JP2009004918A - Portable communication terminal, and temperature compensation method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a portable communication terminal which can control frequency deviation of a crystal vibrator when its temperature rises by aggravation of radio wave reception state. <P>SOLUTION: The portable communication terminal includes wireless communication circuits 2 and 3 performing cellular communication with a wireless base station, a crystal oscillation circuit 9 for supplying a local signal to the wireless communication circuits 2 and 3, a temperature sensor 6 for detecting the temperature, and a temperature compensation circuit 7 for regulating the frequency of the local signal by controlling the crystal oscillation circuit 9 based on the output from the temperature sensor 6. The temperature compensation circuit 7 controls the crystal oscillation circuit 9 such that the frequency deviation of the local signal has the characteristics of negative inclination for the steady temperature. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a portable communication terminal and a temperature compensation method thereof, and more particularly to an improvement of a portable communication terminal having a temperature compensated crystal oscillation circuit, for example, a cellular phone. More particularly, the present invention relates to a temperature compensation method for a crystal oscillation circuit that supplies a local signal to a radio communication circuit that performs cellular communication with a radio base station.

  In general, a mobile communication terminal such as a mobile phone or a PHS (Personal Handyphone System) includes a radio communication circuit that performs cellular communication with a radio base station, and a local oscillation circuit for supplying a local signal to the radio communication circuit. Built-in. The radio communication circuit requires a high-frequency signal to perform frequency up-conversion and down-conversion. Such a high-frequency signal is called a local signal, and a circuit that generates the local signal is a local oscillation circuit.

  In the wireless communication circuit, an RF transmission signal is generated by mixing and filtering a local signal with respect to a transmission signal having an intermediate frequency. On the other hand, an intermediate frequency received signal can be obtained by mixing a local signal with an RF received signal. Since the carrier frequency of the RF signal that can be transmitted and received by such a wireless communication circuit is determined by the frequency of the local signal, high accuracy is required for the frequency of the local signal in the local oscillation circuit. For this reason, a crystal oscillation circuit that generates a high-frequency signal as a local signal using the oscillation action of a crystal resonator is usually used for the local oscillation circuit of the mobile communication terminal. Since a crystal resonator has a property that its oscillation frequency changes according to temperature, in a portable communication terminal as described above, a temperature-compensated crystal oscillation circuit that can suppress fluctuations in oscillation frequency due to temperature ( TCXO) has been used conventionally.

  A TCXO (Temperature Compensated Xtal Oscillator) includes a crystal oscillation circuit, a temperature sensor, and a temperature compensation circuit that controls the crystal oscillation circuit based on the output of the temperature sensor and adjusts the frequency of the high-frequency signal. In this temperature compensation circuit, the crystal oscillation circuit is controlled so that the frequency deviation at each temperature is small. By generating a local signal using such a TCXO, even when the temperature of the crystal resonator changes, the fluctuation of the oscillation frequency can be reduced.

  However, since the above-described conventional TCXO only considers temperature compensation with respect to a steady temperature, if the temperature of the crystal resonator changes suddenly due to a temperature change around the crystal resonator, the frequency deviation is sufficiently compensated. There is a problem that the frequency deviation increases. Usually, in a wireless communication circuit that performs cellular communication with a wireless base station, control is performed to adjust the transmission output according to the reception state of radio waves. That is, when the radio wave reception state deteriorates, control is performed to increase the amplification factor of the RF transmission signal. For this reason, when the reception state of radio waves deteriorates, power consumption in the circuit increases, and a circuit such as a wireless communication circuit generates heat and the temperature of the crystal unit rises rapidly. In the conventional portable communication terminal having the above-described TCXO, when the temperature of the crystal resonator rises due to the deterioration of the reception state, the frequency deviation increases, so that the reception state of the radio wave is further deteriorated. In other words, in the conventional portable communication terminal, once the temperature of the crystal unit rises, the temperature of the radio communication circuit further increases due to the deterioration of the reception state due to the increase in frequency deviation, so the temperature of the crystal unit rises rapidly. There was a problem of doing. On the other hand, when the communication is completed or the reception state is improved, the temperature of the wireless communication circuit is lowered and the temperature of the crystal unit is also lowered. In this case, the reception state deteriorates due to an increase in the frequency deviation due to the temperature drop of the crystal resonator, but this is not a problem because the communication is completed or the reception state is originally good.

In addition, about the temperature characteristic regarding the frequency deviation of a crystal oscillator, it describes in FIG. 6 of patent document 1, FIG. 2 of patent document 2, and patent documents 4-8, for example. Moreover, the portable communication terminal having TCXO is described in Patent Documents 3 and 4, for example. Further, for example, Patent Document 1 describes that the reception state deteriorates when the frequency deviation of the local signal increases.
JP 2000-244355 A JP 2004-23634 A JP 2005-26981 A JP 2006-222725 A JP 2002-26658 A JP 2004-128939 A JP 2004-272882 A JP-A-2005-130372

  As described above, in the conventional mobile communication terminal, when the temperature of the crystal resonator changes suddenly due to the temperature change around the crystal resonator, the frequency deviation cannot be sufficiently compensated and the frequency deviation increases. There was a problem that. In particular, once the temperature of the crystal unit rises, the temperature of the radio communication circuit further increases due to the deterioration of the reception state due to the increase of the frequency deviation, so that the temperature of the crystal unit increases rapidly. It was.

