KR100402760B1 - Microstrip antenna using piezoelectric element - Google Patents

Abstract

The present invention relates to a microstrip antenna using a piezoelectric element, and more particularly, a ground plate 100 is formed on one side thereof, and a lower substrate 110 having a predetermined thickness; and a patch 120 on one side thereof. An upper substrate 130 having a predetermined thickness; And for frequency adjustment, the ground plate 100 and the patch 120 is formed in a position where the ground plate 100 and the patch 120 so as to adjust the interval, the mechanical deformation is applied to the external electric field The piezoelectric element 140 is configured to include, and thus, there is an advantage in that the frequency band can be easily adjusted and moved in real time without applying physical deformation to the antenna.

Description

Microstrip antenna using piezoelectric element {MICROSTRIP ANTENNA USING PIEZOELECTRIC ELEMENT}

The present invention relates to a microstrip antenna using a piezoelectric element, and more particularly, by forming a piezoelectric element that becomes mechanically deformed on a substrate by applying an external electric field without applying a physical deformation to the antenna, and applying an external electric field to generate a frequency in real time. It is about a microstrip antenna using a piezoelectric element that can easily adjust and move the band.

In general, an antenna is used to transmit and receive a signal of electric field strength required by subscribers within a cell radius in a cellular mobile communication base station, and is used as an air interface means used to transmit and receive signals to and from a base station. It is becoming. In addition, radio shade areas such as underground parking lots, subways, and offices in high-rise buildings are used for air interfaces of repeaters.

As described above, a dipole antenna, a yagi antenna, and a microstrip antenna are mainly used in mobile communication or wireless communication.

The dipole antenna is a half-wavelength resonant antenna having a donut-type omnidirectional radiation characteristic and is mainly used as a subscriber antenna of cellular communication and a service antenna of a small repeater.

In addition, the Yagi antenna is an example of improving directivity by overlapping a plurality of dipole antennas in a longitudinal direction, and is mainly used for a zonal antenna of a small repeater.

The microstrip antenna includes a personal mobile communication service including a cellular phone and a personal communication service (PCS), a wireless local looped service, a future public land mobile telecommunication system, and satellite communication. It is used in the wireless communication is mainly used for transmitting and receiving signals between the base station and the user terminal.

1 (A) is a diagram showing the structure of a conventional microstrip patch antenna.

In FIG. 1, reference numeral 1 denotes a dielectric substrate made of a dielectric such as Tefron, Rexolite, or Polytetrafluoroethylene (PTFE). (2) is provided, and a ground plate (3) made of a conductive metal is provided on the lower surface of the dielectric substrate (1) facing the patch (2).

In addition, the patch 2 is provided with a feed point 21 for supplying predetermined power to one side thereof and inputting a predetermined reception signal through impedance matching, and the feed point 21 is provided. And the patch 2 are electrically coupled via a feed line 22.

In the above configuration, when a predetermined power is applied to the feed point 21, the Quasi-TEM mode proceeds in the z direction, where the length L of the patch 2 is λ0 / 2. A leakage electric field as shown in 2 (B) is generated. At this time, the leakage electric fields are mutually offset from each other having a direction from the patch 2 to the ground plate 3 and a direction from the ground plate 3 to the patch 2, and the horizontal components are in phase with each other. As shown in Fig. 1C, the two slots 23 and 24 are separated from each other by a predetermined distance, L.

Then, a high frequency signal is applied from the outside by the radiated electric field between the slots 23 and 24.

That is, according to the conventional microstrip patch antenna described above, the antenna can be realized on a dielectric substrate having a predetermined size, so that the antenna can be installed on a moving body or the like.

The microstrip patch antenna originally has an impedance bandwidth of about 1 to 2%, and many methods for increasing the bandwidth have been proposed. Such methods primarily use a method of placing a parasitic element in a stack on the same plane or another layer as the patch or modifying the patch shape.

U.S. Pat.No. 5,565,875 and U.S. Pat.No. 5,680,144 specify antennas that increase bandwidth by modifying the shape of the silver patches into loops or C-shapes and stacking parasitics. There is a disadvantage in that the thickness is very high and it is very difficult to use practically. For this reason, it is difficult to embed in general personal mobile communication repeater antennas and wireless communication equipments, and as the volume increases, it is difficult to attach to corridors or walls of subways, underground buildings, and radio shade areas.

That is, the conventional microstrip antenna has a disadvantage in that only a fixed frequency range is allowed according to the deformation and manufacture of the appearance.

The present invention has been made to solve the above problems, an object of the present invention is to form a piezoelectric element that is mechanically deformed by applying an external electric field to the antenna without applying a physical deformation to the antenna to apply an external electric field in real time, The present invention provides a microstrip antenna using a piezoelectric element that can easily adjust and move a frequency band.

