Adjustable amplitude limiting filter chip based on collaborative fusion

Abstract

The invention relates to the technical field of microwave passive devices, and provides a collaborative fusion-based adjustable amplitude limiting filter chip, which comprises a main transmission line, and a first-stage amplitude limiting circuit, a quarter-wavelength microstrip line TL1, a second-stage adjustable amplitude limiting circuit, an open-circuit quarter-wavelength microstrip line TL3 and a lumped parallel resonator which are loaded on the main transmission line and are sequentially connected, and the second-stage adjustable amplitude limiting circuit is loaded with an adjustable bias voltage source VDC. According to the chip designed by the invention, a filtering function is fused in an amplitude limiting circuit, and an amplitude limiting level adjustable function is realized while stopband suppression and circuit area are optimized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of microwave passive devices, in particular to an adjustable limiting and filtering chip based on synergistic integration. BACKGROUND

[0002] In recent years, with the rapid development of radar and wireless communication technology, the function of the communication system is becoming more and more complex, and the number of radio frequency channels is becoming more and more large, so the multi-function, high performance and miniaturization of the device unit in the system are put forward more stringent requirements.

[0003] The limiter in the radio frequency front-end receiving link of the communication system is usually used to protect sensitive devices such as low-noise amplifiers from being damaged by high-power microwaves. The traditional limiter attenuates the high-power signal, but the harmonic small signal generated by the nonlinearity of the device will reduce the sensitivity of the system after entering the communication system, so the filter is usually placed at the back end to suppress the out-of-band interference noise. However, in the traditional receiving link, the limiter and the filter are directly cascaded before the low-noise amplifier using a 50-ohm transmission line. This simple cascading method will cause problems such as increased circuit size, deteriorated inter-stage impedance mismatch, and poor out-of-band suppression.

[0004] In addition, the received signal of the radar and communication system varies with the application scenario and target distance, while the threshold and limiting level of the existing limiter are usually fixed values. If different threshold limiters are selected by switches, it will cause problems such as increased overall volume, narrow adjustable threshold range, and large adjustable threshold step. For example, the Chinese invention patent application with the publication number CN114826179A, "A millimeter wave limiting filter chip based on synergistic integration", the limiting filter based on synergistic integration reduces the insertion loss and circuit area of the radio frequency front-end while maintaining high power capacity, and improves the integration and stability of the radio frequency front-end. Although the chip integrates filtering and limiting, it cannot realize the adjustable limiting level function. In advanced radio frequency systems that require dynamic adjustment of system gain or protection threshold, how to design a multifunctional radio frequency front-end chip that integrates adjustable filtering and programmable limiting protection is a current problem to be solved. SUMMARY

[0005] The technical problem to be solved by the present application is how to design a chip that integrates filtering function in the limiting circuit, and realizes adjustable limiting level function while optimizing the stopband suppression and circuit area.

[0006] The present application solves the above technical problems by the following technical means:

[0007] The application provides a tunable limiting filter chip based on synergic fusion, which comprises a main transmission line and a first-stage limiting circuit, a quarter-wavelength microstrip line TL1, a second-stage tunable limiting circuit, an open-circuit quarter-wavelength microstrip line TL3 and a lumped parallel resonator loaded on the main transmission line and connected in sequence.

[0008] Preferably, the main transmission line further comprises an input impedance matching inductor L1, an input end DC blocking capacitor C1 and an output end DC blocking capacitor C6; the input impedance matching inductor L1 and the input end DC blocking capacitor C1 are connected in series in sequence and located between the input end of the main transmission line and the first-stage limiting circuit; and the output end DC blocking capacitor C6 is located between the lumped parallel resonator and the output end of the main transmission line.

[0009] Preferably, the first-stage limiting circuit has an upper-lower symmetric structure; two diodes D1 are stacked in series to form a limiting unit; the upper limiting circuit is connected in parallel with two reverse-parallel limiting units and a spiral inductor L2, and is coupled to the main transmission line through a MIM capacitor C2; and the lower limiting circuit is connected in parallel with two reverse-parallel limiting units and a spiral inductor L3, and is coupled to the main transmission line through a MIM capacitor C3.

