JPH05308216A - Diversity antenna - Google Patents

Abstract

PURPOSE: To provide a portable and compact diversity antenna. CONSTITUTION: The diversity antenna has a single antenna element 1 consisting of a 1/4 wavelength monopole and connection switches S1 to S3 for alternately feeding a current from a common RF feeding point 3 to both the ends of the monopole. The feeding point 3 is a transmission signal source or a receiving input circuit and the spatial distance of a current peak when the current is fed from both the ends is about 1/4 wavelength. Thereby the single antenna element 1 acts as a diversity antenna.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity antenna, and more particularly to a diversity antenna for use in which space saving is required such as a portable device.

[0002]

2. Description of the Related Art In diversity reception, two or more spatially separated antennas are used to overcome propagation path variations due to multipath and ionospheric variations. Switching means is used to switch the antennas at high speed, and the signal on the receiving side is a time division signal from each antenna. Fading is largely compensated by the use of diversity if each antenna is properly placed.

When space is an issue, such as in portable devices, diversity technology could not be used because the size of the antenna system is significantly larger than a single antenna.

According to the present invention, a diversity effect is obtained by alternately feeding a single antenna element from both of the separated ends so that the current peaks are spatially separated. That is, it operates like two antennas separated by the distance of the current peak. In one embodiment, the antenna element is alternately fed from both ends by switching the feeding point with a switch. Switching is performed continuously at high speed or by an intelligent method only when necessary according to the signal state. The antenna can be used for both reception and transmission.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, an antenna element is on a ground plane 2 and is fed from switches S1 and S2 at both ends.
With quarter wave strip 1. The switches S1 and S2 are connected to another change-over switch S3, and the three switches operate simultaneously in an interlocking manner. 3 is a signal source, that is, a reception input. Means (not shown) are provided to drive the switches S1, S2, S3 and provide diversity switching at the two ends of the antenna element.

In this example, the spatial separation of the current peaks when driven from both ends is approximately 1/4 wavelength. Therefore,
It operates as a diversity antenna having two antennas separated by a quarter wavelength. The above two antennas do not operate at the same time but operate alternately by switching with a switch as shown.

2 and 3 show an example of the present invention used for transmitting and receiving a frequency of about 1 GHz. FIG. 2 shows the basic copper pattern of the quarter-wave strip 1 and the ground plane 2 provided on the insulating substrate of the printed wiring board 4. The strip 1 and the ground plane 2 are on opposite sides of the substrate and are therefore insulated from each other. The strip 1 is on the front side of the substrate and the ground plane 2 is on the back side of the substrate. Strip 1 operates as a quarter wave monopole.

The strip 1 is fed from the common RF feeding point 7 from both ends by ¼ wavelength transmission lines 5 and 6 having the same structure. The RF feeder 8 is connected to the feeding point 7 via the input line 9.
To the coupling capacitor 10 via the coupling capacitor 10. Transmission line 5,6
Is a copper foil, which is provided on the substrate 4 by printing or other means.

Switching between the right side power supply and the left side power supply of the strip 1 is performed by a pair of PIN diodes 11 and 12. Each PIN diode is connected from the coupling point of the pair of transmission lines 5 and 6 to the common coupling point 13. The connection point 13 is connected to the ground plane 2 via the substrate 4. Diode 11,
When a suitable DC potential is applied to 12, the antenna is switched by selectively shorting one of the power supply lines. The operation of the switch S1 is performed by the diode 11 and the quarter wavelength line 5 on the left side. The operation of the switch S2 is carried out by the diode 12 and the right quarter wavelength line 5. The operation of the switch S3 is performed by the diode 11 or 12
And the left or right quarter-wave line 6.

The diodes 11 and 12 are connected so that when one is forward biased, the other is reverse biased. The bias potential is supplied to the diode from the DC control input 14 through the resistor 15 and the quarter-wave line 16, the common feed point 7, and the left / right transmission line 6. An RF bias capacitor 24 is connected from the junction of resistor 15 and line 16 to ground through junction 17 which connects to ground plane 2 through substrate 4.

FIG. 4 and FIG. 5 show the current distribution of the right / left side power supply. Reference numeral 18 shows an image current of the ground plane, and 19 shows a current distribution of the monopole 1. 20 is the minimum current point, 21
Is the maximum current point.

