CN111007710B

CN111007710B - Production line calibration method, device and system of equipment clock, self-calibration method and equipment

Info

Publication number: CN111007710B
Application number: CN201911368213.9A
Authority: CN
Inventors: 元恒敏
Original assignee: Spreadtrum Communications Shanghai Co Ltd
Current assignee: Spreadtrum Communications Shanghai Co Ltd
Priority date: 2019-12-26
Filing date: 2019-12-26
Publication date: 2022-01-04
Anticipated expiration: 2039-12-26
Also published as: CN111007710A

Abstract

A production line calibration method, device and system, a self-calibration method and equipment of an equipment clock are provided, the equipment comprises a TSXO and a Bluetooth module, wherein the production line calibration method of the equipment clock comprises the following steps: eliminating the self-carried frequency offset of the TSXO through the Bluetooth module; calibrating a temperature drift of the TSXO. By the method, a clock scheme with a positioning function, which is low in cost and high in precision, can be provided for the universal connection device.

Description

Production line calibration method, device and system of equipment clock, self-calibration method and equipment

Technical Field

The invention relates to the field of clock calibration of intelligent equipment, in particular to a production line calibration method, a production line calibration device and a production line calibration system of an equipment clock, and a self-calibration method and equipment.

Background

In the current society, mobile phone products and internet of things technology are being developed vigorously, while the development of the internet of things is not away from the intelligent Positioning technology, and currently, a Global Positioning module (GPS for short) is mostly used for intelligent Positioning. Universal connection devices for mobile communication, such as mobile phones, computers, etc., are generally equipped with a mobile connection module (connection) and a Global Positioning module (GPS). The mobile connection module may include a BlueTooth module (BT for short) or a Wireless-Fidelity (WIFI for short).

For the GPS module, there are two common clock sources: one is that it has a Temperature compensated crystal Oscillator (TCXO) or crystal resonator (crystal resonator) to provide its clock; and the other clock from the mobile phone communication module is a shared clock. For the internet of things module with the positioning function, the existing mainstream external clock source mainly adopts two types of TCXO and crystal resonance. Among them, the crystal resonator is cheap, but its frequency will shift with temperature, the typical temperature shift is +/-10ppm, besides the temperature shift, there is +/-10ppm difference between different crystal oscillator sample wafers at the same temperature. The TCXO is a crystal oscillator internally integrated with a temperature compensation circuit, and after temperature compensation, the typical temperature drift range of the TCXO is +/-0.5ppm to +/-2 ppm. Due to the extremely high frequency accuracy requirement of the GPS, only the TCXO can be used for the module with the GPS itself.

The external clock source adopted by the existing clock scheme of the internet of things module with the positioning function generally has two types: a but the Temperature Compensated active Oscillator of Voltage control frequency (VC-TCXO) or TCXO of price, precision, stability all are higher, because the Temperature compensating circuit is incorporated in VC-TCX/TCXO assembly through controlling the Voltage of the varactor diode or adopting the Temperature sensing compensating network to form a reverse compensating Voltage, in order to adjust or offset the Crystal itself and produce and drift by the Temperature influence, thus improve the Temperature stability of the Crystal Oscillator, so its precision can reach +/-0.5 ppm- +/-2ppm, meet the demand of GPS, but its cost is higher.

The other one adopts a digital-compensated Crystal Oscillator (DCXO), and a temperature compensation circuit is additionally provided. The DCXO has a lower cost than the VC-TCXO/TCXO, but because the DCXO itself has no frequency adjustment mechanism, static and dynamic frequency errors need to be solved, the static error can be generally adjusted through a calibration procedure, but the dynamic error, that is, the frequency drift along with the temperature change is difficult to be solved, and particularly, it is difficult to accurately obtain the real-time frequency offset corresponding to the current temperature, so that the device at the client cannot be located to the satellite due to too large frequency offset at the extreme temperature.

Disclosure of Invention

The invention solves the technical problem of how to provide a clock scheme with a positioning function for the universal connection equipment, wherein the clock scheme has lower cost and higher precision.

The embodiment of the application provides a production line calibration method of a device clock, wherein the device comprises a TSXO (time sequence identification) and a Bluetooth module, and the method comprises the following steps: eliminating the self-carried frequency offset of the TSXO through the Bluetooth module; calibrating a temperature drift of the TSXO; the eliminating the self-carried frequency offset of the TSXO through the Bluetooth module comprises the following steps: transmitting a first modulated signal, the first modulated signal being received by the Bluetooth module; adjusting a capacitance array value of an oscillation circuit of the TSXO through the Bluetooth module to generate local oscillator signals with different frequencies, calculating frequency deviation of each local oscillator signal and the first modulation signal, and acquiring the capacitance array value when the frequency deviation is a preset value; and storing the capacitance array value when the frequency deviation is a preset value into the equipment.

Optionally, the bluetooth module includes a mixer, and the calculating frequency offset between each local oscillator signal and the first modulation signal includes: mixing the first modulation signal and each local oscillation signal through the frequency mixer to obtain a first mixing signal corresponding to each local oscillation signal; and calculating the frequency offset corresponding to each local oscillation signal according to the first mixing signal.

Optionally, the calculation formula of the first mixing signal is: f. of_I＝f_L±f_C(ii) a Wherein f is_CFor the first modulation signal, f_LIs the local oscillator signal, f_IIs the first mixing signal.

Optionally, the preset value is a value with a minimum absolute value.

Optionally, the device further includes a WIFI module, and the calibrating the temperature drift of the TSXO includes: transmitting a second modulated signal, the second modulated signal being received by the Bluetooth module; heating the TSXO through the WIFI module, and collecting at least four temperatures; acquiring frequency offset corresponding to each temperature according to the second modulation signal through the Bluetooth module; storing the at least four temperatures and the frequency offset corresponding to each temperature in the apparatus.

Optionally, the obtaining, according to the second modulation signal, a frequency offset corresponding to each temperature includes: for each temperature, acquiring a local oscillation signal of the TSXO at the temperature; respectively mixing the second modulation signal and the local oscillator signal at each temperature through a mixer of the Bluetooth module to obtain a second mixing signal at each temperature; and calculating the frequency offset at each temperature according to the second mixing signal.