[0010] Preferably, the capacitances of the coupling capacitors C2 and C3 are different, so that two zero points can be generated in the first-stage limiting circuit; in a transient limiting state, the diodes D1 are equivalent to resistors, and the limiting units are equivalent to resistors, so that the impedance matching of the radio frequency input port is out of tune, thereby reflecting the input high-power microwave signal and achieving the limiting purpose.

[0011] Preferably, the second-stage tunable limiting circuit comprises a spiral inductor L4, a diode D2, a microstrip line TL2 and a bias voltage source VDC connected in series; and further comprises a bypass capacitor C4 loaded between the microstrip line TL2 and the bias voltage source VDC; in a steady-state filtering state, the diode D2 is equivalent to a capacitor, the high-impedance microstrip line TL2 is inductive, and the equivalent capacitor of the diode D2 and the equivalent inductor of the microstrip line TL2 form a series resonant circuit, thereby introducing a transmission zero point on the right side of the filtering passband; in a transient limiting state, the diode D2 is equivalent to a resistor, and the incident high-power microwave signal is reflected due to impedance mismatch, thereby realizing the limiting function.

[0012] Preferably, the voltage adjustment range of the tunable bias voltage source VDC is-2-0V, and the step is 0.5V; the positive electrode of the tunable bias voltage source VDC is connected with the anode of the diode D2, and the negative electrode is grounded; as the tunable bias voltage source VDC gradually increases from-2V to 0V, the equivalent on voltage of the diode D2 gradually increases, and the threshold level and the limiting level of the limiting circuit gradually increase; conversely, the limiting level can be adjusted.

[0013] Preferably, the bypass capacitor C4 is used to filter out the AC component in the output voltage of the adjustable bias voltage source VDC.

[0014] Preferably, the quarter-wavelength microstrip line TL1 is used as an inter-stage impedance transformer to realize impedance transformation to improve the isolation; the open-circuit quarter-wavelength microstrip line TL3 introduces a transmission zero point on each side of the passband; the electrical length at the frequency of the left-side zero point generated by the open-circuit quarter-wavelength microstrip line TL3 is a quarter of a wavelength, and the electrical length at the frequency of the right-side zero point generated by the open-circuit quarter-wavelength microstrip line TL3 is three quarters of a wavelength.

[0015] Preferably, the lumped parallel resonator is composed of a spiral inductor L5 and a MIM capacitor C5 in parallel, and introduces a transmission zero point at the resonant frequency of the lumped parallel resonator, which is located on the right side of the filter passband, and is used to improve the stopband suppression at high frequencies.

[0016] Preferably, the input DC blocking capacitor C1 and the output DC blocking capacitor C6 are respectively used to isolate the DC signals at the input end and the output end of the main input line; and the input impedance matching inductor L1 is used for input impedance matching.

[0017] The present application has the following advantages:

[0018] (1) The present application realizes the adjustable amplitude limiting function by introducing a bias voltage source VDC in the second adjustable amplitude limiting circuit, and only uses simple diodes and microstrip line structures. The design is novel, and is suitable for advanced radio frequency systems that need to dynamically adjust the system gain or protection threshold.

[0019] (2) The present application fuses the filter function into the amplitude limiting circuit through a synergistic fusion design method, eliminates the interconnection structure and impedance matching network between the traditional discrete filter and the amplitude limiter, and thus effectively reduces the circuit size.

