Slot antenna

Abstract

To eliminate noise emitted from an electronic device inside a vehicle.SOLUTION: A slot antenna according to the present invention includes a slot, which is an elongated opening provided in a conductor that constitutes an exterior panel of a vehicle, and a series resonant circuit or a parallel resonant circuit that is arranged such that the slot is short-circuited in a short direction midway along a longer direction of the slot, and the resonant frequency of the series resonant circuit or the parallel resonant circuit matches the noise frequency emitted by electronic equipment installed inside the vehicle.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The disclosed embodiments relate to a slot antenna. [Background technology]

[0002] Conventionally, there is an antenna with a resonant circuit in a slot. Patent Document 1 discloses a technique for artificially changing the slot length by providing a plurality of resonant circuits with different resonant frequencies in the slot and shorting the slot at each resonant frequency. With this technique, it is possible to dynamically change the frequency to be received at each resonant frequency. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-32303 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the technology of Patent Document 1 does not assume the removal of noise emitted from electronic devices inside the vehicle. For example, when an opening in the outer panel of a vehicle is used as a slot, there is a problem that noise emitted from electronic devices inside the vehicle resonates at the opening, resulting in noise contamination.

[0005] The present invention has been made in consideration of the above, and has an object to provide a slot antenna that can remove noise emitted from electronic devices inside a vehicle. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the slot antenna of the present invention has a slot, which is an elongated opening provided in a conductor that constitutes the outer panel of a vehicle, and a series resonant circuit or a parallel resonant circuit that is arranged so that the slot is short-circuited in the short direction midway along the longitudinal direction of the slot, and the resonant frequency of the series resonant circuit or the parallel resonant circuit matches the noise frequency emitted by electronic equipment installed inside the vehicle. Effect of the Invention

[0007] According to the present invention, it is possible to remove noise emitted from electronic devices inside a vehicle. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing the mounting position of a slot antenna. [Diagram 2] FIG. 2 is a schematic diagram of a slot antenna. [Diagram 3] FIG. 3 is a schematic diagram showing the relationship between the resonant frequency and the impedance. [Figure 4] FIG. 4 is a schematic diagram showing the relationship between the resonant circuit and the slot length. [Diagram 5] FIG. 5 is a diagram illustrating an example of frequency characteristics. [Figure 6] FIG. 6 is a schematic diagram showing the relationship between the resonant circuit and the slot length. [Figure 7] FIG. 7 is a diagram illustrating an example of frequency characteristics. [Figure 8] FIG. 8 is a schematic diagram showing another example of the arrangement of the resonant circuit. [Figure 9] FIG. 9 is a diagram showing an example of frequency characteristics in another arrangement example. [Figure 10] FIG. 10 is a schematic diagram showing a modified example of the slot antenna. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the slot antenna disclosed in the present application will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments described below.

[0010] 1 is a diagram showing a mounting position of a slot antenna. As shown in FIG. 1, a slot antenna 1 according to an embodiment is mounted on a vehicle C. The slot antenna 1 is mounted on a roof R of the vehicle C.

[0011] The frequency band of the radio waves received by the slot antenna 1 is, for example, the VHF band (30 to 300 MHz) or the UHF band (300 MHz to 3000 MHz), which includes broadcast waves such as FM (Frequency Modulation) radio broadcasts, DAB (Digital Audio Broadcast), and DTV (Digital TeleVision).

[0012] In addition, in the following figures including Fig. 1, three orthogonal coordinate axes are shown. Specifically, the X-axis corresponds to the traveling direction (front-rear direction) of the vehicle C, with the positive side defined as the rear and the negative side defined as the front. The Y-axis corresponds to the width direction of the vehicle C, with the positive side defined as the right side of the vehicle and the negative side defined as the left side of the vehicle. The Z-axis corresponds to the height direction of the vehicle C, with the positive side defined as the upper side and the negative side defined as the lower side.

[0013] Next, an overview of the slot antenna 1 according to the embodiment will be described with reference to Fig. 2. Fig. 2 is a schematic diagram of the slot antenna 1. As shown in Fig. 2, the slot antenna 1 according to the embodiment includes a slot 200.

[0014] The slot 200 is an opening provided in the metal plate 500 constituting the outer plate of the vehicle C. The slot 200 functions as a slot for receiving radio waves from the outside. As shown in Fig. 2, the slot 200 is an elongated opening with the Y-axis direction being the longitudinal direction and the X-axis direction being the lateral direction.

[0015] However, since such a slot antenna 1 is installed inside the roof R of the vehicle C, there is a problem that unwanted radio waves generated inside the vehicle cabin enter through the slot 200 and mix with the received signal as noise.

