Crystal oscillator

Abstract

The embodiment of the invention discloses a crystal oscillator. The crystal oscillator comprises a voltage reference circuit, a power supply circuit, an oscillating circuit, a compensating circuit, a heating control circuit and a frequency-selecting amplifying circuit, wherein the voltage reference circuit is electrically connected with the power circuit, the oscillating circuit, the compensating circuit and the heating control circuit, the heating control circuit is close to the oscillating circuit, the power circuit is electrically connected with the frequency-selecting amplifying circuit, the compensating circuit is electrically connected with the heating control circuit and the oscillating circuit, and the oscillating circuit is electrically connected with the frequency-selecting amplifying circuit. The frequency-selecting amplifying circuit and the power supply circuit are both provided with triodes; the oscillating circuit is used for generating an oscillating signal, the compensating circuit is used for compensating the oscillating signal, the heating control circuit is used for performing heating control on the oscillating circuit, and the frequency-selecting amplifying circuit is used for performing frequency-selecting amplification and outputting on the oscillating signal. According to the crystal oscillator provided by the embodiment of the invention, the ultra-low short-term stability index of the crystal oscillator can be ensured.

Description

Technical Field

[0001] This invention relates to oscillator technology, and more particularly to a crystal oscillator. Background Technology

[0002] Crystal oscillators, as a reference source, are widely used in modern electronic warfare, navigation, communication, and measurement and control systems due to their inherent characteristics. However, existing crystal oscillators currently face the challenge of achieving ultra-low short-term stability. Summary of the Invention

[0003] This invention provides a crystal oscillator to ensure ultra-low short-term stability.

[0004] This invention provides a crystal oscillator, comprising: a voltage reference circuit, a power supply circuit, an oscillation circuit, a compensation circuit, a heating control circuit, and a frequency selective amplifier circuit;

[0005] The voltage reference circuit is electrically connected to the power supply circuit, the oscillation circuit, the compensation circuit, and the heating control circuit. The heating control circuit is located close to the oscillation circuit. The power supply circuit is electrically connected to the frequency selective amplifier circuit. The compensation circuit is electrically connected to the heating control circuit and the oscillation circuit. The oscillation circuit is electrically connected to the frequency selective amplifier circuit. Both the frequency selective amplifier circuit and the power supply circuit are equipped with transistors.

[0006] The voltage reference circuit and the power supply circuit are used to provide stable voltages of different magnitudes. The oscillation circuit is used to generate an oscillation signal. The compensation circuit is used to compensate the oscillation signal. The heating control circuit is used to control the heating of the oscillation circuit. The frequency selective amplifier circuit is used to selectively amplify the oscillation signal and output it.

[0007] Optionally, the frequency selective amplifier circuit includes a first frequency selective amplifier module and a second frequency selective amplifier module. The structures of the first frequency selective amplifier module and the second frequency selective amplifier module are the same. The input terminal of the first frequency selective amplifier module is electrically connected to the output terminal of the oscillation circuit, and the output terminal of the first frequency selective amplifier module is electrically connected to the input terminal of the second frequency selective amplifier module. The output terminal of the second frequency selective amplifier module serves as the output terminal of the frequency selective amplifier circuit.

[0008] Optionally, the first frequency selective amplifier module includes a first inductor, a second inductor, a third inductor, and a first MOSFET; the first end of the first inductor is electrically connected to the output terminal of the oscillation circuit through a capacitor, the first end of the first inductor is electrically connected to the first electrode of the first MOSFET, the second end of the first inductor is electrically connected to the gate of the first MOSFET through a resistor, the second end of the first inductor is grounded through the resistor, the second electrode of the first MOSFET is electrically connected to the first end of the second inductor through a resistor, the first end of the second inductor is grounded through a capacitor, the second end of the second inductor is electrically connected to the power supply circuit through the third inductor, and the second end of the second inductor serves as the output terminal of the first frequency selective amplifier module.

[0009] Optionally, the voltage reference circuit includes a voltage reference, a resistor, and multiple parallel capacitors. The power supply terminal of the voltage reference is electrically connected to an external power supply through the resistor. The output terminal of the voltage reference serves as the output terminal of the voltage reference circuit. The output terminal of the voltage reference is grounded through the multiple parallel capacitors.

[0010] Optionally, the power supply circuit is a low-noise power supply circuit, which includes a first amplifier and a first transistor; the non-inverting input terminal of the first amplifier is electrically connected to the output terminal of the voltage reference circuit through a resistor, the non-inverting input terminal of the first amplifier is grounded through a capacitor, the inverting input terminal of the first amplifier is electrically connected to the non-inverting input terminal of the first amplifier in sequence through a resistor and a capacitor, the output terminal of the first amplifier is electrically connected to the base of the first transistor, the first terminal of the first transistor is electrically connected to an external power supply, the second terminal of the first transistor is electrically connected to the output terminal of the first amplifier in sequence through a resistor and a capacitor, and the second terminal of the first transistor is electrically connected to the frequency selective amplifier circuit through a resistor.

[0011] Optionally, the oscillation circuit includes a crystal, a second transistor, and a varactor diode; the first terminal of the crystal is electrically connected to the base of the second transistor through a capacitor, and the first terminal of the crystal is electrically connected to the output terminal of the voltage reference circuit through the capacitor and multiple resistors in sequence; the first terminal of the second transistor is electrically connected to the output terminal of the voltage reference circuit through a resistor and a capacitor respectively; the second terminal of the second transistor is grounded through a resistor; the second terminal of the crystal is electrically connected to the negative terminal of the varactor diode through a capacitor; the second terminal of the crystal is connected to an external voltage control signal and the compensation circuit in sequence through a capacitor and a resistor; and the positive terminal of the varactor diode serves as the output terminal of the oscillation circuit.

