BeiDou-3 clock detection switching circuit, method and receiver

Abstract

The present application relates to a BeiDou-3 clock detection switching circuit, method and receiver. The BeiDou-3 clock detection switching circuit includes: an external clock input interface module, which is used to connect an external reference clock module; a clock detection module, which is connected to the external clock input interface module and the baseband chip, and is used to process the external clock signal output by the external clock input interface module, and output the detection signal to the baseband chip; a clock switching module, which is connected to the baseband chip, the external clock input interface module and the radio frequency chip, and is used to disconnect the internal reference clock module and the radio frequency chip after receiving the switching instruction sent by the baseband chip, and connect the external clock input interface module with the frequency chip, and output the external clock signal to the radio frequency chip. The low-cost miniaturized receiver can also meet the high-performance and high-stability navigation positioning timing requirements, and realize the stable and reliable and low-cost miniaturized design of the BeiDou receiver.

Description

Technical Field

[0001] The present application relates to the field of satellite navigation and communication technology, and in particular to a BeiDou-3 clock detection switching circuit, method and receiver. Background Art

[0002] With the official launch of the BeiDou-3 global satellite navigation system, the application of BeiDou in various industries will become more and more extensive and in-depth. Among them, there is an increasing demand for high-performance and high-stability BeiDou navigation positioning and timing, which puts higher requirements on BeiDou navigation receivers. In order to meet these requirements, the receiver needs to use a high-performance and high-stability crystal oscillator as the reference clock. Due to the size and cost limitations, the receiver is generally equipped with only a low-stability and small-sized crystal oscillator as the reference clock of the receiver, which can meet conventional application requirements, but cannot meet the high-performance and high-stability navigation positioning and timing requirements.

[0003] In order to meet the needs of high-performance and high-stability navigation, positioning and timing, the traditional solution is to replace the low-stability crystal oscillator on the receiver board with a high-stability crystal oscillator. This can meet the needs of high-performance Beidou navigation and positioning, but such receivers have the disadvantages of being large in size and high in price. Summary of the invention

[0004] Based on this, it is necessary to provide a BeiDou-3 clock detection switching circuit, method and receiver that can achieve stable and reliable BeiDou receiver and low-cost miniaturized design to address the above problems.

[0005] A BeiDou-3 clock detection switching circuit, comprising:

[0006] External clock input interface module, used to connect external reference clock module;

[0007] A clock detection module, connected to the external clock input interface module and the baseband chip, for processing the external clock signal output by the external clock input interface module and outputting a detection signal to the baseband chip;

[0008] A clock switching module, connected to the baseband chip, the external clock input interface module and the radio frequency chip, for disconnecting the internal reference clock module from the radio frequency chip after receiving a switching instruction sent by the baseband chip, connecting the external clock input interface module to the radio frequency chip, and outputting an external clock signal to the radio frequency chip;

[0009] Among them, the stability of the external reference clock module is greater than the stability of the internal reference clock module; the switching instruction is output by the baseband chip when it is determined that an external reference clock is connected according to the detection signal, and the external clock signal is used by the RF chip to generate a sampling clock and send it to the baseband chip.

[0010] In one embodiment, the clock detection module includes an operational amplifier and a detection unit, the operational amplifier is connected to the external clock input interface module and the detection unit, and the detection unit is connected to the baseband chip; the operational amplifier amplifies the external clock signal output by the external clock input interface module, and outputs the amplified signal to the detection unit, and the detection unit performs clock detection according to the amplified signal and outputs the detection signal to the baseband chip.

[0011] In one embodiment, the detection unit includes an RC filter unit and a voltage comparator, the RC filter unit is connected to the operational amplifier and the voltage comparator, and the voltage comparator is connected to the baseband chip; the RC filter unit converts the amplified signal into a DC signal and transmits it to the voltage comparator, the voltage comparator determines the size of the DC signal and outputs a detection signal to the baseband chip.

