Wideband out-of-band reference circuitry for radio frequency transceiver systems

Abstract

The application relates to a wideband out-of-reference circuit system suitable for a radio frequency transceiving system, which comprises a logic converter, a phase-locked loop circuit and a frequency division filter circuit and an output amplification module.The logic converter is used for converting a reference input signal into a square wave reference signal; the phase-locked loop circuit is used for locking the frequency of an internal crystal oscillator to a preset high frequency through phase comparison and loop filtering control; the frequency division filter circuit is used for dividing the high frequency signal into a preset target fixed frequency signal through a multi-stage frequency division technology and filtering the signal after each frequency division process; and the output amplification module is used for power adjusting the target fixed frequency signal and outputting a final reference signal.The wideband out-of-reference circuit system suitable for the radio frequency transceiving system can allow a wider frequency range of reference signal input and break away from the limitation of a single 10MHz reference signal; and can provide a stable and high-precision 10MHz reference signal with low noise.The application is an independent module and can be assembled according to actual application.

Description

Technical Field

[0001] This invention relates to the field of radio frequency transceiver systems, and more particularly to the field of reference phase-locked loop technology with variable external reference signals, specifically a broadband external reference circuit system suitable for radio frequency transceiver systems. Background Technology

[0002] External reference signals are a critical component of radio frequency (RF) systems. They are typically stable signals from external devices or signal sources, providing a reference for frequency, time, or phase. These signals are essential for the synchronization, stability, and accuracy of the RF system, especially in applications requiring high-precision clock synchronization or frequency stability. External reference signals are usually generated by highly stable oscillators (such as crystal oscillators, temperature-compensated oscillators, atomic clocks, etc.) and play multiple roles in the system.

[0003] In radio frequency (RF) systems, the most common applications of external reference signals are clock synchronization and frequency synthesis. By providing a unified clock reference, external reference signals ensure the synchronization of various components within the system, preventing signal loss or errors caused by clock asynchrony. During frequency synthesis, external reference signals provide a stable reference for the frequency synthesizer, enabling the system to generate accurate and stable RF signals to meet various communication and measurement requirements.

[0004] Furthermore, external reference signals are widely used in signal measurement and calibration of radio frequency systems. By comparing the external reference signal with the system output signal, engineers can accurately measure important parameters such as the system's frequency, phase, and amplitude, ensuring the stability and reliability of system performance. For systems requiring high precision (such as satellite communications and radar systems), external reference signals are a core element in ensuring system accuracy.

[0005] However, the common drawbacks of some external reference signal systems are their support for fixed frequencies, poor specifications, and poor stability, which significantly affect the overall performance of the RF system. First, the fixed frequency limitation means the system cannot flexibly adjust the frequency to meet different application requirements, making it unsuitable for scenarios requiring dynamic frequency changes. Second, poor specifications typically refer to poor frequency stability, high noise, or unstable latency of the signal source, resulting in low-quality output signals and consequently affecting communication accuracy and reliability. Finally, poor stability causes signal fluctuations during long-term operation, affecting the system's sustained performance, especially in high-precision applications, potentially leading to synchronization failures or data errors. Therefore, these drawbacks limit the widespread application of external reference signals in some demanding RF applications. A key technical challenge is how to achieve precise locking of a wide-frequency-range, low-quality external reference signal using a simple, low-cost circuit while ensuring low phase noise and low harmonics in the output signal. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a broadband external reference circuit system that is accurate, stable, robust, and widely applicable to radio frequency transceiver systems.

