Patent Description:
In order to satisfy the increasing demands of radio data traffic after the commercialization of a <NUM> communication system, efforts have been made to develop an advanced <NUM> communication system or a pre-<NUM> communication system. For this reason, the <NUM> communication system or the pre-<NUM> communication system is also referred to as a beyond-<NUM> network communication system or a post-LTE system. In order to accomplish a higher data transfer rate, the implementation of the <NUM> communication system in a super-high frequency (mmWave) band (e.g., about a <NUM> band) is being considered. Also, in order to obviate a propagation loss of a radio wave and increase a delivery distance of a radio wave in the super-high frequency band, discussions for the <NUM> communication system are underway about various techniques such as a beamforming, a massive MIMO, a full dimensional MIMO (FD-MIMO), an array antenna, an analog beam-forming, and a large scale antenna. Additionally, for an improvement in network of the <NUM> communication system, technical developments are being made in an advanced small cell, a cloud radio access network (cloud RAN), an ultra-dense network, a device to device (D2D) communication, a wireless backhaul, a moving network, a cooperative communication, coordinated multi-points (CoMP), a reception-end interference cancellation, and the like. Also, in the <NUM> communication system, a hybrid FSK and QAM modulation (FQAM) and a sliding window superposition coding (SWSC) are developed as advanced coding modulation (ACM) schemes, and a filter bank multi carrier (FBMC), a non-orthogonal multiple access (NOMA), and a sparse code multiple access (SCMA) are also developed as advanced access techniques.

Meanwhile, the Internet, which is a human centered connectivity network where humans generate and consume information, is now evolving to the Internet of things (IoT) where distributed entities, such as things, exchange and process information without human intervention. Further, the Internet of everything (IoE), which is a combination of IoT technology and big data processing technology through connection with a cloud server, has emerged. As technology elements, such as sensing technology, wired/wireless communication and network infrastructure, service interface technology, and security technology, have been demanded for IoT implementation, a sensor network, machine-to-machine (M2M) communication, machine type communication (MTC), and so forth have been recently researched. The IoT may be applied to a variety of fields including smart home, smart building, smart city, smart car or connected car, smart grid, health care, smart appliances, advanced medical service, etc. through convergence and combination between existing information technology (IT) and various industrial applications.

In line with this, various attempts have been made to apply the <NUM> communication system to the IoT network. For example, technologies such as a sensor network, machine type communication (MTC), and machine-to-machine (M2M) communication are being implemented on the basis of <NUM> communication technologies such as beamforming, MIMO, and an array antenna. The use of a cloud radio access network (cloud RAN) for big data processing technology is one example of convergence between the <NUM> technology and the IoT technology.

Prior art publications related to antennas and the aforementioned problems are identified below:.

The next generation communication system may use a super-high frequency (mmWave) band. Thus, in order to use the next generation communication system, an antenna module structure capable of smooth communication even in the super-high frequency band is required. Accordingly, the disclosure is to provide an antenna module structure having high efficiency and gain and realizing a simplified manufacturing process in the next generation communication system.

A first object of the present disclosure is an antenna module comprising at least one antenna array, the antenna array including: a first insulator having a plate shape and having a conductive pattern formed to allow an electrical signal to flow; a first radiator disposed to be spaced apart from an upper surface of the first insulator to a lower surface thereof by a predetermined first distance; a second radiator disposed opposite the first radiator and spaced apart, by a predetermined second distance, from a horizontal plane where the first radiator is disposed; at least one feeder electrically connected to the conductive pattern and formed to supply electrical signals to the first and second radiators; a second insulator disposed on the upper surface of the first insulator and fixing the at least one feeder to be spaced apart by a predetermined third distance from a lower surface of a horizontal plane where the first and second radiators are disposed; and a third insulator disposed on the upper surface of the first insulator and fixing on its first side the first radiator and fixing on its second side, opposite the first side, the second radiator.

