LC resonance circuit for improving spurious suppression of phase-locked source and phase-locked loop circuit

Abstract

The invention provides an LC resonant circuit for improving spurious suppression of a phase-locked source, and belongs to the technical field of airborne radio frequency, the circuit comprises a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a resistor R1, a diode N1 and an inductor L1, the capacitor C1, the capacitor C2 and the inductor L1 are connected in parallel to form a resonant sub-circuit, the capacitor C3 and the capacitor C4 are connected to two ends of the resonant sub-circuit and are respectively grounded in parallel, and the resistor R1, the diode N1 and the inductor L1 are grounded in parallel. The resistor R1 and the capacitor C3 are connected in series with the harmonic oscillator circuit, and the diode N1 is connected in parallel to the ground between the capacitor C2 and the capacitor C3. According to the circuit, the notch depth of the LC resonance circuit is increased, phase discrimination leakage is optimized, and signal spurious suppression is improved; the phase-locked loop circuit is suitable for most phase-locked loop circuits, wide in application scene, high in universality, simple in structure and obvious in signal spurious suppression effect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of airborne radio frequency, and particularly relates to an LC resonant circuit for improving spurious suppression of a phase-locked source and a phase-locked loop circuit. BACKGROUND

[0002] Frequency source is an important component of modern electronic system, and is widely used in communication, radar, electronic countermeasure, navigation, telemetry and remote control, and the functions of a large number of electronic devices and systems are directly dependent on the performance of the frequency source. With the continuous development of electronic technology, various electronic systems have higher and higher requirements for frequency source, and higher requirements are put forward for phase noise, spurious suppression, frequency resolution, relative operating bandwidth and frequency conversion time. In a radar system, a signal generated by a phase-locked loop is usually used as a reference source signal, and in order to suppress the phase discrimination leakage of the phase-locked loop signal, an LC resonant circuit as shown in the formula Figure 2 can be connected in series between the loop filter and the voltage-controlled oscillator, so as to effectively suppress the phase discrimination leakage.

[0003] In a strong interference radar system, the electromagnetic environment is severe, and there are many interferences. These interferences can be conducted into the phase-locked loop circuit through power signals and control signals, and can also interfere with the phase-locked loop circuit through space electromagnetic coupling. The LC resonant circuit commonly used has the disadvantages of insufficient notch depth, large phase discrimination leakage and poor electromagnetic shielding of the winding inductance, resulting in the problems of more near-end spurs of the local oscillator signal and poor suppression during the operation of the phase-locked loop. SUMMARY

[0004] In order to solve the above problems, the present application provides an LC resonant circuit for improving spurious suppression of a phase-locked source.

[0005] In order to achieve the above purpose, the present application provides the following technical scheme, an LC resonant circuit for improving spurious suppression of a phase-locked source, the circuit comprising a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a resistor R1, a diode N1 and an inductor L1, wherein the capacitor C1, the capacitor C2 and the inductor L1 are connected in parallel to form a resonant sub-circuit, the capacitor C3 and the capacitor C4 are connected across the resonant sub-circuit and are respectively connected in parallel to ground, the resistor R1 and the capacitor C3 are connected in series with the resonant sub-circuit, and the diode N1 is connected in parallel between the capacitor C2 and the capacitor C3 and to ground.

[0006] The LC resonant circuit for improving spurious suppression of a phase-locked source provided by the present application also has the following technical features, the inductor L1 is a ferrite laminated chip inductor.

[0007] The LC resonant circuit for improving spurious suppression of a phase-locked source provided by the present application also has the following technical features, the values of the inductor L1, the capacitor C1 and the capacitor C2 are obtained according to the resonant circuit,

[0008] Wherein, f is the trap frequency of LC resonant circuit, L is the inductance of inductor L1, C is the capacitance of capacitor C1 and C2.

[0009] The LC resonant circuit for improving the spurious suppression of a phase-locked source also has the technical features that the resistance R1 is connected between the loop filter and the voltage-controlled oscillator in the phase-locked loop circuit during use, the resistance value of the resistance R1 is consistent with the impedance of the microstrip line in the phase-locked loop circuit, and the resistance R1 is used to match the loop filter and the LC resonant circuit. The LC resonant circuit for improving the spurious suppression of a phase-locked source also has the technical features that the switching time of the diode N1 is less than 10 ns.

