JP2007306323A - Antenna, and wireless communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact antenna capable of obtaining sufficient receiving gain in a high frequency band of a UHF-band television signal or the like, and to provide a wireless communication apparatus. <P>SOLUTION: The reverse F type antenna 1A is provided with a plate-like radiation conductor 2 stored in a door mirror 110 and using a metallic film 112b of a reflector 112 as a ground, a short-circuit conductor 3 for short-circuiting the base end of the radiation conductor 2 with the metallic film 112b and feeding points 4A, 4B, 4C of the radiation conductor 2 which are arranged on respectively different distances L1, L2, L3 from the short-circuit conductor 3, and constituted so as to select the feeding points 4A to 4C in accordance with the frequency band of a receiving signal. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an antenna and a wireless communication apparatus that receive or transmit high-frequency signals such as digital TV.

  As a conventional vehicle antenna, there is an antenna using an inverted-F antenna that is advantageous in terms of small size (for example, see Patent Document 1).

  In this antenna, a concave antenna housing portion is provided on the roof of a vehicle, an inverted F-type antenna is housed in the antenna housing portion, and the upper portion is closed with a housing lid. The antenna housing portion is made of a metal plate and serves as a ground for the inverted F-type antenna. According to this configuration, since there is no portion protruding outside the vehicle body, the design of the vehicle is not impaired, and the antenna can be prevented from being broken.

  Further, as a conventional vehicle antenna, an antenna shared by VHF (ultra high frequency) and UHF (ultra high frequency) is known (for example, see Patent Document 2).

This antenna selects either one of a main monopole element for VHF and a sub monopole element for UHF having different lengths, and a reception signal output from the main monopole element and the sub monopole element. A switching device for outputting to a television receiver. According to this configuration, a small antenna can be provided.
JP 2003-17916 A JP-A-6-303024

  However, since the conventional inverted-F antenna has a small radiating conductor and a relatively narrow band, the antenna configuration has a satisfactory reception gain over the entire UHF (ultra high frequency) frequency (470 MHz to 710 MHz). Difficult to do.

  Since the conventional antenna using a monopole element uses a plurality of antennas, it is difficult to reduce the size. In addition, the antenna may protrude from the vehicle body, which may impair the design of the vehicle.

  Accordingly, it is an object of the present invention to provide an antenna and a wireless communication apparatus that are small in size and can obtain a sufficient reception gain in a high frequency region such as a UHF band.

  In order to achieve the above object, the present invention provides an antenna comprising a radiation conductor and a plurality of feeding points provided on the radiation conductor.

  According to the antenna having the above configuration, the band of the radiation conductor can be widened by switching the feeding point according to the frequency of the high-frequency signal to be communicated.

  In order to achieve the above-mentioned object, the present invention switches and switches a plurality of feeding points of the antenna based on a selection signal and an antenna having a radiation conductor and a plurality of feeding points provided on the radiation conductor. There is provided a wireless communication device comprising a switching circuit for feeding power to the radiation conductor via the feeding point.

  According to the wireless communication apparatus having the above configuration, the band of the radiation conductor can be widened by switching the feeding point by the switching circuit according to the frequency of the high-frequency signal to be communicated.

  The antenna may be attached to the vehicle. Moreover, you may accommodate in the mirror of a vehicle. According to this configuration, the antenna can be attached to the vehicle without impairing the design of the vehicle.

  The radiation conductor may be configured to receive a UHF band television signal. When the length of the radiation conductor is ¼ wavelength, the antenna can be downsized by setting the wavelength of the received signal to the UHF band.

  The antenna includes a radiation conductor, a ground conductor disposed opposite to the radiation conductor, a short-circuit conductor connecting the radiation conductor and the ground conductor, and a plurality of feeding points disposed at different distances from the short-circuit conductor. May be provided.

  In the above configuration, the radiation conductor, the ground conductor, the short-circuit conductor, and the plurality of feeding points may be accommodated in a vehicle mirror, and the ground conductor may be a conductive reflector of the mirror. Thereby, it is not necessary to provide a separate ground conductor, and the configuration of the antenna can be simplified.

  The radiation conductor, the ground conductor, the short-circuit conductor, and the plurality of feeding points may constitute an inverted F-type antenna. Thereby, size reduction of an inverted F type antenna can be achieved.

  According to the present invention, it is small and sufficient reception gain can be obtained in a high frequency region such as a UHF band television signal.

