A crystal oscillator suitable for space application engineering

Abstract

The utility model belongs to the field of space application technology, specifically a crystal oscillator suitable for space application engineering. By using quartz crystals in parallel and adopting LCπ-type spread spectrum circuit, the coating area is expanded in disguise, the crystal frequency pulling amount is increased, the crystal frequency modulation sensitivity is increased, and it is helpful to expand the voltage control adjustment range; reduce phase noise, and have good anti-interference ability and transmission characteristics. The crystal oscillator has an output frequency of up to 300MHz, works stably in a wide operating temperature range (-55℃~85℃), the voltage control adjustment range is ≥±30ppm, the noise is low, and the voltage control linearity can be better than 5%, which meets the technical requirements of high-frequency local oscillator VCXO in the field of space application engineering with ultra-large range voltage control and low level phase noise, and is suitable for promotion and use in aerospace technology space communication projects.

Description

Technical Field

[0001] The utility model belongs to the technical field of space application, and specifically discloses a crystal oscillator suitable for space application engineering. Background Art

[0002] With the rapid development of modern space technology, high-frequency VCXO (voltage-controlled crystal oscillator) is more and more widely used, and the requirements for high-frequency VCXO such as large voltage control, low noise, low power consumption, small size, and high reliability are becoming more and more stringent. Therefore, through the research on quartz crystal resonators and voltage-controlled crystal oscillators, it is necessary to provide the possibility to improve various indicators and meet various usage requirements.

[0003] For space applications, more stringent requirements are put forward in terms of volume compression, index optimization and reliability. As the frequency of space communication becomes higher and higher, high-frequency VCXOs need higher spectrum purity and lower noise in space communication applications such as Ethernet and Starlink, requiring the crystal oscillator local oscillator frequency to continue to increase. Therefore, this utility model mainly focuses on the research of low phase noise VCXO with high-frequency local oscillation of 100M~300M.

[0004] At present, many manufacturers have matured in the application of small-volume crystal oscillators, with different sizes; however, the technical indicators of crystal oscillators are difficult to improve due to the influence of raw materials and crystal size. The local oscillator frequency of the currently known crystal resonator can reach up to 300MHz, and the frequency above 300MHz is basically achieved by the circuit frequency doubling function. However, due to the limitations of existing mature processes, the smaller the size of the crystal resonator, the smaller the frequency pulling amount that its performance parameters can achieve. How to improve the frequency pulling amount of quartz crystals under existing process conditions, realize ultra-large range voltage control of high-frequency local oscillator VCXO, and have a lower level of phase noise, is a problem that technical personnel in this field need to solve. Utility Model Content

[0005] In order to solve the technical problems listed in the background technology, the utility model provides a crystal oscillator suitable for space application engineering. The specific technical solution is as follows:

[0006] A crystal oscillator suitable for space application engineering comprises a voltage control circuit, a crystal oscillation circuit and an output circuit connected in series in sequence. The crystal part of the crystal oscillation circuit is formed by two quartz crystals of the same type connected in parallel; the voltage control circuit is formed by an input voltage regulation circuit and an LCπ-type spread spectrum circuit connected in series.

[0007] The same type of quartz crystals are used in parallel to expand the coating area, increase the crystal frequency pulling capacity, increase the crystal's frequency modulation sensitivity, and help expand the voltage control adjustment range; the LCπ-type spread spectrum circuit is used to obtain good voltage control linearity, reduce phase noise, and further expand the frequency range.

[0008] Preferably, the output circuit is a thick film circuit, comprising a differential output circuit chip and a chip capacitor which are electrically connected as one, and the XT end of the differential output circuit chip is electrically connected to a crystal oscillator circuit.

[0009] Preferably, the total radiation dose of the differential output circuit chip is ≥100 krad (Si), and the single-particle effect resistance is ≥75 MeV·cm 2 / mg.

[0010] The differential output circuit chip is used to receive the high-frequency signal output by the dual crystal oscillator circuit. In a complex high-speed communication environment, it adopts a low load impedance and bidirectional reverse design, which has a strong suppression effect on noise and can obtain good anti-interference ability and transmission characteristics.

[0011] Preferably, the crystal oscillator circuit is a capacitor three-point oscillator circuit, and the quartz crystal is located in the feedback network as an inductor element of the oscillation loop and participates in the oscillation together with other elements.

[0012] Preferably, each of the quartz crystals has a frequency of 200 MHz and is packaged using an SMD3225 chip.

[0013] Preferably, the same model means that the static capacitance C0, dynamic capacitance C1, quality factor Q, and resonant resistance R in the equivalent circuit of the two quartz crystals are the same.

[0014] Compared with the prior art, the utility model has the following advantages:

[0015] The utility model provides a crystal oscillator suitable for space application engineering, which uses quartz crystals in parallel and adopts an LCπ-type spread spectrum circuit, thereby expanding the coating area in disguise, increasing the crystal frequency pulling amount, increasing the crystal's frequency modulation sensitivity, and helping to expand the voltage control amount adjustment range; reducing phase noise, and having good anti-interference ability and transmission characteristics.