[0012] In one of the embodiments, the clock switching module includes an analog switch, an internal reference clock module and a power supply unit, the analog switch is connected to the internal reference clock module, the baseband chip, the external clock input interface module and the radio frequency chip, and the power supply unit is connected to the internal reference clock module for supplying power to the internal reference clock module;

[0013] After receiving the switching instruction sent by the baseband chip, the analog switch disconnects the internal reference clock module and the RF chip, and connects the external clock input interface module and the RF chip; when sending the switching instruction to the analog switch, the baseband chip also sends an instruction to the power supply unit to control the power supply unit to stop supplying power to the internal reference clock module.

[0014] In one of the embodiments, the power supply unit is a linear power supply, and / or the internal reference clock module is a 10 MHz temperature compensated crystal oscillator.

[0015] In one of the embodiments, the external clock input interface module includes a clock interface and an LC filtering unit, the clock interface is connected to the external reference clock module, the clock detection module and the LC filtering unit, and the LC filtering unit is connected to the clock switching module;

[0016] The clock interface receives the external clock signal output by the external reference clock module, transmits the external clock signal to the clock detection module and the LC filter unit, and the LC filter unit filters the external clock signal and transmits it to the clock switching module.

[0017] A BeiDou-3 clock detection switching method, comprising:

[0018] Receive a detection signal output by a clock detection module; the detection signal is obtained by the clock detection module processing an external clock signal output by an external clock input interface module;

[0019] When it is determined according to the detection signal that an external reference clock is connected, a switching instruction is output to the clock switching module; the switching instruction is used to control the clock switching module to disconnect the internal reference clock module from the RF chip, and connect the external clock input interface module to the RF chip, and output the external clock signal to the RF chip;

[0020] Among them, the external clock input interface module is used to connect to the external reference clock module, and the stability of the external reference clock module is greater than the stability of the internal reference clock module; the external clock signal is used by the RF chip to generate a sampling clock and send it to the baseband chip.

[0021] In one of the embodiments, when it is determined according to the detection signal that an external reference clock is connected, the method further includes:

[0022] Sending an instruction to a power supply unit in the clock switching module to control the power supply unit to stop supplying power to the internal reference clock module.

[0023] A receiver comprises a baseband chip, a radio frequency chip and the above-mentioned BeiDou-3 clock detection switching circuit.

[0024] In one of the embodiments, the RF chip is connected to the baseband chip, and the RF chip performs frequency conversion processing on the received clock signal through an internal phase-locked loop module, and outputs a sampling clock to the baseband chip.

[0025] In the above-mentioned BeiDou-3 clock detection switching circuit, method and BeiDou receiver, the clock detection module processes the external clock signal output by the external clock input interface module, and outputs the detection signal to the baseband chip. After receiving the switching instruction output by the baseband chip when it determines that an external reference clock is connected according to the detection signal, the clock switching module disconnects the internal reference clock module from the RF chip, and connects the external clock input interface module to the RF chip, and outputs the external clock signal to the RF chip. When an external reference clock module is connected, the external clock signal is output to the RF chip through the clock switching module, and there is no need to set a high-stability clock module inside the receiver, so that a low-cost and miniaturized receiver can also meet the high-performance and high-stability navigation positioning and timing requirements, and realize the stable and reliable and low-cost miniaturized design of the BeiDou receiver. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1It is a structural block diagram of a BeiDou-3 clock detection switching circuit in one embodiment;

[0027] Figure 2 A schematic diagram of the structure of a BeiDou-3 clock detection switching circuit in one embodiment;

[0028] Figure 3 The figure is a flow chart of a BeiDou-3 clock detection switching method in one embodiment. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0031] It can be understood that the “connection” in the following embodiments should be understood as “electrical connection”, “communication connection”, etc. if the connected circuits, modules, units, etc. have electrical signals or data transmission between each other.

[0032] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the relevant listed items.

