CN112636845A - Frequency standard signal phase-stabilizing transmission system based on symmetric error frequency round-trip correction - Google Patents
Frequency standard signal phase-stabilizing transmission system based on symmetric error frequency round-trip correction Download PDFInfo
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- H04B17/00—Monitoring; Testing
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- H04B17/11—Monitoring; Testing of transmitters for calibration
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
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- H04B17/20—Monitoring; Testing of receivers
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Abstract
The invention relates to a frequency standard signal phase-stabilizing transmission system based on symmetrical cross-frequency back-and-forth correction, which comprises a transmitting device and a receiving device which are connected with each other, wherein the transmitting device comprises an input end, a cross-frequency mixer, a pre-drift mixer and a first band-pass filter which are sequentially connected along the direction of a signal; the receiving device comprises a second circulator, a return signal oscillator and a correction mixer which are connected in pairs, wherein the second circulator is connected with the first circulator, the correction mixer is respectively connected with the second band-pass filter and the third band-pass filter, the second band-pass filter and the third band-pass filter are both connected with a recovery mixer, the recovery mixer is connected with the fourth band-pass filter, and the fourth band-pass filter is connected with the output end. The invention can completely eliminate the influence of the transmission medium on the phase of the frequency standard signal, and has good compatibility and strong anti-interference capability.
Description
Technical Field
The invention relates to the technical field of very long baseline interferometry, in particular to a frequency standard signal phase-stabilizing transmission system based on symmetric error frequency round-trip correction.
Background
To achieve Very Long Baseline Interferometry (VLBI), time synchronization and phase synchronization are the basis and precondition. As VLBI moves to higher frequencies and higher precision, there is a higher demand for time-frequency stability. At present, a high-stability hydrogen atomic clock is generally used as a frequency reference for observation, but a frequency standard signal is subjected to interference factors such as temperature and the like through long-distance transmission, so that a transmission medium is changed, and phase drift of the frequency standard signal is caused.
In order to eliminate the phase drift of the frequency standard signal, two methods are mainly adopted in the prior art: common-frequency round-trip correction and direct error-frequency round-trip correction. However, the compatibility of the same-frequency round-trip correction is poor, and the same-frequency round-trip correction cannot be realized in a cable, and the same-frequency round-trip correction is difficult to adapt to a severe use environment when the same is transmitted in an optical fiber. Direct frequency-error round-trip correction can be realized in a cable, but a frequency difference of about 10MHz exists between a forward-trip signal and a return-trip signal, so that the frequency difference can only reduce the multiple of phase drift, the influence of transmission medium change on the phase cannot be completely eliminated, and the cable is difficult to adapt to the conditions of long distance or severe temperature difference.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a frequency standard signal phase-stabilizing transmission system based on symmetric frequency-staggering round-trip correction, which can completely eliminate the influence of a transmission medium on the phase of a frequency standard signal and has strong anti-interference capability.
The invention provides a frequency standard signal phase-stabilizing transmission system based on symmetrical error frequency round-trip correction, which comprises a transmitting device and a receiving device which are connected with each other, wherein the transmitting device comprises an input end, an error frequency mixer, a pre-drift mixer and a first band-pass filter which are sequentially connected along the direction of a signal; the receiving device comprises two second circulators, a return signal oscillator and a correction mixer which are connected in pairs, the second circulators are connected with the first circulators, the correction mixers are respectively connected with the second band-pass filter and the third band-pass filter, the second band-pass filter is connected with the third band-pass filter, the recovery mixer is connected with the fourth band-pass filter, and the fourth band-pass filter is connected with an output end.
Further, the frequency staggering oscillator is set to generate frequency staggering signals with symmetrically staggered frequencies, and the frequency of the frequency staggering signals is smaller than half of the bandwidth of the first circulator.
Further, the input end is configured to receive an input signal, and the backhaul signal oscillator generates a backhaul signal having a frequency half of the input signal.