  The present invention has been made in view of the above circumstances, and a portable device that can sufficiently compensate for the frequency deviation of a local signal when the temperature of the crystal resonator changes rapidly due to a temperature change around the crystal resonator. An object is to provide a communication terminal and a temperature compensation method thereof. In particular, it is an object of the present invention to provide a mobile communication terminal that can suppress a rapid rise in the temperature of a crystal resonator when the temperature of the crystal resonator rises due to a deterioration in a radio wave reception state.

  A mobile communication terminal according to a first aspect of the present invention includes a radio communication circuit that performs cellular communication with a radio base station, a crystal oscillation circuit that supplies a local signal to the radio communication circuit, and a temperature sensor for detecting temperature. And a temperature compensation circuit that controls the crystal oscillation circuit based on the output of the temperature sensor and adjusts the frequency of the local signal, and the temperature compensation circuit has a frequency deviation of the local signal with respect to a steady temperature. Is configured to control the crystal oscillation circuit so as to have a characteristic having a negative slope.

  According to such a configuration, since the crystal oscillation circuit is controlled so that the frequency deviation of the local signal with respect to the steady temperature has a negative slope, the temperature between the crystal oscillation circuit and the temperature sensor is suddenly increased. When there is a temperature difference in the frequency difference, the frequency deviation can be sufficiently compensated. Therefore, when the temperature of the crystal unit rises due to the deterioration of the radio wave reception state, an increase in the frequency deviation is suppressed, so that the temperature of the crystal unit can be prevented from rising rapidly.

  A mobile communication terminal according to a second aspect of the present invention includes, in addition to the above configuration, a temperature compensation table that associates the output of the temperature sensor with the control data of the crystal oscillation circuit, and the temperature compensation circuit is used as the output of the temperature sensor. Based on the temperature compensation table, the crystal oscillation circuit is controlled based on the temperature compensation table.

  In addition to the above configuration, the portable communication terminal according to the third aspect of the present invention is characterized in that the temperature compensation circuit is minimum when the frequency deviation characteristic of the local signal with respect to the temperature change rate is +1 degree / second or more and +3 degree / second or less. It is comprised so that the said crystal oscillation circuit may be controlled.

  According to a fourth aspect of the present invention, there is provided a temperature compensation method for a mobile communication terminal comprising: a radio communication circuit that performs cellular communication with a radio base station; and a crystal oscillation circuit that supplies a local signal to the radio communication circuit. A temperature compensation method in a terminal, wherein an oscillation step of generating a local signal using a crystal resonator, a communication step of performing cellular wireless communication with a base station using the local signal, and a temperature sensor A temperature detection step for detecting a temperature; and a temperature compensation step for controlling the crystal oscillation circuit based on the temperature detected in the temperature detection step and adjusting the frequency of the local signal. In the temperature compensation step, The local signal frequency with respect to a steady temperature is configured to have a negative slope.

  According to the portable communication terminal and the temperature compensation method of the present invention, the crystal oscillation circuit is controlled so that the frequency deviation of the local signal with respect to the steady temperature has a negative slope. When a temperature difference occurs between the crystal oscillation circuit and the temperature sensor, the frequency deviation can be sufficiently compensated. Therefore, when the temperature of the crystal unit rises due to the deterioration of the radio wave reception state, an increase in the frequency deviation is suppressed, so that the temperature of the crystal unit can be prevented from rising rapidly.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a configuration example of a mobile communication terminal according to Embodiment 1 of the present invention, and shows a schematic configuration of a mobile phone 1. The cellular phone 1 is a portable communication terminal that performs cellular communication with a radio base station, and includes an antenna 11, a radio unit 12, a call control unit 14, a CPU 15, a key input unit 16, an LCD 17, a receiver 18, and a microphone. 19.

  The wireless unit 12 is a transmission / reception unit that transmits and receives radio signals to and from a wireless base station on the mobile communication network via the antenna 11. At the time of transmission, the transmission data from the call control unit 14 is modulated to generate a transmission signal having an intermediate frequency. The transmission signal is converted into an RF transmission signal and transmitted to the radio base station. At the time of reception, an RF reception signal from the radio base station is converted into an intermediate frequency reception signal, and reception data obtained by demodulating the reception signal is output to the call control unit 14.

  The radio unit 12 generates a high-frequency signal as a local signal to be mixed with an intermediate frequency transmission signal to obtain an RF transmission signal, or to be mixed with an RF reception signal to obtain an intermediate frequency reception signal. A module 13 is provided.

  The call control unit 14 performs control related to a call. For example, when the reception state of radio waves deteriorates, control is performed to increase the signal level of the transmission output or the received signal. As described above, the call control unit 14 controls the radio unit 12 to perform cellular communication with the radio base station.

  The CPU 15 is a control circuit that controls the call control unit 14, the LCD 17, the receiver 18, and the like. The key input unit 16 performs an operation of generating a predetermined key input signal by operating an operation key provided on the housing and outputting it to the CPU 15.

  An LCD (Liquid Crystal Display) 17 is a display device that displays information on a screen, and displays key input information and the like. The receiver 18 is a receiving voice output device for outputting a received voice signal. The microphone 19 is a voice input device for transmission that outputs a voice signal obtained by collecting sound to the CPU 15.

  When the reception state of the audio signal received via the antenna 11 deteriorates, it is difficult to hear the received sound reproduced from the receiver 18. In such a case, the call control unit 14 performs control to increase the signal level of the received signal, that is, increase the amplification factor of the received audio signal and increase the reception sensitivity. At this time, control for increasing the transmission output is performed by increasing the amplification factor of the audio signal obtained by the microphone 19.

