JPH11112226A - Polarization switching antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To match one matching circuit at the time of switching a short-circuit point by providing reactance by which input impedance that is almost equal to antenna impedance when one short-circuit point is short-circuited is obtained instead of the short-circuit conductor of the other short-circuit points except for one short-circuit point. SOLUTION: Loading reactance 5 is inserted and connected into the conductor 4 of the short-circuit points A-A' in series. Loading reactance 5 is inserted at the time of short-circuiting A-A'. In a circuit containing an on/off switch means, inductance (matching coil) L0 provided as loading reactance 5, DC inhibition capacitors C1 and C2 and a switching diode D1 are provided, and the values of the control high resistors R1 and R2 of switching control voltage (VCONT) are decided by the ability of the switching diode D1 , power consumption and the value of VCONT. Thus, input impedance when the points A-A' are short- circuited becomes almost equal to input impedance at the time of short-circuiting the points C-C'.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna used for a thin pager such as a card type pager, and more particularly, to a reception bias by switching a short-circuit element of a flat loop antenna which also serves as a receiver case. The present invention relates to an antenna for switching a wavefront.

[0002]

2. Description of the Related Art Small mobile radios are used in various postures. In particular, in the case of a card-type radio paging receiver using a conductor plate of a flat loop antenna as a receiver case,
The reception gain greatly varies depending on the attitude at the time of reception.

A flat loop antenna which also serves as the case of such a card-type radio pager has a feed point near one corner of the flat conductor plate and a short-circuit near the other corner to cut the cross section. This is a loop antenna formed to have a U-shape. This short-circuit point is provided at a plurality of locations so that it can be turned on / off (short-circuit / open), and the short-circuit location at which the receiving sensitivity is maximized is switched and selected, so that the polarization plane of the radio wave arriving at the antenna polarization plane is changed They can be matched (polarization matching or polarization diversity reception).

FIG. 4 is a perspective view showing the structure of a conventional polarization switching antenna. In the drawing, reference numerals 1 and 2 denote flat conductor plates, which function as antenna elements. Reference numeral 3 denotes an insulating frame which accommodates a receiver circuit inside the frame, and is fixed by being sandwiched between the conductor plates 1 and 2 from the upper and lower surfaces. 4
Denotes a short-circuit conductor, which is a conductor such as a bar, a thin plate, or a screw that conducts (short-circuits) near the corners of the upper conductor plate 1 and the lower conductor plate 2. Further, there is a switching means for turning on / off the short-circuit conductor 4 using a switching diode, but is not shown.

In this antenna, a planar loop antenna is formed by combining two planar conductors.
The two corners DD ′ are the feeding points, and the corners CC ′ and A−
A 'is switched to any one of them as a short-circuit point, and a short-circuit point is selected so as to increase the reception gain, thereby forming a polarization switching diversity antenna.

FIG. 5 is a directional characteristic diagram of the antenna.
As shown in FIG. 6, the direction of arrival of the radio wave is the X axis, and the vertical polarization component when the X axis is rotated around the X axis is shown. FIG. 5A shows a case where the point CC ′ is short-circuited.
It becomes an almost vertically polarized antenna. Also, FIG.
This is the case where the point A 'is short-circuited, and the antenna becomes a substantially horizontally polarized antenna.

[0007]

However, in the above-mentioned conventional structure, the conductor plates 1 and 2 are generally rectangular (L × W), and when the corners CC ′ are short-circuited, When the corners AA 'are short-circuited, the loop lengths from the feeding point to the short-circuit point are different, and thus the antennas have the property that the input impedances of the antennas are different from each other. For this reason, the matching circuit (not shown) between the receiving circuit and the antenna is switched at the same time as the switching of the short-circuit point, so that matching is achieved by switching, so that the number of components and the mounting area of the matching circuit increase. There is.

In order to compensate for this drawback, for example, as shown in FIG. 7, if the shape of the conductor plates 1 and 2 is square (L × L), even if the corner AA ′ is short-circuited, CC 'Even if the point is short-circuited, the input impedance becomes the same, and one matching circuit can be shared without switching the variable matching circuit. However, in this configuration, the shape of the flat loop antenna is limited to a square, and there is a practically serious disadvantage that it cannot be applied to a rectangular shape.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks and problems, and to provide a rectangular plate-like loop antenna, which can be matched by a single matching circuit even when a short-circuit point is switched. Is to provide.

[0010]

According to the present invention, in order to improve the above-mentioned disadvantage, when the corner AA 'point is short-circuited (CC' open), an inductance is formed in series between AA '. The input impedance at that time is made substantially equal to the input impedance at the time when the corner C-C 'is short-circuited (opened at A-A'). Even if the short-circuit point is switched, the matching circuit needs to be switched. Instead, the gist is that a single matching circuit is configured to obtain good reception characteristics.