[0007] To achieve the above objectives, the broadband external reference circuit system of the present invention, applicable to radio frequency transceiver systems, is as follows: The main feature of this broadband external reference circuit system suitable for radio frequency transceiver systems is that the system includes: A logic converter that receives a variable frequency reference input signal at its input terminal and converts the reference input signal into a square wave reference signal; A phase-locked loop circuit, connected to the logic converter, is used to receive a square wave reference signal, control the internal crystal oscillator through phase comparison and loop filtering, lock the frequency to a preset high-frequency frequency, and output the corresponding high-frequency signal. The frequency division filter circuit has its input terminal connected to the output terminal of the phase-locked loop circuit. It is used to divide the high-frequency signal to a preset target fixed frequency signal using multi-level frequency division technology, and to filter the signal after each frequency division process. The output amplifier module, connected to the frequency divider filter circuit, is used to adjust the power of the target fixed frequency signal and output the final reference signal.

[0008] Preferably, the phase-locked loop circuit includes a phase detector, a loop filter, and a crystal oscillator, which are connected in sequence. The phase detector is used to compare the square wave reference signal output by the logic converter with the feedback signal output by the crystal oscillator. If the frequency of the feedback signal is higher than the frequency of the square wave reference signal, the control voltage of the crystal oscillator is reduced; if the frequency of the feedback signal is lower than the frequency of the square wave reference signal, the control voltage of the crystal oscillator is increased until the frequency of the feedback signal matches the frequency of the square wave reference signal.

[0009] Preferably, the frequency division filtering circuit includes a first-stage frequency divider, a first-stage filter, a second-stage frequency divider, and a second-stage filter connected in sequence. The first-stage frequency divider and the second-stage frequency divider are used to divide the high-frequency signal to a preset target fixed frequency signal. The first-stage filter and the second-stage filter are used to filter the signal after the frequency division processing.

[0010] Preferably, the system further includes a control circuit module connected to the phase-locked loop circuit, which is used to receive an input reference frequency value, automatically calculate and adjust the phase detection frequency and locking speed of the phase-locked loop circuit based on the reference frequency value, and read the locking state of the phase-locked loop circuit.

[0011] Preferably, the control circuit module is also used to calculate reference frequency configuration parameters, control the division number of the frequency divider in the phase-locked loop circuit, and calculate the reference input signal with a resolution accurate to 1Hz.

[0012] Preferably, the system further includes a power supply circuit module, which is connected to the logic converter, phase-locked loop circuit, frequency divider filter circuit and output amplifier module respectively, for converting the external input voltage into the voltage required by each device and providing separate power supply for circuits of different frequency bands.

[0013] Preferably, the radio frequency signal lines between the logic converter, the phase-locked loop circuit, the frequency divider filter circuit, and the output amplifier module adopt a point-to-point straight-line connection structure, and grounding shielding holes are arranged on both sides of the radio frequency signal lines.

[0014] Preferably, the frequency range of the reference input signal is 10MHz to 100MHz, the preset high frequency is 500MHz, and the frequency of the target fixed frequency signal is 10MHz.

[0015] The broadband external reference circuit system of this invention, suitable for radio frequency transceiver systems, allows for a wider frequency range of reference signal input, overcoming the limitation of a single 10MHz reference signal; it can provide a stable, high-precision, low-noise 10MHz reference signal. This invention is a standalone module and can be selected for assembly according to actual applications. Attached Figure Description

[0016] Figure 1 This is a hardware functional block diagram of the broadband external reference circuit system applicable to radio frequency transceiver systems of the present invention.

[0017] Figure 2 The measured phase noise diagram is shown for the broadband external reference circuit system applicable to radio frequency transceiver systems of the present invention.

[0018] Figure 3 The present invention provides a control interface for a broadband external reference circuit system applicable to radio frequency transceiver systems.

[0019] Figure 4 The present invention provides a physical circuit diagram of a broadband external reference circuit system applicable to radio frequency transceiver systems. Detailed Implementation

[0020] To more clearly describe the technical content of the present invention, the following description is provided in conjunction with specific embodiments.

