Temperature-compensated crystal oscillator temperature compensation test system and method

Abstract

This invention provides a temperature-compensated crystal oscillator (TCC) temperature compensation testing system and method. The system includes: a host computer; a frequency source; a high and low temperature test chamber, the host computer setting the temperature of the test chamber; and multiple test circuit boards located inside the test chamber. Each test circuit board includes an FPGA frequency measurement circuit, an ARM control circuit, and multiple TCXO test circuits. The FPGA frequency measurement circuit measures the frequency of the TCC on each test circuit board according to control commands sent by the host computer. Each TCXO test circuit acquires the frequency of the corresponding TCC at different temperatures. The ARM control circuit determines the voltage-controlled voltage (VDC) of each TCC based on the difference between the frequency of each TCC and the frequency of the frequency source. The host computer determines the compensation parameters of the TCC based on the VDC and writes the compensation parameters back to the TCC. This invention enables batch temperature compensation testing, improving testing efficiency.

Description

Technical Field

[0001] This invention relates to the field of temperature-compensated crystal oscillator testing technology, and in particular to a temperature-compensated crystal oscillator testing system and method. Background Technology

[0002] Temperature-compensated crystal oscillators (TCXOs) are core components of electronic devices, offering high frequency stability. As a high-precision frequency source, they are widely used in communication systems, radar navigation systems, and precision measurement and control systems. TCXOs compensate for oscillation frequency deviations caused by changes in ambient temperature through temperature compensation circuitry.

[0003] In the research and manufacturing of temperature-compensated crystal oscillators (TCCs), measuring the frequency-temperature characteristics of the crystal is an essential step. During long-term operation, various factors can cause fluctuations or aging drift in the operating frequency of a typical crystal oscillator. To ensure the operating frequency meets system requirements, adjustments must be made when the frequency exceeds these requirements, usually achieved through voltage regulation. Furthermore, since the preset parameters and software of the TCC are written during the measurement phase, the efficiency of frequency characteristic measurement directly impacts the industrial production efficiency of TCCs. Additionally, to obtain high-precision TCCs, frequency measurement must also meet certain accuracy requirements. Temperature compensation for TCXOs is a key technology, ensuring high accuracy and stability of the crystal's output frequency across the entire temperature range through temperature compensation testing.

[0004] Temperature-compensated crystal oscillator (TCC) testing is a fundamental and important measurement technique, mainly classified into five categories: direct frequency measurement, time interval / phase conversion frequency measurement, digital frequency measurement, interpolation frequency measurement, and frequency mixing frequency measurement. Current TCC testing equipment generally employs the direct frequency measurement method, and they all share very similar system structures, including a main control computer, a high and low temperature test chamber, a multiplexer, a standard frequency standard, a high-precision frequency meter, and a test circuit board, etc. Figure 1 As shown, due to the limited number of frequency meters available in the frequency characteristic measurement stage (usually only one), the temperature-compensated crystal oscillators (TCCs) under test can only be tested one by one, resulting in low testing efficiency and hindering mass testing and production. Furthermore, during the individual testing of TCCs, maintaining a stable testing environment for an extended period is necessary to ensure all TCCs are tested under the same temperature conditions. This necessitates long holding and testing times for frequency-temperature characteristics testing under different temperature conditions, consuming excessive production resources and increasing production costs. Traditional testing systems can only shorten testing time by reducing the number of testing temperature points, which in turn leads to fewer test data points, reduced compensation accuracy of the TCCs, and sacrifices product accuracy and frequency stability.

[0005] Therefore, traditional temperature-compensated crystal oscillator (TCC) testing equipment is inefficient, with the testing time directly proportional to the number of TCCs under test. Furthermore, it cannot simultaneously accommodate the diverse dynamic frequency-temperature characteristics of TCCs and the long testing duration. Traditional testing equipment is generally only suitable for testing a small number of TCC products. Summary of the Invention

[0006] This invention provides a temperature-compensated crystal oscillator (TCQSO) temperature compensation testing system and method to address the shortcomings of existing TQSO testing equipment, such as low efficiency and inability to balance the diversity of test data and test duration. The system enables parallel measurement of multiple TQSO frequency signals and batch temperature compensation testing.

[0007] This invention provides a temperature-compensated crystal oscillator temperature compensation testing system, comprising:

[0008] Test the host computer;

[0009] A frequency source, which is used to provide a frequency reference;

[0010] A high and low temperature test chamber, wherein the high and low temperature test chamber is connected to the test host computer via a signal connection, and the test host computer is used to set the temperature of the high and low temperature test chamber;

[0011] Multiple test circuit boards are located inside the high and low temperature test chamber. Each test circuit board is connected to the host computer for testing and to the frequency source signal.

[0012] Each test board includes an FPGA frequency measurement circuit, an ARM control circuit, and multiple TCXO test circuits;

[0013] The FPGA frequency measurement circuit is used to measure the frequency of the temperature-compensated crystal oscillator on each test circuit board at different temperatures according to the control commands sent by the test host computer.

[0014] Each TCXO test circuit is used to acquire the frequency of the temperature-compensated crystal oscillator corresponding to each TCXO test circuit at different temperatures. The TCXO test circuit corresponds one-to-one with the temperature-compensated crystal oscillator on each test board.

