JP2004248191A - Strap antenna and radio device provided with same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To expand a receiving frequency band without requiring a sensitivity adjusting operation in a strap antenna. <P>SOLUTION: A strap antenna 2 is composed of a balun 4 for converting a balanced mode into an unbalanced mode, a dipole antenna 8 that is connected to a balanced mode side terminal of the balun 4 and resonated in 200 MHz, a pair of loading means 6, 6 of which one terminal is connected to both terminals of the dipole antenna 8, and a lead wire 10 connected between anti-dipole antenna side terminals of the loading means 6, 6. A pair of loading means 6, 6 are then equipped with loading coils Lc, Lc, and the loading coils Lc, Lc become high impedance to be substantially electrically disconnected for a signal of 200 MHz and become low impedance to be substantially electrically connected for a signal of 100 MHz. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a strap antenna, and more particularly, to a strap antenna capable of obtaining high reception sensitivity over a wide frequency band without performing a sensitivity adjustment operation or a reception frequency switching operation, and a wireless device using the same.
[0002]
[Prior art]
Radio antennas that receive high-frequency radio waves, such as those that use earphones as they are or those that have conductor wires arranged inside the housing of the radio, have been used in the past. It is difficult to obtain sensitivity, and for example, a loop antenna introduced in Japanese Patent Application Laid-Open No. H10-84209 has been developed. In this type of antenna, a loop antenna is attached to a necklace of a small wireless device, and an inductance element is connected to the loop antenna in parallel so that an opening surface of the loop antenna is perpendicular to a human body surface. .
[0003]
[Problems to be solved by the invention]
By the way, for example, when a television broadcast is received, a strap-type neck-hung type antenna as introduced in the above-mentioned Japanese Patent Application Laid-Open No. 10-84209, etc. There is a problem that it is difficult to secure a sufficient receiving sensitivity over the whole area.
That is, a so-called portable liquid crystal TV (television receiver) needs to receive a very wide band high frequency signal of 97 to 770 MHz. Specifically, in the case of the frequency band used for television broadcasting in Japan, the frequency used is 90 to 108 MHz (1 to 3 cH) and 170 to 222 MHz (4 to 12 cH) in the VHF band, and 470 to 770 MHz (13 in the UHF band). To 62 cH) is the operating frequency.
It was difficult to obtain a sufficiently high reception sensitivity over such a wide band, and it was inevitable that a band with low reception sensitivity would occur. This is because the loop length of the loop antenna determines the reception frequency band, and the reception sensitivity of the antenna decreases for frequencies outside the band.
[0004]
For this reason, for example, a sensitivity adjusting member in which a magnetic material is movably inserted and a sensitivity adjusting member is provided, and the insertion amount of the magnetic material is adjusted according to a frequency to be received has been developed. However, according to such sensitivity adjusting means, it is necessary to perform the sensitivity adjusting operation every time the frequency to be received is switched.
[0005]
The present invention has been made to solve such a problem, and a strap antenna and a strap antenna capable of securing sufficient reception sensitivity for signals in a wide band without requiring a sensitivity adjustment operation. It is an object of the present invention to provide a wireless device using the same.
[0006]
[Means for Solving the Problems]
The strap antenna according to claim 1 has a balun for converting from a balanced mode to an unbalanced mode, and has a pair of loading coils at the ends of two conductor wires connected to terminals on the balanced mode side, between the loading coils. Is a strap antenna connected by a conductor wire, and the loading coil has a high impedance with respect to a specific frequency signal (for example, 200 MHz) higher than a preset basic frequency (for example, 100 MHz) and has a high frequency. By separating the conductor wire from the conductor wire connected to the balun, the conductor wire functions as a dipole antenna, and becomes a low impedance with respect to the signal of the fundamental frequency (for example, 100 MHz) and is connected to the balun. A conductor wire is connected between the pair of loading coils and the loading coil. Characterized in that the serial conductor wire so as to function as a loop antenna.
