KR102454355B1 - Multi-band frequency reconfigurable antenna - Google Patents

Abstract

The present invention relates to a multi-band frequency reconfigurable antenna, which comprises: a micro strip patch connected to a meandered radiating structure through a wireless frequency PIN diode for achieving the frequency reconfiguration between two bands. A meandered line structure and a truncated ground plane are used so that the size of the antenna could be greatly reduced to 15.3 mm x 7.2 mm x 0.508 mm. To improve functions, the 8 x 8 multiple-input multiple-output (MIMO) is selected since it is able to arrange and configure long-edge and short-edge antennas. The system does not use an outer decoupling structure and shows the satisfactory MIMO characteristics with a wide decoupling -10 dB bandwidth of 7.4% and 4.8% respectively in a low-frequency band and a high-frequency band. The simulation result is verified by using the produced prototype and a good result is obtained. In addition, as a result of safety analysis based on electromagnetic wave absorption rate and power density in a regulated frequency band by using an actual human body model, it is checked that the safety guidelines are met. Since the mm-wave band under 6 GHz is integrated with a single small structure with a great frequency ratio and excellent MIMO performance, the proposed antenna system is proper for the 5G mobile handheld devices from now on.

Description

MULTI-BAND FREQUENCY RECONFIGURABLE ANTENNA

The present technology relates to a multi-band frequency reconfigurable antenna.

Mobile communication is commonly used in everyday life and is one of the most active areas of social development. Due to the rapid growth of data and information, modern wireless networks require high data rates with low latency. 5G cellular and local area networks (LANs) are expected to be promising solutions that can overcome the limitations of current communication technologies. The Federal Communications Commission has proposed the millimeter wave (mm wave) spectrum as operating frequencies for 5G communications, including 24, 28, 37-39 and 60 GHz.

However, the proposed spectrum has disadvantages related to propagation, which may also affect network deployment. The main 5G mid-band (3.4-3.6 GHz) has been allocated by ITU WRC-15 and has already been deployed in broadband cellular communication systems. This band can provide wider coverage with less propagation loss, but the mm-wave band for short-range indoor links is still in the development stage. In the future, major 5G bands with mm-wave bands (eg 28 GHz) are suitable for high-density 5G small cell networks in urban areas where additional capacity is important. This frequency band is also suitable for macro cells for wider area coverage.

To support large amounts of traffic at high data rates, the fastest 5G services require approximately 100 MHz bandwidth in the 5G mid-band (3.5 GHz) and 1 GHz bandwidth in the mm-wave band (28 GHz). To achieve this goal, several countries, including Korea, have granted 80 MHz and 800 MHz bandwidths per operator in the 3.5 GHz and 28 GHz bands, respectively.

Antenna with multi-band capability and large frequency ratio to handle sub-6 GHz and millimeter wave bands will play an important role in future 5G applications. Considerable research has been done to design antennas for sub-6GHz 5G communication, and several compact-sized mm wave antennas have been proposed. Most of the prior art uses separate antennas for corresponding frequency bands.

However, the space limitation of the handset for multiple single-band antennas is a difficult problem to solve, and the integration of sub-6GHz band antennas and mm wave band antennas has drawn the attention of researchers in this field. Future 5G technologies will require small-sized antennas with frequency reconfiguration that can cover the allocated radio frequency bands (eg sub-6 GHz and mm-wave bands).

The multi-band frequency reconfigurable antenna according to this embodiment is formed by disposing a plurality of single antenna elements, the single antenna element comprising: a meander patch, a microstrip patch, and a meander patch; , an RF switch for connecting the microstrip patch is formed on the first surface of the substrate, and a truncated ground plane is formed on the second surface of the substrate.

According to one aspect of this embodiment, when the RF switch is turned on, the meander patch resonates the antenna in a band less than 6 GHz, and when the RF switch is turned off, the microstrip patch resonates the antenna in the mm wave band.

According to one aspect of the present embodiment, the cut ground plane is positioned to correspond to the position of the RF switch and the microstrip patch on the second surface of the substrate.

According to one aspect of this embodiment, the RF switch is a PIN diode.

According to one aspect of the present embodiment, the plurality of single antenna elements are disposed along a long side of a substrate having a rectangular shape or disposed along a short side of a substrate having a rectangular shape.

According to one aspect of the present embodiment, the meander patch includes a rectangular pattern and a zigzag pattern having one end connected to the rectangular pattern, and the RF switch is connected to the other end of the zigzag pattern.

