CN112485519A - Method, system, device and medium for measuring absolute frequency difference based on delay line - Google Patents
Method, system, device and medium for measuring absolute frequency difference based on delay line Download PDFInfo
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- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/02—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage
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- H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
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Abstract
The invention discloses a method, a system, a device and a medium for measuring absolute frequency difference based on a delay line, wherein the method comprises the following steps: the local crystal oscillator generates an output signal; performing frequency division processing on the output signal to obtain a pulse signal with the period within the measuring range of the delay line measuring device; measuring the pulse period of the pulse signal subjected to frequency division through a delay line measuring device to obtain a frequency deviation value; generating a corresponding control output based on the frequency deviation value output by the delay line measurement device; converting the control output into the actual frequency control quantity of the local crystal oscillator; controlling the output frequency of the local crystal oscillator based on the frequency control quantity, and compensating the deviation of the output signal of the local crystal oscillator; the invention can compensate the deviation of the output signal of the local crystal oscillator and has higher compensation precision.
Description
Technical Field
The invention relates to the field of time-frequency equipment signal processing, in particular to a method, a system, a device and a medium for measuring absolute frequency difference based on a delay line.
Background
In the time-keeping process of the time-frequency device, namely when no GPS/BDS or other sources provide reference clocks (such as pulses of seconds) from the outside, the local crystal oscillator will have frequency drift due to the aging characteristic or the temperature characteristic of the local crystal oscillator. In order to stabilize a normal output local frequency signal without an external reference clock, it is necessary to compensate for the frequency offset of the crystal oscillator.
The conventional compensation method is generally divided into two steps:
step 1: recording the aging parameters or temperature parameters of the local crystal oscillator under the condition of long-time existence of an external reference clock source;
step 2: under the condition of no external reference source, fitting an aging curve according to the data recorded in the step 1 and compensating;
there is a significant problem with the above approach, namely: the deviation between the fitted curve and the actual curve is certain, and when the treatment is carried out for a long time, for example, more than 3 days, the fitted curve compensation cannot reach the required precision.
Disclosure of Invention
In order to solve the problem of insufficient precision in the traditional compensation mode, the invention provides a method, a system, a device and a medium for measuring absolute frequency difference based on a delay line.
In order to achieve the above object, the present invention provides a method for measuring an absolute frequency difference based on a delay line, the method comprising:
the local crystal oscillator generates an output signal;
performing frequency division processing on the output signal to obtain a pulse signal with the period within the measuring range of the delay line measuring device;
measuring the pulse period of the pulse signal subjected to frequency division through a delay line measuring device to obtain a frequency deviation value;
generating a corresponding control output based on the frequency deviation value output by the delay line measurement device;
converting the control output into the actual frequency control quantity of the local crystal oscillator;
and controlling the output frequency of the local crystal oscillator based on the frequency control quantity, and compensating the deviation of the output signal of the local crystal oscillator.
The method for independently measuring the frequency of the local crystal oscillator and compensating the frequency of the crystal oscillator by three steps of frequency division output, delay line pulse width and deviation compensation without an external reference clock is introduced, so that the defect that a fitting curve is compared with an actual curve in the traditional method is overcome, and the precision of frequency deviation compensation of the local crystal oscillator is improved.
The method converts the frequency deviation of the local crystal oscillator into a signal capable of being independently measured, and extracts the frequency deviation by measuring the signal.
Because the delay line measuring device adopts the circuit delay measurement mode to carry out time delay measurement, the measuring process is independent of the characteristics of the local crystal oscillator. In particular, a high-resolution pulse interval measuring device (such as TDC-GP21) used in the ultrasound has very good measuring precision (can reach 1ps resolution), and can meet the frequency monitoring of a crystal oscillator with frequency deviation of more than 1 ppb.
Preferably, the nominal output frequency of the local crystal oscillator in the method is f0Period T of0The output of the local crystal oscillator has frequency deviation delta F corresponding to delta T deviation in one period and frequency deviation coefficient Foc_delta＝Δf/f0Corresponding to the time domain, i.e. Foc_delta＝ΔT/T0。
Preferably, in the method, the pulse signal with the period being T and located in the measuring range of the delay line is generated through frequency division processingdiv，TdivT is the original period, N is the frequency division coefficient, and the time deviation of one period of the pulse signal is Δ Tdiv＝ΔT×N。
The invention also provides an absolute frequency difference measuring system based on the delay line, which comprises:
the local crystal oscillator is used for generating an output signal;
the frequency divider is used for carrying out frequency division processing on the output signal to obtain a pulse signal with the period positioned in the measuring range of the delay line measuring device;
a delay line measuring device for measuring the pulse period of the divided pulse signal to obtain a frequency deviation value;
a processor for generating a corresponding control output based on the frequency deviation value output by the delay line measurement device;
the crystal oscillator control generation circuit: and the frequency control unit is used for controlling the output frequency of the local crystal oscillator based on the frequency control quantity and compensating the deviation of the output signal of the local crystal oscillator.
