Small frequency source module with low phase noise

Abstract

The invention relates to a small frequency source module with low phase noise, which is applied to the technical field of frequency sources, and comprises a dual-redundancy reference source unit, a dynamic temperature compensation unit, a frequency synthesis unit, an intelligent switching control unit and a structure protection unit, the main reference source module and the standby reference source module both adopt MEMS resonators with the Q value not smaller than 10000, the dynamic temperature compensation unit is used for dynamically adjusting the output frequency of the resonators according to the temperature, and the intelligent switching control unit is used for controlling switching between the main reference source module and the standby reference source module; through collaborative design of the high-Q-value MEMS resonator, dynamic temperature compensation and dual-redundancy intelligent switching, the problems of large size, high phase noise, large temperature drift and low reliability of a traditional frequency source module are solved, miniaturization design is realized, and strict requirements of scenes such as communication equipment and a navigation system on miniaturization can be met.

Description

TECHNICAL FIELD

[0001] The application relates to a frequency source module, in particular to a low-phase-noise small-size frequency source module applied to the technical field of frequency sources. BACKGROUND

[0002] The frequency source module is an electronic component or subsystem for generating stable, accurate and adjustable frequency signals, which is widely used in communication, radar, navigation, measurement and other fields. Its core function is to provide high-precision "time reference" or "frequency reference" for various electronic devices, ensuring the reliability of system synchronization, signal modulation / demodulation, data transmission and other functions.

[0003] The Chinese patent application with the publication number CN115902778A discloses a universal small-size frequency source, which comprises a power supply, a frequency synthesizer and a RAM single-chip microcomputer. The power supply is connected with the RAM single-chip microcomputer and the frequency synthesizer. The application can make the existing low-phase-noise phase-locked loop more stable.

[0004] The Chinese patent application with the publication number CN118232908A discloses a small-size agile frequency source. By connecting the output ports of the phase-locked source circuit unit and the differential signal transmission circuit unit to the temperature control loop unit, the system can monitor and adjust the working temperature in real time to ensure the stability of the system under different environmental temperatures.

[0005] Phase noise is one of the key indicators for measuring the performance of a frequency source, which describes the stability of the frequency of the output signal of the frequency source. Low phase noise means that the output signal of the frequency source is purer and has less impact on the performance of the system. Traditional frequency source modules mainly use quartz crystal oscillators or oven-controlled crystal oscillators as reference sources, which have defects such as large size, high phase noise, large temperature drift and low reliability. Therefore, we propose a low-phase-noise small-size frequency source module. SUMMARY

[0006] In view of the above prior art, the technical problem to be solved by the application is that traditional frequency source modules mainly use quartz crystal oscillators or oven-controlled crystal oscillators as reference sources, which have defects such as large size, high phase noise, large temperature drift and low reliability.

[0007] To solve the above problems, the application provides a low-phase-noise small-size frequency source module, which comprises:

[0008] The double-redundancy reference source unit comprises a main reference source module and a backup reference source module, and the main reference source module and the backup reference source module both use micro-electro-mechanical system resonators with a Q value not less than 10000.

[0009] A dynamic temperature compensation unit, comprising a first temperature compensation module, a second temperature compensation module and a data storage module, for dynamically adjusting the output frequency of the resonator according to the temperature;

[0010] a frequency synthesis unit, including a phase-locked loop, for multiplying the compensated reference frequency to a target output frequency;

[0011] An intelligent switching control unit, comprising a switching control module and a micro-electromechanical system switch, for controlling the switching between the main reference source module and the backup reference source module;

[0012] Structural protection unit, including shielding cover and multi-layer printed circuit board;

[0013] The main reference source module is integrated with a main temperature sensor, and the backup reference source module is integrated with a secondary temperature sensor. The main temperature sensor and the secondary temperature sensor are respectively connected to the first temperature compensation module and the second temperature compensation module by signal. The first temperature compensation module and the second temperature compensation module are respectively connected to the main reference source module and the backup reference source module by signal. The switching control module monitors the output frequency of the main reference source module in real time.

[0014] The above-mentioned small frequency source module with low phase noise solves the problems of large size, high phase noise, large temperature drift and low reliability of traditional frequency source modules through the collaborative design of high-Q value micro-electromechanical system resonator, dynamic temperature compensation and dual redundant intelligent switching.