[0007]
Therefore, according to the strap antenna of the first aspect, the high-frequency signal can be mode-converted from the balanced mode to the unbalanced mode by the balun, and the specific frequency (for example, 200 MHz) higher than the fundamental frequency (for example, 100 MHz) can be obtained. For the signal, the loading coil becomes high impedance and is separated from the conductor wire connected to the balun, and the conductor wire can function as a U-shaped dipole antenna and resonate.
In addition, for a signal of a fundamental frequency (for example, 100 MHz), the loading coil has low impedance, and the conductor wire and a pair of loading and a conductor wire connecting the loading coil form one antenna (loop antenna). It can function and resonate.
[0008]
Therefore, an antenna (loop antenna) that resonates at a fundamental frequency (for example, 100 MHz) and further resonates at a higher harmonic (a third harmonic, for example, 300 MHz, a fifth harmonic, for example, 500 MHz, a seventh harmonic, for example, 700 MHz), An antenna (generally a dipole antenna) that resonates with a signal of a specific frequency (for example, 200 MHz) higher than a set frequency (for example, 100 MHz) and further excites its higher harmonic (a third harmonic, for example, 600 MHz) is one strap. It is constituted by an antenna, and it is possible to obtain a sensitivity characteristic with a relatively small change in reception sensitivity over a wide frequency band, and no sensitivity adjustment for the strap antenna is required to obtain the sensitivity characteristic.
Since the loading coil shortens the antenna length required for resonance at the fundamental frequency (for example, 100 MHz), the antenna can resonate with a signal having a long wavelength even if the antenna length is short. The receiving sensitivity to a signal with a low frequency can be increased without any problem. This is another advantage that cannot be ignored.
[0009]
According to a fifth aspect of the present invention, there is provided a wireless device comprising the strap antenna of the first aspect and a receiving device connected thereto.
Therefore, according to the wireless device of the fifth aspect, it is possible to enjoy the advantages of the strap antenna of the first aspect.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention basically provides, as an antenna, a balun for mode conversion from a balanced mode to an unbalanced mode, and at least one pair of loading coils at the ends of two conductor wires connected to terminals on the balanced mode side of the balun. The loading coil at the end thereof is connected by a conductor wire, but another conductor wire insulated therefrom may be connected in parallel to the conductor wire. This is because a parasitic capacitance occurs between the conductors connected in parallel with each other, and the reception frequency band can be expanded by the parasitic capacitance.
[0011]
Further, the pair of conductor wires connected to the balun and the conductor wire connecting between the loading coils may be formed by a plurality of wires so as to have conductivity and mechanical flexibility (flexibility). As its material, for example, soft copper is suitable.
[0012]
The pair of conductor wires may be configured such that the portions connected to the balun form an angle of approximately 180 ° with each other. In this case, the pair of conductor wires functions as a U-shaped dipole antenna for the signal of the specific frequency (for example, 200 MHz).
Also, the angle may be smaller than about 180 °. In this case, the pair of conductor wires functions as a U-shaped dipole antenna for the signal of the specific frequency (for example, 200 MHz).
[0013]
【Example】
Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.
FIGS. 1A and 1B show a first embodiment of the strap antenna of the present invention, wherein FIG. 1A is a configuration diagram and FIG. 1B is a circuit diagram of the antenna. In the drawing, reference numeral 2 denotes a strap antenna (a first embodiment of the strap antenna of the present invention), which includes a balun 4, a conductor wire 6 connected to the balun 4, and a pair of terminals on the opposite balun side of the conductor wire 6. It comprises a pair of loading boxes (loading means) 8 connected to each other, and a conductor wire 10 connected between terminals of the loading box 8 on the side opposite to the balun. The conductor wires 10 and 6 are made of a plurality of wires having conductivity, mechanical flexibility, and the like, and are made of, for example, soft copper. Further, the lead wire may be a lit wire which is insulated from each other.
[0014]
The balun 4 converts the mode from the balanced mode to the non-balanced mode and converts the impedance. The balun 4 has a pair of conductor wires 6 connected to terminals on the balanced portion side and a receiving circuit (liquid crystal TV) connected to the terminals on the unbalanced portion side. Circuit) is connected. The balun 4 specifically performs mode conversion and impedance conversion from a balanced 200Ω to an unbalanced 75Ω.
