阅读说明：本技术 星载原子钟的下变频信号处理方法和变频组件 (Down-conversion signal processing method and down-conversion assembly of satellite-borne atomic clock ) 是由 赵广东 吴晟 刘杰 黄奕 郑荣磊 闵康磊 谢晔 李思衡 董硕 方轶 于 2020-04-21 设计创作，主要内容包括：本发明提供了一种星载原子钟的下变频信号处理方法和变频组件,该方法包括：包括：接收星载氢原子钟物理系统输出的调幅信号；对所述调幅信号进行隔离,得到预设带宽的第一信号；对所述第一信号进行放大、滤波处理之后,与声表面波振荡器输出的振荡信号进行混频,得到混频信号；对所述混频信号进行放大处理,得到预设增益和预设频率的载波信号。从而可以将星载氢原子钟物理系统输出的L波段信号转换至较低的频段,且有效降低下变频过程中引入的噪声干扰,提高载波信号的质量。(The invention provides a down-conversion signal processing method and a frequency conversion component of a satellite-borne atomic clock, wherein the method comprises the following steps: the method comprises the following steps: receiving an amplitude modulation signal output by a physical system of the satellite-borne hydrogen atomic clock; isolating the amplitude-modulated signal to obtain a first signal with a preset bandwidth; amplifying and filtering the first signal, and mixing the first signal with an oscillation signal output by a surface acoustic wave oscillator to obtain a mixing signal; and amplifying the mixing signal to obtain a carrier signal with preset gain and preset frequency. Therefore, the L-band signal output by the satellite-borne hydrogen atomic clock physical system can be converted to a lower frequency band, noise interference introduced in the down-conversion process is effectively reduced, and the quality of the carrier signal is improved.)

1. A down-conversion signal processing method of a satellite-borne atomic clock is characterized by comprising the following steps:

receiving an amplitude modulation signal output by a physical system of the satellite-borne hydrogen atomic clock;

carrying out reverse isolation on the amplitude-modulated signal to obtain a first signal with a preset bandwidth;

amplifying and filtering the first signal, and mixing the first signal with an oscillation signal output by a surface acoustic wave oscillator to obtain a mixing signal;

and amplifying the mixing signal to obtain a carrier signal with preset gain and preset frequency.

2. The method for processing the down-conversion signal of the atomic clock on the satellite according to claim 1, wherein the amplitude modulation signal comprises: error information of the microwave cavity and the crystal oscillator; the frequency range of the center frequency point of the amplitude modulation signal output by the satellite-borne hydrogen atomic clock physical system comprises: 1420.405 MHz. + -. 1.75 MHz.

3. The method for processing the down-conversion signal of the atomic clock on the satellite according to claim 1, wherein the step of performing reverse isolation on the amplitude-modulated signal to obtain a first signal with a preset bandwidth comprises:

and reversely isolating the amplitude-modulated signal in a receiving channel of the amplitude-modulated signal through a ferrite isolator connected in series to obtain a first signal with a preset bandwidth.

4. The method for processing the down-conversion signal of the atomic clock on the satellite according to claim 1, wherein the amplifying and filtering the first signal comprises:

and the first signal passes through a first amplifier, a filter, a first adjustable attenuation network and a second amplifier in sequence to obtain a filtering signal subjected to two-stage amplification.

5. The method for processing the down-conversion signal of the atomic clock on the satellite according to claim 1, wherein the step of amplifying the mixing signal to obtain a carrier signal with a preset gain and a preset frequency comprises:

and sequentially passing the mixing signal through a second adjustable attenuation network, a first intermediate frequency amplifier, a third adjustable attenuation network and a second intermediate frequency amplifier to obtain a carrier signal which is subjected to two-stage amplification and accords with a preset gain and a preset frequency.

