Oscillator

Abstract

To provide an oscillator that detects the ambient temperature before the temperature of a crystal oscillator changes, prevents a delay in the correction of the frequency-temperature characteristics, and reduces the hysteresis of the frequency-temperature characteristics.SOLUTION: The oscillator is a surface-mount type, and is provided with a sensor for detecting ambient temperature 15 to detect temperature for correcting frequency-temperature characteristics on a substrate 1 that has a plurality of circuits mounted on it. The ambient temperature sensor 15 is located closer to a metal cover 2 than a reference crystal oscillator 11 with a quartz crystal plate and other circuits and detects the temperature via a copper foil 16 for heat conduction soldered to the metal cover 2 and soldered to a soldering part 17. The detected temperature is used to correct the frequency-temperature characteristics.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an oscillator, and more particularly to an oscillator capable of detecting the ambient temperature before the temperature of a quartz crystal plate changes, thereby preventing a delay in correction of frequency temperature characteristics. [Background technology]

[0002] [Prior Art] In conventional oscillators, a thermistor is placed near a reference crystal oscillator having a crystal diaphragm to detect the temperature of the reference crystal oscillator, and an arithmetic circuit (CPU: Central Processing Unit) is used to calculate the amount of frequency correction corresponding to the detected temperature, and the frequency-temperature characteristics are corrected using the frequency correction amount.

[0003] [Conventional oscillator: Figure 5] Next, the configuration of a conventional oscillator will be described with reference to Fig. 5. Fig. 5 is an explanatory diagram of a side and a plan of a conventional oscillator, where (a) is an explanatory side view and (b) is an explanatory plan view. As shown in FIG. 5, the conventional oscillator is a surface-mount type, in which a metal cover 2 is fixed to a substrate 1 by a soldering portion 17.

[0004] The plane of the substrate 1 of the conventional oscillator is equipped with a thermistor 10, a reference crystal oscillator 11, a frequency-voltage controlled oscillator 12, a CPU (Central Processing Unit) 13, an FPGA (Field Programmable Gate Array) 14, and soldering portions 17 formed at the four corners of the plane of the substrate 1. The thermistor 10 is disposed near the reference crystal oscillator 11 to sense the temperature of the reference crystal oscillator 11 .

[0005] [Circuit configuration of a conventional oscillator: Figure 6] Next, the circuit configuration of a conventional oscillator will be described with reference to Fig. 6. Fig. 6 is a schematic diagram of the circuit configuration of a conventional oscillator. As shown in FIG. 6, the circuit configuration of a conventional oscillator is such that an oscillation frequency signal oscillated by a reference crystal oscillator 11 is input to an FPGA 14, which outputs a control voltage to a frequency-voltage controlled oscillator 12, which then outputs a specific frequency.

[0006] In addition, the thermistor 10 detects the temperature around the reference crystal oscillator 11, and the CPU 13 calculates a frequency correction value based on the detected temperature value and outputs it to the FPGA 14. The FPGA 14 corrects the oscillation frequency from the reference crystal oscillator 11 with the frequency correction value input from the CPU 13 .

[0007] The thermistor 10 outputs a voltage corresponding to the detected temperature. When the voltage is input to the CPU 13, it is converted from analog to digital (A / D conversion) and input to the frequency correction value calculation unit 13a, which then calculates a frequency correction value. The FPGA 14 also includes a DDS (Digital Direct Synthesizer) 14a and a PLL (Phase Locked Loop) 14b.

[0008] [Thermal circuit model of a conventional oscillator: Figure 7] Next, a thermal circuit model of a conventional oscillator will be described with reference to Fig. 7. Fig. 7 is a schematic diagram of a thermal circuit model of a conventional oscillator. Fig. 7 is a schematic representation of the temperature change in the conventional oscillator using thermal resistance and heat capacity. The thermal circuit model of a conventional oscillator is configured with a reference crystal oscillator 11 and a thermistor 10 connected in parallel to the positive side of a power supply voltage V2, as shown in Figure 7. Here, the power supply voltage is a voltage equivalent to the ambient temperature. Each part is represented by a thermal resistance (R) and a thermal capacity (C).

[0009] In FIG. 7, “Ta” indicates the ambient temperature, “T_Xtal” indicates the temperature of the crystal oscillating plate (reference crystal oscillator 11), and “T_Thermistor” indicates the temperature detected by the thermistor 10.