[0033] In one embodiment, Figure 1 As shown, a BeiDou-3 clock detection switching circuit 100 is provided, including an external clock input interface module 110, a clock detection module 120 and a clock switching module 130. The external clock input interface module 110 is used to connect the external reference clock module 200, the clock detection module 120 connects the external clock input interface module 110 and the baseband chip 310 of the receiver 300, and the clock switching module 130 connects the baseband chip 310, the external clock input interface module 110 and the radio frequency chip 320 of the receiver 300.

[0034] The clock detection module 120 is used to process the external clock signal output by the external clock input interface module 110, and output the detection signal to the baseband chip 310; the clock switching module 130 is used to disconnect the internal reference clock module and the RF chip 320 after receiving the switching instruction sent by the baseband chip 310, and connect the external clock input interface module 110 and the RF chip 320, and output the external clock signal to the RF chip 320. Among them, the stability of the external reference clock module 200 is greater than the stability of the internal reference clock module; the switching instruction is output when the baseband chip 310 determines that an external reference clock is connected according to the detection signal, and the external clock signal is used by the RF chip 320 to generate a sampling clock and send it to the baseband chip 310.

[0035] Specifically, the stability index requirements of the external reference clock module 200 and the internal reference clock module are not unique, and can be set according to actual needs. It is only necessary to meet the stability of the external reference clock module 200 greater than the stability of the internal reference clock module. The clock signal can be provided to the RF chip 320 through the external reference clock module 200 or the internal reference clock module according to the actual scenario. The internal reference clock module can use a 10MHz crystal oscillator, specifically a 10MHz temperature compensated crystal oscillator. Correspondingly, the external reference clock module 200 can be a 10MHz high-stability clock crystal oscillator.

[0036] When the external clock input interface module 110 is connected to the external reference clock module 200, the baseband chip 310 determines that the external reference clock is connected according to the detection signal of the clock detection module 120, outputs a switching instruction to the clock switching module 130, controls the clock switching module 130 to switch, disconnects the connection between the internal reference clock module and the RF chip 320, and connects the external clock input interface module 110 and the RF chip 320, and the external reference clock module 200 provides the clock signal for the RF chip 320; if the external clock input interface module 110 is not connected to the external reference clock module 200, the baseband chip 310 will not output a switching instruction, the clock switching module 130 maintains the connection between the internal reference clock module and the RF chip 320, and the internal reference clock module provides the clock signal for the RF chip 320. The RF chip 320 generates a sampling clock according to the received clock signal and sends it to the baseband chip 310. By using clocks with different precision and stability, navigation timing functions with different positioning precisions can be realized, thereby meeting different application requirements.

[0037] The above-mentioned Beidou-3 clock detection switching circuit, when an external reference clock module 200 is connected, outputs an external clock signal to the RF chip 320 through the clock switching module 130. There is no need to set a high-stability clock module inside the receiver, so that a low-cost and miniaturized receiver can also meet the requirements of high-performance and high-stability navigation, positioning and timing, thereby realizing the stable, reliable and low-cost miniaturized design of the Beidou receiver.

[0038] In one embodiment, Figure 2 As shown, the external clock input interface module 110 includes a clock interface and an LC filter unit 112. The clock interface is connected to the external reference clock module 200, the clock detection module 120 and the LC filter unit 112. The LC filter unit 112 is connected to the clock switching module 130. The clock interface receives the external clock signal output by the external reference clock module 200, and transmits the external clock signal to the clock detection module 120 and the LC filter unit 112. The LC filter unit 112 filters the external clock signal and transmits it to the clock switching module 130. After the external clock signal is received, it is divided into two paths. One path is filtered by the LC filter unit 112 and input to the clock switching module 130, and the other path is input to the clock detection module 120 for processing. The received external clock signal is filtered by the LC filter unit 112 to filter out high-order harmonics and some interference noise.