6. A frequency conversion assembly of a satellite-borne atomic clock, which is applied to the method of any one of the preceding claims 1 to 5, and comprises an L-shaped housing, wherein: the device comprises an input interface, an isolator, a first amplification link, a surface acoustic wave oscillator, a second amplification link and an output interface; wherein:

the input interface is used for receiving an amplitude modulation signal output by a physical system of the satellite-borne hydrogen atomic clock;

the isolator is used for carrying out reverse isolation on the amplitude modulation signal to obtain a first signal with a preset bandwidth;

the first amplification link is used for amplifying and filtering the first signal;

the surface acoustic wave oscillator is used for generating a local oscillation signal;

the second amplification link is used for amplifying and filtering the first signal, and then amplifying a mixing signal obtained by mixing the first signal with a local oscillation signal to obtain a carrier signal with a preset gain and a preset frequency;

and the output interface is used for transmitting the carrier signal to an external detection circuit.

7. The frequency conversion assembly of a space-borne atomic clock according to claim 6, characterized in that said amplitude modulated signal comprises: error information of the microwave cavity and the crystal oscillator; the frequency range of the center frequency point of the amplitude modulation signal output by the satellite-borne hydrogen atomic clock physical system comprises: 1420.405 MHz. + -. 1.75 MHz.

8. The variable frequency component of the atomic clock on board a satellite of claim 6, wherein the first amplification link comprises: the device comprises a first amplifier, a filter, a first adjustable attenuation network and a second amplifier which are sequentially connected in series.

9. The variable frequency component of the atomic clock on board a satellite of claim 6, wherein the second amplification chain comprises: the second adjustable attenuation network, the first intermediate frequency amplifier, the third adjustable attenuation network and the second intermediate frequency amplifier are sequentially connected in series.

10. The frequency conversion assembly of the atomic clock on board according to any one of claims 6 to 9, wherein the microstrip plates on both sides of the L-shaped housing are grounded, and a separate shielding cavity is formed inside the L-shaped housing.

Technical Field

The invention relates to the technical field of microwaves, in particular to a down-conversion signal processing method and a down-conversion component of a satellite-borne atomic clock.

Background

Currently, the Global satellite navigation System includes a Global Positioning System (GPS), a russian GLONASS navigation System, a european galileo navigation System, and a chinese beidou navigation System. Radio signals (carrying satellite time and position) transmitted by a satellite on the day reach the ground over a distance of 2 to 3 kilometers and are received by a ground terminal. Then, by extracting the satellite signal time and differencing it from the local time, the propagation time of the signal can be obtained. The distance between the satellite and the ground can be obtained by multiplying the propagation time by the light velocity. Because the light speed is very high, the precision of time measurement is required to be very high for accurate positioning, for example, when the time measurement error is 10 nanoseconds, the corresponding spatial distance error reaches 3 meters. The requirement for positioning in daily activities is basically about several meters, which requires that the satellites in space have good time keeping capability, and the time difference between each satellite needs to be kept within several nanoseconds.

The beidou global system space segment includes 30 networked satellites, of which 24 Medium Earth Orbit (MEO) satellites, 3 geostationary Orbit (GEO) satellites and 3 Inclined Geosynchronous Orbit (IGSO) satellites. The Beidou global system mainly provides services such as positioning, navigation, speed measurement, time service, communication and the like for various global users. According to the global system overall design requirement, the Beidou global system accuracy index is an operation management mode of updating the full constellation ephemeris once according to 1 hour, and the index is UERE 0.6 m. Meanwhile, under the working mode that inter-satellite link support is considered, the Beidou global system sets the adjustment interval to be not less than 200 days, so that the frequency accuracy of the satellite-borne clock is required to be 2E-11, the second stability is required to be 3E-12, the ten thousand second stability is required to be 3.3E-14, the day stability is required to be 1.2E-14, and the frequency drift rate is required to be 5.8E-13/day.