[0021] The broadband external reference circuit system of the present invention, applicable to radio frequency transceiver systems, includes: A logic converter that receives a variable frequency reference input signal at its input terminal and converts the reference input signal into a square wave reference signal; A phase-locked loop circuit, connected to the logic converter, is used to receive a square wave reference signal, control the internal crystal oscillator through phase comparison and loop filtering, lock the frequency to a preset high-frequency frequency, and output the corresponding high-frequency signal. The frequency division filter circuit has its input terminal connected to the output terminal of the phase-locked loop circuit. It is used to divide the high-frequency signal to a preset target fixed frequency signal using multi-level frequency division technology, and to filter the signal after each frequency division process. The output amplifier module, connected to the frequency divider filter circuit, is used to adjust the power of the target fixed frequency signal and output the final reference signal.

[0022] In a preferred embodiment of the present invention, the phase-locked loop circuit includes a phase detector, a loop filter, and a crystal oscillator, which are connected in sequence. The phase detector is used to compare the square wave reference signal output by the logic converter with the feedback signal output by the crystal oscillator. If the frequency of the feedback signal is higher than the frequency of the square wave reference signal, the control voltage of the crystal oscillator is reduced; if the frequency of the feedback signal is lower than the frequency of the square wave reference signal, the control voltage of the crystal oscillator is increased until the frequency of the feedback signal matches the frequency of the square wave reference signal.

[0023] In a preferred embodiment of the present invention, the frequency division filtering circuit includes a first-stage frequency divider, a first-stage filter, a second-stage frequency divider, and a second-stage filter connected in sequence. The first-stage frequency divider and the second-stage frequency divider are used to divide the high-frequency signal to a preset target fixed frequency signal. The first-stage filter and the second-stage filter are used to filter the signal after the frequency division processing.

[0024] In a preferred embodiment of the present invention, the system further includes a control circuit module connected to the phase-locked loop circuit, which is used to receive an input reference frequency value, automatically calculate and adjust the phase detection frequency and locking speed of the phase-locked loop circuit according to the reference frequency value, and read the locking state of the phase-locked loop circuit.

[0025] In a preferred embodiment of the present invention, the control circuit module is also used to calculate the reference frequency configuration parameters, control the division number of the frequency divider in the phase-locked loop circuit, and calculate the reference input signal with a resolution accurate to 1Hz.

[0026] In a preferred embodiment of the present invention, the system further includes a power supply circuit module, which is connected to the logic converter, phase-locked loop circuit, frequency divider filter circuit and output amplifier module respectively, for converting the external input voltage into the voltage required by each device and providing separate power supply for circuits of different frequency bands.

[0027] In a preferred embodiment of the present invention, the radio frequency signal lines between the logic converter, the phase-locked loop circuit, the frequency divider filter circuit and the output amplifier module adopt a point-to-point straight connection structure, and grounding shielding holes are arranged on both sides of the radio frequency signal lines.

[0028] In a preferred embodiment of the present invention, the frequency range of the reference input signal is 10MHz to 100MHz, the preset high frequency is 500MHz, and the frequency of the target fixed frequency signal is 10MHz.

[0029] This invention belongs to the field of reference phase-locked loop technology for variable external reference signals in radio frequency transceiver systems, and converts a variable input reference signal into a precise, stable and low-phase-noise 10 MHz reference signal.

[0030] The problem solved by this invention is: 1. Allows for wider bandwidth external reference signal input; 2. The external reference input signal has Hz-level resolution; 3. Fixing the reference signal to a specific frequency with high stability minimizes its impact on the overall circuit. 4. The generated 10MHz signal has extremely low phase noise and does not affect the phase noise of the RF transceiver system; 5. The front-end logic converter implements waveform shaping, expanding its applicability and system robustness.

[0031] To solve the above problems, the present invention adopts the following technical solution: The overall circuit can be divided into three parts: power supply circuit, control circuit, and signal processing circuit.

[0032] The power supply section provides separate power to the signal processing circuits for each frequency band to avoid the power supply circuit affecting the circuits processing different frequency bands.

[0033] The control circuit can be controlled via software, allowing for free adjustment of the phase-locked loop's phase detection frequency and locking speed based on the input reference frequency. It also supports external reference input calculations accurate to 1Hz.