[0039] In one embodiment, continue to refer to Figure 2 The clock detection module 120 includes an operational amplifier 122 and a detection unit 124. The operational amplifier 122 is connected to the external clock input interface module 110 and the detection unit 124. The detection unit 124 is connected to the baseband chip 310. The operational amplifier 122 amplifies the external clock signal output by the external clock input interface module 110, and outputs the amplified signal to the detection unit 124. The detection unit 124 performs clock detection according to the amplified signal and outputs the detection signal to the baseband chip 310.

[0040] Specifically, the operational amplifier 122 is connected to the clock interface in the external clock input interface module 110, and the operational amplifier 122 is used as a clock driver to amplify the external clock signal. Taking the external clock signal provided by the 10MHz crystal oscillator as an example, the operational amplifier 122 only needs to have an operating frequency of 10MHz. The operational amplifier 122 has a large input impedance, which is close to an open circuit, so it will not affect the signal quality of the external reference clock. The operational amplifier 122 can also amplify the reference clock to facilitate subsequent power detection. Using an ordinary operational amplifier 122 can well solve the problem of the clock detection module 120 affecting the quality of the clock signal, and can also ensure a low-cost design.

[0041] Further, the detection unit 124 includes an RC filter unit 1242 and a voltage comparator 1244, the RC filter unit 1242 is connected to the operational amplifier 122 and the voltage comparator 1244, and the voltage comparator 1244 is connected to the baseband chip 310; the RC filter unit 1242 converts the amplified signal into a DC signal and transmits it to the voltage comparator 1244, the voltage comparator 1244 determines the magnitude of the DC signal, and outputs a detection signal to the baseband chip 310. Specifically, the input periodic signal is first converted into a DC voltage by the RC filter unit 1242, the magnitude of the voltage is related to the amplitude of the input signal, and then the voltage is determined by the voltage comparator 1244 to detect whether the external reference clock exists, and the detection signal is output to the baseband chip 310 for subsequent switching control. Only one RC filter unit 1242 and a voltage comparator 1244 are needed to replace the detection function of the power detection chip, and no software is required to be implemented, and the circuit cost is very low, which meets the requirements of low-cost receivers.

[0042] In one embodiment, Figure 2 As shown, the clock switching module 130 includes an analog switch 132, an internal reference clock module 134 and a power supply unit 136. The analog switch 132 is connected to the internal reference clock module 134, the baseband chip 310, the external clock input interface module 110 and the RF chip 320. The power supply unit 136 is connected to the internal reference clock module 134 and is used to supply power to the internal reference clock module 134. After receiving the switching instruction sent by the baseband chip 310, the analog switch 132 disconnects the internal reference clock module 134 and the RF chip 320, and connects the external clock input interface module 110 and the RF chip 320. When sending the switching instruction to the analog switch 132, the baseband chip 310 also sends an instruction to the power supply unit 136 to control the power supply unit 136 to stop supplying power to the internal reference clock module 134.

[0043] Among them, the analog switch 132 can be specifically connected to the LC filter unit 112 in the external clock input interface module 110, and a common analog switch device is used to realize line switching, which can also reduce costs. The power supply unit 136 can be a linear power supply, and the internal reference clock module 134 is powered by the linear power supply to ensure the low-cost miniaturization design of the receiver. The internal reference clock module 134 specifically uses a 10MHz temperature-compensated crystal oscillator. After detecting that there is an external reference clock input, the receiver will automatically switch to the external reference clock for operation. In addition, due to the isolation problem of the analog switch, the clock inside the receiver and the external clock will couple with each other to increase the noise level. In order to solve this problem, after switching to the external reference clock for operation, the power supply of the internal temperature-compensated crystal oscillator is also turned off, thereby turning off the output of the internal reference clock, so that the stability of the reference clock can be ensured, and then the positioning accuracy of the receiver can be ensured. It can be understood that if there is no external reference clock input, the analog switch 132 continues to maintain the connection between the internal reference clock module 134 and the RF chip 320, and uses the internal 10MHz temperature-compensated crystal oscillator to provide a clock signal for the RF chip 320.

