KR101974546B1 - Filter integrated cavity back antenna - Google Patents

Abstract

Provided is a filter built-in type cavity-back antenna, which includes: a dielectric substrate on a board; a patch formed on an upper surface of the dielectric substrate; a cavity body attached to a lower surface of the dielectric substrate; a coaxial filter connected to the lower surface of the dielectric substrate; a dielectric sheet attaching the cavity body on the dielectric substrate between the dielectric substrate and the cavity body; and a coupling feed unit attached to the lower surface of the dielectric sheet. Accordingly, the cavity-back antenna can reduce the size of a wireless frequency transceiving system into which the filter built-in type cavity back antenna is applied.

Description

{FILTER INTEGRATED CAVITY BACK ANTENNA}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a cavity-backed antenna with a built-in filter, and more particularly to a cavity-backed cavity antenna with a filter capable of downsizing the size of a radio frequency transmission and reception system.

Harmonics always occur at resonance through the antenna. Harmonics appear at frequencies that are multiples of the fundamental resonant frequency.

When a signal of a small size is transmitted from an antenna, the signal transmitted through the harmonic frequency band is weak and has little effect on the frequency band. On the other hand, when transmitting a large-sized signal from the antenna, the signal transmitted through the harmonic frequency band affects the corresponding frequency band.

Therefore, it is necessary to use a filter to cut off the harmonic frequency band when transmitting an antenna of a large size.

On the other hand, most radio frequency transmission / reception systems are configured such that the antenna and the filter are independently designed and connected through a connection means such as a coaxial cable. Thus, there is a problem that the size of the system is large and the configuration of the system is complicated.

Techniques as a background of the present invention are listed in the following patent documents.

KR 10-2015-0021679 A KR 10-1843305 B1

The present invention provides a cavity-backed antenna with a built-in filter that can be miniaturized in size.

A cavity-backed antenna with a built-in filter according to an embodiment of the present invention includes: a cavity body; And a coaxial filter embedded in the cavity body.

The cavity body may have a patch disposed thereon and the patch may be powered through the coaxial filter to operate.

A cavity-back antenna according to an embodiment of the present invention includes: a plate-shaped dielectric substrate; A patch formed on an upper surface of the dielectric substrate; A cavity body attached to the lower surface of the dielectric substrate; And a coaxial filter installed to pass through the cavity body and connected to the lower surface of the dielectric substrate.

And a dielectric foam filled in a cavity formed concavely on an upper surface of the cavity body, wherein the coaxial filter can be installed to penetrate the dielectric foam.

A dielectric sheet for attaching the cavity body to the dielectric substrate between the dielectric substrate and the cavity body; And a coupling feeding part attached to a lower surface of the dielectric sheet, wherein the coaxial filter can be connected to the lower surface of the dielectric substrate through the coupling feeding part and the dielectric sheet.

The lower surface of the coaxial filter and the lower surface of the cavity body may be on the same plane.

The impedance of the input terminal and the output terminal of the coaxial filter may be different to enable impedance matching.

The patch may have an impedance of 100 OMEGA, and the coaxial filter may have an input impedance of 50 OMEGA and an output impedance of 100 OMEGA.

The coaxial filter includes a hollow casing having a conductivity; And a core coaxially disposed on the shell and applying a signal to the patch and blocking a harmonic frequency band of the signal, wherein the shell and the core may have the same length in the vertical direction.

And the lower surface of the core body and the lower surface of the cavity body may be on the same plane.

The coaxial filter may include a cap having a dielectric constant and disposed between the shell and the core and connecting at least a part of the core to at least a part of the shell.

The covering portion may include a Teflon material.

The core has a first part having an impedance of 50?; A second part protruding upward from an upper surface of the first part and having an impedance of 100?; And a ring-shaped third part protruding from a plurality of positions of the second part, wherein the first part is provided with a coaxial cable having an impedance of 50 ?, and the second part is connected to the lower surface of the dielectric substrate have.

The cover may connect the outer circumferential surface of the third part and the inner surface of the shell, and a space may be provided between the shell and the core excluding the part where the cover is disposed.

The length of the first part in the vertical direction is shorter than that of the second part, and the diameter of the first part may be larger.

According to the embodiment of the present invention, by incorporating the coaxial filter in the cavity body of the cavity back antenna, the size of the radio frequency transmission / reception system can be reduced and the complexity can be solved.