1 (A) to 1 (C) are perspective views showing a conventional microstrip antenna

Figure 2 is an exploded perspective view showing a microstrip antenna using a piezoelectric element according to an embodiment of the present invention

3 is a cross-sectional view illustrating a microstrip antenna using a piezoelectric element according to an embodiment of the present invention.

4 is a diagram illustrating a system for measuring characteristics of a microstrip antenna using piezoelectric elements according to an embodiment of the present invention.

5 is a graph showing a change in frequency with respect to the DC bias of the microstrip antenna using a piezoelectric element according to an embodiment of the present invention

6 is a graph showing a change in frequency with respect to the AC bias of the microstrip antenna using a piezoelectric element according to an embodiment of the present invention

Figure 7 is an exploded perspective view showing a microstrip antenna using a piezoelectric element according to another embodiment of the present invention

8 is a cross-sectional view illustrating a microstrip antenna using a piezoelectric element according to another exemplary embodiment of the present invention.

9 is a diagram illustrating a system for measuring characteristics of a microstrip antenna using piezoelectric elements according to another embodiment of the present invention.

10 is a graph showing a change in frequency with respect to the DC bias of the microstrip antenna using a piezoelectric element according to another embodiment of the present invention

Explanation of symbols on the main parts of the drawings

100: ground plate 110: lower substrate

120: patch 130: upper substrate

140: piezoelectric element 150: air layer

160: voltage source and function generator (LG FG8002, Fluke 5100D; 170)

170: vector network analyzer (HP 8722D)

In order to achieve the above object, the present invention is a ground plate is formed on one side, the lower substrate having a predetermined thickness; A patch formed on one side thereof, the upper substrate having a predetermined thickness; And a piezoelectric element formed at a position where the ground plate and the patch are opposed to each other so as to adjust the gap between the ground plate and the patch and applying an external electric field to adjust the frequency.

In this case, it is preferable to form an air layer spaced apart at regular intervals between the patch and the ground plate.

In addition, the air layer preferably has a thickness of 0.4 to 0.6 mm.

In addition, the upper substrate and the lower substrate has a thickness of 4 ~ 6mm, preferably made of a rectangular shape.

In addition, the patch is a size of 25 × 20 ~ 35 × 30 mm, it is preferable that the feed line is electrically connected to one side.

In addition, the piezoelectric element is preferably made of Pb (Zr, Ti) O ₃ .

In addition, the piezoelectric element has a diameter of 20 to 30 mm and a thickness of 0.18 to 0.38 mm, preferably in the shape of a disc.

And, in the microstrip antenna comprising a substrate formed between the patch and the ground plate, the substrate is a patch is formed on one side, the ground plate is formed on the other side, the ground plate and the patch for frequency adjustment It is characterized in that the piezoelectric element substrate is mechanically deformed when an external electric field is applied to adjust the spacing of the.

At this time, the piezoelectric element substrate is preferably made of LiNbO ₃ .

In addition, the piezoelectric element substrate has a diameter of 70 to 80 mm and a thickness of 0.4 to 0.6 mm, and preferably has a disc shape.

In addition, the patch has a size of 20 × 19 ~ 20 × 29 mm, preferably made of a rectangular shape.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. This embodiment is not intended to limit the scope of the invention, but is presented by way of example only.

Figure 2 is an exploded perspective view showing a microstrip antenna using a piezoelectric element according to an embodiment of the present invention, Figure 3 is a combined cross-sectional view showing a microstrip antenna using a piezoelectric element according to an embodiment of the present invention, Microstrip antenna using a piezoelectric element according to an embodiment of the present invention is the ground plate 100 is formed on the upper surface, the lower substrate 110 having a predetermined thickness; Patch 120 is formed on the bottom surface, the upper substrate 130 having a predetermined thickness; And a plurality of piezoelectric elements 140 installed between the upper substrate 130 and the lower substrate 110 to be mechanically deformed by applying an external electric field.

In this case, the patch 120 and the ground plate 100 is made of a thin copper plate, the air layer 150 is formed by being spaced apart at regular intervals between the patch 120 and the ground plate 100.

Herein, the air layer preferably has a thickness of 0.4 to 0.6 mm.

The patch 120 has a size of 25 × 20 to 35 × 30 mm, and a feed line (not shown) is electrically coupled to one side thereof.

The upper substrate 130 and the lower substrate 110 have a thickness of 4 to 6 mm and have a rectangular shape.

The piezoelectric element 140 is preferably made of Pb (Zr, Ti) O ₃ (hereinafter referred to as PZT).

In addition, the piezoelectric element PZT 140 has a diameter of 20 to 30 mm and a thickness of 0.18 to 0.38 mm, and an electrode 145 is formed on the upper and lower portions thereof, and preferably has a disc shape.