As shown in FIG. 1A, each of the conductor wires 6 has an antenna length (one-sided antenna length) of about 37 cm, and functions as a U-type dipole antenna that resonates with a 200 MHz high-frequency signal. Excitation to waves (3rd harmonic, 5th harmonic, 7th harmonic).
[0015]
In the loading box 8, one end of the loading coil Lc is connected to the conductor wire 6 and the other end is connected to the conductor wire 10, respectively. The conductor wire 10 forms a part of the loop antenna and also plays an important role of allowing the strap antenna 2 to be hung on the neck.
[0016]
As shown by a two-dot chain line in FIG. 1B, another conductive wire 10a may be connected in parallel to the conductive wire 10, and may be used as one strap. By doing so, a parasitic capacitance is generated between the conductors 10 and 10a connected in parallel to each other, and the reception frequency band can be expanded by the parasitic capacitance.
[0017]
Each loading coil Lc has an inductance of 3.0 μH at a frequency of 100 MHz, for example. The inductance of the coil Lc has no shield. FIG. 2 shows the frequency dependence of the inductance of the loading coil Lc. Then, as shown in FIG. 3, the insertion loss is maximized at 200 MHz. Specifically, at 200 MHz, the insertion loss reaches 50 dB.
[0018]
Therefore, it can be said that the impedance becomes substantially high so as to perform high-frequency separation. By the way, at 100 MHz, the insertion loss is only about 10 dB, and the impedance is only low impedance that cannot be separated at high frequencies.
Reference numeral 12 denotes a receiving circuit (receiving device), whose input terminal is connected to an unbalanced side terminal of the balun 4. Reference numeral 14 denotes a wireless device having the receiving circuit 12, for example, a liquid crystal TV (television receiver).
[0019]
The strap antenna 2 has both a 100 MHz resonance loop pole antenna and a 200 MHz resonance U-type dipole antenna, that is, a function as a 100 MHz resonance loop antenna and a function as a 200 MHz resonance U-type dipole antenna.
First, the function as a 100 MHz resonance loop antenna will be described. As shown in FIG. 3, the loading coil Lc has a small insertion loss of about 10 dB (gain = −10 dB) for a signal of a frequency of 100 MHz. In addition, the loading coil Lc and the conductor wire 6 cannot be separated at a high frequency.
[0020]
Therefore, for a signal having a frequency of 100 MHz, the loop antenna including the conductor wires 6 and 6, the loading coils Lc and Lc, and the conductor 10 functions as a reception antenna and resonates.
The loading coil has a function of shortening the length of the resonant antenna, and plays a role in increasing the receiving sensitivity to a signal of a low frequency even if the antenna length is short. That is, since the loop antenna resonates with a high-frequency signal having a length of λ (wavelength) to 1.5λ, the antenna length required to resonate at 100 MHz usually becomes as long as 3 meters. This is not practical for a portable wireless device (liquid crystal TV).
[0021]
However, this strap antenna 2 has a loading coil Lc, and can receive signals of a low frequency with sufficient sensitivity even if the antenna length is short due to the antenna length shortening function of the loading coil Lc. More specifically, in the present embodiment, the conductor wire 6 has a one-sided antenna length of 37 cm, the length of the conductor 10, that is, the length of the portion to be turned around the back of the neck is 40 cm. The part connected to 4 opens at about 180 degrees, and the interval between the parts opened at 180 degrees is 10 cm.
[0022]
In this case, the wavelength of the high-frequency signal having a loop length of 100 MHz is 1.13λ, and resonates with the signal. Incidentally, the loop antenna has a feature that the gain increases as the effective length is longer than λ, that is, up to about 1.5λ. Therefore, in this embodiment, the effective length of the signal wavelength of 1.13λ is increased. Because of the length, the gain is considerably increased, that is, the receiving sensitivity is increased.
