JP2003347822A - Diversity antenna for radio lan - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diversity antenna for a radio LAN having high diversity effect for preventing drop in the reception intensity. <P>SOLUTION: A first antenna 11 of a vertical polarization antenna and a 2nd antenna 12 of a horizontal polarization antenna are installed in parallel on the same dielectric substrate 10. The 1st antenna 11 is monopole antenna, formed substantially L-shaped, as seen from side face, and is positioned upper of a grounded conductor 13 mounted on the rear surface of a dielectric substrate 10. The second antenna is a dipole antenna and is positioned at a part, where the grounded conductor does not exist on the dielectric substrate. The first and the second antennas 11, 12 are connected to a diversity reception circuit 17, a signal wave of stronger receiving the intensity out of respective signal waves received by the 1st antenna 11 and the 2nd antenna 12, is selected, and sent to a receiver 18. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity antenna used for transmitting and receiving signal waves in a wireless LAN (local information communication network), and more particularly, to a diversity antenna mounted on a wireless LAN card mounted on an electronic device such as a personal computer. It relates to a suitable diversity antenna.

[0002]

2. Description of the Related Art In recent years, wireless LANs that can exchange information by transmitting and receiving signal waves in a predetermined frequency band (for example, 2.4 GHz band) without using a wired cable have become widespread. When an electronic device such as a personal computer is compatible with a wireless LAN, a wireless LAN card having a transmission / reception function is often mounted. Such a wireless LAN card is equipped with an antenna for transmitting and receiving a linearly polarized (usually vertically polarized) radio wave used in a wireless LAN, a transmitting circuit, a receiving circuit, and the like.

In an indoor wireless LAN, the effect of multipath, that is, a signal wave is reflected on a floor or a wall and is synthesized through many paths, cannot be ignored. Due to the interference, the reception intensity is likely to be distorted. Therefore, conventionally, for example, a diversity antenna as shown in FIG. 5 is mounted on a wireless LAN card to reduce the distortion of the reception intensity.

In the conventional wireless LAN diversity antenna shown in FIG. 5, a pair of monopole antennas 2 and 3 for transmitting and receiving a vertically polarized signal wave are arranged side by side on a dielectric substrate 1. Ground conductor 4 on almost the entire back surface of
Is provided. Each of the monopole antennas 2 and 3 has the same antenna installed at a different position, and is connected to a transmitter (not shown), a diversity receiving circuit, a receiver, and the like via feed lines 5 and 6. Each of the monopole antennas 2 and 3 is formed in a substantially L-shape in a side view so that a signal wave of a desired wavelength can be transmitted and received while suppressing a height dimension. The signal wave received by each of the monopole antennas 2 and 3 is sent to a diversity receiving circuit, and a signal wave having a high reception strength is selected, or both signal waves are combined and then received by the receiver. Sent to and received.

[0005]

The above-mentioned conventional wireless L
The diversity antenna for AN adopts a system (space diversity system) in which the positions where the monopole antennas 2 and 3 are installed are different, but since these monopole antennas 2 and 3 are both vertically polarized antennas, There is a problem that the trouble peculiar to the vertically polarized signal wave cannot be solved. That is, when a vertically polarized signal wave is received at various measurement points in the wireless LAN, FIG.
As shown by a solid line in FIG. 3, the reception strength is significantly reduced at a specific distance (for example, about 30 meters) from the transmission antenna. In the case of a horizontally polarized signal wave, as shown by a chain line in FIG. 6, although the distance from the transmitting antenna is different, there is also a point where the receiving strength is significantly reduced. Also, when measuring the reflection coefficient when the vertically polarized signal wave is reflected on the floor or the like, as shown by the solid line in FIG. 7, the reflection coefficient decreases extremely near the incident angle of 70 degrees, It can be seen that almost no reflection occurs. On the other hand, when the reflection coefficient of the horizontally polarized signal wave is measured, it can be seen that the signal is reflected at a considerable rate irrespective of the incident angle as shown by the broken line in FIG.

Therefore, in the conventional diversity antenna shown in FIG. 5, although a pair of monopole antennas 2 and 3 are provided side by side, there is a problem that the reception strength is significantly reduced at a specific distance from the transmission antenna. However, it is impossible to solve the problem that the reflection coefficient is extremely reduced near the incident angle of 70 degrees.
The high diversity effect required for antennas cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation of the related art, and an object of the present invention is to provide a diversity antenna for a wireless LAN which has a high diversity effect for preventing a drop in reception intensity.