[0015] The ARM control circuit is used to determine the voltage control voltage of each temperature-compensated crystal oscillator at different temperatures based on the difference between the frequency of each temperature-compensated crystal oscillator at different temperatures and the frequency of the frequency source, so that the frequency of each temperature-compensated crystal oscillator at different temperatures is equal to the frequency of the frequency source.

[0016] The host computer is used to determine the compensation parameters of each temperature-compensated crystal oscillator based on the voltage-controlled voltage of each temperature-compensated crystal oscillator, and write the compensation parameters of each temperature-compensated crystal oscillator back to each temperature-compensated crystal oscillator.

[0017] According to the temperature-compensated crystal oscillator temperature compensation testing system provided by the present invention, the FPGA frequency measurement circuit is used for:

[0018] After receiving the control command sent by the test host computer, a counter is used to count the falling edge of the frequency signal of each temperature-compensated crystal oscillator;

[0019] After counting the falling edges of the frequency signal, the frequency signal is interrupted, the counter is cleared, and the count of the falling edges is latched as the frequency of each temperature-compensated crystal oscillator.

[0020] According to the present invention, a temperature-compensated crystal oscillator temperature compensation testing system is provided, wherein the ARM control circuit is used to adjust the voltage-controlled voltage of each temperature-compensated crystal oscillator based on the difference between the frequency of each temperature-compensated crystal oscillator at different temperatures and the frequency of the frequency source, so that the frequency of each temperature-compensated crystal oscillator at different temperatures is equal to the frequency of the frequency source.

[0021] According to the present invention, a temperature-compensated crystal oscillator temperature compensation testing system is provided, wherein the testing host computer is used to obtain a first relationship curve between the voltage control voltage and the temperature based on the voltage control voltage of each temperature-compensated crystal oscillator at different temperatures;

[0022] Multiple points are selected from the first relationship curve and combined to obtain a second relationship curve between the voltage control voltage and the temperature for each combination;

[0023] Calculate the difference between the voltage control voltage at the same temperature between each of the second relationship curves and the first relationship curve;

[0024] Calculate the average of the differences corresponding to all temperatures in each second relationship curve, and determine the compensation parameters for each temperature-compensated crystal oscillator based on the combination corresponding to the minimum average value.

[0025] According to the present invention, a temperature-compensated crystal oscillator temperature compensation test system is provided, wherein the test host computer is used to write the default parameters of each temperature-compensated crystal oscillator into the temperature-compensated crystal oscillator;

[0026] The FPGA frequency measurement circuit is also used to measure the frequency of each temperature-compensated crystal oscillator under the default parameters when the temperature inside the high and low temperature test chamber is at room temperature.

[0027] The host computer is used to determine whether the frequency of each temperature-compensated crystal oscillator is normal based on the difference between the frequency of each temperature-compensated crystal oscillator under default parameters and the frequency of the frequency source.

[0028] This invention also provides a method for testing temperature compensation of a temperature-compensated crystal oscillator, comprising:

[0029] The temperature of the high and low temperature test chamber is set by the host computer.

[0030] The frequency of the temperature-compensated crystal oscillator on each test circuit board in the high and low temperature test chamber is measured at different temperatures according to the control command sent by the test host computer, using the FPGA frequency measurement circuit in each test circuit board.

[0031] The frequency of the temperature-compensated crystal oscillator corresponding to each TCXO test circuit in each test circuit is collected at different temperatures. The TCXO test circuit corresponds one-to-one with the temperature-compensated crystal oscillator on each test circuit.

[0032] The ARM control circuit in each test circuit board determines the voltage control voltage of each temperature-compensated crystal oscillator at different temperatures based on the difference between the frequency of each temperature-compensated crystal oscillator at different temperatures and the frequency of the frequency source, so that the frequency of each temperature-compensated crystal oscillator at different temperatures is equal to the frequency of the frequency source.

[0033] The host computer determines the compensation parameters of each temperature-compensated crystal oscillator based on the voltage-controlled voltage of each temperature-compensated crystal oscillator, and writes the compensation parameters of each temperature-compensated crystal oscillator back to each temperature-compensated crystal oscillator.

[0034] According to the temperature-compensated crystal oscillator testing system provided by the present invention, the step of measuring the frequency of the temperature-compensated crystal oscillator on each test circuit board in the high and low temperature test chamber at different temperatures according to the control command sent by the host computer, through the FPGA frequency measurement circuit in each test circuit board, includes:

[0035] After receiving the control command sent by the test host computer, the FPGA frequency measurement circuit uses a counter to count the falling edges of the frequency signal of the temperature-compensated crystal oscillator.

[0036] After counting the falling edges of the frequency signal, the frequency signal is interrupted, the counter is cleared, and the count of the falling edges is latched as the frequency of each temperature-compensated crystal oscillator.

[0037] According to the temperature-compensated crystal oscillator (TCQSO) temperature compensation testing system provided by the present invention, the step of determining the voltage-controlled voltage of each TQSO at different temperatures by means of the ARM control circuit in each test circuit board based on the difference between the frequency of each TQSO at different temperatures and the frequency of the frequency source includes:

[0038] The ARM control circuit adjusts the voltage control voltage of each temperature-compensated crystal oscillator based on the difference between the frequency of each temperature-compensated crystal oscillator at different temperatures and the frequency of the frequency source, using a PI control algorithm, so that the frequency of each temperature-compensated crystal oscillator at different temperatures is equal to the frequency of the frequency source.