[0016] More specifically, beat noise having a strong peak in a narrow frequency band emitted from electronic devices (for example, an inverter, a DC-DC converter, etc.) installed inside the vehicle is excited in the slot 200 and becomes noise.

[0017] To address this issue, the slot antenna 1 according to the embodiment includes a resonant circuit Z that is provided midway along the length of the slot 200 so that the slot 200 is short-circuited in the width direction.

[0018] The resonant circuit Z is composed of a coil and a capacitor, and is either a series resonant circuit or a parallel resonant circuit. Note that a series resonant circuit is a circuit in which a coil and a capacitor are connected in series, and a parallel resonant circuit is a circuit in which a coil and a capacitor are connected in parallel.

[0019] Here, the relationship between the resonant frequency and the impedance in the series resonant circuit and the parallel resonant circuit will be described with reference to Fig. 3. Fig. 3 is a schematic diagram showing the relationship between the resonant frequency and the impedance.

[0020] In Fig. 3, the vertical axis represents impedance and the horizontal axis represents frequency. As shown in Fig. 3, in a series resonant circuit, the impedance is lowest at a resonant frequency f0, and the impedance gradually increases as the frequency moves away from the resonant frequency f0. Therefore, when the resonant circuit Z is a series resonant circuit, the slot 200 is short-circuited in the short direction at the resonant frequency f0.

[0021] In addition, in a parallel resonant circuit, the impedance is highest at the resonant frequency f0, and the impedance gradually decreases as the frequency moves away from the resonant frequency f0. Therefore, when the resonant circuit Z is a parallel resonant circuit, the short-circuit state of the slot 200 is released at the resonant frequency f0.

[0022] That is, when the resonant circuit Z is a series resonant circuit, by matching the resonant frequency f0 with the noise frequency, the slot 200 is short-circuited through the series resonant circuit at the noise frequency.

[0023] Furthermore, when the resonant circuit Z is a parallel resonant circuit, the short circuit in the parallel resonant circuit of the slot 200 is released at the noise frequency by matching the resonant frequency f0 with the noise frequency. That is, when the resonant circuit Z is a series resonant circuit, the slot 200 is short-circuited at the noise frequency, and the slot length is shortened. When the resonant circuit Z is a parallel resonant circuit, the short circuit in the slot 200 is released at the noise frequency, and the slot length is lengthened.

[0024] In this manner, the slot antenna 1 according to the embodiment changes the short-circuit state of the slot 200 by the resonant circuit Z, thereby substantially changing the slot length. As a result, the slot antenna 1 according to the embodiment can cut noise emitted from electronic devices inside the vehicle.

[0025] Next, the relationship between the resonant circuit Z and the slot length will be described with reference to Fig. 4 and Fig. 5. Fig. 4 is a schematic diagram showing the relationship between the resonant circuit Z and the slot length. Fig. 5 is a diagram showing an example of frequency characteristics.

[0026] 4, when the resonant circuit Z is a series resonant circuit Zs, and the slot length of the entire slot 200 is L1, when the series resonant circuit Zs resonates, the slot 200 is short-circuited in the short direction by the series resonant circuit Zs. Therefore, the slot length is L2, which is the length from the end of the slot 200 on the feed point P side to the series resonant circuit Zs.

[0027] As shown in the upper part of FIG. 5, it is assumed that, at slot length L1, frequency characteristics C1 have a maximum at peak frequency f1, and, at slot length L2, frequency characteristics C2 have a maximum at peak frequency f2.

[0028] The relationship between the slot length L and the frequency characteristic C is that the longer the slot length, the lower the peak frequency. As shown in the upper part of Fig. 5, the noise N is a peak in a narrow frequency band where the noise frequency fn is maximum.

[0029] Here, when the resonant frequency of the series resonant circuit Zs is a noise frequency fn, the slot 200 functions as an antenna with frequency characteristics C1 for the noise frequency fn, and functions as an antenna with frequency characteristics C2 for other frequencies.

[0030] Therefore, at the noise frequency fn, the frequency characteristic of the slot 200 decreases from the frequency characteristic C1 to the frequency characteristic C2. This enables the slot antenna 1 to remove the noise N at the noise frequency fn.

[0031] Also, a series resonant circuit Zs having a plurality of resonant frequencies may be provided in the slot 200, and each of the plurality of resonant frequencies may be set to coincide with a noise frequency. In this case, the slot 200 has a frequency characteristic that decreases from a frequency characteristic C1 to a frequency characteristic C2 for each noise frequency.

[0032] In other words, when a series resonant circuit Zs having multiple resonant frequencies is provided in the slot 200, the noise N2 and noise N3 corresponding to each of the multiple noise frequencies can be cut by matching each resonant frequency with a noise frequency.