[0015] As a further improvement of the present application, the fundamental frequency of the MEMS resonator is 10 MHz to 26 MHz, and when the reference temperature is 25°C, the frequency temperature coefficient thereof in the temperature range of -40°C to 85°C is ±0.5 ppm / °C.

[0016] As a further improvement of the present application, before the frequency source module leaves the factory, the calibration coefficients are generated and written into the data storage module through the following process:

[0017] Place the frequency source module in an incubator and stabilize it at -40°C, 0°C, 25°C, and 85°C for 2 hours.

[0018] The output frequency of the MEMS resonator at each temperature point is measured using a spectrum analyzer, and the offset relative to the nominal frequency is calculated.

[0019] The temperature-frequency curve is fitted by the least squares method to generate the calibration coefficients and write them into the data storage module.

[0020] As a further improvement of the present application, the dynamic temperature compensation logic of the dynamic temperature compensation unit is:

[0021] The temperature compensation module monitors the temperature T of the reference source module in real time through a temperature sensor, obtains the calibration coefficient K(T) corresponding to the temperature T from the data storage module, and calculates the frequency offset Δf = K(T)·(T-T0), where T0 is the nominal temperature of 25°C.

[0022] The temperature compensation module sends an adjustment voltage to the phase-locked loop to adjust the frequency division ratio of the phase-locked loop so that the compensated output frequency f_out=f_nominal+Δf, where f_nominal is the target nominal frequency.

[0023] As a further improvement of this application, the switching logic of the intelligent switching control unit is:

[0024] The switching control module monitors the output frequency f_main of the main reference source module at a sampling frequency of 10 Hz and calculates the absolute value of the deviation between the output frequency f_main and the nominal frequency f_nominal: Δf_main = |f_main-f_nominal|;

[0025] When Δf_main>1ppm, the switching control module controls the MEMS switch to switch from the main reference source module to the backup reference source module within 1μs;

[0026] When Δf_main≤0.5ppm for 10s, it is determined that the main reference source module has returned to normal, and the switching control module controls the MEMS switch to switch from the backup reference source module back to the main reference source module.

[0027] As a further improvement of the present application, when the main reference source module is working normally, the backup reference source module is in a low-power standby state with a power consumption of ≤1mW.

[0028] As a further improvement of the present application, the shielding cover is made of aluminum alloy, and a thermally conductive silicone pad is attached to the bottom;

[0029] The specific interlayer structure of the multilayer printed circuit board is:

[0030] Bottom layer: power plane, copper thickness 35μm, surface coated with solder mask;

[0031] The second layer: ground plane, with a copper thickness of 35μm, connected to the bottom layer through a via array;

[0032] The third layer: RF signal layer, microstrip line width 0.5mm, surface coated with solder mask;

[0033] Top layer: control signal layer, differential line spacing 0.2mm, surface coated with solder mask.

[0034] As another improvement of the present application, the frequency source module also includes a fusion control unit, which includes a thermometer transformer module and a control decision module. The main temperature sensor is signal-connected to the thermometer transformer module, the thermometer transformer module is signal-connected to the control decision module, and the control decision module is signal-connected to the switching control module.

[0035] As another improved supplement to the present application, the control logic of the fusion control unit includes:

[0036] The temperature sensor module collects the temperature T of the main reference source module at a frequency of 10Hz. 主 And transmit it to the control decision module in real time;

[0037] When T 主 When the temperature is higher than 85℃, the control decision module sends a switching signal to the switching control module, so that the switching control module controls the MEMS switch to switch from the main reference source module to the backup reference source module within 1μs;

[0038] When T 主 After the temperature reaches ≤70℃, it is determined that the main reference source module has returned to normal, and the regulation and decision module sends a switchback signal to the switch control module, so that the switch control module controls the micro-electromechanical system switch to switch back from the backup reference source module to the main reference source module.