Optionally, the at least four temperatures are four temperatures with different values, the TSXO is warmed by the WIFI module, and the at least four temperatures are collected, including: acquiring a first temperature before the TSXO is warmed up; heating the TSXO through the WIFI module, and collecting a second temperature and a third temperature in the heating process; and stopping heating the TSXO, and collecting a fourth temperature in the cooling process.

Optionally, the TSXO includes a thermistor, and the acquiring at least four temperatures includes: a resistor with a preset resistance value is connected in series with the TSXO, and the resistor with the preset resistance value and the TSXO form a voltage division circuit; collecting at least four voltage values at two ends of the TSXO according to the voltage division circuit; and calculating the corresponding resistance value of the thermistor according to the at least four voltage values, and obtaining the at least four temperatures according to the corresponding relation between the resistance value of the thermistor and the temperatures.

Optionally, the TSXO includes a crystal and an oscillator, and the at least four voltage values are voltages across the crystal, and the method further includes: collecting voltage values of a thermal diode inside the oscillator while collecting at least four temperatures of the crystal; obtaining at least two temperatures of the oscillator according to the voltage value of a thermal diode in the oscillator; storing at least two temperatures of the oscillator in correspondence with at least four temperatures of the crystal in the device.

The embodiment of the present application further provides a clock self-calibration method of a device, where the device includes a TSXO and a bluetooth module, and the method includes: and reading a capacitance array value when the frequency deviation is a preset value from the equipment, and setting a capacitance array of an oscillation circuit of the TSXO according to the capacitance array value.

Optionally, the method further includes: reading at least four temperatures and frequency deviation corresponding to each temperature; obtaining a first temperature drift theoretical formula, and substituting the at least four temperatures and the frequency offset corresponding to each temperature into the first temperature drift theoretical formula to obtain a temperature drift formula of the TSXO; acquiring the real-time working temperature of the TSXO, and acquiring the frequency offset corresponding to the real-time working temperature according to the temperature drift formula of the TSXO; compensating the frequency deviation by utilizing a GPS module; wherein, the first temperature drift theoretical formula is as follows: f ═ c3 ^ (t-t0) ^3+ c2 ^ (t-t0) ^2+ c1 ^ (t-t0) + c 0; wherein, F is the frequency offset of the TSXO at the temperature t, the variable t is the temperature, t0 is the reference temperature, and c0, c1, c2 and c3 are constants in the temperature system.

Optionally, the TSXO includes a crystal and an oscillator, and the method further includes: reading at least two temperatures of the oscillator and at least four temperatures of the crystal; acquiring a second temperature drift theoretical formula, and inputting at least two temperatures of the oscillator and at least four temperatures of the crystal into the second temperature drift formula to obtain a temperature drift formula of the TSXO; acquiring the real-time working temperature of the TSXO, and acquiring the frequency offset corresponding to the real-time working temperature according to the temperature drift formula of the TSXO; compensating the frequency deviation by utilizing a GPS module;

wherein, the second temperature drift theoretical formula is as follows: f (t)_t,t_o)＝c3_t*(t_t-t0)^3+c2_t*(t_t-t0)^2+c1_t*(t_t-t0)+c0_t+c0_o+c1_o*(t_o-t 0); wherein, F (t)_t,t_o) For frequency deviation of the oscillating circuit, variable t_tIs the temperature of TSXO, t_oIs the temperature of the oscillator, t0 is the reference temperature, c0_t、c1_t、c2_tAnd c3_tConstant of TSXO in temperature systems, c0_o、c1_oIs a constant of the oscillator in the temperature system.

The embodiment of the application further provides a production line calibration system of the equipment clock, which is characterized by comprising a test instrument, a control end and equipment, wherein the control end is respectively connected with the test instrument and the equipment to control the test instrument and the equipment; the test instrument is used for sending a first modulation signal; the device comprises a TSXO and a Bluetooth module, and is used for adjusting the capacitance array value of an oscillating circuit of the TSXO by using the Bluetooth module to generate local oscillator signals with different frequencies, calculating the frequency deviation of each local oscillator signal and the first modulation signal, acquiring the capacitance array value when the frequency deviation is a preset value, and storing the capacitance array value when the frequency deviation is the preset value.

The embodiment of the present application further provides a terminal, which includes a memory and a processor, where the memory stores computer instructions capable of running on the processor, and the processor executes the steps of the clock self-calibration method of any one of the above devices when executing the computer instructions.

Compared with the prior art, the technical scheme of the embodiment of the invention has the following beneficial effects:

the device clock production line calibration method provided by the embodiment of the invention comprises a TSXO (time sequence identification) and a Bluetooth module, and the method comprises the following steps: eliminating the self-carried frequency offset of the TSXO through the Bluetooth module; calibrating a temperature drift of the TSXO; the eliminating the self-carried frequency offset of the TSXO through the Bluetooth module comprises the following steps: transmitting a first modulated signal, the first modulated signal being received by the Bluetooth module; adjusting a capacitance array value of an oscillation circuit of the TSXO through the Bluetooth module to generate local oscillator signals with different frequencies, calculating frequency deviation of each local oscillator signal and the first modulation signal, and acquiring the capacitance array value when the frequency deviation is a preset value; and storing the capacitance array value when the frequency deviation is a preset value into the equipment. Compared with the prior art, the TCXO in the equipment is replaced by the TSXO, so that the cost is reduced. And through producing line calibration, overcome TSXO's output frequency and receive the influence of temperature variation for equipment provides accurate clock signal, makes GPS module pinpoint according to clock signal.

Furthermore, a Bluetooth module carried by the device receives the first modulation signal, frequency calibration is carried out on the GPS module containing the TSXO according to the first modulation signal, and before the device leaves a factory, calibration is carried out on a clock signal of the device. The calibration comprises two parts of eliminating self-carried frequency offset of the TSXO and dynamically eliminating frequency drift generated by the TSXO according to temperature change. By adopting the scheme, the frequency error caused by the inaccuracy of the local oscillation signal of the TSXO or the influence of the environmental temperature can be avoided, so that the clock signal of the equipment is kept stable, and the accurate positioning is realized.