The system introduces a method for independently measuring the frequency of the local crystal oscillator and compensating the frequency of the crystal oscillator by three steps of frequency division output, delay line pulse width and deviation compensation under the condition of no external reference clock, avoids the defect that the traditional method adopts a fitting curve to compare with an actual curve, and improves the precision of the frequency deviation compensation of the local crystal oscillator.
The system converts the frequency deviation of the local crystal oscillator into a signal capable of being independently measured, and extracts the frequency deviation by measuring the signal.
Because the delay line measuring device adopts the circuit delay measurement mode to carry out time delay measurement, the measuring process is independent of the characteristics of the local crystal oscillator. In particular, a high-resolution pulse interval measuring device (such as TDC-GP21) used in the ultrasound has very good measuring precision (can reach 1ps resolution), and can meet the frequency monitoring of a crystal oscillator with frequency deviation of more than 1 ppb.
Further, the nominal output frequency of the local crystal oscillator in the system is f0Period T of0The output of the local crystal oscillator has frequency deviation delta F corresponding to delta T deviation in one period and frequency deviation coefficient Foc_delta＝Δf/f0Corresponding to the time domain, i.e. Foc_delta＝ΔT/T0。
Furthermore, the distributor in the system generates a pulse signal with the period being in the measuring range of the delay line after processing, and the period of the pulse signal is Tdiv，TdivT is the original period, N is the frequency division coefficient, and the time deviation of one period of the pulse signal is Δ Tdiv＝ΔT×N。
Furthermore, the frequency divider in the system is an independent D trigger group, or the frequency division of the counter is carried out by using the MCU.
Further, the processing flow of the system comprises: training the system process and the punctual measurement correction process;
the training system process:
in the process of domesticating a system, an external reference clock source exists;
stabilizing the output of the local crystal oscillator at a nominal output value through closed-loop control of the local crystal oscillator;
recording the nominal period value of the output signal of the delay line measuring device at the moment;
the punctual measurement correction process:
no external reference source exists in the process of measuring and correcting in real time;
continuously measuring and reading the output of the delay line measuring device, and smoothing the output;
continuously monitoring the deviation between the output of the delay line measuring device and a nominal output value, and generating the output of the local crystal oscillator control quantity when the deviation is greater than the lowest adjustment threshold;
and continuously measuring the amplitude of an output signal of the delay line measuring device to realize closed-loop control.
The invention also provides an absolute frequency difference measuring device, which comprises a memory, a processor and a computer program stored in the memory and capable of running on the processor, wherein the processor realizes the steps of the absolute frequency difference measuring method based on the delay line when executing the computer program.
The invention also provides a computer readable storage medium having stored thereon a computer program for implementing the steps of the delay line based absolute frequency difference measurement method when executed by a processor.
One or more technical schemes provided by the invention at least have the following technical effects or advantages:
the invention can compensate the deviation of the output signal of the local crystal oscillator and has higher compensation precision.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention;
FIG. 1 is a schematic flow chart of a method for measuring absolute frequency difference based on a delay line;
fig. 2 is a schematic diagram of the components of the delay line based absolute frequency difference measurement system.
Detailed Description
In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings. It should be noted that the embodiments of the present invention and features of the embodiments may be combined with each other without conflicting with each other.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described and thus the scope of the present invention is not limited by the specific embodiments disclosed below.
It will be understood by those skilled in the art that in the present disclosure, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship indicated in the drawings for ease of description and simplicity of description, and do not indicate or imply that the referenced devices or components must be constructed and operated in a particular orientation and thus are not to be considered limiting.
It is understood that the terms "a" and "an" should be interpreted as meaning that a number of one element or element is one in one embodiment, while a number of other elements is one in another embodiment, and the terms "a" and "an" should not be interpreted as limiting the number.
Example one
Referring to fig. 1, fig. 1 is a schematic flow chart of a delay line-based absolute frequency difference measurement method, an embodiment of the present invention provides a delay line-based absolute frequency difference measurement method, including:
the local crystal oscillator generates an output signal;
performing frequency division processing on the output signal to obtain a pulse signal with the period within the measuring range of the delay line measuring device;
measuring the pulse period of the pulse signal subjected to frequency division through a delay line measuring device to obtain a frequency deviation value;
generating a corresponding control output based on the frequency deviation value output by the delay line measurement device;
converting the control output into the actual frequency control quantity of the local crystal oscillator;
and controlling the output frequency of the local crystal oscillator based on the frequency control quantity, and compensating the deviation of the output signal of the local crystal oscillator.
