS approximation; accurate spatial filter responses can be realized, even for higher orders This approximation method allows for investigation of the relationships among the parameters of the equivalent circuits, such as the inductance and capacitance, and design parameters such as the dielectric constant, periodicity, and separation between adjacent unit cells. In the conventional low-loss FSS unit cell, while the equivalent series LC circuit of Fig. 4 (a) includes a series inductor as well as a series capacitor, the series inductor can be ignored by considering the shape of the patches having a wide lateral dimension dominantly exciting capacitive in-plane coupling [24].

R21C12

CONCLUSION