  FIG. 2 is a block diagram illustrating a configuration example of a main part of the mobile phone 1 of FIG. 1, and illustrates a configuration within the wireless unit 12. In addition to the local oscillation module 13, the radio unit 12 includes a transmission unit 2, a reception unit 3, a modem unit 4, and a PLL frequency synthesizer 5.

  The transmission unit 2 is a wireless communication circuit including a power amplifier 21, a filter 22, and a mixer 23. The receiving unit 3 is a wireless communication circuit that includes an LNA 31, a mixer 32, and a filter 33. The modem unit 4 includes a modulation circuit 24 and a demodulation circuit 34.

  The PLL frequency synthesizer 5 is a frequency adjustment circuit that generates a local signal having a predetermined frequency based on a high-frequency signal from the local oscillation module 13 and outputs the local signal to the transmission unit 2 and the reception unit 3, and includes a PLL circuit. This PLL (Phase Locked Loop) circuit is a circuit for detecting a phase difference between an input signal and an output signal and holding the frequency of the output signal constant. Here, the case where the PLL frequency synthesizer 5 for adjusting the frequency of the local signal is provided will be described. However, the high-frequency signal generated by the local oscillation module 13 is directly used as the local signal, and the transmitter 2 and the receiver 3 May be supplied.

  Transmission data from the call control unit 14 is modulated by a modulation circuit 24 using a predetermined modulation method, and an intermediate frequency transmission signal is generated. This transmission signal is mixed with the local signal from the PLL frequency synthesizer 5 by the mixer 23 of the transmission unit 2, and the pass band is limited by the filter 22 to generate an RF signal. Then, the power is amplified by the power amplifier 21 and output as an RF transmission signal.

  On the other hand, the RF reception signal from the antenna 11 is amplified by the LNA (low noise amplifier) 31 of the receiving unit 3 and input to the mixer 32. Then, the signal is mixed with the local signal from the PLL frequency synthesizer 5 by the mixer 32, the pass band is limited by the filter 33, and an intermediate frequency reception signal is generated. This received signal is demodulated by the demodulation circuit 34 of the modem unit 4 to generate received data.

  The local oscillation module 13 is a temperature-compensated crystal oscillation circuit that generates a high-frequency signal as a local signal, and includes a temperature sensor 6, a temperature compensation table 7, a temperature compensation circuit 8, and a crystal oscillation circuit 9. The crystal oscillation circuit 9 is an oscillation circuit that generates a high-frequency signal having a predetermined frequency using the oscillation action of a crystal resonator and supplies the signal to the PLL frequency synthesizer 5.

  The temperature sensor 6 is a detection means for detecting the temperature, and includes, for example, a thermosensitive element such as a thermocouple. The temperature compensation circuit 8 is a circuit that controls the crystal oscillation circuit 9 based on the output of the temperature sensor 6 and adjusts the frequency of the high-frequency signal.

  The temperature compensation table 7 is a temperature control information holding unit that holds the output of the temperature sensor 6 in association with the control data of the crystal oscillation circuit 9. For example, the correction amount of the frequency deviation for each temperature is held as the temperature compensation table 7.

  The temperature compensation circuit 8 refers to the temperature compensation table 7 based on the output of the temperature sensor 6 and performs an operation for controlling the crystal oscillation circuit 9 so that the frequency deviation of the high-frequency signal with respect to the steady temperature has a negative slope. The oscillation frequency is adjusted so as to obtain characteristics.

  The steady temperature here is a temperature under a condition in which the temperature change of the crystal resonator is relatively gentle and no temperature difference occurs between the crystal oscillation circuit 9 and the temperature sensor 6. For example, the temperature when the reception state of radio waves is good. By controlling the crystal oscillation circuit 9 so that the frequency deviation of the high-frequency signal with respect to the steady temperature has a negative slope, a temperature difference occurs between the crystal oscillation circuit 9 and the temperature sensor 6 due to a rapid temperature change. In this case, the frequency deviation can be sufficiently compensated. Therefore, when the temperature of the crystal unit rises due to the deterioration of the radio wave reception state, an increase in the frequency deviation is suppressed, so that a rapid temperature increase of the crystal unit can be suppressed.

  The temperature sensor 6, the temperature compensation circuit 8, and the crystal oscillation circuit 9 constituting the local oscillation module 13 are integrally formed as a module on a printed board, for example.

  FIG. 3 is a diagram illustrating a configuration example of the wireless unit 12 in the mobile phone 1 of FIG. 1, showing the arrangement of the transmission unit 2, the reception unit 3, and the local oscillation module 13 formed on the printed circuit board 10. Yes. In this example, the transmitting unit 2 and the receiving unit 3 are arranged at one end of the printed circuit board 10 and the local oscillation module 13 is arranged at the other end.

  In the local oscillation module 13, the temperature compensation circuit 8 and the crystal oscillation circuit 9 are disposed on the reception unit 3 side, and the temperature sensor 6 is disposed on the opposite side to the reception unit 3. Since both the transmission unit 2 and the reception unit 3 have amplifiers (amplifiers), they serve as heat sources during operation. That is, in the wireless unit 12, the temperature sensor 6 is disposed farther than the crystal oscillation circuit 9 with respect to the transmission unit 2 and the reception unit 3 as heat sources.

  In such an arrangement, although heat is transmitted from the transmission unit 2 and the reception unit 3, a time delay occurs between the crystal oscillation circuit 9 and the temperature sensor 6. For this reason, when the power consumption in the circuit increases and the temperatures of the transmission unit 2 and the reception unit 3 rapidly increase, a temperature difference occurs between the crystal oscillation circuit 9 and the temperature sensor 6.