[0008]

In order to achieve the above object, a diversity antenna for wireless LAN according to the present invention comprises a first antenna for transmitting and receiving a vertically polarized signal wave on the same dielectric substrate and a horizontally polarized first antenna. The second transmitting and receiving wave signal wave
, And the first and second antennas are connected to a diversity receiving circuit.

The diversity antenna for wireless LAN thus configured has a polarization antenna in which a first antenna receives a vertical polarization component of a transmitted signal wave and a second antenna receives a horizontal polarization component. Wave diversity system is adopted. In a wireless LAN, the point at which the reception intensity of the vertical polarization component of the signal wave falls is different from the point at which the reception intensity of the horizontal polarization component falls, and the reflection coefficient of the signal wave according to the incident angle is also vertical polarization. Since the component and the horizontal polarization component are different from each other, by transmitting each signal wave received by the first antenna and the second antenna to the diversity receiving circuit for processing, a diversity effect of preventing a drop in reception intensity is obtained. Greatly increase.

[0010] In the above configuration, one of the first and second antennas is a monopole antenna that is bent at right angles to the ground conductor provided on the back surface of the dielectric substrate. The other is preferably a dipole antenna located in a portion of the dielectric substrate where no ground conductor exists.
Since the first and second antennas can be compactly arranged in a limited space on the dielectric substrate, there is no fear of impairing the thinness required for the wireless LAN card.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an external view of a diversity antenna for wireless LAN according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of the diversity antenna. It is.

In the diversity antennas shown in these figures, a first antenna 11 for transmitting and receiving a vertically polarized signal wave and a second antenna for transmitting and receiving a horizontally polarized signal wave are formed on the same dielectric substrate 10. 12 are provided side by side, and a ground conductor 13 is provided on substantially half of the back surface of the dielectric substrate 10. This diversity antenna is a wireless LAN (not shown)
The dielectric substrate 10 is mounted on a card for transmitting and receiving signal waves, and the dielectric substrate 10 is held in a horizontal posture in a state where the wireless LAN card is mounted on an electronic device such as a personal computer.

The first antenna 11 is a monopole antenna which is formed in a substantially L-shape in side view and has a wide portion 11a at a tip end. The first antenna 11 is provided with a transmitter 16, a diversity receiving circuit 17, a receiver 18 and the like. The first antenna 11 is disposed above the ground conductor 13. One end of the high-frequency source is connected to the first antenna 11, and the other end is connected to the ground conductor 13. The second antenna 12 is a dipole antenna that is arranged in a portion of the dielectric substrate 10 where the ground conductor 13 does not exist and is fed centrally. The second antenna 12 is connected to a diversity receiving circuit 17 and a receiver 18 via a feed line 15. It is connected to the.

At the time of transmission of the diversity antenna thus configured, the first antenna 11 transmits a vertically polarized signal wave in a predetermined frequency band. At the time of reception, the first antenna 11 receives the vertical polarization component of the signal wave transmitted to the diversity antenna, and the second antenna 12 receives the horizontal polarization component. Then, the first signal wave received by the first antenna 11 and the second signal wave received by the second antenna 12 are both sent to the diversity receiving circuit 17, and the reception strength of each signal wave is Is selected, and the selected signal wave is sent to the receiver 18 and received. However, the diversity receiving circuit 17 combines the first signal wave and the second signal wave to form a receiver 18.
May be sent.

The above-mentioned diversity antenna for wireless LAN adopts a polarization diversity system in which a first antenna 11 which is a vertical polarization antenna and a second antenna 12 which is a horizontal polarization antenna are used in combination. Even if the reception intensity of the vertical polarization component and the horizontal polarization component of the received signal wave drops due to the influence of multipath, there is no fear that the reception intensity of the signal wave sent to the receiver 18 via the diversity receiving circuit 17 drops significantly. Absent. That is, wireless L
In the AN, as described above, the point where the reception intensity of the vertical polarization component of the signal wave falls is different from the point where the reception intensity of the horizontal polarization component falls (see FIG. 6), and the signal wave corresponding to the incident angle is different. The reflection coefficient differs between the vertically polarized component and the horizontally polarized component (see FIG. 7). Also, as shown in FIG. 3, the reflection phase of the signal wave according to the incident angle is greatly different between the vertical polarization component and the horizontal polarization component. In the case of the vertical polarization, the incident angle is shown as a solid line in FIG. Regardless of the reflection phase is around 180 degrees, whereas in the case of horizontal polarization, as shown by the broken line in FIG.
The phase does not change until the incident angle is around 60 degrees, and the incident angle is 60 degrees.
Beyond this, the reflection phase sharply increases.