Furthermore, the bluetooth module calculates the frequency offset between each local oscillator signal and the first modulation signal by mixing the local oscillator signal and the first modulation signal through a mixer in the bluetooth module to obtain a first mixing signal, and further obtain a frequency offset value between the local oscillator signal and the first modulation signal.

Furthermore, before the equipment leaves the factory, the temperature drift of the TSXO is calibrated by a production line, at least four temperatures and frequency offset values corresponding to each temperature are obtained and stored in a memory of the equipment, so that the frequency offset generated by the temperature drift of the crystal can be automatically eliminated according to the change of the temperature after the equipment leaves the factory, dynamic frequency errors are eliminated, the clock frequency of the equipment is not affected by the frequency offset of the TSXO when the environmental temperature changes, and the accurate positioning of the GPS is ensured.

Drawings

Fig. 1 is a schematic flowchart of a clock calibration method of a device according to an embodiment of the present disclosure;

fig. 2 is a schematic structural diagram of an oscillation circuit of a TSXO according to an embodiment of the present disclosure;

FIG. 3 is a schematic flowchart of step S12 in FIG. 1;

FIG. 4 is a circuit diagram of calibrating a device clock according to an embodiment of the present application;

FIG. 5 is a flow chart illustrating a method for line calibration of a device clock in an exemplary application;

FIG. 6 is a schematic flow chart illustrating a temperature drift self-calibration procedure according to an embodiment of the present application;

fig. 7 is a schematic diagram of a production line calibration system of an apparatus clock according to an embodiment of the present application.

Detailed Description

According to the background art, the clock source of the existing GPS module is TCXO or DCXO, where TCXO is costly; and the DCXO cannot solve a dynamic error generated by frequency drift along with temperature change, so that the GPS module is inaccurate in positioning.

Aiming at the problems, a Temperature Sensor Crystal Oscillator (TSXO for short) can be adopted to provide a clock for the equipment, the difference between the TSXO and a common Crystal Oscillator (TSXO) is that the TSXO internally comprises a Temperature Sensor which is a thermistor or a Temperature diode, meanwhile, the TSXO does not perform closed-loop feedback control on the output frequency like the TCXO, the output frequency of the TSXO is not subjected to Temperature compensation, and the frequency output by the TSXO is greatly influenced by the Temperature. However, the clock corresponding to the crystal oscillator is required to be accurate as the reference clock of the whole equipment system, which requires that, for example, the 26MHz crystal oscillator strictly operates at 26MHz, so that other systems can normally and orderly operate.

In order to solve the above technical problem, the present application provides a clock production line calibration method for a device, where the device includes a TSXO and a bluetooth module, and the method includes: eliminating the self-carried frequency offset of the TSXO through the Bluetooth module; calibrating a temperature drift of the TSXO; the eliminating the self-carried frequency offset of the TSXO through the Bluetooth module comprises the following steps: transmitting a first modulated signal, the first modulated signal being received by the Bluetooth module; adjusting a capacitance array value of an oscillating circuit of the TSXO through the Bluetooth module to generate local oscillator signals with different frequencies, calculating frequency deviation of each local oscillator signal and the first modulation signal, and acquiring the capacitance array value when the frequency deviation is a preset value; and storing the capacitance array value when the frequency deviation is a preset value into the equipment.

The scheme replaces the TCXO in the equipment with the TSXO so as to reduce the cost. And through producing line calibration, overcome TSXO's output frequency and receive the influence of temperature variation for equipment provides accurate clock signal, makes GPS module pinpoint according to clock signal.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

Referring to fig. 1, fig. 1 is a schematic flow chart illustrating a method for calibrating a production line of a device clock; the method may specifically include the following steps S11 and S12. Wherein:

and step S11, eliminating the self-carried frequency offset of the TSXO through the Bluetooth module.

The self-contained frequency offset is the frequency offset between the output frequency of the TSXO and the expected clock signal at normal temperature. Since all devices cannot guarantee strict consistency, the crystal oscillators from the factory have individual differences and the influence of welding and loads on single boards, the crystal oscillator source on each device needs to be corrected.

The device can be calibrated before leaving the factory according to the matching of the Bluetooth module of the device and the GPS module hung with the TSXO on a production line. The clock signal of the equipment is obtained according to the local oscillation signal generated by the TSXO oscillation, the local oscillation signal of the TSXO oscillation can be detected according to the Bluetooth module of the equipment, so that the self-frequency deviation between the oscillation frequency of the local oscillation signal of the crystal oscillator and the oscillation frequency of the clock signal expected to be obtained is obtained, the self-frequency deviation is calibrated, the accurate clock signal is obtained, and the clock calibration before factory shipment is realized.

And step S12, calibrating the temperature drift of the TSXO.

In addition, because the frequency of the Crystal (Crystal) in the TSXO drifts with the temperature change, the frequency error caused by the temperature change needs to be calibrated accordingly, so that the clock signal of the device is not affected by the ambient temperature of the device, thereby ensuring the normal positioning of the GPS module.

In step S11, the elimination of the self-contained frequency offset of the TSXO through the bluetooth module may specifically include the following steps S111 to S113:

and S111, transmitting a first modulation signal, wherein the first modulation signal is received by the Bluetooth module.

The first modulation signal is a comparison signal used for carrying out frequency offset elimination on a local oscillation signal of the TSXO, is obtained according to a clock signal of normal work of equipment, and can be set as required. The frequency of the clock signal may be equal to the oscillation frequency corresponding to the clock signal in which the device normally operates, or a preset difference may exist between the oscillation frequency and the oscillation frequency corresponding to the clock signal in which the device normally operates.

Alternatively, the first modulation signal may be transmitted by a dedicated test instrument, and the test may be controlled by a control terminal performing a clock calibration method of the device to set the frequency of the first modulation signal. For example, the test instrument may be allowed to transmit a single-tone modulation signal, i.e., a first modulation signal, with a frequency of 2402MHz at a certain frequency point in the 2.4GHz band through the external antenna.

The bluetooth module of the device can receive the first modulation signal, and the first modulation signal is used as a comparison signal to perform frequency offset calibration on the local oscillation signal of the TSXO.