[0020] (3) The open-circuit quarter-wavelength microstrip line introduced in the present application improves the out-of-band suppression. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 FIG. 1 is a circuit topology schematic diagram of the adjustable amplitude limiting filter of the embodiment of the present application;

[0022] Figure 2 FIG. 2 is a comparison schematic diagram of the synergistic fusion design principle of the adjustable amplitude limiting filter chip of the embodiment of the present application and the traditional cascade design;

[0023] Figure 3 FIG. 3 is an equivalent schematic diagram of the adjustable amplitude limiting filter chip of the embodiment of the present application in the steady-state filter state;

[0024] Figure 4 FIG. 4 is an S parameter comparison diagram of the adjustable amplitude limiting filter chip of the embodiment of the present application with / without the open-circuit λ / 4 microstrip line.

[0025] Figure 5 The S parameter comparison chart of the adjustable limiting amplitude filter chip with / without the lumped parallel resonator in the embodiment of the present application is shown in the figure;

[0026] Figure 6 The simulation result schematic diagram of the limiting amplitude level of the adjustable limiting amplitude filter chip under different bias voltage sources VDC in the embodiment of the present application is shown in the figure;

[0027] Figure 7 The simulation result schematic diagram of the S parameter of the adjustable limiting amplitude filter chip under different bias voltage sources VDC in the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0029] Embodiment 1

[0030] The embodiment provides an adjustable limiting amplitude filter chip based on cooperative fusion, and a circuit topological structure thereof is shown in the figure. Figure 1 The adjustable limiting amplitude filter chip based on cooperative fusion comprises a main transmission line and a first-stage limiting amplitude circuit, a quarter-wavelength microstrip line TL1, a second-stage adjustable limiting amplitude circuit, an open quarter-wavelength microstrip line TL3 and a lumped parallel resonator which are loaded on the main transmission line and connected in sequence. The second-stage adjustable limiting amplitude circuit is loaded with an adjustable bias voltage source VDC, so as to realize adjustable limiting amplitude level.

[0031] The main transmission line further comprises an input impedance matching inductor L1, an input end DC blocking capacitor C1 and an output end DC blocking capacitor C6. The input impedance matching inductor L1 and the input end DC blocking capacitor C1 are connected in sequence and located between the input end of the main transmission line and the first-stage limiting amplitude circuit. The output end DC blocking capacitor C6 is located between the lumped parallel resonator and the output end of the main transmission line. The input end DC blocking capacitor C1 and the output end DC blocking capacitor C6 are respectively used for blocking DC signals at the input end and the output end of the main input line. The input impedance matching inductor L1 is used for input end impedance matching.

[0032] The first-stage limiting circuit structure is symmetrical; two diodes D1 are stacked in series to form a limiting unit; the upper limiting circuit is connected in parallel with two reverse-parallel limiting units and a spiral inductor L2, and is coupled to the main transmission line through a MIM capacitor C2; the lower limiting circuit is connected in parallel with two reverse-parallel limiting units and a spiral inductor L3, and is coupled to the main transmission line through a MIM capacitor C3.

[0033] The coupling capacitances C2 and C3 have different capacitance values, and the first-stage limiting circuit can generate two zero points; in the transient limiting state, the diodes D1 are equivalent to resistors, and the limiting units are equivalent to resistors, so that the impedance matching of the radio frequency input port is out of tune, thereby reflecting the input high-power microwave signal, and achieving the limiting purpose.

[0034] The second-stage adjustable limiting circuit comprises a spiral inductor L4, a diode D2, a microstrip line TL2 and a bias voltage source VDC connected in series; and further comprises a bypass capacitor C4 loaded between the microstrip line TL2 and the bias voltage source VDC; in the steady-state filtering state, the diode D2 is equivalent to a capacitor, the high-impedance microstrip line TL2 is inductive, and the equivalent capacitor of the diode D2 and the equivalent inductor of the microstrip line TL2 form a series resonant circuit, thereby introducing a transmission zero point on the right side of the filtering passband; in the transient limiting state, the diode D2 is equivalent to a resistor, and the incident high-power microwave signal is reflected due to impedance mismatch, thereby realizing the limiting function.

