JPH02217028A - Cordless telephone system for mobile communication - Google Patents

Abstract

PURPOSE:To prevent the generation of radio interference disturbance inherent to a cordless telephone system for mobile communication by determining a secondary carrier frequency between a master set and a slave set with primary carrier frequency. CONSTITUTION:The size of a communication area between the master set and the slave set is extremetely small as compared to the sizes of small radio zones (a) to (c), the range of high possibility for the generation of radio interference disturbance is included in the same small radio zones (a) to (c) and a mobile station 10 for the same primary carrier frequency signal does not exist in the same small radio zones (a) to (c). Namely, the primary carrier frequency for an incoming line or an outgoing line between a mobile telephone base station 20 and the master set is received by the master set and the slave set, the received signals are respectively divided at their frequency and directly utilized as a 1st local oscillation signal for forming a secondary carrier for executing transmission/reception between the master set and the slave set. Consequently, a secondary carrier frequency components are not overlapped in a communication enable range between the master set and the slave set and radio interference inherent to the cordless telephone system can be evaded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a cordless telephone device for mobile communications, particularly a mobile station of a base station for mobile telephones that is installed in a mobile body such as a car and uses a general telephone public network. The present invention relates to a mobile communication telephone device that performs telephone communication.

[Prior Art] In recent years, mobile stations mounted on moving objects such as cars and trains,
Mobile telephone communication has been widely put into practical use, in which base stations, which are fixed stations, are connected by wireless communication, and telephone communication is performed from the base stations using the general telephone public network.

Further, as the mobile station, there is a cordless telephone device consisting of a base unit and a handset unit connected by wireless communication, and the telephone device has the advantage that it can be used not only inside the car but also outside the car. Because of this, it is becoming widely used.

Hereinafter, a cordless telephone device for mobile communication, for example a cordless telephone device for a car phone, will be explained.

First, FIG. 2 shows a schematic diagram of a car telephone communication system.

In the figure, 10a and 10b are mobile stations, and 20
a, 20b, and 20c are base stations for car telephones; 30 is a base control station that controls the base stations 20a, 20b, and 20c, respectively; and 40 is a switching center for car telephones. As shown in the figure, the car phone service area SA is divided into multiple small wireless zones a, b, and c with a radius of 5 km to 20 km, and each small wireless zone a, b, and c has a car phone base station. 20 a, 20 b, 2
0c are provided respectively. At this time, each of the base stations 20a, 20b.

The primary carrier frequencies for the uplink (from the mobile station to the base station) line and the downlink (from the base station to the mobile station) line between the mobile station 20c and each mobile station 10a, 10b are set in the adjacent small wireless zone a. , b, and c do not use the same frequency, and the same primary carrier frequency is not used simultaneously within the same small radio zone a, b, and c.

Next, transmission and reception of primary transmission signals between the mobile station 10a and the base station 20a will be explained.

First, when the telephone device of the mobile station 10a is placed in an off-footer state, the base station 20a is placed in the uplink free space 1 in wireless zone a.
The next carrier frequency fit is selected and a signal indicating this first carrier frequency fH is transmitted to the mobile station 10a. At this time, the downlink primary carrier frequency fir is automatically set to a value with a certain frequency difference from the flt.

In response, the mobile station 10a converts primary transmission signals such as dial signals and voice signals based on the carrier signal of the primary carrier frequency fit, and transmits the converted signals to the base station 20a, and Telephone communication is possible with a desired party via the telephone switching center 40 and using the general public telephone network NW.

On the other hand, the voice signal from the called party is converted into a primary transmission signal of the primary carrier frequency fir at the base station 20a, and is transmitted to the mobile station 10a, in reverse of the above-described operation.

In this way, the mobile station 10a can perform telephone communication via the base station 2081, the base control station 30, and the mobile phone switching center 40.

In addition, the base station 20a transmits and receives primary transmission signals to and from the mobile station 10a, and monitors the reception quality of the primary transmission signal from the mobile station 10a, and when the reception quality falls below a certain value, the mobile station 10a Assuming that the mobile station 10a is leaving the current small wireless zone a, the mobile station 10a is connected to the base stations 20b and 20c of the adjacent small wireless zones b and C via the base control station 30.
and request reception quality monitoring.