  When the temperature sensor 6 is disposed farther from the heat source than the crystal oscillation circuit 9, the time delay amount Δt with respect to the crystal oscillation circuit 9 when heat is transferred from the heat source to the temperature sensor 6 becomes a positive value. For this reason, it is considered that the detection temperature detected by the temperature sensor 6 when the temperature rises is lower than the temperature of the crystal oscillation circuit 9 if the heat capacities of the temperature sensor 6 and the crystal oscillation circuit 9 are the same. In such a case, the conventional TCXO cannot sufficiently compensate for the frequency deviation of the local signal, resulting in an increase in the frequency deviation. In the present embodiment, by performing temperature compensation based on a temperature compensation table 7 that is set in advance so that the frequency deviation with respect to a steady temperature has a negative slope, the frequency deviation at the time of temperature rise is sufficient. Will be compensated for. Therefore, the temperature compensation based on the temperature compensation table 7 sufficiently compensates for the frequency deviation when the time delay amount Δt becomes a positive value, so that the temperature sensor 6 is more effective than the crystal oscillation circuit 9 with respect to the heat source. It is most effective when placed far away.

  FIG. 4 is a diagram illustrating an example of the operation of the wireless unit 12 in FIG. 2, and shows temperature characteristics at the oscillation frequency of the crystal resonator. In FIG. 4, the temperature characteristic of the oscillation frequency is graphed by a characteristic curve indicating the frequency deviation at each temperature. The oscillation frequency of the crystal resonator is, for example, 19.2 MHz (megahertz).

  This characteristic curve is a downwardly convex curve that has a frequency deviation f (T) of 0 ppm (part per million) when the temperature T is about 25 ° C. (Celsius degree), and becomes a minimum near 50 ° C.

  Specifically, the frequency deviation when the temperature T is 20 ° C. is about 1 ppm, and it decreases monotonically from 20 ° C. to about 51 ° C. to a minimum value of about −3.5 ppm. Moreover, when temperature T exceeds 51 degreeC, it increases monotonously and is about -0.2 ppm at 70 degreeC.

  Thus, the crystal resonator has a property that its oscillation frequency changes according to temperature. The temperature compensation circuit 8 performs an operation of correcting the frequency deviation of such a crystal resonator and suppressing the frequency deviation for each temperature.

  FIG. 5 is a diagram illustrating an example of the operation in the wireless unit 12 of FIG. 2, and shows a correction curve 41 indicating the correction amount of the frequency deviation for each temperature by the temperature compensation table 7. The correction curve 41 is a graph of the temperature compensation table 7 and is a convex curve with the correction amount C (T) maximizing when the temperature T is around 50 ° C.

  Specifically, the correction amount when the temperature T is 20 ° C. is about −0.5 ppm, and increases monotonically from 20 ° C. to about 50 ° C., and reaches a maximum value of about 3.5 ppm. Further, when the temperature T exceeds 50 ° C., it decreases monotonously and reaches about 0.1 ppm at 70 ° C.

  In the temperature compensation circuit 8, an operation of adjusting the oscillation frequency of the crystal oscillation circuit 9 is performed based on the temperature compensation table 7 represented by such a correction curve.

  Here, when the temperature of the crystal resonator suddenly increases due to the temperature change around the crystal resonator, a temperature difference is generated between the crystal oscillation circuit 9 and the temperature sensor 6. That is, a deviation ΔT occurs between the temperature detected by the temperature sensor 6 and the actual temperature of the crystal resonator. For example, there may be a case where the temperature of the crystal resonator is higher by ΔT than the temperature detected by the temperature sensor 6. In such a case, the correction curve 42 for the temperature of the crystal oscillation circuit 9 is obtained by moving the correction curve 41 to the high temperature side by ΔT.

  Therefore, the correction amount C (T) of the frequency deviation with respect to the detected temperature T is determined as (−1) times the frequency deviation f (T + ΔT) at T + ΔT.

  FIG. 6 is a diagram illustrating an example of the operation in the wireless unit 12 of FIG. 2, and shows a characteristic curve indicating the frequency deviation after correction based on the temperature compensation table 7. This characteristic curve is a convex curve which monotonously decreases in a temperature range exceeding 20 ° C., and the frequency deviation a (T) after correction is about 0.5 ppm when the temperature T is 20 ° C.

  That is, in this characteristic curve, the frequency deviation with respect to the steady temperature has a negative slope. Specifically, the frequency deviation is a1 (ppm) when the temperature is T1, and a2 (ppm) (a2 <a1) when T2 (T2> T1). In this example, the frequency deviation is 0 ppm when the temperature T is about 50 ° C., and about −1.1 ppm at 70 ° C.

  In this example, the frequency deviation of the local signal with respect to the steady temperature has a characteristic that always has a negative slope within a temperature range of 20 ° C. to 70 ° C.

  FIG. 7 is a diagram illustrating an example of the operation in the wireless unit 12 in FIG. 2, and illustrates how the local oscillation module 13 changes in temperature. FIG. 7 shows how the surface temperature of the local oscillation module 13 changes with the passage of time t when the air temperature is 25 ° C. For example, the surface temperature is about 27 ° C. when the elapsed time is 0 second (sec), and is about 51 ° C. when the elapsed time is 10 seconds.