Preferably, the at least one feeder includes: a first feeder having one end electrically connected to the conductive pattern, having other end spaced apart from a lower surface of the first radiator by the third distance, and supplying an electrical signal related to horizontal polarization to the first radiator; a second feeder having one end electrically connected to the conductive pattern, having other end spaced apart from the lower surface of the first radiator by the third distance, and supplying an electrical signal related to vertical polarization to the first radiator; a third feeder having one end electrically connected to the conductive pattern, having other end spaced apart from a lower surface of the second radiator by the third distance, and supplying an electrical signal related to horizontal polarization to the second radiator; and a fourth feeder having one end electrically connected to the conductive pattern, having other end spaced apart from the lower surface of the second radiator by the third distance, and supplying an electrical signal related to vertical polarization to the second radiator.

Preferably, each of the first, second, third, and fourth feeders includes: a first segment forming a right angle with the upper surface of the first insulator and extending toward the first or second radiator, and a second segment forming a right angle with the first segment and being spaced apart by the third distance from, in parallel with, the lower surface of the horizontal plane where the first and second radiators are disposed.

Preferably, an extension line of the second segment of the first feeder and an extension line of the second segment of the second feeder form a right angle with each other, and an extension line of the second segment of the third feeder and an extension line of the second segment of the fourth feeder form a right angle with each other.

Preferably, the third insulator is a radome.

Preferably, the antenna array further includes a partition wall having a metallic material and disposed between the first radiator and the second radiator.

Preferably, the antenna array further includes a wireless communication chip or circuit board disposed on a lower surface of the first insulator and supplying an electrical signal to the at least one feeder.

A second object of the present disclosure is a base station comprising the antenna module according to the first object of the present disclosure.

The disclosure provides an antenna module structure in which a radiator and a feeder are disposed using an insulator or a radome. Therefore, compared to an antenna module structure using a printed circuit board (PCB), the cost of manufacturing an antenna module may be reduced.

In addition, according to an embodiment of the disclosure, the assembly mass productivity of the antenna module is improved, and thus the defective rate of the antenna module may be reduced.

In addition, according to an embodiment of the disclosure, adjusting the arrangement of feeders and disposing a partition wall between radiators may improve the performance of the antenna module and thus reduce the size of the antenna module.

In the following description of embodiments, descriptions of techniques that are well known in the art and not directly related to the present invention are omitted. This is to clearly convey the subject matter of the disclosure by omitting any unnecessary explanation.

For the same reason, some elements in the drawings are exaggerated, omitted, or schematically illustrated. Also, the size of each element does not entirely reflect the actual size. In the drawings, the same or corresponding elements are denoted by the same reference numerals.

The advantages and features of the disclosure and the manner of achieving them will become apparent with reference to embodiments described in detail below and with reference to the accompanying drawings. Rather, these embodiments are provided so that the disclosure will be thorough and complete and will fully convey the scope of the disclosure to those skilled in the art. To fully disclose the scope of the disclosure to those skilled in the art, the disclosure is only defined by the scope of claims. In the disclosure, similar reference numbers are used to indicate similar constituent elements.

It will be understood that each block of the flowchart illustrations, and combinations of blocks in the flowchart illustrations, may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which are executed via the processor of the computer or other programmable data processing apparatus, generate means for implementing the functions specified in the flowchart block or blocks. These computer program instructions may also be stored in a computer usable or computer-readable memory that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer usable or computer-readable memory produce an article of manufacture including instruction means that implement the function specified in the flowchart block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions that are executed on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks.

In addition, each block of the flowchart illustrations may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s).

The term "unit", as used herein, refers to a software or hardware component or device, such as a field programmable gate array (FPGA) or application specific integrated circuit (ASIC), which performs certain tasks. A unit may be configured to reside on an addressable storage medium and configured to execute on one or more processors. Thus, a module or unit may include, by way of example, components, such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functionality provided for in the components and units may be combined into fewer components and units or further separated into additional components and modules. In addition, the components and units may be implemented to operate one or more central processing units (CPUs) in a device or a secure multimedia card. Also, in embodiments, the unit may include one or more processors.

An antenna module structure disclosed herein may be applied to the next generation communication system. According to an embodiment, the antenna module structure disclosed herein may be applied to a communication system having an operating frequency of <NUM> or less.

<FIG> is a side view showing an antenna array according to a first embodiment of the disclosure.