A diagram illustrating a system for measuring characteristics of a microstrip antenna using a piezoelectric element according to an embodiment of the present invention as shown in FIG. 4, as shown in FIG. 4, a voltage source and a function generator (Fluke 5100D, LG FG8002; 160). It was measured by a vector network analyzer (HP 8722D; 170) applying DC and AC bias.

That is, the vector network analyzer HP 8722D; 170 is connected to the piezoelectric element PZT 140 from the voltage source and the output port 161 of the function generator 160, and is electrically connected to the patch 120. By connecting DC and AC bias to the piezoelectric element PZT 140 by connecting to the input port 171, the movement of the frequency with respect to the external electric field is measured.

FIG. 5 is a graph illustrating a change in frequency with respect to the DC bias of a microstrip antenna using a piezoelectric element according to an embodiment of the present invention, in which resonance characteristics of the resonance frequency are shifted with respect to DC or AC bias. Is defined as the difference in frequency between the resonant frequency in a particular electric field and the resonant frequency in a zero electric field. In other words, Is defined as the difference in frequency between the maximum resonant frequency and the minimum resonant frequency at a specific AC bias voltage. Here, the arrow indicates the increase / decrease direction of the applied electric field. This graph shows the "butterfly curve". The piezoelectric element PZT 140 exhibits hysteresis because it is a ferroelectric material. This phenomenon arises from the hysteresis effect of the piezoelectric element (PZT) plate. External electric field Is 1.90 MHz-cm / Hz.

At this time, from the piezoelectric equation, the relationship between strain and electric field E is as follows.

. -------------------------- (Equation 1)

Where dt is a piezoelectric constant.

That is, the resonant frequency of the patch antenna was calculated as shown in the following equation (2) based on the approximation value.

-------- (Equation 2)

here, , , Wow Are the length, thickness, relative dielectric constant and resonant frequencies of the piezoelectric element, respectively. The theoretical equation is in good agreement with the experimental results.

In this graph, the resonant frequency of the antenna decreases from -12 [kV / cm] to -2 [kV / cm] and then continuously increases from -2 [kV / cm] to 12 [kV / cm]. Can be seen. In addition, it can be seen that the resonance frequency of the antenna is continuously increased from 12 [kV / cm] to 2 [kV / cm] and from 2 [kV / cm] to -12 [kV / cm].

That is, it can be seen that the lowest frequency when ± 2 [kV / cm] is applied. This graph is similar to the strain curve of a general piezoelectric body. The voltage difference between the two peaks is generated by the hysteresis loop of the ferroelectric, and it can be seen that the frequency change is the largest in the electrostatic field.

6 is a graph illustrating a change in frequency of an AC bias electric field of a microstrip antenna using a piezoelectric element according to an embodiment of the present invention. Shows 6.12 MHz-cm / ㎸. Is 3 times larger than For external electric field Represents a linear relationship.

That is, the piezoelectric element PZT 140 does not show hysteresis when the AC bias is greater than an arbitrary polarity.

7 is an exploded perspective view showing a microstrip antenna using a piezoelectric element according to another embodiment of the present invention, Figure 8 is a cross-sectional view showing a microstrip antenna using a piezoelectric element according to another embodiment of the present invention, Microstrip antenna using a piezoelectric element according to another embodiment of the present invention has a predetermined thickness, the piezoelectric element substrate 200 is a mechanical deformation when an external electric field is applied; A patch 210 formed on an upper surface of the piezoelectric element substrate 200; And a ground plate 220 formed on the bottom surface of the piezoelectric element substrate 200.

At this time, the piezoelectric element substrate 200 is preferably made of LiNbO ₃ .

In addition, the piezoelectric element substrate 200 preferably has a diameter of 70 to 80 mm and a thickness of 0.4 mm to 0.6 mm, and has a disc shape.

In addition, the patch 210 has a size of 20 × 19 ~ 30 × 29 mm, a feed line (not shown) is electrically coupled to one side thereof, preferably made of a rectangular shape.

In addition, the piezoelectric element substrate (LiNbO ₃ ; 200) was washed with an ultrasonic cleaner using acetone for 10 minutes to remove organic substances from the surface. It was then washed with metal alcohol and deionized water for 10 minutes. After it was dried using Nitrogen Gas, a silver electrode was deposited on the surface using hot steam.

FIG. 9 is a diagram illustrating a characteristic measurement system for measuring characteristics of a microstrip antenna using piezoelectric elements according to another exemplary embodiment of the present invention. The voltage source and the function generator (Fluke 5100D, LG FG8002; 160) and a vector network analyzer (HP 8722D; 170) with DC or AC bias applied.