That is, the polarization switching antenna according to the present invention is a case in which two rectangular flat conductor plates arranged in parallel at a sufficiently small interval compared with the wavelength are fixed by an insulating frame to accommodate a receiver circuit. And a short-circuit conductor for short-circuiting the corners at high frequency with one of the opposite corners of the two conductor plates serving as a power supply point and the other plurality of corners serving as short-circuit points. And a switch for short-circuiting one of the plurality of corners so as to match the plane of polarization of the antenna with the plane of polarization of the arriving radio wave. In place of the short-circuit conductors at the other short-circuit points except for one, a reactance is provided so that the input impedance becomes substantially equal to the antenna input impedance when the one short-circuit point is short-circuited. And it is characterized in that said and.

Further, when the one short-circuit point is set at a corner in the long side direction on the same side as the feed point of the rectangular conductor plate, the short-circuit point is short on the same side as the feed point of the rectangular conductor plate. A matching coil is used as the reactance provided in place of the short-circuit conductor at the corner in the side direction, or the one short-circuit point is located on the same side as the feeding point of the rectangular conductor plate. When the corner is set in the short side direction, a matching capacitor is provided as the reactance provided on the same side as the feeding point of the rectangular conductor plate in place of the short-circuit conductor in the long side direction corner. It is assumed that.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 shows a perspective view and a partial circuit diagram of a first embodiment of the present invention. (A) is an external structural view of the first embodiment,
It is the same rectangle as the conventional structure shown in FIG. 4, and the same portions are denoted by the same reference numerals. The difference from the conventional one is that the loaded reactance 5 is inserted and connected in series with the conductor 4 at the short-circuit point AA 'so that the loaded reactance 5 is inserted when the AA' is short-circuited. FIG. 3B is a detailed circuit example diagram between the short-circuit points AA ′, which is a circuit including on / off switching means. L ₀ is the inductance provided as loaded reactance 5 (matching coil), C _1, C ₂ are DC blocking capacitor, D ₁ is a switching diode. R ₁ and R ₂ are high resistances for controlling the switching control voltage (V _CONT ), the value of which is the switching diode D
₁ is determined by the performance, current consumption, and V _CONT value.

In the first embodiment, for example, when there is no loaded reactance 5 (matching coil L ₀ ) (conventional configuration), specific examples of the input impedance (Zin) of the antenna are as follows: (A-A 'open): Zin = 1.07 + j
93.4 [Ω] AA 'point short circuit (CC' open): Zin = 0.83 + j
74.3 [Ω]. In this state, when the short-circuit point is switched, the input impedances are different from each other. Therefore, when a matching coil of L ₀ = 4 nH is loaded in series at the short-circuit point of AA ′ as in the first embodiment, the input impedance when the AA ′ point is short-circuited is as follows. Become. AA 'point short circuit (CC' open): Zin = 1.02 + j
93.2 [Ω] Therefore, the input impedance becomes almost equal to that at the time of the CC ′ point short-circuit, and it can be seen that even if these short-circuit points are switched, a good matching state can be obtained with the same matching circuit.

In the first embodiment, for example, assuming that the inductance L _{0 of the} matching coil is 4 nH, the values C ₁ and C _{2 of} the DC blocking capacitors are 1000 pF, and the resistance values R ₁ and R ₂ for control are 10 kΩ, + V _CONT the application of a control voltage diode D ₁ is turned on, the matching coil L ₀ to the corner portion a-a 'between (vertical flat conductor plates) are inserted and connected, the diode D ₁ is applied with -V _CONT is turned off And the space between the corners AA ′ is open. The other short-circuit point C-
The circuit between C ′ is a circuit provided with a conducting wire (short-circuit conductor) instead of L _{0 in} FIG. 1B, and is turned on / off (short-circuit / open).

The switching directional characteristic in this case is the same as that of the conventional FIG.
As in the case of (1), good characteristics were exhibited, and it was verified that there was a polarization plane switching effect.

FIG. 2 shows a perspective view and a partial circuit diagram of a second embodiment of the present invention. A rectangular structure similar to that of the first embodiment is different from that of the first embodiment in that a loading reactance 5 is inserted and connected in series to a conductor 4 at a short-circuit point CC ′,
The configuration is such that the loading reactance 5 is inserted when C 'is short-circuited. However, in this case, the matching capacitor C ₀ as loading reactance 5 as shown in (B)
Is provided. As in the case of the first embodiment, the input impedance when there is no matching capacitor C ₀ is as follows: CC ′ point short circuit (AA ′ open): Zin = 1.07 + j
93.4 [Ω] AA 'point short circuit (CC' open): Zin = 0.83 + j
74.3 [Ω]. In this state, when the short-circuit point is switched, the input impedances are different from each other.

Therefore, in the second embodiment, the corner C-
'When the short-circuit point of loading a matching capacitor C ₀ = 60 pF in series, C-C' C input impedance is as follows when shorted points. CC 'point short circuit (AA' open): Zin = 0.86 + j
71.6 [Ω] Therefore, the input impedance when the AA ′ point is short-circuited becomes substantially equal, and it can be seen that even if these short-circuit points are switched, a good matching state can be obtained with the same matching circuit.