The base control station 30 then selects the base station with the highest reception quality among the adjacent small wireless zones (in the example of FIG. 2, base station 2
0c) and connects the mobile station 1 via the currently connected base station 20a.
Select the primary carrier frequency of 0a from fIt, flr and select the vacant frequency of base station 20c, for example f3t,
Change to f3r.

Therefore, even if the mobile station 10a moves freely within each of the small fish line zones a, b, and c of the service area SA, telephone communication is always possible.

Next, the mobile station 10 will be explained based on FIG.

The mobile station 10 includes a base unit 100 and a handset unit 120 that are connected via wireless communication in order to make cordless calls.

The base unit 100 includes a primary transceiver 102 that transmits and receives primary transmission signals to and from a base station (not shown), and an observation transceiver 104 that transmits and receives secondary transmission signals to and from the slave unit 120.
, a primary/secondary signal converter 106 that converts the primary transmission signal received from the base station into a secondary transmission signal, and a secondary transmission signal received by the observation transceiver 104 into a primary transmission signal. and a secondary/primary signal converter 108 for converting the signal.

The slave unit 120 also includes a slave transceiver 122 that transmits and receives secondary transmission signals to and from the base unit 100, and a secondary/audio signal that converts the secondary transmission signal received from the base unit lOO into an audio signal. The conversion unit 124 converts dial signals and audio signals into 2
an audio/secondary signal converter 126 that converts into a next transmission signal;
It consists of

Therefore, if such a telephone is used, it is possible to carry out cordless telephone communication not only inside the car but also by taking the handset unit 120 out of the car within a radius of 10 m to 20 m from the base unit 100. It becomes possible.

Furthermore, in the cordless telephone device described above, there are those in which the secondary carrier frequency of the secondary transmission signal is fixed, and those in which the secondary carrier frequency signal is selected from a plurality of types of frequencies.

The latter telephone device is a telephone device with a carrier sense function, and at the time of starting communication, two phones are already in use in the communicable area between the base unit and the slave unit (range of about 10m to 20m from the base unit).
The system detects the next carrier frequency and selects an unused frequency from among multiple preset frequencies as the second carrier frequency, and multiple cordless phones are fixedly placed in close proximity. It has the advantage of not causing interference.

[Problems to be Solved by the Invention] However, since conventional cordless telephone devices for mobile communication are installed in moving objects such as automobiles, even if the telephone device has the above-mentioned carrier sense function, , since the secondary carrier frequency is fixed, the same 2
There was a problem in that interference occurred when approaching another mobile station that was talking on the next carrier frequency.

In addition, in the past, the applicant has filed a patent application for patent application No.
As No. 38, we proposed a device that uses the primary carrier frequency between the base station and base unit to form a desired secondary carrier frequency using a synthesizer, but this device requires a complicated circuit such as a synthesizer. There was a problem.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to avoid interference peculiar to cordless telephone devices for mobile communication.

[Means for Solving the Problems] In order to achieve the above object, the mobile communication cordless telephone device according to the present invention has a communication area between the base unit and the handset unit whose size is the same as that of the small wireless zone. The range in which the above-mentioned interference is likely to occur is within the same small radio zone, and there are
Focusing on the fact that there is no mobile station for the next carrier frequency signal, the primary carrier frequency for the uplink or downlink between the mobile phone base station and the base unit is transmitted by the antenna in the base unit and handset unit. It is characterized in that it is directly used as a first local oscillation signal for forming a secondary carrier that is received and frequency-divided and transmitted and received between the base unit and the slave unit.

[Function] The cordless telephone device for mobile communication according to the present invention is configured as described above, and directly detects and divides the primary carrier frequency between the base station and the mobile station to transmit the 2nd frequency between the base unit and the handset unit. Since the next carrier frequency is determined, the second carrier frequency does not overlap in the communicable range between the base unit and the handset unit, and interference peculiar to cordless telephone devices can be avoided.

In addition, since the device of the present invention constantly monitors the primary carrier frequency, when a mobile object moves to another small wireless zone, the secondary carrier frequency is changed according to the updated primary carrier frequency. Therefore, interference can be avoided even if the mobile station moves to another small wireless zone.