That is, the voltage source and the output port 161 of the function generator 160 and the vector network analyzer (HP 8722D; 170) from the bias (Bias-T 5530A, Picosecond; 230) mounted on the piezoelectric element substrate (LiNbO ₃ ; 200). By applying a DC bias to the microstrip antenna by connecting to the input port 171 of), the movement of the frequency with respect to the external electric field is measured. In this case, the bias tee (Bias-T 5530A, Picosecond; 230) is electrically connected to the patch 210 formed on the top surface of the piezoelectric element substrate (LiNbO ₃ ; 200), which is not shown.

On the other hand, the AC bias could not be supplied due to the limitation of bias (Tias-T 5530A, Picosecond; 230).

FIG. 5 is a graph illustrating a change in frequency with respect to a DC bias electric field of a microstrip antenna using a piezoelectric element according to an exemplary embodiment of the present invention, in which a shift characteristic of a resonance frequency with respect to a DC bias is observed.

The resonance frequency of the microstrip patch antenna using the piezoelectric element substrate (LiNbO ₃ ; 200) is 5.67 GHz. Since the forced magnetic field of the piezoelectric element substrate (LiNbO ₃ ; 200) is extremely high, its piezoelectric direction does not change in the range of 5 mA / cm.

As a result, The relationship of is linear. For external electric field Is 5.57 MHz-cm / Hz. For AC bias Cannot be measured because of the bias-tee limit.

Thus, the present invention shows that the resonant frequency of the microstrip patch antenna can be controlled by an external electric field when used as a piezoelectric element substrate.

That is, the resonant frequency with respect to the external electric field is 1.90 MHz-cm / kV with DC bias and 6.12 MHz-cm / kW with AC bias in the case of the microstrip antenna using the piezoelectric element (PZT; 100).

In addition, in the case of the microstrip antenna using the piezoelectric element substrate (LiNbO ₃ ; 200), it is 5.57 MHz-cm / kV under DC bias. Although these results show that the frequency shifts are relatively small, they will be larger when we use piezoelectric elements with large electromagnetic components, and are suitable for use as circuit boards for microstrip antennas.

The present invention is not limited to the above-described embodiment, and it will be apparent that many modifications are possible by those skilled in the art within the technical spirit of the present invention.

Therefore, as described above, the present invention provides a piezoelectric element that is mechanically deformed by applying an external electric field without applying a physical deformation to the antenna, thereby applying an external electric field, thereby easily adjusting and moving a frequency band in real time. There is this.

Claims (11)

A ground plate 100 formed on one side thereof, the lower substrate 110 having a predetermined thickness; Patch 120 is formed on one side, the upper substrate 130 having a predetermined thickness; And In order to adjust the frequency, the ground plate 100 and the patch 120 are formed in a position opposite to each other so that the gap between the ground plate 100 and the patch 120 can be adjusted. Element 140; Microstrip antenna using a piezoelectric element, characterized in that comprises a. The method of claim 1, Microstrip antenna using a piezoelectric element, characterized in that to form an air layer 150 is spaced apart at regular intervals between the patch 120 and the ground plate (100). The method of claim 2, The air layer 150 is a microstrip antenna using a piezoelectric element, characterized in that having a thickness of 0.4 ~ 0.6㎜. The method of claim 1, The upper substrate 130 and the lower substrate 110 has a thickness of 4 ~ 6mm, the microstrip antenna using a piezoelectric element, characterized in that formed in a rectangular shape. The method of claim 1, The patch 120 has a size of 25 × 20 to 35 × 30 mm, and a microstrip antenna using a piezoelectric element, characterized in that a feed line is electrically connected to one side thereof. The method of claim 1, The piezoelectric element 140 is a microstrip antenna using a piezoelectric element, characterized in that consisting of Pb (Zr, Ti) O ₃ . The method of claim 1, The piezoelectric element 140 has a diameter of 20 to 30 mm and a thickness of 0.18 to 0.38 mm, and has a disc shape, and has a microstrip antenna using a piezoelectric element. In the microstrip antenna comprising a substrate formed between the patch and the ground plate, The substrate has a patch 210 formed on one side thereof, a ground plate 220 formed on the other side thereof, and an outer side of the substrate to adjust a gap between the ground plate 100 and the patch 120 for frequency adjustment. Microstrip antenna using a piezoelectric element, characterized in that the piezoelectric element substrate 200 is mechanical deformation when an electric field is applied. The method of claim 8, The piezoelectric element substrate 200 is a microstrip antenna using a piezoelectric element, characterized in that consisting of LiNbO ₃ . The method of claim 8, The piezoelectric element substrate 200 has a diameter of 70 to 80 mm and a thickness of 0.4 to 0.6 mm, and has a disc shape, and has a piezoelectric element. The method of claim 8, The patch 210 has a size of 20 × 19 ~ 20 × 29 mm, and a microstrip antenna using a piezoelectric element, characterized in that formed in a rectangular shape.