[0044] Specifically, the clock switching module 130 selects a 10MHz clock for the receiver as a reference signal input to the RF chip 320, and the phase-locked loop module inside the RF chip 320 converts the frequency to output a 62MHz clock signal to the baseband chip 310 as a sampling clock. The baseband chip 310 uses this sampling clock to collect satellite signals for subsequent signal processing. Using 10MHz clocks of different accuracy and stability, the receiver can achieve navigation timing functions with different positioning accuracy, thereby meeting different application requirements.

[0045] In one embodiment, a BeiDou-3 clock detection switching method is also provided, which is implemented based on a baseband chip, such as Figure 3 As shown, the method includes:

[0046] Step S110: receiving a detection signal output by the clock detection module; the detection signal is obtained by the clock detection module processing the external clock signal output by the external clock input interface module.

[0047] Step S120: When it is determined that an external reference clock is connected according to the detection signal, a switching instruction is output to the clock switching module; the switching instruction is used to control the clock switching module to disconnect the internal reference clock module from the RF chip, and connect the external clock input interface module to the RF chip, and output the external clock signal to the RF chip. Among them, the external clock input interface module is used to connect the external reference clock module, and the stability of the external reference clock module is greater than the stability of the internal reference clock module; the external clock signal is used by the RF chip to generate a sampling clock and send it to the baseband chip.

[0048] Furthermore, when it is determined according to the detection signal that an external reference clock is connected, the method further includes step S130: sending an instruction to a power supply unit in the clock switching module to control the power supply unit to stop supplying power to the internal reference clock module.

[0049] It can be understood that the specific structures of the external clock input interface module, the clock detection module and the clock switching module have been explained in detail in the above-mentioned Beidou-3 clock detection switching circuit, and will not be repeated here.

[0050] In one embodiment, Figure 2 As shown, a receiver 300 is also provided, including a baseband chip 310, a radio frequency chip 320 and the above-mentioned BeiDou-3 clock detection switching circuit 100. The radio frequency chip 320 is connected to the baseband chip 310, and the radio frequency chip 320 performs frequency conversion processing on the received clock signal through an internal phase-locked loop module, and outputs a sampling clock to the baseband chip 310. The baseband chip 310 uses the sampling clock to collect satellite signals for subsequent signal processing.

[0051] Specifically, the BeiDou-3 global satellite navigation system has been officially launched. The application of BeiDou in various industries will become more and more extensive and in-depth. Among them, the demand for high-performance and high-stability BeiDou navigation positioning is also increasing, which puts higher requirements on BeiDou navigation receivers. As a key component of the receiver, the crystal oscillator directly determines the performance of the receiver. In high-demand applications, a high-performance and high-stability crystal oscillator must be used as the reference clock. The main problems are: (1) High-performance crystal oscillators are not only expensive, but also large in size, which conflicts with the low-cost and miniaturization requirements of the navigation receiver board and is not suitable for being placed on the receiver board; (2) As a key component of the navigation receiver, once the crystal oscillator is damaged and fails, the entire receiver will be unusable. Therefore, a clock detection switching device is required on the receiver to automatically switch between the internal and external clocks. When an external high-stability reference clock input is detected, it switches to the external clock. When the external high-stability crystal oscillator is damaged and fails, it automatically switches to the internal ordinary crystal oscillator to ensure the stability and reliability of the receiver. (3) The receiver reference clock is generally a low-frequency signal of 10MHz. The general solution is to use a dedicated detection chip for power detection and switch it through software control. This detection and switching solution is relatively complex to implement, has a high price and cost, and will affect the quality of the clock signal. It is not suitable for detecting the reference clock; (4) The internal and external reference clocks are usually switched by switches. Due to the isolation problem of the switch, the two reference clocks will couple with each other and increase the noise, which will cause the carrier phase calculated by the navigation receiver to jitter.

