JP2001148609A - Antenna, balance/non-balance converter and receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the unintended conduction of a switch circuit for changing the valid length of an antenna element by the turning on/off of the switch circuit. SOLUTION: In a switching circuit DS5 inserted between two antenna elements 3, an input terminal Bias1 on an anode side in a diode 61 or an input terminal Bias 2 on a cathode side and a DV bias power source are selectively connected by the operation of a bias circuit. The conduction of the diode 61 can surely be prevented by the application (namely, inverse bias) of DC bias to the cathode side of the diode 61.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an antenna, a balun converter and a receiver, and more particularly, to an antenna, a balun converter and a receiver capable of receiving signals in a plurality of different frequency bands.

[0002]

2. Description of the Related Art An antenna has an antenna element length (effective length of an antenna) corresponding to a frequency band of a signal to be used. In many cases, the effective length is λ / 2 with respect to a wavelength λ of a desired frequency band. Or, it is set to be λ / 4. For this reason, a receiver that receives radio waves in two different frequency bands uses two antennas having different effective lengths according to the frequencies, and switches between them for use.

In this respect, it is convenient if the effective length of one antenna can be switched between long and short. For this purpose, conventionally, a switching circuit in which a diode and a resistor are connected in parallel is interposed between a plurality of divided antenna elements, and a DC bias power supply is connected to the feeding side of the antenna element. An antenna has been proposed (Japanese Patent Laid-Open No. 10-32417). In this conventional configuration, the diode is rendered conductive by applying a forward bias voltage to the diode with a DC bias power supply, thereby changing the effective number of antenna elements and changing the effective length of the antenna. On the other hand, a DC breaker comprising a capacitor is interposed on the power supply side with respect to the connection point between the DC bias power supply and the antenna element, thereby preventing the possibility that the bias voltage flows into the power supply side.

[0004]

However, in this conventional antenna, even when a forward bias voltage is not applied to a specific diode, when the signal level is large, the diode conducts, and unnecessary antennas become unnecessary. There is a possibility that up to the antenna element will be in a connected state. In addition, since the bias voltage always acts on the antenna element, there is a problem that the electrical characteristics of the antenna element may change over time and the signal may be distorted.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an antenna capable of reliably holding an effective number of antenna elements and preventing a bias voltage from acting on the antenna elements.

[0006]

According to a first aspect of the present invention, there is provided an antenna including a plurality of antenna elements and a switching circuit interposed between the plurality of antenna elements. A diode, a DC bias power supply, switching means for selectively connecting an anode side or a cathode side of the diode and the DC bias power supply, and a connection point between the DC bias power supply and the diode and the antenna element. And a capacitor provided in the antenna.

According to the first aspect of the present invention, since the anode side or the cathode side of the diode and the DC bias power supply are selectively connected by the switching means, the cathode side of the diode is connected to the DC bias power supply (ie, reverse bias). ) Can surely prevent conduction of the diode. Also, since the capacitor is provided between the connection point between the DC bias power supply and the diode and the antenna element, no bias voltage acts on the antenna element.

According to a second aspect of the present invention, there is provided the antenna according to the first aspect of the present invention, wherein the switching means is a circuit operated based on an operation of a manual switch.

According to the second invention, the signal frequency band of the antenna of the first invention can be switched by simple means.

According to a third aspect of the present invention, there is provided a balanced-unbalanced converter including a conversion characteristic setting member for setting a balanced-unbalanced conversion characteristic according to a reception wavelength of an antenna to be connected. This is a balance-unbalance converter provided with an effective length changing means for changing an effective length of a member.

When the length of the antenna element is changed according to the frequency band to be used as in the first invention, the impedance characteristic of the antenna changes, so that the equilibrium relationship between this and the feed line also changes. . Therefore, in the third aspect of the present invention, the effective length changing means for changing the effective length of the conversion characteristic setting member of the balanced-unbalanced converter is provided. By adjusting the conversion characteristics of the unbalanced converter, it is possible to perform proper balanced-unbalanced conversion.

According to a fourth aspect of the present invention, there is provided the balanced-unbalanced converter according to the third aspect of the present invention, wherein one end of the conversion characteristic setting member is connected to an end of the first conductor of the feed line on the antenna side. A conductor short-circuited and the other end of which is short-circuited to a second conductor of the feeder line, the first effective length of the antenna element having a first effective length corresponding to a reception wavelength, and the effective length The changing means includes a connection point separated from a short-circuit point on the antenna side in the conversion characteristic setting member by a second effective length according to a reception wavelength in a second effective length of the antenna element, A balanced-unbalanced converter, which is a switch means for selectively connecting two conductors.