  When the ambient temperature suddenly rises due to the deterioration of the reception state or the like, the temperature of the local oscillation module 13 rises in this way. According to the results of experiments by the present inventors, the slope of the temperature change with respect to the surface temperature of the local oscillation module 13, that is, the amount of change in temperature v per unit time is about 2 degrees / second (deg / sec). ing. In this specification, such a temperature change gradient is referred to as a temperature change rate.

  FIG. 8 is a diagram illustrating an example of a temperature change of the wireless unit 12 when the reception state of radio waves deteriorates. FIG. 8 shows a characteristic curve B1 indicating a temperature change of the transmitter 2 and the receiver 3, a characteristic curve B2 indicating a temperature change of the crystal oscillation circuit 9, and a characteristic curve B3 indicating a temperature change of the temperature sensor 6. Has been.

  The characteristic curve B1 has a temperature T10 at an elapsed time of 0 seconds, rapidly increases in temperature until the elapsed time t1, and reaches a saturation temperature (temperature T11) at t1. On the other hand, in the characteristic curves B2 and B3, a time delay occurs in the temperature change within the temperature increase period A1.

  In this example, the temperature change of the temperature sensor 6 is further delayed with respect to the temperature change of the crystal oscillation circuit 9. When the time delay amount in such a temperature change is Δt, the temperature shift ΔT generated between the crystal oscillation circuit 9 and the temperature sensor 6 can be expressed as ΔT = v × Δt.

  Generally, when the reception state of radio waves is poor, control is performed to increase the amplification factor of the received signal or increase the transmission output. For this reason, the current flowing through the circuit increases, and the temperature of the circuit rises. At this time, if the frequency fluctuation due to the temperature change of the crystal resonator is not sufficiently compensated, the reception sensitivity is deteriorated, and the temperature of the circuit further increases.

  As described above, when the temperature of the crystal oscillation circuit 9 rapidly increases due to the temperature change of the transmission / reception circuit, a temperature shift ΔT due to a time delay of the temperature change occurs between the crystal oscillation circuit 9 and the temperature sensor 6. In the present embodiment, when the temperature of the crystal resonator rises rapidly, the frequency fluctuation due to the temperature change is sufficiently compensated, so that it is possible to suppress the deterioration of the reception sensitivity.

  On the other hand, when the call ends or when the reception state of the radio wave is improved, the power consumption is reduced, so that the temperature of the circuit is lowered. In this case, even if the frequency fluctuation due to the temperature change is not sufficiently compensated, the reception level is originally high, so that the influence due to the deterioration of the reception sensitivity is small. For this reason, the characteristic curve B4 when the temperature of the circuit decreases is a curve in which the temperature gradually decreases with time.

  FIGS. 9A and 9B are diagrams showing an example of the operation of the radio unit 12 of FIG. 2 in comparison with the prior art, and shows temperature characteristics at the oscillation frequency after temperature compensation. FIG. 9A shows a frequency deviation characteristic curve A2 in a steady state and a characteristic curve A3 when the temperature rises as temperature characteristics of the radio unit 12 according to the present invention. FIG. 9B shows a characteristic curve A4 of frequency deviation in a steady state and a characteristic curve A5 when the temperature rises as temperature characteristics according to the prior art.

  The characteristic curve A2 is a characteristic curve indicating a frequency deviation after correction in a steady state, that is, when the temperature change is relatively gradual, and has a negative slope. The characteristic curve A3 is a characteristic curve showing the corrected frequency deviation when the ambient temperature rapidly increases due to deterioration of the reception state or the like, and the frequency deviation at each temperature is approximately 0 ppm.

  As described above, in the present embodiment, it is possible to suppress an increase in the frequency deviation when the temperature of the crystal resonator is rapidly increased. In a steady state, a frequency deviation of about −0.8 ppm to +0.5 ppm occurs in a temperature range of 20 ° C. to 70 ° C. This deviation is normally allowed.

  In contrast, the characteristic curve A4 has a frequency deviation of approximately 0 ppm at each temperature, while the characteristic curve A5 has a larger frequency deviation at each temperature than the characteristic curve A3. That is, in the prior art, when the ambient temperature rapidly increases, the frequency deviation becomes large.

  FIG. 10 is a diagram showing an example of the operation of the radio unit 12 of FIG. 2 in comparison with the prior art, and shows the state of the error average of the frequency deviation with respect to the temperature change rate. The graph C1 is a graph showing an average error of frequency deviation for each temperature change speed v as a characteristic of the wireless unit 12 according to the present invention. The graph C2 is a graph showing an average error of frequency deviation for each temperature change speed v as a characteristic according to the prior art.

  The average error of the frequency deviation is obtained by averaging the frequency deviation with respect to the change rate v at each temperature within a predetermined temperature range, for example, a temperature range from 20 ° C. to 70 ° C., for the temperature range.

  In the graph C1, the change rate monotonously decreases in the range from -3 degrees / second to +2 degrees / second, and is minimal (minimum value 0 ppm) at the change speed +2 degrees / second. Further, when the change speed exceeds +2 degrees / second, it increases monotonously. That is, in the present embodiment, the frequency deviation is minimized when the temperature change rate is +2 degrees / second.

  On the other hand, in the prior art, the change speed is minimized at 0 degree / second. In the present embodiment, as shown in the graph C1, the oscillation frequency is adjusted so that the characteristic of the frequency deviation with respect to the temperature change rate v is minimized when it is +1 degree / second or more and +3 degree / second or less.

