CN111373885B - Rubidium clock circuit structure for temperature coefficient compensation by utilizing step frequency multiplier - Google Patents
Rubidium clock circuit structure for temperature coefficient compensation by utilizing step frequency multiplier Download PDFInfo
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- CN111373885B CN111373885B CN201318002012.4A CN201318002012A CN111373885B CN 111373885 B CN111373885 B CN 111373885B CN 201318002012 A CN201318002012 A CN 201318002012A CN 111373885 B CN111373885 B CN 111373885B
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Abstract
The invention discloses a rubidium clock circuit structure utilizing a step frequency multiplier to carry out temperature coefficient compensation, the temperature sensitivity of an SRD is utilized to carry out rubidium clock temperature coefficient compensation so as to reduce the temperature coefficient of a rubidium clock overall machine, the output microwave power can be positive or negative along with the change of temperature, the microwave power frequency shift is positive, therefore, the microwave power is changed into a positive temperature coefficient along with the rise of temperature, the microwave power is changed into a negative temperature coefficient along with the rise of temperature, namely, the rubidium clock circuit temperature coefficient caused by the positive or negative can be negative, according to the positive or negative magnitude of the temperature coefficient of the existing physical part, a step frequency multiplier (SRD) which is opposite to the temperature coefficient of the physical part and has the closest magnitude is actively debugged to be installed into the rubidium clock overall machine, the rubidium clock temperature coefficient compensation is realized, the temperature coefficient of the rubidium clock overall machine is reduced, the method is simple to realize, and the temperature coefficient of the rubidium clock overall machine can be greatly reduced, theoretically, the temperature coefficient of the rubidium clock complete machine can be close to zero.
Description
Technical Field
The invention relates to a rubidium clock circuit structure, in particular to a rubidium clock circuit structure which does not need to change the existing rubidium clock design and utilizes a step frequency multiplier to perform temperature coefficient compensation, and belongs to the technical field of rubidium clock design.
Background
The rubidium clock is an atomic clock which is most widely applied, has the advantages of small volume, light weight, low power consumption, low price, high reliability, long service life, good short-term stability and the like, is convenient for miniaturization and batch production, and the working principle of the rubidium clock is shown in fig. 1. The specific principle is as follows: the output signal (10MHz signal) of the crystal oscillator generates 6834.6875MHz microwave signal through frequency doubling, synthesis and other measures, the microwave signal is fed into a physical part, the physical part is equivalent to a quantum frequency discriminator, the fed microwave signal is subjected to frequency discrimination to obtain a detection signal, the detection signal generates voltage control voltage through a servo circuit to control the crystal oscillator, and the output frequency of the crystal oscillator is locked on the physical part through the loop. The resonance frequency of the physical part of the rubidium clock is determined by the transition between the rubidium atom ground state hyperfine energy levels, the transition frequency is very stable and not easily influenced by the external environment, and the stability, the drift rate and the aging rate are small.
The rubidium clock is composed of a core part and an external temperature control circuit (TCB). The core part is composed of a physical part and a circuit part, and the core part is a main body of a frequency standard and is used for realizing the whole frequency locking loop. The external temperature control circuit has the function of ensuring that the rubidium clock has a relatively stable temperature environment on the planet. Therefore, the temperature coefficient of the rubidium clock overall machine is jointly determined by the temperature coefficient of the physical part, the temperature coefficient of the circuit part and the thermal gain of the external temperature control system (determined by the heat capacity of the controlled temperature part and the gain of the temperature control circuit). The temperature coefficient of the circuit part influences the rubidium clock frequency through microwave power frequency shift, namely the temperature coefficient of the circuit part can be changed by changing the magnitude of microwave power, and the optical frequency shift and the collision frequency shift of the physical part caused by the temperature sensitivity of the rubidium bulb system influence the rubidium clock frequency. Factors influencing the medium-and-long-term stability of the rubidium clock are the influence of the temperature coefficient except for a flicker platform determined by factors such as circuit noise, microwave power stability, physical part optical frequency shift and collision frequency shift, and specifically, the magnitude of the temperature coefficient has a large influence on the frequency stability of the rubidium clock at a sampling time of 1000s and above because the temperature change is a slow change process during actual long-term test.