Further, the cross-frequency mixer is configured to mix the input signal with the cross-frequency signal to generate a first up-converted signal and a first down-converted signal; the pre-drift mixer is configured to mix the first up-conversion signal and the first down-conversion signal with the return signal respectively to generate a phase pre-drift first frequency-conversion signal group; the first band-pass filter is arranged to screen out a second down-conversion signal and a third down-conversion signal from the phase pre-drifting first frequency conversion signal group to form a trip signal; the first circulator is configured to extract the outbound signal and the return signal, transmit the outbound signal to the second circulator, and transmit the return signal to a pre-drift mixer; the correction mixer is arranged to mix the outbound signal and the inbound signal to generate a second set of frequency converted signals for correction; the second band pass filter is configured to filter out a fourth downconverted signal from the frequency converted signal for correction; the third band pass filter is configured to filter out a fifth downconverted signal from the frequency converted signal for correction; the recovery mixer is configured to mix the fourth down-conversion signal and the fifth down-conversion signal to obtain a double-frequency mixed signal; the fourth bandpass filter is arranged to screen out the signal to be output from the double frequency mixed signal.
Further, the passband frequency of the first bandpass filter is at f1-(f0-f2) To f1-(f0+f2) F is0For the frequency of the input signal, f1Is the frequency of the return signal, f2Is the frequency of the frequency error signal.
Further, the passband frequency of the second bandpass filter is the frequency of the input signal minus the frequency of the error signal.
Further, the passband frequency of the third bandpass filter is the frequency of the input signal minus the frequency of the error signal.
Further, the passband frequency of the fourth bandpass filter is 2 times the frequency of the input signal.
Optionally, the transmitting device and the receiving device are connected by a cable.
Optionally, the transmitting device and the receiving device are connected by an optical cable.
The invention relates to a phase-stabilized transmission system of a frequency standard signal, which is characterized in that an error frequency oscillator generates an error frequency signal with symmetrically staggered frequency, a return signal oscillator generates a return signal with the frequency half of the frequency of an input signal, and the input frequency standard signal is subjected to frequency mixing and filtering by utilizing the thought of round-trip correction to finally output a signal irrelevant to a transmission medium, thereby completely eliminating the influence of the transmission medium on the phase of the frequency standard signal. Meanwhile, the invention utilizes the symmetrical error frequency signal, and has good compatibility and strong anti-interference capability.
Drawings
Fig. 1 is a schematic structural diagram of a frequency standard signal phase-stable transmission system based on symmetric error frequency round-trip correction according to the present invention.
Detailed Description
The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
As shown in fig. 1, a frequency standard signal phase-stable transmission system based on symmetrical error frequency round-trip correction according to a preferred embodiment of the present invention includes a transmitting device 10 and a receiving device 20 connected to each other, and the transmitting device 10 and the receiving device 20 may be connected by a transmission cable or a transmission cable.
The transmitting device 10 includes an input end 11, an error frequency oscillator 12, an error frequency mixer 13, a pre-drift mixer 14, a first band-pass filter 15 and a first circulator 16, wherein the input end 11, the error frequency mixer 13, the pre-drift mixer 14 and the first band-pass filter 15 are sequentially connected along a signal direction, the error frequency oscillator 12 is connected with the error frequency mixer 13, and the pre-drift mixer 14 and the first band-pass filter 15 are both connected with the first circulator 16.
The receiving device 20 includes a return signal oscillator 21, a calibration mixer 22, a second band-pass filter 23, a third band-pass filter 24, a recovery mixer 25, a fourth band-pass filter 26, an output 27, and a second circulator 28, wherein the second circulator 21 is connected to the first circulator 16, the second circulator 28 is connected to the return signal oscillator 21 and the calibration mixer 22, the return signal oscillator 21 is connected to the calibration mixer 22, the calibration mixer 22 is connected to the second band-pass filter 23 and the third band-pass filter 24, the second band-pass filter 23 and the third band-pass filter 24 are both connected to the recovery mixer 25, and the recovery mixer 25, the fourth band-pass filter 26, and the output 27 are sequentially connected along the signal direction.