[0035] The voltage adjustment range of the adjustable bias voltage source VDC is -2-0V, and the step is 0.5V; the positive electrode of the adjustable bias voltage source VDC is connected with the anode of the diode D2, and the negative electrode is grounded; as the adjustable bias voltage source VDC gradually increases from -2V to 0V, the equivalent on-voltage of the diode D2 gradually increases, and the limiting level and the limiting amplitude of the limiting circuit gradually increase; vice versa, thereby realizing the adjustable limiting amplitude function.

[0036] The bypass capacitor C4 is used for filtering the alternating component in the output voltage of the adjustable bias voltage source VDC.

[0037] The quarter-wavelength microstrip line TL1 is used as an inter-stage impedance transformer to realize impedance transformation and improve the isolation degree; the open quarter-wavelength microstrip line TL3 introduces a transmission zero point on each side of the passband; the electrical length at the frequency of the left-side zero point of the generated passband is one quarter of a wavelength, and the electrical length at the frequency of the right-side zero point of the generated passband is three quarters of a wavelength.

[0038] The lumped parallel resonator is composed of a spiral inductor L5 and a MIM capacitor C5 connected in parallel, and introduces a transmission zero point at the resonant frequency, which is located on the right side of the filtering passband, and is used for improving the stopband suppression at high frequencies.

[0039] AsFigure 2 As shown, the conventional design method of the amplitude limiting filter is to cascade the amplitude limiter and the filter directly by using a 50-ohm transmission line, and does not have the adjustable amplitude limiting level function. The collaborative fusion design method proposed in the embodiment is to fuse the filtering function into the amplitude limiting circuit, eliminates the interconnection structure and impedance matching network between the traditional separate filter and the amplitude limiter, thereby effectively reducing the circuit size, and in addition, the second-stage adjustable amplitude limiting circuit realizes the adjustable amplitude limiting level function.

[0040] Specifically, the principle of the embodiment for realizing filtering and adjustable amplitude limiting is as follows:

[0041] In the transient amplitude limiting state, the impedance of the first-stage and second-stage amplitude limiting circuits is mismatched, so that the incident high-power microwave signal is reflected, and the amplitude limiting level changes with the change of the output voltage of the adjustable voltage source; in the steady-state filtering state, the first-stage amplitude limiting circuit provides a filtering passband and first and second transmission zeros, the open-circuit quarter-wavelength (λ / 4) microstrip line introduces third and fourth zeros, the lumped parallel resonator generates a fifth zero, and the second-stage amplitude limiting circuit introduces a sixth zero.

[0042] As shown in Figure 3 , the diodes in the amplitude limiting unit are in the cutoff state in the steady-state filtering, at which time they are equivalent to capacitors, the equivalent capacitance of the diode D1 is C D1 , and the equivalent capacitance of the diode D2 is C D2 . In the first-stage amplitude limiting circuit, the total equivalent capacitance of the amplitude limiting unit and the spiral inductance form a parallel resonant circuit, generating a filtering passband, and the total equivalent capacitance of the amplitude limiting unit, the spiral inductance and the coupling capacitance form a series resonant circuit, introducing a transmission zero. Since the coupling capacitances C2 and C3 have different capacitance values, the first-stage amplitude limiting circuit can generate two transmission zeros. In the second-stage amplitude limiting circuit, the high-impedance microstrip line TL2 is inductive, and the equivalent capacitance C D2 and the equivalent inductance of the microstrip line TL2 form a series resonant circuit, introducing a transmission zero on the right side of the filtering passband.

[0043] As shown in Figure 4 , the S parameter comparison chart of the adjustable amplitude limiting filter chip based on the collaborative fusion with / without the open-circuit λ / 4 microstrip line TL3; the S parameter (Scattering Parameters) is used to describe how a radio frequency network reflects and transmits energy when it is excited by an incident wave, and is the core index for describing its performance. As shown in the figure, the two transmission zeros introduced by the open-circuit λ / 4 microstrip line TL3 can effectively control the passband in the Ku band (i.e., 12-18 GHz), and improve the out-of-band suppression.

