JP2002368676A - Intermittent reception method, intermittent receiver and mobile communication terminal capable of utilizing them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mobile communication terminal, the power consumption of which is reduced. SOLUTION: An intermittent reception control unit 100 activates a system clock generating section 200, when it is in normal operation and stops the system clock generating section 200 when it is in a sleep state. Thus, the power consumption of the mobile terminal is reduced. Furthermore, in order to facilitate synchronization acquisition of a spread code and a received signal in the case of restoration from sleep state to the normal operating state, a sleep period measurement section 106 measures sleep period, by using a sleep clock and converts the sleep period into the number of system clocks using a clock ratio measured by a clock ratio measurement section 108. Thus, the synchronization timing between the spread code and the received signal can be estimated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discontinuous reception technique. The present invention particularly relates to a method for intermittently receiving a signal, an intermittent receiving device that can use the method, and a mobile communication terminal that can use them.

[0002]

2. Description of the Related Art In recent years, the number of users of wireless communication systems such as portable telephones and PHSs has increased dramatically. The greatest advantage of the mobile phone is that the terminal can be carried when going out, and it is possible to make and receive calls anytime and anywhere. In order to maximize the advantage of being able to carry easily, there is a need for a technology that further extends the time that can be used continuously without charging a mobile phone, that is, the continuous standby time. In fact, when a user chooses a mobile terminal, the length of continuous standby time is an important factor.

[0003] In order to improve the continuous standby time, not only the power consumption when the user is using the mobile phone, such as a telephone call or the display of information on a liquid crystal screen, is reduced, but also the user is required to use the mobile phone. It is important to reduce power consumption when is not used, that is, when waiting for an incoming call. As a technology for reducing power consumption during standby for incoming calls, after receiving a signal for a certain reception time and checking for the presence or absence of an incoming call, a sleep state is set for a predetermined period, and an operation of receiving a signal only for a certain reception period is repeated. A so-called intermittent reception technique is known.

[0004]

Problems to be Solved by the Invention
No. 70 discloses a wake state from a sleep state at a timing that reflects a frequency error and a phase error between a fast clock that stops during sleep and a slow clock that also operates during sleep when a predetermined sleep period has elapsed. Disclose the technology to return to The technique disclosed in this publication relates to a narrowband communication system, but in the case of a code division multiple access (CDMA) system employed in a third generation communication system, a received signal is not transmitted. And a spreading code for despreading the signal and multiplying them in synchronization, the problem becomes more complicated. That is, even when sleeping once and waking, it is necessary to devise a method of realizing re-acquisition of the synchronization between the received signal and the spread code in a short time.

[0005] The present invention has been made in view of such a background, and an object thereof is to provide an efficient intermittent reception technique,
It is an object of the present invention to provide a technology for reducing power consumption of a mobile communication terminal.

[0006]

One embodiment of the present invention relates to a discontinuous reception method. In this method, prior to switching from a normal operation state to a sleep state to receive a signal, a frequency of a first frequency clock for normal operation and a frequency of a second frequency clock for control in sleep state are changed. , Stopping the clock of the first frequency and switching from the normal operation state to the sleep state, and measuring the number of clocks of the second frequency clock over a sleep period. And returning to the normal operation state in synchronization with the clock of the second frequency when a start request is detected during sleep, the ratio of the frequencies, and the measured clock of the second frequency. And calculating the sleep period from the number in units of the clock of the first frequency.

[0007] The clock of the first frequency is supplied to each circuit and CP.
A high-speed system clock used for the operation of U may be used. The clock having the second frequency may be a low-speed sleep clock used for a real-time clock IC or the like. By stopping the high-speed system clock during the sleep period, power consumption can be reduced.
Further, by measuring the sleep period using the sleep clock that operates even during the sleep, the timing when returning from the sleep state to the normal operation state can be aimed at, and the spread code and the reception signal can be easily synchronized. Since the frequency ratio is measured before sleep, the influence of a temperature drift described later can be easily eliminated. A period ratio may be used instead of the clock frequency ratio. Hereinafter, the term "frequency ratio" includes the period ratio.