And S112, adjusting the capacitance array value of the oscillation circuit of the TSXO through the Bluetooth module to generate local oscillation signals with different frequencies, calculating the frequency offset of each local oscillation signal and the first modulation signal, and acquiring the capacitance array value when the frequency offset is a preset value.

Referring to fig. 2, fig. 2 is a schematic diagram of an oscillating circuit of a TSXO; the system clock is generated through an oscillation circuit, the whole oscillation circuit is composed of a crystal and an oscillator, the oscillator comprises a capacitor array, a plurality of capacitors b1, b2, … and bn are arranged in the oscillator, each capacitor corresponds to a switch, the capacitance value (called as a capacitor array value in the application) of the capacitor array can be changed by adjusting the switches of the capacitors in the capacitor array, and the clock calibration principle is that the accurate output of the system clock is adjusted by changing the load capacitance in a crystal oscillator resonance circuit, so that the local oscillation signal of the TSXO is adjusted, and the calibration purpose is achieved.

Under the control through setting up bluetooth module for bluetooth module can adjust the capacitance array value in TSXO's oscillating circuit, so that TSXO's local oscillator signal changes, and calculate the frequency offset between local oscillator signal and the first modulation signal through bluetooth module, thereby make local oscillator signal can produce the local oscillator signal that carries out the accurate positioning for the GPS module.

Wherein the preset value is varied according to the variation of the first modulation signal. When the frequency of the first modulation signal is equal to the oscillation frequency corresponding to the clock signal of the normal work of the equipment, the preset value is 0 or is as close to 0 as possible; when a preset difference exists between the frequency of the first modulation signal and the oscillation frequency corresponding to the clock signal of the device working normally, the preset value should be equal to or as close as possible to the preset difference.

S113, storing the capacitance array value when the frequency deviation is a preset value into the device.

And storing the capacitance array value obtained in the step S112 in the memory of the device, so that the device can automatically obtain the capacitance array value when being started, thereby generating a local oscillation signal when the GPS works normally.

In the above embodiment, the bluetooth module of the device receives the first modulation signal, and performs frequency calibration on the GPS module including the TSXO according to the first modulation signal, and calibrates the clock signal of the device before the device leaves the factory. The calibration comprises the elimination of the self-frequency offset of the TSXO and the dynamic elimination of the frequency drift of the crystal oscillator generated according to the temperature change. Therefore, frequency errors caused by inaccuracy of local oscillation signals of the TSXO or influence of ambient temperature can be avoided, clock signals of the equipment are kept stable, and accurate positioning is achieved.

In one embodiment, the bluetooth module includes a mixer. Referring to fig. 1, the step S112 in fig. 1 of calculating the frequency offset between each local oscillator signal and the first modulation signal may include: mixing the first modulation signal and each local oscillation signal through the frequency mixer to obtain a first mixing signal corresponding to each local oscillation signal; and calculating the frequency offset corresponding to each local oscillation signal according to the first mixing signal.

The Bluetooth module of the device comprises a frequency mixer, and the frequency mixer can be used for calculating the frequency offset of the local oscillator signal and the first modulation signal, namely, the local oscillator signal and the first modulation signal are mixed by the frequency mixer to obtain a mixed signal, namely, the first mixed signal. The first modulation signal received by the bluetooth module may be in the same direction or opposite direction to the local oscillator signal, and the frequency mixer may be used to adjust the phase difference between the first modulation signal and the local oscillator signal, so as to calculate the frequency difference between the first modulation signal and the local oscillator signal, thereby obtaining the frequency offset between the first modulation signal and the local oscillator signal.

In this embodiment, the manner of calculating the frequency offset between each local oscillator signal and the first modulation signal by the bluetooth module is to obtain a first mixing signal after mixing the local oscillator signal and the first modulation signal by a mixer in the bluetooth module, and further obtain a frequency offset value between the local oscillator signal and the first modulation signal.

Optionally, the calculation formula of the first mixing signal is as follows:

f_I＝f_L±f_C；

wherein f is_CFor the first modulation signal, f_LIs the local oscillator signal, f_IIs the first mixing signal.

When the first modulation signal and the local oscillation signal are in the same direction, calculating the frequency difference value of the first modulation signal and the local oscillation signal to obtain a corresponding frequency offset value; when the first modulation signal and the local oscillation signal are opposite to each other, the sum of the frequencies of the first modulation signal and the local oscillation signal can be calculated to obtain the corresponding frequency offset.

Optionally, the frequency of the first modulation signal may be set to be equal to an oscillation frequency corresponding to a clock signal for normal operation of the device. The preset value is a value with the smallest absolute value at this time, even if the frequency of the local oscillation signal is as close as possible to the frequency of the first modulation signal.

In an embodiment, the apparatus may further include a WIFI module, please refer to fig. 3, fig. 3 provides a flowchart of step S12 in fig. 1, and the calibrating the temperature drift of the TSXO in step S12 may include:

and S121, transmitting a second modulation signal, wherein the second modulation signal is received by the Bluetooth module.

The second modulation signal is a comparison signal used for carrying out frequency offset elimination on a local oscillation signal of the TSXO when the temperature changes; also derived from the clock signal at which the device is operating normally, and may be the same as or different from the first modulated signal.

During the temperature drift calibration process for the TSXO, a second modulation signal for frequency comparison during calibration is also received by the bluetooth module.

And S122, heating the TSXO through the WIFI module, and collecting at least four temperatures.

Carry out the power amplifier through controlling the WIFI module and send out by force, heat up TSXO to the change of ambient temperature in the simulation use, and gather 4 at least different temperatures, with the frequency deviation between the oscillation frequency of detecting crystal oscillator under each temperature and its normal atmospheric temperature. For example, emission at 5G (if there is 5G) and 2.4G at High (High) power acts as a warm-up accelerator.

Step S123, obtaining, by the bluetooth module, a frequency offset corresponding to each temperature according to the second modulation signal.

Similarly, the frequency mixing may be performed on the oscillation signal of the TSXO at each temperature and the second modulation signal according to the frequency mixer of the bluetooth module, so as to obtain the frequency offset between the oscillation frequency of the crystal oscillator at the temperature and the second modulation signal, and thus obtain the frequency offset corresponding to the temperature.