[Example code] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

In this embodiment, an example in which the present invention is applied to a cordless telephone device using weak radio waves for a car phone will be described.

In FIG. 1, a cordless telephone device installed in a car usually consists of a main body 140 fixed to the car body, a main unit part 100, and a handset part 120 that can be removed from the car body. A transmitting/receiving antenna 160 is provided for transmission, and the primary carrier frequency for transmission is fit.
Transmission and reception of the primary carrier frequency fir for reception is performed. In the embodiment, the transmission primary carrier frequency f
It uses a range of 925 to 940 MHz.

Furthermore, as is well known, within one wireless zone within the carrier frequency range, the channel spacing is set at 12.5 KHz in high demand areas and 25 KHz in other areas, and within the same service area, base station equipment technology For reasons of 25 channel spacing or 12.5K
It is operated at HzX25-312° 5KHz intervals.

Therefore, it is understood that within the same service area, the closest first carrier frequencies also have a frequency difference of at least 312.5 KHz. The present invention is characterized in that this primary carrier frequency is directly received and frequency-divided to be used as a first local oscillation signal that forms a secondary carrier frequency between the base unit and the slave unit.

Cordless devices that use weak radio waves that use weak radio waves between the base unit and the slave unit have a transmission frequency of 46MHz and 46MHz.
It is commonly used in the 9 MHz band, and aspects in this band will be described below in Examples.

The main unit 100 has a transmitting circuit for secondarily modulating the received signal R from the main unit 140 and transmitting it to the slave unit 120, and this transmitting circuit has a transmitting unit 50 including a modulator. The transmitter 50 performs FM modulation on the received signal R to generate an intermediate frequency transmit signal f (IFTI), which is sent to the mixer 52.
It is mixed with the first local oscillation frequency fLl characteristic of the present invention, which will be described in detail later in , and sent to the slave unit 120 as a secondary transmission signal fT1 from the parent and child antenna 5δ via the duplexer 54.
send towards.

Further, the uplink secondary transmission signal transmitted from the handset unit 120 side toward the base unit 100 is received by the parent-child antenna 56 and guided to the demultiplexer 54 as a signal fR1, and this signal is sent to the mixer 58 at the 1 local oscillation signal fL1 and output to the receiving unit 60 as an intermediate frequency received signal f (IFRI).
is supplied to The receiving section 60 includes an amplification and a detector, and supplies the signal to the main body 140 as a transmission signal T after frequency conversion (for example, 455 Kl(z)), amplification, and amplitude limitation.

A characteristic feature of the present invention is that the first local oscillation signal fLl is directly formed by frequency division of the primary carrier frequency between the base station and base unit 100, and for this reason, A primary carrier monitoring antenna 62 is provided within the base unit 100, and in the embodiment, detects the transmission primary carrier frequency flt (925 MHz).

The received primary carrier frequency is supplied from the amplifier 64 to the frequency divider δδ, where it is subjected to a predetermined frequency division operation. In the example, this frequency division ratio is set to 1/32,
For example, if the primary carrier frequency is 925 to 940 Mllz
If , the frequency-divided signal is 28.90625 to 29.
It is understood that the frequency is 375 MHz. According to the present invention, this frequency-divided signal is used as the first local oscillation signal fL1, and in the embodiment, since the output of the frequency divider 66 is a square wave, it is converted into a sine waveform by the bandpass filter 68. ing. Therefore, according to the present invention, the base unit 100 directly outputs the node 1 local oscillation signal fLl from the primary carrier frequency.
Since the secondary carrier frequency within the same wireless zone does not interfere with other cordless telephone devices, the secondary carrier frequency is also automatically changed when switching wireless zones, so that the secondary carrier frequency can be transmitted to other zones. Interference between cordless signals between parent and child can be automatically prevented when moving.
Furthermore, as is clear from the configuration of the base unit 100, the first
In order to obtain the local oscillation signal fLl, it is possible to obtain the first local oscillation signal fLl extremely easily using only a primary carrier monitoring antenna and a frequency divider, without requiring a synthesizer or other complicated configuration. Become.