According to the fourth aspect of the present invention, when the antenna element length is the first effective length, the switch means is turned off to select the first effective length of the conversion characteristic setting member. If is the second effective length, the switch means is turned on and the second effective length of the conversion characteristic setting member is selected, so that proper balance-unbalance conversion can be performed.

According to a fifth aspect of the present invention, there is provided the balun converter according to the fourth aspect of the present invention, wherein the switch means includes a diode, a DC bias power supply, an anode or cathode side of the diode and the DC bias. And a switching means for selectively connecting to a power supply.

In the fifth aspect of the present invention, the switching means of the balun converter is configured to selectively connect the anode side or the cathode side of the diode to the DC bias power supply by the switching means. And a DC bias power supply, the conduction of the diode can be reliably prevented.

A sixth aspect of the present invention is the balun converter according to the fourth or fifth aspect of the present invention, wherein the conversion characteristic setting member and the first conductor of the feeder line are short-circuited by a strip line. And the impedance matching with the antenna is performed by the strip line.

In the sixth invention, impedance matching with the antenna is performed by the strip line.
In particular, fine adjustment of the characteristic impedance can be easily performed by changing the line width of the strip line.

According to a seventh aspect of the present invention, there is provided a receiver used in connection with the antenna of the first aspect of the present invention and the baluns of the third to sixth aspects of the present invention. And a control unit that outputs an operation instruction to the switching unit of the antenna and the effective length changing unit of the balun converter according to the detected desired reception frequency band, and the control unit includes: A receiver characterized in that an effective length of the conversion characteristic setting member is changed so as to match a reception wavelength in an effective length of the antenna element.

In the seventh aspect of the present invention, when the band detecting means detects the desired receiving frequency band, the control means changes the antenna switching means and the effective length of the balun converter according to the detected desired receiving frequency band. An operation instruction is output to the means. Therefore, the effective number of antenna elements, that is, the effective length of the antenna, is selected according to the desired reception frequency band, and the balance-unbalance conversion at that time can be appropriately performed.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, antenna 1
Represents a plurality of antenna elements 3 and a switching circuit D
S5 is included, and is connected so as to branch from the balun 7 in two directions. Each of the left and right branches of the antenna 1 is configured by connecting the two antenna elements 3 by a switching circuit DS5. The base end of each branch of the antenna element 3 is connected to a balun 7 which is a balanced-unbalanced converter. Connected to one end (balanced side). A receiver 70 is connected to the other end (unbalanced side) of the balun 7 via a coaxial cable 30 which is an unbalanced feed line.

The antenna 1 is a balanced dipole antenna. The total effective length of the two antenna elements 3 directly connected to the balun 7 is LA1, and the antenna 1 further includes the antenna element 3 on the tip side of each branch. The total effective length of one antenna element 3 is LA2. These effective lengths LA1 and LA2 respectively correspond to desired reception frequency bands. That is, the effective length LA1 is 2.6G in frequency.
In order to receive automotive satellite broadcasts in the vicinity of Hz, the wavelength is set to 5.5 cm corresponding to λ _1/2 for the wavelength λ ₁ = 11 cm. The effective length LA2 is 1.6 GHz in frequency.
In order to receive a nearby GPS signal, its wavelength λ ₂ = 1
It is set in 9cm corresponding to lambda _2/2 to 8 cm.

FIG. 2 shows the inside of the switching circuit DS5 on the right side in FIG. In FIG.
The switching circuit DS5 includes a diode 61, and an input terminal Bias1 on the anode side and an input terminal Bias2 on the cathode side of the diode 61. Diode 61 and input terminals Bias1 and Bias
2, a parallel circuit including capacitors 63 and 64 and coils 65 and 66 is provided. Further, capacitors 67 and 68 are provided on the antenna element 3 side with respect to the connection point between the anode side or the cathode side of the diode 61 and the input terminals Bias1 and Bias2.