The down-conversion component is positioned at the rear-stage output of a physical system of the satellite-borne hydrogen atomic clock, and is used for moving the microwave signal frequency spectrum which is oscillated from the physical microwave cavity and has crystal oscillation and microwave cavity error information to the intermediate-frequency part for processing by a rear-stage detection circuit. The down-conversion component controls the influence of noise generated by the down-conversion component on a signal path in the process of frequency conversion, and the phase jitter caused by the down-conversion component is controlled to be as low as possible.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a down-conversion signal processing method and a down-conversion component of a satellite-borne atomic clock.

In a first aspect, the present invention provides a down-conversion signal processing method for a satellite-borne atomic clock, including:

receiving an amplitude modulation signal output by a physical system of the satellite-borne hydrogen atomic clock;

carrying out reverse isolation on the amplitude-modulated signal to obtain a first signal with a preset bandwidth;

amplifying and filtering the first signal, and mixing the first signal with a local oscillation signal output by a surface acoustic wave oscillator to obtain a mixing signal;

and amplifying the mixing signal to obtain a carrier signal with preset gain and preset frequency.

Optionally, the amplitude modulated signal comprises: error information of the microwave cavity and the crystal oscillator; the frequency range of the center frequency point of the amplitude modulation signal output by the satellite-borne hydrogen atomic clock physical system comprises: 1420.405 MHz. + -. 1.75 MHz.

Optionally, the performing reverse isolation on the amplitude-modulated signal to obtain a first signal with a preset bandwidth includes:

and filtering the amplitude-modulated signal in a receiving channel of the amplitude-modulated signal through a ferrite isolator connected in series to obtain a first signal with a preset bandwidth.

Optionally, the amplifying and filtering the first signal includes:

and the first signal passes through a first amplifier, a filter, a first adjustable attenuation network and a second amplifier in sequence to obtain a filtering signal subjected to two-stage amplification.

Optionally, the amplifying the mixing signal to obtain a carrier signal with a preset gain and a preset frequency includes:

and sequentially passing the mixing signal through a second adjustable attenuation network, a first intermediate frequency amplifier, a third adjustable attenuation network and a second intermediate frequency amplifier to obtain a carrier signal which is subjected to two-stage amplification and accords with a preset gain and a preset frequency.

In a second aspect, the present invention provides a frequency conversion assembly of a satellite-borne atomic clock, which is applied to the method of any one of the first aspect, wherein the frequency conversion assembly comprises an L-shaped housing, and the L-shaped housing is internally provided with: the device comprises an input interface, an isolator, a first amplification link, a surface acoustic wave oscillator, a second amplification link and an output interface; wherein:

the input interface is used for receiving an amplitude modulation signal output by a physical system of the satellite-borne hydrogen atomic clock;

the isolator is used for carrying out reverse isolation on the amplitude modulation signal to obtain a first signal with a preset bandwidth;

the first amplification link is used for amplifying and filtering the first signal;

the surface acoustic wave oscillator is used for generating a local oscillation signal;

the second amplification link is used for amplifying and filtering the first signal, and then amplifying a mixing signal obtained by mixing the first signal with an oscillation signal to obtain a carrier signal with a preset gain and a preset frequency;

and the output interface is used for transmitting the carrier signal to an external detection circuit.

Optionally, the amplitude modulated signal comprises: error information of the microwave cavity and the crystal oscillator; the frequency range of the center frequency point of the amplitude modulation signal output by the satellite-borne hydrogen atomic clock physical system comprises: 1420.405 MHz. + -. 1.75 MHz.

Optionally, the first amplifying link includes: the device comprises a first amplifier, a filter, a first adjustable attenuation network and a second amplifier which are sequentially connected in series.

Optionally, the second amplification chain comprises: the second adjustable attenuation network, the first intermediate frequency amplifier, the third adjustable attenuation network and the second intermediate frequency amplifier are sequentially connected in series.

Optionally, the microstrip plates on both sides of the L-shaped housing are grounded, and a separate shielding cavity is formed inside the L-shaped housing.