In addition, since the coaxial filter built in the cavity body also plays the role of an impedance matching circuit, it is not necessary to connect a separate impedance converter or matching network to the cavity back antenna, so that the size of the system can be further reduced, Can be further simplified.

1 is a structural view of a filter-embedded cavity-back antenna according to an embodiment of the present invention.
2 is a structural view of a filter according to an embodiment of the present invention.
3 is a structural view of a cavity-back antenna according to a comparative example of the present invention.
4 is a graph illustrating antenna characteristics according to an embodiment of the present invention and a comparative example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described below, but may be embodied in various forms. It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. BRIEF DESCRIPTION OF THE DRAWINGS The drawings may be exaggerated for purposes of describing embodiments of the present invention, wherein like reference numerals refer to like elements throughout.

The cavity-back antenna according to the embodiment of the present invention (also referred to as a filter-embedded cavity-back antenna) may be used in a radio frequency transmission / reception system.

1 is a structural view of a filter-embedded cavity-back antenna according to an embodiment of the present invention. 1 (a) is an exploded perspective view of the filter-integrated cavity back antenna, and FIG. 1 (b) is a sectional view of the filter-integrated cavity back antenna. 2 is a structural view of a filter according to an embodiment of the present invention. 2 (a) is a cross-sectional view of the filter, and FIG. 2 (b) is a cross-sectional view of the filter.

Referring to FIG. 1, a filter-embedded cavity back antenna according to an embodiment of the present invention includes a cavity body 300 for providing a cavity, and a coaxial filter 600 embedded in the cavity body 300. At this time, the patch body 120 is disposed on the upper part of the cavity body 300, and the patch 120 is coupled through the coaxial filter 600 to operate as a patch antenna.

Alternatively, the filter-embedded cavity back antenna includes a plate-like dielectric substrate 110, a patch 120 formed on the upper surface of the dielectric substrate 110, a cavity body 300 attached to the lower surface of the dielectric substrate 110, And a coaxial filter 600 installed to penetrate through the dielectric substrate 300 and connected to the lower surface of the dielectric substrate.

The filter-embedded cavity back antenna includes a dielectric foam 400 filled in a cavity formed in a concave shape on an upper surface of the cavity body 300, a dielectric substrate 400 disposed between the dielectric substrate 110 and the cavity body 300, A dielectric sheet 200 for attaching the cavity body 300 to the dielectric sheet 200, and a coupling feeding part 500 attached to the lower surface of the dielectric sheet 200.

At this time, the coaxial filter 600 may be installed to penetrate the dielectric foam 400. The coaxial filter 600 may be electrically connected to the lower surface of the dielectric substrate 110 through the coupling feeding part 500 and the dielectric sheet 200.

A patch 120 formed on the dielectric substrate 110 and the dielectric substrate 110 may form a microstrip patch antenna 100.

The dielectric substrate 110 may be an RF-30 substrate having a dielectric constant of 3 and a thickness of 1.27 mm. The dielectric substrate 110 may have a rectangular plate shape. For the formation of the patch 120, the dielectric substrate 110 may have a predetermined area. The patch 120 may be formed at the center of the upper surface of the dielectric substrate 120.

The patch 120 may be formed on the upper surface of the dielectric substrate 110. The patch 120 may be formed in a rectangular shape. The operating frequency can be adjusted to the target band by adjusting the length and width of the patch 120. In order to increase the bandwidth of the frequency, the patch 120 may be fed through the coupling energy by the coupling feeding part 500. The patch 120 may be designed to have an impedance of 75? Or 100?. Preferably, in the embodiment of the present invention, the patch 120 may be designed to have an impedance of 100 OMEGA.

The dielectric sheet 200 may include a bonding sheet having a dielectric constant of 3.206. The dielectric sheet 200 may be formed in the same shape and size as the lower surface of the dielectric substrate 110. The upper surface of the dielectric sheet 200 may be attached to the lower surface of the dielectric substrate 110. The cavity body 300 can be attached to the lower surface of the dielectric sheet 200. That is, the dielectric sheet 200 serves as a bonding layer for connecting the microstrip patch antenna 100 and the cavity body 300.

The cavity body 300 may be formed in a rectangular parallelepiped shape. The cavity body 300 may be attached to the edge of the lower surface of the dielectric sheet 200. That is, the cavity body 300 can be attached to the lower surface of the dielectric substrate 110 by the dielectric sheet 200.