The switching circuit DS5 is configured such that the diode 61 is turned on / off by selectively applying a DC bias voltage to the input terminal Bias1 or the input terminal Bias2. That is, when a DC bias voltage is applied to the input terminal Bias1, the diode 61 is turned on or turned on, whereby the left and right antenna elements 3 in FIG. 2 are connected, and as a result, the effective length of the antenna 1 in FIG. LA2 is selected. When a DC bias voltage is applied to the input terminal Bias2, the diode 61 is turned off, thereby cutting off the conduction of the left and right antenna elements 3 in FIG. 2, and as a result, the effective length LA1 of the antenna 1 in FIG.
Is selected. The parallel circuit composed of the capacitors 63 and 64 and the coils 65 and 66 is connected to the input terminals Bias1 and Bias2 from the antenna element 3,
Alternatively, leakage of a high-frequency signal from the input terminals Bias1 and Bias2 to the antenna element 3 is prevented.

A receiver 70 is provided with a bias circuit 71 for selectively applying a DC bias voltage to the input terminals Bias1 and Bias2. This bias circuit 7
Reference numeral 1 denotes a well-known configuration including a 5 V constant voltage source (not shown), a switching element such as a transistor, and an inverter for inverting the polarity. The switching element operates to connect the input terminals Bias1 and Bias2 to each other. It is configured to selectively apply a DC bias voltage.

FIGS. 5A and 5B show a schematic configuration of the balun 7. FIG. The substrate 10 is a dielectric sheet made of a synthetic resin film having a thickness of about 100 μm. This substrate 10
On the first surface side, a line portion 12 made of a conductor layer having a thickness of about 10 to 20 μm is formed. This track section 12
Is composed of a main line portion 28 and a branch line portion 29 which is arranged substantially symmetrically with respect to the main line portion 28 with the slot 26 interposed therebetween and for setting conversion characteristics. On the second surface side of the substrate 10, a microstrip line 20 is formed by patterning a conductor layer having a thickness of about 10 to 20 μm.

As the feed line, a coaxial cable 30 which is an unbalanced line is used and connected to the second surface side of the substrate 10. In this coaxial cable 30, a core layer 36 is surrounded by a dielectric layer 34, and a jacket (shield) 3
2 is provided with a general configuration.

The jacket 32 of the coaxial cable 30 is
Conductive bonding lands 22 formed on the second surface of
Are connected to the line portion 12 through the sheath bonding land 22 and a feed point 60 which is a through-hole plating layer formed on the substrate 10.
The core wire 36 extending from the dielectric layer 34 is
On the second surface 0, it is connected by soldering to a core bonding land 24 formed near the jacket bonding land 22.

The core wire connecting lands 24 are connected to the microstrip line 20. Note that the core wire joining land 24 may be formed integrally with the microstrip line 20 or may be formed separately from the microstrip line 20 and later formed on the microstrip line 2.
0 may be connected.

Line section 12 and microstrip line 20
Are connected via a feed point 62 which is a through-hole plating layer formed on the substrate 10. Therefore, the core wire 34 of the coaxial cable 30 is connected to the line section 12 at the feeding point 62 via the microstrip line 20.

The microstrip line 20 serves not only as a simple line connecting the coaxial cable 30 and the feeding point 62 in the balun 7, which is a balanced / unbalanced converter, but also with the main line portion 28 of the line portion 12. The interaction also serves as an impedance converter.

Since the microstrip line 20 is formed as a conductor layer pattern, there is an advantage that its characteristic impedance can be changed to a desired value only by adjusting its line width. In theory, the characteristic impedance of the microstrip line 20 is as shown in FIG.
Are set so as to satisfy the impedance conversion characteristics as shown in FIG. In FIG. 6, Zin is the characteristic impedance as viewed from the left side of the line, Zl is the characteristic impedance as viewed from the right side of the line, Zo is the characteristic impedance of the part that becomes the impedance conversion unit, and Zm1 and Zm2 are the parts that become the impedance conversion unit. It shows characteristic impedance in different regions. FIG. 6 (b)
Theoretically, when the line length of the microstrip line 20 is λ / 4 (λ is the transmission / reception wavelength), the width is set so that the characteristic impedance Zo satisfies the following equation (1). It will be.

[0032]

(1) Zin · Zl = Zo ² (1)

In the case corresponding to FIG. 6D, theoretically, for example, when the length of the microstrip line 20 is λ / 4, the characteristic impedance Zm1 or Zm2 becomes ) Or (3), the width is set.