Compared with the prior art, the invention has the following beneficial effects:

the down-conversion signal processing method and the frequency conversion assembly of the satellite-borne atomic clock can convert the L-waveband signal output by the physical system of the satellite-borne hydrogen atomic clock into a lower frequency band, effectively reduce noise interference introduced in the down-conversion process and improve the quality of a carrier signal.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 is a schematic diagram illustrating a down-conversion signal processing method of a satellite-borne atomic clock according to the present invention;

FIG. 2 is a schematic signal processing flow diagram of a frequency conversion assembly of a satellite-borne atomic clock according to the present invention;

FIG. 3 is a schematic block diagram of a satellite-borne atomic clock provided by the present invention;

FIG. 4 is a front view of a frequency conversion assembly of the satellite-borne atomic clock provided by the invention;

FIG. 5 is a right side view of the frequency conversion assembly of the atomic clock on board according to the present invention;

FIG. 6 is a left side view of the frequency conversion assembly of the satellite-borne atomic clock provided by the invention.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.

The invention provides a down-conversion signal processing method of a satellite-borne atomic clock, which comprises the following steps: receiving an amplitude modulation signal output by a physical system of the satellite-borne hydrogen atomic clock; carrying out reverse isolation on the amplitude-modulated signal to obtain a first signal with a preset bandwidth; amplifying and filtering the first signal, and mixing the first signal with an oscillation signal output by a surface acoustic wave oscillator to obtain a mixing signal; and amplifying the mixing signal to obtain a carrier signal with preset gain and preset frequency.

In this embodiment, according to the output characteristic of the modulation signal of the satellite-borne hydrogen clock physical system, signal isolation needs to be performed on the input interface of the frequency conversion component to prevent the later-stage active device reflected signal from adversely affecting the atomic transition performance of the physical system, so as to affect the final performance of the atomic clock for outputting a 10MHz signal. After the L-band radio frequency signal passes through the isolation circuit, the L-band radio frequency signal is subjected to first-stage amplification, the signal is subjected to second-stage amplification through a band-pass filter, a radio frequency, an ultralow-phase noise surface wave type local vibration source, passive mixing and a mixed intermediate frequency amplification link, and finally low-noise intermediate frequency signal output is realized.

It should be noted that, in this embodiment, a scheme is adopted in which the saw oscillator oscillates a signal at a time, and it is not necessary to perform frequency doubling again to deteriorate phase noise. The total gain of signal amplification of the down-conversion component reaches 70 dB-80 dB, and the high gain characteristic of the link has higher requirements on related parameter allocation calculation and structural grounding design.

Optionally, the amplitude modulated signal comprises: error information of the microwave cavity and the crystal oscillator; the frequency range of the center frequency point of the amplitude modulation signal output by the satellite-borne hydrogen atomic clock physical system comprises: 1420.405 MHz. + -. 1.75 MHz.

In this embodiment, as a surface acoustic wave oscillation module for a mixing local oscillator, a 1440MHz center frequency ultralow phase noise sine wave local oscillation source is generated by one-time oscillation, and the phase noise needs to meet the use requirement of a satellite-borne hydrogen atomic clock.

Illustratively, the on-board hydrogen atomic clock physical system outputs an amplitude modulation signal of an L-band carrier frequency, a 3.5MHz signal bandwidth, and an error modulation signal of 25 Hz. After entering the down-conversion component, reverse isolation not less than 25dB needs to be performed on the modulation signal of the L-band carrier and the modulation signal of 3.5MHz bandwidth, so as to prevent the signal reflected by the rear-stage active device from adversely affecting the physical system.

Optionally, isolating the amplitude-modulated signal to obtain a first signal with a preset bandwidth, including: and reversely isolating the amplitude-modulated signal in a receiving channel of the amplitude-modulated signal through a ferrite isolator connected in series to obtain a first signal with a preset bandwidth.

