A quartz crystal oscillator test frequency dividing circuit
By designing a frequency divider circuit for testing quartz crystal oscillators, the problems of signal reflection and waveform distortion caused by impedance mismatch under high-frequency conditions were solved. This enabled stable measurement of high-frequency signals and met the testing requirements for multi-variety, small-batch production, thereby improving the efficiency of frequency fine-tuning processes and product yield.
Patent Information
- Application Number
- CN202522043994.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-23
- Publication Date
- 2026-08-25
- Estimated Expiration
- 2035-09-23
AI Technical Summary
Under high-frequency conditions, impedance mismatch in quartz crystal oscillators leads to signal reflection, waveform distortion, and frequency counting errors. Traditional conditioning circuits have poor versatility and are difficult to adapt to the testing needs of multi-variety, small-batch production.
A frequency divider circuit for testing quartz crystal oscillators was designed, including a signal input interface, a signal conditioning module, a frequency divider module, and a buffer output module. Through waveform shaping, frequency division, and impedance isolation, it adapts to the output impedance of different oscillators and the input impedance of the measuring equipment, thereby reducing signal reflection and distortion.
It improves the stability and anti-interference capability of frequency measurement, enhances the efficiency of frequency fine-tuning process and product yield, and meets the testing needs of multi-variety, small-batch production.
Smart Images
Figure CN224684204U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of electronic measurement technology, specifically to a frequency division circuit for testing quartz crystal oscillators. Background Technology
[0002] A quartz crystal oscillator is a precision electronic device that uses a quartz crystal as its resonant element. It is widely used to provide stable clock signals for electronic systems. During manufacturing, to ensure that the output frequency meets the design target, a frequency fine-tuning process is required. This involves measuring the output frequency in real time and adjusting the crystal parameters to gradually approach the target frequency value. The accuracy of the frequency measurement directly determines the final performance and product yield of the oscillator. As electronic devices develop towards higher frequencies and higher speeds, the operating frequencies of quartz crystal oscillators are increasing, commonly exceeding 50MHz and even reaching the hundreds of MHz level. High-frequency signals are easily affected by circuit board wiring, connecting cables, and load impedance mismatch during transmission. Impedance mismatch can lead to signal reflection, waveform distortion, ringing, and in severe cases, frequency counting errors or oscillator frequency hopping, causing the fine-tuning process to fail or even damaging the product.
[0003] In existing testing systems, the oscillator output signal is typically connected directly to frequency measurement devices, such as frequency meters or counters, via transmission lines. However, different models of quartz crystal oscillators have varying driving capabilities and output impedances in their internal output stages, while the input impedance of the test circuit is generally a fixed value. This impedance mismatch can cause significant signal integrity problems at high frequencies, especially when the oscillator output impedance is inconsistent with the characteristic impedance of the transmission line or the input impedance of the measurement device. This increases the signal reflection coefficient, leading to exacerbated waveform distortion. Furthermore, some oscillator output waveforms are not standard square waves but non-ideal waveforms containing many harmonic components, further increasing the difficulty of accurate frequency measurement. While traditional methods can attempt to improve this through impedance matching networks or signal conditioning circuits, these methods suffer from poor versatility, complex adjustments, and difficulty in adapting to the testing needs of multi-variety, small-batch production. Utility Model Content
[0004] In view of the above problems, this utility model provides a quartz crystal oscillator test frequency divider circuit, the quartz crystal oscillator test frequency divider circuit comprising:
[0005] A signal input interface is provided for connecting the output signal of the quartz crystal oscillator under test.
[0006] A signal conditioning module, wherein the input terminal of the signal conditioning module is electrically connected to the signal input interface, is used to perform waveform shaping on the output signal and convert it into a differential output signal;
[0007] The frequency divider module has its input terminal electrically connected to the output terminal of the signal conditioning module, and is used to perform frequency division processing on the shaped differential signal.
[0008] A buffer output module, the input terminal of which is electrically connected to the output terminal of the frequency divider module, is used to perform impedance isolation and power drive on the frequency-divided signal and output it to a frequency measurement device.
[0009] In one possible implementation, the signal conditioning module includes a comparator and a level converter for shaping and converting the output signal into a differential signal.
[0010] In one possible implementation, the frequency divider module is a four-way divider, which is used to reduce the frequency of the output signal to one-quarter.
[0011] In one possible implementation, the frequency divider is implemented using a frequency divider with an LVPECL logic interface;
[0012] The differential input terminal of the frequency divider is connected to the differential output terminal of the signal conditioning module through an input terminal resistor network;
[0013] The differential output of the frequency divider is connected to the input of the buffer output module via an output resistor network.