The connection modes between the above devices are all electrical connections, and the above devices are described in detail below.
The input terminal 11 receives a frequency standard signal from a hydrogen atomic clock as an input signal, and the frequency of the frequency standard signal is denoted as f0。
The frequency-staggered oscillator 12 generates a frequency-symmetrically staggered frequency-staggered signal having a frequency f2Less than half the bandwidth of the first circulator 16.
The frequency offset mixer 13 receives the frequency standard signal and the frequency offset signal, so that the frequency standard signal and the frequency offset signal are mixed to generate a first up-conversion signal and a first down-conversion signal. The frequency of the first up-converted signal and the frequency of the first down-converted signalThe frequency is vertically symmetrical around the frequency of the frequency standard signal, specifically, the frequency of the first up-conversion signal is f0+f2The frequency of the first down-converted signal is f0-f2。
The pre-drift mixer 14 receives the first up-converted signal, the first down-converted signal and the backhaul signal from the first circulator 16, so that the first up-converted signal and the first down-converted signal are respectively mixed with the backhaul signal to pre-drift the phase of the frequency standard signal. The first frequency conversion signal group which can generate phase pre-drift after frequency mixing comprises four signals, and the frequencies of the four signals are respectively: f. of1+(f0+f2)、f1-(f0+f2)、f1+(f0-f2)、f1-(f0-f2)。
The pass band frequency of the first band-pass filter 15 is set to f1-(f0-f2) To f1-(f0+f2) Thereby shifting the frequency f produced by the pre-drift mixer 141+(f0+f2) And f1+(f0-f2) Filtering out the signal to screen out the frequency f1-(f0+f2) Of the second down-converted signal and a frequency f1-(f0-f2) The third downconverted signal. The second down-converted signal and the third down-converted signal together form a range-going signal.
The first circulator 16 combines and extracts the outbound signal and the return signal, and transmits the outbound signal to the second circulator 28 and the return signal to the pre-drift mixer 14.
The return signal oscillator 21 in the receiving apparatus 20 generates the return signal described above and transmits it to the first circulator 16 through the second circulator 28, and the frequency f of the return signal1Is set to frequency f0Half of that.
The correction mixer 22 receives the outbound signal from the second circulator 28 and the backhaul signal from the backhaul signal oscillator 21, mixes the outbound signal and the backhaul signal, and generates a second set of frequency-converted signals for correction to implementThe phase of the frequency standard signal is corrected back and forth. The second set of frequency conversion signals for correction comprises four signals with frequencies respectively: f. of1+[f1-(f0+f2)]、f1-[f1-(f0+f2)]、f1+[f1-(f0-f2)]、f1-[f1-(f0-f2)]。
The second band-pass filter 23 and the third band-pass filter 24 each receive four signals from the correction mixer 22, wherein the pass-band frequency of the second band-pass filter 23 is set to f0-f2Thereby screening out the frequency f0-f2The fourth downconverted signal of (1). The passband frequency of the third bandpass filter 24 is set to f0+f2Thereby screening out the frequency f0+f2The fifth downconverted signal of (1).
The recovery mixer 25 receives the fourth down-conversion signal and the fifth down-conversion signal, mixes the fourth down-conversion signal and the fifth down-conversion signal, and obtains a frequency of 2f2Has a signal sum frequency of 2f0Of the signal of (1).
The passband frequency of the fourth bandpass filter 26 is set to 2f0So that the frequency is 2f0And output 27 transmits the signal to the user. The frequency is 2f0The phase of the signal (2) is independent of the transmission medium and is not shifted by the change of the transmission medium.
The following formula verifies that the phase-stable transmission system of the present invention can generate a frequency standard signal that is not affected by the transmission medium.