[0033] Next, a case where the resonant circuit Z is a parallel resonant circuit will be described with reference to Fig. 6 and Fig. 7. Fig. 6 is a schematic diagram showing the relationship between the resonant circuit Z and the slot length. Fig. 7 is a diagram showing an example of frequency characteristics.

[0034] 6, in the case where a parallel resonant circuit Zp is provided in the slot 200, when the parallel resonant circuit Zp resonates, the parallel resonant circuit Zp releases the short circuit of the slot 200. Therefore, in the case where the resonant frequency of the parallel resonant circuit Zp is the noise frequency fn, the slot 200 functions as an antenna with a slot length L2 at the noise frequency fn, and functions as an antenna with a slot length L1 at other frequencies.

[0035] Therefore, the area of ​​the slot 200 outside the parallel resonant circuit Zp (the area farther from the feed point P than the parallel resonant circuit Zp) is an area that effectively functions as the slot 200 when the parallel resonant circuit Zp resonates.

[0036] Also, as shown in the upper part of FIG. 7, it is assumed that, at slot length L1, frequency characteristics C1 have a maximum at peak frequency f1, and, at slot length L2, frequency characteristics C2 have a maximum at peak frequency f2.

[0037] At a noise frequency fn which is the resonant frequency of the parallel resonant circuit Zp, the slot length increases from slot length L2 to slot length L1, and the frequency characteristic of the slot 200 for the noise frequency fn decreases from frequency characteristic C2 to frequency characteristic C1. This enables the slot antenna 1 to remove the noise N of the noise frequency fn.

[0038] Next, another example of the arrangement of the resonant circuit Z will be described with reference to Fig. 8 and Fig. 9. Fig. 8 is a schematic diagram showing another example of the arrangement of the resonant circuit Z. Fig. 9 is a diagram showing an example of frequency characteristics in the other example of the arrangement.

[0039] 8, a parallel resonant circuit Zp, a series resonant circuit Zs1, and a series resonant circuit Zs2 are arranged in the slot 200 from the longer slot length side. That is, the slot antenna 1 shown in FIG 6 is provided with at least one series resonant circuit (Zs1 and Zs2) on the feed point P side of the parallel resonant circuit Zp.

[0040] In this case, the overall slot length of slot 200 is slot length L1, the slot length when short-circuited by parallel resonant circuit Zp is slot length L2, the slot length when short-circuited by series resonant circuit Zs1 is slot length L3, and the slot length when short-circuited by series resonant circuit Zs2 is slot length L4.

[0041] As shown in FIG. 9, the frequency characteristics for slot lengths L1 to L4 are frequency characteristics C1 to C4, respectively, the resonant frequency of the series resonant circuit Zs1 is a noise frequency fn1, the resonant frequency of the series resonant circuit Zs2 is a noise frequency fn2, and the resonant frequency of the parallel resonant circuit Zp is a noise frequency fn3.

[0042] In this case, at frequencies other than the noise frequency fn3, the slot 200 is short-circuited by the parallel resonant circuit Zp, so that the normal slot length is based on the slot length L2, and the frequency characteristic is the frequency characteristic C2 corresponding to the slot length L2.

[0043] At the noise frequency fn1, the slot 200 is short-circuited by the series resonant circuit Zs1, the slot length is shortened from the slot length L2 to the slot length L3, and the frequency characteristic for the noise frequency fn1 is attenuated from the frequency characteristic C2 to the frequency characteristic C3. In this case, the noise of the noise frequency fn1 can be cut.

[0044] At the noise frequency fn2, the slot length is shortened from slot length L2 to slot length L4, and the frequency characteristic for the noise frequency fn2 is attenuated from frequency characteristic C2 to frequency characteristic C4. In this case, the noise at the noise frequency fn2 can be cut.

[0045] On the other hand, at the noise frequency fn3, the parallel resonant circuit Zp resonates, and the slot length increases from slot length L2 to slot length L1. Therefore, the frequency characteristic for the noise frequency fn3 attenuates from frequency characteristic C2 to frequency characteristic C1. In this case, the noise of the noise frequency fn3 can be cut.

[0046] In this way, by providing a plurality of series resonant circuits or parallel resonant circuits with different resonant frequencies in the slot 200, a plurality of noises with different frequencies can be cut.

[0047] Although the case where there is one parallel resonant circuit Zp has been described here, a pair of parallel resonant circuits may be provided on both sides of the feed point P. That is, in the example of FIG. 9, one parallel resonant circuit Zp may be added to the left of the feed point P.

[0048] In the slot 200, the area outside the pair of parallel resonant circuits Zp is an area that is effective only when each parallel resonant circuit Zp resonates, and by providing a series resonant circuit Zs closer to the power supply point P than the parallel resonant circuits Zp, the series resonant circuit Zs can be effectively used to remove noise.