The cavity body 300 may be a metal conductor. The cavity body 300 may be sized to meet a minimum size for the required antenna characteristics.

The cavity body 300 may have a concave cavity formed on the upper surface thereof. The cavity may have a rectangular parallelepiped shape in which the four corners extending in the vertical direction are rounded. The cavity is used to improve the frequency bandwidth, and the frequency bandwidth can be adjusted by adjusting the size and shape of the cavity.

The coupling feeding part 500 may be attached to a predetermined position of the lower surface of the dielectric sheet 200. The coupling feeding part 500 may be located in the cavity. Coupling feed portion 500 may be a metal post capable of feeding coupling to patch 120. The input impedance of the patch 120 may vary depending on the position of the coupling feeding part 500. [ The coupling feeding part 500 may be formed at a position where the input impedance of the patch 120 is 75? Or 100?. Preferably, the coupling feeding part 500 may be formed at a position such that the input impedance of the patch 120 is 100 OMEGA.

The cavity may be filled with a dielectric foam 400. That is, the dielectric foam 400 is filled in the remaining space other than the space where the coaxial filter 600 and the coupling feeding part 500 are installed, so that there is no empty space in the cavity. The frequency bandwidth can be adjusted according to the dielectric constant of the dielectric foam 400.

The coaxial filter 600 may be installed to vertically penetrate the cavity body 300 and the dielectric foam 400. That is, the coaxial filter 600 is embedded in the cavity body 300 and can be protected by the dielectric foam 400. Here, the coaxial filter 600 means a filter having an internal structure in a coaxial shape.

The coaxial filter 600 can be brought into contact with the coupling feeding part 500 at its upper end (output end). The coaxial filter 600 can be electrically connected to the lower surface of the dielectric substrate 1100 through the coupling feeding part 500. The lower ends (input ends) of the coaxial filter 600 and the lower surfaces of the cavity body 300 are formed on the same plane Coaxial filter 600 may apply a signal to patch 120 and block unwanted harmonic frequency bands in the signal.

On the other hand, reflection loss due to signal reflection may occur in the connection between the RF elements. Therefore, it is important to prevent signal reflection. To do this, the input and output impedances of each device must be matched to the reference impedance. Therefore, a matching network for impedance matching is needed inside the RF device.

However, according to the embodiment of the present invention, the impedance of the input terminal and the impedance of the output terminal may be different from each other so that impedance matching can be performed. Therefore, a separate matching network is not required, and the impedance of the input terminal of the coaxial filter 600 may be matched to the reference impedance. Here, the reference impedance may be 50?.

For example, the coaxial filter 600 has the same value as the impedance value of the coaxial cable (not shown) (for example, 50?), Which will be described later, and has the same value as the impedance value of the patch 120 The input and output stages can be designed. Thus, since there is no need for a separate matching network, the connection structure of the entire system can be simplified, and the weight and size can be reduced.

In addition, the filter provided in the conventional radio frequency transmitting and receiving system is larger than ordinary RF elements. Therefore, as in the embodiment of the present invention, the structure in which the coaxial filter 600 is embedded in the cavity body 300 is a filter-embedded type antenna in which a filter and an antenna are combined into one module. Therefore, There is an advantage to be able to do.

Hereinafter, a coaxial filter 600 according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG.

The coaxial filter 600 includes a hollow shell 620 having a conductivity, a core 610 that is coaxially disposed on the shell 620 and that applies a signal to the patch 120 and blocks harmonic frequency bands in the signal. And an envelope 630 having a dielectric constant and disposed between the envelope 620 and the core 610 and connecting at least a portion of the core 610 to at least a portion of the envelope 620.

The sheath 620 and the core 610 may be made of metal. The sheath 620 and the core 610 may have the same length in the vertical direction. The lower surface of the outer skin 620 and the lower surface of the core body 610 and the lower surface of the cavity body 300 may be located on the same plane. The envelope 620 serves as a shield, and the core 610 can serve as a filter. On the other hand, the outer shell 620 may be referred to as an outer conductor, and the core body 610 may be referred to as an inner conductor. The envelope 620 may be cylindrical.