Step S124, storing the at least four temperatures and the frequency offset corresponding to each temperature in the device.

After at least four temperatures and frequency offset values corresponding to the temperatures are sequentially obtained, the temperatures and the frequency offset values are stored in a memory of the equipment, so that the equipment can restore a temperature drift curve of the crystal according to the stored temperatures and the corresponding frequency offsets, so that when the environment temperature changes, the frequency offset corresponding to the TSXO real-time working temperature is obtained according to the temperature drift curve, and the frequency offset is compensated, thereby ensuring that the clock frequency of the equipment is not influenced by the TSXO temperature drift when the environment temperature changes, and ensuring the accuracy of a system clock.

In this embodiment, before the device leaves the factory, a production line calibration is performed on the temperature drift of the TSXO, so as to obtain at least four temperatures and frequency offset values corresponding to each temperature, and the frequency offset values are stored in a memory of the device, so that the frequency offset generated by the crystal temperature drift can be automatically eliminated according to the change of the temperature after the device leaves the factory, a dynamic frequency error is eliminated, it is ensured that the clock frequency of the device is not affected by the frequency offset of the TSXO when the ambient temperature changes, and accurate positioning of the GPS is ensured.

In an embodiment, with continuing reference to fig. 3, the step S123 in fig. 3 of obtaining the frequency offset corresponding to each temperature according to the second modulation signal includes: for each temperature, acquiring a local oscillation signal of the TSXO at the temperature; respectively mixing the second modulation signal and the local oscillator signal at each temperature through a mixer of the Bluetooth module to obtain a second mixing signal at each temperature; and calculating the frequency offset at each temperature according to the second mixing signal.

Specifically, the bluetooth module calculates the frequency offset corresponding to each temperature by mixing the local oscillator signal of the TSXO at each temperature with the received second modulation signal through a mixer in the bluetooth module, and the mixed signal is referred to as a second mixed signal. And calculating the frequency offset between the local oscillation signal and the second modulation signal at the temperature according to the frequency of the second mixing signal so as to obtain the frequency offset generated due to the temperature offset at the temperature.

Optionally, the frequency of the second modulation signal is a frequency of a local oscillation signal when the crystal oscillator operates at normal temperature, and the frequency mixer may calculate a frequency offset corresponding to each temperature according to the following formula:

f_I'＝f_L'±f_C'；

wherein f is_C'Is a second modulation signal, f_L'For local oscillator signal of TSXO at each temperature, f_I'Is the second mixing signal for each temperature. When the second modulation signal and the local oscillation signal are in the same direction, calculating the frequency difference between the second modulation signal and the local oscillation signal to obtain the frequency deviation corresponding to the temperature; when the second modulation signal and the local oscillator signal are opposite to each other, the sum of the frequencies of the second modulation signal and the local oscillator signal can be calculated to obtain the frequency offset corresponding to the temperature.

In this embodiment, the second modulation signal and the local oscillator signal are mixed by the mixer of the bluetooth module to obtain the frequency offset value.

In one embodiment, the at least four temperatures are four temperatures with different values, and the step of warming the TSXO by the WIFI module and collecting the at least four temperatures includes: acquiring a first temperature before the TSXO is warmed up; heating the TSXO through the WIFI module, and collecting a second temperature and a third temperature in the heating process; and stopping heating the TSXO, and collecting a fourth temperature in the cooling process.

In the scheme, the first temperature is collected before temperature rise in four temperatures collected during temperature drift calibration, namely the normal temperature of normal work of the TSXO; the second temperature and the third temperature are collected in the temperature rising process, namely two temperatures in the temperature rising state; the fourth temperature is collected when the temperature is reduced, and the temperature values of the four points are different.

Therefore, four different temperatures of the crystal oscillator in normal temperature, temperature rising and temperature lowering states can be obtained, and the frequency deviation of each temperature can be obtained. Because the temperature drift curve of the crystal in the crystal oscillator can be expressed as a cubic polynomial, the cubic polynomial can be determined according to the four temperatures and the corresponding frequency offsets so as to obtain the temperature drift change curve of the crystal.

In one embodiment, the TSXO contains a thermistor, and the acquiring at least four temperatures includes: a resistor with a preset resistance value is connected in series with the TSXO, and the resistor with the preset resistance value and the TSXO form a voltage division circuit; collecting at least four voltage values at two ends of the TSXO according to the voltage division circuit; and calculating the corresponding resistance value of the thermistor according to the at least four voltage values, and obtaining the at least four temperatures according to the corresponding relation between the resistance value of the thermistor and the temperatures.

The TSXO comprises a thermistor, and the resistance value and the temperature of the thermistor have a preset corresponding relation and are determined by the characteristics of the thermistor. Therefore, the current temperature of the TSXO can be obtained only by obtaining the resistance values of the thermistor at different moments in the temperature rising and temperature reduction processes after temperature rising. Potentiometers can be connected to the two ends of the TSXO to detect the voltage of the TSXO during working, so that the resistance value of the TSXO can be calculated, the resistance value of the thermistor can be obtained, and then the current temperature of the TSXO can be obtained.

In one embodiment, the TSXO includes a crystal and an oscillator, the at least four voltage values being voltages across the crystal, the method further comprising: collecting voltage values of a thermal diode inside the oscillator while collecting at least four temperatures of the crystal; obtaining at least two temperatures of the oscillator according to the voltage value of a thermal diode in the oscillator; storing at least two temperatures of the oscillator in correspondence with at least four temperatures of the crystal in the device.

In particular, a calibration circuit for the device clock may be designed to enable the device to self-calibrate for temperature drift. Referring to fig. 4, fig. 4 is a circuit diagram of calibrating a device clock; the clock source of the device is a TSXO, the TSXO comprises a crystal XO and a thermistor Rt, and in addition, the circuit further comprises an oscillator OSC. The TSXO is connected in parallel with the oscillator OSC, and the TSXO can be equivalent to an inductor and forms an LC parallel resonant circuit with a capacitor array in the oscillator OSC. The capacitance value of the capacitor array in the oscillator circuit OSC is adjusted through calibration to generate a specific frequency so as to obtain a local oscillator signal.

