JP2005236590A - Antenna device and mobile communication apparatus having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna device which has a high gain and sharp directional characteristics, with ease and at a low cost. <P>SOLUTION: Then antenna device comprising a plurality of antenna elements arranged at the predetermined spacing on a substrate includes a synthesizer which outputs distributed signal with a predetermined phase difference from different terminals, respectively, by distributing the signal inputted from each antenna element based on the number of the antenna elements. The synthesizer solves the problem by being formed on the substrate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an antenna device and a mobile communication device including the antenna device, and more particularly to an antenna device for realizing highly accurate transmission / reception in a mobile body such as an automobile and a mobile communication device including the antenna device. .

  2. Description of the Related Art Conventionally, a reception field strength switching type diversity antenna is used as a general means for receiving a signal such as a TV broadcast in a moving body such as an automobile or a train.

  In this antenna, for example, two sets of receiving antennas composed of two (two) rod antennas are installed on the roof of an automobile, and outputs from a total of four rod antennas are input to a diversity circuit. Of the four rod antenna outputs, the output with the highest received electric field strength is selected.

  Therefore, in order to take advantage of the effect of diversity, the above-described two sets of antennas are installed with an interval of several wavelengths so as to reduce the correlation between the received intensity fluctuations. The advantage of this method is that an inexpensive diversity circuit can be used.

  Furthermore, as a high-level technique, a reception system using an adaptive array that adaptively controls directivity using an array antenna including a plurality of antenna elements has been proposed (see, for example, Non-Patent Document 1). ). In this method, the phase of each antenna element output before synthesis is adjusted so that the S / N ratio (Signal 1 to Noise ratio) after synthesis of the outputs of a plurality of antenna elements is maximized. The element outputs are synthesized in phase.

  From the standpoint of antenna directivity, this is equivalent to beam forming in the desired direction of radio waves. Compared with the diversity method described above, the gain increases and the directivity pattern also changes. Become sharper. Specifically, as shown in Non-Patent Document 1, as a result of a field experiment by an experimental system using four antenna elements, the average reception rate by the conventional method without directivity control is 48.5. However, when directivity control is performed, the rate is greatly improved to 77.2%, and the superiority of directivity control with four antennas has been clarified.

  In addition, for the purpose of improving reception quality at the time of mobile reception in terrestrial digital broadcasting, reception quality improvement by directivity control has been studied (see, for example, Non-Patent Document 2).

In Non-Patent Document 2, digital signals are demodulated after frequency conversion of signals received by a plurality of antenna elements into IF (intermediate frequency) of 8 MHz and A / D conversion. Furthermore, it is known that by combining weighted signals so that the signals after quadrature demodulation are in phase, the gain and directivity are superior to those of the above-described diversity method.
Nobuyuki Shibata et al., “Study on Improvement Method for Mobile Reception Characteristics of Digital Terrestrial Broadcasting by Directivity Control”, Mobile Computing and Wireless Communication Intelligent Transportation System, p77-p82 (2002.2.128) Yoshitoshi Fujimoto et al. “A Study on Directional Reception of Digital Terrestrial Broadcasting”, 2002 IEICE Communication Society (B-5-70)

  However, since the diversity antenna described above always selects an antenna output having a large reception output among the four antennas, only one antenna is operating as the antenna operation. Therefore, the antenna gain and directivity have values and characteristics corresponding to one antenna.

  In other words, for example, even if four antennas are installed on the roof of an automobile, the gain of the antenna is low, and the directivity is widened because it is received with the directivity characteristic of one antenna element, and reflected waves from buildings, buildings, etc. It was easy to receive and reception performance was not enough.

  On the other hand, the method of constructing an adaptive array by attaching an array antenna composed of a plurality of antenna elements to the roof of a moving body operates as an array antenna, so both gain and directivity are characteristics compared to the diversity method described above. However, as shown in Non-Patent Document 2, it is necessary to amplify the antenna output after frequency conversion, to further A / D convert, and to perform complex multiplication by a weighting synthesis circuit corresponding to a phase control and synthesis circuit There is. For this reason, since the device configuration of the antenna device increases and the processing becomes complicated, it cannot be said that the antenna device is suitable for a mobile communication device from the viewpoint of cost.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an antenna device having high gain and sharp directivity characteristics easily and inexpensively, and a mobile communication device including the antenna device.