[0010] [Temperature tracking characteristics of conventional oscillators: Figure 8] Next, the temperature tracking characteristics of a conventional oscillator will be described with reference to Fig. 8. Fig. 8 is a graph of the temperature tracking characteristics of a conventional oscillator. In Fig. 8, the ambient temperature is increased and kept constant until 360 minutes, and then decreased from 400 minutes. As shown in FIG. 8, the temperature tracking characteristics of a conventional oscillator are such that the temperature (T_Xtal) of the quartz plate (reference quartz oscillator 11) rises and falls with a delay in response to rises and falls in the ambient temperature (Ta), but the rise and fall of the temperature (T_Thermistor) of the thermistor 10 follows with an even greater delay than the quartz plate temperature (T_Xtal).

[0011] Then, the frequency correction value calculation unit 13a calculates a frequency correction value using the temperature (T_Thermistor) of the thermistor 10 and provides it to the DDS 14a in the FPGA 14, so that the frequency temperature characteristics of the reference crystal oscillator 11 are corrected by the DDS 14a.

[0012] [Related Technology] As a related prior art, there is a "Temperature Compensated Crystal Oscillator" (Patent Document 1) disclosed in Japanese Patent Laid-Open Publication No. 01-208904. Patent Document 1 discloses a configuration for a temperature compensated crystal oscillator in which the response time of a temperature detector that detects the ambient temperature to a temperature change is made equal to the response time of a crystal oscillation element to a temperature change. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Japanese Patent Application Publication No. 01-208904 Summary of the Invention [Problem to be solved by the invention]

[0014] However, conventional oscillators were unable to quickly follow the temperature changes of the quartz crystal plate inside the container, and instead detected the temperature with a delay and corrected the frequency-temperature characteristics. This resulted in a delay in the correction of the frequency-temperature characteristics, which caused hysteresis in the frequency-temperature characteristics.

[0015] Although the technology disclosed in Patent Document 1 improves the response characteristics of the temperature detector to temperature changes, a delay in frequency correction occurs because the temperature detector is configured to follow the detected temperature. Therefore, Patent Document 1 does not disclose a configuration capable of preventing a delay in correction of the frequency temperature characteristic and reducing the hysteresis of the frequency temperature characteristic.

[0016] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide an oscillator that can detect the ambient temperature before the temperature of the quartz crystal plate changes, thereby preventing a delay in correcting the frequency-temperature characteristics and reducing hysteresis in the frequency-temperature characteristics. [Means for solving the problem]

[0017] The present invention, which aims to solve the problems of the above-mentioned conventional examples, is a surface-mount type oscillator having a metal cover, in which a temperature sensor that detects temperature in order to correct the frequency-temperature characteristics of a quartz crystal plate is provided on a substrate carrying a plurality of circuits, and the temperature sensor is positioned so that the distance to the metal cover is shorter than the distance to the plurality of circuits, and the temperature is detected via heat-conducting copper foil soldered to the metal cover.

[0018] The present invention is characterized in that in the oscillator, the heat-conducting copper foil is soldered to the metal cover at the four corners of the substrate, and the temperature sensor is provided near the corners.

[0019] The present invention is characterized in that, in the above-mentioned oscillator, it has a transient thermal response calculation unit that calculates or estimates the amount of temperature fluctuation in the quartz crystal vibration plate taking into account the structural transient thermal response from the temperature detected by the temperature sensor, and a frequency correction value calculation unit that calculates a correction value for the frequency-temperature characteristics based on the calculated temperature fluctuation.

[0020] The present invention is characterized in that, in the above oscillator, the transient thermal response calculation unit is provided with a CR filter type transient thermal model having parameters of thermal resistance value and heat capacity value of the transient thermal response obtained by simulation, and calculates the amount of temperature fluctuation in the quartz vibration plate using the transient thermal model. Effect of the Invention

[0021] According to the present invention, a surface-mount type oscillator having a metal cover is provided on a substrate carrying a plurality of circuits, and a temperature sensor for detecting temperature in order to correct the frequency-temperature characteristics of a quartz crystal plate is provided. The temperature sensor is positioned at a position where the distance to the metal cover is shorter than the distance to the plurality of circuit components, and the oscillator detects temperature via heat-conducting copper foil soldered to the metal cover. This has the effect of detecting the ambient temperature before the quartz crystal plate, preventing delays in correction of the frequency-temperature characteristics, and reducing hysteresis in the frequency-temperature characteristics. [Brief description of the drawings]