[0008] Another embodiment of the present invention also relates to a discontinuous reception method. In this method, prior to switching from a normal operation state to a sleep state to receive a signal, a frequency of a first frequency clock for normal operation and a frequency of a second frequency clock for control in sleep state are changed. , Stopping the clock of the first frequency and switching from the normal operation state to the sleep state, and measuring the number of clocks of the second frequency clock over a sleep period. When the number of clocks reaches a predetermined threshold, returning to the normal operation state; and when a start request is detected before the number of clocks reaches the predetermined threshold, Storing the number and returning to the normal operation state in synchronization with the clock of the second frequency; the ratio of the frequencies; From the stored number of clocks or the threshold at-up, and a step of calculating the sleep period as a unit clock for the first frequency.

When there is no activation request during sleep, the operation returns to the normal operation state when a predetermined sleep period has elapsed. When there is an activation request during sleep, normal operation does not wait for the predetermined sleep period to elapse. Returns to the state.
In this case as well, the sleep period is measured by the sleep clock, so that the timing of returning to the normal operation state is determined.

The method may further include counting the number of clocks by a counter element, and when a start request is detected before the number of clocks reaches the predetermined threshold value, the count value of the counter element is determined. , The predetermined threshold value or a value close to the predetermined threshold value may be loaded.

In the method, a step of calculating a remainder when the number of clocks of the clock of the first frequency calculated in the calculating step is divided by a code length of a spreading code for despreading the signal. And estimating a timing of multiplying the signal by the spreading code based on the remainder. This facilitates synchronization acquisition when returning to the normal operation state.

Still another preferred embodiment according to the present invention relates to an intermittent receiving apparatus. This intermittent receiver is a first intermittent receiver for normal operation.
A first clock obtaining unit that obtains a clock signal of a second frequency, a second clock obtaining unit that obtains a clock signal of a second frequency for controlling during sleep, and detecting a sleep request and a start request. A sleep control unit that controls switching between a normal operation state and a sleep state, and stores a ratio between the first frequency and the second frequency when the sleep control unit detects the sleep request. A clock ratio measuring unit that measures the number of clocks of the clock of the second frequency over the period of the sleep state, and calculates the clock of the first frequency during the period of the sleep state from the number of clocks and the ratio. A sleep period measuring unit that calculates the unit as a unit.

Still another preferred embodiment according to the present invention relates to a mobile communication terminal. The mobile communication terminal includes a transmitting unit that modulates and transmits a signal, a receiving unit that receives and demodulates a signal, a control unit that controls the transmitting unit and the receiving unit, and a relatively high-speed first clock. And a sleep state in which signal reception is interrupted while maintaining a minimum system state using a relatively low-speed second clock. An intermittent reception control unit for controlling, the reception unit has a synchronization control unit for synchronizing the signal and a spread code for despreading the signal, and the intermittent reception control unit is set to a normal operation state. A clock ratio measuring unit for measuring a frequency ratio between the first clock and the second clock when shifting to a sleep state; A sleep control unit for stopping the clock and a sleep period measured by the second clock, and when returning from the sleep state to the normal operation state, the sleep period is set to the number of clocks of the first clock based on the frequency ratio. And a sleep period measuring unit for converting to
The synchronization control unit recovers a synchronization state of a system using the number of clocks of the first clock.

Still another preferred embodiment according to the present invention relates to a mobile communication terminal. The mobile communication terminal includes a transmitting unit that modulates and transmits a signal, a receiving unit that receives and demodulates a signal, a control unit that controls the transmitting unit and the receiving unit, and a normal operation state that receives the signal. An intermittent reception control unit that controls switching between a sleep state and a sleep state. The reception unit includes a synchronization control unit that synchronizes the signal and a spread code for despreading the signal, The reception control unit acquires a first clock signal for acquiring a clock signal of a first frequency for normal operation, and acquires a second clock signal for acquiring a clock signal of a second frequency for control during sleep. Department and
A sleep control unit that detects a sleep request and an activation request, and controls switching between the normal operation state and the sleep state, and the first frequency when the sleep control unit detects the sleep request. A clock ratio measurement unit that stores a ratio with the second frequency, and measures the number of clocks of the second frequency over the period of the sleep state, and calculates the period of the sleep state from the number of clocks and the ratio. And a sleep period measurement unit that converts the number of clocks of the first frequency to the number of clocks of the first frequency. The synchronization control unit, when returning from the sleep state to the normal operation state, converts the converted first frequency The timing of multiplying the spread code by the signal is estimated based on the number of clocks.