[0010] The LC resonant circuit for improving the spurious suppression of a phase-locked source also has the technical features that the resistance R1 and the capacitors C3 and C4 form an RC resonant circuit, the capacitances of the capacitors C3 and C4 are the same, and the capacitances are obtained according to the following formula, f1=1 / (2*π*R*C), Wherein, R is the resistance value of R1, and f1 is the cutoff frequency of the loop filter.

[0011] Another object of the present application is to provide a phase-locked loop circuit, which comprises the LC resonant circuit for improving the spurious suppression of a phase-locked source as described in any one of the preceding embodiments, and the LC resonant circuit for improving the spurious suppression of a phase-locked source is connected between the loop filter and the voltage-controlled oscillator.

[0012] Advantages The LC resonant circuit for improving the spurious suppression of a phase-locked source provided by the present application increases the trap depth of the LC resonant circuit, optimizes the phase discrimination leakage, improves the signal spurious suppression, is suitable for most phase-locked loop circuits, has a wide application scenario, has strong universality, has a simple structure, and has obvious signal spurious suppression effect.

[0013] The capacitance and inductance in the LC resonant circuit for improving the spurious suppression of a phase-locked source provided by the present application are easy to calculate, the filtering effect can be directly simulated by using ADS software, the parameters can be designed in advance, and the debugging time is reduced; the inductor L1 uses a ferrite laminated chip inductor instead of a wound inductor, electromagnetic shielding is enhanced, the near-end spurious suppression of the phase-locked loop signal is improved in a strong interference radar system.

[0014] The LC resonant circuit for improving the spurious suppression of a phase-locked source provided by the present application can effectively broaden the loop bandwidth under the premise of meeting the phase discrimination leakage index, improve the stability of the phase-locked loop circuit, and reduce the locking time of the phase-locked loop signal. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the present disclosure, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0016] Figure 1 The phase-locked loop circuit model provided by the embodiments of the present application; Figure 2 The LC resonant circuit provided in the prior art; Figure 3 The LC resonant circuit for improving the phase-locked loop source stray suppression provided by the embodiments of the present application; Figure 4 The phase-locked loop signal spectrum diagram when using a wire-wound inductor under strong interference conditions; Figure 5 The phase-locked loop signal spectrum diagram when using a ferrite laminated chip inductor under strong interference conditions. DETAILED DESCRIPTION

[0017] The present application will be further described in detail below in combination with the drawings and embodiments. It should be noted that these embodiments are not a limitation on the present application, and equivalent transformations or substitutions of functions, methods, or structures made by those skilled in the art based on these embodiments are within the protection scope of the present application.

[0018] In the description of the embodiments of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0019] In addition, the terms "first", "second", "third", and the like are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second", and the like can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0020] The terms "mounting", "connected", "connection" should be understood broadly, for example, can be fixed connection, can also be detachable connection, or integrally connected; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present invention can be understood according to the specific circumstances.

[0021] As shown in Figure 3 The embodiment of the present application provides an LC resonant circuit for improving the spurious suppression of a phase-locked source, which comprises a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a resistor R1, a diode N1 and an inductor L1, Among them, the capacitor C1, the capacitor C2 and the inductor L1 are connected in parallel to form a resonant sub-circuit, the capacitor C3 and the capacitor C4 are connected across the resonant sub-circuit and are respectively connected in parallel to the ground, the resistor R1 and the capacitor C3 are connected in series with the resonant sub-circuit, and the diode N1 is connected in parallel between the capacitor C2 and the capacitor C3 and to the ground.

[0022] In some embodiments, the inductor L1 is a ferrite laminated inductor.

[0023] In some embodiments, the values of the inductor L1, the capacitor C1 and the capacitor C2 are obtained according to the resonant circuit,

[0024] Among them, f is the notch frequency of the LC resonant circuit, L is the inductance of the inductor L1, and C is the sum of the capacitances of the capacitor C1 and the capacitor C2.

[0025] In some embodiments, the LC resonant circuit is connected between a loop filter and a voltage-controlled oscillator in a phase-locked loop circuit during use, the resistance value of the resistor R1 is consistent with the impedance of a microstrip line in the phase-locked loop circuit, and is used to match between the loop filter and the LC resonant circuit, In some embodiments, the switching time of the diode N1 is less than 10ns. Used to increase the loop stability.

[0026] In some embodiments, the resistor R1 and the capacitor C3 and the capacitor C4 form an RC resonant circuit, the capacitances of the capacitor C3 and the capacitor C4 are the same, and are obtained according to the following formula, f1=1 / (2*π*R*C), Among them, R is the resistance value of R1, and f1 is the cutoff frequency of the loop filter.