  With this configuration, even when a temperature difference occurs between the crystal oscillation circuit 9 and the temperature sensor 6 due to a rapid temperature rise, the frequency deviation can be sufficiently compensated, and the radio wave reception state can be compensated. When the temperature of the crystal unit rises due to deterioration, an increase in frequency deviation can be suppressed.

  FIG. 11 is a diagram illustrating an example of the operation in the wireless unit 12 in FIG. 2, in which the amount of deterioration in reception sensitivity with respect to the amount of oscillation frequency variation is illustrated. The graph showing the deterioration amount for each fluctuation amount of the oscillation frequency is a straight line rising to the right. Here, the center frequency of the RF reception signal is 1.5 GHz (gigahertz), and the oscillation frequency of the crystal resonator is 19.2 MHz (megahertz).

  For example, the deterioration amount of the reception sensitivity is 5 dB (decibel) when the fluctuation amount of the oscillation frequency is 0.2 Hz, and 10 dB when 0.4 Hz.

  From this graph, it can be seen that as the amount of fluctuation of the oscillation frequency increases, the amount of deterioration in reception sensitivity also increases. That is, it can be seen that once the fluctuation amount of the oscillation frequency is increased due to the temperature rise due to the deterioration of the reception state, the reception state is further deteriorated due to the deterioration of the reception sensitivity.

  In the present embodiment, since the crystal oscillation circuit 9 is controlled so that the frequency deviation of the local signal with respect to the steady temperature has a negative slope, the crystal oscillation circuit 9 and the temperature sensor 6 are caused by a rapid temperature rise. When a temperature difference occurs between them, the frequency deviation can be sufficiently compensated. Therefore, when the temperature of the crystal unit rises due to the deterioration of the radio wave reception state, an increase in the frequency deviation is suppressed, so that a rapid temperature increase of the crystal unit can be suppressed.

  Here, the procedure for obtaining the correction amount C (T) according to the present invention from the frequency deviation f (T) representing the temperature characteristic at the oscillation frequency of the crystal resonator will be described using mathematical expressions.

First, the frequency deviation f (T) represented by the characteristic curve of FIG. 4 can be expressed by a cubic equation using the constants A, B, C, and D as f (T) = AT ³ + BT ² + CT + D. . Further, the temperature shift ΔT between the crystal oscillation circuit 9 and the temperature sensor 6 that occurs when the temperature rises can be expressed as ΔT = v × Δt using the temperature change rate v and the time delay amount Δt.

  At this time, the frequency deviation a (T) after temperature correction is expressed as a (T) = f (T) + C (T) using the correction amount C (T) represented by the correction curve 41 in FIG. Is done. When the temperature rises, the temperature T shifts by ΔT due to the time delay of the temperature detection correction, so a (T) = f (T) + C (T−ΔT). The correction amount according to the present invention is C (T) determined such that a (T) becomes a (T) = 0.

  Specifically, C (T−ΔT) = − f (T) is obtained from f (T) + C (T−ΔT) = 0, and C (T) = − f (T + ΔT) is obtained from this equation. It is done. Accordingly, the correction amount C (T) according to the present invention is obtained from the frequency deviation f (T), the time delay amount Δt, and the change speed v.

The frequency deviation a (T) after temperature correction can be expressed as the following equation.

Embodiment 2. FIG.
In the first embodiment, the example in which the temperature compensation is performed so that the characteristic curve indicating the frequency deviation after correction is monotonously reduced and becomes a convex curve has been described. On the other hand, in the present embodiment, a case will be described in which temperature compensation is performed so that a characteristic curve indicating a corrected frequency deviation becomes a straight line with a lower right.

  FIG. 12 is a diagram showing an example of the operation of the mobile phone according to the second embodiment of the present invention, and shows a characteristic curve 51 indicating the frequency deviation after correction based on the temperature compensation table. This characteristic curve 51 is obtained by approximating the characteristic curve 52 of FIG. 6 with a straight line, and is a straight line passing through two different points (temperatures T21 and T22) on the characteristic curve 52.

  That is, in the characteristic curve 51, the frequency deviation with respect to the temperature has a constant slope. The characteristic curve 51 is determined using a frequency deviation on the characteristic curve 52 at a temperature within a temperature change range, for example, a temperature T21 = 20 ° C. (minimum temperature) and T22 = 45 ° C. (intermediate temperature).

  FIG. 13 is a diagram showing an example of the operation of the mobile phone of FIG. 12, and shows a characteristic curve of frequency deviation in a steady state and a characteristic curve at the time of temperature rise. The characteristic curve in the steady state is a straight line that monotonously decreases in a temperature range exceeding 20 ° C., with the temperature deviation T being 20 ° C. and the corrected frequency deviation s (T) being about 0.5 ppm. In this example, the frequency deviation is 0 ppm when the temperature T is about 53 ° C., and about −0.2 ppm at 70 ° C.

  On the other hand, the characteristic curve at the time of temperature rise is a downwardly convex curve where the frequency deviation is minimized when the temperature is around 35 ° C. Specifically, the frequency deviation is approximately 0 ppm in the temperature range from 20 ° C. to 50 ° C., and is approximately 0.6 ppm at 70 ° C.

  FIG. 14 is a diagram showing an example of the operation of the mobile phone shown in FIG. 12 in comparison with the prior art, and shows the state of the error average of the frequency deviation with respect to the temperature change rate. Graph D1 is a graph showing an average error of frequency deviation for each temperature change rate v as a characteristic of the mobile phone according to the present invention. The graph C2 is a graph showing an average error of frequency deviation for each temperature change speed v as a characteristic according to the prior art.

