JPH118512A - Low profile antenna - Google Patents

Abstract

(57) Abstract: The present invention provides a small and low-profile antenna capable of expanding an operation band. A first linear element (103) and a second linear element (104) whose ends are vertically connected to a ground conductor plate (100), and a third line having ends connected to the two linear elements, respectively. And a fourth linear element 101 having an end connected to the linear element 102. The linear element 103 is connected to the feed line 106 at a connection point 103a, and
04 is connected to the power supply line 105 at a connection point 104a. Each feed line is a high-frequency switch 1 that connects the wireless circuit and the feed line.
07, and the high frequency switch 107 switches the operating frequency band according to the frequency to be received.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small-sized low-profile antenna used for a portable radio having a relatively wide operating frequency.

[0002]

2. Description of the Related Art In recent years, portable wireless devices have been reduced in size and thickness. As the name implies, a portable wireless device is carried around and must be highly portable. For that purpose, it is very important to be small and thin.

[0003] Among components constituting a portable wireless device, miniaturization of a wireless circuit is progressing at a rapid speed. On the other hand, although the miniaturization of the battery and the antenna is progressing, the speed of miniaturizing the circuit unit is not far. Against such a background, miniaturization and thinning of an antenna is one of the technical issues of a portable wireless device that must be swiftly advanced.

On the other hand, in the case of portable radios, the number of subscribers has increased,
Due to an increase in data transmission speed and the like, the frequency band in which the wireless device must operate tends to increase. Generally, as the size of an antenna is reduced, the operating band becomes narrower. Therefore, widening the band of the radio and miniaturizing the antenna are contradictory events.

For example, as a small antenna, there is an inverted-F antenna shown in FIG. This antenna is applied to a mobile phone or the like as a small, low-profile antenna. FIG.
In the figure, 600 is a ground conductor plate, 601 is a linear element, 602 is a short-circuit side linear element, 603 is a feed side linear element, and 604 is a feed point. This antenna operates around a frequency at which the electrical length from the feeding point 604 to the tip 601a of the linear element 601 is a quarter wavelength. Further, by changing the structural parameters of the short-circuit line (not shown) connected to the short-circuit side linear element 602 and the power supply line (not shown) connected to the power supply-side linear element 603, the antenna characteristics can be optimized with respect to the operating frequency band even in the low posture state. Can be

[0006] However, it is known that the operation band of such an inverted-F antenna becomes narrower when the posture is lowered. For example, if the height is about one-tenth of a wavelength of a desired frequency, the bandwidth of the antenna becomes 1% or less. In such a case, the center frequency is 1G and the maximum is 1
There is a problem that it can cope only up to 0 MHz and cannot be applied to a system that requires a wider band.

[0007]

As described above,
In a portable wireless device, an inverted-F antenna has been used as a small and low-profile antenna, but there has been a problem that the operating band is narrowed due to the low posture.

[0008]

In view of the above problems, a low-profile antenna according to the present invention has a ground conductor plate made of a plate-like conductive member and a first linear element having one end connected to the ground conductor plate. A second linear element having one end connected to the ground conductor plate, a third linear element having one end connected to the first linear element, and the other end connected to the second linear element. , One end is connected to a first connection point between the first linear element and the conductor member, and a first feeder line having a length of 1/4 of the wavelength of the first operating frequency; A second connecting point between the linear element and the ground conductor plate, and having a length of 1/4 of the wavelength of the second operating frequency.
And one end is connected to the third linear element, and the length from the other end to the first connection point is one of the wavelengths of the second operating frequency.
/ 4 and the length from the other end to the second connection point is １ ／ of the wavelength of the first operating frequency.
And a switching unit connected to the other end of each of the first and second power supply lines and selectively switching between the first and second power supply lines. .

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration example of a low-profile antenna according to an embodiment of the present invention. In FIG. 1, 100 is a ground conductor plate, 1
01, 102, 103, and 104 are linear elements;
06 is a power supply line, 107 is a high-frequency switch, 108 is a control circuit, and 109 is a wireless circuit. Linear elements 103 and 1
Reference numerals 04 are disposed such that one end is perpendicular to the ground conductor plate 100. The linear element 102 has one end connected to the linear element 103 and the other end connected to the linear element 104, and is disposed so as to be parallel to the ground conductor plate 100. Further, one end of the linear element 101 is connected to a position different from the center position of the linear element 102, and is disposed so as to be parallel to the ground conductor plate 100.

The linear element 103 is connected to a power supply line 105 formed of a coaxial cable or the like at a connection point 103a. Similarly, the linear element 104 is connected to a feed line 106 formed of a coaxial cable or the like at a connection point 104a.

The high frequency switch 107 is connected to the power supply lines 105 and 106 and the radio circuit 109. The high-frequency switch 107 selects either the power supply line 105 or the power supply line 106 according to a signal from the control circuit 108. The unselected feeder line is configured to be open at the end.