One end of a thermistor Rt of the TSXO of the equipment is connected with a resistor Rs, the resistance value of the resistor Rs is known, and one end of the resistor Rs, which is far away from the thermistor Rt, is connected with an analog-to-digital converter SD-ADC. Connecting the connecting end of the thermistor Rt and the resistor Rs into an input end 0 of a multi-path signal selector MUX; when the oscillator OSC and the thermistor Rt are connected in parallel, one end of the oscillator OSC is connected to the thermistor Rt, and the other end of the oscillator OSC is connected to the input terminal 1 of the multiplexer MUX. The output end of the multi-path signal selector MUX is connected with the analog-to-digital converter SD-ADC. The analog-to-digital converter SD-ADC can acquire different input signals in a time-sharing manner through input ends 0 and 1 of the multi-path signal selector MUX.

Acquiring at least four temperatures of a crystal and frequency deviation corresponding to each temperature by the following steps:

step 1: the input end 0 of the multi-channel signal selector MUX is selected, and the voltage at two ends of the analog-to-digital converter SD-ADC collecting resistor Rs is the voltage difference between two points TSEN _ VREFP and TSEN _ TSX.

Step 2: the analog-to-digital converter SD-ADC converts the voltage collected at the two ends of the resistor Rs into a digital signal and transmits the digital signal to a GPS module of the equipment.

And step 3: the GPS module calculates the voltage at two ends of the Rt according to the known voltage V _ Ref at two ends of the Rs and Rt series circuit, and calculates the resistance value of the thermistor Rt at the moment through the following formula (1).

Wherein V in the formula (1) is the voltage at the two ends of Rt, Rt is the resistance of the thermistor, Rs is the resistance of the resistor Rs, and V _ Ref is the voltage at the two ends when the resistor Rs and the thermistor Rt are connected in series.

And 4, step 4: and the GPS module obtains the working temperature of the thermistor Rt at the moment according to the corresponding relation between the resistance value and the temperature of the thermistor Rt. And the Bluetooth module of the device calculates the frequency offset at the moment.

And 5: and correspondingly storing the temperature obtained by the GPS module and the frequency offset obtained by the Bluetooth module into a memory of the equipment to obtain the temperature and the frequency offset corresponding to the temperature.

Step 6: and changing the working temperature of the equipment, and continuing to execute the steps 1 to 5 to obtain at least 4 temperatures and the frequency offset corresponding to each temperature.

When the input terminal 1 is selected, the analog-to-digital converter SD-ADC collects the voltage across the photodiode in the oscillator OSC, i.e., the voltage difference between the voltage value at the input terminal 1 and two points TSEN _ VREFN. And acquiring at least two temperatures of the oscillator by the same method as the acquiring steps of the temperature of the crystal and the corresponding frequency deviation.

In this embodiment, a calibration circuit of a device clock is provided to collect frequency offset generated by a crystal in a TSXO along with temperature change and frequency offset generated by an oscillator along with temperature change, so as to accurately calculate a temperature drift of the TSXO.

Referring to fig. 5, fig. 5 is a flowchart illustrating a method for calibrating a production line of a device clock in an application example. In the application scenario, before the equipment leaves the factory, the equipment is firstly subjected to clock calibration, and the calibration mode is as follows:

in step S500, calibration is started.

Step S510, self-contained frequency offset cancellation. Specifically, the method comprises steps S511 and S512, wherein:

and step S511, judging whether the self frequency offset of the TSXO can be eliminated through the Bluetooth module.

In step S512, if the erasure is possible, the capacitor array value is stored, and the following step S521 is continued.

The control terminal controls the signal generator to generate a first modulation signal, so that the equipment to be calibrated receives the first modulation signal through the Bluetooth module, calculates the self-frequency offset of the TSXO in the equipment, eliminates the self-frequency offset by adjusting the capacitance array value of the crystal oscillator, and stores the capacitance array value successfully eliminating the self-frequency offset into the equipment memory.

And step S540, if the calibration failure cannot be eliminated, reporting a calibration failure message, and not continuing to execute the subsequent steps.

If the Bluetooth module cannot adjust the capacitance array value, or cannot eliminate the self-frequency offset even if the capacitance array value is adjusted for multiple times, for example, if the local oscillation signal frequency of the capacitance array value crystal of the Bluetooth module adjustment crystal oscillator is almost kept unchanged, the crystal oscillator of the device can be considered to be abnormal in operation, and a calibration failure message is reported.

And step S520, temperature drift calibration. Step S520 specifically includes the following steps S521 to S525, in which:

step S521, obtain the first temperature, and calculate the frequency offset of the TSXO at the first temperature.

Step S522, the PA of the WIFI module of the device is made to transmit with a certain power, so as to raise the temperature of the TSXO.

Step S523, waiting for a period of time, acquiring a second temperature, and calculating the frequency offset of the TSXO at the second temperature; optionally, the difference between the first temperature and the second temperature is not less than 1 degree celsius.

Step 524, waiting for a period of time, acquiring a third temperature, and calculating the frequency offset of the TSXO at the third temperature; optionally, a difference between the second temperature and the third temperature is not less than 0.5 ℃.

And step S525, the PA transmission of the WIFI module is closed.

Step S526, wait for a period of time, collect the fourth temperature, and calculate the frequency offset of the TSXO at the fourth temperature.

Optionally, the fourth temperature is at least 3 degrees celsius lower than the third temperature.

Time interval between above-mentioned four temperatures can set up through the transmission power of the PA of WIFI module to realize the collection of temperature, also can judge whether TSXO can normally work when the temperature changes according to transmission power. For example, if the PA of the WIFI module is set to transmit at a certain power, but the TSXO does not increase the corresponding temperature within a certain time, it may be determined that the TSXO does not operate normally, and a calibration failure message may be reported.

Step S530, the four temperatures and the corresponding frequency offsets are stored in the memory of the device.

In steps S521, S523, and S524 to S526, if any of the steps fails to be executed, a message indicating that the test failed is reported, and the subsequent steps are not executed.