[0039] As another improvement supplement of the present application, the control logic of the fusion control unit also includes:

[0040] Thermometer module changes according to T 主 The temperature change rate dT / dt of the main reference source module is obtained by differential calculation and transmitted to the control decision module in real time;

[0041] When dT / dt>5℃ / s, the control decision module sends a switching signal to the switching control module, so that the switching control module controls the micro-electromechanical system switch to switch from the main reference source module to the backup reference source module within 1μs;

[0042] When dT / dt≤1℃ / s for 10s and T 主 If the temperature is ≤85℃, it is determined that the main reference source module has returned to normal, and the regulation and decision module sends a switchback signal to the switch control module, so that the switch control module controls the micro-electromechanical system switch to switch from the backup reference source module back to the main reference source module.

[0043] To summarize, this application solves the problems of large size, high phase noise, large temperature drift and low reliability of traditional frequency source modules through the collaborative design of high-Q value micro-electromechanical system resonators, dynamic temperature compensation and dual redundant intelligent switching, and realizes miniaturization design, which can meet the stringent requirements of miniaturization in scenarios such as communication equipment and navigation systems; in addition, this application also deeply integrates the dynamic temperature compensation mechanism and the dual redundant intelligent switching mechanism through the fusion control unit, and constructs a full-link closed-loop management system of "temperature monitoring-compensation adjustment-risk warning-redundant switching", realizing a leap-forward upgrade from "single temperature drift compensation" to "active prevention and control of temperature risks + performance redundancy + thermal redundancy". This integration not only improves the reliability and stability of the module in complex environments, but also further optimizes the phase noise performance, and ultimately improves the reliability and long-term stability of the frequency source module in the entire temperature range and complex working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a structural block diagram of a small frequency source module with low phase noise in the first embodiment of the present application;

[0045] Figure 2 A flow chart for generating calibration coefficients in the first embodiment of the present application;

[0046] Figure 3 This is a dynamic temperature compensation logic diagram of the dynamic temperature compensation unit in the first embodiment of the present application;

[0047] Figure 4 This is a switching logic diagram of the intelligent switching control unit in the first embodiment of the present application;

[0048] Figure 5 This is a structural block diagram of a multilayer printed circuit board in the first embodiment of the present application;

[0049] Figure 6 This is a structural block diagram of the fusion control unit in the second embodiment of the present application;

[0050] Figure 7 This is a control logic diagram of the fusion control unit in the second embodiment of this application. DETAILED DESCRIPTION

[0051] Two implementation modes of the present application are described in detail below with reference to the accompanying drawings.

[0052] The first implementation method:

[0053] Figure 1-Figure 5 A small frequency source module with low phase noise is shown, including:

[0054] The dual-redundant reference source unit includes a main reference source module and a backup reference source module. The main reference source module is integrated with a main temperature sensor, and the backup reference source module is integrated with a secondary temperature sensor. Both the main reference source module and the backup reference source module use a MEMS resonator (micro-electromechanical system resonator) with a Q value (quality factor) of not less than 10,000. The fundamental frequency of the MEMS resonator is 10 MHz to 26 MHz. When the reference temperature is 25°C, the frequency temperature coefficient within the temperature range of -40°C to 85°C is ±0.5 ppm / °C. The MEMS resonator has the advantages of small size and high Q value, and supports I 2 C digital interface, which facilitates temperature compensation control, such as Murata's XRCGB series MEMS resonators;

[0055] A dynamic temperature compensation unit, comprising a first temperature compensation module, a second temperature compensation module, and a data storage module, for dynamically adjusting the output frequency of the resonator according to the temperature, wherein the primary temperature sensor and the secondary temperature sensor are respectively connected to the first temperature compensation module and the second temperature compensation module by signal, and the first temperature compensation module and the second temperature compensation module are respectively connected to the primary reference source module and the backup reference source module by signal;

[0056] A frequency synthesis unit, including a phase-locked loop, is used to multiply the compensated reference frequency to the target output frequency. The phase-locked loop receives the compensation signal through a digital tuning interface or a pre-tuning interface, adjusts the frequency division ratio to lock the target frequency, and outputs a low-phase-noise RF signal.

[0057] The intelligent switching control unit includes a switching control module and a MEMS switch (micro-electromechanical system switch), which is used to control the switching between the main reference source module and the backup reference source module. The switching control module monitors the output frequency of the main reference source module in real time.