  In the graph D1, the change rate monotonously decreases in the range from -3 degrees / second to +1 degree / second, and is minimal (minimum value 0.1 ppm) at the change speed +1 degree / second. Further, when the change speed exceeds +1 degree / second, it increases monotonously. In the present embodiment, as shown in the graph D1, the oscillation frequency is adjusted so that the frequency deviation characteristic with respect to the temperature change rate v becomes minimum when the frequency deviation is +1 degree / second or more and +3 degree / second or less.

  Here, the procedure for obtaining the frequency deviation s (T) after temperature correction according to the present invention from the frequency deviation a (T) after temperature correction will be described using mathematical expressions.

First, using constants p and q, s (T) = pT + q and a linear expression, p and q are determined because this straight line passes through two points a (T21) and a (T22). That is, p and q are expressed as follows.

Therefore, the frequency deviation s (T) after temperature correction can be expressed as the following equation.

  In the present embodiment, the crystal oscillation circuit 9 is controlled so that the characteristic curve indicating the frequency deviation of the local signal with respect to the steady temperature becomes a straight line having a constant negative slope. When a temperature difference occurs between the circuit 9 and the temperature sensor 6, the frequency deviation can be sufficiently compensated.

  In the first and second embodiments, the crystal oscillation circuit 9 is designed so that the frequency deviation with respect to the steady temperature always has a negative slope within a predetermined temperature range (temperature range from 20 ° C. to 70 ° C.). Although the example in the case of controlling is described, the present invention is not limited to this. For example, if the frequency deviation is smaller on the higher temperature side than room temperature compared to the frequency deviation at room temperature (25 ° C.), the temperature range in which the section where the frequency deviation with respect to the steady temperature has a slope of 0 or more includes the room temperature. It may exist in the inside. Alternatively, if the frequency deviation at the upper limit is smaller than the frequency deviation at the lower limit of the temperature range in which the mobile phone 1 operates normally, the section where the frequency deviation with respect to the steady temperature has a slope of 0 or more is normal temperature. It may exist within the temperature range including.

  In the first and second embodiments, the example in which the crystal oscillation circuit 9 is controlled so that the frequency deviation with respect to the steady temperature has a negative slope has been described. Generally, in a mobile phone, once the time delay amount Δt with respect to the crystal oscillation circuit 9 when heat is transferred from the heat source to the temperature sensor 6 becomes a positive value, the frequency deviation is not sufficiently compensated and the reception state is deteriorated. However, there is a property that the delay amount Δt further increases due to a temperature rise by automatic adjustment of the transmission output. The present invention controls the crystal oscillation circuit 9 so that the frequency deviation with respect to the steady temperature has a negative slope regardless of whether or not the time delay amount Δt is positive. Since the increase in the frequency deviation when the delay amount Δt becomes a positive value is suppressed, it is suitable for the mobile phone as described above. However, it is conceivable that the temperature sensor 6 is disposed closer to the heat source than the crystal oscillation circuit 9 and the time delay amount Δt is clearly a negative value. Below, such a case is demonstrated.

  FIG. 15 is a diagram showing another configuration example of the wireless unit 12 in the mobile phone 1 of FIG. 1, and shows a case where the temperature sensor 6 is arranged closer to the heat source than the crystal oscillation circuit 9. . In such an arrangement, since the temperature sensor 6 is closer to the heat source than the crystal oscillation circuit 9, the time delay amount Δt with respect to the crystal oscillation circuit 9 when heat is transferred from the heat source to the temperature sensor 6 becomes a negative value. Therefore, it is considered that the detected temperature detected by the temperature sensor 6 when the temperature rises is higher than the temperature of the crystal oscillation circuit 9 if the heat capacities of the temperature sensor 6 and the crystal oscillation circuit 9 are the same.

  In this case, since the temperature deviation ΔT between the crystal oscillation circuit 9 and the temperature sensor 6 is also a negative value, the frequency deviation a (T) after the temperature correction represents a downwardly convex quadratic curve. Accordingly, assuming that the time delay amount Δt between the temperature sensor 6 and the crystal oscillation circuit 9 is a negative value, the frequency deviation with respect to the steady temperature is determined to have a characteristic having a positive slope. . Even in such a case, if Δt is a negative value, the correction amount C (T) can be obtained from the frequency deviation f (T).

  FIG. 16 is a diagram illustrating an example of the operation of the wireless unit 12 in FIG. 15, and illustrates temperature characteristics at the oscillation frequency after temperature compensation. In FIG. 16, as the temperature characteristics of the wireless unit 12, a frequency deviation characteristic curve A12 in a steady state and a characteristic curve A13 when the temperature rises are shown. The characteristic curve A12 is a characteristic curve indicating a frequency deviation after correction in a steady state, and has a positive slope. A characteristic curve A13 is a characteristic curve showing a frequency deviation after correction when the ambient temperature rapidly increases due to deterioration of the reception state or the like, and the frequency deviation at each temperature is approximately 0 ppm.

  In the temperature compensation circuit 8, assuming that the time delay amount Δt between the temperature sensor 6 and the crystal oscillation circuit 9 is a negative value, the frequency deviation of the local signal with respect to the steady temperature has a positive slope. The operation of controlling the crystal oscillation circuit 9 is performed so that By performing temperature compensation for the steady temperature as shown by the characteristic curve A12, abruptly the temperature compensation is performed so that the frequency deviation with respect to the steady temperature has a negative slope. The frequency deviation can be sufficiently compensated when the temperature rises, and the increase in the frequency deviation can be suppressed. Therefore, in the case where the temperature sensor 6 is disposed closer to the heat source than the crystal oscillation circuit 9 and the time delay amount Δt is a negative value, the frequency with respect to the steady temperature Temperature compensation may be performed so that the deviation has a characteristic having a positive slope.