[0016] The crystal oscillator has an output frequency of up to 300MHz, operates stably in a wide operating temperature range (-55℃~85℃), has a voltage control adjustment range of ≥±30ppm, low noise, and a voltage control linearity better than 5%, meeting the technical requirements of high-frequency local oscillator VCXO with ultra-wide voltage control and low phase noise in the field of space application engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the basic functional structure of the circuit in the embodiment of the utility model;

[0018] Figure 2 This is a schematic diagram of a dual crystal oscillator circuit in an embodiment of the utility model;

[0019] Figure 3 This is the equivalent circuit diagram of the quartz crystal in the embodiment of the utility model;

[0020] Figure 4 This is a LC π-type spread spectrum circuit diagram in an embodiment of the utility model;

[0021] Figure 5 This is a schematic diagram of the output circuit in the embodiment of the utility model. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the utility model clearer, the utility model is described below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on this embodiment, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0023] refer to Figure 1 This embodiment provides a crystal oscillator suitable for space application engineering, including a dual quartz crystal oscillation circuit, a voltage control circuit and an output circuit.

[0024] The dual quartz crystal oscillator circuit includes crystal 1, crystal 2 and an oscillator circuit; crystal 1 and crystal 2 have the same parameters, including static capacitance C0, dynamic capacitance C1, quality factor Q, and resonant resistance R in the crystal equivalent circuit. Crystal 1 and crystal 2 are connected in parallel and used to form a dual crystal oscillator circuit (see Figure 2 ); the output signal of the oscillation circuit is the local oscillation frequency signal output. The parameters of the selected crystal 1 and crystal 2 can be made the same by crystal parameter testing and special dual crystal test tooling. The parallel connection of crystal 1 and crystal 2 is equivalent to expanding the wafer coating area, increasing the frequency modulation sensitivity of the crystal, and helping to expand the voltage control adjustment range. Because the crystal (quartz crystal equivalent circuit see Figure 3 ) is inductive and can be regarded as a crystal parallel inductor frequency spread. The original series resonant frequency remains unchanged, and its parallel resonant frequency moves up, expanding the adjustable frequency range. When crystal 1 and crystal 2 are connected in parallel, the equivalent resistance is reduced compared to a single crystal, and the oscillation circuit is easier to start and the oscillation is more stable, thereby more effectively suppressing parasitic oscillation and self-excited oscillation, greatly improving the stability of the oscillation circuit.

[0025] The voltage control circuit includes a variable capacitance diode D, a voltage control input resistor R2 and an LC π-type spread spectrum circuit (the π-type spread spectrum circuit composed of L2, C2 and C3, see Figure 4). The output end of the voltage control circuit is electrically connected to the input end of the dual crystal oscillator circuit; the principle of the voltage control circuit is to use the principle of adjusting the voltage across the varactor diode to change its capacitance to achieve the purpose of controlling the output frequency by voltage. The LCπ-type spread spectrum circuit can expand the frequency range, obtain good voltage control linearity and a larger voltage control adjustment range, and achieve the parameter control requirements of large voltage control.

[0026] The output circuit is a thick film circuit. The XT end of the thick film circuit is connected to the dual crystal oscillator circuit; the thick film circuit consists of an LVPECL differential output circuit chip and chip capacitors (see Figure 5 ); the thick film circuit package is independently designed and developed; the total radiation dose of the LVPECL differential output circuit integrated circuit chip is ≥100krad(Si), and the single particle effect resistance is ≥75MeV·cm2 / mg; the LVPECL differential output circuit is used to receive the high-frequency signal output by the dual crystal oscillation circuit. In a complex high-speed communication environment, it adopts a low load impedance and bidirectional reverse design, which has a strong suppression effect on noise and can obtain good anti-interference ability and transmission characteristics.

[0027] The scheme described has the following advantages: the output frequency can reach up to 300MHz, it works stably in a wide operating temperature range (-55℃~85℃), the voltage control adjustment range is ≥±30ppm, the noise is low, and the voltage control linearity can be better than 5%.

[0028] Finally, it should be noted that the above description is only a preferred embodiment of the utility model and is not intended to limit the utility model. Although the utility model is described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions recorded in the above embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model shall be included in the protection scope of the utility model.

Claims

1. A crystal oscillator suitable for space application engineering, comprising a voltage control circuit, a crystal oscillator circuit, and an output circuit connected in series, characterized in that: The crystal part of the crystal oscillator circuit is formed by connecting two quartz crystals of the same type in parallel; the voltage control circuit is formed by connecting an input voltage regulating circuit and an LC π-type spread spectrum circuit in series.

2. A crystal oscillator suitable for space application engineering as claimed in claim 1, characterized in that: The output circuit is a thick film circuit, comprising a differential output circuit chip and a chip capacitor which are electrically connected as one body, and the XT end of the differential output circuit chip is electrically connected to a crystal oscillator circuit.

3. A crystal oscillator suitable for space application engineering as claimed in claim 2, characterized in that: The total radiation dose of the differential output circuit chip is ≥100krad(Si), and the single particle effect resistance is ≥75MeV·cm 2 / mg.

4. A crystal oscillator suitable for space application engineering as claimed in claim 3, characterized in that: The crystal oscillator circuit is a capacitor three-point oscillator circuit. The quartz crystal is located in the feedback network and acts as an inductor element of the oscillation loop, participating in the oscillation together with other elements.

5. A crystal oscillator suitable for space application engineering as claimed in claim 4, characterized in that: Each of the quartz crystals has a frequency of 200 MHz and is packaged using a SMD3225 chip.

6. A crystal oscillator suitable for space application engineering as claimed in claim 5, characterized in that: The same model refers to that the static capacitance C0, dynamic capacitance C1, quality factor Q, and resonant resistance R in the equivalent circuit of the two quartz crystals are the same.

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