[0034] The signal processing circuit is the focus of this invention. Figure 1As shown, the variable-frequency reference input signal is first converted into a square-wave reference signal for easier processing by the phase-locked loop (PLL) chip. The phase detector compares the reference signal with the feedback signal from the crystal oscillator and corrects the frequency generated by the crystal oscillator based on the comparison result. If the feedback frequency is higher than the reference frequency, the control voltage on the crystal oscillator is reduced; if the feedback frequency is lower than the reference frequency, the control voltage on the crystal oscillator is increased until the feedback frequency matches the reference frequency, at which point the PLL will stably lock at that frequency. A specially designed loop filter is used, which, compared to traditional locking schemes, more effectively reduces phase noise and improves signal quality. Subsequent signal processing employs multi-stage frequency division technology, dividing the locked frequency to the required fixed frequency. After each division, a specially designed filter is added to remove harmonics and other interference signals, further improving signal quality. At the output end, an amplifier adjusts the output signal power to meet the requirements of the RF transceiver system.

[0035] In a specific embodiment of the present invention, the physical object is shown in the figure below. Figure 4 As shown, the power input port is located at the bottom left, and the control signal input port is at the top. Signals from 10 to 100 MHz are input through the connector at the bottom right and output through the connector at the top right after signal processing. This invention locks the 10-100 MHz signal to 10 MHz, offering advantages such as good phase noise and low harmonics. For example, when the input reference signal is 12.3456 MHz, with the input reference frequency configured at 12.3456 MHz, R divider set to 1, and reference multiplier enabled, the resulting 10 MHz output signal has a power of 4.6 dBm, a harmonic distortion of -50 dBc, and a phase noise level as shown. Figure 2 As shown. Figure 2 The purple area represents the phase noise of the oscilloscope's 10MHz reference signal; the blue area represents the phase noise of the circuit's 10MHz output signal.

[0036] The power supply circuit converts the input 12V voltage to the voltage required by each device and provides separate power supply for each frequency band circuit, reducing the impact of the power supply circuit on the radio frequency signal.

[0037] The control circuit section can be controlled via software. Figure 3 The control shown allows for the control of the overall circuit's power supply enable. When this function is not used, the module can be shut down to reduce power consumption. The control signal can precisely control the division ratio of the frequency divider within the phase-locked loop (PLL) chip, the phase detection frequency, and other functions, and can read the PLL's locking status to provide feedback to the operator. Through software development, it can support automatic calculation and configuration of relevant parameters based on the user-input reference frequency. Even with an external reference input signal accurate to the Hz, it can still accurately lock to 10MHz.

[0038] In the signal processing circuit, the conventional approach is for the user manual to specify a TTL level square wave with a limited rise time, pushing the problem onto the user. This invention, however, incorporates intelligent conversion, eliminating the need for the user to worry about the signal type; it's plug-and-play. The input 10-100MHz signal is converted into a low-phase-noise square wave signal by a logic converter. This signal is then compared with the signal generated by the crystal oscillator in the phase-locked loop chip, and the crystal oscillator is controlled accordingly until the loop locks the frequency to a precise 500MHz. Frequency divider-1 and frequency divider-2 then divide the 500MHz signal to 10MHz, with filtering performed after each division to effectively reduce harmonic interference. Furthermore, the RF signals between components are directly connected point-to-point, and numerous shielding gaps are placed on both sides of the lines to further reduce external interference to the RF signal.

[0039] The phase noise of the output signal was effectively reduced by optimizing the loop filter through simulation. The final output phase noise at 10MHz is as follows: Figure 2 As shown, the purple line represents the phase noise measured by the spectrum analyzer at its own 10MHz reference output, while the blue and yellow lines represent the phase noise of the 10MHz signal generated by the present invention under different configurations. The blue line represents the phase noise of the final actual output. Analysis of the figure shows that the phase noise generated by the present invention is basically consistent with the phase noise of the testing equipment itself, and the actual phase noise will not be higher than the instrument's own phase noise.