According to one aspect of the present embodiment, the microstrip patch has a “mountain” shape.

According to one aspect of this embodiment, the single antenna element is expressed as an equivalent circuit of a series-connected type of resistor and inductor when the RF switch is turned on, and when the RF switch is blocked, capacitors and resistors connected in parallel are connected in series with the inductor It is expressed as an equivalent circuit.

According to one aspect of this embodiment, the substrate comprises a dielectric material, wherein the relative permittivity [epsilon]r of the dielectric material is greater than two.

According to one aspect of this embodiment, the antenna is a multiple input multiple output (MIMO) antenna.

The antenna according to this embodiment provides the advantages of simple structure, reasonable gain, high radiation efficiency, and frequency reconstruction, so that it is suitable for low-frequency and high-frequency 5G applications, unlike the existing state-of-the-art technology.

1 (a) is a diagram showing configuration A (Configuration A) of the antenna according to the present embodiment, and FIG. 1 (b) is a diagram showing configuration B (Configuration B) of the antenna according to the present embodiment.
Figure 2 (a) is a view showing the outline of a single antenna element, Figure 2 (b) is a view showing the connection relationship between the meander patch, micro strip patch and PIN diode in a single antenna element, Figure 2 (c) ) is a diagram showing the cut ground structure.
3 is a diagram showing an equivalent circuit used for simulation for a PIN diode ON state and OFF state.
Figure 4 (a) is a view showing the surface current in the RF switch ON state, Figure 4 (b) is a view showing the surface current in the RF switch OFF state.
5(a) and 5(b) are diagrams illustrating simulated reflection coefficients of the antenna element in configuration A and the corresponding isolation at 3.5 and 28 GHz, and FIGS. 5(c) and 5(d) ) is a diagram showing the reflection coefficient and isolation for configuration B in the corresponding low and high frequency bands, respectively.
6 shows the simulated ECC performance in the corresponding switching state of the proposed MIMO antenna system.
7 is a diagram illustrating a DG value calculated by the antenna according to the present embodiment.
8(a) and 8(b) are diagrams illustrating three-dimensional radiation patterns at two frequencies for configuration A and configuration B;
9 (a) and (b) are diagrams showing the distribution of 10 g average SAR in the 3.5 GHz band for configurations A and B, respectively.
10 is a diagram illustrating PD distributions for two configurations at 28 GHz.
11(a) and 11(b) are diagrams illustrating spatial PD intensity along a line (15 mm) for configuration A and configuration B, respectively.

This embodiment relates to a small dual-band frequency reconfigurable antenna for a 5G portable device. The radio frequency PIN diode switch provides two operating states to the antenna system according to the present embodiment. The proposed antenna can cover up to 3.39-3.66 GHz (ON state) and 27.40-28.60 GHz (OFF state) for 5G applications. Significant size reduction and bandwidth enhancement can be achieved by using meandered radiating patches and truncated ground structures.

In order to improve the channel capacity and spectral efficiency for future 5G communication, 8 × 8 MIMO with short edge and long edge antenna layout configuration of possible rectangular substrate was adopted. From the meandered radiating patch and the truncated ground structure, satisfactory decoupling bandwidths were obtained in both configurations without the use of an external decoupling structure.

A prototype was built and performance was verified through measurement. The measured results were reasonably related to the simulation. For safety concerns, SAR and PD analyzes were performed at low and high frequencies, respectively. Both SAR and PD have been found to comply with the safety limits prescribed by the Institute of Electrical and Electronics Engineers (IEEE) and the International Commission on the Protection of Non-Ionizing Radiation (ICNIRP).