And step S550, finishing the production line calibration.

After the equipment finishes the calibration of the production line, the capacitor array of the TSXO can be automatically set according to the capacitor array value when the frequency deviation stored in the calibration of the production line is a preset value, so that the capacitance value corresponding to the capacitor array is the capacitor array value when the frequency deviation is the preset value, and the self-frequency deviation of the TSXO in the equipment is eliminated.

In one embodiment, the self-calibration method of the device may further include a temperature drift self-calibration step, please refer to fig. 6, fig. 6 provides a schematic flow chart of the temperature drift self-calibration step; the temperature drift self-calibration step comprises:

step S601, reading at least four temperatures and frequency offsets corresponding to the temperatures.

Step S602, obtaining a first temperature drift theoretical formula, and substituting the at least four temperatures and the frequency offsets corresponding to each temperature into the first temperature drift theoretical formula to obtain the temperature drift formula of the TSXO.

S603, obtaining the real-time working temperature of the TSXO, and obtaining the frequency offset corresponding to the real-time working temperature according to the temperature drift formula of the TSXO.

S604, compensating the frequency offset by using a GPS module.

The first temperature drift theoretical formula in step S602 is:

F＝c3*(t-t0)^3+c2*(t-t0)^2+c1*(t-t0)+c0 (2)

wherein, F is the frequency offset of the TSXO at the temperature t, the variable t is the temperature, t0 is the reference temperature, and c0, c1, c2 and c3 are constants in the temperature system.

Formula (2) is that the typical crystal temperature drift curve is a cubic polynomial, and the temperature drift change of the TSXO can be expressed by the temperature drift curve of the crystal. In this case, the device may calculate, through the stored four temperatures and the frequency offset corresponding to each temperature, constants C0, C1, C2, and C3 therein, and restore the temperature drift formula of the TSXO, so that when the temperature of the working environment changes, the frequency offset at the temperature is automatically obtained according to the restored temperature drift formula, and is compensated by the GPS module.

In this embodiment, for the TSXO, the temperature drift curve may be summarized as a cubic polynomial in formula (2), and the temperature drift formula of the TSXO may be obtained according to the four temperatures stored in the device and the frequency offset corresponding to each temperature, so that the device may automatically compensate the generated frequency offset according to the change of the operating temperature, and self-calibration of the device on the temperature drift is implemented.

In one embodiment, the TSXO includes a crystal and an oscillator, the at least four different voltage values being voltages across the crystal, the method further comprising: reading at least two temperatures of the oscillator and at least four temperatures of the crystal; acquiring a second temperature drift theoretical formula, and inputting at least two temperatures of the oscillator and at least four temperatures of the crystal into the second temperature drift formula to obtain a temperature drift formula of the TSXO; acquiring the real-time working temperature of the TSXO, and acquiring the frequency offset corresponding to the real-time working temperature according to the temperature drift formula of the TSXO; compensating the frequency deviation by utilizing a GPS module;

wherein, the second temperature drift theoretical formula is as follows:

F(t_t,t_o)＝c3_t*(t_t-t0)^3+c2_t*(t_t-t0)^2+c1_t*(t_t-t0)+c0_t+c0_o+c1_o*(t_o-t0) (3)

wherein, F (t)_t,t_o) For frequency deviation of the oscillating circuit, variable t_tIs the temperature of TSXO, t_oIs the temperature of the oscillator, t0 is the reference temperature, c0_t、c1_t、c2_tAnd c3_tConstant of TSXO in temperature systems, c0_o、c1_oIs a constant of the oscillator in the temperature system.

With continued reference to fig. 6, at least four of the temperature and first temperature drift equations of fig. 6 (i.e., equation (2)) represent only temperature drift variations of the crystal in the TSXO, without taking into account temperature variations of the oscillator. A general oscillating circuit consists of a capacitor and an inductor, and the change of the temperature inside the vibrator can influence the change of the capacitance value inside the oscillator, so that the oscillating frequency of the oscillator is influenced, and the accurate positioning of the GPS is influenced. In view of the above, the scheme solves the temperature drift problem on the basis of cost and precision. When the temperature drift calibration is carried out on a production line, not only the temperature drift curve of the crystal needs to be considered, but also the temperature drift change condition of the oscillator needs to be calibrated.

Specifically, the temperature drift change of the oscillator can be represented by F_oExpressed, as follows:

F_o＝c0_o+c1_o*(t_o-t0)；

wherein, F_oIs the frequency offset of the oscillator, variable t_oIs the temperature of the oscillator, t0 is the reference temperature, c0_oAnd c1_oIs a constant of the oscillator in the temperature system.

The temperature drift of the TSXO may be expressed as the sum of the temperature drift of the crystal and the temperature drift of the oscillator, i.e. the second temperature drift theoretical formula (i.e. formula (3)). The equipment can substitute at least two temperatures of the oscillator, at least four temperatures of the crystal and frequency deviation corresponding to each temperature into a second temperature deviation theoretical formula to obtain the temperature deviation formula of the TSXO, so that when the temperature of the working environment changes, the frequency deviation at the temperature is automatically obtained according to the reduced temperature deviation formula, and the compensation is carried out through the GPS module.

In this embodiment, the production line can calibrate both the temperature drift of the chip (temperature inside the oscillator chip) and the temperature drift of the chip (temperature outside the crystal chip) so that the device can automatically compensate according to calibrated parameters to achieve fast positioning and meet the requirements of subsequent GPS online learning tracking and fast and accurate positioning.

The embodiment of the present application further provides a system for calibrating a production line of a device clock, please refer to fig. 7, where the system includes a test instrument 701, a control end 702, and a device 703.

The control end 702 is connected to the test instrument 701 and the device 703, respectively, to control the test instrument 701 and the device 703.

The test instrument 701 is configured to transmit a first modulated signal.

The device 703 includes a TSXO and a bluetooth module, and is configured to adjust a capacitance array value of an oscillation circuit of the TSXO by using the bluetooth module to generate local oscillator signals with different frequencies, calculate a frequency offset between each local oscillator signal and the first modulation signal, obtain a capacitance array value when the frequency offset is a preset value, and store the capacitance array value when the frequency offset is the preset value.