[0058] Before the frequency source module leaves the factory, the calibration coefficients are generated and written into the data storage module through the following process:

[0059] Place the frequency source module in an incubator and stabilize it at -40°C, 0°C, 25°C, and 85°C for 2 hours.

[0060] Use a spectrum analyzer to measure the output frequency of the MEMS resonator at each temperature point and calculate the offset relative to the nominal frequency;

[0061] The temperature-frequency curve is fitted by the least squares method to generate the calibration coefficients and write them into the data storage module.

[0062] The dynamic temperature compensation logic of the dynamic temperature compensation unit is:

[0063] The temperature compensation module monitors the temperature T of the reference source module in real time through a temperature sensor, obtains the calibration coefficient K(T) corresponding to the temperature T from the data storage module, and calculates the frequency offset Δf = K(T)·(T-T0), where T0 is the nominal temperature of 25°C.

[0064] The temperature compensation module sends an adjustment voltage to the phase-locked loop to adjust the frequency division ratio of the phase-locked loop so that the compensated output frequency f_out=f_nominal+Δf, where f_nominal is the target nominal frequency.

[0065] The switching logic of the intelligent switching control unit is:

[0066] The switching control module monitors the output frequency f_main of the main reference source module at a sampling frequency of 10 Hz and calculates the absolute value of the deviation between the output frequency f_main and the nominal frequency f_nominal: Δf_main = |f_main-f_nominal|;

[0067] When Δf_main>1ppm, the switching control module controls the MEMS switch to switch from the main reference source module to the backup reference source module within 1μs;

[0068] When Δf_main≤0.5ppm for 10s, it is determined that the main reference source module has returned to normal, and the switching control module controls the MEMS switch to switch from the backup reference source module back to the main reference source module.

[0069] When the main reference source module is working normally, the backup reference source module is in a low-power standby state with a power consumption of ≤1mW.

[0070] This application uses a MEMS resonator with a Q value ≥ 10000, which is not only small in size and can meet the needs of miniaturization, but also its high Q value characteristic itself greatly reduces the intrinsic noise of the resonator; in addition, one of the core sources of phase noise is the drift of the resonator output frequency (especially the temperature drift caused by temperature changes). In this application, the dynamic temperature compensation unit uses a closed-loop mechanism of "calibration-monitoring-correction" to offset the influence of temperature on the resonator frequency in real time, and control the frequency drift caused by temperature within an extremely small range, which not only significantly reduces the temperature drift, but also significantly reduces the phase noise caused by temperature drift; and the dual redundant reference source unit in this application uses the "master-standby collaboration + fast switching" mechanism to avoid the deterioration of phase noise caused by performance fluctuations or failures of a single reference source, which not only further reduces the phase noise, but also effectively avoids the risk of single point failure;

[0071] Therefore, this application solves the problems of large size, high phase noise, large temperature drift and low reliability of traditional frequency source modules through the collaborative design of high-Q value MEMS resonators, dynamic temperature compensation and dual redundant intelligent switching, and realizes a miniaturized design that can meet the stringent requirements of miniaturization in scenarios such as communication equipment and navigation systems.

[0072] The frequency source module also includes a structural protection unit, which includes a shielding cover and a multi-layer PCB (printed circuit board). The shielding cover is made of aluminum alloy and has a thermal conductive silicone pad attached to the bottom.

[0073] The specific interlayer structure of a multi-layer PCB is:

[0074] Bottom layer: power plane, copper thickness 35μm, surface coated with solder mask;

[0075] The second layer: ground plane, with a copper thickness of 35μm, connected to the bottom layer through a via array;

[0076] The third layer: RF signal layer, microstrip line width 0.5mm, surface coated with solder mask;

[0077] Top layer: control signal layer, differential line spacing 0.2mm, surface coated with solder mask;

[0078] The aluminum alloy shielding cover not only provides electromagnetic shielding, but also quickly conducts heat from the module to the outside through the thermally conductive silicone pad to dissipate heat, avoiding performance drift caused by high temperature. The optimized design of the multi-layer PCB power / ground plane and RF / control signal layer can effectively reduce signal crosstalk and power supply noise, improving the module's robustness in complex electromagnetic environments.