[0023]
Therefore, a 100 MHz resonant loop antenna having a practical antenna length is formed, and a loop antenna that resonates at a frequency of 100 MHz and excites to a harmonic (100, 550, 710) of 100 MHz is functioned. You do it.
[0024]
Next, a function as a 200 MHz resonance U-type dipole antenna will be described. As shown in FIG. 3, each of the loading coils Lc has an insertion loss of as high as 50 dB (gain: −50 dB) with respect to a signal having a frequency of 200 MHz. Separate from the conductor wire 6. That is, only the conductor wire 6 functions as an antenna (generally, a dipole antenna). The length of one antenna is 37 cm, which resonates with a signal having a frequency of 200 MHz. Therefore, it resonates with a 200 MHz frequency signal and excites to a 200 MHz harmonic (3rd harmonic, 5th harmonic, 7th harmonic).
In the case of a dipole antenna, the actual resonance wavelength tends to be slightly shorter than the calculated value of the resonance wavelength for each antenna length.
[0025]
As described above, according to the present strap antenna 2, the loading coil Lc having a large insertion loss with respect to a signal having a frequency of 200 MHz separates the loading coil Lc from the conductor wire 6, so that the 200 MHz resonance U-type is used. Functions as a dipole antenna.
The loading coil Lc having an inductance of 3.0 μH has a small insertion loss with respect to a signal having a frequency of 100 MHz, and the conductor wire 6 is integrated with the loading coil Lc and the conductor 10 at a high frequency. , The loading coil Lc and the conductor 10 constitute a loop antenna. Then, even if the antenna length is short due to the shortening of the antenna length by the loading coil Lc, the antenna can resonate with a high frequency signal of a relatively low frequency of 100 MHz. Therefore, it also functions as a 100 MHz resonance loop antenna.
[0026]
As described above, the present strap antenna 2 functions as a 100 MHz resonance loop antenna or a 200 MHz resonance dipole antenna without performing any sensitivity adjustment operation, so that the strap antenna 2 resonates at 100 MHz and 200 MHz, and a harmonic of the 100 MHz and 200 MHz. Sufficiently high reception sensitivity can be obtained over a wide band that sufficiently covers the frequency band used for television broadcasting, which excites waves (3 times, 5 times, and 7 times).
[0027]
In this strap antenna 2, if the angle of the part of the pair of conductor wires 6, 6 connected to the balanced side terminal of the balun 4 is 180 ° or less (however, it is necessary to be 30 ° or more), 100 MHz An antenna in which a resonance loop pole antenna and a 200 MHz resonance V-type dipole antenna coexist.
[0028]
【The invention's effect】
According to the strap antenna of the first aspect, a high-frequency signal can be mode-converted from a balanced mode to an unbalanced mode by a balun, and a signal having a specific frequency (for example, 200 MHz) higher than a fundamental frequency (for example, 100 MHz) can be obtained. On the other hand, the loading coil becomes high impedance and the loading coil is separated from the conductor wire, and the separated conductor wire functions as a dipole antenna and resonates.
[0029]
For a signal of a fundamental frequency (for example, 100 MHz), the loading coil has low impedance so that a conductor wire, a pair of loading coils, and a conductive wire connected between the pair of loading coils on the opposite balun side terminals. Function as one antenna (loop antenna) and resonate.
[0030]
Accordingly, an antenna (loop antenna) that resonates at a fundamental frequency (eg, 100 MHz) and excites its harmonics (3rd harmonic, eg, 300 MHz, 5th harmonic, eg, 500 MHz, 7th harmonic, eg, 700 MHz), and a fundamental frequency An antenna (generally a dipole antenna) that resonates with a signal of a specific frequency (for example, 200 MHz) higher than (for example, 100 MHz) and excites a higher harmonic (a third harmonic, for example, 600 MHz or the like) is constituted by one strap antenna. Thus, it is possible to obtain sensitivity characteristics with a relatively small change in reception sensitivity over a wide frequency band, and no sensitivity adjustment for the strap antenna is required to obtain the sensitivity characteristics.
