CN109787616B - Frequency signal switching system and switching method - Google Patents
Frequency signal switching system and switching method Download PDFInfo
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Abstract
The invention discloses a frequency signal switching system and a switching method, comprising the following steps: the device comprises a main channel frequency source, a standby channel frequency source, a phase discriminator, a low-pass filter, an AD converter, a DA converter, a local oscillator and an MCU (microprogrammed control unit); the main channel frequency source and the standby channel frequency source are respectively connected with the phase discriminator, the low-pass filter and the AD converter in sequence; the output end of the AD converter is connected with the input end of the MCU, the output end of the MCU is connected with the input end of the DA converter, and the output end of the DA converter is connected with the input end of the local oscillator; the output of the local oscillator is divided into two paths, one path is used for outputting signals, and the other path is respectively connected with the input end of each phase discriminator. The invention can eliminate the influence of inherent phase difference existing between each path of frequency signal, so that the phase does not jump and the signal is not interrupted in the switching process, and the continuity and the stability of the frequency signal can be ensured.
Description
Technical Field
The invention belongs to the technical field of time frequency, and particularly relates to a frequency signal switching system and a frequency signal switching method.
Background
In the fields of precision time service, aerospace, radar synchronization, tip weapon control, high-speed communication, deep space exploration and the like, higher requirements are provided for frequency signals, and the frequency signals are required to have the characteristics of accuracy, continuity, stability, reliability and the like.
In practical use, users often need to have a plurality of frequency sources for reliability and stability of frequency signals, and in order to perform coordination, a switching method needs to be introduced, so that when one frequency source in use fails, the other frequency source in use is quickly and reliably switched to the other normal frequency source. However, at present, most systems still adopt hard switching modes such as a radio frequency switch to realize signal switching, so that the output signals are easy to generate the problems of burrs, jumps, interruptions and the like in the switching process, and the stability and the continuity of the signals are influenced.
Disclosure of Invention
The present invention is directed to a system and a method for switching frequency signals, so as to solve the above-mentioned problems. The method of the invention adopts a soft switching mode of digital error tracking and channel gating to replace the traditional hard switching mode of the radio frequency switch, can eliminate the influence of inherent phase difference existing between each path of frequency signals, ensures that the phase does not jump and the signals are not interrupted in the switching process, and can ensure the continuity and stability of the frequency signals.
In order to achieve the purpose, the invention adopts the following technical scheme:
a frequency signal switching system, comprising: the device comprises a main channel frequency source, a standby channel frequency source, a phase discriminator, a low-pass filter, an AD converter, a DA converter, a local oscillator and an MCU (microprogrammed control unit); the main channel frequency source and the standby channel frequency source are respectively connected with the phase discriminator, the low-pass filter and the AD converter in sequence; the output end of the AD converter is connected with the input end of the MCU, the output end of the MCU is connected with the input end of the DA converter, and the output end of the DA converter is connected with the voltage-controlled voltage input end of the local oscillator; the output of the local oscillator is divided into two paths, one path is used for outputting signals, and the other path is respectively connected with the input end of each phase discriminator.
Furthermore, the number of the standby channel frequency sources is one or more, and the standby channel frequency sources are arranged according to a preset priority.
Further, the MCU includes:
a subtractor for calculating a phase error;
the PI arithmetic unit is used for calculating a control quantity according to the input signal;
the input end of the control unit is connected with the output end of the subtracter; the control unit is connected with the PI operation unit and can transmit information, and the output end of the control unit is used for outputting the control quantity.
Further, the phase jitter of the output signal before and after switching of the frequency source is less than 5 ps.
A method of switching frequency signals, comprising the steps of:
step 1, locking a local oscillator frequency signal on a main channel frequency signal in a digital phase locking mode;
step 2, detecting the phase error signals of the main channel frequency signal and the local oscillator frequency signal and the phase error signals of the standby channel frequency signal and the local oscillator frequency signal in real time; when the jitter of the phase error signal exceeds a preset threshold value, the corresponding channel frequency signal is considered to be in fault;
step 3, when the main channel frequency signal is not detected to be in fault, repeating the step 1 and the step 2; when the main channel frequency signal is detected to be in fault, the phase error signal of the spare channel without fault is selected as the input signal of the digital phase lock, the local oscillator frequency signal is locked on the spare channel frequency signal in the digital phase lock mode, and the frequency signal switching is completed.