Still another preferred embodiment according to the present invention relates to a discontinuous reception method. The method uses a relatively fast first clock to receive and process the signal and a relatively slow second clock to maintain a minimum system state while maintaining a minimum system state. In the intermittent reception method in which the sleep state in which reception is interrupted repeats, the frequency ratio between the first clock and the second clock is measured at the time of transition from the normal operation state to the sleep state, and the first clock is measured in the sleep state. The sleep period to the second
When returning from the sleep state to the normal operation state, the sleep period is converted into the number of clocks of the first clock based on the frequency ratio, and the synchronization state of the system by the first clock is measured. Recover.

It is to be noted that any combination of the above-described components and any conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, and the like are also effective as embodiments of the present invention.

[0017]

FIG. 1 shows an overall configuration of a communication terminal 10 according to an embodiment. The communication terminal 10 includes an antenna 80 for transmitting and receiving signals to and from a base station, a receiving unit 20 for receiving and demodulating a signal, a transmitting unit 30 for modulating and transmitting data, a receiving unit 20, and a transmitting unit 30. Control unit 40, a microphone 50 for externally inputting voice information, a speaker 60 for outputting voice information to the outside, an input unit 70 for receiving a key input and the like from outside, and an intermittent reception for controlling intermittent reception when waiting for an incoming call. A control unit 100 is provided. Communication terminal 10
May further include a display unit for displaying text information or image information.

In the present embodiment, communication terminal 10 mainly used in a CDMA communication system of the direct spreading system
Will be described. In this communication system, the communication terminal 10 acquires a modulated signal by synchronizing and multiplying a received signal with a despread code, detects the modulated signal, and decodes the data.

FIG. 2 shows a part of the internal configuration of the receiving unit 20. The receiving unit 20 includes a band-pass filter 22 for removing unnecessary frequency bands of the received signal, a multiplier 24 for multiplying the received signal by a despreading code and despreading, and a signal processing for detecting and decoding the received signal. And a synchronization control unit 28 for synchronizing the received signal with the despread code. The receiving unit 20 may include, in addition to the above configuration, an amplifier for adjusting gain, an automatic gain control mechanism, a mechanism for down-converting the frequency of a received signal to a baseband band, and the like.
Although a configuration required for a general mobile communication terminal of the DMA system is provided, since a conventionally known technique can be used for these configurations, description thereof is omitted here.

The synchronization control unit 28 includes a matched filter for synchronization acquisition, a delay lock loop for synchronization tracking, and the like. Conventionally known techniques can be used for these configurations. As described later, when returning from the sleep state, the synchronization control unit 28 acquires information for synchronization acquisition from the intermittent reception control unit 100, and performs synchronization acquisition by a matched filter or the like based on the information.

FIG. 3 shows the internal configuration of the intermittent reception control unit 100. The function of the intermittent reception control unit 100 is as follows.
In terms of hardware, microcomputers, memories,
It can be realized by other LSI.

The intermittent reception control unit 100 reduces power consumption by intermittently putting the receiving unit 20 to sleep when the communication terminal 10 is in a call waiting state. FIG. 4 is a diagram showing how the receiving unit 20 intermittently receives a signal. When the communication terminal 10 enters the incoming call waiting state, the intermittent reception control unit 100 causes the receiving unit 20 to receive a signal during a predetermined reception period and confirms the presence or absence of an incoming call. If there is no incoming call, the system clock is stopped for a predetermined sleep period (hereinafter, also referred to as “default sleep period”) to put the receiving unit 20 to sleep. Then, when the default sleep period has elapsed, the system clock and the receiving unit 20 are activated again to receive a signal. When the user issues a start request such as a call request during the sleep period, the system clock is started without waiting for the end of the default sleep period.