[0012] Optionally, the heating control circuit includes a thermistor, a second amplifier, a third amplifier, a second MOSFET, and a third MOSFET; the non-inverting input of the second amplifier is electrically connected to the output of the compensation circuit and the voltage reference circuit; the inverting input of the second amplifier is electrically connected to the first terminal of the thermistor through a resistor; the second terminal of the thermistor is grounded; the first terminal of the thermistor is electrically connected to the output of the voltage reference circuit through a resistor; the output of the second amplifier is electrically connected to the non-inverting input of the third amplifier through a resistor; the non-inverting input of the third amplifier is electrically connected to an external power supply through a resistor; the inverting input of the third amplifier is electrically connected to the voltage reference circuit through a resistor; the output of the third amplifier is electrically connected to the gates of the second MOSFET and the third MOSFET through a resistor; the first terminals of the second MOSFET and the third MOSFET are electrically connected to the external power supply; and the second terminals of the second MOSFET and the third MOSFET are grounded.

[0013] Optionally, the thermistor, the second MOSFET, and the third MOSFET are located close to the oscillation circuit.

[0014] Optionally, the compensation circuit includes a digital potentiometer and a resistor. The power supply terminal of the digital potentiometer is electrically connected to the output terminal of the voltage reference circuit. The first output terminal of the digital potentiometer is electrically connected to the heating control circuit. The second output terminal of the digital potentiometer is electrically connected to the oscillation circuit through the resistor.

[0015] Optionally, the crystal oscillator further includes a housing, a base, a first circuit board, and a second circuit board, wherein the first circuit board and the second circuit board are located on the base and inside the housing, the power supply circuit and the frequency selective amplifier circuit are located on the first circuit board, and the voltage reference circuit, the compensation circuit, the oscillation circuit and the heating control circuit are located on the second circuit board.

[0016] The crystal oscillator provided in this embodiment of the invention includes: a voltage reference circuit, a power supply circuit, an oscillation circuit, a compensation circuit, a heating control circuit, and a frequency selective amplifier circuit. The voltage reference circuit is electrically connected to the power supply circuit, the oscillation circuit, the compensation circuit, and the heating control circuit. The heating control circuit is located close to the oscillation circuit. The power supply circuit is electrically connected to the frequency selective amplifier circuit. The compensation circuit is electrically connected to both the heating control circuit and the oscillation circuit. The oscillation circuit is electrically connected to the frequency selective amplifier circuit. Both the frequency selective amplifier circuit and the power supply circuit are equipped with transistors. The voltage reference circuit and the power supply circuit provide stable voltages of varying magnitudes. The oscillation circuit generates an oscillation signal. The compensation circuit compensates for the oscillation signal. The heating control circuit controls the heating of the oscillation circuit. The frequency selective amplifier circuit amplifies the oscillation signal and outputs it. The crystal oscillator provided in this embodiment of the invention compensates for the oscillation signal generated by the oscillation circuit through the compensation circuit to ensure the stability of the frequency accuracy of the oscillation signal. Furthermore, the frequency selective amplifier circuit and the power supply circuit are equipped with transistors to ensure the effect of frequency selective amplification and power supply stability, thereby ensuring the ultra-low short-term stability index of the crystal oscillator and the stability of the frequency accuracy of the oscillation signal. Attached Figure Description

[0017] Figure 1 This is a structural block diagram of a crystal oscillator provided in an embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram of a frequency-selective amplifier circuit provided in an embodiment of the present invention;

[0019] Figure 3 This is a schematic diagram of a voltage reference circuit provided in an embodiment of the present invention;

[0020] Figure 4 This is a schematic diagram of a power supply circuit provided in an embodiment of the present invention;

[0021] Figure 5 This is a schematic diagram of an oscillation circuit provided in an embodiment of the present invention;

[0022] Figure 6 This is a schematic diagram of a heating control circuit provided in an embodiment of the present invention;

[0023] Figure 7 This is a schematic diagram of a compensation circuit provided in an embodiment of the present invention;

[0024] Figure 8 This is a schematic diagram of the structure of a crystal oscillator provided in an embodiment of the present invention. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0026] Figure 1 This is a structural block diagram of a crystal oscillator provided in an embodiment of the present invention. (Reference) Figure 1 The crystal oscillator includes: a voltage reference circuit 10, a power supply circuit 20, an oscillation circuit 30, a compensation circuit 40, a heating control circuit 50, and a frequency selective amplifier circuit 60. The voltage reference circuit 10 is electrically connected to the power supply circuit 20, the oscillation circuit 30, the compensation circuit 40, and the heating control circuit 50. The heating control circuit 50 is located close to the oscillation circuit 30. The power supply circuit 20 is electrically connected to the frequency selective amplifier circuit 60. The compensation circuit 40 is electrically connected to both the heating control circuit 50 and the oscillation circuit 60. The oscillation circuit 30 is electrically connected to the frequency selective amplifier circuit 60. Both the frequency selective amplifier circuit 60 and the power supply circuit 20 are equipped with transistors. The voltage reference circuit 10 and the power supply circuit 20 provide stable voltages of varying magnitudes. The oscillation circuit 30 generates an oscillation signal. The compensation circuit 40 compensates for the oscillation signal. The heating control circuit 50 controls the heating of the oscillation circuit 30. The frequency selective amplifier circuit 60 amplifies and outputs the oscillation signal.