The covering portion 630 may include a Teflon material having a dielectric constant of 2.1 and may be formed in a ring shape. The covering portion 630 serves to eliminate the separation between the sheath 620 and the core 610 and structurally interconnects the sheath 620 and the core 610 such that the coaxial filter 600 is resistant to vibration .

The core 610 may have different impedances at the upper end (output end) and the lower end (input end). The core 610 may have a structure in which an output terminal of a high impedance (100?) And an input terminal of a low impedance (50?) Are cascade-connected. Thus, the core 610 can have an input impedance of 50 OMEGA and an output impedance of 100 OMEGA.

The core body 610 includes a first part 611 of a round bar shape having an impedance of 50?, A second part 612 of a round bar shape protruding upward from the upper surface of the first part 611 and having an impedance of 100? And a third part 613 and 614 in the form of a ring projecting from a plurality of positions of the part 612. A plurality of third parts 613 and 614 may be formed, for example, two. The third part 613, 614 may include a lower protruding part 613 and an upper protruding part 614.

The first part 611 is the input of the coaxial filter 600 and the upper part of the second part 612 is the output of the coaxial filter 600. The length of the first part 611 in the vertical direction is shorter than that of the second part 612, and the diameter of the first part 611 may be larger. The covering portion 630 may be provided to connect the outer circumferential surface of the lower protruding part 613 and the upper protruding part 614 to the inner surface of the outer cover 620. At this time, a space portion 640 may be provided between the sheath 620 and the core 610 except the portion where the covering portion 630 is disposed. Air may be present in the space 640, so that the dielectric constant may be one. The coaxial filter 600 may be formed in the above-described configuration to serve as a low-pass filter. Meanwhile, the first part 611 and the second part 612 can adjust the impedance by controlling the diameter. For example, the impedance can be increased as the diameter of the second part 612 is decreased, and the impedance can be decreased as the diameter of the second part 612 is increased.

The first part 611 may be provided with a coaxial cable (not shown) having an impedance of 50 ?. The second part 612 contacts the coupling feeding part 500 and can be electrically connected to the lower surface of the dielectric substrate 110 through the coupling feeding part 500. [

The first part 611 can be supplied with power from the coaxial cable. When a signal is applied to the coaxial cable, the applied signal is input to the first part 611, for example, the input terminal through the coaxial cable, and the input signal is inputted to the coupling feeding part 500 And the output signal is coupled to the patch 120 through the coupling coupling power feeder 500. [ At this time, the impedances can be matched through the input terminal and the output terminal, and unnecessary band signals can be attenuated.

The above-described filter-incorporated cavity back antenna can be designed to operate in the frequency range of 2.9 GHz to 3.4 GHz.

3 is a structural view of a cavity-back antenna according to a comparative example of the present invention.

3, a cavity-back antenna according to a comparative example of the present invention includes a microstrip patch antenna 10 having a plate-like dielectric substrate 11 and a patch 12 formed on a top surface of the dielectric substrate 11, A dielectric sheet 20 attached to the lower surface of the dielectric substrate 11, a cavity body 30 attached to the lower surface of the dielectric sheet 20, a dielectric foam 40 filled in the cavity formed on the upper surface of the cavity body 30, And a coupling feeding part 50 which is attached to the lower surface of the dielectric sheet 20 and whose lower part penetrates the lower surface of the cavity body 20 in the up and down direction.

That is, the cavity-back antenna according to the comparative example of the present invention does not include the coaxial filter 600 according to the embodiment of the present invention.

4 is a graph illustrating antenna characteristics according to an embodiment of the present invention and a comparative example. Here, Fig. 4 (a) shows S11 and Fig. 4 (b) shows realized gain.

A cavity-backed antenna with a built-in filter according to an embodiment of the present invention was prepared. In this case, the cavity-backed antenna with a built-in filter according to the embodiment of the present invention has a version in which a coaxial filter is designed as a fifth-order filter and a coaxial filter is designed as a sixth-order filter.

Then, a cavity-back antenna according to a comparative example of the present invention was prepared.

The cavity-embedded cavity-back antennas according to the embodiment of the present invention and the cavity-back antenna according to the comparative example of the present invention were connected to a coaxial cable having an impedance of 50? For feeding.

The cavity built-in cavity back-up antennas according to the embodiment of the present invention and the cavity back-up antenna according to the comparative example of the present invention are operated to measure the antenna characteristics and the measured results are shown in a graph. Here, the target band of the operating frequency was 2.9 GHz to 3.4 GHz.