[0014] In one possible implementation, a DC blocking capacitor is connected in series between the signal input interface and the input terminal of the signal conditioning module.
[0015] In one possible implementation, a load resistor is also connected in parallel at the signal input interface, the load resistor being used to provide a matching load for the quartz crystal oscillator under test.
[0016] In one possible implementation, the buffered output module includes a buffer, the input of which is connected to the output of the divider via a resistor network through a DC blocking capacitor.
[0017] In one possible implementation, the output terminal of the buffer output module is connected to a high-frequency connector, which is used to connect an external transmission cable.
[0018] In one possible implementation, the high-frequency connector is an SMA connector.
[0019] In one possible implementation, the quartz crystal oscillator test frequency divider circuit is mounted on a separate printed circuit board with mounting holes for fixed installation.
[0020] The above-described one or more technical solutions in the embodiments of this application have at least one or more of the following technical effects:
[0021] This utility model provides a frequency division circuit for testing quartz crystal oscillators. By setting a signal conditioning module to shape the waveform of the oscillator output, it effectively improves the problems of high harmonic content and non-sharp edges in non-ideal square waves, thus improving the accuracy of subsequent frequency division processing. The impedance isolation and power drive functions of the buffer output module can adaptively match the output impedance of different oscillators under test with the input impedance of the measuring equipment, significantly reducing reflection, distortion, and ringing phenomena in high-frequency signal transmission, and avoiding frequency counting errors caused by impedance mismatch. The frequency division module further improves the stability and anti-interference capability of frequency measurement by reducing the signal frequency and increasing the signal wavelength, thereby reducing signal transmission reflection. The collaborative work of each module not only solves the signal integrity problem caused by impedance mismatch under high-frequency conditions, but also overcomes the shortcomings of poor versatility of traditional conditioning circuits. It can adapt to the production and testing needs of multi-variety, small-batch quartz crystal oscillators, effectively improving the efficiency of frequency fine-tuning process and product yield.
[0022] The above description is merely an overview of the technical solution of this utility model. In order to better understand the technical means of this utility model and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this utility model more obvious and understandable, specific embodiments of this utility model are given below. Attached Figure Description
[0023] To more clearly illustrate the technical solutions in the embodiments of this utility model 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 utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0024] Figure 1 This is a schematic diagram of the overall circuit module of the quartz crystal oscillator test frequency divider circuit in the embodiment of this utility model;
[0025] Figure 2 This is a schematic diagram of the circuit principle of the quartz crystal oscillator test frequency divider circuit in the embodiment of this utility model.
[0026] Explanation of reference numerals in the attached diagram: 100, signal input interface; 200, signal conditioning module; 300, frequency divider module; 400, buffer output module; 500, circuit board. Detailed Implementation
[0027] To make the objectives, technical solutions, and advantages of this utility model clearer, the embodiments of this utility model will be described in further detail below with reference to the accompanying drawings.
[0028] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. In the following description, when referring to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this invention as detailed in the appended claims.
[0029] The overall concept of the technical solution provided by this utility model is as follows:
[0030] Please see Figures 1 to 2 The quartz crystal oscillator test frequency divider circuit includes:
[0031] The signal input interface 100 is used to connect the output signal of the quartz crystal oscillator under test. The signal input interface 100 is the physical and electrical connection point between the entire test circuit and the quartz crystal oscillator under test. Common interface forms such as high-frequency coaxial connectors, spring probes, and fixed gold-plated contacts can be selected.
[0032] The signal conditioning module 200 is electrically connected to the signal input interface 100. It is used to shape the waveform of the output signal and convert it into a differential output signal. The signal conditioning module 200 converts the potentially non-ideal high-frequency signal from the signal input interface 100 into a standard square wave with steep edges, clean logic levels, and stable amplitude, so as to provide a more ideal working signal for the subsequent frequency divider module 300.
[0033] Frequency divider module 300, whose input terminal is electrically connected to the output terminal of signal conditioning module 200, is used to perform frequency division processing on the shaped differential signal. Frequency divider module 300 performs frequency division processing on the shaped differential signal from signal conditioning module 200 to reduce the signal frequency, increase the signal wavelength, and reduce signal transmission reflection, thereby improving the stability and anti-interference capability of frequency measurement.
[0034] A buffer output module 400, whose input terminal is electrically connected to the output terminal of the frequency divider module 300, is used to provide impedance isolation and power drive for the frequency-divided signal and output it to the frequency measurement equipment. The buffer output module 400 electrically isolates the output signal of the frequency divider module 300 from the frequency measurement equipment to prevent signal reflection and interference; the buffer output module 400 provides sufficient current and voltage drive capability to ensure that the signal can be transmitted to the measurement equipment without distortion; furthermore, the buffer output module 400 buffers the signal, reducing the impact of subsequent circuits on preceding circuits and improving signal stability and reliability.