[0027] Specifically, the voltage reference circuit 10 supplies power to the power supply circuit 20, the oscillation circuit 30, the compensation circuit 40, and the heating control circuit 50. The power supply circuit 20 supplies power to the frequency selective amplifier circuit 60. One end of the compensation circuit 40 connected to the oscillation circuit 30 transmits an adjustable voltage signal to compensate for the input voltage of the oscillation circuit 30. The other end of the compensation circuit 40 connected to the heating control circuit 50 transmits another adjustable voltage signal to compensate for the input voltage of the heating control circuit 50. This allows the heating temperature of the oscillation circuit 30 to be adjustable by the heating control circuit 50, ensuring the stability of the oscillation signal generated by the oscillation circuit 30. The oscillation signal generated by the oscillation circuit 30, such as a 10MHz oscillation signal, is amplified by the frequency selective amplifier circuit 60 before being output. Furthermore, both the frequency selective amplifier circuit 60 and the power supply circuit 20 are equipped with transistors to ensure the effectiveness of the frequency selective amplification and the stability of the power supply, thereby ensuring the stability of the crystal oscillator's ultra-low short-term stability index (ultra-low refers to low frequency error per second, and short-term stability refers to the short-term stability of the crystal oscillator) and the frequency accuracy of the oscillation signal.

[0028] The crystal oscillator provided in this embodiment includes: a voltage reference circuit, a power supply circuit, an oscillation circuit, a compensation circuit, a heating control circuit, and a frequency selective amplifier circuit. The voltage reference circuit is electrically connected to the power supply circuit, the oscillation circuit, the compensation circuit, and the heating control circuit. The heating control circuit is located close to the oscillation circuit. The power supply circuit is electrically connected to the frequency selective amplifier circuit. The compensation circuit is electrically connected to both the heating control circuit and the oscillation circuit. The oscillation circuit is electrically connected to the frequency selective amplifier circuit. Both the frequency selective amplifier circuit and the power supply circuit are equipped with transistors. The voltage reference circuit and the power supply circuit provide stable voltages of varying magnitudes. The oscillation circuit generates an oscillation signal. The compensation circuit compensates for the oscillation signal. The heating control circuit controls the heating of the oscillation circuit. The frequency selective amplifier circuit amplifies the oscillation signal and outputs it. The crystal oscillator provided in this embodiment compensates for the oscillation signal generated by the oscillation circuit through the compensation circuit to ensure the stability of the oscillation signal's frequency accuracy. Furthermore, the frequency selective amplifier circuit and the power supply circuit are equipped with transistors to ensure the effectiveness of the frequency selective amplification and power supply stability, thereby ensuring the ultra-low short-term stability index of the crystal oscillator and the stability of the oscillation signal's frequency accuracy.

[0029] Figure 2 This is a schematic diagram of a frequency-selective amplifier circuit provided in an embodiment of the present invention. (Reference) Figure 2 Optionally, the frequency selective amplifier circuit 60 includes a first frequency selective amplifier module 61 and a second frequency selective amplifier module 62. The structures of the first frequency selective amplifier module 61 and the second frequency selective amplifier module 62 are identical. The input terminal of the first frequency selective amplifier module 61 is electrically connected to the output terminal of the oscillation circuit 30, and the output terminal of the first frequency selective amplifier module 61 is electrically connected to the input terminal of the second frequency selective amplifier module 61. The output terminal of the second frequency selective amplifier module 61 serves as the output terminal of the frequency selective amplifier circuit 60. Specifically, the oscillation signal output by the oscillation circuit 30 is sequentially amplified by the first frequency selective amplifier module 61 and the second frequency selective amplifier module 62. The output terminal of the second frequency selective amplifier module 61 outputs the frequency selectively amplified oscillation signal, thereby achieving frequency selective amplification of the oscillation signal and ensuring that the oscillation signal meets the actual requirements.

[0030] refer to Figure 2Optionally, the first frequency selective amplifier module 61 includes a first inductor L1, a second inductor L2, a third inductor L3, and a first MOSFET M1; the first end of the first inductor L1 is electrically connected to the output terminal of the oscillation circuit through a capacitor, the first end of the first inductor L1 is electrically connected to the first electrode of the first MOSFET M1, the second end of the first inductor L1 is electrically connected to the gate of the first MOSFET M1 through a resistor, the second end of the first inductor L1 is grounded through a resistor, the second electrode of the first MOSFET M1 is electrically connected to the first end of the second inductor L2 through a resistor, the first end of the second inductor L2 is grounded through a capacitor, the second end of the second inductor L2 is electrically connected to the power supply circuit 20 through the third inductor L3, and the second end of the second inductor L2 serves as the output terminal of the first frequency selective amplifier module 61. Specifically, when the first MOSFET M1 is turned on, the oscillation signal S output by the oscillation circuit 30 is sequentially output to the second frequency selective amplifier module 62 through the first MOSFET M1 and the second inductor L2. The voltage signal VD1 output by the power supply circuit 20, such as a 10V DC voltage signal, is transmitted to the second frequency selective amplifier module 62 through the third inductor L3. When the first MOSFET M1 is turned off, the voltage signal output by the power supply circuit 20 is transmitted to the second frequency selective amplifier module 62. Thus, when the first MOSFET M1 is turned on, the first frequency selective amplifier module 61 outputs both the oscillation signal and the voltage signal; when the first MOSFET M1 is turned off, the first frequency selective amplifier module 61 outputs the voltage signal to the second frequency selective amplifier module 62, thereby achieving frequency selective amplification of the oscillation signal through the first frequency selective amplifier module 61.

