Oscillator

Abstract

Provided is an oscillator capable of detecting the ambient temperature before the temperature of a crystal oscillator changes, preventing the correction delay of frequency-temperature characteristics, and reducing the hysteresis of the frequency-temperature characteristics. In a surface mount type oscillator, an ambient temperature detection sensor (15) for detecting temperature in order to correct frequency temperature characteristics is provided on a substrate (1) on which a plurality of circuits are mounted, the ambient temperature detection sensor (15) being disposed closer to a metal cover (2) than a reference crystal oscillator (11) provided with a crystal piece and other circuits. The temperature is detected via a heat-conducting copper foil (16) welded to the metal cover (2) by a welding part (17), and the detected temperature is used to correct the frequency-temperature characteristics.

Description

Technical Field

[0001] This invention relates to oscillators, and more particularly to oscillators capable of detecting ambient temperature before temperature changes occur in the crystal oscillator, thereby preventing correction delays in frequency-temperature characteristics. Background Technology

[0002] [Previous technologies]

[0003] In conventional oscillators, a scheme is used to detect the temperature of a reference crystal oscillator equipped with a crystal oscillator chip. A thermistor is placed near the reference crystal oscillator, and a computing circuit (CPU: Central Processing Unit) is used to calculate the frequency correction amount corresponding to the detected temperature. The frequency temperature characteristics are then corrected using this frequency correction amount.

[0004] [Previous oscillators: Figure 5]

[0005] Next, referring to Figure 5, the structure of a conventional oscillator will be described. Figure 5 is an explanatory diagram of the side and plan views of a conventional oscillator. Furthermore, (a) is a side view and (b) is a plan view.

[0006] Regarding the conventional oscillators, as shown in Figure 5, they are surface-mounted, with the metal cover 2 fixed to the substrate 1 using the welding part 17.

[0007] The conventional oscillator substrate 1 includes 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 solder portions 17 formed at the four corners of the substrate 1.

[0008] Thermistor 10 is positioned near reference crystal oscillator 11 in order to sense the temperature of reference crystal oscillator 11.

[0009] [Previous oscillator circuit structure: Figure 6]

[0010] Next, referring to Figure 6, the circuit structure of a conventional oscillator will be described. Figure 6 is a schematic diagram of the circuit structure of a conventional oscillator.

[0011] In the conventional oscillator circuit structure, as shown in Figure 6, the oscillation frequency signal oscillated by the reference crystal oscillator 11 is input to the FPGA 14. The FPGA 14 outputs a control voltage to the frequency-voltage controlled oscillator 12, and the frequency-voltage controlled oscillator 12 outputs a specific frequency.

[0012] 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.

[0013] In FPGA14, the oscillation frequency from reference crystal oscillator 11 is corrected using the frequency correction value input from CPU13.

[0014] In addition, the voltage output from the thermistor 10 corresponds to the detected temperature. After being 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, where the frequency correction value calculation unit 13a calculates the frequency correction value.

[0015] In addition, FPGA14 features a DDS (Digital Direct Synthesizer) 14a and a PLL (Phase Locked Loop) 14b.

[0016] [Previous hot-loop model of oscillator: Figure 7]

[0017] Next, referring to Figure 7, the thermal loop model of a conventional oscillator will be explained. Figure 7 is a schematic diagram of the thermal loop model of a conventional oscillator. In addition, Figure 7 is a graph that schematically shows the temperature changes in a conventional oscillator using thermal resistance and thermal capacity.

[0018] The conventional thermal loop model of the oscillator is shown in Figure 7, which is a structure in which the reference crystal oscillator 11 and the thermistor 10 are connected in parallel on the positive side of the power supply voltage V2. Here, the power supply voltage is the result of replacing the ambient temperature with voltage.

[0019] Each part is represented by thermal resistance (R) and heat capacity (C).

[0020] In Figure 7, “Ta” represents the ambient temperature, “T_Xtal” represents the temperature of the crystal oscillator (reference crystal oscillator 11), and “T_Thermistor” represents the detection temperature of the thermistor 10.

[0021] [Temperature tracking characteristics of previous oscillators: Figure 8]

[0022] Next, referring to Figure 8, the temperature tracking characteristics of a conventional oscillator will be explained. Figure 8 is a graph showing the temperature tracking characteristics of a conventional oscillator. Figure 8 shows the ambient temperature rising and remaining constant for more than 360 minutes, and then decreasing from 400 minutes onwards.