Since the loading coil shortens the antenna length required for resonance, it can resonate with a signal having a long wavelength even if the antenna length is short. Therefore, it is possible to increase the receiving sensitivity to a signal with a low frequency without lengthening the antenna.
[0031]
According to the strap antenna of the second aspect, since another conductor wire is connected in parallel to the conductor wire connected between the loading coil and the opposite terminal of the pair of loading means, they are connected in parallel with each other. Parasitic capacitance occurs between the conductors, and the reception frequency band can be expanded (smoothed) by the parasitic capacitance.
[0032]
According to the strap antenna of the third aspect, the portions of the two conductor wires connected to the balun form approximately 180 ° with each other, so that the two signal wires for the specific frequency signal Functions as a U-shaped dipole antenna, so that a loop-pole antenna that resonates at the fundamental frequency and a U-shaped dipole antenna that resonates at the specific frequency coexist.
[0033]
According to the strap antenna of the fourth aspect, the portions of the two conductor wires connected to the balun form an angle of less than about 180 ° with each other, so that a loop pole antenna that resonates at the fundamental frequency, The antenna coexists with the V-type dipole antenna resonating at the specific frequency.
[0034]
According to the wireless device of the fifth aspect, since the strap antenna of the first aspect is used, the advantages of the strap antenna of the first aspect can be enjoyed.
[Brief description of the drawings]
1A and 1B show one embodiment of a strap antenna of the present invention, wherein FIG. 1A is a configuration diagram and FIG. 1B is a circuit diagram.
FIG. 2 is a curve diagram showing a relationship between a frequency and an inductance of a loading coil used in the embodiment.
FIG. 3 is a curve diagram showing a relationship between a frequency of a loading coil used in the above embodiment and an insertion loss.
[Explanation of symbols]
2 ... strap antenna, 4 ... balun, 6 ... conductor wire,
8. Loading means (loading box)
10, 10a ... a conductor wire connected between a pair of loading means,
12: receiving device, 14: radio, Lc: loading coil.

Claims (5)

It has a balun for converting from a balanced mode to an unbalanced mode, and a pair of loading coils is provided at the ends of two conductor wires connected to terminals on the balanced mode side of the balun, and the coils are connected by a conductor wire. A strap antenna,
The loading coil has a high impedance with respect to a specific frequency signal higher than a preset fundamental frequency, and is separated from the conductor wire connected to the balun in a high frequency manner so that the conductor wire functions as a dipole antenna. For the signal of the fundamental frequency, the conductor wire connected to the balun, the pair of loading coils, and the conductor wire portion connecting the loading coils are made to function as a loop antenna. Strap antenna to do. 2. The strap antenna according to claim 1, wherein another conductor wire insulated from the conductor wire connecting the loading coils is connected in parallel. The two conductor lines connected to the terminals of the balun on the balanced mode side form substantially 180 degrees with each other on the side connected to the terminals, and the two signal lines for the specific frequency signal. 3. The strap antenna according to claim 1, wherein the strap antenna functions as a U-shaped dipole antenna. At least portions of the two conductor wires connected to the terminals on the balanced mode side of the balun make an angle of less than about 180 ° with each other, and the angle is smaller than about 180 ° with respect to the specific frequency signal. 3. The strap antenna according to claim 1, wherein the two signal lines function as a V-type dipole antenna. A balun for converting from a balanced mode to an unbalanced mode; a pair of loading coils provided at the ends of two conductor wires connected to a terminal on the balanced mode side of the balun; the loading coils are connected by a conductor wire; The loading coil becomes a high impedance for a specific frequency signal higher than a preset fundamental frequency, and is separated from the conductor wire connected to the balun in a high frequency, and the conductor wire is used as a dipole antenna. A strap antenna for causing the conductor wire connected to the balun, the pair of loading coils, and the conductor wire portion connecting the loading coils to function as a loop antenna for the signal of the fundamental frequency. When,
A receiver in which an antenna output terminal is connected to an unbalanced mode side terminal of the balun,
A wireless device comprising:

Images