[First Embodiment]
FIG. 1 is a perspective view showing an external appearance of a vehicle to which a wireless communication apparatus according to a first embodiment of the present invention is applied.

  The vehicle 100 is equipped with a digital TV image receiving system 10 as a wireless communication device. The digital TV image receiving system 10 includes an inverted F-type antenna 1A housed in a door mirror 110 provided at the front end of the left and right front doors 101, a TV monitor 16 disposed in the front of the vehicle, and inside the front door 101. The speaker 19 and the remote controller (hereinafter referred to as “remote controller”) 15 for the TV monitor 16 are provided. In the figure, reference numeral 102 denotes a windshield, and 103 denotes a room mirror.

  2A and 2B show a door mirror, in which FIG. 2A is a perspective view and FIG. 2B is a cross-sectional view taken along line AA in FIG. The door mirror 110 includes a door mirror case 111 made of a synthetic resin molded product and a reflecting mirror 112, and the inverted F-type antenna 1 </ b> A is disposed inside the reflecting mirror 112.

  The reflecting mirror 112 includes a substrate 112a made of a resin such as acrylic or glass, and a metal film 112b as a conductive reflector made of aluminum or the like formed on the back surface of the substrate 112a by vapor deposition or the like. The conductive reflector may be made of an oxide semiconductor such as ITO (indium tin oxide).

  Inverted F-type antenna 1A of the present embodiment uses metal film 112b of reflecting mirror 112 as a ground, and short-circuits flat radiation conductor 2, the base end of radiation conductor 2, and metal film 112b. The conductor 3 is provided with feeding points 4A, 4B, 4C arranged at different distances L1, L2, L3 from the short-circuit conductor 3 of the radiation conductor 2. The feeding point 4A arranged at the position closest to the short-circuit conductor 3 is for low frequency (for example, 470 to 550 MHz), and the feeding point 4C arranged at the position farthest from the short-circuit conductor 3 is for high frequency (for example, 630 to 710 MHz), and the feeding point 4B disposed between the feeding point 4A for low frequency and the feeding point 4C for high frequency is for medium frequency (for example, 550 to 630 MHz).

  A circuit board 11 is disposed between the radiation conductor 2 of the inverted F-type antenna 1 </ b> A and the reflecting mirror 112. The configuration of the circuit board 11 will be described later.

  The radiation conductor 2 has a length of λ / 4, for example, where λ is the wavelength of the received radio wave. The radiation conductor 2 has a width of 40 mm and a length of 120 mm, for example, and the short-circuit conductor 3 has a height of 30 mm, for example.

  A coaxial cable 17 is connected to the inverted F-type antenna 1A via the circuit board 11. The outer conductor 17a of the coaxial cable 17 is connected to the metal film 112b by solder 17b, and the central conductor 17c of the coaxial cable 17 is The circuit board 11 is connected.

  FIG. 3 is a block diagram of the digital TV receiving system 10. The digital TV image receiving system 10 amplifies a television signal received by the inverted F-type antenna 1A, a feed point switching circuit 12A for switching the feed points 4A to 4C of the inverted F-type antenna 1A, and the inverted F-type antenna 1A. The TV tuner 14 for selecting a television signal from the signal amplified by the high-frequency amplifier 13, the remote controller 15 for transmitting a channel selection signal to the TV tuner 14 by infrared rays, and the TV tuner 14. A TV monitor 16 for outputting the video of the selected broadcast station and the speaker 19 for outputting the sound of the broadcast station selected by the TV tuner 14 are provided. The feeding point switching circuit 12A and the high frequency amplifier 13 constitute the circuit board 11 shown in FIG.

  The TV tuner 14 selects a television signal of the corresponding broadcasting station based on channel selection by the remote controller 15, demodulates the video signal and the audio signal from the television signal, outputs the video signal to the TV monitor 16, and outputs the audio signal. Is output to the speaker 19.

  The TV monitor 16 displays an image on the color liquid crystal panel based on the video signal sent from the TV tuner 14.

  4A shows the feeding point switching circuit 12A, and FIG. 4B shows the circuit configuration of the switch. The feed point switching circuit 12A includes a first comparator 120 that compares an input voltage to the + input terminal 120a and a reference voltage (−2V) to the − input terminal 120b, an input voltage to the + input terminal 121a, and −. A second comparator 121 that compares a reference voltage (−3 V) to the input terminal 121 b, a NOT circuit 122 having an input connected to the output terminal 120 c of the first comparator 120, and the first and second comparators 120. , 121 includes an Ex-OR circuit 123 having inputs connected to the output terminals 120c, 121c.