[0034]

[Number 2] ^{Zm1 = (Zin 2 · Zl)} 1/3 ··· (2)

[0035]

Zm2 = (Zl ² · Zin) ^1/3 (3)

In the example of FIG. 5 of the present embodiment, the microstrip line 20 is
4, a substantially L-shaped pattern is formed, and in order to achieve impedance matching between the line portion 12 and the coaxial cable 30, a region having a desired line width in the line and further different in width from each other. 20a, 20b, and 20c. In this example, the length of the region 20b is approximately λ / 4.
It has become. The characteristic impedance of the microstrip line 20 is calculated as HA. It can be approximated according to Wheeler's formula, etc., but is actually affected by various other factors, especially the electrical conditions near the installation location. When the characteristic impedance changes, the regions 20a and 20a of the microstrip line 20 of FIG.
The characteristic impedance can be adjusted by increasing or decreasing the width of each part of b and 20c.

The length of the branch line 29, it is ideal to lambda _2/4 relative to the wavelength lambda ₂ = 18cm of GPS signals. On the other hand, in the middle of the branch line section 29, the feeding point 62
Only lambda _1/4 with respect to the wavelength lambda ₁ = 11cm signal automotive satellite from the spaced position, providing a selection connection 27 connecting the main line portion 28 and the branch line 29. The selection connection unit 27 includes a switching circuit DS27a connected to the main line unit 28, a switching circuit DS27b connected to the branch line unit 29, and a switching circuit DS27b.
a and 27b. These switching circuits DS27a and 27b have substantially the same circuit configuration as the switching circuit DS5 (see FIG. 2) provided in the antenna 1, and each of them selectively applies a DC bias voltage to the input terminal Bias1 or the input terminal Bias2. Thereby, the diode in the configuration is configured to be turned on / off. The switching circuits DS27a and 27b are connected to the switching circuit D27.
Similarly to S5, the input terminal Bi is connected to the bias circuit 71 of the receiver 70, and the input terminal Bi
The configuration is such that a DC bias voltage is selectively applied to as1 and Bias2.

Referring to FIG. 1 again, the receiver 70 includes a receiving circuit 73 for demodulating and amplifying a signal received from the antenna 1 and a push button switch and a dial switch (not shown) in addition to the bias circuit 71 described above. An operation unit 77 for performing operation inputs such as power on / off and switching of a desired station / use frequency band, and a liquid crystal display for displaying vehicle position information / route information based on GPS signals and operation state information of the entire apparatus. Display 79 for
And a control unit 75 that controls the operation of the entire receiver 70. Although not shown, the control unit 75 includes a CPU that executes various arithmetic processes, a ROM that stores operation programs and various set values, a RAM used for various operations, and a non-volatile memory that stores an operation history and the like. It is comprised including.

The operation of the present embodiment configured as described above will be described below. In the present embodiment, it is assumed that the receiver 70 normally receives satellite broadcasts for automobiles and receives GPS signals at predetermined time intervals.

In FIG. 7, first, the control unit 7 of the receiver 70
5 detects the operation state of the receiver 70 from the operation state of the reception circuit 73 and the operation state of the operation unit 77 (S10). Next, it is determined whether a GPS signal reception request has been made based on the detected operation state (S20).

At the time of normal reception, that is, during reception of automobile satellite broadcasting, a negative determination is made because no GPS signal reception request has been made. Next, the off operation of the two switching circuits DS5 of the antenna 1 is performed. Output is performed (S30). The output of the OFF operation is transmitted from the bias circuit 71 to the two switching circuits D of the antenna 1 in accordance with the output of the OFF signal to the bias circuit 71.
A DC bias voltage is applied to the input terminal Bias2 on the cathode side in S5. As a result, the diode 61 of the switching circuit DS5 is turned off, whereby the conduction of the left and right antenna elements 3 in FIG. 2 is cut off. As a result, the effective length LA1 of the antenna 1 in FIG. 1 is selected.

Next, an on operation output is performed on the two switching circuits DS27a and 27b of the balun 7 (S40). Specifically, the on operation output is supplied from the bias circuit 71 to the two switching circuits DS2 of the balun 7 in accordance with the output of the on signal to the bias circuit 71.
Input terminal Bias1 on the anode side in 7a, 27b
, A DC bias voltage is applied. As a result, the diode 61 of the switching circuit DS5 is turned on or turned on, and the effective length LB1 of the branch line section 29 of the balun 7 in FIG. 5 is selected.