[0027] In some embodiments, a phase-locked loop circuit is provided, as shown in Figure 1As shown, the phase-locked loop circuit comprises the LC resonant circuit for improving the phase-locked source spurious suppression as claimed in any one of the preceding embodiments, which is connected between the loop filter and the voltage-controlled oscillator.

[0028] In some embodiments, there is provided a phase-locked loop circuit as Figure 1 As shown in the X-band phase-locked loop circuit, it comprises a phase detector 1, a loop filter 2, a voltage-controlled oscillator 3, a CPLD 4, a frequency divider 5, and an LC resonant circuit 6 connected between the loop filter 2 and the voltage-controlled oscillator 3. The phase detector 1 is HMC439QS16G of Hittite Company, the loop filter 2 is built by an operational amplifier AD797AR of Analog Company, and the VCO is HMC588LC4B of Hittite Company. The phase detector uses a 100MHz reference signal as the reference signal input, and the working mode uses the integer mode with a frequency step of 10MHz. In the LC resonant circuit 6, the inductance L1=5.6uH, the capacitance C1=39pF, C2=6.8pF, C3=680pF, C4=680pF, the resistance R1=47Ω, and the diode N1 is 1N4148H(G).

[0029] The original phase-locked loop circuit, the phase-locked loop signal phase detection leakage is -65dBc, and the near-end spurious on the radar whole machine is -35dBc, as shown in Figure 4 After adding the LC resonant circuit 6 of the present application, the phase-locked loop signal phase detection leakage is -75dBc, and the near-end spurious on the radar whole machine is -65dBc, as shown in Figure 5 .

[0030] The above only describes the preferred embodiments of the present application and should not be used to limit the present application. Any modification, equivalent replacement, and improvement within the spirit and principle of the present application should be included in the protection scope of the present application. The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled in the art, without departing from the technical principles of the present application, a number of improvements and variations can be made, which should be considered as the protection scope of the present application.

Claims

1. An LC resonant circuit for improving the spurious rejection of a phase-locked source, characterized in that, The circuit comprises capacitor C1, capacitor C2, capacitor C3, capacitor C4, resistor R1, diode N1 and inductor L1, Wherein, capacitor C1, capacitor C2 and inductor L1 are connected in parallel to form a resonant sub-circuit, capacitor C3 and capacitor C4 are connected across the resonant sub-circuit and are connected in parallel to ground, resistor R1 and capacitor C3 are connected in series with the resonant sub-circuit, and diode N1 is connected in parallel between capacitor C2 and C3 to ground.

2. The LC resonant circuit improving the spurious rejection of a phase-locked source according to claim 1, characterized in that, The inductor L1 is a ferrite laminated inductor.

3. The LC resonant circuit to improve the phase-locked source's spurious rejection of claim 1, wherein, The values of the inductor L1, capacitor C1 and capacitor C2 are obtained according to the resonant circuit, Wherein, f is the notch frequency of the LC resonant circuit, L is the inductance of inductor L1, and C is the sum of the capacitances of capacitor C1 and C2.

4. The LC resonant circuit to improve the phase-locked source's spurious rejection of claim 1, wherein, The LC resonant circuit is used in the process of connecting between the loop filter and the voltage-controlled oscillator in the phase-locked loop circuit, the resistance value of the resistor R1 is consistent with the impedance of the microstrip line in the phase-locked loop circuit, and the resistor R1 is used to match between the loop filter and the LC resonant circuit.

5. The LC resonant circuit to improve the phase-locked source's spurious rejection of claim 1, wherein, The switching time of the diode N1 is less than 10 ns.

6. The LC resonant circuit to improve the phase-locked source's spurious rejection of claim 1, wherein, The resistor R1 and the capacitors C3 and C4 form an RC resonant circuit, the capacitances of the capacitors C3 and C4 are the same, and the capacitances are obtained according to the following formula, f1=1 / (2*π*R*C), Wherein, R is the resistance value of R1, and f1 is the cutoff frequency of the loop filter.

7. A phase-locked loop circuit, characterized by comprising: The phase-locked loop circuit comprises the LC resonant circuit for improving the phase-locked source stray suppression according to any one of claims 1-6, and the LC resonant circuit for improving the phase-locked source stray suppression is connected between the loop filter and the voltage-controlled oscillator.

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