For more contents of the working principle and the working mode of the production line calibration system of the device clock, reference may be made to the related descriptions in fig. 1 to fig. 6, and details are not repeated here.

The embodiment of the present application further provides a terminal, which includes a memory and a processor, where the memory stores computer instructions capable of running on the processor, and the processor executes the steps of the clock self-calibration method of the device shown in fig. 6 when executing the computer instructions.

This equipment can be for extensive connection equipment that possesses bluetooth module, GPS module and WIFI module such as cell-phone, computer, intelligent wrist-watch, and the clock signal of this equipment is produced by TSXO. The device can perform frequency offset compensation on the TSXO contained in the device through the clock self-calibration method so as to calibrate the local clock.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A method for in-line calibration of a device clock, wherein the device comprises a TSXO and a Bluetooth module, the method comprising:

eliminating the self-carried frequency offset of the TSXO through the Bluetooth module;

calibrating a temperature drift of the TSXO;

the eliminating the self-carried frequency offset of the TSXO through the Bluetooth module comprises the following steps:

transmitting a first modulated signal, the first modulated signal being received by the Bluetooth module;

adjusting a capacitance array value of an oscillation circuit of the TSXO through the Bluetooth module to generate local oscillator signals with different frequencies, calculating frequency deviation of each local oscillator signal and the first modulation signal, and acquiring the capacitance array value when the frequency deviation is a preset value;

storing the capacitance array value when the frequency deviation is a preset value into the equipment;

the device further includes a WIFI module that calibrates the temperature drift of the TSXO, including:

transmitting a second modulated signal, the second modulated signal being received by the Bluetooth module;

heating the TSXO through the WIFI module, and collecting at least four temperatures;

acquiring frequency offset corresponding to each temperature according to the second modulation signal through the Bluetooth module;

storing the at least four temperatures and the frequency offsets corresponding to each temperature in the device;

wherein the TSXO comprises a thermistor, a crystal and an oscillator, and the acquiring of at least four temperatures comprises:

a resistor with a preset resistance value is connected in series with the TSXO, and the resistor with the preset resistance value and the TSXO form a voltage division circuit;

collecting at least four voltage values at two ends of a crystal of the TSXO according to the voltage division circuit;

calculating the corresponding resistance value of the thermistor according to the at least four voltage values, and obtaining the at least four temperatures according to the corresponding relation between the resistance value of the thermistor and the temperatures;

the method further comprises the following steps:

collecting voltage values of a thermal diode inside the oscillator while collecting at least four temperatures of the crystal;

obtaining at least two temperatures of the oscillator according to the voltage value of a thermal diode in the oscillator;

storing at least two temperatures of the oscillator in correspondence with at least four temperatures of the crystal in the device.

2. The method of claim 1, wherein the bluetooth module comprises a mixer, and wherein calculating the frequency offset of each local oscillator signal from the first modulated signal comprises:

mixing the first modulation signal and each local oscillation signal through the frequency mixer to obtain a first mixing signal corresponding to each local oscillation signal;

and calculating the frequency offset corresponding to each local oscillation signal according to the first mixing signal.

3. The method of claim 2, wherein the first mixing signal is calculated by:

f_I＝f_L±f_C；

4. The method of claim 1, wherein the predetermined value is a value having a minimum absolute value.

5. The method of claim 1, wherein the obtaining the frequency offset corresponding to each temperature according to the second modulation signal comprises:

for each temperature, acquiring a local oscillation signal of the TSXO at the temperature;

respectively mixing the second modulation signal and the local oscillator signal at each temperature through a mixer of the Bluetooth module to obtain a second mixing signal at each temperature;

and calculating the frequency offset at each temperature according to the second mixing signal.

6. The method of claim 1, wherein the at least four temperatures are four different values of temperature, and wherein the warming the TSXO by the WIFI module and collecting the at least four temperatures comprises:

acquiring a first temperature before the TSXO is warmed up;

heating the TSXO through the WIFI module, and collecting a second temperature and a third temperature in the heating process;

and stopping heating the TSXO, and collecting a fourth temperature in the cooling process.

7. A method of self-calibrating a clock of a device, the device comprising a TSXO, a GPS module and a bluetooth module, the TSXO comprising a crystal and an oscillator, the method comprising:

reading a capacitance array value when the frequency offset is a preset value from the equipment, and setting a capacitance array of an oscillation circuit of the TSXO according to the capacitance array value;

reading at least two temperatures of the oscillator and at least four temperatures of the crystal;

acquiring a second temperature drift theoretical formula, and inputting at least two temperatures of the oscillator and at least four temperatures of the crystal into the second temperature drift formula to obtain a temperature drift formula of the TSXO;

acquiring the real-time working temperature of the TSXO, and acquiring the frequency offset corresponding to the real-time working temperature according to the temperature drift formula of the TSXO;

compensating the frequency offset by using the GPS module;

wherein, the second temperature drift theoretical formula is as follows:

F(t_t,t_o)＝c3_t*(t_t-t0)^3+c2_t*(t_t-t0)^2+c1_t*(t_t-t0)+c0_t+c0_o+c1_o*(t_o-t0)；

8. The production line calibration system of the equipment clock is characterized by comprising a test instrument, a control end and equipment, wherein the control end is respectively connected with the test instrument and the equipment to control the test instrument and the equipment;

the test instrument is used for sending a first modulation signal;

the device comprises a TSXO, a Bluetooth module and a WIFI module, and is used for adjusting the capacitance array value of an oscillating circuit of the TSXO by using the Bluetooth module to generate local oscillator signals with different frequencies, calculating the frequency deviation of each local oscillator signal and the first modulation signal, acquiring the capacitance array value when the frequency deviation is a preset value, and storing the capacitance array value when the frequency deviation is the preset value;

the equipment heats the TSXO through the WIFI module and collects at least four temperatures;

the equipment receives a second modulation signal through the Bluetooth module, and acquires frequency offset corresponding to each temperature according to the second modulation signal;

9. A terminal comprising a memory and a processor, the memory having stored thereon computer instructions executable on the processor, wherein the processor, when executing the computer instructions, performs the steps of the method of claim 7.