[0031] Furthermore, such as Figure 2 As shown, the second frequency selective amplifier module 62 includes a fourth inductor L4, a fifth inductor L5, a sixth inductor L6, and a second MOSFET M2. The first end of the fourth inductor L4 is electrically connected to the output terminal of the first frequency selective amplifier module 61, i.e., the second end of the second inductor L2, through a capacitor. The first end of the fourth inductor L4 is electrically connected to the first electrode of the second MOSFET M2. The second end of the fourth inductor L4 is electrically connected to the gate of the second MOSFET M2 through a resistor. The second end of the fourth inductor L4 is grounded through a resistor. The second electrode of the second MOSFET M2 is electrically connected to the first end of the fifth inductor L5 through a resistor. The first end of the fifth inductor L5 is grounded through a capacitor. The second end of the fifth inductor L5 is electrically connected to the power supply circuit 20 through the sixth inductor L6. The second end of the fifth inductor L5 serves as the output terminal OUT of the first frequency selective amplifier module 61.

[0032] In addition, such as Figure 2As shown, the first terminal of the second inductor L2 is grounded through two parallel capacitors. One terminal of the third inductor L3 is electrically connected to the second inductor L2, and the other terminal of the third inductor L3, which is the terminal connected to the power supply circuit 20, is grounded through a capacitor. Similarly, the first terminal of the fifth inductor L5 is grounded through two parallel capacitors. One terminal of the fifth inductor L5 is electrically connected to the fourth inductor L4, and the other terminal of the fifth inductor L5, which is the terminal connected to the third inductor L3 and the power supply circuit 20, is grounded through a capacitor.

[0033] Figure 3 This is a schematic diagram of a voltage reference circuit provided in an embodiment of the present invention. (Reference) Figure 3 Optionally, the voltage reference circuit 10 includes a voltage reference U4, a resistor, and multiple parallel capacitors. The power supply terminal of the voltage reference U4 is electrically connected to the external power supply VD2 through the resistor. The output terminal of the voltage reference U4 serves as the output terminal of the voltage reference circuit 10. The output terminal of the voltage reference U4 is grounded through multiple parallel capacitors.

[0034] Specifically, the voltage reference U4 outputs a voltage signal VD3. For example, the voltage signal VD3 is a 5V DC voltage signal, which powers the circuit that requires a 5V DC power supply, while the external power supply VD2 has a 12V DC voltage.

[0035] Furthermore, voltage reference U4 provides a stable voltage; that is, the voltage signal VD3 output from the output terminal of voltage reference U4 is stable, providing an accurate and stable voltage reference for the crystal oscillator. The working principle of voltage reference U4 is as follows: Zener diode reference, bandgap voltage reference, transistor reference, or capacitive voltage divider reference. Zener diode reference: operates using Zener breakdown characteristics; when the reverse bias voltage exceeds a certain value, the Zener diode enters the breakdown region and generates a relatively constant voltage, which can be used as a reference. Bandgap voltage reference: utilizes the energy difference generated by different types of charge carriers (electrons and holes) in semiconductor materials to generate a voltage independent of temperature changes through specific circuit design. Transistor reference: uses the base-emitter voltage of a transistor as a reference voltage source; with proper design, a stable voltage output can be generated. Capacitive voltage divider reference: provides a stable voltage reference through a capacitive voltage divider circuit. Furthermore, the voltage reference U4 can be categorized into several types, including series voltage reference sources, shunt voltage reference sources, voltage reference sources combined with comparators, and voltage reference sources combined with amplifiers. Series voltage reference sources function similarly to three-terminal regulators, featuring low dropout voltage, low power consumption, and excellent voltage regulation performance. They consume load and quiescent current only from the input power supply. Some series voltage reference sources can also operate in shunt mode. Shunt voltage reference sources operate similarly to Zener diodes, requiring a bias current higher than the sum of the maximum quiescent current and the maximum expected load current. They can operate under various input voltage conditions. Voltage reference sources combined with comparators or amplifiers combine the excellent initial accuracy and low over-temperature drift performance of a single-function voltage reference source with a comparator, buffer amplifier, and current sense amplifier to provide a stable voltage reference.

[0036] In addition, such as Figure 3 As shown, the power supply terminal of voltage reference U4 is electrically connected to the external power supply VD2 through a resistor. One end of the resistor connected to the external power supply VD2 is grounded through two parallel capacitors, and the other end of the resistor is grounded through a capacitor. The output terminal of voltage reference U4 is grounded through three parallel capacitors.

[0037] Figure 4 This is a schematic diagram of a power supply circuit provided in an embodiment of the present invention. (Reference) Figure 4Optionally, the power supply circuit 20 is a low-noise power supply circuit, which includes a first amplifier U1 and a first transistor Q1. The non-inverting input terminal of the first amplifier U1 is electrically connected to the output terminal of the voltage reference circuit 10 through a resistor, and the non-inverting input terminal of the first amplifier U1 is grounded through a capacitor. The inverting input terminal of the first amplifier U1 is electrically connected to the non-inverting input terminal of the first amplifier U1 in sequence through a resistor and a capacitor. The output terminal of the first amplifier U1 is electrically connected to the base of the first transistor Q1. The first terminal of the first transistor Q1 is electrically connected to the external power supply VD2. The second terminal of the first transistor Q1 is electrically connected to the output terminal of the first amplifier U1 in sequence through a resistor and a capacitor. The second terminal of the first transistor Q1 is electrically connected to the frequency selective amplifier circuit 60 through a resistor.