1 is a block diagram showing a configuration example of a mobile communication terminal according to Embodiment 1 of the present invention, in which a schematic configuration of a mobile phone 1 is shown. FIG. 2 is a block diagram illustrating a configuration example of a main part of the mobile phone 1 of FIG. 1, in which a configuration within a wireless unit 12 is illustrated. It is the figure which showed the structural example of the radio | wireless part 12 in the mobile telephone 1 of FIG. 1, and the arrangement | positioning of the transmission part 2, the receiving part 3, and the local oscillation module 13 is shown. FIG. 3 is a diagram illustrating an example of an operation in the wireless unit 12 in FIG. 2, and illustrates temperature characteristics at an oscillation frequency of a crystal resonator. FIG. 3 is a diagram illustrating an example of an operation in the wireless unit 12 of FIG. 2, and a correction curve 41 indicating a correction amount of a frequency deviation for each temperature by the temperature compensation table 7 is illustrated. FIG. 3 is a diagram illustrating an example of an operation in the wireless unit 12 of FIG. 2, and shows a characteristic curve indicating a frequency deviation after correction based on the temperature compensation table 7. FIG. 3 is a diagram illustrating an example of an operation in the wireless unit 12 in FIG. 2, in which a temperature change state of the local oscillation module 13 is illustrated. It is the figure which showed an example of the temperature change of the radio | wireless part 12 when the reception state of an electromagnetic wave deteriorated. It is the figure which showed an example of the operation | movement in the radio | wireless part 12 of FIG. 2 compared with the prior art, and the temperature characteristic in the oscillation frequency after temperature compensation is shown. It is the figure which showed an example of the operation | movement in the radio | wireless part 12 of FIG. 2 compared with the prior art, and the mode of the error average of the frequency deviation with respect to the change rate of temperature is shown. FIG. 3 is a diagram illustrating an example of an operation in the wireless unit 12 in FIG. 2, in which a deterioration amount of reception sensitivity with respect to an oscillation frequency variation amount is illustrated. It is the figure which showed an example of operation | movement of the mobile telephone by Embodiment 2 of this invention, and the characteristic curve 51 which shows the frequency deviation after correction | amendment based on a temperature compensation table is shown. It is the figure which showed an example of the operation | movement in the mobile telephone of FIG. 12, and the characteristic curve of the frequency deviation in a steady state and the characteristic curve at the time of a temperature rise are shown. It is the figure which showed an example of the operation | movement in the mobile telephone of FIG. 12 compared with the prior art, and the mode of the error average of the frequency deviation with respect to the change rate of temperature is shown. FIG. 7 is a diagram showing another configuration example of the wireless unit 12 in the mobile phone 1 of FIG. 1, and shows a case where the temperature sensor 6 is arranged closer to the heat source than the crystal oscillation circuit 9. FIG. 16 is a diagram illustrating an example of an operation in the wireless unit 12 in FIG. 15, and illustrates temperature characteristics at an oscillation frequency after temperature compensation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cellular phone 2 Transmission part 3 Reception part 4 Modem part 5 PLL frequency synthesizer 6 Temperature sensor 7 Temperature compensation table 8 Temperature compensation circuit 9 Crystal oscillation circuit 10 Printed circuit board 11 Antenna 12 Radio | wireless part 13 Local oscillation module 14 Call control part 15 CPU
16 Key input unit 17 LCD
18 Receiver 19 Microphone 21 Power amplifier 22, 33 Filter 23, 32 Mixer 24 Modulation circuit 34 Demodulation circuit

Claims (4)

A wireless communication circuit for performing cellular communication with a wireless base station;
A crystal oscillation circuit for supplying a local signal to the wireless communication circuit;
A temperature sensor for detecting the temperature;
A temperature compensation circuit that controls the crystal oscillation circuit based on the output of the temperature sensor and adjusts the frequency of the local signal;
The portable communication terminal, wherein the temperature compensation circuit controls the crystal oscillation circuit so that a frequency deviation of the local signal with respect to a steady temperature has a negative slope. A temperature compensation table associating the output of the temperature sensor with the control data of the crystal oscillation circuit;
The portable communication terminal according to claim 1, wherein the temperature compensation circuit controls the crystal oscillation circuit with reference to the temperature compensation table based on an output of the temperature sensor.   The temperature compensation circuit controls the crystal oscillation circuit so that a frequency deviation characteristic of the local signal with respect to a change rate of temperature is minimized when the frequency deviation is +1 degree / second or more and +3 degree / second or less. Item 3. The mobile communication terminal according to Item 1 or 2. A temperature compensation method in a portable communication terminal including a wireless communication circuit that performs cellular communication with a wireless base station, and a crystal oscillation circuit that supplies a local signal to the wireless communication circuit,
An oscillation step for generating a local signal using a crystal unit;
A communication step of performing cellular radio communication with a base station using the local signal;
A temperature detecting step for detecting temperature using a temperature sensor;
A temperature compensation step of controlling the crystal oscillation circuit based on the temperature detected in the temperature detection step and adjusting the frequency of the local signal;
A temperature compensation method for a mobile communication terminal, wherein, in the temperature compensation step, the frequency of the local signal with respect to a steady temperature has a characteristic having a negative slope.

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