As an example, the secondary carrier frequency fT1 for transmission is set to 46
Ml(z, and the receiving secondary carrier frequency fR1 is 4
9MHz, and the primary carrier frequency is 925MHz.
In this case, each frequency is determined as follows.

First, the first local oscillation signal fLl is 925MHz+32
-28.90625MHz, and as a result, the transmitter 5
The intermediate frequency at 0 is determined to be 17.09375MHz,
Also, the intermediate frequency at the receiving section 60 is 20°09375M+
It is determined as Iz.

By changing the primary carrier frequency, each of these frequencies changes the first local oscillation signal fL1 and the secondary carrier frequencies fTl and fRl by a predetermined frequency difference.

The handset unit 120 according to the present invention also has the same configuration as the base unit 100, and corresponding constituent members are designated by the reference numeral 200 and their explanation will be omitted.

In the handset section 120 , a transmission signal is supplied from the microphone 70 to the transmission section 250 , and the output of the reception section 260 is supplied to the speaker 71 .

The slave unit 120 differs from the base unit 100 in that the detected and frequency-divided first local oscillation signal fL1 is mixed with the output of the fixed frequency oscillator 72 by a mixer 74, and this fixed frequency fL2 is 3 in the example
7. The frequency is set to 1875 MHz, and as a result, the mixer output fL3 is determined to be 66.09375 M)Iz.

As a result, the transmitting section 250 in the handset section 120
And the receiving unit 260 receives the base unit 100 by the frequency conversion.
It can be shared with the transmitting section 50 and receiving section 60 of.

In the embodiment shown in FIG.
and a parent and child antenna 56, 256, each part 1
00.120, it is also possible to share the carrier monitoring antenna and the parent and child antennas, and if necessary, these shared antennas can be built into the device.

In addition, in the embodiment shown in FIG. 1, the fixed frequency oscillator 73 and mixer 74 are used to convert the frequency to generate the secondary carrier in the slave unit 120 in order to match the transmitting and receiving frequencies with the base unit. A similar effect can be obtained by making the configuration similar to that of the slave unit and the configuration of the slave unit similar to that of the base unit.

Further, in the present invention, the various antennas described above may be specially configured as an antenna device, or may be formed simply from conductor wires routed for receiving radio waves.

[Effects of the Invention] As explained above, according to the cordless telephone device for mobile communication according to the present invention, the effective frequency range between the base unit and the handset unit is always within the small wireless zone, and - Since different primary carrier frequencies are always assigned to mobile stations within a small radio zone, by determining the secondary carrier frequency between the base unit and handset unit based on the primary carrier frequency, it is possible to This has the effect of not causing interference even when mobile stations are close to each other.

Further, according to the present invention, in order to obtain the first local oscillation signal, it is only necessary to directly receive the primary carrier frequency with an antenna and divide it, eliminating the need for a synthesizer or the like that requires a complicated configuration. There are some advantages.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram of the main parts of a cordless telephone device for mobile phone communication according to the present invention, FIG. 2 is an explanatory diagram of a car phone communication system, and FIG. 3 is a schematic configuration diagram of a conventional car phone device. be. 10a, IQb --- Mobile stations 20a, 20b, 20c --- Base station 30...
Base control station 40 ... Car telephone exchange 62.262 ... Primary carrier monitoring antenna 6
6.266... Frequency divider 120... Slave unit fLl... First local oscillation signal

Claims (1)

[Scope of Claims] A mobile communication telephone device that is mounted on a mobile body such as a car and performs telephone communication as a mobile station of a mobile telephone base station using a general telephone public network, the mobile station comprising: In a cordless telephone device for mobile communication including a base unit and a handset unit connected by wireless communication, the base unit and handset unit include a primary carrier for transmission or reception between a base station and a mobile station. The receiving antenna and this one
Frequency dividers that divide the next carrier frequency are provided, and the divided signals that change according to the first carrier frequency are transmitted and received between the base unit and the slave unit to form a secondary carrier signal. 1. A cordless telephone device for mobile communication, characterized in that the cordless telephone device is directly used as a first local oscillation signal for the purpose of transmitting a signal.