[0038] Specifically, the external power supply VD2 is electrically connected to the first terminal of the first transistor Q1 and the power supply terminal of the first amplifier U1, and the external power supply VD2 supplies power to the first amplifier U1. The non-inverting input terminal of the first amplifier U1 receives a voltage signal, such as a 5V DC voltage signal, transmitted from the voltage reference circuit 10. This voltage signal is amplified by the first amplifier U1 and transmitted from the output terminal of the first amplifier U1 to the gate of the first transistor Q1, turning on the first transistor Q1. The first terminal of the first transistor Q1 receives a voltage signal, such as a 12V DC voltage signal, transmitted from the external power supply VD2. The second terminal of the first transistor Q1 serves as the output terminal of the power supply circuit 20, outputting a voltage signal, such as a 10V DC voltage signal, to power the frequency selective amplifier circuit 60. The power supply circuit 20 provides a low-noise voltage signal to the frequency selective amplifier circuit 60 through the first amplifier U1, the first transistor Q1, and the resistors and capacitors connected to the first amplifier U1 and the first transistor Q1, ensuring reliable power supply.

[0039] In addition, such as Figure 4 As shown, the non-inverting input terminal of the first amplifier U1 is grounded through two parallel capacitors. The two parallel capacitors are the capacitors connecting the inverting input terminal and the non-inverting input terminal of the first amplifier U1. The output terminal of the first amplifier U1 is grounded in sequence through a capacitor (which is the capacitor connecting the second terminal of the first transistor Q1 to the output terminal of the first amplifier U1) and a resistor (which is the resistor connecting the inverting input terminal and the non-inverting input terminal of the first amplifier U1). The second terminal of the first transistor Q1 is electrically connected to the frequency selective amplifier circuit 60 through two parallel resistors.

[0040] Figure 5 This is a schematic diagram of an oscillation circuit provided in an embodiment of the present invention. (Reference) Figure 5Optionally, the oscillation circuit 30 includes a crystal Y, a second transistor Q2, and a varactor diode D. The first end of the crystal Y is electrically connected to the base of the second transistor Q2 through a capacitor. The first end of the crystal Y is also electrically connected to the output of the voltage reference circuit 10 through a capacitor and multiple resistors. The first terminal of the second transistor Q2 is electrically connected to the output of the voltage reference circuit 10 through a resistor and a capacitor. The second terminal of the second transistor Q2 is grounded through a resistor. The second end of the crystal Y is electrically connected to the negative terminal of the varactor diode D through a capacitor. The second end of the crystal Y is connected to an external voltage control signal VC and a compensation circuit 30 through a capacitor and a resistor. The positive terminal of the varactor diode D serves as the output of the oscillation circuit 30.

[0041] Specifically, the second terminal of crystal Y is connected to the external voltage control signal VC and the output terminal of voltage reference circuit 10 in sequence through a capacitor and a resistor. The cathode of varactor diode D is electrically connected to compensation circuit 30 through a resistor. Compensation circuit 40 outputs a second voltage signal V2 (adjustable) to the cathode of varactor diode D, so that compensation circuit 30 provides compensation voltage to the cathode of varactor diode D to adjust the frequency accuracy of oscillation signal S. The external voltage control signal VC (adjustable voltage) and the voltage signal output by voltage reference circuit 10, such as a 5V DC voltage signal, are transmitted to the second terminal of crystal Y. The voltage signal output by voltage reference circuit 10 is also transmitted to the first terminal of crystal Y. The switching on and off of the second transistor Q2 can adjust the voltage at the first terminal of crystal Y. Crystal Y oscillates to generate oscillation signal S, which is output through varactor diode D to provide an oscillation signal for frequency selective amplifier circuit.

[0042] In addition, such as Figure 5As shown, the positive terminal of the varactor diode D is grounded through a resistor. The output terminals of the external voltage control signal VC and the voltage reference circuit 10 are electrically connected to the second terminal of the crystal Y through two different resistors. The resistor connected to the external voltage control signal VC is grounded through a resistor and a capacitor in sequence. The resistor connected to the output terminal of the voltage reference circuit 10 is grounded through a capacitor (which is connected in parallel with a resistor). The second terminal of the crystal Y is electrically connected to the two different resistors mentioned above through two series capacitors and a resistor in sequence. The capacitor closest to the second terminal of the crystal Y in the series connection is connected in parallel with a capacitor. The first terminal and the second terminal of the crystal Y are connected in parallel with the first terminal and the second terminal. A resistor is connected between the two terminals. The first terminal of crystal Y is connected to the output terminal of voltage reference circuit 10 via a capacitor (the capacitor connected between the first terminal of crystal Y and the base of the second transistor Q2), three series resistors, and the first terminal of the second transistor Q2. The end of the three series resistors closest to the first terminal of crystal Y is grounded through a parallel resistor and a capacitor. The resistance between the first terminal of the second transistor Q2 and the output terminal of voltage reference circuit 10 is the resistance furthest from the first terminal of crystal Y among the three series resistors. The first terminal of the second transistor Q2 is connected to the output terminal of voltage reference circuit 10 via two capacitors. The capacitor connected to the base of the second transistor Q2 is connected to the second terminal of the second transistor Q2 via a capacitor (the end of which is grounded through a capacitor), an inductor, and a capacitor (which is connected in parallel with another capacitor). The second terminal of the second transistor Q2 is grounded through two parallel resistors. The end of the resistor connected to the second terminal of the second transistor Q2 is connected between the two capacitors connected to the first terminal of the second transistor Q2.