[0023] Regarding the temperature tracking characteristics of conventional oscillators, as shown in Figure 8, the temperature (T_Xtal) of the crystal oscillator (reference crystal oscillator 11) rises and falls with a delay relative to the rise and fall of the ambient temperature (Ta), but the temperature (T_Thermistor) of the thermistor 10 tracks the rise and fall with an even greater delay than the temperature (T_Xtal) of the crystal oscillator.

[0024] Furthermore, the frequency correction value calculation unit 13a uses the temperature (T_Thermistor) of the thermistor 10 to calculate the frequency correction value and provides it to the DDS14a in the FPGA14, thereby using the DDS14a to correct the frequency temperature characteristics of the reference crystal oscillator 11.

[0025] [Related Technologies]

[0026] Furthermore, as a related prior art, there is Japanese Patent Application Publication No. 01-208904 entitled "Temperature Compensated Crystal Oscillator" (Patent Document 1).

[0027] Patent Document 1 shows a structure in a temperature-compensated crystal oscillator in which the response time of a temperature detector that detects the ambient temperature to a temperature change is equal to the response time of a crystal oscillating element to a temperature change.

[0028] Existing technical documents

[0029] Patent documents

[0030] Patent Document 1: Japanese Patent Application Publication No. 01-208904 Summary of the Invention

[0031] However, in conventional oscillators, it is impossible to quickly follow the temperature changes of the crystal oscillator inside the container, thus delaying the detection of temperature to correct the frequency temperature characteristics. Therefore, there is a delay in the correction of the frequency temperature characteristics, resulting in a hysteresis problem in the frequency temperature characteristics.

[0032] Furthermore, although the response characteristics of the temperature detector to temperature changes were improved in Patent Document 1, there was still a delay in the sound frequency correction due to the structure for tracking the detected temperature.

[0033] Therefore, in Patent Document 1, a structure that can prevent the correction delay of frequency temperature characteristics and reduce the hysteresis of frequency temperature characteristics is not shown.

[0034] The present invention was made in view of the above-mentioned actual situation, and its object is to provide an oscillator that can detect the ambient temperature before the temperature of the crystal oscillator changes, thereby preventing the correction delay of the frequency temperature characteristics and reducing the hysteresis of the frequency temperature characteristics.

[0035] To address the problems of the aforementioned prior art, the present invention provides a surface-mount oscillator with a metal cover, wherein a temperature sensor for detecting temperature to correct the frequency-temperature characteristics of a crystal oscillator is provided on a substrate on which multiple circuits are mounted. The temperature sensor is positioned at a distance from the metal cover that is shorter than the distance from the multiple circuits, and the temperature is detected via a heat-conducting copper foil soldered to the metal cover.

[0036] In the oscillator described above, copper foil for heat conduction is soldered to a metal cover at the four corners of the substrate, and a temperature sensor is positioned near these corners.

[0037] The present invention includes, in the above-described oscillator, a transition thermal response calculation unit that calculates or estimates the amount of temperature variation in the crystal oscillator that takes into account the transition thermal response of the structure, based on the temperature detected by a temperature sensor; and a frequency correction value calculation unit that calculates a correction value for the frequency temperature characteristic based on the calculated temperature variation.

[0038] In the aforementioned oscillator, the transient thermal response calculation unit of this invention possesses a transient thermal model in the form of a CR filter through simulation. This transient thermal model is used to calculate the temperature variation in the crystal oscillator. The transient thermal calculation model in the form of a CR filter has parameters such as the thermal resistance and thermal capacity of the transient thermal response.

[0039] According to the present invention, by providing a surface-mount type oscillator with a metal cover, wherein a temperature sensor for detecting the temperature to correct the frequency-temperature characteristics of the crystal oscillator is provided on a substrate on which multiple circuits are mounted, the temperature sensor is positioned at a distance from the metal cover that is shorter than the distance from the multiple circuit components, and the temperature is detected by means of a heat-conducting copper foil soldered to the metal cover, thus having the effect of detecting the ambient temperature before the crystal oscillator, preventing the correction delay of the frequency-temperature characteristics, and reducing the hysteresis of the frequency-temperature characteristics. Attached Figure Description

[0040] Figure 1 is an illustrative diagram of the side and plan view of this oscillator.