Further, step 1 specifically includes:
step 1.1, taking a phase error signal of a main channel frequency signal and a local oscillator frequency signal as an input signal of a PI operation unit, and calculating by the PI operation unit according to the input signal to obtain a control quantity;
and step 1.2, outputting the control quantity obtained in the step 1.1 to a DA converter through a control unit, and outputting an analog voltage signal by the DA converter to control the frequency and the phase of a local oscillator signal so as to realize the locking of the local oscillator frequency signal on a main channel frequency signal.
Further, step 2 specifically includes:
step 2.1, phase error data of frequency signals of each channel and frequency signals of a local oscillator in a preset number are collected;
step 2.2, respectively calculating the average value of the collected phase error data of each channel to obtain the target value of the locking phase of each channel;
step 2.3, acquiring and obtaining real-time phase error data of each channel, and taking the difference value between the real-time phase error data of each channel and a locked phase target value as a phase error signal of the channel;
and 2.4, comparing the obtained phase error signals of each channel with a preset threshold value, and judging whether the frequency signals of each channel have faults or not.
A multichannel frequency signal switching method is based on the frequency signal switching system of the invention, the number of spare channel frequency sources of the switching system is multiple, and the method specifically comprises the following steps:
step 1, in the main channel, the frequency signal f of the main channel0With a local oscillator frequency signal fVCOSequentially passes through a phase discriminator and low-pass filteringObtaining a phase error uDerr0(t); phase error uDerr0(t) obtaining data AD via AD converter0Will AD0As an input signal of a PI arithmetic unit of the MCU;
step 2, the PI arithmetic unit carries out AD calculation according to the data0And calculating a control quantity DATA by the following formula:
DATA＝p×AD0+i×∑AD0，
in the formula, Sigma AD0Is AD0P is a proportionality coefficient of a digital PI operation unit, and I is an integral coefficient of the digital PI operation unit;
step 3, outputting the control quantity DATA to a DA converter through a control unit of the MCU;
step 4, the DA converter outputs a control voltage signal uC (t) and a local oscillator signal fVCOIs controlled in frequency and phase such that the output signal fOUTIs locked to f0(ii) a Wherein f isOUT＝fVCO；
Step 5, in each spare channel, fVCOIs locked to f0Then, the frequency signal f of the spare channels 1 and 2 … Q is collected1、f2…fQAnd fVCOThe voltage signal sequentially passes through the phase discriminator and the low-pass filter and is converted into AD1、AD2…ADQ；
Step 6, AD1、AD2…ADQRespectively collecting n times and averaging to obtain target values of the locking phases of the standby channels 1 and 2 … Q
n is an integer greater than 1;
step 7, calculating to obtain real-time AD acquired by the AD converter by using a subtracter in the MCU1、AD2……ADQAnd
as a difference value of each channel phase error signal Derr1、Derr2……DerrQ；
Step 8, detecting AD through the control unit of the MCU0～ADQWhen the jitter exceeds a threshold value, ADhJudging that the frequency signal of the path has a fault, otherwise, judging that the frequency signal of the path is normal;
step 9, if the control unit does not detect the main channel frequency signal f0Repeating the steps 1 to 8 when a fault occurs; if the control unit detects the main channel frequency signal f0If the fault occurs, judging the working state of the standby channel signal; and the control unit selects the spare channel phase error signal without fault as an input signal of a PI operation unit of the MCU according to a preset sequence, locks the local oscillator frequency signal on the spare channel frequency signal and completes frequency signal switching.
Further, in step 8, the threshold ADh＝10。
Further, the MCU is a single chip microcomputer with preset computing capability.
Compared with the prior art, the invention has the following beneficial effects:
the invention relates to a seamless switching method of multi-channel frequency signals, which realizes the seamless switching of the frequency signals by adopting a digital error tracking and software gating method on the basis of a digital phase-locked loop technology. Firstly, a phase error signal of a main channel frequency signal and a local oscillator frequency signal is used as an input signal of a PI operation unit of a digital phase-locked loop, and the output of the PI operation unit drives a DA converter to control a local oscillator, so that digital phase locking is realized; after the digital phase-locked loop finishes locking the frequency signal of the main channel, taking the phase difference between each path of standby channel signal and the frequency signal of the local oscillator as a target value of the locking phase corresponding to each path; when the main channel frequency signal has a fault, the control unit selects the phase error signal of the spare channel signal without the fault and the local oscillator frequency signal as the input signal of the PI operation unit of the digital phase-locked loop to complete digital phase locking, thereby realizing the seamless switching of the frequency signals. The invention adopts a soft switching mode of digital error tracking and software gating instead of a hard switching mode of a radio frequency switch, the digital error tracking technology eliminates the influence of inherent phase difference between each path of frequency signal, so that the phase of the switching process does not jump, the soft switching mode of the software gating does not have the action of a hardware switch, so that the frequency signal is not interrupted in the switching process, and the continuity of the frequency signal is ensured.