[0039] According to the temperature compensation testing system for temperature-compensated crystal oscillators provided by the present invention, the step of determining the compensation parameters of each temperature-compensated crystal oscillator by the host computer based on the voltage-controlled voltage of each temperature-compensated crystal oscillator includes:

[0040] The host computer uses the voltage-controlled voltage of each temperature-compensated crystal oscillator at different temperatures to obtain a first relationship curve between the voltage-controlled voltage and the temperature.

[0041] Multiple points are selected from the first relationship curve and combined to obtain a second relationship curve between the voltage control voltage and the temperature for each combination;

[0042] Calculate the difference between the voltage control voltage at the same temperature between each of the second relationship curves and the first relationship curve;

[0043] Calculate the average of the differences corresponding to all temperatures in each second relationship curve, and determine the compensation parameters for each temperature-compensated crystal oscillator based on the combination corresponding to the minimum average value.

[0044] The temperature compensation testing system for a temperature-compensated crystal oscillator provided by the present invention further includes:

[0045] The host computer for testing writes the default parameters of each temperature-compensated crystal oscillator into each temperature-compensated crystal oscillator.

[0046] The frequency of each temperature-compensated crystal oscillator under the default parameters is measured using the FPGA frequency measurement circuit in the high and low temperature test chamber when the temperature is at room temperature.

[0047] The host computer determines whether the frequency of each temperature-compensated crystal oscillator is normal based on the difference between the frequency of each temperature-compensated crystal oscillator under default parameters and the frequency of the frequency source.

[0048] The temperature-compensated crystal oscillator (TCC) testing system and method provided by this invention integrates the testing circuit onto a testing circuit board. A host computer controls multiple testing circuit boards in parallel to perform TCC testing. All TCC oscillators are centrally placed in a high-low temperature test chamber, enabling simultaneous batch testing of frequency signals from multiple TCC oscillators at the same temperature. This improves testing efficiency and eliminates the need to shorten testing time by reducing the number of testing temperature points, balancing the diversity of test data and testing duration. It offers advantages such as wide frequency range, wide temperature range, high precision, automation, and batch measurement. The testing system has a small footprint, low cost, high rotational stability, and a simple and efficient testing method, improving the accuracy and pass rate of TCC oscillators, reducing production costs, and increasing production efficiency. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0050] Figure 1 This is a schematic diagram of the structure of a TCXO testing system provided by existing technology;

[0051] Figure 2 This is a schematic diagram of the temperature compensation test system for temperature-compensated crystal oscillators provided by the present invention;

[0052] Figure 3 This is a schematic diagram of the software architecture of the temperature-compensated crystal oscillator temperature compensation test system provided by the present invention;

[0053] Figure 4 This is a schematic diagram of the test process of the temperature-compensated crystal oscillator temperature compensation test system provided by the present invention;

[0054] Figure 5 This is a schematic diagram of the test results of the temperature-compensated crystal oscillator temperature compensation test system provided by the present invention;

[0055] Figure 6 This is a schematic diagram of the test results of the external system in the temperature compensation test system for temperature-compensated crystal oscillators provided by the present invention;

[0056] Figure 7 This is a schematic flowchart of the temperature compensation test method for temperature-compensated crystal oscillators provided by the present invention. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0058] The following is combined Figure 2 The present invention describes a temperature-compensated crystal oscillator temperature compensation testing system, comprising:

[0059] Test the host computer;

[0060] The host computer for testing mainly consists of a LabVIEW test host computer program. It is the control core of the entire system, used to set relevant test procedures and parameters, monitor the system's operating status, record relevant test data and calculate compensation parameters, and store parameters and measurement results.

[0061] A frequency source, which is used to provide a frequency reference;

[0062] Optionally, the frequency source is a high-precision frequency standard (clock source), such as a 10MHz high-precision frequency standard, used to provide a reference clock signal for the test board, especially to provide a frequency reference for frequency measurement of the TCXO.

[0063] Each test board's clock input interface is equipped with a buffer to improve load capacity and eliminate the impact of load on the clock source itself. Therefore, one clock source can provide clocks to multiple test boards simultaneously.

[0064] A high and low temperature test chamber, wherein the high and low temperature test chamber is connected to the test host computer via a signal connection, and the test host computer is used to set the temperature of the high and low temperature test chamber;

[0065] The high and low temperature test chamber primarily provides an accurate and stable ambient temperature for the compensation testing process, and provides timely feedback of the real-time temperature, which is recorded and saved by the host computer. The data can be stored in a database via Ethernet according to the data management system format.

[0066] Multiple test circuit boards are located inside the high and low temperature test chamber. Each test circuit board is connected to the host computer for testing and to the frequency source signal.

[0067] The main function of the 0 test circuit board is to realize frequency testing, crystal oscillator frequency and temperature data acquisition, and temperature compensation testing, using the relevant control signals sent by the test host computer as a reference.

[0068] Each test board includes an FPGA (Field Programmable Gate Array) frequency measurement circuit, an ARM (Advanced RISC Machines) control circuit, and multiple TCXO test circuits.

[0069] The FPGA frequency measurement circuit is used to measure the frequency of the temperature-compensated crystal oscillator on each test circuit board at different temperatures according to the control commands sent by the test host computer.