[0040] Therefore, this invention can convert an input 10-100MHz signal into a precise and stable 10MHz reference signal with low harmonics and low phase noise, enabling the RF transceiver system to adapt to more scenarios and laying the foundation for the system's accuracy.

[0041] The purpose of this invention is to provide a high-quality, wideband external reference signal for radio frequency (RF) transceiver systems, focusing on optimizing the phase noise and signal purity of the circuit itself. This invention focuses on the RF front-end signal chain itself, aiming to solve the technical problem of "how to provide an RF system with an extremely low phase noise and high purity reference source".

[0042] The technical solution of this invention adopts a series processing link: external reference input → square wave conversion → phase detection → voltage-controlled crystal oscillator correction → loop filter optimization → multi-stage frequency division + filtering → power amplifier output. After PLL locking, this invention also adds refined processing links such as multi-stage frequency division and power adjustment.

[0043] The technical solution of this invention features a specially designed loop filter to reduce phase noise; it has multi-stage frequency division and targeted filters, with harmonics filtered out after each stage of frequency division, further improving signal quality; and the output power is adjusted by the output amplifier to meet the requirements of the RF system.

[0044] Through the aforementioned targeted design, this invention achieves lower phase noise, cleaner spectral characteristics, and adjustable output power, directly serving the stringent signal quality requirements of radio frequency transceiver systems.

[0045] The core innovation of the technical solution of this invention lies in the organic combination of multiple technical features, namely, software-controllable precise configuration → PLL locking to high frequency → multi-level frequency division and filtering for step-by-step purification → adjustable output power → independent power supply guarantee. This complete signal purification chain, as a whole, has not been disclosed in the prior art.

[0046] The technical solution of the present invention has a cascaded structure of multi-level frequency division and independent filtering at each level. By setting a specially designed filter after each frequency division, the harmonics and spurious signals generated by the frequency division can be filtered out step by step. Compared with single frequency division or unified filtering after frequency division, the spectral purity of the final output signal can be significantly improved.

[0047] The technical solution of this invention adjusts the output signal power through an output amplification module. The output amplifier allows the reference signal power to be adjusted according to the needs of the RF transceiver system, providing flexibility in interface adaptation. The reference signal in the comparison document is only for internal use within the module and does not require power adjustment.

[0048] The technical solution of this invention reduces phase noise through targeted design of PLL loop filter, and through simulation optimization of loop filter, makes the phase noise of output signal basically the same as the reference phase noise of high-end instrument itself.

[0049] The technical solution of the present invention calculates the reference input signal with a resolution accurate to 1Hz, realizing 1Hz-level accurate calculation of the external reference input frequency and automatic parameter configuration, such as locking 12.3456MHz to 10MHz.

[0050] The technical solution of this invention provides separate power supplies for circuits of different frequency bands. By providing independent power supplies, power coupling interference between circuits of different frequency bands is avoided, which is a system-level noise suppression method.

[0051] The technical solution of this invention features a point-to-point linear radio frequency signal line and a grounding shielding hole. By optimizing the PCB layout, it reduces external interference and radiation of the radio frequency signal, which is an anti-interference measure combined with the hardware design level.

[0052] The technical solution of this invention achieves intelligent waveform shaping through a logic converter. This invention incorporates a logic converter that automatically converts external reference signals into low-phase-noise square waves, eliminating the need for users to focus on the input signal type and enabling plug-and-play functionality. Specific implementation details of this embodiment can be found in the relevant descriptions in the above embodiments, and will not be repeated here.

[0053] It is understood that the same or similar parts in the above embodiments can be referred to each other, and the contents not described in detail in some embodiments can be referred to the same or similar contents in other embodiments.

[0054] It should be noted that in the description of this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means at least two.