Firstly, the frequency f of the frequency standard signal is determined0Set to 750MHz, frequency f of the backhaul signal1Set to 375MHz, frequency f of the error signal2Set to 34MHz, the signals generated by the nodes in fig. 1 are as follows:
the node S1 is a frequency standard signal input by the hydrogen atomic clock, the frequency is 750MHz, and the analytic expression is:
cos(2πf0t+φ0)
in the formula, phi0As frequency standard informationThe initial phase of the sign.
Node S2 is the frequency-shifted signal generated by the frequency-shifted oscillator 12, with a frequency of 34MHz and an analytic formula:
cos(2πf2t+φ2)
in the formula, phi2Is the initial phase of the frequency-staggered signal.
Node S3 is a mixed signal of S1 and S2, which includes two signals with frequencies of 784MHz and 716MHz, respectively, and the analytic formula is:
cos[2π(f0+f2)t+φ0+φ2]+cos[2π(f0-f2)t+φ0-φ2]
the node S4 is a backhaul signal of the node S7 back to the transmitting device via the transmission medium, which is longer than the signal of the node S7 by the transmission delay time τ. Node S7 is the backhaul signal, with a frequency of 375MHz and an analytic expression:
cos(2πf1t+φ1)
in the formula, phi1Is the initial phase of the backhaul signal.
The signal frequency at node S4 is 375MHz, and the analytic formula is:
coS(2πf1t-2πf1τ+φ1)
the node S5 is a down-converted signal that is frequency-selected and retained by the first band-pass filter 15 after being frequency-mixed with S4 at S3, the down-converted signal includes the above second down-converted signal and third down-converted signal, the frequencies of the second down-converted signal and the third down-converted signal are 341MHz and 409MHz, and the signal analytic expression of the node S5 is:
cos[2π(f0-f1+f2)t+2πf1τ+φ0-φ1+φ2]
+cos[2π(f0-f1-f2)t+2πf1τ+φ0-φ1-φ2]
the node S6 is an outbound signal for the node S5 to reach the receiving device via the transmission medium, with a transmission delay time τ greater than the signal for the node S5. The range-extending signal comprises a second down-conversion signal with the frequency of 341MHz and a third down-conversion signal with the frequency of 409MHz, and the analytic expression is as follows:
cos[2π(f0-f1+f2)t+2π(2f1-f0-f2)τ+φ0-φ1+φ2]
+cos[2π(f0-f1-f2)t+2π(2f1-f0+f2)τ+φ0-φ1-φ2]
the node S8 is a signal obtained by mixing the node S6 and the node S7, and the signal includes a plurality of signals with different frequencies, wherein there are two signals with frequencies of 716MHz and 784MHz, respectively.
Node S9 is a fourth down-converted signal retained after frequency selection by the second band-pass filter 23 at node S8, with frequency 716MH, and the analytic formula is:
cos[2π(f0-f2)t+2π(2f1-f0+f2)τ+φ0-φ2]
node S10 is a fourth downconverted signal retained at node S8 after frequency selection by the third bandpass filter 24, with a frequency of 784MH and an analytic expression of:
cos[2π(f0+f2)t+2π(2f1-f0-f2)τ+φ0+φ2]
the node S11 is a signal to be output that is obtained by mixing S9 and S10 and is retained after frequency selection by the fourth bandpass filter 26, the frequency is 1500MHz, and the analytic expression is:
cos[4πf0t+4π(2f1-f0)τ+2φ0]
due to frequency f of the backhaul signal1Is f0Half of (2), thus 2f in the above formula1-f0Is 0, 4 pi (2 f)1-f0) Term elimination, the final analytical formula is:
cos(4πf0t+2φ0)
it can be seen that the output signal analytic expression does not contain a term related to the delay time τ, and therefore, the phase thereof is independent of the transmission medium and does not drift by the change of the transmission medium.