Example two
Referring to fig. 2, fig. 2 is a schematic diagram illustrating an absolute frequency difference measurement system based on a delay line, according to an embodiment of the present invention, the system includes:
the local crystal oscillator is used for generating an output signal;
the frequency divider is used for carrying out frequency division processing on the output signal to obtain a pulse signal with the period positioned in the measuring range of the delay line measuring device;
a delay line measuring device for measuring the pulse period of the divided pulse signal to obtain a frequency deviation value;
a processor for generating a corresponding control output based on the frequency deviation value output by the delay line measurement device;
the crystal oscillator control generation circuit: and the frequency control unit is used for controlling the output frequency of the local crystal oscillator based on the frequency control quantity and compensating the deviation of the output signal of the local crystal oscillator.
Wherein, in the first and second embodiments:
local crystal oscillator: generally a constant temperature crystal oscillator, whose standard isThe output frequency is called f0Period T of0. Due to the aging characteristic of the crystal oscillator, after a period of time, the output of the crystal oscillator has frequency deviation delta F, corresponding to the deviation of delta T in a period, a frequency deviation coefficient F is generally definedoc_delta＝Δf/f0. Corresponding to the time domain, i.e. Foc_delta＝ΔT/T0。
Frequency division processing: since the measurement range of the general delay line measurement is limited (generally within 100 us), in order to utilize the measurement range of the delay line to the maximum, a pulse signal having a period T within the measurement range of the delay line is generated by frequency division processingdivT × N, where T is the original period and N is the division coefficient. The frequency divider can be an independent D trigger group or utilize the MCU to divide the frequency of the counter. After frequency division, although the frequency is reduced, the frequency offset coefficient does not change. In the presence of frequency deviation, the time deviation of one period of the frequency deviation after frequency division is delta Tdiv＝ΔT×N。
Delay line measurement: since the delay measurement output of the delay line measurement device depends only on the characteristics such as temperature and the like, and is independent of the frequency of the input signal, the pulse period of the divided signal is measured by the delay line measurement device.
A processor: and receiving and processing the deviation value output by the delay line measuring device, monitoring the period deviation, and generating corresponding control output according to the control method of the crystal oscillator.
Wherein, the processing procedure of the processor (MCU) is as follows:
1. when the delay line measuring device works, the MCU reads data once per second, and the reading mode is a digital signal of the SPI interface.
And 2, smoothing the read delay line measurement data by the MCU to eliminate the burst interference and the measurement white noise influence.
3. Assuming that the measurement accuracy of the delay line is 1ps, and the measurement pulse width is set to 50us, a higher resolution (generally considered to be improved by 10 times) can be obtained due to the long-time accumulation (more than 1200 seconds) of the measurement noise.
4. Then under this assumption, a frequency offset accuracy of 1/(50 × 1000 × 10), i.e., 2 × 10-8And (4) frequency precision.
5. When such a frequency measurement deviation occurs, the voltage control of the OCXO is adjusted.
The crystal oscillator control generation circuit: and converting the control output by the processor into the actual frequency control quantity of the crystal oscillator.
EXAMPLE III
The third embodiment of the present invention provides an apparatus for measuring absolute frequency difference, including a memory, a processor, and a computer program stored in the memory and executable on the processor, where the processor implements the steps of the method for measuring absolute frequency difference based on a delay line when executing the computer program.
The processor may be a Central Processing Unit (CPU), or other general-purpose processor, a digital signal processor (digital signal processor), an Application Specific Integrated Circuit (Application Specific Integrated Circuit), an off-the-shelf programmable gate array (field programmable gate array) or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component, or the like. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
The memory can be used for storing the computer program and/or the module, and the processor can realize various functions of the absolute frequency difference measuring device in the invention by operating or executing the data stored in the memory. The memory may mainly include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required for at least one function (such as a sound playing function, an image playing function, etc.), and the like. Further, the memory may include high speed random access memory, and may also include non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card, a secure digital card, a flash memory card, at least one magnetic disk storage device, a flash memory device, or other volatile solid state storage device.
Example four
A fourth embodiment of the present invention provides a computer-readable storage medium, where a computer program is stored, and when the computer program is executed by a processor, the method for measuring an absolute frequency difference based on a delay line is implemented.
