JPH07303079A - Noise preventing circuit - Google Patents

Abstract

PURPOSE:To provide a miniaturized and effective noise preventing circuit for a portable telephone set. CONSTITUTION:Concerning the noise preventing circuit for portable telephone set to communicate with a communication channel designated from a base station by providing plural communication channels, memory, clock signal oscillating circuit and control part to be operated by a clock signal, the clock signal oscillating circuit 11 can control a clock signal frequency corresponding to a control signal (a) and a memory 8 previously stores the value of the control signal (a) for generating the prescribed clock signal frequency and information showing whether mutual interference is generated between the clock signal frequency and the communication channel. When any communication channel is designated from the base station, while referring to the memory 8, the control part 8 adjusts the clock signal oscillating circuit 11 by selecting the value of the control signal (a) for generating the clock signal frequency not to be interfered with that communication channel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise prevention circuit for preventing a communication failure due to a clock signal of a control unit of a portable telephone or its harmonics.

[0002]

2. Description of the Related Art In recent mobile phones and the like, in addition to a receiving circuit for receiving a radio signal from a base station, a transmitting circuit for transmitting a radio signal to the base station, a voice signal processing unit for processing voice, channel control, call control, etc. Is provided with a control unit for controlling the entire telephone, and the control unit is a CPU that operates with a clock signal.
Is used. For example, 4.8M is applied to the clock signal.
If a signal with a frequency of Hz is used, its harmonics may cause mutual interference with a communication signal in a frequency band used for communication (for example, 860 to 870 MHz), resulting in a communication failure such as a beat failure or a decrease in sensitivity. is there. In such a case, conventionally, the mutual interference is prevented by shielding the communication circuit in the high frequency region or separating the communication circuit from the clock signal in a distance.

[0003]

However, in recent years,
As communication systems have become more sophisticated, communication speeds have increased, and systems have become more complex. Many devices used in communication equipment are also high-speed, but on the other hand, noise generated from the devices is also large. There is a problem of adverse effects on the communication device itself and others. In mobile communications such as mobile phones, downsizing of communication devices is very important, and using shields or separating the communication circuit from the clock signal as in the past increases the size of the device. There was a problem that it would end up.

The present invention has been made in view of the above points, and an object of the present invention is to eliminate the above problems and to provide a compact and effective noise prevention circuit for a mobile phone.

[0005]

In order to solve the above problems, the present invention has a plurality of communication channels, includes a memory, a clock signal oscillation circuit, and a control unit that operates by a clock signal. In a noise prevention circuit of a mobile phone that communicates on a designated communication channel, the clock signal oscillation circuit 11 can control the clock signal frequency by a control signal a as shown in FIG. The value of the control signal a for generating a predetermined clock signal frequency and the information as to whether mutual interference occurs between the clock signal frequency and the communication channel are stored in advance, and the communication channel is designated by the base station. At this time, the control unit 7 refers to the memory 8 and selects a value of the control signal a for generating a clock signal frequency that does not cause mutual interference between the communication channels. And adjusting a lock signal oscillator circuit 11.

[0006]

According to the present invention, the value of the control signal for generating a predetermined clock signal frequency in the memory 8 and the communication channel in which mutual interference does not occur at that frequency or the communication channel in which mutual interference occurs are stored in advance in association with each other. When the communication channel is designated by the base station, the control unit 7 refers to the memory 8 and selects the value of the control signal a for generating a frequency at which mutual interference does not occur, and sets the clock signal frequency to a predetermined frequency. Since the adjustment is performed, mutual interference between the clock signal frequency and the communication frequency does not occur and a communication failure such as a beat failure or a decrease in sensitivity does not occur.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing a configuration example of a mobile phone equipped with the noise prevention circuit of the present invention. As shown in the figure, the mobile phone equipped with the noise prevention circuit of the present invention includes an antenna 1, a receiving circuit 2, a transmitting circuit 3, a voice signal processing unit 4, a transmitter 5, a receiver 6, and a control unit 7 for controlling the entire mobile phone. ,
It comprises a memory 8 for storing programs and data, a channel controller 9 for switching channels, a D / A converter 10 for converting a control signal a into an analog value, and a clock signal oscillating circuit 11.

At the time of reception, the mobile phone receives a radio wave signal from the base station by the antenna 1, demodulates it by the receiving circuit 2, processes it by the voice signal processing unit 4, and outputs the voice from the handset 6. At the time of transmission, a voice signal is output from the transmitter 5, the signal processed by the voice signal processing unit 4 is modulated by the transmission circuit 3, and is transmitted as a radio wave from the antenna 1.

The control unit 7 has a CPU (central processing unit), and the CPU operates with a clock signal of 4.8 MHz oscillated by the clock signal oscillation circuit 11. In addition, the control unit 7 controls the audio signal processing unit 4 and the like, and controls the channel of the receiving circuit 2 and the transmitting circuit 3 through the channel control unit 9 based on a command from the base station to control the entire mobile phone such as protocol processing. .

The memory 8 is a storage device for storing programs executed by the CPU and data, the control section 7 controls the control signal a, and the D / A converter 10 converts the control signal a into an analog value. Then, the frequency of the clock signal, which is an output signal, is adjusted by inputting it to the clock signal oscillation circuit 11.