[0035] By setting the signal conditioning module 200 to shape the waveform of the oscillator output, the problems of high harmonic content and non-sharp edges in non-ideal square waves are effectively improved, enhancing the accuracy of subsequent frequency division processing. The impedance isolation and power drive functions of the buffer output module 400 can adaptively match the output impedance of different oscillators under test with the input impedance of the measuring equipment, significantly reducing reflection, distortion, and ringing phenomena in high-frequency signal transmission, and avoiding frequency counting errors caused by impedance mismatch. The frequency division module 300 further improves the stability and anti-interference capability of frequency measurement by reducing the signal frequency, increasing the signal wavelength, and reducing signal transmission reflection. The coordinated work of these modules not only solves the signal integrity problem caused by impedance mismatch under high-frequency conditions, but also overcomes the shortcomings of poor versatility of traditional conditioning circuits, adapting to the production and testing needs of multi-variety, small-batch quartz crystal oscillators, effectively improving the efficiency of frequency fine-tuning processes and product yield.
[0036] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.
[0037] In an exemplary embodiment, the signal conditioning module 200 includes a comparator and a level shifter, which are used to shape and convert the output signal into a differential signal. For example, see [link to example]. Figure 2 The signal conditioning module 200 includes a chip U2 that integrates a comparator and a level conversion output stage on the same chip. The chip U2 converts the single-ended input signal from the quartz crystal oscillator into a differential square wave signal with stable amplitude, steep edges, and strong common-mode noise suppression capability. The differential output provides extremely high signal integrity for subsequent processing.
[0038] In the exemplary embodiments, please refer to Figure 2The frequency divider module 300 is a four-way divider U3, which reduces the frequency of the output signal to one-quarter. The four-way divider U3 receives the shaped differential signal from the signal conditioning module 200 and counts the pulses of the input signal using an internal counter or trigger. For example, using a 4-way counter, one pulse is output for every four pulses counted, resulting in the frequency-divided signal, which is one-quarter of the input signal's frequency.
[0039] The frequency divider U3 reduces the frequency of the input signal to one-quarter and then transmits it to the frequency counter for measurement via the buffer output module 400. Since the measurement result only needs to be restored to the original frequency by a simple arithmetic multiplication (multiply by 4) in the computer, the signal integrity problem caused by high-frequency signal transmission is avoided. It also effectively reduces the signal reflection that is more likely to occur due to impedance discontinuity in high-frequency signal transmission and outputs a standardized low-frequency signal, thereby improving the stability and anti-interference capability of frequency measurement.
[0040] For further details, please refer to Figure 2 The frequency divider module 300 is implemented using a frequency divider with an LVPECL logic interface. LVPECL is a high-speed differential logic standard that can handle signal frequencies up to several GHz and is widely used in high-frequency and high-speed digital circuits. In this invention, the frequency divider U3 is used to divide the differential signal from the signal conditioning module 200 and output the differential signal to the buffer output module 400.
[0041] The differential input terminal of the frequency divider U3 is connected to the differential output terminal of the signal conditioning module 200 via an input resistor network; for example... Figure 2 As shown, the input termination resistor network includes resistors R4, R5, R6, and R7. The frequency divider U3 receives the differential signal output from the signal conditioning module 200, and input termination matching is achieved through resistors R4, R5, R6, and R7. These resistors are used to match the transmission impedance from the signal conditioning module 200 to the frequency divider U3, reducing signal reflection and ensuring high-frequency signal integrity.
[0042] The differential output of the frequency divider U3 is connected to the input of the buffer output module 400 via a resistor network. For example... Figure 2 As shown, the input terminal resistor network includes resistors R8, R9, R10, and R11. Similarly, these resistors match the impedance of the divider U3 to the next stage, ensuring that the signal is not distorted during transmission.
[0043] For further details, please refer to Figure 2A DC blocking capacitor C8 is connected in series between the signal input interface 100 and the input terminal of the signal conditioning module 200. The function of the DC blocking capacitor C8 is to block the DC component output by the signal input interface 100, allowing only the AC oscillation signal to pass through, thus avoiding DC bias interference with subsequent circuits.
[0044] For further details, please refer to Figure 2 A load resistor R1 is also connected in parallel at the signal input interface 100. The load resistor R1 is used to provide a matching load for the quartz crystal oscillator under test. Specifically, the load resistor R1 is connected in parallel between the output terminal of the quartz crystal oscillator under test and ground to provide AC ground for the quartz crystal oscillator under test, match the output impedance of the quartz crystal oscillator under test, and ensure the stability of the amplitude and waveform of the output signal.