According to an embodiment, an antenna module <NUM> may include a first insulator <NUM> having a plate shape and having a conductive pattern formed to allow an electrical signal to flow, a first radiator <NUM> disposed to be spaced apart from an upper surface of the first insulator <NUM> to a lower surface thereof by a predetermined first distance, a first feeder <NUM> having one end electrically connected to the conductive pattern, having other end spaced apart from the lower surface of the first radiator <NUM> by a predetermined third distance, and supplying an electrical signal related to horizontal polarization to the first radiator <NUM>, and a second feeder <NUM> having one end electrically connected to the conductive pattern, having other end spaced apart from the lower surface of the first radiator <NUM> by the third distance, and supplying an electrical signal related to vertical polarization to the first radiator <NUM>.

According to an embodiment, the antenna module <NUM> includes a second insulator <NUM> disposed on the upper surface of the first insulator <NUM> and fixing the first feeder <NUM> to be spaced apart by the predetermined third distance from a lower surface of a horizontal plane on which the first radiator <NUM> is disposed, and a third insulator <NUM> disposed on the upper surface of the first insulator <NUM> and fixing the second feeder <NUM> to be spaced apart by the third distance from the lower surface of the horizontal plane on which the first radiator <NUM> is disposed.

According to an embodiment, the second and third insulators <NUM> and <NUM> are formed separately from the first insulator <NUM>, and the second and third insulators <NUM> and <NUM> may be bolted with the first insulator <NUM>. (Bolting is only one example for combining the first insulator, the second insulator, and the third insulator, so that the scope of the disclosure should not be limited to this.

According to an embodiment, the first feeder <NUM> and the second feeder <NUM> may have an 'L' shape. Each of the first and second feeders <NUM> and <NUM> may include a first segment forming a right angle with the upper surface of the first insulator <NUM> and extending toward the first radiator <NUM>, and a second segment forming a right angle with the first segment and being spaced apart by the third distance from, in parallel with, the lower surface of the horizontal plane on which the first radiator <NUM> is disposed.

That is, each of the first and second feeders <NUM> and <NUM> may be supplied with an electrical signal from the conductive pattern of the first insulator <NUM> through the first segment, and may supply the electrical signal to the first radiator <NUM> through the second segment.

According to an embodiment, the third distance from the first radiator <NUM> to the first feeder <NUM> or the second feeder <NUM>, or the area where the second segment of the first and second feeders <NUM> and <NUM> is overlapped with the first radiator <NUM> may be determined based on the frequency characteristics of radio waves to be radiated through the first radiator <NUM>.

According to an embodiment, the first and second feeders <NUM> and <NUM> may have a gap-coupled structure with the first radiator <NUM>. All of the first feeder <NUM>, the second feeder <NUM>, and the first radiator <NUM> may have a metallic material, and the first and second feeders <NUM> and <NUM> may be spaced apart from the first radiator <NUM> by the third distance. That is, the above-described structure may have an effect as if disposing a capacitor or an inductor between the first and second feeders <NUM> and <NUM> and the first radiator <NUM>. This may make it possible to improve the bandwidth of radio waves emitted through the first radiator <NUM>. According to an embodiment, the third distance may be determined based on the frequency characteristics (including a bandwidth) of radio waves emitted through the first radiator <NUM>.

According to an embodiment, the antenna module 10C includes a fourth insulator <NUM> disposed on the upper surface of the first insulator <NUM> and fixing the first radiator <NUM> such that the lower surface of the first radiator <NUM> is spaced apart from the upper surface of the first insulator <NUM> by the first distance. According to an embodiment, the first distance may be determined based on the frequency characteristics (including a bandwidth) of radio waves emitted through the first radiator <NUM>, and also the first distance may be determined in various ways according to a designer's need.

According to an embodiment, the fourth insulator <NUM> is formed separately from the first insulator <NUM>, and the fourth insulator <NUM> may be bolted with the first insulator <NUM>. According to an embodiment, in the fourth insulator <NUM>, the lower surface of the horizontal plane on which the first radiator <NUM> is disposed may be spaced apart from the upper surfaces of the second and third insulators <NUM> by the third distance.

According to an embodiment, a ground layer <NUM> may be disposed on a lower surface of the first insulator <NUM>, and a wireless communication chip or circuit board for supplying electrical signals to the first and second feeders <NUM> and <NUM> may be disposed on a lower surface of the ground layer <NUM>.