Next, if a GPS signal reception request has been made, an affirmative determination is made in step S20, and then an on operation output is performed on the two switching circuits DS5 of the antenna 1 (S50). Specifically, the on operation output is supplied from the bias circuit 71 to the anode-side input terminals Bi of the two switching circuits DS5 of the antenna 1 in accordance with the output of the on signal to the bias circuit 71.
A DC bias voltage is applied to as1. As a result, the diode 61 of the switching circuit DS5 is turned on or turned on, thereby connecting the left and right antenna elements 3 in FIG. 2, and as a result, the effective length LA2 of the antenna 1 in FIG. 1 is selected.

Next, an off operation output is performed on the two switching circuits DS27a and 27b of the balun 7 (S60). Specifically, the off operation output is supplied from the bias circuit 71 to the two switching circuits DS2 of the balun 7 in accordance with the output of the off signal to the bias circuit 71.
7a, 27b, the cathode-side input terminal Bias2
, A DC bias voltage is applied. Thereby, the conduction of the diode 61 of the switching circuit DS5 is cut off,
Effective length LB2 of branch line section 29 of balun 7 in FIG.
Is selected. Therefore, the effective length LA2 of the antenna 1 and the branch line section 29 of the balun 7 suitable for receiving the GPS signal
Is received according to the effective length LB2 of.

As described above, the present embodiment includes the two antenna elements 3 and the switching circuit DS5 interposed between the plurality of antenna elements 3, and the switching circuit DS5 includes the diode 6
1 is configured such that the input terminal Bias1 on the anode side or the input terminal Bias2 on the cathode side and the DC bias power supply are selectively connected by the operation of the bias circuit 71, so that a bias voltage is applied to the cathode side of the diode 61 (that is, Bias) can reliably prevent conduction of the diode 61. Further, since the capacitors 67 and 68 are provided between the antenna element 3 and the connection point between the diode 61 and the DC bias power supply side (input terminals Bias1 and Bias2), the DC bias voltage does not act on the antenna element 3. .

When the effective length of the antenna element 3 is changed according to the frequency band used as in the antenna 1, the impedance characteristic of the antenna changes.
The balance between this and the feed line also changes, but in the present embodiment, in the balun 7 which is a balance-unbalance converter,
Since the effective length of the branch line section 29, which is a conversion characteristic setting member, is changed by turning on / off the switching circuits DS27a and 27b, the conversion of the balun 7 can be performed even when used in connection with such an antenna 1. By adjusting the characteristics, proper balance-unbalance conversion can be performed. In the switching circuits DS27a and 27b of the balun 7, similarly to the switching circuit DS5 of the antenna 1, application of a bias voltage to the cathode side of the diode (that is, reverse bias) can reliably prevent conduction of the diode.

Further, in the present embodiment, the branch line section 29 as the conversion characteristic setting member of the balun 7 and the core wire 36 of the coaxial cable 30 are short-circuited by the microstrip line 20, and the microstrip line 20 connects the antenna 1 to the antenna 1. , The fine adjustment of the impedance can be easily performed by changing the line width of the microstrip line 20.

In the present embodiment, the desired receiving frequency band is detected from the operating state of the receiver 70, and the switching circuit DS5 of the antenna 1 and the switching circuits DS27a, DS2 of the balun 7 are detected in accordance with the detected desired receiving frequency band.
7b is provided with a control unit 75 for outputting an operation instruction, and the effective length of the branch line unit 29 of the balun 7 is changed in accordance with the reception wavelength in the effective length of the antenna element 3; The effective number of the antenna elements 3, that is, the effective length of the antenna 1 is selected, and the balance-unbalance conversion at that time can be appropriately performed.

In this embodiment, the input terminal Bias1 on the anode side or the input terminal Bias2 on the cathode side of the diode 61 and the DC bias power supply are selectively connected by the operation of the bias circuit 71. Instead of a simple configuration, as shown in FIG. 3, by forming a selection bias circuit including a manual switch SW and a polarity reversing inverter 81, the input terminal Bias1 or the input terminal Bias2 is operated according to the operation of the manual switch SW.
And a DC bias power supply may be selectively connected.

In this embodiment, the left and right branches of the antenna 1 are configured by connecting the two antenna elements 3 with the switching circuit DS5.
The base end of each branch of the antenna element 3 is a balun 7
Has been described, the present invention can be applied to antennas having various configurations as shown in FIGS. 8A to 8F in addition to the antenna having such a configuration. . FIG. 8 shows (a)
Is a dipole antenna, (b) is a monopole antenna, (c) is an inverted L antenna (balanced type), (d) is an inverted L antenna, (e) is a T-type antenna (balanced type), and ( f) shows an application example of the present invention in a T-type antenna.