The absolute frequency difference measuring device, if implemented in the form of a software functional unit and sold or used as a separate product, may be stored in a computer-readable storage medium. Based on such understanding, all or part of the flow in the method of implementing the embodiments of the present invention may also be stored in a computer readable storage medium through a computer program, and when the computer program is executed by a processor, the computer program may implement the steps of the above-described method embodiments. Wherein the computer program comprises computer program code, an object code form, an executable file or some intermediate form, etc. The computer readable medium may include: any entity or device capable of carrying said computer program code, a recording medium, a usb-disk, a removable hard disk, a magnetic disk, an optical disk, a computer memory, a read-only memory, a random access memory, a point carrier signal, a telecommunications signal, a software distribution medium, etc. It should be noted that the computer readable medium may contain content that is appropriately increased or decreased as required by legislation and patent practice in the jurisdiction.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. A method for measuring absolute frequency difference based on a delay line, the method comprising:
the local crystal oscillator generates an output signal;
performing frequency division processing on the output signal to obtain a pulse signal with the period within the measuring range of the delay line measuring device;
measuring the pulse period of the pulse signal subjected to frequency division through a delay line measuring device to obtain a frequency deviation value;
generating a corresponding control output based on the frequency deviation value output by the delay line measurement device;
converting the control output into the actual frequency control quantity of the local crystal oscillator;
and controlling the output frequency of the local crystal oscillator based on the frequency control quantity, and compensating the deviation of the output signal of the local crystal oscillator.
2. The method of claim 1, wherein the local oscillator has a nominal output frequency f0Period T of0The output of the local crystal oscillator has frequency deviation delta F corresponding to delta T deviation in one period and frequency deviation coefficient Foc_delta＝Δf/f0Corresponding to the time domain, i.e. Foc_delta＝ΔT/T0。
3. The delay line-based absolute frequency difference measuring method according to claim 1, wherein the pulse signal having a period T in a measurement range of the delay line is generated by the frequency dividing processdiv，TdivT is the original period, N is the frequency division coefficient, and the time deviation of one period of the pulse signal is Δ Tdiv＝ΔT×N。
4. A delay line based absolute frequency difference measurement system, the system comprising:
the local crystal oscillator is used for generating an output signal;
the frequency divider is used for carrying out frequency division processing on the output signal to obtain a pulse signal with the period positioned in the measuring range of the delay line measuring device;
a delay line measuring device for measuring the pulse period of the divided pulse signal to obtain a frequency deviation value;
a processor for generating a corresponding control output based on the frequency deviation value output by the delay line measurement device;
the crystal oscillator control generation circuit: and the frequency control unit is used for controlling the output frequency of the local crystal oscillator based on the frequency control quantity and compensating the deviation of the output signal of the local crystal oscillator.
5. The delay line based absolute frequency difference measurement system of claim 4, wherein the nominal output frequency of the local oscillator is f0Period T of0The output of the local crystal oscillator has frequency deviation delta F corresponding to delta T deviation in one period and frequency deviation coefficient Foc_delta＝Δf/f0Corresponding to the time domain, i.e. Foc_delta＝ΔT/T0。
6. The delay line based absolute frequency difference measuring system according to claim 4, wherein the distributor generates the pulse signal having a period T within the measuring range of the delay line after processingdiv，TdivT is the original period, N is the frequency division coefficient, and the time deviation of one period of the pulse signal is Δ Tdiv＝ΔT×N。
7. The delay line based absolute frequency difference measurement system of claim 4, wherein the frequency divider is a separate D flip-flop group or a counter frequency division is performed by using MCU.
8. The delay line based absolute frequency difference measurement system of claim 4, wherein the processing flow of the system comprises: training the system process and the punctual measurement correction process;
the training system process:
in the process of domesticating a system, an external reference clock source exists;
stabilizing the output of the local crystal oscillator at a nominal output value through closed-loop control of the local crystal oscillator;
recording the nominal period value of the output signal of the delay line measuring device at the moment;
the punctual measurement correction process:
no external reference source exists in the process of measuring and correcting in real time;
continuously measuring and reading the output of the delay line measuring device, and smoothing the output;
continuously monitoring the deviation between the output of the delay line measuring device and a nominal output value, and generating the output of the local crystal oscillator control quantity when the deviation is greater than the lowest adjustment threshold;
and continuously measuring the amplitude of an output signal of the delay line measuring device to realize closed-loop control.
9. An absolute frequency difference measuring device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the delay line based absolute frequency difference measuring method according to any one of claims 1 to 3 when executing the computer program.
10. A computer-readable storage medium, in which a computer program is stored, which, when being executed by a processor, carries out the steps of the method for delay line based absolute frequency difference measurement according to any of claims 1-3.
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