As shown in fig. 2, in a general rubidium clock design, a rubidium clock circuit portion is composed of 7 components, namely, 9 frequency multipliers, a servo circuit, an isolation amplifier, SRDs (step multipliers), a frequency synthesis circuit, a TCB control circuit, and a crystal oscillator. The physical part of the rubidium clock is an independent part, and the rest parts in the circuit part are not sensitive to temperature change except that the SRD is sensitive to temperature. The physical part is sensitive to temperature variations, with a temperature coefficient of typically + -7e-13/℃～±5e-12Between/° c. The output power of an SRD varies greatly with temperature, and is typically: the temperature variation range is 30-40 ℃, and the output power variation delta p of the SRD is about +/-0.5 dB to +/-1 dB. Frequency shift fp of about +1e due to microwave power-11The frequency temperature variation coefficient Td caused by the power factor is Td ═ Δ p × fp ± (1 e)-11/℃～±5e-12V. C. Namely, the temperature coefficient of the rubidium clock circuit is + -1e-11/℃～±5e-12/℃。
The method for calculating the temperature coefficient T of the rubidium clock complete machine comprises the following steps: if T is (circuit part temperature coefficient Td + physical part temperature coefficient Tw)/(temperature control gain K of temperature control system), if the temperature coefficient of a certain rubidium clock circuit part is +1e-11The temperature coefficient of the physical part is +5 e-12/DEG C, the temperature control gain of the temperature control system is 10, and the overall temperature coefficient T of the rubidium clock is [ (+1 e)-11)+(+5e-12)]/10＝1.5e-12V. C. Because the temperature sensitivity of the step frequency multiplier (SRD) in the circuit part and the temperature sensitivity of the physical part are determined by the device characteristics and the physical mechanism, it is difficult to directly reduce the temperature coefficient, and the traditional method for reducing the temperature coefficient is to increase the gain of a single-layer temperature control system by increasing the number of temperature control layers or by changing the form of a temperature control circuit, etc., so as to increase the K value. Both of these approaches add complexity and cost to the overall machine.
Disclosure of Invention
The technical problem solved by the invention is as follows: the rubidium clock circuit structure overcomes the defects of the prior art, the rubidium clock circuit structure for temperature coefficient compensation by using the step frequency multiplier is simple to realize, any design of the existing rubidium clock does not need to be changed, and the complexity and the cost of the whole machine are not increased.
The technical solution of the invention is as follows: a rubidium clock circuit structure utilizing a step frequency multiplier to carry out temperature coefficient compensation comprises a frequency multiplier, a servo circuit, an isolation amplifier, a step frequency multiplier, a frequency synthesis circuit, a TCB control circuit and a crystal oscillator, wherein the step frequency multiplier comprises a pi-type input matching circuit, a bias circuit, a resonant network, a pulse generator and a cavity filter, the pi-type input matching circuit comprises capacitors C3, C4, C5, C6, C7, C8 and an inductor L2, the capacitors C3, C4 and C5 are connected in parallel and then one end of the capacitors is grounded, the other end of the capacitors C6, C7 and C8 is connected in parallel and then the other end of the capacitors is grounded, the other end of the capacitors is connected with the output end of an inductor L2, the bias circuit comprises capacitors C1, a choke coil L1, a resistor R1 and a capacitor C2, one end of the capacitor C1 is connected with a radio frequency signal output by the frequency multiplier in series, the other end of the inductor L2 is connected with the input end of the inductor R1 and one end of the capacitor C686, the other end of the resonant network is connected with one end of a choke coil L1, the other end of the choke coil L1 is connected between a capacitor C1 and an inductor L2, the resonant network is composed of an inductor L3, capacitors C9 and C10, one end of the parallel connection of the capacitors C9 and C10 is connected with the output end of the inductor L3, the other end of the parallel connection is grounded, the input end of the inductor L3 is connected with the output end of the inductor L2, a step diode V1 serving as a pulse generator is connected with the capacitors C9 and C10 in parallel, the positive electrode of a step diode V1 is connected with the output end of the inductor L3, the negative electrode of the step diode V1 is grounded, the step diode V1, the capacitors C9 and C10 and the output coupling capacitor Cc jointly form a cavity filter, the step diode V1, the attenuated oscillation waveform and the frequency signal output by the frequency synthesis circuit are subjected to difference frequency, and the signal after difference frequency is filtered by the cavity filter and then is filtered by the coupling capacitor Cc to obtain the microwave signal output by the step frequency multiplier.
The step diode is a 2J1C type step diode.