  In addition, the feed point switching circuit 12A has switches 124A to 124C connected between the central conductor of the coaxial cable 17 and the feed points 4A to 4C, respectively, and the control terminal of the switch 124A has a second comparator 121 connected to the control terminal. The output terminal 121c is connected, the output of the Ex-OR circuit 123 is connected to the control terminal of the switch 124B, and the output of the NOT circuit 122 is connected to the control terminal of the switch 124C.

  As shown in FIG. 4B, each switch 124A to 124C is connected to an input terminal 125a to which the central conductor of the coaxial cable 17 from the high-frequency amplifier 13 is connected and the feeding points 4A to 4C of the inverted F-type antenna 1A. Output terminal 125b and a control terminal 125c to which the output terminal of the second comparator 121, NOT circuit 122 or Ex-OR circuit 123 is connected, a PIN diode D1, capacitors C1 to C3, choke coil L1, Series type composed of L2 etc.

  FIG. 5 shows the reception characteristics of the inverted F-type antenna 1A, and shows the relationship between the distance from the short-circuit conductor 3 to the feed points 4A to 4C and the gain of the received signal. In the figure, the solid line indicates a reception characteristic of a reception frequency of 470 MHz, the broken line indicates a reception characteristic of 590 MHz, and the alternate long and short dash line indicates a reception characteristic of 710 MHz. The distances from the short-circuit conductor 3 to the low-frequency feed point 4A, the medium-frequency feed point 4B, and the high-frequency feed point 4C are set to 10 mm, 40 mm, and 70 mm, for example. The gain of the received signal is about −9 dB at the low frequency feed point 4A, about −2 dB at the medium frequency feed point 4B, and about −3 dB at the high frequency feed point 4C. It can be seen that it has reception sensitivity.

(Operation of the first embodiment)
Next, the operation of the first embodiment will be described. When the user operates the remote controller 15 to select a channel, the remote controller 15 transmits a channel selection signal to the TV tuner 14 by infrared rays. The TV tuner 14 transmits a channel selection signal to the feed point switching circuit 12A via the high-frequency amplifier 13 by the signal cable 18. The feed point switching circuit 12A feeds power to the corresponding feed points 4A to 4C based on the channel selection signal.

  For example, when a 4V selection signal is output to the feed point switching circuit 12A, the first comparator 1201 compares the 4V selection signal with the 2V reference voltage, and the selection signal is higher than the 2V reference voltage. A level signal is output. The second comparator 121 compares the 4V selection signal with the 3V reference voltage, and outputs an H level signal because the selection signal is higher than the 3V reference voltage. Therefore, the outputs of the NOT circuit 122 and the Ex-OR circuit 123 become L level, the H level output signal of the second comparator 121 is supplied to the control terminal 125c of the high frequency switch 124C, and the input terminal of the switch 124C. 125a and the output terminal 125b become conductive.

  When the 2.5V selection signal is output to the feed point switching circuit 12A, the first comparator 120 compares the 2.5V selection signal with the 2V reference voltage, and the selection signal has a 2V reference voltage. Since it is higher, an H level signal is output. The second comparator 121 compares the 2.5V selection signal with the 3V reference voltage, and outputs an L level signal because the selection signal is lower than the 3V reference voltage. For this reason, the output of the NOT circuit 122 becomes L level, the output of the Ex-OR circuit 123 becomes H level and is output to the control terminal 125c of the switch 124B for medium frequency, and the output from the input terminal 125a of the switch 124B. The terminal 125b becomes conductive.

  When the 1V selection signal is output to the feed point switching circuit 12A, the first comparator 120 compares the 1V selection signal with the 2V reference voltage, and the selection signal is lower than the 2V reference voltage. A level signal is output. The second comparator 121 compares the 1V selection signal with the 3V reference voltage, and outputs an L level signal because the selection signal is lower than the 3V reference voltage. For this reason, the output of the Ex-OR circuit 123 becomes L level, the output of the NOT circuit 122 becomes H level, and is output to the control terminal 125c of the low frequency switch 124A, and the input terminal 125a and the output terminal of the switch 124A. 125b becomes conductive.