[0043] Figure 6 This is a schematic diagram of a heating control circuit provided in an embodiment of the present invention. (Reference) Figure 6Optionally, the heating control circuit 50 includes a thermistor RT, a second amplifier U2, a third amplifier U3, a second MOSFET M2, and a third MOSFET M3. The non-inverting input of the second amplifier U2 is electrically connected to the output of the compensation circuit 40 and the voltage reference circuit 10. The inverting input of the second amplifier U2 is electrically connected to the first terminal of the thermistor RT through a resistor. The second terminal of the thermistor RT is grounded. The first terminal of the thermistor RT is electrically connected to the output of the voltage reference circuit 10 through a resistor. The output of the second amplifier U2 is electrically connected to the non-inverting input of the third amplifier U3 through a resistor. The non-inverting input of the third amplifier U3 is electrically connected to the external power supply VD2 through a resistor. The inverting input of the third amplifier U3 is electrically connected to the voltage reference circuit 10 through a resistor. The output of the third amplifier U3 is electrically connected to the gate of the second MOSFET M2 and the gate of the third MOSFET M3 through a resistor. The first terminals of the second MOSFET M2 and the third MOSFET M3 are electrically connected to the external power supply VD2. The second terminals of the second MOSFET M2 and the third MOSFET M3 are grounded.

[0044] For example, the voltage of the external power supply VD2 is 12V DC, and the voltage signal output from the output terminal of the voltage reference circuit 10 is 5V DC. Specifically, the compensation circuit 40 outputs a first voltage signal V1 (adjustable) to the non-inverting input terminal of the second amplifier U2. When the temperature of the thermistor RT changes, the voltage at the inverting input terminal of the second amplifier U2 changes, thereby adjusting the output voltage of the second amplifier U2, which in turn adjusts the non-inverting input voltage of the third amplifier U3, thereby adjusting the output voltage of the third amplifier U3. This, in turn, adjusts the base voltage of the second MOSFET M2 and the base voltage of the third MOSFET M3, thereby adjusting the on / off time of the second MOSFET M2 and the third MOSFET M3, and thus adjusting the heating power of the second MOSFET M2 and the third MOSFET M3 to control the temperature of the oscillation circuit 30.

[0045] In addition, the non-inverting input of the second amplifier U2 is electrically connected to the outputs of the compensation circuit 40 and the voltage reference circuit 10 through two resistors. The non-inverting input of the second amplifier U2 is grounded through a resistor. The output of the second amplifier U2 is electrically connected to the inverting input of the second amplifier U2 through a capacitor (which has a parallel branch containing a capacitor and two resistors connected in series). The output of the third amplifier U3 is electrically connected to the inverting input of the third amplifier U3 through a capacitor (the end of which is away from the output of the third amplifier U3 is electrically connected to the first terminal of the third MOSFET M3 through a resistor). The first terminals of the second MOSFET M2 and the third MOSFET M3 are electrically connected to the external power supply VD2 through different resistors. The power supply terminal of the second amplifier U2 is electrically connected to the output of the voltage reference circuit 10. The power supply terminal of the third amplifier U3 is electrically connected to the external power supply VD2 through a resistor (the end of which is close to the power supply terminal of the third amplifier U3 is grounded through a capacitor, and the end of which is away from the power supply terminal of the third amplifier U3 is grounded through two parallel capacitors).

[0046] Optionally, the thermistor, the second MOSFET, and the third MOSFET are located near the oscillation circuit 30.

[0047] Specifically, the thermistor, the second MOSFET, and the third MOSFET are located on at least one side of the crystal in the oscillation circuit 30, so that the temperature difference between the thermistor and the crystal is within a preset range, ensuring that the temperature of the thermistor can represent the temperature of the crystal. Thus, the heating power of the second MOSFET and the third MOSFET are adjusted by the temperature of the thermistor to ensure that the temperature of the crystal is within the preset range and that the temperature of the crystal meets the actual requirements.

[0048] Figure 7 This is a schematic diagram of a compensation circuit provided in an embodiment of the present invention. (Reference) Figure 7 Optionally, the compensation circuit 40 includes a digital potentiometer U5 and a resistor. The power supply terminal of the digital potentiometer U5 is electrically connected to the output terminal of the voltage reference circuit 10. The first output terminal of the digital potentiometer U5 is electrically connected to the heating control circuit 50. The second output terminal of the digital potentiometer U5 is electrically connected to the oscillation circuit 30 through the resistor.