  In order to solve the above problems, the present invention employs means for solving the problems having the following characteristics.

  According to the first aspect of the present invention, in an antenna device composed of a plurality of antenna elements arranged at a predetermined interval on a substrate, a signal input from each antenna element is distributed based on the number of antenna elements, and the distributed signal Each of which is output from a different terminal with a predetermined phase difference, and the combined circuit is formed on the substrate.

  According to the first aspect of the present invention, it is possible to easily and inexpensively realize an antenna device with high gain and sharp directivity. Thereby, highly accurate reception can be realized.

According to a second aspect of the present invention, the combining circuit distributes a signal input from the terminal based on the number of antenna elements, and distributes the distributed signal to one of the plurality of antenna elements. According to the second aspect of the present invention, an antenna device having a high gain and a sharp directivity can be realized easily and inexpensively. Thereby, highly accurate transmission is realizable.

The invention described in claim 3 is characterized in that the synthesis circuit includes the same number of hybrid circuits as the number of antenna elements, and the hybrid circuits are arranged at a predetermined interval. Therefore, by using the hybrid circuit, it is possible to easily and inexpensively distribute one input to a plurality of terminals, and to form a circuit in which the distributed output has a predetermined phase difference.

  The invention described in claim 4 is characterized in that the number of antenna elements is four or more.

  According to the fourth aspect of the present invention, by having four or more antenna elements, it is possible to select an output terminal that maximizes received power from directivity characteristics in four or more directions. As a result, an antenna device having a high gain and a sharp directivity can be realized easily and inexpensively.

  The invention described in claim 5 includes a diversity circuit that outputs only a signal having the maximum received electric field strength among signals input from the antenna elements, and the diversity circuit is formed on the substrate. It is characterized by that.

  According to the fifth aspect of the present invention, since the diversity circuit is formed on the substrate, transmission / reception with high gain and sharp directivity can be realized without increasing the scale of the antenna device. Moreover, the mounting property to a mobile communication apparatus can also be improved.

  The invention described in claim 6 is a mobile communication device including the antenna device according to any one of claims 1 to 5.

  According to the sixth aspect of the present invention, it is possible to realize highly accurate transmission / reception by providing the mobile communication device with an antenna device that is configured easily and inexpensively and has a high gain and sharp directivity.

  According to the present invention, it is possible to provide an antenna device with high gain and sharp directivity characteristics easily and inexpensively.

<Outline of the present invention>
According to the present invention, in an antenna device composed of a plurality of antenna elements, a signal input from each antenna element is distributed based on the number of antenna elements, and the distributed signal is output with a predetermined phase difference. By providing a simple circuit, a switchable diversity antenna apparatus having a number of independent directivities corresponding to the number of antenna elements is provided.

  Here, in the present invention, in order to operate the antenna device as an array antenna, the antenna elements are arranged at equal intervals of one wavelength or less. Moreover, as an antenna element, a rod antenna, a patch antenna, or the like used in conventional diversity antennas can be used.

  Further, when the outputs from the respective antenna elements are combined, the antenna device of the present invention uses a combining circuit formed on the printed board and including the same number of hybrid circuits as the respective antenna elements. The output of the combining circuit has output terminals corresponding to the number of antenna elements arranged, and outputs from the terminals are input to the diversity circuit. The diversity circuit outputs the signal having the highest reception intensity among the input signals to the diversity circuit output terminal.

  At this time, signals with different phase differences are output from other antenna elements based on the output of a certain antenna element from the arrayed antenna elements, so each output terminal of the synthesis circuit corresponds to the antenna element. Thus, the output when directivity is formed in different directions is obtained.

  Therefore, each output from the combining circuit can obtain an antenna output having the same gain and directivity as when the beam is formed by the array antenna including the same number of antenna elements. In other words, the same effects as those obtained when an array antenna is configured can be obtained at a low cost, and the configuration of the antenna device is very simple. For example, an antenna device is installed in a mobile communication device such as an automobile to receive a TV broadcast. Etc. can be realized more easily. The antenna device according to the present invention may be used not only for reception but also for transmission.