The above embodiments are merely preferred embodiments of the present invention, which are not intended to limit the scope of the present invention, and various changes may be made in the above embodiments of the present invention. All simple and equivalent changes and modifications made according to the claims and the content of the specification of the present application fall within the scope of the claims of the present patent application. The invention has not been described in detail in order to avoid obscuring the invention.
Claims (10)
1. A frequency standard signal phase-stable transmission system based on symmetrical error frequency round-trip correction comprises a transmitting device and a receiving device which are connected with each other,
the transmitting device comprises an input end, an offset frequency mixer, a pre-drifting mixer and a first band-pass filter which are sequentially connected along the signal direction, wherein the offset frequency mixer is connected with an offset frequency oscillator, and the pre-drifting mixer and the first band-pass filter are connected with a first circulator;
the receiving device comprises two second circulators, a return signal oscillator and a correction mixer which are connected in pairs, the second circulators are connected with the first circulators, the correction mixers are respectively connected with the second band-pass filter and the third band-pass filter, the second band-pass filter is connected with the third band-pass filter, the recovery mixer is connected with the fourth band-pass filter, and the fourth band-pass filter is connected with an output end.
2. The system according to claim 1, wherein the cross-frequency oscillator is configured to generate a cross-frequency signal with symmetrically staggered frequencies, and the frequency of the cross-frequency signal is less than half of the bandwidth of the first circulator.
3. The system according to claim 2, wherein the input terminal is configured to receive an input signal, and the backhaul signal oscillator generates a backhaul signal, and the frequency of the backhaul signal is half of the input signal.
4. The frequency standard signal phase-stable transmission system based on the symmetric error frequency round-trip correction according to claim 3,
the cross-frequency mixer is configured to mix the input signal with the cross-frequency signal to generate a first up-conversion signal and a first down-conversion signal;
the pre-drift mixer is configured to mix the first up-conversion signal and the first down-conversion signal with the return signal respectively to generate a phase pre-drift first frequency-conversion signal group;
the first band-pass filter is arranged to screen out a second down-conversion signal and a third down-conversion signal from the phase pre-drifting first frequency conversion signal group to form a trip signal;
the first circulator is configured to extract the outbound signal and the return signal, transmit the outbound signal to the second circulator, and transmit the return signal to a pre-drift mixer;
the correction mixer is arranged to mix the outbound signal and the inbound signal to generate a second set of frequency converted signals for correction;
the second band pass filter is configured to filter out a fourth downconverted signal from the frequency converted signal for correction;
the third band pass filter is configured to filter out a fifth downconverted signal from the frequency converted signal for correction;
the recovery mixer is configured to mix the fourth down-conversion signal and the fifth down-conversion signal to obtain a double-frequency mixed signal;
the fourth bandpass filter is arranged to screen out the signal to be output from the double frequency mixed signal.
5. The system according to claim 3, wherein the first band-pass filter has a passband at f1-(f0-f2) To f1-(f0+f2) In-line with the aboveM, f0For the frequency of the input signal, f1Is the frequency of the return signal, f2Is the frequency of the frequency error signal.
6. The frequency standard signal phase-stable transmission system based on the symmetric error frequency round trip correction according to claim 3, wherein the passband frequency of the second band-pass filter is the frequency of the input signal minus the frequency of the error frequency signal.
7. The frequency standard signal phase-stable transmission system based on the symmetric error frequency round trip correction according to claim 3, wherein the passband frequency of the third band-pass filter is the frequency of the input signal minus the frequency of the error frequency signal.
8. The frequency standard signal phase-stable transmission system based on the symmetric error frequency round trip correction according to claim 3, wherein the passband frequency of the fourth bandpass filter is 2 times the frequency of the input signal.
9. The system according to claim 1, wherein the transmitting device and the receiving device are connected by a cable.
10. The frequency standard signal phase-stable transmission system based on the symmetrical frequency error round-trip correction according to claim 1, wherein the transmitting device and the receiving device are connected through an optical cable.
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