[0070] Each TCXO test circuit is used to acquire the frequency of the temperature-compensated crystal oscillator corresponding to each TCXO test circuit at different temperatures. The TCXO test circuit corresponds one-to-one with the temperature-compensated crystal oscillator on each test circuit board 0.

[0071] The ARM control circuit is used to determine the voltage control voltage of each temperature-compensated crystal oscillator at different temperatures based on the difference between the frequency of each temperature-compensated crystal oscillator at different temperatures and the frequency of the frequency source, so that the frequency of each temperature-compensated crystal oscillator at different temperatures is equal to the frequency of the frequency source.

[0072] The test host computer described in 5 is used to determine the compensation parameters of each temperature-compensated crystal oscillator based on the voltage-controlled voltage of each temperature-compensated crystal oscillator, and write the compensation parameters of each temperature-compensated crystal oscillator back to each temperature-compensated crystal oscillator.

[0073] The power supply provides a stable voltage to the test circuit board and temperature-compensated crystal oscillator of the entire test system, ensuring the normal operation of the system.

[0074] The MOXA card serves as a serial communication tool, enabling signal communication and data transmission between the host computer and the test circuit.

[0075] The testing system measures the frequency signal of the temperature-compensated crystal oscillator without compensation, and then sends the measured frequency data and real-time temperature information to the host computer, which generates the frequency-temperature characteristic matrix for each temperature-compensated crystal oscillator.

[0076] The host computer is also responsible for measuring and comparing the frequency signals under different temperature conditions with the high-precision frequency standard signal. Using the high-precision frequency standard signal as a reference, the input voltage control value of the test circuit board is adjusted according to the measurement deviation between the two. The system automatically generates the compensation voltage-temperature curve (VT curve data), obtains the temperature compensation parameter table, and automatically calculates and burns the parameters into the temperature-compensated crystal oscillator to complete the compensation test of the temperature-compensated crystal oscillator.

[0077] The frequency-temperature characteristics of a temperature-compensated crystal oscillator (TCI) are primarily determined by the frequency-temperature characteristics of the crystal resonator. The commonly used AT-cut crystal resonator exhibits a cubic frequency-temperature characteristic curve. The principle of temperature compensation in a TCI is to change the load capacitance in the oscillation circuit, causing it to change with temperature, thereby compensating for the frequency drift caused by changes in ambient temperature and keeping the output frequency essentially constant.

[0078] Based on the above analysis, the compensation principle of the test system can be derived as follows:

[0079] 1. Measure and determine the compensation voltage-temperature curve (VT curve) that minimizes the frequency error of the temperature-compensated crystal oscillator;

[0080] 2. Based on the compensation voltage-temperature curve (VT curve data), calculate the compensation parameters and select the parameter with the smallest offline compensation residual as the final parameter;

[0081] 3. Write the compensation parameters, test the full-temperature frequency output of the crystal oscillator after compensation, and evaluate and verify the compensation effect.

[0082] It can be seen that obtaining accurate compensation voltage-temperature curve parameters is a key step in the design and production of temperature-compensated crystal oscillators, which directly affects the accuracy of frequency compensation and the performance of the temperature-compensated crystal oscillator.

[0083] High-precision frequency measurement and voltage-controlled voltage loading compensation model are key modules in the overall system design. The high-precision frequency measurement process and method can effectively measure the deviation between the temperature-compensated crystal oscillator frequency signal and the standard frequency signal, and can effectively obtain the compensation voltage-temperature curve (VT curve data) to verify the effect of temperature compensation. The voltage-controlled voltage loading compensation model can ensure the compensation accuracy of the temperature-compensated crystal oscillator and improve its performance and frequency stability.

[0084] like Figure 3 As shown, the software system of the host computer for testing includes four parts: control scheduling, data acquisition, information processing, and parameter write-back.

[0085] The test control function includes configuring parameters such as the temperature range, temperature change rate, and test duration of the test chamber, as well as controlling the start and stop of temperature compensation, controlling the test circuit board to achieve tests in different states, and sending this control information to the high and low temperature test chamber and the test circuit board.

[0086] The data acquisition function is responsible for collecting the temperature information and frequency count information of each channel of the crystal oscillator under test output by the test circuit board during the test process, as well as the voltage control voltage value corresponding to the frequency error requirement.

[0087] The data processing function includes converting the frequency count information output by the test circuit board into frequency measurement values, and generating frequency-temperature curves and voltage-controlled voltage-temperature curves (VT curve data) for each channel crystal oscillator together with the corresponding temperature information, and calculating the temperature compensation parameter table.

[0088] The parameter read / write function is responsible for writing the calculated temperature compensation parameter information back to each channel crystal oscillator, and can also read the parameters of each channel crystal oscillator.

[0089] The test system program can perform different functional tests on temperature-compensated crystal oscillators. The program functions are as follows:

[0090] 1. TCXO Parameter Setting Program: This program measures and sets the parameters of the TCXO by sending different commands to the test circuit board. Parameter setting generally includes two types: initial parameter setting and nominal frequency download before calibration, and scaling parameter programming after calibration.

[0091] 2. TCXO Voltage-Frequency Curve Test Program: This program tests the voltage-frequency curve of the TCXO by sending commands to the test circuit board. It provides a basis for setting various TCXO parameters and calculating open-loop calibration compensation parameters.