In the case of the CDMA communication system, it is necessary to synchronize the received signal with the despreading code in order to despread the received signal. However, if the system clock is stopped during the sleep period, the synchronization timing is lost. It is necessary to perform synchronization acquisition again when returning from sleep. Therefore, in the embodiment, the synchronization timing of the despread code at the time of restart is estimated by measuring the sleep period using the sleep clock that is operating even during the sleep period. As a result, the time and power required for synchronization acquisition at the time of restart can be minimized. Here, the reception period is several tens of milliseconds, and the default sleep period is about 1 or 2 seconds. Since the sleep period is at most several seconds, the above estimation is effective.

The system clock obtaining section 102 obtains a system clock used for the operation of the CPU and each circuit from the system clock generating section 200. The sleep clock obtaining unit 104 obtains, from the sleep clock generating unit 202, a sleep clock used for control during sleep and operation of a clock. The entity of the system clock acquisition unit 102 and the sleep clock acquisition unit 104 may be an input buffer, a circuit that divides the system clock and the sleep clock according to a request inside the intermittent reception control unit 100, and the like. When an element is not required, it may be considered that it simply refers to a microstrip line of a clock signal input to the intermittent reception control unit 100, that is, any physical configuration that receives a clock.
Here, the frequency of the system clock is 15.36 MH
z, and the frequency of the sleep clock is 32.768 kHz, which is a crystal oscillation frequency often used for a real-time clock IC or a multiple thereof. That is, the system clock generator 200 supplies a clock signal faster than the sleep clock generator 202. Power consumption is reduced by stopping a system clock that supplies a fast clock signal during sleep.

The sleep period measuring unit 106 measures a period from the sleep state to the return from the sleep state using the system clock and the sleep clock. The sleep period measurement unit 106 first measures the number of system clocks from the time of entering the sleep state to the first rise of the sleep clock. The sleep period measurement unit 106
When the first rise of the sleep clock is detected, the clock to be measured is switched to the sleep clock, and thereafter, the number of sleep clocks is measured. Sleep period measurement unit 1
Reference numeral 06 outputs the measured number of sleep clocks when shifting from the sleep state to the normal operation state. The end timing of the sleep period is when the default sleep period ends or when a start request is issued by the user. By measuring the sleep period with the sleep clock, the system clock can be stopped during sleep.

The clock ratio measuring unit 108 measures the ratio between the frequency of the system clock and the frequency of the sleep clock. Since the sleep period measurement unit 106 measures the sleep period using the sleep clock, a clock ratio is required to convert the sleep period into the number of system clocks. Although the frequencies of the system clock and the sleep clock are predetermined, the frequency of the crystal oscillator that generates the clock slightly varies depending on the temperature. Therefore, measurement is performed to obtain an accurate ratio. The clock ratio measurement unit 108
The clock ratio may be constantly measured during the operation of the system clock, or the clock ratio may be measured prior to transition to the sleep state when a sleep request is issued.

The sleep control unit 110 includes the control unit 4
In response to a sleep request and a start request transmitted from 0 or the like, transition to the sleep state and return from the sleep state are controlled. When detecting the sleep request, the sleep control unit 110 causes the clock ratio measurement unit 108 to store the immediately preceding clock ratio, and instructs the sleep period measurement unit 106 to start measurement. Further, it instructs the power supply control unit 204 to stop the main power supply, and shifts to the sleep state. After the elapse of the default sleep period, the power supply control unit 204 is instructed to start up the main power supply, and the sleep period measurement unit 106 is instructed to output a measurement result. If a start request from the user is detected via the control unit 40 before the default sleep period elapses, the main power supply unit 204 is instructed to start the main power supply, and the normal operation state is synchronized with the rise of the sleep clock. Switch to By synchronizing the end of the sleep period with the sleep clock, measurement errors in the sleep period can be minimized.