The invention adopts the soft switching mode of digital error tracking and software gating to replace the traditional hard switching mode of the radio frequency switch, eliminates the influence of inherent phase difference existing between each path of frequency signal, ensures that the phase does not jump and the signal is not interrupted in the switching process, ensures the continuity and stability of the frequency signal, and ensures that a user can effectively and stably coordinate and use a plurality of paths of frequency signal sources.
Through practical tests, the phase jitter of the output signals of the multi-channel frequency signal seamless switching system before and after signal switching can be less than 5 ps.
Drawings
Fig. 1 is a schematic block diagram of a three-channel frequency signal switching system according to an embodiment of the present invention;
fig. 2 is a schematic block diagram of a flow chart of a multi-channel frequency signal switching method according to an embodiment of the present invention.
Detailed Description
The present invention will be further described in detail with reference to the accompanying drawings and specific examples, which are provided for implementing the technical solutions of the present invention and for providing detailed embodiments and specific work flows, but the scope of the present invention is not limited to the following examples.
Referring to fig. 1, fig. 1 is a schematic block diagram of an embodiment with three channels as an example. The frequency signal switching system comprises a main channel frequency source, a 2-channel standby channel frequency source, a phase discriminator, a low-pass filter, an AD converter, a DA converter, a local oscillator and a singlechip. Wherein the backup channel frequency sources have a priority order of f1、f2(ii) a The single chip microcomputer realizes functions of a subtracter, a PI operation unit, a control unit and the like.
In the invention, a main channel frequency source and a standby channel frequency source are respectively connected with a phase discriminator, a low-pass filter and an AD converter in sequence; the output end of the AD converter is connected with the input end of the MCU, the output end of the MCU is connected with the input end of the DA converter, and the output end of the DA converter is connected with the input end of the local oscillator; the output of the local oscillator is divided into two paths, one path is used for outputting signals, the other path is divided into N paths which are respectively connected with the input ends of the phase discriminator of each standby channel and the phase discriminator of the main channel, and N is a natural number. The selection of the single chip microcomputer only needs to satisfy certain computation capability, for example, MSP430FE427, STM32F103RCT6, and the like can be selected.
The MCU includes: a subtractor for calculating a phase error; the PI arithmetic unit is used for calculating a control quantity according to the input signal; the input end of the control unit is connected with the output end of the subtracter; the control unit is connected with the PI operation unit and can transmit information, and the output end of the control unit is used for outputting the control quantity.
According to the switching system, the phase jitter of the output signals before and after the switching of the frequency source is less than 5 ps.
Referring to fig. 2, a method for seamless switching of multi-channel frequency signals according to the present invention includes the following steps:
step 1, main channel frequency signal f0With a local oscillator frequency signal fVCODirectly obtaining a phase error signal uD through a phase discriminator and a low-pass filtererr0(t); will phase error signal uDerr0(t) data AD obtained by passing through AD converter0As an input signal to the PI operation unit of the digital phase locked loop.
Step 2, the PI arithmetic unit calculates according to AD0The control amount DATA is calculated as shown in the following equation:
DATA＝p×AD0+i×∑AD0，
in the formula, sigma AD0Is AD0P is a proportionality coefficient of the digital PI operation unit, and I is an integral coefficient of the digital PI operation unit.
And step 3: the control unit outputs the control amount DATA to the DA converter.
And 4, step 4: the DA converter outputs a control voltage signal uC (t) to the local oscillator signal fVCOThe frequency and phase of the signal are controlled.
To this end, the digital phase-locked loop completes the locking of the main channel frequency signal, i.e. the output signal fOUTIs locked in f0Wherein f isOUT＝fVCO。
And then, seamless switching of the frequency signal is realized by adopting a digital error tracking and software gating method.