FIG. 2 is a diagram showing a configuration example of a clock signal oscillator circuit. As shown, the clock signal oscillator circuit 11
Is a resistor 11-1, a variable capacitance diode 11-2, a capacitor 11-3, a crystal oscillator 11-4, a capacitor 11
-5 and an amplifier 11-6.

The clock signal oscillator circuit 11 has a variable capacitance diode 11-2 connected in parallel with the load capacitance (capacitor 11-3) of the crystal oscillator 11-4, and the voltage at the input terminal (D / A converter). The output voltage of the controller 10) is applied to the variable capacitance diode 11-2, the load capacitance is changed by controlling the voltage, and the clock signal frequency as the output is controlled. Control range is ± 75 ppm (4.8 MH
z is about ± 360 Hz).

The operation of the noise prevention circuit will be described below.
In advance, the value of the control signal a for generating the clock signal frequency of 4.8 MHz and the communication channel (or frequency) that does not cause interference at the clock signal frequency of 4.8 MHz are stored in association with each other, and 4.8 MHz + 300 Hz (or A value of a control signal a for generating a clock signal frequency of 4.8 MHz-300 Hz and 4.8 MHz + 300 Hz
(Or 4.8 MHz-300 Hz), communication channels (or frequencies) that do not cause mutual interference are stored in association with each other.

The control unit 7 of the portable telephone is usually 4.8.
It is operating at a clock signal frequency of MHz. The communication channel to be used is designated by the base station, and the control unit 7 controls the switching of the communication channels of the receiving circuit 2 and the transmitting circuit 3 through the channel control unit 9. Further, the control unit 7 compares the communication channel stored in the memory 8 with the designated communication channel, and confirms that the designated communication channel does not cause mutual interference with the clock signal frequency of 4.8 MHz. If interference occurs with the clock signal frequency of 4.8 MHz, the control unit 7 sets the value of the control signal a to the value stored in the memory 8 and sets the clock signal frequency output from the clock signal oscillation circuit 11 to 4. Set to 8MHz + 300Hz.

For example, in the mobile phone, the frequency band used for communication is 860 to 870 MHz, and the clock signal frequency output from the clock signal oscillation circuit 11 is 4.8 MHz.
Then, the harmonics 180 times and 181 times the clock signal frequency become 864 MHz and 868.8 MHz, respectively, and since they fall within the frequency band used for communication, mutual interference occurs in the communication channels using frequencies in the vicinity of these frequencies and a beat failure occurs. It may cause communication failure such as.

In the noise prevention circuit of the present invention, a communication channel which causes a communication failure such as a beat failure in the clock signal of 4.8 MHz in advance (a communication failure does not occur in a clock signal frequency of 4.8 MHz ± 300 Hz). When,
The value of the control signal a for generating the clock signal frequency of 4.8 MHz + 300 Hz is correspondingly stored in the memory 8, and when the channel is designated by the base station, the memory 8 is referred to and the value of the control signal a is set to the channel. Set to the corresponding value and set the clock signal frequency (4.8
MHz or 4.8 MHz ± 300 Hz) to prevent communication failure such as beat failure.

In the above description, the control signal a for generating a predetermined clock signal frequency is stored in the memory 8 in association with a communication channel that does not cause a communication failure and processed. A control signal a for generating a clock signal frequency that does not cause communication failure for a designated communication channel is stored in advance for a control signal a for causing communication failure.
May be selected and output.

[0018]

As described in detail above, according to the present invention, the following excellent effects are expected. (1) The value of a control signal for generating a predetermined clock signal frequency and a communication channel in which mutual interference does not occur at that frequency or a communication channel in which mutual interference occurs in the memory are stored in advance in the memory in correspondence with each other. When a communication channel is designated, the control unit refers to the memory, selects and outputs a control signal for generating a frequency at which mutual interference does not occur, and adjusts the clock signal frequency to a predetermined frequency. Will not cause mutual interference, and will not cause communication failure such as beat failure or sensitivity deterioration. (2) Further, since the shield is not required, the device is small and lightweight.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a mobile phone equipped with a noise prevention circuit of the present invention.

FIG. 2 is a diagram showing a configuration example of a clock signal oscillator circuit.

[Explanation of symbols]

 1 antenna 2 receiving circuit 3 transmitting circuit 4 voice signal processing unit 5 transmitter 6 receiver 7 control unit 8 memory 9 channel control unit 10 D / A converter 11 clock signal oscillator circuit 11-1 resistor 11-2 variable capacity Diode 11-3 Capacitor 11-4 Crystal oscillator 11-5 Capacitor 11-6 Amplifier

Claims (1)

[Claims] 1. A noise prevention circuit for a mobile phone, which has a plurality of communication channels, comprises a storage device, a clock signal generating means, and a control section which operates by a clock signal, and communicates with the communication channel designated by the base station. In the above, the clock signal oscillating means can control the clock signal frequency by a control signal, and the storage device previously communicates with the clock signal frequency and the value of the control signal for generating a predetermined clock signal frequency. Information on whether mutual interference occurs between channels is stored, and when a communication channel is specified by a base station, the control unit refers to the storage device and a clock signal that does not cause mutual interference between the communication channels. A noise prevention circuit characterized in that a value of a control signal for generating a frequency is selected to adjust the clock signal oscillating means.