JP2802203B2 - Digital cordless telephone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital cordless telephone having a pair of antennas, and more particularly, to a digital cordless telephone in which an antenna connected to a transmitting circuit is switched in superframe transmission.

[0002]

2. Description of the Related Art In a cordless telephone using wireless communication using analog signals, the number of usable channels is limited. Therefore, in an environment where many cordless telephones are used at the same time, many telephones cannot be used due to the limitation of the number of channels, and the use of digital cordless telephones has been proposed to solve these problems. ing.

In this digital cordless telephone, a super frame is always transmitted from a master unit using a control channel, and a slave unit can transmit or receive a call based on the received super frame. It is configured to take out information such as the presence of information and perform an operation corresponding to the taken out information.

[0004]

However, the frequencies used for communication such as the above-described superframes include:
Since an extremely high frequency in the vicinity of 2 GHz is employed, the transmitted radio wave is extremely easily reflected by a wall or the like in an installation environment, and a phenomenon occurs that the reflected wave and the direct wave interfere with each other.

FIG. 5 is an explanatory diagram showing the relationship between the distance from the antenna of the master unit to the slave unit and the electric field strength of the radio wave used for superframe transmission. This will be described in detail with reference to the drawing, where the distance from the antenna to the slave unit is d91 and d9.
At the position 2, the phase of the reflected wave and the phase of the direct wave are mutually 1
Because they differ by 80 degrees, the interference between the reflected wave and the direct wave at these positions acts in the direction of weakening the electric field strength. Therefore, if there is no interference, the electric field strength L, which is the lower limit of reception,
The electric field intensity is lower than the lower limit due to interference where the electric field intensity is higher than 91.

In other words, the superframe cannot be received even though the slave unit is located within the superframe receivable range (indicated by d93 in the figure). However, there is a problem that the installation position of the slave unit is limited even in the receivable range.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a digital cordless telephone capable of eliminating a superframe receivable position occurring within a superframe receivable range. Is to do.

[0008]

In order to solve the above-mentioned problems, a digital cordless telephone according to the present invention comprises: a pair of antennas having different mounting positions in a horizontal plane;
A transmission circuit for transmitting at least a superframe,
When one of a pair of antennas is used as a first antenna and the other is used as a second antenna, an antenna changeover switch that connects a transmission circuit to the first antenna or the second antenna and a partition that is a unit of a superframe Is a unit superframe, an antenna switching control unit that switches the connection of the antenna switch every time the transmission of the unit superframe is completed a plurality of times is provided.

[0009]

The first antenna and the second antenna have different attachments in a horizontal plane.
The position where the phase of the direct wave of the radio wave transmitted from the second antenna and the phase of the interference wave differ by 180 degrees is the position where the phase of the direct wave and the phase of the interference wave of the radio wave transmitted from the second antenna are 18
It is not the same for positions that differ by 0 degrees. as a result,
Because the phase of the direct wave of the radio wave from one antenna and the phase of the interference wave are different by 180 degrees, even when the electric field strength at that position becomes less than the reception limit value, the electric field strength of the radio wave from the other antenna is It does not fall below the reception limit.

[0010]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an electrical configuration of an embodiment of a base unit of a digital cordless telephone according to the present invention.

In FIG. 1, a diversity antenna 10 attached to a base unit main body (not shown) has first antennas 11 having different attachment positions on a horizontal plane.
And the second antenna 12. The first antenna 11 is connected to the contact a of the antenna changeover switch 13, and the second antenna 12 is connected to the contact b of the switch 13.

The contact c of the antenna change-over switch 13 is guided to a transmission / reception change-over switch 14 for connecting the diversity antenna 10 to the reception circuit 15 or the transmission circuit 16 for connection. The signal indicating the response from the device and the signal indicating the voice) are sent to the control unit indicated by the broken line 22. The output from the control unit 22 (a signal indicating a superframe and a signal indicating a voice) are transmitted to the transmission circuit 16.
Is given.

The control unit 22 includes a switch control unit 18 whose control output C1 is guided to the antenna changeover switch 13, a counter 19 whose output is guided to the changeover control unit 18, and a control output C2 which controls the transmission / reception changeover switch 14. The transmission / reception control unit 21 is guided to the reception circuit 15 and the transmission circuit 16, and the output thereof is configured by a superframe information creation unit 20 guided to the counter 19 and the transmission / reception control unit 21.