[0041] Figure 2 is a schematic diagram of the circuit structure of this oscillator.

[0042] Figure 3 is a schematic diagram of the thermal circuit model of this oscillator.

[0043] Figure 4 is a graph showing the temperature tracking characteristics of this oscillator.

[0044] Figure 5 is an illustrative diagram of the side and plan view of a conventional oscillator.

[0045] Figure 6 is a schematic diagram of the circuit structure of a conventional oscillator.

[0046] Figure 7 is a schematic diagram of the thermal loop model of a previous oscillator.

[0047] Figure 8 is a graph showing the temperature tracking characteristics of a previous oscillator. Detailed Implementation

[0048] The embodiments of the present invention will be described with reference to the accompanying drawings.

[0049] [Summary of Implementation Methods]

[0050] The oscillator (this oscillator) of the embodiment of the present invention is a surface-mount crystal oscillator with a metal cover. On a substrate on which multiple circuits are mounted, a temperature sensor is provided to detect the temperature for correcting the frequency temperature characteristics. The temperature sensor is positioned at a distance from the metal cover that is shorter than the distance from the reference crystal oscillator with the crystal oscillator and other circuits. The temperature is detected by a heat-conducting copper foil soldered to the metal cover. The detected temperature is used to correct the frequency temperature characteristics. The ambient temperature can be detected before the temperature of the crystal oscillator changes, thereby preventing the correction delay of the frequency temperature characteristics and reducing the hysteresis of the frequency temperature characteristics.

[0051] [This oscillator: Figure 1]

[0052] Referring to Figure 1, the structure of this oscillator will be described. Figure 1 is an explanatory diagram of the side and plan view of this oscillator. Furthermore, (a) is an explanatory diagram of the side view, and (b) is an explanatory diagram of the plan view.

[0053] As shown in Figure 1, this oscillator is a surface-mount type, with the metal cover 2 fixed to the substrate 1 by the welding part 17.

[0054] The substrate 1 of this oscillator includes 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 sensor 15, solder joints 17 formed at the four corners of the substrate 1, and a heat-conducting copper foil 16 connecting the ambient temperature sensor 15 and the solder joints 17.

[0055] Furthermore, the various parts of this oscillator will be described later.

[0056] In addition, as shown in Figure 1(2), the ambient temperature sensor 15 is located closer to the metal cover 2 and closer to the corner portion 17, which is one of the four corners of the substrate 1, in order to detect the temperature of the metal cover 2. It is connected to the solder portion 17 via the heat conduction copper foil 16.

[0057] That is, the ambient temperature sensor 15 is positioned at a distance from the metal cover 2 that is shorter than the distance from other circuits, and detects the temperature of the metal cover 2 via the heat conduction copper foil 16 and the solder joint 17.

[0058] [Circuit structure of this oscillator: Figure 2]

[0059] Next, referring to Figure 2, the circuit structure of this oscillator will be described. Figure 2 is a schematic diagram of the circuit structure of this oscillator.

[0060] The circuit structure of this oscillator is shown in Figure 2. The oscillation frequency signal oscillated by the reference crystal oscillator 11 is input to the FPGA 14. The FPGA 14 outputs a control voltage to the frequency-voltage controlled oscillator 12, and outputs a specific frequency from the frequency-voltage controlled oscillator 12.

[0061] In addition, the ambient temperature sensor 15 detects the temperature of the metal cover 2, the CPU 13 calculates the temperature value of the heat conduction delay caused by the overheating response, calculates the frequency correction value based on the temperature value and outputs it to the FPGA 14.

[0062] Here, "temperature value with thermal conduction delay" refers to the temperature value obtained by the reference crystal oscillator 11 from the conduction of heat from the surrounding environment, relative to the temperature value detected by the ambient temperature detection sensor 15.

[0063] In FPGA14, the oscillation frequency from reference crystal oscillator 11 is corrected using the frequency correction value input from CPU13.

[0064] [Components of this oscillator]

[0065] Next, the various parts of this oscillator will be explained in detail.

[0066] The reference crystal oscillator 11 has a crystal oscillator that oscillates to produce a reference frequency.