FIG. 5 is a diagram for explaining the operation of the intermittent reception control unit 100. However, the figure schematically shows the process and time required for the transition of the operating state greatly reduced for the sake of understanding. Further, it should be noted that the frequency ratio between the system clock HCLK and the sleep clock LCLK is also schematically shown, and differs greatly from the actual ratio. FIG. 5 shows a normal operation mode flag (NMD in the figure) and a sleep request signal (SLPR in
Q), a system clock (same HCLK), a sleep clock (same LCLK), a start request signal (same WKRQ), a main power supply voltage (same MPW), and a main power ready signal (same MPWRDY). Among these, MPW is an actual voltage, and all other signals are high level active signals.

First, at time T0, the sleep control unit 110
Detects the sleep request signal SLPRQ, it shifts from the normal operation to the sleep state in synchronization with the next rise of the system clock HCLK. Sleep period measurement unit 1
06 measures the period t1 from the transition timing T1 to the sleep state to the rise T2 of the next sleep clock LCLK by the number of system clocks. In this example, t1 is two system clocks.
Although it is exactly between two clocks and three clocks, it may be rounded down to two clocks or rounded up to three clocks. At this time, the sleep control unit 110 causes the clock ratio measurement unit 108 to record the frequency ratio m between the system clock and the sleep clock.

The sleep period measuring unit 106 switches the clock to be measured from the system clock to the sleep clock in synchronization with the rise T2 of the sleep clock LCLK, and thereafter measures the number of sleep clocks. Subsequently, sleep control section 110 instructs power supply control section 204 to stop the main power supply, and power supply control section 204 stops the main power supply. As a result, the supply of power to the system clock generation unit 200 is stopped, and the system clock is stopped. The sleep clock operates during sleep.

There are two types of timing for returning from the sleep state to the normal operation. One is a timing at which the default sleep period ends, and the other is a timing at which a start request is detected before the default sleep period ends as a result of the assertion of the user start request signal. These two cases are described below.

In the example shown in FIG. 5, the sleep request signal S
Before LPRQ remains active and before the default sleep period expires, the user may request a wake-up request WKRQ.
Has been issued. When detecting the activation request WKRQ, the sleep control unit 110 instructs the power supply control unit 204 to activate the main power supply. As a result, the main power supply voltage MPW
Rise, and the ready signal MPWRDY of the main power supply becomes active. Thereby, the system clock generator 20
0 operation is resumed, and the system clock is supplied again. The sleep control unit 110 shifts to the normal operation in synchronization with the rise of the sleep clock. However, at the time T3, the power supply is not yet stable and the ready signal MPWRDY of the main power supply is in the LOW state. And wait for a predetermined number of sleep clocks. The sleep control unit 110 confirms that the ready signal MPWRDY of the main power supply at the time T4 is active, and shifts to the normal operation in synchronization with the next rising of the system clock.

At this time, the total sleep period t is the number of system clocks (2 clocks in this example) measured during the period t1 from the transition to the sleep state to the first rise of the sleep clock, and the number of sleep clocks thereafter. (3 clocks in this example) and the number of system clocks (1 clock in this example) measured during a period t3 from the last rise of the sleep clock to the rise of the system clock. When the number of system clocks is converted using the clock ratio m recorded before the transition to the sleep state, the sleep period t is expressed as (3 + 3m) clocks of the system clock. By dividing this by the despreading code length and taking the remainder, the phase of the despreading code at the time of restart can be estimated. Based on the estimation result, synchronization acquisition is realized by the synchronization control unit 28 in a relatively short time.