Further, in this embodiment, two antenna elements 3 are used for one branch of the antenna 1,
Although the effective length of the antenna is changed in two stages, a configuration in which three or more antenna elements are used on one side of the antenna 1 and the effective length of the antenna is changed in three or more stages instead of such a configuration. Such a configuration is also included in the category of the present invention.

Further, in the present embodiment, the balun 7 which is a branch conductor type balanced-to-unbalanced converter has been described as an example of the balanced-to-unbalanced converter. It is also possible to apply the present invention to a balanced-unbalanced converter having the above configuration, and any configuration that changes the effective length of the conversion characteristic setting member belongs to the scope of the present invention.

By the way, instead of the switching circuit DS5 in the present embodiment, the switching circuit 1 shown in FIG.
05 may be used. This switching circuit 105
The configuration is such that a diode 107 is interposed between a ground point and a connection point between the cathode side of the diode 61 and the input terminal Bias2. The diode 107 has the same characteristics as the diode 61, or has a relatively low breakdown voltage. Note that this switching circuit 10
The remaining configuration of 5 is the same as that of the above-described switching circuit DS5. Therefore, the same members are denoted by the same reference numerals and description thereof will be omitted.

In this switching circuit 105, even if the DC bias voltage from the input terminal Bias2 (ie, reverse bias) exceeds the breakdown voltage of the diode 61, the operation of the diode 107 reduces the DC bias voltage. There is an advantage that it is possible to escape to the ground point, and thereby it is possible to more reliably prevent undesired conduction of the diode 61.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration example of a switching circuit.

FIG. 3 is a diagram illustrating a configuration example when a bias circuit includes a manual switch;

FIG. 4 is a diagram illustrating another configuration example of the switching circuit.

5A is a plan view showing a balun, and FIG. 5B is a side view thereof.

FIG. 6 is a diagram illustrating impedance conversion characteristics.

FIG. 7 is a flowchart showing the operation of the receiver.

FIGS. 8A to 8F are diagrams showing other configuration examples of the antenna.

[Explanation of symbols]

1 antenna, 3 antenna elements, 5, 27a,
27b Switching circuit DS, 7 baluns, 20 microstrip lines, 28 main line sections, 29 branch line sections, 30 coaxial cables.

Claims (7)

[Claims] 1. An antenna comprising: a plurality of antenna elements; and a switching circuit interposed between the plurality of antenna elements, wherein the switching circuit includes a diode, a DC bias power supply, Switching means for selectively connecting an anode side or a cathode side to the DC bias power supply; and a capacitor provided between a connection point between the DC bias power supply and the diode and the antenna element. Antenna. 2. The antenna according to claim 1, wherein said switching means is a circuit that operates based on an operation of a manual switch. 3. A balanced-unbalanced converter comprising a conversion characteristic setting member for setting a balance-unbalance conversion characteristic according to a reception wavelength of an antenna to be connected, wherein the conversion characteristic setting member has an effective length. A balanced-unbalanced converter having an effective length changing means for changing. 4. The balance-unbalance converter according to claim 3, wherein one end of the conversion characteristic setting member is short-circuited to an end of the first conductor of the feed line on the antenna side, and the other end is provided. Is a conductor short-circuited to the second conductor of the feeder line, has a first effective length according to the reception wavelength in the first effective length of the antenna element, the effective length changing means, From the short-circuit point on the antenna side in the conversion characteristic setting member, a connection point separated by a second effective length according to the reception wavelength in the second effective length of the antenna element, and a second conductor of the feed line ,
A balun converter comprising switch means for selectively connecting. 5. The balun converter according to claim 4, wherein the switch means selectively selects a diode, a DC bias power supply, an anode side or a cathode side of the diode, and the DC bias power supply. And a switching circuit connected to the switching circuit. 6. The balanced-unbalanced converter according to claim 4, wherein the conversion characteristic setting member and the first conductor of the power supply line are short-circuited by a strip line, and the strip line is used for the conversion characteristic setting member. A balun converter, wherein impedance matching with the antenna is performed. 7. A receiver used in connection with the antenna according to claim 1 and the balun converter according to claims 3 to 6, wherein band detection means for detecting a desired reception frequency band; Control means for outputting an operation instruction to the switching means of the antenna and the effective length changing means of the balun converter according to the detected desired reception frequency band, wherein the control means comprises an effective length of the antenna element. Wherein the effective length of the conversion characteristic setting member is changed so as to conform to the reception wavelength of the receiver.