[0079] Second implementation method:

[0080] See also Figure 6 and Figure 7 Different from the first embodiment, the frequency source module also includes a fusion control unit, which includes a thermometer transformer module and a control decision module. The main temperature sensor is signal-connected to the thermometer transformer module, the thermometer transformer module is signal-connected to the control decision module, and the control decision module is signal-connected to the switching control module.

[0081] The regulatory logic of the fusion regulatory unit includes:

[0082] The temperature sensor module collects the temperature Tmain of the main reference source module at a frequency of 10Hz through the main temperature sensor and transmits it to the control decision module in real time;

[0083] When T 主When the temperature is higher than 85℃, the control decision module sends a switching signal to the switching control module, so that the switching control module controls the MEMS switch to switch from the main reference source module to the backup reference source module within 1μs;

[0084] When T 主 After the temperature drops to ≤70°C, it is determined that the main reference source module has returned to normal. The control decision module sends a switchback signal to the switch control module, so that the switch control module controls the MEMS switch to switch back from the backup reference source module to the main reference source module.

[0085] The control logic of the fusion control unit also includes:

[0086] The temperature sensor module calculates the temperature change rate dT / dt of the main reference source module through differential calculation based on Tmain and transmits it to the control decision module in real time;

[0087] When dT / dt>5℃ / s, the control decision module sends a switching signal to the switching control module, so that the switching control module controls the MEMS switch to switch from the main reference source module to the backup reference source module within 1μs;

[0088] When dT / dt≤1℃ / s for 10s and T 主 If the temperature is ≤85℃, it is determined that the main reference source module has returned to normal, and the regulation and decision module sends a switchback signal to the switch control module, so that the switch control module controls the MEMS switch to switch back from the backup reference source module to the main reference source module.

[0089] The fusion control unit deeply integrates the dynamic temperature compensation mechanism (dynamic temperature compensation unit) and the dual-redundant intelligent switching mechanism (intelligent switching control unit), and builds a full-link closed-loop management system of "temperature monitoring-compensation adjustment-risk warning-redundant switching", realizing a leap-forward upgrade from "single temperature drift compensation" to "active prevention and control of temperature risks + performance redundancy + thermal redundancy". This integration not only improves the reliability and stability of the module in complex environments, but also further optimizes the phase noise performance, and ultimately improves the reliability and long-term stability of the frequency source module in the entire temperature range and complex working conditions.

[0090] In view of current actual needs, the protection scope of the above-mentioned implementation mode adopted in this application is not limited to this. Various changes made within the knowledge scope of technical personnel in this field without departing from the concept of this application still fall within the protection scope of the present invention.

Claims

1. A small frequency source module with low phase noise, characterized in that: include: A dual-redundant reference source unit, comprising a main reference source module and a backup reference source module, wherein both the main reference source module and the backup reference source module adopt a micro-electromechanical system resonator with a Q value of not less than 10,000; A dynamic temperature compensation unit, comprising a first temperature compensation module, a second temperature compensation module and a data storage module, for dynamically adjusting the output frequency of the resonator according to the temperature; a frequency synthesis unit, including a phase-locked loop, for multiplying the compensated reference frequency to a target output frequency; An intelligent switching control unit, comprising a switching control module and a micro-electromechanical system switch, for controlling the switching between the main reference source module and the backup reference source module; Structural protection unit, including shielding cover and multi-layer printed circuit board; The main reference source module is integrated with a main temperature sensor, and the backup reference source module is integrated with a secondary temperature sensor. The main temperature sensor and the secondary temperature sensor are respectively connected to the first temperature compensation module and the second temperature compensation module by signal. The first temperature compensation module and the second temperature compensation module are respectively connected to the main reference source module and the backup reference source module by signal. The switching control module monitors the output frequency of the main reference source module in real time.

2. A small frequency source module with low phase noise according to claim 1, characterized in that: The fundamental frequency of the MEMS resonator is 10 MHz to 26 MHz. When the reference temperature is 25° C., the frequency temperature coefficient thereof is ±0.5 ppm / ° C. within the temperature range of -40° C. to 85° C.