[0022] [Figure 1] 1A and 1B are explanatory diagrams of the side and top of the oscillator. [Diagram 2] FIG. 2 is a schematic diagram of the circuit configuration of the oscillator. [Diagram 3] FIG. 2 is a schematic diagram of a thermal circuit model of the oscillator. [Figure 4] FIG. 4 is a graph showing the temperature tracking characteristics of the oscillator. [Diagram 5] 1A and 1B are explanatory diagrams of a side and a plan view of a conventional oscillator. [Figure 6] FIG. 1 is a schematic diagram of a circuit configuration of a conventional oscillator. [Figure 7] FIG. 1 is a schematic diagram of a thermal circuit model of a conventional oscillator. [Figure 8] FIG. 13 is a graph showing temperature tracking characteristics of a conventional oscillator. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. [Outline of the embodiment] The oscillator (the present oscillator) according to an embodiment of the present invention is a surface-mount type crystal oscillator having a metal cover, in which a temperature sensor for detecting temperature in order to correct the frequency-temperature characteristics is provided on a substrate carrying a plurality of circuits, and the temperature sensor is positioned in a position where the distance to the metal cover is shorter than the distance to a reference crystal oscillator having a crystal diaphragm and other circuits, and the temperature is detected through heat-conducting copper foil soldered to the metal cover, and the detected temperature is used to correct the frequency-temperature characteristics, so that the ambient temperature is detected before the temperature of the crystal diaphragm changes, preventing delays in the correction of the frequency-temperature characteristics and reducing hysteresis in the frequency-temperature characteristics.

[0024] [This oscillator: Figure 1] The configuration of this oscillator will be described with reference to Fig. 1. Fig. 1 is an explanatory diagram of the side and top of this oscillator, where (a) is an explanatory side view and (b) is an explanatory top view. As shown in FIG. 1, this oscillator is a surface-mount type, and a metal cover 2 is fixed to a substrate 1 by a soldering portion 17.

[0025] The plane of the substrate 1 of this oscillator is equipped with a reference crystal oscillator 11, a frequency-voltage controlled oscillator 12, a CPU (Central Processing Unit) 13, an FPGA (Field Programmable Gate Array) 14, an ambient temperature detection sensor 15, soldering portions 17 formed at the four corners of the plane of the substrate 1, and a heat-conducting copper foil 16 connecting the ambient temperature detection sensor 15 and the soldering portions 17. Each part of this oscillator will be described later.

[0026] In addition, as shown in FIG. 1(2), in order to detect the temperature of the metal cover 2, the ambient temperature detection sensor 15 is provided closer to the metal cover 2 than the other circuits and closer to a soldering portion 17 at one of the four corners of the board 1, and is connected to the soldering portion 17 via a heat-conducting copper foil 16. In other words, the ambient temperature detection sensor 15 is positioned so that the distance to the metal cover 2 is shorter than the distance to other circuits, and detects the temperature of the metal cover 2 via the heat conductive copper foil 16 and the soldering portion 17.

[0027] [Circuit configuration of this oscillator: Figure 2] Next, the circuit configuration of this oscillator will be described with reference to Fig. 2. Fig. 2 is a schematic diagram of the circuit configuration of this oscillator. As shown in FIG. 2, the circuit configuration of this oscillator is such that an oscillation frequency signal oscillated by a reference crystal oscillator 11 is input to an FPGA 14, which outputs a control voltage to a frequency-voltage controlled oscillator 12, causing the frequency-voltage controlled oscillator 12 to output a specific frequency.

[0028] Furthermore, the ambient temperature detection sensor 15 detects the temperature of the metal cover 2, and the CPU 13 calculates the temperature value of the thermal conduction delay due to the transient thermal response, and calculates a frequency correction value based on the temperature value and outputs it to the FPGA . Here, the “temperature value of thermal conduction delay” refers to the temperature value obtained when the reference crystal oscillator 11 receives heat conduction from the surroundings relative to the temperature value detected by the ambient temperature detection sensor 15 . The FPGA 14 corrects the oscillation frequency from the reference crystal oscillator 11 with the frequency correction value input from the CPU 13 .

[0029] [Parts of this oscillator] Next, each part of this oscillator will be specifically described. The reference crystal oscillator 11 includes a crystal resonator and oscillates a reference frequency. This reference crystal oscillator 11 has a frequency temperature characteristic in which the frequency characteristic changes depending on the ambient temperature. The frequency-voltage controlled oscillator 12 is a VCO (Voltage Controlled Oscillator) that changes the oscillation frequency according to a control voltage from the FPGA 14 and outputs the frequency.