The power supply line 105 is not selected and the power supply line 105 is not selected.
When the terminal on the high-frequency switch 107 side is opened, the terminal connected to the linear element 104 is short-circuited. Similarly, if the power supply line 106 is not selected and the terminal on the high frequency switch 107 side of the power supply line 106 is opened, the terminal connected to the linear element 103 is in a short-circuit state.

The linear element (103 or 104) on the side selected by the high-frequency switch 107 is the element on the feeding side in the inverted-F antenna, and the linear element (103 or 104) on the open side is It operates as an element on the short-circuit side.

With such a configuration, the high frequency switch 107 controls the inverse F of two different configuration parameters.
This is equivalent to operating with the antenna switched. Generally, the operating frequency of the inverted F antenna is determined by the distance from the feeding point to the open end. Therefore, antennas having different lengths of this portion have different operating frequencies. In the present invention, the same operation as that of two types of antennas having different lengths is realized by one antenna.

The operation of the antenna according to one embodiment of the present invention will be described with reference to FIG. 2 (a), (b),
(C) shows a simple configuration of the antenna of the present embodiment. In FIG. 2, a power supply mark is attached to a connection point (103a or 104a) which is a power supply point between the linear element on the side selected by the high frequency switch 107 (not shown) and the power supply line among the linear elements 103 or 104. I have. The connection point (103a or 104a) between the linear element on the open side and the feeder line
) Are marked with a mark indicating grounding. In FIG. 2, A represents the length of the linear element 101, the length from the feeding point 103a to the connection point between the linear element 101 and the linear element 102, and C represents the length of the linear element 101 from the feeding point 104a. The length to the connection point of the element 102 is shown.

As described in the configuration of this embodiment, the linear element 1
Numeral 01 is disposed at a position shifted from the center position of the linear element 102. Therefore, B shown in FIGS. 2A, 2B, and 2C
And C have different lengths.

First, when the power supply line 105 is selected by a high-frequency switch 107 (not shown), the side of the linear element 103 becomes the power supply side and the side of the linear element 104 becomes the short-circuit side as shown in FIG. In this case, the antenna is f1 = c / λ
= 4c / (A + B) in a band centered on the first frequency f1. On the other hand, when the power supply line 106 is selected, the side of the linear element 104 shown in FIG. 2C is the power supply side, and the side of the linear element 103 is the short-circuit side. in this case,
The antenna operates in a band centered on the second frequency f2 indicated by f2 = c / .lambda. '= 4c / (A + B).
Since the lengths of B and C are different, f1 and f2 are different frequencies.

As described above, by switching the element to be fed, the antenna of the present embodiment can have two different band characteristics. Next, a method for determining antenna parameters will be described in detail with reference to FIGS.

For example, suppose a case where an operating band of 100 MHz is required around a frequency of 1.9 GHz. When the antenna height is 7 mm, the operating band is about 50 MHz with a normal inverted-F antenna. In this state, V
FIG. 3 shows the frequency characteristics of the SWR.
Here, VSWR is one of the indexes indicating the operation band of the antenna, and is a value indicating how much the power input to the antenna is actually radiated. The larger the VSWR, the more power is returned to the wireless circuit without being radiated from the antenna.

FIG. 4 is an explanatory diagram for explaining the operating band characteristic of the embodiment of the present invention. Here, the same components as those in FIG. FIG. 4 illustrates a case where the height L1 of the antenna is 7 mm. Linear element 1
03, the length from the connection point of the linear element 102 to the connection point of the linear element 102 and the linear element 101 is L2, and the linear element 10
Let L3 be the length from the connection point between the linear element 102 and the linear element 102 to the connection point between the linear element 102 and the linear element 101. The length (L2 + L3) of the linear element 102 is a parameter for determining the best value of VSWR. This value corresponds to the linear element 10
1 is attached to one of the ends of the linear element 102,
In this state, the VSWR value is determined experimentally so as to be optimal. Here, the length of the linear element 102 (L2 + L
3) was set to 5 mm.

Next, parameters L2 and L3 relating to the mounting position of the linear element 101 are determined by calculation from the optimized operating band of the antenna when determining the length of the linear element 102. Here, the band BW of the antenna was initially 50 MHz. Desired band BW0 is 1
Assuming that the frequency is 00 MHz, two center frequencies are determined as f1 = f0 + BW0 / 4 f2 = f0-BW0 / 4 assuming that the current center frequency is f0, and the operating band is allocated. From these two equations, the current center frequency f0 = 1900
It can be seen that it is sufficient to distribute the frequency by 25 MHz upward and downward from the MHz.