Compared with the prior art, the invention has the advantages that: the invention reduces the temperature coefficient of the rubidium clock by performing rubidium clock temperature coefficient compensation by utilizing the temperature sensitivity of a step multiplier (SRD) under the condition of not increasing the complexity of the rubidium clock circuit and the whole machine, in particular to utilize the characteristic that the step tube frequency multiplier (SRD) is sensitive to the temperature, so that the output microwave power can be positive or negative along with the change of the temperature, because the microwave power frequency shift is positive, the microwave power is a positive temperature coefficient which is increased along with the temperature rise, and the microwave power is a negative temperature coefficient which is decreased along with the temperature rise, namely, the temperature coefficient of the rubidium clock circuit can be positive or negative, according to the positive and negative of the temperature coefficient of the existing physical part, the step multiplier (SRD) which is opposite to the temperature coefficient of the physical part and has the closest magnitude is actively debugged and loaded into the rubidium clock whole machine to realize the rubidium clock temperature coefficient compensation, the temperature coefficient of the rubidium clock complete machine is reduced, the realization is simple, the temperature coefficient of the rubidium clock complete machine can be greatly reduced, theoretically, the temperature coefficient of the rubidium clock complete machine can be close to zero, and further the long-term stability and the environmental adaptability of the rubidium clock are improved.
Drawings
FIG. 1 is a block diagram of the operating principles of a rubidium clock;
FIG. 2 is a diagram illustrating a layout of a conventional rubidium clock;
FIG. 3 is a schematic circuit diagram of a step multiplier;
fig. 4 is a schematic diagram of the operation of the step multiplier.
Detailed Description
As shown in fig. 3, the step multiplier comprises an i-type input matching circuit, a bias circuit, a resonant network, a pulse generator and a cavity filter, wherein the i-type input matching circuit comprises capacitors C3, C4, C5, C6, C7, C8 and an inductor L2, capacitors at two ends of an inductor L2 are all designed in a form of parallel connection of a plurality of capacitors so as to finely adjust the matching network, so that the circuit is in a good matching state, unnecessary loss in energy transmission is reduced, the capacitors C3, C4 and C5 are connected in parallel, one end of each capacitor is grounded, the other end of each capacitor is connected with an input end of an inductor L2, the capacitors C6, C7 and C8 are connected in parallel, one end of each capacitor is grounded, the other end of each capacitor is connected with an output end of an inductor L2, the bias circuit comprises a capacitor C1, a coil L1, a resistor R1 and a capacitor C2, one end of a capacitor C1 is connected with a radio frequency signal output by the frequency multiplier in series, the other end of, the other end of the choke coil L1 is connected with one end of a choke coil L1, the other end of the choke coil L1 is connected between a capacitor C1 and an inductor L2, a resonant network is composed of a resonant inductor L3, capacitors C9 and C10, one end of the capacitors C9 and C10 is connected with the output end of the inductor L3 after being connected in parallel, the other end of the capacitor L3 is grounded, the input end of the inductor L3 is connected with the output end of the inductor L2, a step diode V1 serving as a pulse generator is connected with the capacitors C9 and C10 in parallel, the anode of a step diode V1 is connected with the output end of the inductor L3, the cathode of the step diode V1 is grounded, the step diode V1, the capacitors C9 and C10 and an output coupling capacitor Cc form a cavity filter together, the step, the attenuated oscillation waveform and the frequency signal output by the frequency synthesis circuit are subjected to difference frequency, and the signal after difference frequency is filtered by the cavity filter and then is filtered by the coupling capacitor Cc to obtain the microwave signal output by the step frequency multiplier.
Specifically, the method comprises the following steps: the step diode V1 is used as a step tube pulse generator to generate large-amplitude narrow pulses with rich harmonic waves for exciting a distributed parameter type resonance circuit in a square body to obtain an attenuation oscillation waveform with the frequency of 6840MHz, the difference frequency of the attenuation oscillation waveform and a 5.3125MHz signal generated by a frequency synthesis circuit (DDS) is obtained, and then a 6834.6875MHz microwave signal output by a step frequency multiplier is obtained through a coupling capacitor Cc. In the technical scheme, the SRD frequency multiplier adopts step tube cavity external frequency multiplication, so that output power, noise and clutter are observed visually, and debugging is convenient.