[0092] 3. Open-loop calibration test: By cyclically sending commands to the test circuit board, the frequency of the TCXO changes with temperature under conditions of with and without compensation.

[0093] 4. Closed-loop calibration test: Closed-loop calibration is performed by cyclically sending commands to the test circuit board to obtain the temperature-voltage control curve that makes the TCXO frequency deviation 0.

[0094] 5. TCXO performance test program: The frequency accuracy of the compensated TCXO is tested by sending commands to the test board in a loop.

[0095] The testing process of the test system should be carried out according to the relevant procedures. First, install the temperature-compensated crystal oscillator on the test socket, and then insert the test socket into the test circuit board. Place the test circuit board into the high and low temperature test chamber, and adjust the temperature of the high and low temperature test chamber according to the system settings.

[0096] The frequency measurement error of the temperature-compensated crystal oscillator batch testing system designed in this paper does not exceed ±1×10⁻⁶. -8 It fully meets the design and production requirements, with temperature stability not exceeding ±1×10. -7 It meets the accuracy requirements of TCXO and has a good compensation effect.

[0097] The TCXO batch temperature compensation system can simultaneously test 8 test circuits, and a single circuit board can perform compensation testing on 64 crystal oscillators. A single system can test 512 temperature-compensated crystal oscillators and can be further expanded. This system has good compatibility, capable of simultaneously performing compensation testing on crystal oscillators of multiple frequencies, as long as the crystal oscillators on each test circuit board have the same frequency. The system's compensation testing process is simple and fully automated, requiring no manual operation to automatically perform frequency testing, compensation testing, parameter calculation, parameter writing, and verification testing. This high degree of automation significantly improves production efficiency.

[0098] This system is compatible with various existing models of test chambers, power supplies, and other equipment, eliminating the need to purchase dedicated testing equipment, thus saving costs and improving equipment utilization efficiency. It is fully automated, requiring no pre-entry of crystal oscillator parameters; the system automatically generates parameters based on frequency and options, significantly reducing operational and experience-based costs.

[0099] This testing system can be extended to various types and frequencies of temperature-compensated crystal oscillators, exhibiting extremely high testing compatibility. It can salvage crystal oscillators that were previously uncompensable, significantly saving costs and resources.

[0100] This embodiment integrates the test circuit onto the test circuit board, and uses a host computer to control multiple test circuit boards in parallel to perform temperature-compensated crystal oscillator (TCC) tests. All TCCs are placed in a high-low temperature test chamber, thereby enabling simultaneous batch testing of frequency signals from multiple TCCs at the same temperature. This improves testing efficiency and eliminates the need to shorten testing time by reducing the number of test temperatures, balancing the diversity of test data and test duration. It offers advantages such as wide frequency range, wide temperature range, high precision, automation, and batch measurement. The test system has a small footprint, low cost, high rotational stability, and a simple and efficient testing method, improving the accuracy and pass rate of TCCs, reducing production costs, and increasing production efficiency.

[0101] Based on the above embodiments, the FPGA frequency measurement circuit in this embodiment is used for:

[0102] After receiving the control command sent by the test host computer, a counter is used to count the falling edge of the frequency signal of each temperature-compensated crystal oscillator;

[0103] After counting the falling edges of the frequency signal, the frequency signal is interrupted, the counter is cleared, and the count of the falling edges is latched as the frequency of each temperature-compensated crystal oscillator.

[0104] Traditional temperature-compensated crystal oscillator testing systems often use embedded software, while the temperature-compensated crystal oscillator batch temperature compensation testing system designed in this embodiment is based on an FPGA digital logic measurement scheme, which has higher reliability and feasibility. This measurement scheme is not only highly accurate and fast, but also allows multiple crystal oscillators that need compensation to be measured at the same time.

[0105] The working principle is as follows: After the FPGA frequency measurement circuit receives the control command sent by the test host computer, when the clear signal is invalid and the chip select signal becomes low, the counter in the FPGA frequency measurement circuit starts to count the falling edge of the crystal oscillator frequency signal under test. When all falling edges have been counted, the data latching function will be disabled, the relevant signals will be interrupted and cleared.

[0106] When the reset signal is invalid and the chip select signal is high, the counter will not count the falling edge of the crystal oscillator frequency signal, but will latch the relevant data in time and generate an interrupt signal on the rising edge to read the measurement signal related to the chip select time.

[0107] The chip select signal that needs to be measured is obtained from the clock signal of the high-precision frequency standard after being divided by the frequency divider. The change of the chip select signal is naturally synchronized with the change of the high-precision frequency standard clock signal, and there is no obvious correlation between its deviation and the accumulation of time. Therefore, the measurement scheme based on FPGA digital logic also uses the high-precision frequency standard clock signal as the measurement reference source to improve the accuracy of the measurement.

[0108] Based on the above embodiments, the ARM control circuit in this embodiment is used to adjust the voltage control voltage of each temperature-compensated crystal oscillator according to the difference between the frequency of each temperature-compensated crystal oscillator at different temperatures and the frequency of the frequency source, based on the PI (Proportional Integral) control algorithm, so that the frequency of each temperature-compensated crystal oscillator at different temperatures is equal to the frequency of the frequency source.