3. A small frequency source module with low phase noise according to claim 2, characterized in that: Before the frequency source module leaves the factory, the calibration coefficients are generated and written into the data storage module through the following process: Place the frequency source module in an incubator and stabilize it at -40°C, 0°C, 25°C, and 85°C for 2 hours. The output frequency of the MEMS resonator at each temperature point is measured using a spectrum analyzer, and the offset relative to the nominal frequency is calculated. The temperature-frequency curve is fitted by the least squares method to generate the calibration coefficients and write them into the data storage module.

4. A small frequency source module with low phase noise according to claim 3, characterized in that: The dynamic temperature compensation logic of the dynamic temperature compensation unit is: The temperature compensation module monitors the temperature T of the reference source module in real time through a temperature sensor, obtains the calibration coefficient K(T) corresponding to the temperature T from the data storage module, and calculates the frequency offset Δf = K(T)·(T-T0), where T0 is the nominal temperature of 25°C. The temperature compensation module sends an adjustment voltage to the phase-locked loop to adjust the frequency division ratio of the phase-locked loop so that the compensated output frequency f_out=f_nominal+Δf, where f_nominal is the target nominal frequency.

5. A small frequency source module with low phase noise according to claim 4, characterized in that: The switching logic of the intelligent switching control unit is: The switching control module monitors the output frequency f_main of the main reference source module at a sampling frequency of 10 Hz and calculates the absolute value of the deviation between the output frequency f_main and the nominal frequency f_nominal: Δf_main = |f_main-f_nominal|; When Δf_main>1ppm, the switching control module controls the MEMS switch to switch from the main reference source module to the backup reference source module within 1μs; When Δf_main≤0.5ppm for 10s, it is determined that the main reference source module has returned to normal, and the switching control module controls the MEMS switch to switch from the backup reference source module back to the main reference source module.

6. The small frequency source module with low phase noise according to claim 5, characterized in that: When the main reference source module operates normally, the backup reference source module is in a low-power standby state with a power consumption of ≤1 mW.

7. A small frequency source module with low phase noise according to claim 6, characterized in that: It also includes a fusion control unit, which includes a temperature sensor module and a control decision module. The main temperature sensor is signal-connected to the temperature sensor module, the temperature sensor module is signal-connected to the control decision module, and the control decision module is signal-connected to the switching control module.

8. The small frequency source module with low phase noise according to claim 7, characterized in that: The control logic of the fusion control unit includes: The temperature sensor module collects the temperature T of the main reference source module at a frequency of 10Hz. 主 And transmit it to the control decision module in real time; When T 主 When the temperature is higher than 85℃, the control decision module sends a switching signal to the switching control module, so that the switching control module controls the MEMS switch to switch from the main reference source module to the backup reference source module within 1μs; When T 主 After the temperature reaches ≤70℃, it is determined that the main reference source module has returned to normal, and the regulation and decision module sends a switchback signal to the switch control module, so that the switch control module controls the micro-electromechanical system switch to switch back from the backup reference source module to the main reference source module.

9. The small frequency source module with low phase noise according to claim 8, characterized in that: The control logic of the fusion control unit also includes: Thermometer module changes according to T 主 The temperature change rate dT / dt of the main reference source module is obtained by differential calculation and transmitted to the control decision module in real time; When dT / dt>5℃ / s, the control decision module sends a switching signal to the switching control module, so that the switching control module controls the micro-electromechanical system switch to switch from the main reference source module to the backup reference source module within 1μs; When dT / dt≤1℃ / s for 10s and T 主 If the temperature is ≤85℃, it is determined that the main reference source module has returned to normal, and the regulation and decision module sends a switchback signal to the switch control module, so that the switch control module controls the micro-electromechanical system switch to switch from the backup reference source module back to the main reference source module.

10. The small frequency source module with low phase noise according to claim 1, characterized in that: The shielding cover is made of aluminum alloy, and a thermal conductive silicone pad is attached to the bottom; The specific interlayer structure of the multilayer printed circuit board is: Bottom layer: power plane, copper thickness 35μm, surface coated with solder mask; The second layer: ground plane, with a copper thickness of 35μm, connected to the bottom layer through a via array; The third layer: RF signal layer, microstrip line width 0.5mm, surface coated with solder mask; Top layer: control signal layer, differential line spacing 0.2mm, surface coated with solder mask.

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