[0030] The CPU 13 calculates the temperature value of the thermal conduction delay due to the transient thermal response based on the temperature detected by the ambient temperature detection sensor 15, and calculates the corresponding frequency correction value, and is provided with a frequency correction value calculation unit 13a and a transient thermal response calculation unit 13b.

[0031] The frequency correction value calculation unit 13a calculates a frequency correction value based on the temperature value input from the transient thermal response calculation unit 13b, and outputs the frequency correction value to the DDS 14a of the FPGA 14. The transient thermal response calculation unit 13b has a transient thermal calculation model that calculates the temperature value of the thermal conduction delay for the transient thermal response. The transient thermal calculation model is in a filter format as shown in the circuit of the schematic diagram described later, and has parameters. The transient thermal calculation model is obtained in advance by actual measurement or thermal simulation.

[0032] The FPGA 14 is an integrated circuit whose configuration can be set by a purchaser or designer after manufacture. A DDS (Digital Direct Synthesizer) 14a in the FPGA 14 is a device that freely modulates and outputs frequencies and waveforms, and corrects the reference frequency from the reference crystal oscillator 11 with a frequency correction value from a frequency correction value calculation unit 13a in the CPU 13.

[0033] In addition, a PLL (Phase Locked Loop) 14b in the FPGA 14 synchronizes the phase of the input signal and the output signal by inputting to the frequency-voltage controlled oscillator 12 the phase difference between an input signal of a reference frequency and a feedback signal of the output of the frequency-voltage controlled oscillator 12, whose frequency changes depending on the voltage.

[0034] The ambient temperature detection sensor 15 is a 16-bit high-precision temperature sensor IC that detects the temperature of the heat-conducting copper foil 16 connected to the metal cover 2 and outputs information on the detected temperature to the CPU 13 via I2C (Inter-Integrated Circuit) communication, which achieves high-speed communication with peripheral devices using a serial communication method. The heat-conducting copper foil 16 is a copper foil with high thermal conductivity printed on the substrate 1, and outputs the ambient temperature transmitted to the metal cover 2 to the ambient temperature detection sensor 15 almost simultaneously and with little error.

[0035] [Thermal circuit model of this oscillator: Figure 3] Next, the thermal circuit model of this oscillator will be explained with reference to Fig. 3. Fig. 3 is a schematic diagram of the thermal circuit model of this oscillator. Note that Fig. 3 is a schematic representation of the temperature change in this oscillator using thermal resistance and heat capacity. As shown in Figure 3, the thermal circuit model of this oscillator is configured such that a reference crystal oscillator 11 and an ambient temperature detection sensor 15 are connected in parallel to the positive side of the power supply voltage V2, and a transient thermal response calculation unit 13b is connected to the ambient temperature detection sensor 15. Each part is represented by a thermal resistance (R) and a thermal capacity (C).

[0036] In Figure 3, "Ta" indicates the ambient temperature, "T_Xtal" indicates the temperature of the quartz crystal plate (reference quartz crystal oscillator 11), "T_TaSensor" indicates the temperature of the ambient temperature detection sensor 15, and "T_Xtal_est" indicates the estimated temperature of the quartz crystal plate.

[0037] This quartz crystal plate estimated temperature is the temperature of the thermal conduction delay due to the transient thermal response, and corresponds to the temperature value calculated by the transient thermal response calculation unit 13b. Therefore, the transient thermal response calculation unit 13b holds the parameters of the resistance (R3) and capacitance (C3) shown in the schematic circuit of Figure 3 in a simulation, and calculates the quartz crystal plate estimated temperature (temperature of the thermal conduction delay for the transient thermal response) by calculation.

[0038] [Temperature tracking characteristics of this oscillator: Figure 4] Next, the temperature tracking characteristics of this oscillator will be explained with reference to Figure 4. Figure 4 is a graph of the temperature tracking characteristics of this oscillator. Figure 4 shows the graph in which the ambient temperature is increased and kept constant until 360 minutes, and then decreased from 400 minutes. As shown in FIG. 4, the temperature tracking characteristic of this oscillator is such that the temperature (T_Xtal) of the quartz crystal plate (reference quartz crystal oscillator 11) rises and falls with a delay relative to the rise and fall of the ambient temperature (Ta), but the rise and fall of the temperature (T_TaSensor) of the ambient temperature detection sensor 15 follows the temperature closer to the ambient temperature (Ta) than the quartz crystal plate temperature (T_Xtal).