Therefore, in the diversity antenna adopting the polarization diversity system in which the vertical polarization antenna and the horizontal polarization antenna are used in combination as in the present embodiment, there are problems peculiar to the vertical polarization component of the signal wave and the horizontal polarization. A defect peculiar to the wave component is not directly reflected on the reception intensity. FIG. 4 is a characteristic diagram showing how the reception strength of the signal wave received by the receiver 18 changes according to the distance from the transmission antenna. As shown in the figure, in this diversity antenna,
It can be seen that the reception can be performed in a good state with little distortion of the reception intensity at any reception point, and the diversity effect is greatly enhanced.

In the case of this diversity antenna, the first antenna 11 is a monopole antenna which stands on the dielectric substrate 10 and bends at a right angle, and the second antenna 11
Of the first antenna 1 on the dielectric substrate 10
Since the dipole antennas are arranged side by side, the first and second antennas 11 and 12 can be compactly arranged in a limited space on the dielectric substrate 10. Therefore, it is possible to transmit and receive a signal wave of a desired wavelength while suppressing the height dimension of the entire antenna, and there is no fear of impairing the thinness required for the wireless LAN card.

[0018]

The present invention is embodied in the form described above and has the following effects.

A first antenna, which is a vertically polarized antenna, and a second antenna, which is a horizontally polarized antenna, are arranged side by side on the same dielectric substrate, and the vertically polarized wave component of the signal wave transmitted is transmitted to the second antenna. One antenna receives the horizontal polarized wave component, and the second antenna receives the signal wave received by the first antenna and the second antenna. The signal wave is sent to the diversity receiving circuit for processing. Since it is a diversity antenna for wireless LAN, the diversity effect for preventing a drop in reception strength is high, and a problem specific to the vertical polarization component and a problem specific to the horizontal polarization component of the signal wave are not directly reflected in the reception intensity. . Therefore, by mounting this diversity antenna on a wireless LAN card, it is possible to receive signals at any reception point in a good state with little distortion in reception intensity.

[Brief description of the drawings]

FIG. 1 is an external view of a diversity antenna for wireless LAN according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of the diversity antenna shown in FIG.

FIG. 3 is a characteristic diagram showing a reflection phase of a signal wave corresponding to an incident angle for each polarization component.

FIG. 4 is a characteristic diagram illustrating a relationship between a reception point and a reception intensity in the embodiment.

FIG. 5 is an external view of a wireless LAN diversity antenna according to a conventional example.

FIG. 6 is a characteristic diagram showing a relationship between a reception point and a reception intensity for each polarization component.

FIG. 7 is a characteristic diagram illustrating a reflection coefficient of a signal wave according to an incident angle for each polarization component.

[Explanation of symbols]

10 Dielectric substrate 11 First antenna 12 Second antenna 13 Ground conductor 16 transmitter 17 Diversity receiver circuit 18 Receiver

Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) H04B 7/10 H04B 7/10 B 7/26 7/26 DF Term (Reference) 5J021 AA02 AA09 AA13 AB02 AB03 CA01 DB05 EA04 FA21 FA31 GA03 HA06 HA10 JA05 5J046 AA04 AB06 AB07 AB10 PA07 5K059 CC03 CC05 DD02 DD27 DD37 5K067 AA23 BB21 CC24 KK03 KK17

Claims (2)

[Claims] A first antenna for transmitting and receiving a vertically polarized signal wave and a second antenna for transmitting and receiving a horizontally polarized signal wave are provided side by side on the same dielectric substrate. A diversity antenna for a wireless LAN, wherein the second antenna is connected to a diversity receiving circuit. 2. The monopole antenna according to claim 1, wherein one of the first and second antennas is a monopole antenna that stands at a right angle to a ground conductor provided on a back surface of the dielectric substrate. And a dipole antenna located at a portion of the dielectric substrate where no ground conductor is present.