<Embodiment>
Next, an embodiment to which the present invention is applied will be described with reference to the drawings. In the embodiment of the present invention, as shown in Non-Patent Document 2, the reception rate by directivity control is increased by further increasing the number of antenna elements. Considering this, four antenna elements are used. In the present embodiment, a board on which a plastic substrate, a ground plate, and a printed board, which will be described later, are superposed is referred to as a “substrate”.

  FIG. 1 is a diagram showing an example of the first embodiment of the present invention. 1A is a perspective view of the antenna device 10 according to the first embodiment, and FIG. 1B is a back plan view of the antenna device 10.

  In the antenna device 10 of FIG. 1, rod antennas 11 a to 11 d having a quarter wavelength as antenna elements are squarely installed on a plastic substrate 12. Moreover, although the installation interval of the rod antennas 11a to 11d is set to 3/4 wavelength, in the present invention, the interval between the antenna elements may be one wavelength or less, and may be arranged, for example, at 1/2 wavelength interval.

  A ground plate 13 is formed under the plastic substrate 12. A printed circuit board 14 is installed under the ground plate 13. The printed circuit board 14 is formed with a composite circuit as shown in FIG. This synthetic circuit is a planar circuit created by etching or the like. Here, the outputs of the rod antennas 11a to 11d are connected to the rod antenna output terminals 15a to 15d, respectively.

  The planar circuit on the printed circuit board 14 is composed of hybrid circuits 16a to 16d. Here, the operation of the hybrid circuit 16 will be described with reference to the drawings. FIG. 2 is a diagram for explaining the operation of the hybrid circuit. The circuit shown in FIG. 2 is a hybrid ring circuit. The hybrid ring circuit 20 shown in FIG. 2 is configured to have an input terminal 21, a separation terminal 22, and two output terminals 23 and 24, and one side has a quarter wavelength (however, the wavelength (λ ) Is composed of a square transmission line with a wavelength on the substrate depending on the dielectric constant of the printed circuit board.

  In the hybrid circuit shown in FIG. 2, the signal input from the input terminal 21 is divided into two equal parts and output from the output terminal 23 and the output terminal 24. At this time, if the phase of the signal at the output terminal 23 is 0 °, the signal at the output terminal 23 can obtain an output with a phase delayed by 90 °.

  Similarly, the signal input from the separation terminal 22 is divided into two equal parts and output from the output terminal 23 and the output terminal 24. If the phase of the signal at the output terminal 24 is 0 °, the output terminal 23 is 90 °. A delayed phase output is obtained. Here, the outputs of the input terminal 21 and the separation terminal 22 are separated from each other (isolation), and each operates as a single bisection circuit.

  The hybrid circuit that performs the same operation as the above-described hybrid ring circuit is not limited to this, and includes, for example, a branch line coupler type. Further, the circuit used in the present invention is not limited to a hybrid circuit, and one input is distributed to two output terminals. The distributed output is the output of one output terminal, and the other output terminal is predetermined. It is only necessary to be configured to output with a phase difference of. However, by using the above-described hybrid circuit, it is cheap and easily distributed to two output terminals for one input, and the distributed output has a predetermined phase difference (λ / 4 in FIG. 2). A circuit can be formed.

  Here, the hybrid circuit 16 of FIG. 1 will be described in correspondence with the circuit of FIG. The output of the rod antenna 11a in FIG. 1 is output to the rod antenna output terminal 15a. This means that the hybrid ring circuit 20 shown in FIG. 2 is connected to the output terminal 24. The output of the rod antenna 11b is output to the rod antenna output terminal 15b. This means that the hybrid ring circuit 20 shown in FIG. 2 is connected to the output terminal 23.

  Similarly, the output of the rod antenna 11c is output to the rod antenna output terminal 15c. This means that the hybrid ring circuit 20 shown in FIG. 2 is connected to the output terminal 23. The output of the rod antenna 11d is output to the rod antenna output terminal 15d. This means that the hybrid ring circuit 20 shown in FIG. 2 is connected to the output terminal 24.