Next, the case where the operation shifts to the normal operation at the timing when the default sleep period ends will be described. The sleep control unit 110 keeps the sleep state for a predetermined sleep period, for example, 10 clocks with a sleep clock, and instructs the main power supply to start before the sleep period ends. Then, the operation shifts to the normal operation in synchronization with the rise of the sleep clock. At this time, the sleep period t is the number of system clocks (two clocks in this example) measured during a period t1 from the transition to the sleep state to the rise of the first sleep clock, and the number of sleep clocks thereafter (in this example). 10 clocks). When converted to the number of system clocks using the clock ratio m recorded before the transition to the sleep state, the sleep period t is (2 + 10)
m) Expressed as a clock. By dividing this by the despreading code length and taking the remainder, the phase of the despreading code at the time of restart can be estimated. Synchronization acquisition is performed by the synchronization control unit 28 based on the estimation result.

The sleep period measuring unit 106 may be designed to count a sleep clock when transitioning to a sleep state, and to issue a start request signal when a predetermined number (10 clocks in the above example) is reached. Good. In the case of such a configuration, when there is an activation request from a user or the like before the end of the sleep period, the counter value at that time is stored as the sleep period, and 1 is set from the default sleep period (10 in the above example). Load the counter with the reduced value (9 in the example above). As a result, it is possible to minimize the overhead for starting or changing the state of an arbitrary circuit that refers to the count value for shifting to the normal operation state, and reduce unnecessary processing time.

As described above, according to the embodiment, the synchronization acquisition at the time of returning to the normal operation can be facilitated by estimating the length of the sleep period. As a result, it is possible to simplify a configuration required for synchronous acquisition, such as a matched filter and a memory, and to contribute to a reduction in power consumption, a reduction in size and weight of the device, and a reduction in cost. In addition, by performing intermittent reception during standby for incoming calls, power consumption can be reduced, and the continuous standby enabled time can be extended.

The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and that such modifications are also within the scope of the present invention.

In the embodiment, the communication system of the DC-CDMA system has been described. However, the detection technique of the embodiment can be used for other communication systems.

When shifting to the sleep state, the timing of shifting the clock to be measured from the system clock to the sleep clock and the timing of returning from the sleep state to the normal operation state are not limited to the examples described in the embodiment. It is understood by those skilled in the art that various design changes are possible. In short, in order to stop the system clock at the time of sleep, the time management control clock in the meantime should be switched to the sleep clock, and the system can be converted into the system clock later.

[0040]

According to the present invention, an efficient intermittent receiving technique can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a communication terminal according to an embodiment.

FIG. 2 is an internal configuration diagram of a receiving unit.

FIG. 3 is an internal configuration diagram of an intermittent reception control unit.

FIG. 4 is a diagram illustrating a state in which a receiving unit intermittently receives a signal.

FIG. 5 is a diagram for explaining the operation of the intermittent reception control unit.

[Explanation of symbols]

Reference Signs List 10 communication terminal, 20 reception unit, 28 synchronization control unit, 30 transmission unit, 40 control unit, 100 intermittent reception control unit, 102 system clock acquisition unit, 104 sleep clock acquisition unit, 106 sleep period measurement unit, 108 clock ratio measurement unit 110 sleep control unit.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (8)