Assuming that the connection point 103a is a feeding point, the length from the connection point 103a to the tip of the linear element 101 (L1 +
L2 + L4) is a quarter wavelength (λ /
4), and the linear element 10 is connected from the connection point 104a.
The length (L1 + L3 + L4) to the tip of 1 is 1875
It is sufficient if the wavelength becomes a quarter wavelength (λ ′ / 4) in MHz. When λ / 4 and λ '/ 4 are calculated, λ / 4 is 39 mm and λ' / 4 is 40 mm.
Becomes This is L2−L3 = λ / 4−λ ′ / 4 from the two equations of L1 + L3 + L4 = λ / 4 and L1 + L2 + L4 = λ ′ / 4. Here, since L2 + L3 = 5 mm and L2-L3 = −1 mm, L2 is 2 mm and L3 is 3 mm on the linear element 102.
It turns out that it is good to do. Finally, the length L4 of the linear element 101 can be obtained from L1 + L3 + L4 = λ / 4. Here, the length L4 of the linear element 101 is 31 mm.

Here, the length of the feed line 105 is L1 + L2 +
40 mm corresponding to L4, the length of the power supply line 106 is L1 + L
It becomes 41 mm corresponding to 3 + L4. V of this embodiment
FIG. 5 shows the SWR frequency characteristics. When the linear element 103 is selected, the length from the feeding point to the tip of the linear element 101 is 40 mm, and the center frequency is 1923 MHz. When the linear element 104 is selected, 41 mm
Therefore, the center frequency is 1875 MHz. Since the operating band can be set to 50 MHz at each center frequency, from 1850 MHz to 1950 MHz, almost 10
This will cover the 0 MHz band.

Next, the control circuit 108 will be described.
The control circuit 108 estimates the frequency of the signal currently being received from the frequency control data of the wireless circuit 109 and adjusts the power supply line accordingly in order to match the operation band of the antenna with the currently used frequency band. To the high-frequency switch 107 to perform the following. As the frequency control data, for example, a control signal of a voltage control frequency transmitter of a synthesizer section may be used.

In general, in radio communication, a frequency is specifically set for a control signal from a base station. Therefore, a method is conceivable in which the high-frequency switch 107 is first set to a certain frequency band of the control signal, and if the frequency is reset according to the control signal, the frequency band is reset so as to move accordingly. With the configuration described in the above embodiment, the operable band of a small, low-profile antenna such as an inverted-F antenna can be significantly widened.

[0027]

As described above in detail, according to the present invention, by switching the operating frequency band, it is possible to realize a small, low-profile antenna having a wide frequency band.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a low-profile antenna according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating the operation of the low-profile antenna according to one embodiment of the present invention.

FIG. 3 is a diagram illustrating the operation of a conventional antenna.

FIG. 4 is an explanatory diagram of a low-profile antenna according to one embodiment of the present invention.

FIG. 5 is an operation explanatory diagram of the low-profile antenna according to one embodiment of the present invention;

FIG. 6 is a configuration diagram of a conventional small low-profile antenna.

[Explanation of symbols]

 100. . . Ground conductor plate 101. . . Linear element 102. . . Linear element 103. . . Linear element 104. . . Linear elements 103a. . . Connection points 104a. . . Connection point 105. . . Feed line 106. . . Power supply line 107. . . High frequency switch 108. . . Control circuit 109. . . Wireless circuit

Claims (2)

[Claims] A first linear element having one end connected to the ground conductor plate; and a second linear element having one end connected to the ground conductor plate. A third linear element having one end connected to the first linear element and the other end connected to the second linear element; and one end connected to the first linear element and the conductor member. And the length is １ ／ of the wavelength of the first operating frequency.
A first power supply line, one end of which is connected to a second connection point between the second linear element and the conductor member, the length of which is １ ／ of the wavelength of the second operating frequency.
And one end connected to the third linear element, and the other end connected to the first
Is 1 wavelength of the second operating frequency.
/ 4, and a fourth linear element disposed so that the length from the other end to the second connection point is ４ of the wavelength of the first operating frequency; and A low-profile antenna, comprising: a switching unit connected to a power supply line and the other end of the second power supply line, and selectively switching between the first power supply line and the second power supply line. . 2. A ground conductor plate made of a plate-like conductive member, a first linear element having one end connected perpendicularly to the ground conductor plate, and a second linear element having one end vertically connected to the ground conductor plate. A third linear element having one end connected to the first linear element and the other end connected to the second linear element and parallel to the ground conductor plate; The first linear element is connected to a first connection point between the first linear element and the conductor member, and has a length of １ ／ of the wavelength of the first operating frequency.
A first power supply line, one end of which is connected to a second connection point between the second linear element and the conductor member, the length of which is １ ／ of the wavelength of the second operating frequency.
A second power supply line, one end of which is vertically connected to the third linear element, and the length from the other end to the first connection point is １ ／ of the wavelength of the second operating frequency. And the length from the other end to the second connection point is １ ／ of the wavelength of the first operating frequency,
A fourth linear element that is parallel to the ground conductor plate, and is connected to the other end of the first power supply line and the other end of the second power supply line, respectively, and selectively connects the first power supply line with the second power supply line. A low-profile antenna, comprising: switching means for switching between a power supply line and a power supply line.