[0052] Aiming at the high-performance and high-stability navigation positioning and timing requirements of BeiDou-3, this application provides a BeiDou-3 clock detection switching circuit, method and receiver, which realizes the automatic switching between the external high-stability crystal oscillator and the internal ordinary crystal oscillator of the receiver, ensuring the stability and reliability of the BeiDou receiver and the low-cost miniaturized design. Its advantages are mainly reflected in the following aspects:

[0053] 1. Through the BeiDou-3 clock detection switching circuit 100, a low-cost and miniaturized ordinary receiver can also meet the requirements of high-performance and high-stability navigation positioning and timing.

[0054] 2. A BeiDou-3 clock detection switching circuit 100 is added to the receiver. When the external high-stability crystal oscillator is damaged or fails, it automatically switches to the internal ordinary crystal oscillator, thereby improving the reliability of the receiver.

[0055] 3. The BeiDou-3 clock detection and switching circuit 100 can realize automatic detection and switching of the external clock using only ordinary operational amplifiers and comparators. The circuit cost is very low and the implementation is very simple, which meets the requirements of low-cost receivers.

[0056] 4. The BeiDou-3 clock detection switching circuit 100 uses an operational amplifier to implement signal detection and turns off the internal ordinary crystal oscillator while performing clock switching, thus solving the problem of affecting the quality of the 10MHz clock signal.

[0057] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0058] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A BeiDou-3 clock detection switching circuit, characterized in that: include: External clock input interface module, used to connect external reference clock module; A clock detection module, connected to the external clock input interface module and the baseband chip, for processing the external clock signal output by the external clock input interface module and outputting a detection signal to the baseband chip; A clock switching module, connected to the baseband chip, the external clock input interface module and the radio frequency chip, for disconnecting the internal reference clock module from the radio frequency chip after receiving a switching instruction sent by the baseband chip, connecting the external clock input interface module to the radio frequency chip, and outputting an external clock signal to the radio frequency chip; Among them, the stability of the external reference clock module is greater than the stability of the internal reference clock module; the switching instruction is output by the baseband chip when it is determined that an external reference clock is connected according to the detection signal, and the external clock signal is used by the RF chip to generate a sampling clock and send it to the baseband chip; if the external clock input interface module is not connected to the external reference clock module, the baseband chip does not output the switching instruction, the clock switching module maintains the connection between the internal reference clock module and the RF chip, and the internal reference clock module provides the RF chip with a clock signal; the RF chip generates a sampling clock according to the received clock signal and sends it to the baseband chip, so that the baseband chip can realize navigation timing functions with different positioning accuracies; The clock switching module includes an analog switch, an internal reference clock module and a power supply unit, the analog switch is connected to the internal reference clock module, the baseband chip, the external clock input interface module and the radio frequency chip, and the power supply unit is connected to the internal reference clock module for supplying power to the internal reference clock module; After receiving the switching instruction sent by the baseband chip, the analog switch disconnects the internal reference clock module and the radio frequency chip, and connects the external clock input interface module and the radio frequency chip; when sending the switching instruction to the analog switch, the baseband chip also sends an instruction to the power supply unit to control the power supply unit to stop supplying power to the internal reference clock module; The clock detection module includes an operational amplifier and a detection unit, the operational amplifier is connected to the external clock input interface module and the detection unit, and the detection unit is connected to the baseband chip; the operational amplifier amplifies the external clock signal output by the external clock input interface module, and outputs the amplified signal to the detection unit, and the detection unit performs clock detection according to the amplified signal, and outputs the detection signal to the baseband chip; the detection unit includes an RC filter unit and a voltage comparator, the RC filter unit is connected to the operational amplifier and the voltage comparator, and the voltage comparator is connected to the baseband chip; the RC filter unit converts the amplified periodic signal into a DC signal whose voltage magnitude is related to the input signal amplitude and transmits it to the voltage comparator, and the voltage comparator determines the magnitude of the DC signal and outputs the detection signal to the baseband chip; The external clock input interface module includes a clock interface and an LC filtering unit, the clock interface is connected to the external reference clock module, the clock detection module and the LC filtering unit, and the LC filtering unit is connected to the clock switching module; the clock interface receives the external clock signal output by the external reference clock module, transmits the external clock signal to the clock detection module and the LC filtering unit, and the LC filtering unit filters the external clock signal and transmits it to the clock switching module.