[0067] The reference crystal oscillator 11 has a frequency-temperature characteristic whose frequency characteristics vary with the ambient temperature.

[0068] The frequency-voltage controlled oscillator 12 is a VCO (Voltage Controlled Oscillator) that outputs a frequency by changing the oscillation frequency through a control voltage from the FPGA 14.

[0069] The CPU 13 calculates the temperature value of the heat conduction delay caused by the transient thermal response based on the temperature detected by the ambient temperature sensor 15, and calculates the corresponding frequency correction value. It includes a frequency correction value calculation unit 13a and a transient thermal response calculation unit 13b.

[0070] The frequency correction value calculation unit 13a calculates the frequency correction value based on the temperature value input from the transition thermal response calculation unit 13b, and outputs it to the DDS14a of the FPGA14.

[0071] The transient thermal response calculation unit 13b has a transient thermal calculation model for calculating the temperature value of the heat conduction delay for the transient thermal response. The transient thermal calculation model is in the form of a filter as shown in the circuit diagram below, and has parameters. The transient thermal calculation model is pre-determined through actual measurement or thermal simulation.

[0072] FPGA14 is an integrated circuit whose structure can be defined by the purchaser or designer after manufacturing.

[0073] The DDS (Digital Direct Synthesizer) 14a inside the FPGA 14 is a device that freely modulates the frequency and waveform and outputs them. It uses the frequency correction value from the frequency correction value calculation unit 13a of the CPU 13 to correct the reference frequency from the reference crystal oscillator 11.

[0074] In addition, the PLL (Phase Locked Loop) 14b in FPGA14 synchronizes the phases of the input signal and the output signal by inputting the phase difference between the input signal of the reference frequency and the feedback signal of the output of the frequency-voltage controlled oscillator 12, whose frequency varies with voltage.

[0075] The ambient temperature sensor 15 is a 16-bit high-precision temperature sensor IC that detects the temperature of the heat conduction copper foil 16 connected to the metal cover 2. It outputs the detected temperature information to the CPU 13 through I2C (Inter-Integrated Circuit) communication, which enables high-speed communication with peripheral devices via serial communication.

[0076] Regarding the copper foil 16 for heat conduction, a copper foil with high thermal conductivity is printed on the substrate 1, which outputs the ambient temperature transferred to the metal cover 2 to the ambient temperature detection sensor 15 approximately simultaneously with less error.

[0077] [Thermal circuit model of this oscillator: Figure 3]

[0078] Next, referring to Figure 3, the thermal circuit model of this oscillator will be explained. Figure 3 is a schematic diagram of the thermal circuit model of this oscillator. In addition, Figure 3 is a graph that schematically shows the temperature change in this oscillator using thermal resistance and thermal capacity.

[0079] The thermal circuit model of this oscillator is shown in Figure 3. It consists of a reference crystal oscillator 11 and an ambient temperature sensor 15 connected in parallel on the positive side of the power supply voltage V2, and an ambient temperature sensor 15 connected to a transition thermal response calculation unit 13b.

[0080] Each part is represented by thermal resistance (R) and heat capacity (C).

[0081] In Figure 3, “Ta” represents the ambient temperature, “T_Xtal” represents the temperature of the crystal oscillator (reference crystal oscillator 11), “T_TaSensor” represents the temperature of the ambient temperature sensor 15, and “T_Xtal_est” represents the estimated temperature of the crystal oscillator.

[0082] The predicted temperature of the crystal oscillator is the temperature of the thermal conduction delay caused by the transient thermal response. The temperature value calculated by the transient thermal response calculation unit 13b is equivalent to the predicted temperature of the crystal oscillator. Therefore, in the transient thermal response calculation unit 13b, the predicted temperature of the crystal oscillator (the temperature of the thermal conduction delay due to the transient thermal response) is calculated by simulating the parameters of the resistor (R3) and capacitor (C3) shown in the schematic circuit of FIG3.

[0083] [Temperature tracking characteristics of this oscillator: Figure 4]

[0084] Next, referring to Figure 4, the temperature tracking characteristics of this oscillator will be explained. Figure 4 is a graph showing the temperature tracking characteristics of this oscillator. Figure 4 shows the curves of ambient temperature rising and remaining constant for more than 360 minutes, and then decreasing from 400 minutes onwards.