According to an embodiment, one antenna array includes two radiators. The antenna array structure including the two radiators will be described below with reference to <FIG>.

<FIG> is a plan view showing an upper surface of the antenna array according to the first embodiment of the disclosure.

According to an embodiment, feeders <NUM>, <NUM>, <NUM>, and <NUM> and insulators <NUM>, <NUM>, <NUM>, and <NUM> for fixing the feeders may be disposed under a first radiator <NUM> and a second radiator <NUM>. However, in <FIG>, for convenience of description, the feeders <NUM>, <NUM>, <NUM>, and <NUM> and the insulators <NUM>, <NUM>, <NUM>, and <NUM> are illustrated as if penetrating the first and second radiators <NUM> and <NUM>.

According to an embodiment, an antenna array 20C includes a first insulator <NUM> having a plate shape and having a conductive pattern <NUM> formed to allow an electrical signal to flow, a first radiator <NUM> disposed to be spaced apart from an upper surface of the first insulator <NUM> to a lower surface thereof by a predetermined first distance, and a second radiator <NUM> disposed to be spaced apart from the first radiator <NUM> by a predetermined second distance on a horizontal plane where the first radiator <NUM> is disposed.

The conductive pattern <NUM> may supply an electrical signal, received from a wireless communication chip or circuit board disposed on a lower surface of a ground layer <NUM>, to the feeders <NUM>, <NUM>, <NUM>, and <NUM>. According to an embodiment, the conductive pattern may include a first port <NUM> for supplying an electrical signal related to horizontal polarization, and a second port <NUM> for supplying an electrical signal related to vertical polarization.

According to an embodiment, the horizontal polarization related electrical signal supplied through the first port <NUM> and the vertical polarization related electrical signal supplied through the second port <NUM> may be distributed by a distributor and then respectively supplied to the first radiator <NUM> and the second radiator <NUM>.

According to an embodiment, the antenna array <NUM> includes a first feeder <NUM> having one end electrically connected to the conductive pattern <NUM>, having other end spaced apart from the lower surface of the first radiator <NUM> by a predetermined third distance, and supplying an electrical signal related to horizontal polarization to the first radiator <NUM>, a second feeder <NUM> having one end electrically connected to the conductive pattern <NUM>, having other end spaced apart from the lower surface of the first radiator <NUM> by the third distance, and supplying an electrical signal related to vertical polarization to the first radiator <NUM>, a third feeder <NUM> having one end electrically connected to the conductive pattern <NUM>, having other end spaced apart from the lower surface of the second radiator <NUM> by the third distance, and supplying an electrical signal related to horizontal polarization to the second radiator <NUM>, and a fourth feeder <NUM> having one end electrically connected to the conductive pattern <NUM>, having other end spaced apart from the lower surface of the second radiator <NUM> by the third distance, and supplying an electrical signal related to vertical polarization to the second radiator <NUM>.

According to an embodiment, an extension line of the first feeder <NUM> and an extension line of the second feeder <NUM> may form a right angle with each other, and also an extension line of the third feeder <NUM> and an extension line of the further feeder <NUM> may form a right angle with each other. Therefore, at the first and second radiators <NUM> and <NUM>, isolation between vertical polarization and horizontal polarization may be improved.

According to an embodiment, the second feeder <NUM> supplying the electrical signal related to the vertical polarization to the first radiator <NUM> and the fourth feeder <NUM> supplying the electrical signal related to the vertical polarization to the second radiator <NUM> may have different arrangement forms. According to an embodiment, a path along which the vertical polarization related electrical signal supplied through the second port <NUM> reaches the second feeder <NUM>, and a path along which the vertical polarization related electrical signal supplied through the second port <NUM> reaches the fourth feeder <NUM> may have a path difference. Due to this path difference, a <NUM>-degree difference may exist between the phase of the electrical signal supplied through the second feeder <NUM> and the phase of the electrical signal supplied through the fourth feeder <NUM>. According to an embodiment, the isolation between the first radiator <NUM> and the second radiator <NUM> may be improved because of a phase difference between the second feeder <NUM> and the fourth feeder <NUM>, so that the performance of the antenna module can be improved.