[0049] Specifically, the output of the voltage reference circuit 10 outputs a voltage signal, such as a 5V DC voltage signal, to power the digital potentiometer U5. The first output of the digital potentiometer U5 outputs a first voltage signal V1 (adjustable) to the heating control circuit 50 to compensate for the input voltage of the heating control circuit 50. The second output of the digital potentiometer U5 outputs a second voltage signal V2 (adjustable) to the oscillation circuit 30 to compensate for the input voltage of the oscillation circuit 30. Further, the first voltage signal output from the first output of the digital potentiometer U5 and the second voltage signal output from the second output of the digital potentiometer U5 are achieved by adjusting the resistor. Specifically, the digital potentiometer U5 uses digital signals to achieve programmable resistance adjustment, realizing precise, stable, and automatically controllable resistance adjustment. The core structure of the digital potentiometer U5 consists of a resistor array (composed of multiple precision fixed resistors connected in series; for example, the total resistance of the resistor array is 1kΩ~1MΩ, such as 10kΩ or 100kΩ) and an electronic switch matrix (composed of MOS transistors or CMOS switches). The conduction state of the switches is selected through digital control signals, thereby changing the total resistance value.

[0050] Furthermore, the resistor array of the digital potentiometer U5 typically consists of tens to hundreds of precision resistors of equal resistance connected in series, forming a resistor chain with a fixed total resistance. The two ends of this resistor chain correspond to the two ends of a traditional potentiometer. An electronic switch is connected in parallel at each resistor connection point (node), and the common terminal of all switches serves as a tap, corresponding to the sliding terminal of a traditional potentiometer. External digital signals (such as commands, clock signals, and data) select a switch to conduct via internal control circuitry (such as a shift register or decoding circuitry), connecting the tap to the corresponding node and thus changing the resistance value between the two ends of the resistor chain and the common terminal of the switch. Additionally, the digital potentiometer can have built-in non-volatile memory to save the current resistance setting, automatically restoring the previous adjustment state upon power-up after a power outage, eliminating the need for reconfiguration.

[0051] Figure 8 This is a schematic diagram of a crystal oscillator provided in an embodiment of the present invention. (Reference) Figure 8Optionally, the crystal oscillator also includes a housing 70, a base 80, a first circuit board 81, and a second circuit board 82. The first circuit board 81 and the second circuit board 82 are located on the base 80 and inside the housing 70. The power supply circuit 20 and the frequency selective amplifier circuit 60 are located on the first circuit board 81, and the voltage reference circuit 10, the compensation circuit 40, the oscillation circuit 30, and the heating control circuit 50 are located on the second circuit board 82. Specifically, the pins 83 of the base 80 are soldered through the fixing holes of the first circuit board 81, the crystal Y is soldered to the second circuit board 82, and the fixing holes of the second circuit board 82 are soldered through the pins 83 of the base 80. The base 80 is placed into the housing groove for soldering and sealing. The housing 70 protects the internal circuitry, and the base 80 supports the first circuit board 81 and the second circuit board 82. The arrangement of two circuit boards solves the problem that the overall volume of each circuit is too large to be integrated into a single circuit board.

[0052] The crystal oscillator provided in this embodiment includes: a voltage reference circuit, a power supply circuit, an oscillation circuit, a compensation circuit, a heating control circuit, and a frequency selective amplifier circuit. The voltage reference circuit is electrically connected to the power supply circuit, the oscillation circuit, the compensation circuit, and the heating control circuit. The heating control circuit is located close to the oscillation circuit. The power supply circuit is electrically connected to the frequency selective amplifier circuit. The compensation circuit is electrically connected to the heating control circuit and the oscillation circuit. The oscillation circuit is electrically connected to the frequency selective amplifier circuit. Both the frequency selective amplifier circuit and the power supply circuit are equipped with transistors. The voltage reference circuit and the power supply circuit provide stable voltages of varying magnitudes. The oscillation circuit generates an oscillation signal. The compensation circuit compensates for the oscillation signal. The heating control circuit controls the heating of the oscillation circuit. The frequency selective amplifier circuit amplifies and outputs the oscillation signal using selective frequency amplification. The frequency selective amplifier circuit includes a first frequency selective amplifier module and a second frequency selective amplifier module, both having identical structures. The crystal oscillator provided in this embodiment compensates for the oscillation signal generated by the oscillation circuit through a compensation circuit to ensure the stability of the frequency accuracy of the oscillation signal. Furthermore, both the frequency selective amplifier circuit and the power supply circuit are equipped with transistors to ensure the effect of frequency selective amplification and power supply stability, thereby guaranteeing the ultra-low short-term stability index of the crystal oscillator and the stability of the frequency accuracy of the oscillation signal. The ultra-low short-term stability index can reach the order of 1.5E-13. Ultra-low short-term stability can reduce phase noise and ensure phase noise performance. The crystal oscillator provided in this embodiment can achieve ultra-low short-term stability and isothermal operation. This ultra-low short-term stable isothermal crystal oscillator can provide extremely high frequency output stability over long periods and can provide high frequency accuracy, meeting the needs of various application scenarios such as communication systems, radar systems, navigation systems, time synchronization systems, and electronic measuring instruments. It can also maintain stable performance even in harsh environments.

[0053] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, rearrangements, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A crystal oscillator, characterized in that, include: Voltage reference circuit, power supply circuit, oscillation circuit, compensation circuit, heating control circuit, and frequency selective amplifier circuit; The voltage reference circuit is electrically connected to the power supply circuit, the oscillation circuit, the compensation circuit, and the heating control circuit. The heating control circuit is located close to the oscillation circuit. The power supply circuit is electrically connected to the frequency selective amplifier circuit. The compensation circuit is electrically connected to the heating control circuit and the oscillation circuit. The oscillation circuit is electrically connected to the frequency selective amplifier circuit. Both the frequency selective amplifier circuit and the power supply circuit are equipped with transistors. The voltage reference circuit and the power supply circuit are used to provide stable voltages of different magnitudes. The oscillation circuit is used to generate an oscillation signal. The compensation circuit is used to compensate the oscillation signal. The heating control circuit is used to control the heating of the oscillation circuit. The frequency selective amplifier circuit is used to selectively amplify the oscillation signal and output it.