[0085] Regarding the temperature tracking characteristics of this oscillator, as shown in Figure 4, the temperature (T_Xtal) of the crystal oscillator (reference crystal oscillator 11) rises and falls with a delay relative to the ambient temperature (Ta), but the temperature (T_TaSensor) of the ambient temperature detection sensor 15 tracks the temperature at a position closer to the ambient temperature (Ta) than the crystal oscillator temperature (T_Xtal).

[0086] Furthermore, in the transition thermal response calculation unit 13b, the control value is calculated in such a way that the estimated temperature (T_Xtal_est) of the crystal oscillator is the same as the temperature (T_Xtal) of the crystal oscillator, and the control value is provided to the DDS14a in the FPGA14. The frequency correction value calculation unit 13a can use the estimated temperature (T_Xtal_est) of the crystal oscillator to calculate the frequency correction value, and use the DDS14a to correct the frequency temperature characteristics of the reference crystal oscillator 11.

[0087] [Effects of the Implementation Method]

[0088] This oscillator is a surface-mount type oscillator with a metal cover 2. On the substrate 1 on which multiple circuits are mounted, an ambient temperature sensor 15 is provided to detect the temperature for correcting the frequency temperature characteristics. The ambient temperature sensor 15 is configured to be closer to the metal cover 2 than the reference crystal oscillator 11 with the crystal oscillator and other circuits. The temperature is detected by a heat-conducting copper foil 16 that is soldered to the metal cover 2 by a solder joint 17. The detected temperature is used to correct the frequency temperature characteristics. Therefore, it has the effect of detecting the ambient temperature before the temperature of the crystal oscillator changes, thus preventing the correction delay of the frequency temperature characteristics and reducing the hysteresis of the frequency temperature characteristics.

[0089] Furthermore, according to this oscillator, the transition thermal response calculation unit 13b calculates the temperature value of the transition thermal response in the reference crystal oscillator 11 corresponding to the temperature change, and the frequency correction value calculation unit 13a calculates the frequency correction value based on the temperature value and outputs it to the DDS 14a in the FPGA 14. The DDS 14a corrects the frequency temperature characteristics of the reference frequency from the reference crystal oscillator 11, so the transition thermal response calculation unit 13b can calculate the estimated temperature close to the temperature change of the crystal oscillator chip of the reference crystal oscillator 11. The frequency correction value calculation unit 13a calculates the frequency correction value using the estimated temperature, so it has the effect of preventing the correction delay of the frequency temperature characteristics and reducing the hysteresis of the frequency temperature characteristics.

[0090] Industrial availability

[0091] This invention is applicable to oscillators that can detect ambient temperature before the temperature of the crystal oscillator changes, thereby preventing the correction delay of frequency temperature characteristics and reducing the hysteresis of frequency temperature characteristics.

[0092] (Symbol Explanation)

[0093] 1: Substrate; 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 sensor; 16: Copper foil for heat conduction; 17: Soldering part.

Claims

1. A surface-mounted oscillator with a metal shield, wherein, A temperature sensor is configured on a substrate carrying multiple circuits to detect temperature in order to correct the frequency-temperature characteristics of a crystal oscillator. The temperature sensor is positioned at a distance from the metal cover that is shorter than the distance from the plurality of circuits, and detects the temperature via a heat-conducting copper foil welded to the metal cover.

2. The oscillator according to claim 1, wherein, Copper foil for heat conduction is soldered to a metal cover at the four corners of the substrate, and temperature sensors are placed near these corners.

3. The oscillator according to claim 1 or 2, wherein, The oscillator has: The transition thermal response calculation unit calculates the temperature variation in the crystal oscillator that takes into account the structural transition thermal response, based on the temperature detected by the temperature sensor. as well as The frequency correction value calculation unit calculates the correction value of the frequency temperature characteristic based on the calculated temperature variation.

4. The oscillator according to claim 3, wherein, The transition thermal response calculation unit has a transition thermal model in the form of a CR filter through simulation. This transition thermal model is used to calculate the temperature variation in the crystal oscillator. The transition thermal calculation model in the form of a CR filter has parameters such as the thermal resistance and thermal capacity of the transition thermal response.

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