The current distribution determines the radiation field of the monopole 1. The current maximum is vertical and the radiated field is
It is equivalent to the radiation field of a half-wave dipole perpendicular to the current maximum. The maximum current on the left and right is almost 1
Since they are separated by / 4 wavelength, spatial diversity equivalent to moving the vertical 1/2 wavelength dipole by the distance of the current maximum point is provided.

The operation is as follows.

When a positive DC voltage is applied to the DC control input, the right side of the monopole 1 is fed with a maximum RF current 22 (FIG. 4). The PIN diode 11 is biased on and shorts the left coupling point of the transmission lines 5, 6 to the ground plane.
The PIN diode 12 is off and has no effect. Therefore, an open circuit is formed between the left side of the monopole 1 and the common feeding point 7, and the RF current becomes maximum on the right side of the monopole (reference numeral 22).

When a negative DC voltage is applied to the DC control input 14, the situation is reversed and the left end of the monopole 1 is fed with a maximum RF current 23 (FIG. 5). PIN diode 12 is biased on and PIN diode 11 is off.

The DC voltage at the terminal 14 periodically repeats above and below the ground potential to supply power to the monopole 1 from the left or the right, or maintains one polarity to deteriorate the signal state. Power is continuously supplied from only one side until switching is required. In the latter case, the signal state is monitored by a circuit (not shown) to which the antenna is connected, and a control signal for switching the polarity of the DC bias voltage at the terminal 14 is generated when necessary.

The 1/4 wavelength line 16 for DC power supply is always open to RF (high frequency) due to the operation of the capacitor 24. The RF input 8 is blocked by the capacitor 10 for the direct current at the input 14. The signals at input 8 (RF) and input 14 (DC) are to ground plane 2.

[0018]

The above antenna is effective in saving space in a portable device because it provides a diversity effect with a single antenna element. The present invention is particularly useful for time division multiplex communication systems (TDM) and also cordless C.
It is also used as a transceiver antenna for T2 telephone handsets.

[Brief description of drawings]

FIG. 1 is a configuration example of a diversity antenna according to the present invention.

FIG. 2 shows a configuration of a printed wiring circuit.

FIG. 3 shows parts similar to FIG. 2 but additionally required for switching.

FIG. 4 shows a current distribution of right side power feeding.

FIG. 5 shows a current distribution of left side power feeding.

[Explanation of symbols]

 1 antenna element S1, S2, S3 switch 2 ground plane 3 common feeding point 4 substrate 5, 6 transmission line 7 feeding point 11, 12 PIN diode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Graham Edgar Beesley United Kingdom, Hampshire, Winchester ESO 21 2NJ, Sparseholt, Church Lane, Upcott cottage (no house number)

Claims (9)

[Claims] 1. A diversity antenna comprising a single antenna element and driving means for driving the element from two separated positions so that the maximum current points are separated. 2. The diversity antenna according to claim 1, wherein the position is an end portion of the antenna. 3. The diversity antenna according to claim 1, wherein the driving means has a switch means for switching a feeding point of the antenna between the two positions. 4. The diversity antenna according to claim 3, wherein the switch means includes a switching diode. 5. RF for feeding an RF signal to an antenna element
3. A power feeding point, spaced RF coupling means for feeding an RF signal to each position of the antenna element through the switch means, and means for operating the switch means to change the power feeding position of the antenna element. 4. The diversity antenna according to 4 above. 6. The diversity antenna according to claim 5, wherein said switch means forms a shunt with respect to the RF coupling means. 7. A DC feed point is provided for applying a DC bias voltage to bias the switching diode, one RF coupling means is shorted to ground and the other R coupling means.
7. The diversity antenna according to claim 4, wherein the F coupling means is not short-circuited. 8. The diversity antenna according to claim 7, wherein a square wave defining two different DC levels for switching the diode is applied to the DC feeding point to alternately and periodically switch the feeding position of the antenna element. 9. The diversity antenna according to claim 7, further comprising means for changing the DC potential applied to the DC feeding point according to the state of the RF signal, and switching the feeding point of the antenna element only when necessary according to the state.