[0109] The voltage-controlled voltage compensation model of the test system mainly includes two aspects: the generation of voltage-controlled voltage input and accuracy control. The main purpose of the design is to meet the requirements of high-precision voltage-controlled voltage input generation and control.

[0110] In this embodiment, the test system selects a PI control algorithm for calculation during the frequency temperature compensation test, using the difference between the nominal frequency and the actual crystal oscillator frequency measurement value. At the beginning of compensation, the frequency difference is large, so a smaller measurement value is selected for periodic adjustment. According to the proportional adjustment algorithm, the difference between the crystal oscillator frequency and the nominal frequency is quickly reduced. When the measured crystal oscillator frequency is close to the nominal frequency, it indicates that the system has entered a stable phase. The periodic value of the measurement is gradually increased, and at this point, the PI adjustment algorithm is selected to calculate the voltage control input. The crystal oscillator frequency compensation control also uses a corresponding calculation formula designed according to the model, facilitating rapid response control from the lower-level computer program.

[0111] The variation in crystal oscillator frequency accuracy is primarily related to the accuracy of the voltage-controlled voltage input. The accuracy value is the ratio of the maximum frequency range for crystal oscillator temperature compensation adjustment to the adjustment range of the voltage-controlled voltage input. Therefore, the accuracy can be controlled by adjusting these two values. Simultaneously, the resolution of the input voltage-controlled voltage also determines the accuracy of temperature compensation; the smaller the resolution of the voltage-controlled voltage, the smaller the crystal oscillator frequency error it can compensate for.

[0112] In traditional temperature-compensated crystal oscillator (TCC) testing systems, voltage-controlled voltage measurements are mostly performed manually. The temperature is changed to the target point and held, then the output of a digital voltmeter or regulated power supply is adjusted to bring the oscillator output to its center frequency. The output of the digital voltmeter or regulated power supply at this point is the compensation voltage for that temperature point. This process is repeated at each test temperature point to obtain a set of data.

[0113] This embodiment employs an external high-speed, high-resolution DAC (Digital Analog Converter) and a low-noise, low-temperature-drift operational amplifier to generate a high-precision voltage-controlled voltage for temperature compensation testing of the test system. Compared to traditional solutions using digital voltmeters, this approach offers faster control response, higher compensation efficiency, reduced equipment control steps, and enables automated, batch testing.

[0114] Based on the above embodiments, the test host computer in this embodiment is used to obtain a first relationship curve between the voltage control voltage and the temperature based on the voltage control voltage of each temperature-compensated crystal oscillator at different temperatures;

[0115] Based on the measured frequency versus temperature curve and the proportionality coefficient between the frequency change and the voltage control voltage change, the required compensation voltage versus temperature curve, i.e., the first relationship curve, is calculated.

[0116] Multiple points are selected from the first relationship curve and combined to obtain a second relationship curve between the voltage control voltage and the temperature for each combination;

[0117] Multiple points are selected from the first relationship curve and combined. The corresponding combination is fitted each time to obtain the second relationship curve of voltage-controlled voltage changing with temperature.

[0118] Calculate the difference between the voltage control voltage at the same temperature between each of the second relationship curves and the first relationship curve;

[0119] Calculate the average of the differences corresponding to all temperatures in each second relationship curve, and determine the compensation parameters for each temperature-compensated crystal oscillator based on the combination corresponding to the minimum average value.

[0120] Based on the above embodiments, such as Figure 4 As shown, in this embodiment, the host computer is used to write the default parameters of each temperature-compensated crystal oscillator into each temperature-compensated crystal oscillator;

[0121] The FPGA frequency measurement circuit is also used to measure the frequency of each temperature-compensated crystal oscillator under the default parameters when the temperature inside the high and low temperature test chamber is at room temperature.

[0122] The host computer is used to determine whether the frequency of each temperature-compensated crystal oscillator is normal based on the difference between the frequency of each temperature-compensated crystal oscillator under default parameters and the frequency of the frequency source.

[0123] like Figure 4 As shown, the test process of the test system includes parameter reading and writing, temperature compensation, voltage adjustment, and compensation parameter calculation and writing. The specific steps are as follows:

[0124] 1. Connect the power supply.

[0125] 2. Write default parameters: The host computer automatically selects the initial default parameters to be written based on the test status.

[0126] 3. Room temperature frequency test: Set the temperature chamber to room temperature and measure the frequency output of each TCXO channel under default parameters to determine whether the product under test is outputting the normal frequency.

[0127] 4. Voltage adjustment coefficient: The temperature chamber is set to room temperature. The voltage control voltage VC is set to 0.5V, 1.65V and 2.8V through the measurement command, and the frequency output at the corresponding voltage value is measured.

[0128] 5. Set the temperature of the incubator, maintain the temperature until it becomes constant, and then perform frequency measurement and temperature compensation.

[0129] 6. Calculate and write compensation parameters, and verify product performance.

[0130] Sixty-four crystal oscillators with an accuracy of 0.28ppm were selected for simultaneous frequency testing, and the external testing system and the testing system designed in this embodiment were compared and analyzed.

[0131] The test system designed in this embodiment tested the frequency and temperature stability of the crystal oscillator as follows: Figure 5 As shown, all 64 crystal oscillators were within 0.28ppm, which meets the product performance requirements. This indicates that the testing accuracy of the test system designed in this embodiment meets the design and production testing requirements and can be used for batch frequency testing of crystal oscillators.