(Effects of the first embodiment)
According to the first embodiment, the following effects can be obtained.
(A) By switching the feeding points 4A to 4C according to the frequency of the received high-frequency signal, the band of the inverted F-type antenna can be expanded.
(B) By using the metal film 112b of the door mirror 110 as the ground conductor of the inverted F-type antenna, it is not necessary to provide a separate ground conductor, the number of parts can be reduced, and the configuration of the antenna can be simplified.
(C) By housing the inverted F-type antenna 1A in the door mirror case 111 of the door mirror 110, the design of the vehicle 100 is not impaired.
(D) Since high frequency signals are targeted as in the UHF band, the antenna can be made small.

[Second Embodiment]
6A and 6B show a door mirror according to a second embodiment of the present invention, in which FIG. 6A is a perspective view, and FIG. 6B is a sectional view taken along line BB of FIG. In the present embodiment, the number of feeding points is set to two, and the feeding point switching circuit is configured to switch between two feeding points. The rest is configured in the same manner as in the first embodiment.

  The inverted F-type antenna 1B according to the present embodiment uses the metal film 112b of the reflecting mirror 112 as a ground, and short-circuits the flat radiation conductor 2, the base end of the radiation conductor 2, and the metal film 112b. A conductor 3 and feeding points 4B and 4C arranged at different distances L2 and L3 from the short-circuit conductor 3 of the radiation conductor 2 are configured. The feeding point 4B arranged at a position closest to the short-circuit conductor 3 is for a low frequency (for example, 470 to 550 MHz) and a medium frequency (for example, 550 to 630 MHz), and is at a position farthest from the short-circuit conductor 3. The disposed feeding point 4C is for high frequency (for example, 630 to 710 MHz).

FIG. 7 shows the feed point switching circuit 12B of the present embodiment. This feeding point switching circuit 12B
The first comparator 120 that compares the input voltage to the + input terminal 120a and the reference voltage (−2V) to the −input terminal 120b, the input voltage to the + input terminal 121a and the reference voltage to the −input terminal 121b ( −3V), and a NOT circuit 121 having an input connected to the output terminal 120c of the first comparator 120.

  Further, in the feed point switching circuit 12B, switches 124B and 124C similar to those shown in FIG. 4B are connected between the central conductor of the coaxial cable 17 and the feed points 4B and 4C, respectively. The output terminal 121c of the second comparator 121 is connected to the control terminal 125c, and the output of the NOT circuit 122 is connected to the control terminal 125c of the switch 124C.

(Operation of Second Embodiment)
Next, the operation of the second embodiment will be described. When the user operates the remote controller 15 to select a channel, the remote controller 15 transmits a channel selection signal to the TV tuner 14 by infrared rays. The TV tuner 14 transmits a channel selection signal to the feed point switching circuit 12A via the high-frequency amplifier 13 by the signal cable 18. The feed point switching circuit 12A feeds power to the corresponding feed points 4B and 4C based on the channel selection signal.

  For example, when a 4V selection signal is output to the feed point switching circuit 12B, the first comparator 1201 compares the 4V selection signal with the 2V reference voltage, and the selection signal is higher than the 2V reference voltage. A level signal is output. The second comparator 121 compares the 4V selection signal with the 3V reference voltage, and outputs an H level signal because the selection signal is higher than the 3V reference voltage. Since the output of the NOT circuit 122 is at L level, the H level output signal of the second comparator 121 is supplied to the control terminal 125c of the low frequency and medium frequency switch 124B, and the input terminal 125a of the switch 124B The output terminal 125b becomes conductive.

  When the 1V selection signal is output to the feed point switching circuit 12B, the first comparator 120 compares the 1V selection signal with the 2V reference voltage, and the selection signal is lower than the 2V reference voltage. A level signal is output. The second comparator 121 compares the 1V selection signal with the 3V reference voltage, and outputs an L level signal because the selection signal is lower than the 3V reference voltage. For this reason, the output of the NOT circuit 122 becomes H level, this H level signal is output to the control terminal 125c of the high frequency switch 124C, and the input terminal 125a and the output terminal 125b of the switch 124C become conductive.

(Effect of the second embodiment)
According to the second embodiment, the band of the inverted F antenna can be widened by switching the feeding points 4B and 4C according to the frequency of the high-frequency signal to be communicated. In addition, the antenna can be reduced in size as in the first embodiment.

[Other embodiments]
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention. For example, the combination of the components between the embodiments can be arbitrarily performed.

  For example, in the above embodiment, the case where the inverted F-type antenna is installed on the door mirror has been described, but a fender mirror, a room mirror, or another mirror may be used.