Then, the super frame information creating section 20
Is configured to send information indicating the created superframe to the transmission / reception control unit 21 and send a signal to the counter 19 every time the creation of a unit superframe, which is information that is one unit of the superframe, is completed. ing.

The counter 19 counts the number of signals sent from the superframe information creating unit 20, and when the count value reaches a preset value n, the value becomes n. The switching control unit 18
And reset itself.

The switching control unit 18 is a block for switching the connection of the antenna switch 13 every time a signal is supplied from the counter 19, and the transmission / reception control unit 21 sends the superframe information to the transmission circuit 16. In addition to the transmission, the operation of each of the transmission / reception switch 14, the reception circuit 15, and the transmission circuit 16 is controlled.

The analog line interface 24 to which the telephone line 25 is connected is a block for performing a call operation to the telephone line 25, detecting an incoming call, etc., and converting a voice signal into an internal standard signal.

The analog line interface 24
The audio circuit 23 bidirectionally connected to each of the control unit 22 and the control unit 22 is received by the reception circuit 15 and
2 converts the digital audio signal into an analog audio signal and converts it into an analog line interface 24.
, And converts an analog audio signal transmitted from the analog line interface 24 into a digital audio signal, and transmits the digital audio signal to the control unit 22.

The antenna switching control unit 17 according to the first aspect of the present invention is configured by two blocks of the switching control unit 18 and the counter 19 in the above configuration.

FIG. 2 is an explanatory diagram showing the timing of superframe transmission and antenna switching, FIG. 3 is a flowchart showing the main operation of this embodiment, and FIG. It is explanatory drawing which shows the relationship with intensity | strength. The operation of one embodiment of the present invention will be described below with reference to FIG.

When transmitting a super frame, the transmission / reception control unit 21 controls the transmission / reception switch 14 as an initial setting so that the output of the transmission circuit 16 is connected to the c-contact of the antenna switch 13, and the transmission circuit 1
6 is set to the operating state, and the receiving circuit 15 is set to the non-operating state.
Further, the counter 19 is set to a value 0 as an initial value, and the switching control unit 18 connects the c contact of the antenna switch 13 to the a contact.

On the other hand, a superframe is composed of a plurality of identical unit superframes, and a unit superframe is composed of a plurality of superframe elements. The creation unit 20 first creates a superframe element.

Next, the created superframe element is transmitted to the transmission circuit 16 via the transmission / reception control unit 21, and the radio wave indicating the superframe element is transmitted to the first circuit to which the output of the transmission circuit 16 is guided. It is transmitted from the antenna 11.

Hereinafter, the superframe information creating section 20
Sends the created superframe element to the transmission circuit 16 via the transmission / reception control unit 21 every time the superframe element is created. Therefore, the created superframe elements are sequentially transmitted from the first antenna 11 (step S11).

When the creation of all the superframe elements constituting the unit superframe is completed, the superframe information creation unit 20 sends an output indicating the completion of the creation of the unit superframe to the counter 19.
Therefore, the counter 19 to which this output is derived counts up the count value by one according to the output (step S13).

Thereafter, the superframe information creating section 20
Repeats the above operation again, and when the creation of all the superframe elements constituting the unit superframe and the sending of the created superframe elements to the transmission circuit 16 are completed, sends the output to the counter 19 again. . The counter 19 performs a counting operation according to this output, and increases the count value by one (steps S11 to S11).
S13).

The above operation is repeated thereafter.
When the count value of the counter 19 reaches the preset value n, the counter 19 sends a signal notifying that the value has reached n to the switching control unit 18. As a result, the switching control unit 18 performs control to switch the connection of the c contact of the antenna switch 13 from the a contact to the b contact. Further, the counter 19 resets itself and sets its value to 0 (steps S14 to S16).

Then, in the connection state where the output of the transmission circuit 16 is guided to the second antenna 12, as described above,
Super frame element is super frame information creation unit 2
The superframe elements generated one after another by 0 are guided to the transmission circuit 16 and transmitted (steps S11 and S12).

Each time the transmission of the unit superframe is completed, the value of the counter 19 is counted up. When the count value becomes the value n, the switching control unit 18 disconnects the c-contact of the antenna changeover switch 13. The contact is switched from the contact b to the contact a, and the first antenna 11 is connected to the transmission circuit 16 again (step S13).
To S16).

Hereinafter, the same operation is repeated.