[Claims] 1. Prior to switching from a normal operation state for receiving a signal to a sleep state, a clock having a first frequency for normal operation and a clock having a second frequency for control during sleep are provided. Storing a frequency ratio; stopping the clock of the first frequency to switch from the normal operation state to the sleep state; and measuring the number of clocks of the clock of the second frequency over a sleep period. And a step of returning to the normal operation state in synchronization with a clock of the second frequency when a start request is detected during sleep; and a ratio of the frequency and the measured second frequency. Calculating the sleep period from the number of clocks using the clock of the first frequency as a unit. Law. 2. Prior to switching from a normal operation state for receiving a signal to a sleep state, a clock of a first frequency for normal operation and a clock of a second frequency for control during sleep are used. Storing a frequency ratio; stopping the clock of the first frequency to switch from the normal operation state to the sleep state; and measuring the number of clocks of the clock of the second frequency over a sleep period. When the clock number reaches a predetermined threshold, returning to the normal operation state; and when detecting a start request before the clock number reaches the predetermined threshold, Storing the number of clocks;
Returning to the normal operation state in synchronization with a clock having a frequency of the following frequency; and the ratio of the frequencies and the number of clocks or the threshold value stored in the step of returning to the normal operation state. A step of calculating in units of frequency clocks. 3. The method according to claim 1, further comprising the step of counting the number of clocks by a counter element, wherein when a start request is detected before the clock number reaches the predetermined threshold value, the count value of the counter element is set as the count value. 3. The method of claim 2, wherein a value at or near a predetermined threshold is loaded. Calculating a remainder obtained by dividing the number of clocks of the clock of the first frequency calculated in the calculating step by a code length of a spreading code for despreading the signal; The method according to claim 1, further comprising: estimating a timing of multiplying the signal by the spreading code based on the remainder. 5. A first clock acquisition unit for acquiring a clock signal of a first frequency for normal operation, and a second clock acquisition unit for acquiring a clock signal of a second frequency for control during sleep. A sleep control unit that detects a sleep request and a wake-up request and controls switching between a normal operation state and a sleep state; and the first frequency when the sleep control unit detects the sleep request. A clock ratio measurement unit that stores a ratio of the clock of the second frequency to the clock of the second frequency over the period of the sleep state. A sleep period measuring unit that calculates a state period in units of a clock of the first frequency. 6. A transmitting unit for modulating and transmitting a signal, a receiving unit for receiving and demodulating a signal, a control unit for controlling the transmitting unit and the receiving unit, and a first clock having a relatively high speed. Controls switching between a normal operating state, in which signal reception and processing is performed using a second clock, and a sleep state in which signal reception is interrupted while maintaining a minimum system state using a relatively slow second clock. An intermittent reception control unit, wherein the reception unit has a synchronization control unit for synchronizing the signal and a spreading code for despreading the signal, and the intermittent reception control unit sleeps from a normal operation state. A clock ratio measurement unit that measures a frequency ratio between the first clock and the second clock when transitioning to a state, and the first clock in a sleep state. And a sleep control unit for stopping the sleep period. The sleep period is measured by the second clock, and when returning from the sleep state to the normal operation state, the sleep period is set to the number of clocks of the first clock based on the frequency ratio. A mobile communication terminal, comprising: a sleep period measuring unit for converting; and the synchronization control unit recovers a synchronization state of the system using the number of clocks of the first clock. 7. A transmitting unit for modulating and transmitting a signal, a receiving unit for receiving and demodulating a signal, a control unit for controlling the transmitting unit and the receiving unit, and a normal operation state for receiving the signal. An intermittent reception control unit that controls switching to a sleep state, the reception unit includes a synchronization control unit that synchronizes the signal with a spreading code for despreading the signal, The control unit includes a first clock acquisition unit that acquires a clock signal of a first frequency for normal operation, and a second clock acquisition unit that acquires a clock signal of a second frequency for control during sleep. A sleep control unit that detects a sleep request and an activation request and controls switching between the normal operation state and the sleep state; and the sleep control. When the unit detects the sleep request, a clock ratio measurement unit that stores a ratio between the first frequency and the second frequency, and counts the number of clocks of the second frequency over a period of the sleep state. A sleep period measuring unit that converts the period of the sleep state to the number of clocks of the first frequency based on the number of clocks and the ratio, wherein the synchronization control unit performs the normal operation from the sleep state. When returning to a state, the mobile communication terminal estimates the timing of multiplying the signal by the spreading code based on the converted clock number of the first frequency. 8. A normal operating state in which signals are received and processed using a relatively high-speed first clock, and a minimum system state is maintained using a relatively low-speed second clock. In the intermittent reception method in which a signal is interrupted and a sleep state is interrupted, a frequency ratio between the first clock and the second clock is measured at the time of transition from a normal operation state to a sleep state. The clock is stopped and the sleep period is measured by the second clock. Upon returning from the sleep state to the normal operation state, the sleep period is converted into the number of clocks of the first clock based on the frequency ratio, and Restoring the synchronization state of the system by the first clock.