[0055] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0056] The broadband external reference circuit system of this invention, suitable for radio frequency transceiver systems, allows for a wider frequency range of reference signal input, overcoming the limitation of a single 10MHz reference signal; it can provide a stable, high-precision, low-noise 10MHz reference signal. This invention is a standalone module and can be selected for assembly according to actual applications.

[0057] In this specification, the invention has been described with reference to specific embodiments thereof. However, it will be apparent that various modifications and variations can be made without departing from the spirit and scope of the invention. Therefore, the specification and drawings should be considered illustrative rather than restrictive.

Claims

1. A broadband external reference circuit system suitable for radio frequency transceiver systems, characterized in that, The system includes: A logic converter that receives a variable frequency reference input signal at its input terminal and converts the reference input signal into a square wave reference signal; A phase-locked loop circuit, connected to the logic converter, is used to receive a square wave reference signal, control the internal crystal oscillator through phase comparison and loop filtering, lock the frequency to a preset high-frequency frequency, and output the corresponding high-frequency signal. The frequency division filter circuit has its input terminal connected to the output terminal of the phase-locked loop circuit. It is used to divide the high-frequency signal to a preset target fixed frequency signal using multi-level frequency division technology, and to filter the signal after each frequency division process. The output amplifier module, connected to the frequency divider filter circuit, is used to adjust the power of the target fixed frequency signal and output the final reference signal.

2. The broadband external reference circuit system for radio frequency transceiver systems according to claim 1, characterized in that, The phase-locked loop circuit includes a phase detector, a loop filter, and a crystal oscillator, which are connected in sequence. The phase detector compares the square wave reference signal output by the logic converter with the feedback signal output by the crystal oscillator. If the frequency of the feedback signal is higher than the frequency of the square wave reference signal, the control voltage on the crystal oscillator is reduced; if the frequency of the feedback signal is lower than the frequency of the square wave reference signal, the control voltage on the crystal oscillator is increased until the frequency of the feedback signal matches the frequency of the square wave reference signal.

3. The broadband external reference circuit system for radio frequency transceiver systems according to claim 1, characterized in that, The frequency division and filtering circuit includes a first-stage frequency divider, a first-stage filter, a second-stage frequency divider, and a second-stage filter connected in sequence. The first-stage frequency divider and the second-stage frequency divider are used to divide the high-frequency signal to a preset target fixed frequency signal. The first-stage filter and the second-stage filter are used to filter the signal after the frequency division process.

4. The broadband external reference circuit system for radio frequency transceiver systems according to claim 1, characterized in that, The system also includes a control circuit module connected to the phase-locked loop circuit. The control circuit module receives the input reference frequency value, automatically calculates and adjusts the phase detection frequency and locking speed of the phase-locked loop circuit based on the reference frequency value, and reads the locking state of the phase-locked loop circuit.

5. The broadband external reference circuit system for radio frequency transceiver systems according to claim 1, characterized in that, The control circuit module is also used to calculate reference frequency configuration parameters, control the division number of the frequency divider in the phase-locked loop circuit, and calculate the reference input signal with a resolution accurate to 1Hz.

6. The broadband external reference circuit system for radio frequency transceiver systems according to claim 1, characterized in that, The system also includes a power supply circuit module, which is connected to the logic converter, phase-locked loop circuit, frequency divider filter circuit and output amplifier module respectively, and is used to convert the external input voltage into the voltage required by each device and to provide individual power supply for circuits of different frequency bands.

7. The broadband external reference circuit system for radio frequency transceiver systems according to claim 1, characterized in that, The radio frequency signal lines between the logic converter, the phase-locked loop circuit, the frequency divider filter circuit and the output amplifier module adopt a point-to-point straight connection structure, and grounding shielding holes are arranged on both sides of the radio frequency signal lines.

8. The broadband external reference circuit system for radio frequency transceiver systems according to claim 1, characterized in that, The frequency range of the reference input signal is 10MHz to 100MHz, the preset high frequency is 500MHz, and the frequency of the target fixed frequency signal is 10MHz.

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