8 × 8 MIMO The design of the antenna configuration

1 is a diagram showing the structure of a proposed 8 × 8 MIMO antenna system, FIG. 1 (a) is a diagram showing configuration A (Configuration A, 10A) of the antenna according to the present embodiment, Figure 1 (b) ) is a diagram showing configuration B (Configuration B, 10B) of the antenna according to the present embodiment. 1 (a) to 1 (b), in Configuration A (Configuration A, 10A), eight antenna elements (Ant-A1 ~ Ant-A8) are symmetrical along two short edges of the substrate are arranged as In the configuration B (Configuration B, 10B), the antenna elements (Ant-B1 to Ant-B8) are arranged along the long edge of the system board. To obtain minimum insulation, the two closest antenna elements in configuration A (10A) and configuration B (10A) were spaced apart by 13.2 mm and 41.7 mm spacing, respectively. The designed eight antenna elements were printed on a Rogers RT / duroid 5880 substrate with a relative permittivity (εr = 2.2), loss tan (tanδ) of 0.0009, and a thickness of 0.508 mm. The substrate type and thickness were chosen to compensate for losses in the millimeter wave band and manufacturability. As the system board, standard dimensions of 162.6mm × 77.7mm corresponding to the Samsung Galaxy S10 5G were selected. A radiating patch including a switching element and a ground plane were printed on the front and back surfaces of the substrate, respectively.

Antenna system design and optimization was performed using a finite element method (FEM) based simulator ANSYS HFSS. Safety evaluations such as SAR and PD analysis were performed using a finite difference time domain (FDTD)-based solver-based solver Sim4LifeTM (Zurich MedTech AG, Switzerland) as a realistic human body model. The effect of radiation patterns on the head was assessed using the FDTD-based Remcom.

B. Design of single antenna element

FIG. 2(a) is a diagram showing an overview 100 of a single antenna element, and FIG. 2(b) is a meander patch 112 and a microstrip patch 114 and an RF switch 114 in a single antenna element. It is a diagram showing the connection relationship of the PIN diode, and FIG. 2( c ) is a diagram showing a truncated ground plane 120 .

2( a ) to 2 ( c ), the single antenna element 100 includes: a meander patch 110 , a microstrip patch 120 and a meander patch 110 . And, an RF switch 130 connecting the microstrip patch 120 is formed on the first surface of the substrate, and a truncated ground plane 150 is formed on the second surface of the substrate.

As illustrated in FIGS. 2 ( a ) to 2 ( c ), the meander patch 110 includes a rectangular pattern 112 and a zigzag pattern 114 with one end connected to the rectangular pattern, and the RF switch 130 . ) is connected to the other end of the zigzag pattern 114 .

As illustrated in the figure, the microlostrip patch 120 has a “mountain” shape, and the cut ground structure 120 corresponds to the zigzag pattern 114 and the RF switch 130 on the second surface of the substrate. Located.

The single antenna element 100 includes a meander patch 110 , a microstrip patch 120 , and a PIN diode switch that is an RF switch 130 connecting the meander patch 110 and the microstrip patch 120 . do. The proposed single antenna element 100 has a size of 15.3 mm × 7.2 mm × 0.508 mm. Referring to FIG. 2( c ), as illustrated, it is possible to obtain miniaturization and a wide bandwidth by using a truncated ground structure 120 . The signal to be radiated to the antenna is fed through a 50 inch microstrip feed line (not shown) with a width of 1 mm.

Utilizing the reconstruction characteristics, the microstrip patch 120 and the meander patch 110 are combined to form a single structure through the RF switch 130 . A PIN diode, RF switch 130, is placed between the two parts to change the switching state to resonate the antenna at 3.5 and 28 GHz. A DC blocking capacitor (Fig. 2(a) capacitors) is placed between the two parts to block the DC bias voltage input to the RF source. While the PIN diode is ON, the antenna operates at 3.5 GHz. On the other hand, in the OFF state, it operates in the mm-wave band of 28 GHz. The proposed MIMO antenna including 8 single antenna elements was fabricated in both configuration A and configuration B. Infineon's silicon PIN diode (BER90-22EL) is used in the proposed design due to its low insertion loss and fast switching time. In each configuration, eight PIN diodes are soldered and provided with a bias circuit on the top surface of the board. The bias voltage for the diode was provided through a jumper wire.

3 is a diagram showing an equivalent circuit used for simulation for a PIN diode ON state and OFF state. A very low resistance of 2.7Ω and an inductance of 0.4nH were considered for the PIN diode in the ON state. To get a good correlation between the measurement and simulation results, the PIN diode must provide the same resistance and inductance in the measurement. Therefore, these values were considered based on the technical data sheet of the PIN diode. 3 shows the details of the bias circuit used for the measurements, including an RF choke of 68nH, a DC bias capacitor of 8.2pF, and a bias voltage of 3.3V (applied to the DC bias terminal). In addition, when a biasing voltage of 0V was applied in the simulation of the OFF state of the PIN diode, the capacitance and reverse resistance of each diode were assigned as 0.2pF and 1.6kΩ, respectively, according to the data sheet of BER90-22EL.