And 5: continuous acquisition f of AD convertersVCOIs locked to f0Time, spare channel 1, 2 frequency signal f1、f2And fVCOVoltage signal passing through phase discriminator and low-pass filter is converted into AD1、AD2。
Step 6: AD1、AD2Collecting n times and averaging to obtain target value of locking phase of spare channels 1 and 2
Where n is 10.
And 7: obtaining new AD collected by AD converter by subtracter1、AD2And with
As a difference value of each channel phase error signal Derr1、Derr2。
And 8: the control unit detects AD0～AD2When the jitter exceeds a threshold value, ADhJudging that the frequency signal of the path has a fault, otherwise, judging that the frequency signal of the path is normal; herein take ADh＝10。
And step 9: if the control unit does not detect the main channel frequency signal f0Repeating the steps 1 to 8 when a fault occurs; if the control unit detects the main channel frequency signal f0If a fault occurs, the standby channel signal f is judged1、f2In a predefined sequence, the control unit selects the phase error signal of the non-faulty standby channelThe signal is used as an input signal of a PI operation unit of the digital phase-locked loop to realize digital phase locking.
From the main frequency signal f by practical tests0Switching to alternate channel signal f1Or f2And the phase jitter of the output signals before and after switching is less than 5 ps.
The three-channel embodiment of the present invention provides a seamless switching method for multi-channel frequency signals. On the basis of the digital phase-locked loop technology, the seamless switching of the frequency signals is realized by adopting a digital error tracking and software gating method. The phase error signal of the main channel frequency signal and the local oscillator frequency signal is used as the input signal of the PI arithmetic unit of the digital phase-locked loop, and the output of the PI arithmetic unit drives the DA converter to control the local oscillator, thereby realizing the digital phase-locked. After the digital phase-locked loop finishes locking the main channel frequency signal, the phase difference between each path of standby channel signal and the local oscillator frequency signal is used as a locking phase target value corresponding to each path. When the main channel frequency signal has a fault, the control unit selects the phase error signal of the spare channel signal without the fault and the local oscillator frequency signal as the input signal of the PI operation unit of the digital phase-locked loop to complete digital phase locking, thereby realizing the seamless switching of the frequency signals. The invention adopts a soft switching mode of digital error tracking and software gating instead of a hard switching mode of a radio frequency switch, and the digital error tracking technology eliminates the influence of inherent phase difference existing between each path of frequency signal, so that the phase of the switching process does not jump; the soft switching mode of software gating has no action of a hardware switch, so that the frequency signal is not interrupted in the switching process, and the continuity of the frequency signal is ensured.
The three-channel embodiment of the invention adopts a soft switching mode of digital error tracking and software gating, replaces the traditional hard switching mode of the radio frequency switch, eliminates the influence of inherent phase difference existing between each channel of frequency signals, ensures that the phase does not jump and the signals are not interrupted in the switching process, and ensures the continuity and stability of the frequency signals, thereby ensuring that a user can effectively and stably coordinate and use a plurality of channels of frequency signal sources. Through practical tests, the phase jitter of the output signals of the multichannel frequency signal seamless switching system before and after signal switching can be less than 5 ps.
The above-described embodiments are merely specific examples for further explaining the objects, technical solutions and advantageous effects of the present invention in detail, and the present invention is not limited thereto. Any modification, equivalent replacement, improvement and the like made within the scope of the disclosure of the present invention are included in the protection scope of the present invention.