According to an embodiment, the antenna array <NUM> includes a second insulator <NUM> disposed on the upper surface of the first insulator <NUM> and fixing the first feeder <NUM> to be spaced apart by the predetermined third distance from the lower surface of the horizontal plane on which the first radiator <NUM> is disposed.

According to an embodiment, the antenna array <NUM> may include a third insulator <NUM> disposed on the upper surface of the first insulator <NUM> and fixing the second feeder <NUM> to be spaced apart by the third distance from the lower surface of the horizontal plane on which the first radiator <NUM> is disposed.

According to an embodiment, the antenna array <NUM> may include a fourth insulator <NUM> disposed on the upper surface of the first insulator <NUM> and fixing the third feeder <NUM> to be spaced apart by the third distance from the lower surface of the horizontal plane on which the second radiator <NUM> is disposed.

According to an embodiment, the antenna array <NUM> may include a fifth insulator <NUM> disposed on the upper surface of the first insulator <NUM> and fixing the fourth feeder <NUM> to be spaced apart by the third distance from the lower surface of the horizontal plane on which the second radiator <NUM> is disposed.

<FIG> is a side view showing an antenna array according to a second embodiment of the disclosure.

According to an embodiment, an antenna array <NUM> includes a fourth insulator <NUM> disposed on an upper surface of a first insulator <NUM> and fixing a first radiator <NUM> such that a lower surface of the first radiator <NUM> is spaced apart from the upper surface of the first insulator <NUM> by a predetermined first distance.

According to an embodiment, the antenna array <NUM> may include a second insulator <NUM> and a third insulator <NUM> fixing a first feeder <NUM> and a second feeder <NUM> to be spaced apart by a predetermined third distance from a lower surface of a horizontal plane on which the first radiator <NUM> is disposed.

According to an embodiment, the second insulator <NUM>, the third insulator <NUM>, and the fourth insulator <NUM> may be integrally formed. Alternatively, they may be formed separately and then combined with each other using bolting or adhesive.

Except that the second and third insulators <NUM> and <NUM> may be combined with the fourth insulator <NUM>, the structure of the antenna array <NUM> (including a ground layer <NUM>) shown in <FIG> may be the same as or similar to the structure of the antenna array <NUM> shown in <FIG>.

<FIG> is a side view showing an antenna array according to a third embodiment of the disclosure.

According to an embodiment, an antenna array <NUM> may include a radome <NUM> disposed on an upper surface of a first insulator <NUM> and having a first radiator mounting portion for fixing a first radiator <NUM> to be spaced apart from the upper surface of the first insulator <NUM> by a predetermined first distance.

Although <FIG> shows a case where only one radiator <NUM> is disposed on the radome <NUM>, an antenna array structure in which two radiators are disposed on one radome <NUM> in accordance with the antenna array structure shown in <FIG> may also be considered.

According to an embodiment, a first feeder <NUM> fixed by a second insulator <NUM> is disposed to be spaced apart from the first radiator <NUM> by a predetermined third distance, and a second feeder <NUM> fixed by a third insulator <NUM> may be disposed to be spaced apart from the first radiator <NUM> by the third distance. In this case, the third distance may be shorter than the first distance. According to an embodiment, the first feeder <NUM> and the second feeder <NUM> may supply an electrical signal related to horizontal polarization and an electrical signal related to vertical polarization to the first radiator <NUM>, respectively.

Except that the radome <NUM> on which the first radiator <NUM> is disposed may be included in the antenna array <NUM>, the structure of the antenna array <NUM> (including a ground layer <NUM>) shown in <FIG> may be the same as or similar to the structure of the antenna array <NUM> shown in <FIG>.

<FIG> is a side view showing an antenna array according to a fourth embodiment of the disclosure.

According to an embodiment, the first radiator <NUM> may be disposed on an upper surface of the fourth insulator <NUM>, and a second radiator <NUM> may be disposed on a lower surface of the fourth insulator <NUM> to be opposite to the first radiator <NUM>. The first radiator <NUM> and the second radiator <NUM> may be electrically connected to each other through a vertical interconnect access (VIA) <NUM>.

According to an embodiment, the first and second radiators <NUM> and <NUM> may receive an electrical signal related to horizontal polarization and an electrical signal related to vertical polarization through a first feeder <NUM> and a second feeder <NUM>.