[0132] like Figure 6 As shown, the test system in this embodiment has an error within ±0.15ppm compared to the external test system, with a mean error of 0.02ppm. This indicates that the test system designed in this embodiment has essentially the same test accuracy and consistency as the external test system. Through comparative evaluation testing, the TCXO temperature compensation system designed in this embodiment meets the requirements.

[0133] Temperature-compensated crystal oscillators were selected for temperature compensation testing, with a compensation temperature range of -40℃ to 85℃. After the compensation test, the system designed in this embodiment was used for comparative testing to verify the accuracy of the compensation test. The frequency error of the 20MHz crystal oscillator after compensation was within 1.5ppm. By comparing with other test systems, the frequency temperature stability differed by only 0.1ppm, and the compensation results were basically consistent.

[0134] The temperature compensation test method for temperature-compensated crystal oscillators provided by the present invention is described below. The temperature compensation test method for temperature-compensated crystal oscillators described below can be referred to in correspondence with the temperature compensation test system for temperature-compensated crystal oscillators described above.

[0135] like Figure 7 As shown, the method includes:

[0136] Step 701: Set the temperature of the high and low temperature test chamber using the host computer.

[0137] Step 702: The frequency of the temperature-compensated crystal oscillator on each test circuit board in the high and low temperature test chamber is measured at different temperatures according to the control command sent by the test host computer through the FPGA frequency measurement circuit in each test circuit board.

[0138] Step 703: Collect the frequency of the temperature-compensated crystal oscillator corresponding to each TCXO test circuit at different temperatures through each TCXO test circuit in each test circuit board. The TCXO test circuit corresponds one-to-one with the temperature-compensated crystal oscillator on each test circuit board.

[0139] Step 704: The ARM control circuit in each test circuit board determines the voltage control voltage of each temperature-compensated crystal oscillator at different temperatures based on the difference between the frequency of each temperature-compensated crystal oscillator at different temperatures and the frequency of the frequency source, so that the frequency of each temperature-compensated crystal oscillator at different temperatures is equal to the frequency of the frequency source.

[0140] Step 705: The host computer determines the compensation parameters of each temperature-compensated crystal oscillator based on the voltage-controlled voltage of each temperature-compensated crystal oscillator, and writes the compensation parameters of each temperature-compensated crystal oscillator back to the temperature-compensated crystal oscillator.

[0141] This embodiment integrates the test circuit onto the test circuit board, and uses a host computer to control multiple test circuit boards in parallel to perform temperature-compensated crystal oscillator (TCC) tests. All TCCs are placed in a high-low temperature test chamber, thereby enabling simultaneous batch testing of frequency signals from multiple TCCs at the same temperature. This improves testing efficiency and eliminates the need to shorten testing time by reducing the number of test temperatures, balancing the diversity of test data and test duration. It offers advantages such as wide frequency range, wide temperature range, high precision, automation, and batch measurement. The test system has a small footprint, low cost, high rotational stability, and a simple and efficient testing method, improving the accuracy and pass rate of TCCs, reducing production costs, and increasing production efficiency.

[0142] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A temperature-compensated crystal oscillator temperature compensation testing system, characterized in that, include: Test the host computer; A frequency source, which is used to provide a frequency reference; A high and low temperature test chamber, wherein the high and low temperature test chamber is connected to the test host computer via a signal connection, and the test host computer is used to set the temperature of the high and low temperature test chamber; Multiple test circuit boards are located inside the high and low temperature test chamber. Each test circuit board is connected to the host computer for testing and to the frequency source signal. Each test board includes an FPGA frequency measurement circuit, an ARM control circuit, and multiple TCXO test circuits; The FPGA frequency measurement circuit is used to measure the frequency of the temperature-compensated crystal oscillator on each test circuit board at different temperatures according to the control commands sent by the test host computer. Each TCXO test circuit is used to acquire the frequency of the temperature-compensated crystal oscillator corresponding to each TCXO test circuit at different temperatures. The TCXO test circuit corresponds one-to-one with the temperature-compensated crystal oscillator on each test board. The ARM control circuit is used to determine the voltage control voltage of each temperature-compensated crystal oscillator at different temperatures based on the difference between the frequency of each temperature-compensated crystal oscillator at different temperatures and the frequency of the frequency source, so that the frequency of each temperature-compensated crystal oscillator at different temperatures is equal to the frequency of the frequency source. The host computer is used to determine the compensation parameters of each temperature-compensated crystal oscillator based on the voltage-controlled voltage of each temperature-compensated crystal oscillator, and write the compensation parameters of each temperature-compensated crystal oscillator back to each temperature-compensated crystal oscillator. The host computer is used to obtain a first relationship curve between the voltage control voltage and the temperature based on the voltage control voltage of each temperature-compensated crystal oscillator at different temperatures; Multiple points are selected from the first relationship curve and combined to obtain a second relationship curve between the voltage control voltage and the temperature for each combination; Calculate the difference between the voltage control voltage at the same temperature between each of the second relationship curves and the first relationship curve; Calculate the average of the differences corresponding to all temperatures in each second relationship curve, and determine the compensation parameters for each temperature-compensated crystal oscillator based on the combination corresponding to the minimum average value.