As illustrated in FIG. 3( b ), the single antenna element 100 is expressed as an equivalent circuit of a series-connected type of resistor and inductor when the RF switch 130 is turned on, and connected in parallel when the RF switch 130 is blocked. Capacitors and resistors are represented as equivalent circuits in series with inductors.

The surface current distribution of the proposed antenna at the corresponding frequency is shown in FIGS. 4(a) and 4(b). 4 (a) and 4 (b) are diagrams for explaining the operating principle of the antenna. In the ON state illustrated in Fig. 4(a), the switch causes current to flow into the meander structure responsible for the 3.5 GHz resonance in the microstrip patch portion. In the OFF state, the switch limits the radiating structure to only the microstrip patch portion. Therefore, the current distribution is concentrated only on the microstrip patch, as shown in Fig. 4(b), and resonance occurs at 28 GHz.

5(a) and 5(b) are diagrams illustrating simulated reflection coefficients of the antenna element in configuration A and the corresponding isolation at 3.5 and 28 GHz, and FIGS. 5(c) and 5(d) ) is a diagram showing the reflection coefficient and isolation for configuration B in the corresponding low and high frequency bands, respectively. As can be seen in Figure 5, the proposed MIMO antenna in both configurations covers the target 5G 3.5GHz band (3.45-3.55GHz) when the switch is on, and in the OFF state, the antenna has a bandwidth of 1060MHz in the mm wave band 28GHz. works with All antenna elements in both configurations showed good impedance matching. It can be seen that in configuration A, the reflection coefficients of some antenna elements slightly deviate from 3.5 GHz due to tightness, but the bandwidth is sufficient to cover the target band.

The proposed MIMO antenna system was also evaluated for mutual coupling between various antenna elements in the two configurations. Due to the similar structure and symmetrical arrangement of the antenna elements in each configuration, only the transmission coefficients S12-S18 and S23 were evaluated. Desirable isolation is achieved even in low frequency bands across the operating bandwidth due to reduced grounding effects by the meandered radiating structure and truncated ground plane. As shown in Fig. 5(a) and Fig. 5(c), 14dB and 24.5dB separation between the nearest antenna elements were obtained in configurations A and B, respectively, in the main 5G band (3.5GHz). For configurations A and B, satisfactory isolation of 33.7 and 36.4 dB was obtained between the nearest antenna elements in the mm wave band (28 GHz), respectively. The improved insulation at 28 GHz is believed to be due to the very short wavelength of the mm wave band, and the isolation value between the closest antenna elements (Ant-A1 and -A2) at 3.5 GHz is relatively low due to the short distance between the antenna elements. Although small, the mutual coupling of the proposed MIMO antenna is limited to sub-6 GHz and mm wave bands. Still better than many 5G antennas.

To verify the performance of the proposed 5G MIMO antenna system, envelope correlation coefcient (ECC) and diversity gain (DG) were evaluated. Usable performance can be obtained when the envelope correlation coefficient (ECC) < 0.5. ECC can be calculated in several ways, including using the received signal envelope or estimating complex cross-correlations using S-parameters or radiation patterns. In this work, the simulated ECC was calculated from the radiation pattern of the antenna element based on the following equation.

[Equation 1]

(θ, φ) 및

(θ, φ)는 i, j = 1, 2, 3,…, 8 에서 i 번째 및 j 번째 안테나 요소의 방사 패턴이다.where ρij denotes ECC,

(θ, φ) and

(θ, φ) is i, j = 1, 2, 3,… , 8 are the radiation patterns of the i-th and j-th antenna elements.

6 shows the simulated ECC performance in the corresponding switching state of the proposed MIMO antenna system. The maximum ECC between the nearest antenna elements was observed at 3.5 GHz and obtained values of 0.11 and 0.02 for configuration A and configuration B, respectively, which were lower than the acceptable ECC value of 0.5. Another important parameter in MIMO performance characteristics is diversity gain (DG), which quantifies the radiation degradation of an antenna element using the signal-to-noise ratio. The corresponding DG value was calculated using Equation (2) in Equation 1 and is shown in FIG. 7 . 5 and 6, good MIMO diversity performance was observed based on the calculated ECC and DG values for all frequency bands of the two configurations.