Since the physical system of the satellite-borne hydrogen atomic clock is sensitive to external noise interference, the assembly needs to have the isolation capability of more than 25dB for a reverse channel, and a ferrite signal isolator is firstly connected in series in a receiving channel.

Optionally, the amplifying and filtering the first signal includes: and the first signal passes through a first amplifier, a filter, a first adjustable attenuation network and a second amplifier in sequence to obtain a filtering signal subjected to two-stage amplification.

In this embodiment, the rf amplifying link includes two stages of rf amplifiers and one stage of bandpass filter. Each stage of amplifier realizes the signal gain of 28dB, the gain flatness is less than or equal to +/-0.5 dB, and the out-of-band harmonic suppression is carried out on the signals through a band-pass filter in the middle of carrying out two-stage amplification on the signals.

In this embodiment, the first signal is subjected to the first-stage amplification, the interface matching, the signal filtering, and the second-stage amplification of the signal, so that the overall gain of the first amplification link is not less than 50 dB.

Optionally, the amplifying the mixing signal to obtain a carrier signal with a preset gain and a preset frequency includes: and sequentially passing the mixing signal through a second adjustable attenuation network, a first intermediate frequency amplifier, a third adjustable attenuation network and a second intermediate frequency amplifier to obtain a carrier signal which is subjected to two-stage amplification and accords with a preset gain and a preset frequency.

Illustratively, the local oscillator for passive mixing is a surface acoustic wave process type oscillator, whose output frequency range after primary oscillation is: 1.44GHz +/-500 kHz; output power: 13.5 +/-1 dBm; the full-temperature frequency fluctuation is less than or equal to 500 kHz; clutter suppression is less than or equal to-60 dBc; the phase noise is less than or equal to-90 dBc/Hz @1kHz (representing that the phase noise of the local oscillation signal at 1kHz is less than or equal to-90 dBc/Hz), or less than or equal to-124 dBc/Hz @10kHz (representing that the phase noise of the local oscillation signal at 10kHz is less than or equal to-124 dBc/Hz). The surface acoustic wave is only transmitted on the surface based on the piezoelectric effect, and the selection of the medium material is flexible, so that the surface acoustic wave has excellent phase noise and frequency temperature stability, and the adverse effect of local additional noise on an error signal is reduced to the minimum. The mixed intermediate frequency signal firstly passes through a CLC band-pass filter and secondly passes through two stages of intermediate frequency amplifiers, so that the gain of not less than 40dB can be realized.

In this embodiment, after passive frequency mixing, a group of CLC low-pass filters suppress the local oscillator leakage signal and the frequency mixing image frequency by not less than 30dB, so as to ensure that the residual unwanted signal does not affect the post-detection circuit.

The invention also provides a frequency conversion component of the satellite-borne atomic clock, which is applied to the method in any one of the first aspect, wherein the frequency conversion component comprises an L-shaped shell, and the L-shaped shell is internally provided with: the device comprises an input interface, an isolator, a first amplification link, a surface acoustic wave oscillator, a second amplification link and an output interface; wherein: the input interface is used for receiving an amplitude modulation signal output by a physical system of the satellite-borne hydrogen atomic clock; the isolator is used for carrying out reverse isolation on the amplitude-modulated signal to obtain a first signal with a preset bandwidth; the first amplification link is used for amplifying and filtering the first signal; a surface acoustic wave oscillator for generating an oscillation signal; the second amplification link is used for amplifying and filtering the first signal, and then amplifying a mixing signal obtained by mixing the first signal with the oscillation signal to obtain a carrier signal with preset gain and preset frequency; and the output interface is used for transmitting the carrier signal to an external detection circuit.