According to an embodiment, the antenna array <NUM> is capable of radiating horizontal polarization and vertical polarization through two radiators <NUM> and <NUM>, and thus may have an improved gain value in comparison with an antenna array structure radiating horizontal polarization and vertical polarization through one radiator.

Except that the first and second radiators <NUM> and <NUM> may be disposed on upper and lower surfaces of the fourth insulator <NUM>, respectively, the structure of the antenna array <NUM> (including a ground layer <NUM> and second insulators <NUM> and <NUM>) shown in <FIG> may be the same as or similar to the structure of the antenna array <NUM> shown in <FIG>.

<FIG> is a view showing an antenna module according to an embodiment of the disclosure.

According to an embodiment, one antenna module <NUM> may include two antenna arrays. As described above in <FIG>, one antenna array may include a first insulator <NUM> having a plate shape and having a conductive pattern formed to allow an electrical signal to flow, a first radiator <NUM> disposed to be spaced apart from an upper surface of the first insulator <NUM> to a lower surface thereof by a predetermined first distance, and a second radiator <NUM> disposed to be spaced apart from the first radiator <NUM> by a predetermined second distance on a horizontal plane where the first radiator <NUM> is disposed.

According to an embodiment, one or more partition walls <NUM> and <NUM> having a metallic material may be disposed between the first radiator <NUM> and the second radiator <NUM>. The partition walls <NUM> and <NUM> may improve isolation between the first radiator <NUM> and the second radiator <NUM>. That is, because of the partition walls <NUM> and <NUM>, the probability that a radio wave emitted through the first radiator <NUM> interfere with a radio wave emitted through the second radiator <NUM> may be reduced.

According to an embodiment, the partition walls <NUM>, <NUM>, <NUM>, and <NUM> may be disposed not only between the first and second radiators <NUM> and <NUM>, but also between the antenna arrays. Therefore, isolation between the antenna arrays may be improved through the partition walls <NUM>, <NUM>, <NUM>, and <NUM>.

Meanwhile, the structures of feeders <NUM>, <NUM>, <NUM>, and <NUM> and second insulators <NUM>, <NUM>, <NUM>, and <NUM> shown in <FIG> may be the same as or similar to those shown in <FIG>. In addition, although <FIG> shows only a case where two antenna arrays are disposed in one antenna module, the scope of the disclosure should not be limited thereto.

<FIG> is a view showing a base station according to an embodiment of the disclosure.

According to an embodiment, a base station <NUM> may include four antenna arrays <NUM>, <NUM>, <NUM>, and <NUM>. The structures of radiators, insulators, and feeders constituting each antenna array are as described in <FIG>.

According to an embodiment, each of the antenna arrays <NUM>, <NUM>, <NUM>, and <NUM> may include a partition wall <NUM>, <NUM>, <NUM>, or <NUM> having a metallic material and disposed between radiators constituting each antenna array. Through this, it is possible to improve the isolation of the antenna array.

Claim 1:
An antenna module comprising at least one antenna array (<NUM>), the antenna array (<NUM>) including:
a first insulator (<NUM>) having a plate shape and having a conductive pattern formed to allow an electrical signal to flow;
a first radiator (<NUM>) disposed to be spaced apart from an upper surface of the first insulator (<NUM>) to a lower surface thereof by a predetermined first distance;
a second radiator (<NUM>) disposed opposite the first radiator (<NUM>) and spaced apart, by a predetermined second distance, from a horizontal plane where the first radiator (<NUM>) is disposed;
at least one feeder (<NUM>, <NUM>) electrically connected to the conductive pattern and formed to supply electrical signals to the first and second radiators (<NUM>, <NUM>);
a second insulator (<NUM>, <NUM>) disposed on the upper surface of the first insulator (<NUM>) and fixing the at least one feeder (<NUM>, <NUM>) to be spaced apart by a predetermined third distance from a lower surface of a horizontal plane where the first and second radiators (<NUM>, <NUM>) are disposed; and
a fourth insulator (<NUM>), disposed on the upper surface of the first insulator (<NUM>), fixing on its first side the first radiator (<NUM>) and fixing on its second side, opposite the first side, the second radiator (<NUM>).