  In the above embodiment, an inverted F antenna has been described. However, the present invention can also be applied to other antennas such as a microstrip antenna.

  In the above-described embodiment, the case of receiving UHF band radio waves has been described. However, GPS radio waves may be received.

  In the above embodiment, the case of receiving radio waves has been described. However, the present invention can also be applied to the case of transmitting and receiving radio waves.

  In the above embodiment, the switch 124 is configured in a series type using a PIN diode, but may be a shunt type using a PIN diode, or may be configured by a GaAsFET and a resistance element. You may comprise by switching elements, such as a PN junction diode, JFET, MOSFET, BJT, a capacitor, a resistance element, and a choke coil.

1 is a perspective view showing an external appearance of a vehicle to which a wireless communication apparatus according to a first embodiment of the present invention is applied. The door mirror which concerns on 1st Embodiment is shown, (a) is a perspective view, (b) is the sectional view on the AA line of (a). It is a block diagram of the radio | wireless communication apparatus which concerns on 1st Embodiment. It is a circuit diagram of the feed point switching circuit according to the first embodiment. It is a figure which shows the receiving characteristic of the inverted F type antenna which concerns on 1st Embodiment. The door mirror which concerns on the 2nd Embodiment of this invention is shown, (a) is a perspective view, (b) is the BB sectional drawing of (a). It is a circuit diagram of the feed point switching circuit according to the second embodiment.

Explanation of symbols

1A, 1B Inverted F antenna 2 Radiation conductor 3 Short-circuit conductors 4A, 4B, 4C Feed point 10 Wireless communication device 11 Circuit boards 12A, 12B Feed point switching circuit 13 High frequency amplifier 14 TV tuner 15 Remote control 16 TV monitor 17 Coaxial cable 17a Outside Conductor 17b Solder 17c Central conductor 18 Signal cable 19 Speaker 100 Vehicle 101 Front door 102 Windshield 103 Room mirror 110 Door mirror 111 Door mirror case 112 Reflector 112a Substrate 112b Metal film 120, 121 Comparator 120a, 121a + Input terminals 120b, 121b -Input Terminal 120c, 121c Output terminal 122 NOT circuit 123 Ex-OR circuit 124A-124C Switch 125a Input terminal 125b Output terminal 125c Control terminal L1, L2, L3 Short circuit Distance from body to feeding point

Claims (14)

A radiation conductor;
An antenna comprising a plurality of feeding points provided on the radiation conductor.   The antenna according to claim 1, wherein the antenna is attached to a vehicle.   The antenna according to claim 1, wherein the antenna is housed in a mirror of a vehicle.   The antenna according to claim 1, wherein the radiating conductor receives a UHF band television signal. A radiation conductor;
A grounding conductor disposed opposite the radiation conductor;
A short-circuit conductor connecting the radiation conductor and the ground conductor;
An antenna comprising: a plurality of feeding points arranged at different distances from the short-circuit conductor. The radiation conductor, the ground conductor, the short-circuit conductor, and the plurality of feeding points are accommodated in a vehicle mirror,
The antenna according to claim 5, wherein the ground conductor is a conductive reflector of the mirror.   6. The antenna according to claim 5, wherein the radiation conductor, the ground conductor, the short-circuit conductor, and the plurality of feeding points constitute an inverted F-type antenna. A radiation conductor and an antenna having a plurality of feed points provided on the radiation conductor;
A radio communication apparatus comprising: a switching circuit that switches the plurality of feeding points of the antenna based on a selection signal and feeds the radiation conductor through the switched feeding points.   The wireless communication apparatus according to claim 8, wherein the wireless communication apparatus is installed in a vehicle.   The wireless communication apparatus according to claim 8, wherein the antenna is housed in a mirror of a vehicle.   9. The wireless communication apparatus according to claim 8, wherein the antenna receives a UHF band television signal. A radiation conductor, a ground conductor disposed opposite to the radiation conductor, a short-circuit conductor connecting the radiation conductor and the ground conductor, and an antenna including a plurality of feeding points disposed at different distances from the short-circuit conductor; ,
A radio communication apparatus comprising: a switching circuit that switches the plurality of feeding points of the antenna based on a selection signal and feeds the radiation conductor through the switched feeding points. The antenna is housed in a vehicle mirror,
The wireless communication apparatus according to claim 12, wherein the ground conductor is a conductive reflector of the mirror.   The wireless communication apparatus according to claim 12, wherein the antenna is an inverted F-type antenna.

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