[0039] The transient thermal response calculation unit 13b calculates a control value so that the quartz plate estimated temperature (T_Xtal_est) is the same as the quartz plate temperature (T_Xtal), and provides this to the DDS 14a in the FPGA 14.This enables the frequency correction value calculation unit 13a to calculate a frequency correction value using the quartz plate estimated temperature (T_Xtal_est), and the frequency-temperature characteristics of the reference crystal oscillator 11 are corrected in the DDS 14a.

[0040] [Effects of the embodiment] According to this oscillator, it is a surface mount type having a metal cover 2, and an ambient temperature detection sensor 15 for detecting temperature in order to correct the frequency-temperature characteristics is provided on a substrate 1 carrying a plurality of circuits, and the ambient temperature detection sensor 15 is positioned closer to the metal cover 2 than the reference crystal oscillator 11 having a crystal diaphragm and other circuits, and detects temperature via the heat-conducting copper foil 16 soldered to the metal cover 2 at the soldering portion 17, and the detected temperature is used to correct the frequency-temperature characteristics, so that the ambient temperature is detected before the temperature of the crystal diaphragm changes, preventing delays in the correction of the frequency-temperature characteristics and reducing hysteresis in the frequency-temperature characteristics.

[0041] In addition, according to this oscillator, the temperature value of the transient thermal response corresponding to the temperature change in the reference crystal oscillator 11 is calculated by the transient thermal response calculation unit 13b, and the frequency correction value calculation unit 13a calculates the frequency correction value based on that temperature value and outputs it to the DDS 14a in the FPGA 14, and the DDS 14a corrects the frequency-temperature characteristic of the reference frequency from the reference crystal oscillator 11. Therefore, the transient thermal response calculation unit 13b can calculate an estimated temperature that is close to the temperature change of the crystal diaphragm of the reference crystal oscillator 11, and the frequency correction value calculation unit 13a calculates the frequency correction value using that estimated temperature, thereby preventing delays in the correction of the frequency-temperature characteristic and reducing hysteresis in the frequency-temperature characteristic. [Industrial Applicability]

[0042] The present invention is suitable for an oscillator that can detect the ambient temperature before the temperature of the quartz crystal plate changes, prevent a delay in correcting the frequency-temperature characteristic, and reduce hysteresis in the frequency-temperature characteristic. [Explanation of symbols]

[0043] 1... Board, 2... Metal cover, 10... Thermistor, 11... Reference crystal oscillator, 12... Frequency-voltage controlled oscillator, 13... CPU (Central Processing Unit), 14... FPGA (Field Programmable Gate Array), 15... Ambient temperature detection sensor, 16... Copper foil for heat conduction, 17... Soldering section

Claims

1. A surface-mount oscillator having a metal cover, A temperature sensor is positioned on a circuit board on which multiple circuits are mounted, such that the distance to the metal cover is shorter than the distance to the multiple circuits, and detects the temperature via heat-conducting copper foil soldered to the metal cover in order to correct the frequency-temperature characteristics of the crystal diaphragm. A transient thermal response calculation unit calculates the estimated temperature of the quartz crystal diaphragm (T_Xtal_est) based on the temperature value (T_TaSensor) detected by the temperature sensor, which has a smaller heat conduction delay than the temperature of the quartz crystal diaphragm (T_Xtal) due to heat conduction delay caused by the conduction of heat from the ambient temperature (Ta) of the quartz crystal diaphragm, as the temperature value of the heat conduction delay that becomes the same as the temperature of the quartz crystal diaphragm (T_Xtal) obtained by simulation, and calculates a control value based on the estimated temperature of the quartz crystal diaphragm (T_Xtal_est), for the structural transient thermal response, An oscillator characterized by having a frequency correction value calculation unit that calculates a frequency temperature characteristic correction value based on the control value calculated from the estimated temperature of the crystal diaphragm.

2. The oscillator according to Claim 1, wherein the transient thermal response calculation unit includes a transient thermal model of the CR filter type that has parameters for thermal resistance and thermal capacitance of the transient thermal response obtained by simulation, and calculates the estimated temperature of the crystal diaphragm using the transient thermal model.

3. The oscillator according to claim 1 or 2, characterized in that the heat-conducting copper foil is soldered to the metal cover at the four corners of the substrate, and the temperature sensor is provided near the corner.

4. The oscillator according to claim 1 or 2, characterized in that the temperature sensor outputs the detected temperature to the transient thermal response calculation unit using a serial communication method of Inter-Integrated Circuit communication.

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