8(a) and 8(b) show three-dimensional radiation patterns at two frequencies for configuration A and configuration B. These patterns were evaluated on real human head and hand models in the FDTD-based simulator Remcom. As illustrated in FIG. 8, the proposed MIMO antenna element in both configurations radiates outward. However, some antenna elements are in close contact with the fingers, slightly impeding the radiating action due to the power absorption of the hand tissue.

An important safety aspect associated with the electromagnetic (EM) fields of wireless end devices is the coupling between the user's head and hands. International organizations such as IEEE and ICNIRP have established safety guidelines to limit human exposure to electromagnetic waves. These guidelines are (a) SAR (Specific Absorption Rate) to prevent tissue heating at frequencies below 10 GHz and (b) Power Density (PD) to prevent tissue heating near body surfaces at frequencies above 10 GHz. Therefore, to ensure user safety, the peak 10-g average SAR should not exceed 2 W/kg. On the other hand, PD should be less than 10 W/m ² . Hand and head proximity safety analysis of the proposed MIMO antenna was performed using Sim4Life's real human model Duke. 9 (a) and (b) show the distribution of the 10 g average SAR in the 3.5 GHz band for configurations A and B, respectively. An input power of 24 dBm was set for each antenna element as it was used in the SAR calculation of the LTE smartphone. However, for mm wave frequencies, power standards have not yet been defined. As expected, the maximum peak SAR was observed in the finger closest to the antenna element in each configuration as shown in FIG. However, the safety limits of the ICNIRP guidelines were observed. The maximum 10g average SAR values for each port in both configurations are summarized in Table 1 below.

PD is currently preferred because it is difficult to determine a reasonable average volume for SAR estimation at low penetration depths at high frequencies (>10 GHz). Considering a realistic scenario, the distance between the MIMO antenna system (ground plane) and the head surface was set to about 15 mm. Figure 10 shows the PD distributions for both configurations at 28 GHz. 11(a) and 11(b) show the spatial PD intensity along the line (15 mm) for configuration A and configuration B, respectively. The corresponding maximum peak PDs were 2500 and 2000 W/m ² and decreased with distance as shown in FIGS. 11(a) and 11(b). PD exposures for the human head model were estimated for all ports and are listed in Table 1. The maximum PD value of both configurations complied with the limit prescribed at the head surface of 10 W/m ² for an input power of 24 dBm.

Although it has been described with reference to the embodiment shown in the drawings in order to help the understanding of the present invention, this is an embodiment for implementation, it is merely an example, and various modifications and equivalents from those of ordinary skill in the art It will be appreciated that other embodiments are possible. Accordingly, the true technical protection scope of the present invention should be defined by the appended claims.

100: single antenna element 110: meander patch
129: microstrip patch 130: RF switch

Claims (10)

A multi-band frequency reconfigurable antenna comprising:
A plurality of single antenna elements are arranged and formed,
The single antenna element comprises:
meander patch,
microstrip patch and
An RF switch connecting the meander patch and the micro strip patch is formed on a first surface of the substrate;
A truncated ground plane is formed on the second surface of the substrate,
The cut ground plane is
An antenna positioned to correspond to the position of the RF switch and the microstrip patch on the second side of the substrate.
According to claim 1,
When the RF switch is turned on,
the meander patch resonates the antenna in a band below 6 GHz;
When the RF switch is blocked,
An antenna in which the microstrip patch resonates the antenna in the mm wave band. delete According to claim 1,
The RF switch is a PIN diode antenna. According to claim 1,
The plurality of single antenna elements are
or disposed along the long side of the substrate having a rectangular shape,
An antenna disposed along a short side of the substrate having a rectangular substrate. According to claim 1,
The meander patch is
rectangular pattern and
It includes a zigzag pattern having one end connected to the rectangular pattern,
The RF switch is an antenna connected to the other end of the zigzag pattern. According to claim 1,
The micro strip patch,
Antenna with a “mountain” shape. According to claim 1,
The single antenna element comprises:
When the RF switch is turned on, it is expressed as an equivalent circuit in the form of a series connection of a resistor and an inductor,
Antenna expressed as an equivalent circuit in which capacitors and resistors connected in parallel are connected in series with an inductor when the RF switch is cut off. According to claim 1,
the substrate comprises a dielectric material;
the relative permittivity (εr) of the dielectric material is greater than 2,
The thickness of the substrate is less than 1 mm antenna. According to claim 1,
The antenna is a multiple input multiple output (MIMO) antenna.

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