4 (a) and 4 (b), all three cases have realized gains of S11 and 5 dB or more at 10 dB or less in the target band.

However, the 'Intergrated 5th order filter' graph showing the measurement result of the cavity back antenna (hereinafter, referred to as 'Example 1') having the coaxial filter designed with the fifth filter and the cavity back antenna (S11) and a low realized gain in a frequency band other than the target frequency band in the graph of the 'Intergrated 6th order filter' showing the measurement result of the second embodiment (hereinafter referred to as 'embodiment 2').

On the other hand, the 'Only antenna' graph showing the measurement results of the cavity-back antenna without the coaxial filter (referred to as a "comparative example") shows that S11 and a realized realized gain lower than those in the target frequency band can see.

That is, it can be seen that Embodiments 1 and 2 implement both the characteristics of the filter and the characteristics of the antenna.

Here, comparing Example 1 with Example 2, it is confirmed that Example 2 has a lower realized gain in a frequency band other than the target frequency band. That is, the higher the filter order, the better the frequency blocking characteristic.

However, in terms of size, the first embodiment is designed such that the coaxial filter is designed as a fifth-order filter and the height parameter is designed as 21.97 mm. In the second embodiment, the coaxial filter is designed as a sixth- .

That is, it can be seen that Embodiment 1 is more excellent in terms of reducing the overall size of the filter-incorporated cavity back antenna.

The above-described embodiments of the present invention are for the explanation of the present invention and are not intended to limit the present invention. It should be noted that the configurations and the methods disclosed in the above embodiments of the present invention may be modified into various forms by combining or intersecting with each other, and such modifications are also within the scope of the present invention. That is, the present invention may be embodied in various forms within the scope of the claims and equivalents thereof, and it is possible for the technician skilled in the art to make various embodiments within the scope of the technical idea of the present invention. .

110: dielectric substrate
120: Patch
200: dielectric sheet
300: Cavity body
400: dielectric foam
500: Coupling feeding part
600: coaxial filter

Claims (11)

A planar dielectric substrate;
A patch formed on an upper surface of the dielectric substrate;
A cavity body attached to the lower surface of the dielectric substrate;
A coaxial filter installed to penetrate the cavity body and connected to the lower surface of the dielectric substrate;
A dielectric sheet for attaching the cavity body to the dielectric substrate between the dielectric substrate and the cavity body; And
And a coupling feeding part attached to a lower surface of the dielectric sheet,
And the coaxial filter is connected to the lower surface of the dielectric substrate via the coupling feeding part and the dielectric sheet. The method according to claim 1,
Wherein the lower surface of the coaxial filter and the lower surface of the cavity body are located on the same plane. The method according to claim 1,
Wherein the coaxial filter has different impedances of an input terminal and an output terminal so that impedance matching can be performed. The method according to claim 1,
The patch has an impedance of 100 OMEGA,
Wherein the coaxial filter has an input impedance of 50 OMEGA and an output impedance of 100 OMEGA. The method according to claim 1,
The coaxial filter includes:
A hollow shell having a conductivity;
A core having a conductivity and coaxially disposed on said sheath and applying a signal to said patch and blocking harmonic frequency bands in said signal;
And the core and the core have the same length in the vertical direction. The method of claim 5,
And the lower surface of the core body and the lower surface of the cavity body are located on the same plane. The method of claim 5,
The coaxial filter includes:
And a covering portion having a dielectric constant and disposed between the sheath and the core, the covering portion connecting at least a portion of the sheath with at least a portion of the sheath. The method of claim 7,
Wherein the covering portion comprises a Teflon material. The method of claim 7,
Wherein the core body comprises:
A first part having an impedance of 50?;
A second part protruding upward from an upper surface of the first part and having an impedance of 100?;
And a ring-shaped third part protruding from a plurality of positions of the second part,
A coaxial cable having an impedance of 50? Is provided on the first part,
And the second part is connected to the lower surface of the dielectric substrate. The method of claim 9,
The covering portion connects the outer circumferential surface of the third part and the inner surface of the sheath,
And a space is provided between the outer shell and the core, except for a portion where the cover is disposed. The method of claim 9,
Wherein the first part is shorter in the vertical direction than the second part and has a larger diameter.

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