  Further, the input terminal 21 of the hybrid circuit 16a is connected to the output terminal 24 of the hybrid circuit 16b, and the separation terminal 22 of the hybrid circuit 16a is connected to the output terminal 23 of the hybrid circuit 16d. Similarly, the input terminal 21 of the hybrid circuit 16c is connected to the output terminal 24 of the hybrid circuit 16d, and the separation terminal 22 of the hybrid circuit 16c is connected to the output terminal 23 of the hybrid circuit 16b.

  Further, the input terminal 21 of the hybrid circuit 16b is connected to the combined circuit output terminal 17d, the separation terminal 22 of the hybrid circuit 16b is connected to the combined circuit output terminal 17b, and the input terminal 21 of the hybrid circuit 16d is connected to the combined circuit output terminal 17a. The separation terminals 22 of the hybrid circuit 16d are respectively connected to the synthesis circuit output terminal 17c.

  Note that from the combined circuit output terminal 17a to the rod antenna output terminal 15a, from the combined circuit output terminal 17b to the rod antenna output terminal 15b, from the combined circuit output terminal 17c to the rod antenna output terminal 15c, and from the combined circuit output terminal 17d to the rod antenna output terminal 15d. Are connected by a microstrip line 18, the line lengths are equal, and the rod antennas 11a to 11d resonate at the same frequency. The synthesis circuit output terminals 17a to 17d are connected to a diversity circuit or the like, and an output terminal having the maximum received power is selected from the four synthesis circuit output terminals and a signal is output.

  Next, when each signal is input from the combining circuit output terminals 17a to 17d when the antenna device shown in FIG. 1 is used as a transmission antenna, what phase current is supplied to the rod antennas 11a to 11d. Will be described with reference to the drawings.

  FIG. 3 is a diagram showing an example of the mutual phase relationship of each antenna element of the antenna device according to the present invention. As shown in FIG. 3, for example, when a signal is input from the synthesis circuit output terminal 17a, assuming that the phase of the current fed to the rod antenna 11a is 0 °, the rod antenna 11b has a current delayed by 90 °. Power is supplied. The rod antenna 11c is also fed with a current having a phase difference of 90 °. The rod antenna 11d is supplied with a current having a phase of 180 °. This is because the rod antenna 11a and the rod antenna 11d have a distance corresponding to ½ wavelength on the transmission line.

  This shows that when the rod antennas 11a to 11d are array antennas, a radiation phase plane inclined from the rod antenna 11a toward the rod antenna 11d is formed. Similarly, as shown in FIG. 3, signals are output to the respective rod antennas when the signals are input to the synthesis circuit output terminals 17b to 17d according to different phase conditions.

  That is, the antenna device configured by the rod antennas 11a to 11d has four different phase relationships, and independent directivity patterns are formed in the four directions.

  As shown in the first embodiment, by combining four antenna elements formed on a substrate and a composite circuit having a hybrid circuit, directivity independent in four directions is formed with a simple configuration. An antenna device can be realized. The directivity characteristics in the four directions can be obtained by selecting a predetermined terminal from the four output terminals. Therefore, for example, by inputting outputs from four output terminals into a conventional diversity circuit or the like and selecting a terminal having the maximum received power, an antenna apparatus having high gain and sharp directivity can be realized easily and inexpensively. it can.

  Moreover, as shown in FIG. 1, the antenna apparatus which consists of a rod antenna can be used, for example as a receiving antenna of terrestrial digital broadcasting.

  Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a diagram illustrating an example of the second embodiment of the antenna device according to the present invention. 4A is a perspective view of the antenna device 40 according to the second embodiment, and FIG. 4B is a back plan view of the antenna device 40.

  In the antenna device 40 shown in FIG. 4, circularly polarized patch antennas 41 a to 41 d are formed on the printed circuit board 42 instead of the rod antennas 11 a to 11 d shown in FIG. 1. As for the outputs of the patch antennas 41a to 41d, the feed points 43a to 43d of the patch antennas 41a to 41d are connected to the patch antenna output terminals 55a to 55d, and signals are input and output therefrom.

  A ground plate 44 is formed under the printed circuit board 42. Moreover, although the arrangement | positioning space | interval of each patch antenna 41a-41d is set to 3/4 wavelength, the space | interval of an antenna element should just be 1 wavelength or less in this invention, for example, you may arrange | position with a 1/2 wavelength space | interval.