[0045] In the exemplary embodiments, please refer to Figure 2 The buffer output module 400 includes a buffer U4. The input terminal of the buffer U4 is connected to the output terminal of the frequency divider U3 via a resistor network through a DC blocking capacitor C1. The buffer U4 can be a high-speed operational amplifier or a dedicated buffer chip. The buffer U4 receives one differential signal from the frequency divider module 300. Its function is to isolate the preceding and following circuits, prevent load changes from interfering with the preceding stage, and provide sufficient power to drive the signal and ensure long-distance signal transmission. The DC blocking capacitor C1 further blocks the DC component, allowing only the AC signal to enter the buffer U4, thereby preventing DC bias from affecting the buffer U4.
[0046] In an exemplary embodiment, the output terminal of the buffer output module 400 is connected to a high-frequency connector for connecting an external transmission cable. The high-frequency connector provides a physical interface for the processed test signal to achieve a reliable, low-loss, low-reflection connection with an external standard coaxial cable; it ensures that the signal can be transmitted from the PCB level to the frequency measurement equipment while maintaining signal integrity to the maximum extent. For example, the high-frequency connector is an SMA connector. SMA connectors use a threaded connection mechanism, are vibration-resistant, have reliable connections, and good repeatability. Their operating frequencies can typically reach 18 GHz or even higher, fully meeting the testing requirements of 100 MHz quartz crystal oscillators.
[0047] Furthermore, the quartz crystal oscillator test frequency divider circuit is mounted on a separate printed circuit board 500, which has mounting holes for fixed installation. By integrating all components of the quartz crystal oscillator test frequency divider circuit onto a single printed circuit board 500 and fixing it through the mounting holes, a stable and reliable physical platform can be provided for the quartz crystal oscillator test frequency divider circuit.
[0048] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.
[0049] Obviously, those skilled in the art can make various modifications and variations to the embodiments of this utility model without departing from the spirit and scope of the embodiments of this utility model. Therefore, if these modifications and variations to the embodiments of this utility model fall within the scope of the claims of this utility model and their equivalents, then this utility model also intends to include these modifications and variations.
Claims
1. A frequency divider circuit for testing a quartz crystal oscillator, characterized in that, include: A signal input interface is provided for connecting the output signal of the quartz crystal oscillator under test. A signal conditioning module, wherein the input terminal of the signal conditioning module is electrically connected to the signal input interface, is used to perform waveform shaping on the output signal and convert it into a differential output signal; The frequency divider module has its input terminal electrically connected to the output terminal of the signal conditioning module, and is used to perform frequency division processing on the shaped differential signal. A buffer output module, the input terminal of which is electrically connected to the output terminal of the frequency divider module, is used to perform impedance isolation and power drive on the frequency-divided signal and output it to a frequency measurement device.
2. The quartz crystal oscillator test frequency divider circuit according to claim 1, characterized in that, The signal conditioning module includes a comparator and a level converter, which are used to shape the output signal and convert it into a differential signal.
3. The quartz crystal oscillator test frequency divider circuit according to claim 2, characterized in that, The frequency divider module is a four-way divider, which is used to reduce the frequency of the output signal to one-quarter.
4. The quartz crystal oscillator test frequency divider circuit according to claim 3, characterized in that, The frequency divider is implemented using an LVPECL logic interface; The differential input terminal of the frequency divider is connected to the differential output terminal of the signal conditioning module through an input terminal resistor network; The differential output of the frequency divider is connected to the input of the buffer output module via an output resistor network.
5. A quartz crystal oscillator test frequency divider circuit according to claim 1, characterized in that, A DC blocking capacitor is connected in series between the signal input interface and the input terminal of the signal conditioning module.
6. The quartz crystal oscillator test frequency divider circuit according to claim 1, characterized in that, A load resistor is also connected in parallel at the signal input interface, which is used to provide a matching load for the quartz crystal oscillator under test.
7. A quartz crystal oscillator test frequency divider circuit according to claim 4, characterized in that, The buffer output module includes a buffer, and the input terminal of the buffer is connected to the output terminal of the frequency divider via a resistor network through a DC blocking capacitor.
8. A quartz crystal oscillator test frequency divider circuit according to claim 1, characterized in that, The output end of the buffer output module is connected to a high-frequency connector, which is used to connect to an external transmission cable.
9. A quartz crystal oscillator test frequency divider circuit according to claim 8, characterized in that, The high-frequency connector is an SMA connector.
10. A frequency divider circuit for testing a quartz crystal oscillator according to any one of claims 1-9, characterized in that, The quartz crystal oscillator test frequency divider circuit is mounted on a separate printed circuit board, which has mounting holes for fixed installation.