2. The temperature-compensated crystal oscillator temperature compensation testing system according to claim 1, characterized in that, The FPGA frequency measurement circuit is used for: After receiving the control command sent by the test host computer, a counter is used to count the falling edge of the frequency signal of each temperature-compensated crystal oscillator; After counting the falling edges of the frequency signal, the frequency signal is interrupted, the counter is cleared, and the count of the falling edges is latched as the frequency of each temperature-compensated crystal oscillator.

3. The temperature-compensated crystal oscillator temperature compensation testing system according to claim 1, characterized in that, The ARM control circuit is used to adjust the voltage control voltage of each temperature-compensated crystal oscillator based on the difference between the frequency of each temperature-compensated crystal oscillator at different temperatures and the frequency of the frequency source, so that the frequency of each temperature-compensated crystal oscillator at different temperatures is equal to the frequency of the frequency source.

4. The temperature-compensated crystal oscillator temperature compensation testing system according to any one of claims 1-3, characterized in that, The host computer for testing is used to write the default parameters of each temperature-compensated crystal oscillator into each temperature-compensated crystal oscillator; The FPGA frequency measurement circuit is also used to measure the frequency of each temperature-compensated crystal oscillator under the default parameters when the temperature inside the high and low temperature test chamber is at room temperature. The host computer is used to determine whether the frequency of each temperature-compensated crystal oscillator is normal based on the difference between the frequency of each temperature-compensated crystal oscillator under default parameters and the frequency of the frequency source.

5. A method for testing temperature compensation of a temperature-compensated crystal oscillator, characterized in that, include: The temperature of the high and low temperature test chamber is set by the host computer. The frequency of the temperature-compensated crystal oscillator on each test circuit board in the high and low temperature test chamber is measured at different temperatures according to the control command sent by the test host computer, using the FPGA frequency measurement circuit in each test circuit board. The frequency of the temperature-compensated crystal oscillator corresponding to each TCXO test circuit in each test circuit is collected at different temperatures. The TCXO test circuit corresponds one-to-one with the temperature-compensated crystal oscillator on each test circuit. The ARM control circuit in each test circuit board determines the voltage control voltage of each temperature-compensated crystal oscillator at different temperatures based on the difference between the frequency of each temperature-compensated crystal oscillator at different temperatures and the frequency of the frequency source, so that the frequency of each temperature-compensated crystal oscillator at different temperatures is equal to the frequency of the frequency source. The host computer determines the compensation parameters of each temperature-compensated crystal oscillator based on the voltage-controlled voltage of each temperature-compensated crystal oscillator, and writes the compensation parameters of each temperature-compensated crystal oscillator back to each temperature-compensated crystal oscillator. The step of determining the compensation parameters of each temperature-compensated crystal oscillator by the host computer based on the voltage-controlled voltage of each temperature-compensated crystal oscillator includes: The host computer uses the voltage-controlled voltage of each temperature-compensated crystal oscillator at different temperatures to obtain a first relationship curve between the voltage-controlled voltage and the temperature. Multiple points are selected from the first relationship curve and combined to obtain a second relationship curve between the voltage control voltage and the temperature for each combination; Calculate the difference between the voltage control voltage at the same temperature between each of the second relationship curves and the first relationship curve; Calculate the average of the differences corresponding to all temperatures in each second relationship curve, and determine the compensation parameters for each temperature-compensated crystal oscillator based on the combination corresponding to the minimum average value.

6. The temperature compensation test method for a temperature-compensated crystal oscillator according to claim 5, characterized in that, The step of measuring the frequency of the temperature-compensated crystal oscillator on each test circuit board in the high and low temperature test chamber at different temperatures according to the control command sent by the host computer, through the FPGA frequency measurement circuit in each test circuit board, includes: After receiving the control command sent by the test host computer, the FPGA frequency measurement circuit uses a counter to count the falling edges of the frequency signal of the temperature-compensated crystal oscillator. After counting the falling edges of the frequency signal, the frequency signal is interrupted, the counter is cleared, and the count of the falling edges is latched as the frequency of each temperature-compensated crystal oscillator.

7. The temperature compensation test method for a temperature-compensated crystal oscillator according to claim 5, characterized in that, The step of determining the voltage-controlled voltage of each temperature-compensated crystal oscillator at different temperatures based on the difference between the frequency of each temperature-compensated crystal oscillator at different temperatures and the frequency of the frequency source, using the ARM control circuit in each test circuit board, includes: The ARM control circuit adjusts the voltage control voltage of each temperature-compensated crystal oscillator based on the difference between the frequency of each temperature-compensated crystal oscillator at different temperatures and the frequency of the frequency source, using a PI control algorithm, so that the frequency of each temperature-compensated crystal oscillator at different temperatures is equal to the frequency of the frequency source.

8. The temperature compensation test method for temperature-compensated crystal oscillators according to any one of claims 5-7, characterized in that, Also includes: The host computer for testing writes the default parameters of each temperature-compensated crystal oscillator into each temperature-compensated crystal oscillator. The frequency of each temperature-compensated crystal oscillator under the default parameters is measured using the FPGA frequency measurement circuit in the high and low temperature test chamber when the temperature is at room temperature. The host computer determines whether the frequency of each temperature-compensated crystal oscillator is normal based on the difference between the frequency of each temperature-compensated crystal oscillator under default parameters and the frequency of the frequency source.

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