The working process of the step multiplier is shown in fig. 4: 9 frequency of the frequency multiplier output is fiThe signal is applied to a pulse generator after passing through a bias and n-shaped input matching circuit, a large-amplitude narrow pulse with rich harmonic waves is generated due to the extremely strong nonlinearity of the junction capacitance of the step diode, and then a resonant network formed by a resonant inductor L3 and SRD junction capacitances C9 and C10 is excited by the large-amplitude narrow pulse to form a frequency f-NfiThe oscillation waveform is attenuated, so that most of harmonic energy is concentrated near the required Nth harmonic, the difference frequency is carried out on the oscillation waveform and a low-frequency signal generated by a rubidium clock frequency synthesis circuit, the oscillation waveform passes through a cavity filter, and then an 6834.6875MHz microwave signal output by a step frequency multiplier is obtained through a coupling capacitor Cc and is output to a load (a physical part).
The specific implementation method of the invention is as follows: according to the measured temperature coefficient of the physical part and microwave power frequency shift data, a circuit structure shown in fig. 3 is designed, when the frequency multiplier of the step tube is debugged in a single machine, the frequency multiplier is in an optimal state through debugging a matching circuit, through debugging C3, C4, C5, L2, C6, C7 and C8 in fig. 3, a step diode (a 2J1C type step diode sensitive to temperature) is selected, and then the temperature performance is determined through a single preset temperature test so as to meet the positive and negative of the temperature coefficient required by the whole machine.
The specific embodiment is as follows: according to the measured temperature coefficient and microwave power frequency shift data of the physical part of the rubidium clock, when the SRD (step tube frequency multiplier) is debugged in a single machine mode, the rule that the power of a 6.8GHz signal output by the SRD changes along with the temperature is actively controlled by selecting debugging of a step diode and a matching circuit, and due to the temperature sensitivity and the individual difference of the step tube, the power of the 6.8GHz signal output by some SRDs can change along with the temperature in actual debuggingThe power of the 6.8GHz signal output by the SRD changes along with the temperature change in the same direction, the temperature coefficient of the SRD is a positive temperature coefficient, and the temperature coefficient of the SRD is a negative temperature coefficient. Typically, such temperature coefficients are of the order of about + -2 e-11/℃～±5e-12/° c, and the temperature coefficient of the physical part is of the order of ± 7e-13/℃～±5e-12When the temperature coefficient of a physical portion is-7E/. degree.C-12About/° C, the power of the 6.8GHz signal output by the SRD (step tube frequency multiplier) is required to be changed positively along with the temperature change when the SRD is debugged on a single machine, the change amplitude is controlled to be about 0.7dB, and the temperature coefficient is closest to +7E when the SRD is assembled on the whole machine after debugging is finished-12Frequency multiplier of SRD step tube at/deg.C and the temperature coefficient is-7E-12The physical parts of about/° C are jointly filled, so that the temperature coefficient can be compensated, and according to the method, the temperature coefficient of the whole machine can be reduced to 10-13Of even lower order. For example, the following steps are carried out: assume that the temperature control gain K of the temperature control system is 10.
1. A temperature coefficient Tw1 was measured for 1 physical part (1#) in the range of 30 ℃ to 40 ℃ and assumed here to be-7 e-12V. C. Measuring the microwave power frequency shift fp1 of the physical part, assuming that the microwave power frequency shift of the physical part is 1e-11/dB.
2. When the SRD (step tube frequency multiplier) is debugged in a single machine, the debugging of the step diode and the matching circuit is selected, so that when the power of a 6.8GHz signal output by the SRD changes in the range of 30-40 ℃, the change is about +0.7dB, and the temperature coefficient caused by the change is about +0.7 × (1 e) Td-11)＝+7e-12V. C. This SRD is set to 1 #.
3. When the whole machine is assembled, the 1# physical part and the 1# SRD (step tube frequency multiplier) are assembled into the whole machine to complete matching, and therefore the temperature coefficient of the rubidium clock is as follows: t (circuit part temperature coefficient Td1+ physical part temperature coefficient Tw 1)/(temperature control gain K of temperature control system) (+7 e)-12)+(-7e-12)/10≈0。
The above example is ideal, and in actual operation, since complete temperature coefficient compensation is difficult to achieve, there is always a residual temperature coefficient, but this method can still greatly reduce the temperature coefficient of the rubidium clock. In the above example, if no temperature compensation is performed, the temperature coefficient is still-7 e in the physical portion-12In the case of/° C, one temperature coefficient is selected to be-1 e-11The temperature coefficient of the rubidium clock overall machine is-1.7 e per SRD of DEG C-12V. C. I.e. more than 10 times greater than the compensated temperature coefficient.
Those skilled in the art will appreciate that the details of the invention not described in detail in the specification are within the skill of those skilled in the art.