[0049] Next, a modified example of the slot antenna 1 will be described with reference to Fig. 10. Fig. 10 is a schematic diagram showing a modified example of the slot antenna 1. As shown in Fig. 10, two conductive plates 100 are provided in a slot 200.

[0050] The two conductive plates 100 are provided so as to form an L-shaped slit 210 in a top view, and a gap 220 is formed between the conductive plates 100 and the metal plate 500. The slit 210 and the gap 220 also function as a slot 200.

[0051] Furthermore, the two conductive plates 100 are each fixed to a metal plate 500 by a metal bracket 110, and the conductive plates 100 and the metal plate 500 are electrically connected to each other by the bracket 110. Furthermore, the two conductive plates 100 have feeding points P on both sides of the slit 210, and power is fed through the feeding points P.

[0052] 10, in the slot antenna 1 according to the modified example, a resonant circuit Z is provided in the slit 210 or the gap 220. In this case, the resonant circuit Z is a series resonant circuit, and the resonant frequency is made to coincide with the noise frequency, so that both ends of the slot 200 at the feeding point P are shorted at the resonant frequency.

[0053] As a result, radio waves are not excited in the slot 200, so that the slot 200 becomes insensitive to noise and can cut out the noise.

[0054] As described above, the slot antenna 1 according to the embodiment includes a slot 200, which is an elongated opening provided in a conductor constituting the outer plate of a vehicle C, and a series resonant circuit or a parallel resonant circuit consisting of a coil and a capacitor, arranged so that the slot 200 is short-circuited in the short direction midway along the longitudinal direction of the slot 200.

[0055] Therefore, the slot antenna 1 according to the embodiment can change the slot length by using a series resonant circuit or a parallel resonant circuit, and can therefore remove noise that is mixed into the received broadcast waves.

[0056] In the above embodiment, the slot antenna 1 is disposed on the roof R of the vehicle, but the present invention is not limited to this. That is, the present invention may be applied to a slot antenna disposed at a position where beat noise having a strong peak in a narrow frequency band occurs. In this case, for example, the present invention may be applied to a device other than a vehicle, such as a mobile phone.

[0057] Further advantages and modifications may readily occur to those skilled in the art. Thus, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and equivalents thereof. [Explanation of symbols]

[0058] 1 Slot Antenna 100 Conductor plate 110 Bracket 200 Slots 210 Slit 220 Gap 500 Sheet Metal C Vehicle P Feeding point Rear roof Z resonant circuit Zp parallel resonant circuit Zs series resonant circuit

Claims

1. A slot is an elongated opening provided in a conductor constituting an outer panel of a vehicle; A series resonant circuit or a parallel resonant circuit is provided in the middle of the slot in the longitudinal direction so that the slot is short-circuited in the lateral direction, The resonant frequency of the series resonant circuit or the parallel resonant circuit is The frequency of the noise emitted by the electronic equipment installed inside the vehicle is the same. Slot antenna.

2. the series resonant circuit or the parallel resonant circuit has a plurality of resonant frequencies; The plurality of resonant frequencies are Each of the plurality of noise frequencies corresponds to 2. The slot antenna according to claim 1.

3. A plurality of the series resonant circuits or the parallel resonant circuits having different resonant frequencies are provided at different positions in the longitudinal direction of the slot, The resonant frequency of the series resonant circuit or the parallel resonant circuit is Each of the plurality of noise frequencies corresponds to 2. The slot antenna according to claim 1.

4. The slot includes: One of the parallel resonant circuits and at least one of the series resonant circuits are provided on the power supply point side of the parallel resonant circuit, The resonant frequencies of the parallel resonant circuit and the series resonant circuit are Each of the plurality of noise frequencies corresponds to 2. The slot antenna according to claim 1.

5. The slot includes: A pair of the parallel resonant circuits is provided on both sides of a power supply point, The resonant frequency of each of the parallel resonant circuits is Each of the plurality of noise frequencies corresponds to 2. The slot antenna according to claim 1.

6. The slot includes: At least one of the series resonant circuits is provided between the pair of the parallel resonant circuits, The resonant frequencies of the parallel resonant circuit and the series resonant circuit are Each of the plurality of noise frequencies corresponds to 6. The slot antenna according to claim 5.

7. Within the slot: A conductor plate is provided which is electrically connected to the outer plate, When at least a part of the slit in the conductive plate and the gap between the conductive plate and the conductor are combined with the opening to form the slot, The series resonant circuit or the parallel resonant circuit is provided midway through the slit or the gap.

2. The slot antenna according to claim 1.

Images