Claims (4)
1. A frequency signal switching system, comprising: the device comprises a main channel frequency source, a standby channel frequency source, a phase discriminator, a low-pass filter, an AD converter, a DA converter, a local oscillator and an MCU (microprogrammed control unit);
the main channel frequency source and the standby channel frequency source are respectively connected with the phase discriminator, the low-pass filter and the AD converter in sequence; the output end of the AD converter is connected with the input end of the MCU, the output end of the MCU is connected with the input end of the DA converter, and the output end of the DA converter is connected with the voltage-controlled voltage input end of the local oscillator; the output of the local oscillator is divided into two paths, one path is used for outputting signals, and the other path is respectively connected with the input end of each phase discriminator;
the frequency signal switching method of the frequency signal switching system comprises the following steps:
step 1, locking a local oscillator frequency signal on a main channel frequency signal in a digital phase locking mode;
step 2, detecting phase error signals of the main channel frequency signal and the local oscillator frequency signal and phase error signals of the standby channel frequency signal and the local oscillator frequency signal in real time; when the jitter of the phase error signal exceeds a preset threshold value, the corresponding channel frequency signal is considered to have a fault;
step 3, when the main channel frequency signal is not detected to be in fault, repeating the step 1 and the step 2; when the main channel frequency signal is detected to be in fault, selecting a phase error signal of a spare channel without fault as an input signal of digital phase locking, and locking a local oscillator frequency signal on the spare channel frequency signal in a digital phase locking mode to complete frequency signal switching;
the step 1 specifically comprises: step 1.1, taking a phase error signal of a main channel frequency signal and a local oscillator frequency signal as an input signal of a PI operation unit, and calculating by the PI operation unit according to the input signal to obtain a control quantity; step 1.2, outputting the control quantity obtained in the step 1.1 to a DA converter through a control unit, and outputting an analog voltage signal by the DA converter to control the frequency and the phase of a local oscillator signal so as to realize the locking of the local oscillator frequency signal on a main channel frequency signal;
the step 2 specifically comprises the following steps: step 2.1, phase error data of frequency signals of each channel and frequency signals of a local oscillator in a preset number are collected; step 2.2, respectively calculating the average value of the collected phase error data of each channel to obtain the target value of the locking phase of each channel; step 2.3, acquiring and obtaining real-time phase error data of each channel, and taking the difference value between the real-time phase error data of each channel and a locked phase target value as a phase error signal of the channel; step 2.4, comparing the obtained phase error signals of each channel with a preset threshold value, and judging whether the frequency signals of each channel have faults or not;
the phase jitter of the output signal before and after switching of the frequency source is less than 5 ps.
2. A frequency signal switching system according to claim 1, wherein the number of backup channel frequency sources is one or more and is prioritized.
3. The frequency signal switching system according to claim 1, wherein the MCU comprises:
a subtractor for calculating a phase error;
the PI arithmetic unit is used for calculating a control quantity according to the input signal;
the input end of the control unit is connected with the output end of the subtracter; the control unit is connected with the PI operation unit and can transmit information, and the output end of the control unit is used for outputting the control quantity.
4. A multi-channel frequency signal switching method, based on the frequency signal switching system of claim 1, wherein the number of spare channel frequency sources of the switching system is plural, and the method specifically comprises the following steps:
step 1, in the main channel, the frequency signal f of the main channel0With a local oscillator frequency signal fVCOSequentially passing through a phase discriminator and a low-pass filter to obtain a phase error uDerr0(t); phase error uDerr0(t) obtaining data AD via AD converter0Will AD0As an input signal of a PI arithmetic unit of the MCU;
step 2, the PI arithmetic unit carries out AD calculation according to the data0And calculating a control quantity DATA by the following formula:
DATA＝p×AD0+i×∑AD0，
in the formula, sigma AD0Is AD0P is a proportionality coefficient of the digital PI operation unit, and i is an integral coefficient of the digital PI operation unit;
step 3, outputting the control quantity DATA to a DA converter through a control unit of the MCU;
step 4, the DA converter outputs a control voltage signal uC (t) and a local oscillator signal fVCOIs controlled in frequency and phase such that the output signal fOUTIs locked in f0(ii) a Wherein f isOUT＝fVCO；
Step 5, in each spare channel, fVCOIs locked to f0Then, the frequency signal f of the spare channels 1 and 2 … Q is collected1、f2…fQAnd fVCOThe voltage signal sequentially passes through a phase discriminator and a low-pass filter and is converted into AD1、AD2…ADQ；
Step 6, AD1、AD2…ADQRespectively collecting n times and averaging to obtain target values of the locking phases of the standby channels 1 and 2 … Q
n is an integer greater than 1;
step 7, calculating to obtain real-time AD acquired by the AD converter by using a subtracter in the MCU1、AD2……ADQAnd
as a difference value of each channel phase error signal Derr1、Derr2……DerrQ；
Step 8, detecting AD through the control unit of the MCU0～ADQWhen the jitter exceeds a threshold value, ADhJudging that the frequency signal of the path has a fault, otherwise, judging that the frequency signal of the path is normal;
step 9, if the control unit does not detect the main channel frequency signal f0Repeating the steps 1 to 8 when a fault occurs; if the control unit detects the main channel frequency signal f0If the fault occurs, judging the working state of the standby channel signal; and the control unit selects the spare channel phase error signal without fault as an input signal of a PI operation unit of the MCU according to a preset sequence, locks the local oscillator frequency signal on the spare channel frequency signal and completes frequency signal switching.
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