Claims (2)
1. The utility model provides an utilize step multiplier to carry out rubidium clock circuit structure of temperature coefficient compensation, comprises frequency multiplier, servo circuit, isolation amplifier, step multiplier, frequency synthesis circuit, TCB control circuit and crystal oscillator, its characterized in that: the step frequency multiplier comprises a pi-type input matching circuit, a bias circuit, a resonant network, a pulse generator and a cavity filter, wherein the pi-type input matching circuit comprises capacitors C3, C3 and an inductor L3, one end of each capacitor C3, C3 and C3 is grounded after being connected in parallel, the other end of each capacitor C3, C3 and C3 are grounded after being connected in parallel, the bias circuit comprises a capacitor C3, a choke coil L3, a resistor R3 and a capacitor C3, one end of the capacitor C3 is connected with a radio-frequency signal output by the frequency multiplier in series, the other end of the inductor L3 is connected in series, one end of the resistor R3 and the capacitor C3 is grounded after being connected in parallel, the other end of the choke coil L3 is connected with one end of the choke coil L3, the other end of the choke coil L3 is connected with the capacitor C3 and the inductor L3, the capacitor C3 and the capacitor L3 and the inductor L3 are connected in parallel, the, the other end of the inductor L3 is grounded, the input end of the inductor L2 is connected with the output end of the inductor L2, a step diode V1 serving as a pulse generator is connected with capacitors C9 and C10 in parallel, the anode of a step diode V1 is connected with the output end of the inductor L3, the cathode of the step diode V1 is grounded, the step diode V1, the capacitors C9 and C10 and an output coupling capacitor jointly form a cavity filter, the step diode V1 generates a narrow pulse for exciting a resonance network, the resonance network outputs an attenuation oscillation waveform, the attenuation oscillation waveform and a frequency signal output by a frequency synthesis circuit carry out difference frequency, and a signal after difference frequency is filtered by the cavity filter to obtain a microwave signal output by a step frequency multiplier through a coupling capacitor Cc;
setting the temperature coefficient of the step frequency multiplier to be a positive temperature coefficient when the power of the 6.8GHz signal output by the step frequency multiplier changes along with the temperature in the same direction, and otherwise, setting the temperature coefficient to be a negative temperature coefficient; when the temperature coefficient of a physical part of a rubidium clock is-7E-12/DEG C, when the single unit of the step frequency multiplier is debugged, the power of a 6.8GHz signal output by the step frequency multiplier changes in the same direction along with the temperature, the change amplitude is controlled to be 0.7dB, and after debugging is finished, the step frequency multiplier with the temperature coefficient closest to + 7E-12/DEG C and the temperature coefficient of-7E are assembled when the whole unit is assembled-12The physical parts of/° c are co-housed, thereby achieving compensation of the temperature coefficient.
2. The rubidium clock circuit structure for temperature coefficient compensation by using step frequency multiplier as claimed in claim 1, wherein: the step diode is a 2J1C type step diode.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107809216A (en) * | 2017-11-23 | 2018-03-16 | 西安空间无线电技术研究所 | A kind of pressure-sensitive compensation circuit of OCXO and OCXO frequency pressure-sensitive character ameliorative ways |
| CN111464145A (en) * | 2020-04-07 | 2020-07-28 | 成都仕芯半导体有限公司 | Digital step attenuator |
| CN112187182A (en) * | 2020-10-22 | 2021-01-05 | 上海航天电子通讯设备研究所 | Satellite-borne X-frequency band miniaturized high-order frequency doubling device |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107809216A (en) * | 2017-11-23 | 2018-03-16 | 西安空间无线电技术研究所 | A kind of pressure-sensitive compensation circuit of OCXO and OCXO frequency pressure-sensitive character ameliorative ways |
| CN107809216B (en) * | 2017-11-23 | 2021-09-03 | 西安空间无线电技术研究所 | OCXO pressure-sensitive compensation circuit and OCXO frequency pressure-sensitive characteristic improvement method |
| CN111464145A (en) * | 2020-04-07 | 2020-07-28 | 成都仕芯半导体有限公司 | Digital step attenuator |
| CN112187182A (en) * | 2020-10-22 | 2021-01-05 | 上海航天电子通讯设备研究所 | Satellite-borne X-frequency band miniaturized high-order frequency doubling device |
| CN112187182B (en) * | 2020-10-22 | 2023-05-23 | 上海航天电子通讯设备研究所 | Space-borne X-frequency-band miniaturized high-order frequency doubling device |
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