  A printed circuit board 45 is installed under the ground plate 44. The printed circuit board 45 is formed with a composite circuit as shown in FIG. This synthetic circuit is a planar circuit created by etching or the like. Moreover, each hybrid circuit 56a-56d is connected by the microstrip line 58, and the line length is equal.

  The patch antennas 41a to 41d are formed with notches at two corners as shown in FIG. 4 in order to receive circularly polarized waves. However, the present invention is not limited to this. The antennas 41a to 41d may be rectangular without receiving cutouts so as to receive linearly polarized waves.

  In the second embodiment, the synthesis circuit formed on the printed circuit board 45 has a diversity circuit 59. Thereby, a compact and inexpensive apparatus can be realized. The diversity circuit can be similarly formed on the printed board in the first embodiment described above.

  Here, the operations of the hybrid circuits 56a to 56d connected to the patch antenna output terminals 55a to 55d are the same as those in the first embodiment described above, but in the second embodiment, the diversity circuit 59 is an antenna. It is provided in the device 40. That is, the outputs from the synthesis circuit output terminals 57a to 57d are directly input to the diversity circuit 59 provided on the same printed circuit board 45, and the output having the highest received electric field strength is selected by the diversity circuit 59 and the diversity circuit output terminal. 47 is output. Further, the output of the diversity circuit output terminal 47 is output from the antenna combining output terminal 48 via the microstrip line 46.

  As described above, by applying the second embodiment, the directivity characteristics in the four directions can be obtained by the diversity circuit 59 selecting four output terminals. As a result, an antenna device having a high gain and a sharp directivity can be realized easily and inexpensively.

  Further, since the patch antenna shown in the second embodiment can be used in a microwave band such as 2.6 GHz band, for example, broadcasting from a quasi-zenith satellite or the like that is expected to be launched in the future. It can be applied as an antenna device for receiving.

  Here, directivity characteristics of the combined output terminal when the above-described embodiment is applied will be described with reference to the drawings. FIG. 5 is a diagram illustrating an example of directivity when the composite output terminal 57c in the second embodiment is selected.

  In FIG. 5, the horizontal axis indicates the x-axis, and the vertical axis indicates the y-axis angle (deg.). An intersection 0 ° between the x-axis and the y-axis indicates a center point located at the same distance from each antenna element, and indicates a z-axis direction (zenith direction) perpendicular to the plane formed by the printed circuit board 42. ing. The x-axis, y-axis, and z-axis correspond to the x-axis, y-axis, and z-axis shown in FIGS. That is, FIG. 5 shows the directivity pattern on the xy plane.

  As shown in FIG. 5, the phase plane of the combined circuit output terminal 57b shown in FIG. 4 can be acquired by the patch antennas 41a to 41d, and a directivity pattern tilted with respect to the z-axis direction is formed. The directivity is maximum (+6 dB) in the plane of “x> 0, y> 0”.

  FIG. 5 shows the directivity pattern (x> 0, y> 0) when the combined output terminal 57c is selected as the output with the highest received electric field strength. If selected, the directivity patterns that are rotationally symmetric about the z axis are “x <0, y <0”, “x <0, y> 0”, and “x> 0, y <0”, respectively. Will be formed.

  Specifically, when the combined output terminal 57b is selected as the output having the highest received electric field strength, the directivity is maximized in the plane of “x> 0, y> 0”, and the combined output terminal 57a is selected. In this case, the directivity is maximized in the plane of “x <0, y> 0”, and the directivity in the plane of “x> 0, y <0” is selected when the composite output terminal 57d is selected. Maximum.

  Thus, by applying the present invention and selecting four output terminals, directivity characteristics in four directions can be obtained. Further, by inputting these four output terminals to the diversity circuit and selecting the terminal having the maximum received power, the antenna apparatus for terrestrial digital broadcasting mobile reception having high gain and sharp directivity characteristics easily and inexpensively. Can be realized.