The down-conversion component in the embodiment is used for receiving an L-band signal output by a microwave cavity of a satellite-borne hydrogen atomic clock with two paths of amplitude modulation error information, moving a frequency spectrum from the L-band to a lower frequency band, and realizing high-gain amplification of a whole signal link. While controlling the local noise that may be introduced to a lower level. The design of the component comprises signal isolation, a radio frequency amplification link, band-pass filtering, an ultra-low phase noise surface wave type natural vibration source, passive mixing and an intermediate frequency amplification link. The key points of the structure are as follows: the design adopts an L-shaped compact structural layout, and is suitable for the installation mode of the cylindrical physical part of the satellite-borne hydrogen clock; the interface comprises two SMA main signal input and output ports and a feed-through capacitance type power supply interface; the link channel adopts a mode of large-area grounding of the middle shell and two sides of the microstrip substrate and a scheme of designing a single shielding cavity to effectively prevent self-excitation and crosstalk of the link. The structural design can adapt to the cylindrical characteristic of a hydrogen clock physical system, and the space of the satellite-borne hydrogen atomic clock is fully utilized.

Illustratively, the down-conversion assembly has two SMA socket interfaces in total, wherein what input SMA interface received is the amplitude modulation signal that the physical system modulated has microwave cavity and crystal oscillator error information, and the theoretical central frequency point f of carrier wave is 1420.405MHz for the physical system output, and the central frequency point can adapt to and is not less than 1.75MHz within the range variably according to the physical cavity performance difference. The modulation frequency is 25Hz, and the intensity of the carrier signal is-103 dBm-86 dBm.

Illustratively, the down-conversion assembly adopts an L-shaped compact structural layout and is suitable for the installation mode of a cylindrical physical part of a satellite-borne hydrogen clock; the high-frequency interface comprises two SMA main signal input and output ports and a feedthrough capacitor power supply interface; the link channel adopts a mode of large-area grounding of the middle shell and the two microstrip plates and designs an independent shielding cavity to effectively prevent self-excitation and crosstalk of the whole variable-frequency amplification link.

Optionally, the amplitude modulated signal comprises: error information of the microwave cavity and the crystal oscillator; the frequency range of the center frequency point of the amplitude modulation signal output by the satellite-borne hydrogen atomic clock physical system comprises: 1420.405 MHz. + -. 1.75 MHz.

Optionally, the first amplification link comprises: the device comprises a first amplifier, a filter, a first adjustable attenuation network and a second amplifier which are sequentially connected in series.

Optionally, the second amplification chain comprises: the second adjustable attenuation network, the first intermediate frequency amplifier, the third adjustable attenuation network and the second intermediate frequency amplifier are sequentially connected in series.

Illustratively, the low-pass filtered intermediate frequency amplification chain also adopts a two-stage amplification scheme, and if single-stage amplification is adopted, the risk of self-excitation of an amplification channel is increased because the circuit is extremely unstable due to too high gain. And meanwhile, impedance matching of front and rear interstage 50 omega interfaces is designed.

Optionally, the microstrip plates on both sides of the L-shaped housing are grounded, and a separate shielding cavity is formed inside the L-shaped housing.

Illustratively, due to the characteristic of the physical partial cylindrical structure of the satellite-borne hydrogen atomic clock, the down-conversion assembly is suitable for the atomic clock structure to be designed into an L-shaped structure. And the whole amplification gain of the component is high, so that the link adopts a grounding mode that the microstrip substrate is in large-area contact with the shell, and poor performance caused by poor grounding is avoided.

Illustratively, the frequency Fo of the final output carrier signal of the down-conversion component of this embodiment is 19.6MHz ± 1.75MHz, the modulation frequency is 25Hz, and the output signal strength is-32 dBm to-15 dBm.

It should be noted that, the steps in the down-conversion signal processing method of the satellite-borne atomic clock provided by the present invention may be implemented by using corresponding modules, devices, units, and the like in the frequency conversion component, and a person skilled in the art may refer to the technical solution of the system to implement the step flow of the method, that is, an embodiment in the system may be understood as a preferred example for implementing the method, and details are not repeated here.

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.