2. The crystal oscillator according to claim 1, characterized in that, The frequency selective amplifier circuit includes a first frequency selective amplifier module and a second frequency selective amplifier module. The first frequency selective amplifier module and the second frequency selective amplifier module have the same structure. The input terminal of the first frequency selective amplifier module is electrically connected to the output terminal of the oscillation circuit, and the output terminal of the first frequency selective amplifier module is electrically connected to the input terminal of the second frequency selective amplifier module. The output terminal of the second frequency selective amplifier module serves as the output terminal of the frequency selective amplifier circuit.

3. The crystal oscillator according to claim 2, characterized in that, The first frequency selective amplifier module includes a first inductor, a second inductor, a third inductor, and a first MOSFET. The first end of the first inductor is electrically connected to the output terminal of the oscillation circuit through a capacitor. The first end of the first inductor is electrically connected to the first terminal of the first MOSFET. The second end of the first inductor is electrically connected to the gate of the first MOSFET through a resistor. The second end of the first inductor is grounded through the resistor. The second terminal of the first MOSFET is electrically connected to the first end of the second inductor through a resistor. The first end of the second inductor is grounded through a capacitor. The second end of the second inductor is electrically connected to the power supply circuit through the third inductor. The second end of the second inductor serves as the output terminal of the first frequency selective amplifier module.

4. The crystal oscillator according to claim 1, characterized in that, The voltage reference circuit includes a voltage reference, a resistor, and multiple parallel capacitors. The power supply terminal of the voltage reference is electrically connected to an external power supply through the resistor. The output terminal of the voltage reference serves as the output terminal of the voltage reference circuit, and the output terminal of the voltage reference is grounded through the multiple parallel capacitors.

5. The crystal oscillator according to claim 1, characterized in that, The power supply circuit is a low-noise power supply circuit, which includes a first amplifier and a first transistor. The non-inverting input terminal of the first amplifier is electrically connected to the output terminal of the voltage reference circuit through a resistor. The non-inverting input terminal of the first amplifier is grounded through a capacitor. The inverting input terminal of the first amplifier is electrically connected to the non-inverting input terminal of the first amplifier in sequence through a resistor and a capacitor. The output terminal of the first amplifier is electrically connected to the base of the first transistor. The first terminal of the first transistor is electrically connected to an external power supply. The second terminal of the first transistor is electrically connected to the output terminal of the first amplifier in sequence through a resistor and a capacitor. The second terminal of the first transistor is electrically connected to the frequency selective amplifier circuit through a resistor.

6. The crystal oscillator according to claim 1, characterized in that, The oscillation circuit includes a crystal, a second transistor, and a varactor diode. The first terminal of the crystal is electrically connected to the base of the second transistor through a capacitor. The first terminal of the crystal is also electrically connected to the output terminal of the voltage reference circuit through the capacitor and multiple resistors. The first terminal of the second transistor is electrically connected to the output terminal of the voltage reference circuit through a resistor and a capacitor. The second terminal of the second transistor is grounded through a resistor. The second terminal of the crystal is electrically connected to the negative terminal of the varactor diode through a capacitor. The second terminal of the crystal is connected to an external voltage control signal and the compensation circuit through a capacitor and a resistor. The positive terminal of the varactor diode serves as the output terminal of the oscillation circuit.

7. The crystal oscillator according to claim 1, characterized in that, The heating control circuit includes a thermistor, a second amplifier, a third amplifier, a second MOSFET, and a third MOSFET. The non-inverting input of the second amplifier is electrically connected to the output of the compensation circuit and the voltage reference circuit. The inverting input of the second amplifier is electrically connected to the first terminal of the thermistor through a resistor. The second terminal of the thermistor is grounded. The first terminal of the thermistor is electrically connected to the output of the voltage reference circuit through a resistor. The output of the second amplifier is electrically connected to the non-inverting input of the third amplifier through a resistor. The non-inverting input of the third amplifier is electrically connected to an external power supply through a resistor. The inverting input of the third amplifier is electrically connected to the voltage reference circuit through a resistor. The output of the third amplifier is electrically connected to the gates of the second and third MOSFETs through a resistor. The first terminals of the second and third MOSFETs are electrically connected to the external power supply. The second terminals of the second and third MOSFETs are grounded.

8. The crystal oscillator according to claim 7, characterized in that, The thermistor, the second MOS transistor, and the third MOS transistor are located near the oscillation circuit.

9. The crystal oscillator according to claim 1, characterized in that, The compensation circuit includes a digital potentiometer and a resistor. The power supply terminal of the digital potentiometer is electrically connected to the output terminal of the voltage reference circuit. The first output terminal of the digital potentiometer is electrically connected to the heating control circuit. The second output terminal of the digital potentiometer is electrically connected to the oscillation circuit through the resistor.

10. The crystal oscillator according to claim 1, characterized in that, It also includes a housing, a base, a first circuit board and a second circuit board, the first circuit board and the second circuit board being located on the base and inside the housing, the power supply circuit and the frequency selective amplifier circuit being located on the first circuit board, and the voltage reference circuit, the compensation circuit, the oscillation circuit and the heating control circuit being located on the second circuit board.

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