  Next, an embodiment when the present invention is applied to a mobile communication device such as an automobile will be described with reference to the drawings. FIG. 6 is a diagram showing an example in which the antenna device according to the present invention is installed in an automobile. In FIG. 6, the antenna device according to the first embodiment described above is used as an example.

  In FIG. 6, an antenna device 62 is installed on a roof portion 61 of an automobile 60, and rod antennas 63 a to 63 d are further installed on a substrate 64. For example, when signals are received from the rod antennas 63a to 63d, the signals input by the rod antennas 63a to 63d are sent to the synthesis circuit output terminals 65a to 65d formed on the substrate 64, and the respective synthesis circuit output terminals. The signal is output to a diversity circuit 67 installed in the vehicle by a cable 66 connected corresponding to 65a to 65d. Diversity circuit 67 selects the signal having the highest received electric field strength from the input signals as described above and outputs the selected signal to display output device 68 to output optimal video, audio, and the like from display output device 68. it can.

  As described above, according to the present invention, it is possible to easily and inexpensively provide an antenna device with high gain and sharp directivity and a mobile communication device including the antenna device. Specifically, by combining a plurality of antenna elements and a circuit that distributes one input signal to a plurality of signals, and further outputs the distributed signal with a predetermined phase difference, it is possible to move in different directions with a simple configuration. An antenna device capable of forming independent directivity can be realized. In addition, it can form easily by using a hybrid circuit as a circuit output with the above-mentioned predetermined phase difference.

  In addition, by installing the antenna device according to the present invention in a moving body such as an automobile, the directivity of the antenna can be improved even in a radio wave environment that changes with time, for example, when receiving terrestrial digital broadcasting while running in an automobile. Therefore, it is possible to realize a mobile communication device that is always optimal. The present invention is not limited to use for receiving terrestrial digital broadcasts, but may also be used as an antenna device for receiving broadcasts from a quasi-zenith satellite or the like scheduled for future launch in a mobile object. Can do.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to such specific embodiments, and various modifications, within the scope of the gist of the present invention described in the claims, It can be changed.

It is a figure which shows an example of 1st Embodiment in this invention. It is a figure for demonstrating operation | movement of a hybrid circuit. It is a figure of an example which shows the mutual phase relationship of each antenna element of the antenna apparatus in this invention. It is a figure which shows an example of 2nd Embodiment of the antenna apparatus in this invention. It is a figure which shows an example of directivity when the output terminal 57b in 2nd Embodiment is selected. It is a figure which shows an example which installed the antenna apparatus in this invention in the motor vehicle.

Explanation of symbols

10, 40, 62 Antenna device 11, 63 Rod antenna 12 Plastic substrate 13, 44 Ground plate 14, 42, 45 Printed substrate 15 Rod antenna output terminal 16, 56 Hybrid circuit 17, 57, 65 Composite circuit output terminal 18, 46, 58 Microstrip line 20 Hybrid ring circuit 21 Input terminal 22 Separation terminal 23, 24 Output terminal 41 Circularly polarized patch antenna 43 Feeding point 47 Diversity circuit output terminal 48 Antenna combined output terminal 55 Patch antenna output terminal 59, 67 Diversity circuit 60 Automobile 61 Roof 61
64 Substrate 66 Cable 68 Display output device

Claims (6)

In an antenna device composed of a plurality of antenna elements arranged at predetermined intervals on a substrate,
It has a combining circuit that distributes signals input from each antenna element based on the number of antenna elements, and outputs the distributed signals from different terminals with a predetermined phase difference,
The antenna device according to claim 1, wherein the synthesis circuit is formed on the substrate. The synthesis circuit is:
The signal input from the terminal is distributed based on the number of antenna elements, and the distributed signal is output with a predetermined phase difference with reference to the output to one antenna element among the plurality of antenna elements. The antenna device according to claim 1. The synthesis circuit is:
The antenna device according to claim 1, comprising the same number of hybrid circuits as the number of antenna elements, wherein the hybrid circuits are arranged at a predetermined interval.   The antenna apparatus according to claim 1, wherein the number of antenna elements is four or more. Among the signals input from each antenna element, it has a diversity circuit that outputs only the signal with the maximum received electric field strength,
The diversity circuit is formed on the substrate.   A mobile communication device comprising the antenna device according to claim 1.

Images