2. The circuit according to claim 1, characterized in that The power supply unit is a linear power supply.

3. The circuit according to claim 2, characterized in that The internal reference clock module is a 10MHz temperature compensated crystal oscillator.

4. A BeiDou-3 clock detection switching method, characterized in that: include: Receive a detection signal output by a clock detection module; the detection signal is obtained by the clock detection module processing an external clock signal output by an external clock input interface module; When it is determined according to the detection signal that an external reference clock is connected, a switching instruction is output to the clock switching module; the switching instruction is used to control the clock switching module to disconnect the internal reference clock module from the RF chip, and connect the external clock input interface module to the RF chip, and output the external clock signal to the RF chip; Among them, the external clock input interface module is used to connect the external reference clock module, and the stability of the external reference clock module is greater than the stability of the internal reference clock module; the external clock signal is used for the RF chip to generate a sampling clock and send it to the baseband chip; if the external clock input interface module is not connected to the external reference clock module, the baseband chip does not output a switching instruction, and the clock switching module maintains the connection between the internal reference clock module and the RF chip, and the internal reference clock module provides a clock signal for the RF chip; the RF chip generates a sampling clock according to the received clock signal and sends it to the baseband chip, so that the baseband chip can realize navigation timing functions with different positioning accuracies; The clock switching module includes an analog switch, an internal reference clock module and a power supply unit. The analog switch is connected to the internal reference clock module, the baseband chip, the external clock input interface module and the radio frequency chip. The power supply unit is connected to the internal reference clock module and is used to supply power to the internal reference clock module. After receiving the switching instruction sent by the baseband chip, the analog switch disconnects the internal reference clock module from the radio frequency chip and connects the external clock input interface module to the radio frequency chip. When sending the switching instruction to the analog switch, the baseband chip also sends an instruction to the power supply unit to control the power supply unit to stop supplying power to the internal reference clock module. The clock detection module includes an operational amplifier and a detection unit, the operational amplifier is connected to the external clock input interface module and the detection unit, and the detection unit is connected to the baseband chip; the operational amplifier amplifies the external clock signal output by the external clock input interface module, and outputs the amplified signal to the detection unit, and the detection unit performs clock detection according to the amplified signal, and outputs the detection signal to the baseband chip; the detection unit includes an RC filter unit and a voltage comparator, the RC filter unit is connected to the operational amplifier and the voltage comparator, and the voltage comparator is connected to the baseband chip; the RC filter unit converts the amplified periodic signal into a DC signal whose voltage magnitude is related to the input signal amplitude and transmits it to the voltage comparator, and the voltage comparator determines the magnitude of the DC signal and outputs the detection signal to the baseband chip; The external clock input interface module includes a clock interface and an LC filtering unit, the clock interface is connected to the external reference clock module, the clock detection module and the LC filtering unit, and the LC filtering unit is connected to the clock switching module; the clock interface receives the external clock signal output by the external reference clock module, transmits the external clock signal to the clock detection module and the LC filtering unit, and the LC filtering unit filters the external clock signal and transmits it to the clock switching module.

5. A receiver, characterized in that: It comprises a baseband chip, a radio frequency chip and the BeiDou-3 clock detection switching circuit as described in any one of claims 1 to 3.

6. The receiver according to claim 5, characterized in that The radio frequency chip is connected to the baseband chip, and the radio frequency chip performs frequency conversion processing on the received clock signal through an internal phase-locked loop module, and outputs a sampling clock to the baseband chip.

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