The above operation will be described with reference to FIG. 2. At time T11, the first antenna 11 is connected to the transmission circuit 16, and during the subsequent period t11, the transmission of the unit superframe n times will cause the first antenna 11 to transmit. It is performed using.

The time T12 at which the period t11 ends
Then, the second antenna 12 is connected to the transmission circuit 16, and during the period t12, the unit antenna 12 transmits the unit superframe n times. Then, in a period t13 starting from the time T13, the unit superframe is transmitted again n times using the first antenna 11. Hereinafter, the same is repeated.

The operation at the time of transmitting the superframe has been described above, and then the description will be shifted to the relationship between the reception position and the electric field strength.

Now, assuming that the installation position of the slave unit is a distance d11 (see FIG. 4) with respect to the first antenna 11.
Since the electric field strength of the radio wave transmitted from the first antenna 11 is indicated by the solid line 31, the electric field strength at the installation position of the slave unit can be received when the superframe is transmitted using the first antenna 11. The level is below the limit L11. That is, a state in which the reliable reception of the superframe is not guaranteed.

However, as described above, the superframe is activated by the second antenna 12 after a certain period of time.
, The electric field strength at the installation position of the slave unit at this time is L13 (the electric field strength of the radio wave from the second antenna 12 is indicated by a broken line 32), and the reception limit It will be a level that fully satisfies L11,
Super frame reception is guaranteed.

Further, when the installation position of the slave unit is a distance d12 with respect to the first antenna 11, when the superframe is transmitted from the second antenna 12, the reception limit L11
As described below, when a superframe is transmitted from the first antenna 11, the level becomes a level that sufficiently satisfies the reception limit L11.

Hereinafter, at the distance d13, the second antenna 12
In the distance d14, the radio wave from the first antenna 11 satisfies the reception limit L11, and the reception of the superframe is guaranteed regardless of the position within the distance d15 which is the superframe receivable range. Will be done.

The distance a shown in FIG. 4 indicates the difference between the mounting position of the first antenna 11 and the mounting position of the second antenna 12 in the horizontal direction. The distance value indicates a difference along a certain distance direction.

The description of the relationship between the installation position of the slave unit and the electric field strength has been completed above, and the accompanying operation will be described below.

When the slave responds to the transmission of the above-described superframe, the transmission from the slave and the transmission from the master are performed by a time division method using the same frequency band. Then, the radio wave transmitted from the slave unit at this time is received by the receiving circuit 15. The transmission of radio waves to the slave unit is performed using the transmission circuit 16.

The present invention is not limited to the above embodiment,
Regarding the timing of switching the connection between the first antenna 11 or the second antenna 12 and the transmission circuit 16, a case has been described where the antenna connection is switched every time a unit superframe is transmitted n times. As another configuration, as long as the unit superframe is always transmitted a plurality of times in each of the first antenna 11 and the second antenna 12, the number of transmissions of the unit superframe in each antenna is Any number of times is possible.

[0043]

The digital cordless telephone according to the present invention includes a pair of antennas having different mounting positions in a horizontal plane, a transmission circuit for transmitting at least a superframe, and an antenna switching control unit. Since the antenna for transmission is switched each time the transmission of a unit superframe is completed a plurality of times, the radio wave from one of the antennas is limited as long as the reception position is within the receivable range of the superframe. Even when the value is equal to or less than the value, the radio wave from the other antenna is equal to or more than the reception limit value, so that it is possible to eliminate an unreceivable position of the super frame within the super frame receivable range.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electrical configuration of a digital cordless telephone according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the timing of superframe transmission and antenna switching.

FIG. 3 is a flowchart showing a main operation of one embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a relationship between a distance of a base unit from an antenna and an electric field intensity.

FIG. 5 is an explanatory diagram showing the relationship between the distance of a base unit from an antenna and the electric field strength in the conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 1st antenna 12 2nd antenna 13 Antenna switch 16 Transmission circuit 17 Antenna switch control part

Claims (1)

(57) [Claims] 1. A pair of antennas having different mounting positions in a horizontal plane, a transmission circuit for transmitting at least a superframe, and one of the pair of antennas as a first antenna and the other as a second antenna. When the transmission circuit is connected to a first antenna or a second antenna, an antenna changeover switch is connected to the first antenna or the second antenna. A digital cordless telephone, comprising: an antenna switching control unit that switches connection of the antenna switching switch each time the process is completed.