In the second embodiment, for example, the matching capacitor C ₀ = 60 pF and the DC blocking capacitor C ₁
= 1000 pF, control resistance values R ₁ , R ₂ = 10 kΩ, and when a control voltage of + V _CONT is applied, the diode D ₁
There turned on, the corners C-C 'matching capacitor C ₀ between is inserted and connected, by applying a -V _CONT diode D ₁ is turned off corners C-C' between becomes open. The circuit between the other short-circuit points AA ′ is configured so that C ₀ = 1000 pF in FIG. 2B and is turned on / off at a high frequency. The switching directional characteristics in this case show good characteristics as in the case of the conventional FIG. 5, and it has been verified that there is a polarization plane switching effect.

[0020] Next, in the first embodiment, a matching coil L ₀ provided as loading reactance 5 between the corner portion A-A of short-circuit point ', in the second embodiment, the short-circuit point corner C -C '
It explained reason for providing the matching capacitor C ₀ as loading reactance 5 between.

FIG. 3 is a perspective view of a rectangular planar loop antenna and an input impedance characteristic diagram thereof. FIG.
As shown in (A), when the corners CC ′ are short-circuited with the corners DD ′ as feed points, a loop length (a U-shaped cross-section loop length) is (2L + t), The loop length when the corner AA ′ is short-circuited is (2W + t). And
The input impedance Zin (A
−A ′ short circuit) is 0.83 + j7 as shown in FIG.
4.3 (Ω), and the input impedance Zin (CC ′ short circuit) when CC ′ is short-circuited becomes 1.07 + j93.4 (Ω) as shown in FIG.

From the above, when CC ′ is short-circuited, A−
Since the loop length is longer than that at the time of A 'short circuit, it can be seen that the L property is large (inductive). In order to make the two impedances the same, the electrical lengths of the two must be equal. Therefore: To match the impedance at the time of AA 'short circuit with the impedance at the time of CC' short circuit, a coil is loaded on AA 'and the electrical length is increased. This is the first
This is an embodiment of the invention. : Conversely, the impedance at the time of AA 'short circuit is CC'
To match the impedance at the time of short circuit, the inductiveness must be reduced. Therefore, a capacitor is loaded on CC ′ to shorten the electrical length at the time of CC ′ short circuit. This is the second embodiment.

[0023]

As described in detail above, according to the present invention, even when the two conductor plates are rectangular, one matching circuit can be shared between the antenna and the radio circuit. ,
The polarization plane directivity characteristic has an extremely large effect in practice that a good characteristic can be obtained as before.

[Brief description of the drawings]

FIG. 1 is a perspective view and a partial circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a perspective view and a partial circuit diagram showing a second embodiment of the present invention.

FIG. 3 is an example of an input impedance characteristic due to a short-circuit loop.

FIG. 4 is a perspective view of a conventional polarization switching antenna.

FIG. 5 is a diagram illustrating an example of a conventional polarization plane switching directional characteristic.

FIG. 6 is a diagram illustrating the definition of polarization plane directivity characteristics.

FIG. 7 is a perspective view of a conventional polarization switching antenna.

[Explanation of symbols]

 1, 2 conductor plate 3 insulating frame 4 conductor 5 loading reactance

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04Q 7/14 H04B 7/26 103C

Claims (3)

[Claims] 1. A rectangular flat plate-shaped conductor plate arranged in parallel at a sufficiently small interval as compared with a wavelength is fixed by an insulating frame and also serves as a case for accommodating a receiver circuit. A short-circuit conductor for short-circuiting the corners at high frequency using one of the opposite corners of the plate as a feeding point and a plurality of other corners as short-circuit points, and an on / off switching means for the short-circuit conductor. In a polarization switching antenna configured to match the polarization plane of an incoming radio wave by switching any one of the corners and short-circuiting, a short-circuit of another short-circuit point other than one of the plurality of short-circuit points A polarized wave switching antenna, wherein a reactance is provided in place of a conductor so that an input impedance becomes substantially equal to an antenna input impedance when the one short-circuit point is short-circuited. 2. When the one short-circuit point is set at a corner in the long side direction on the same side of the rectangular conductor plate as the power supply point, the short-circuit point is short on the same side as the power supply point of the rectangular conductor plate. The polarization switching antenna according to claim 1, wherein a matching coil is used as the reactance provided in place of the short-circuit conductor at the corner in the side direction. 3. When the one short-circuit point is set at a corner in the short side direction on the same side as the feed point of the rectangular conductor plate, the short-circuit point is longer on the same side as the feed point of the rectangular conductor plate. 2. The polarization switching antenna according to claim 1, wherein a matching capacitor is provided as the reactance provided in place of the short-circuit conductor at the corner in the side direction.