[0044] As shown in Figure 5As shown in the figure, the S parameter comparison chart of the tunable limiting amplitude filter chip based on synergistic integration with / without lumped parallel resonator; the figure shows that the transmission zero introduced by the lumped parallel resonator can significantly optimize the stopband suppression performance at high frequencies.

[0045] As shown in the figure, the simulation results of the limiting amplitude level of the tunable limiting amplitude filter chip based on synergistic integration under different bias voltage sources VDC; the figure shows that the limiting amplitude level changes with the change of the bias voltage VDC, indicating that the tunable limiting amplitude filter chip of the embodiment has the function of adjustable limiting amplitude level. Figure 6

[0046] As shown in the figure, the simulation results of the S parameter of the tunable limiting amplitude filter chip based on synergistic integration under different bias voltage sources VDC; the figure shows that the S21 parameter shows good stopband suppression performance under different voltages, and the S11 parameter shows good impedance matching of the chip. Figure 7

[0047] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.​​

Claims

1. A tunable amplitude limiting filter chip based on synergistic fusion, characterized in that, The application relates to a high-power microwave transient limiter, which comprises a main transmission line and a first-stage limiting circuit, a quarter-wavelength microstrip line TL1, a second-stage adjustable limiting circuit, an open quarter-wavelength microstrip line TL3 and a lumped parallel resonator loaded on the main transmission line and connected in sequence.

2. The tunable amplitude limiting filter chip based on synergistic fusion according to claim 1, characterized in that, The main transmission line further comprises an input impedance matching inductor L1, an input end DC blocking capacitor C1 and an output end DC blocking capacitor C6; the input impedance matching inductor L1 and the input end DC blocking capacitor C1 are connected in series and located between the input end of the main transmission line and the first-stage limiting circuit; and the output end DC blocking capacitor C6 is located between the lumped parallel resonator and the output end of the main transmission line.

3. The tunable amplitude limiting filter chip based on synergistic fusion according to claim 1, characterized in that, The first-stage limiting circuit is symmetrically arranged in an upper and lower structure; two diodes D1 are connected in series to form a limiting unit; the upper limiting circuit is connected in parallel with two reverse-parallel limiting units and a spiral inductor L2, and is coupled to the main transmission line through a MIM capacitor C2; and the lower limiting circuit is connected in parallel with two reverse-parallel limiting units and a spiral inductor L3, and is coupled to the main transmission line through a MIM capacitor C3.

4. The tunable amplitude limiting filter chip based on synergistic fusion according to claim 3, characterized in that, The capacitances of the coupling capacitors C2 and C3 are different, and two zero points can be generated in the first-stage limiting circuit; in a transient limiting state, the diodes D1 are equivalent to resistors, and the limiting units are equivalent to resistors, so that the impedance matching of the radio frequency input port is out of tune, thereby the input high-power microwave signal is reflected, and the limiting purpose is achieved.

5. The tunable amplitude limiting filter chip based on synergistic fusion of claim 1, wherein, The second-stage adjustable limiting circuit comprises a spiral inductor L4, a diode D2, a microstrip line TL2 and a bias voltage source VDC connected in series; and a bypass capacitor C4 is loaded between the microstrip line TL2 and the bias voltage source VDC; in a steady-state filtering state, the diode D2 is equivalent to a capacitor, the high-impedance microstrip line TL2 is inductive, the equivalent capacitor of the diode D2 and the equivalent inductor of the microstrip line TL2 form a series resonant circuit, and a transmission zero point is introduced on the right side of the filtering passband; in a transient limiting state, the diode D2 is equivalent to a resistor, and the incident high-power microwave signal is reflected due to impedance mismatch, thereby the limiting function is realized.

6. The tunable amplitude limiting filter chip based on synergistic fusion according to claim 5, characterized in that, The voltage adjustment range of the adjustable bias voltage source VDC is-2-0V, and the step is 0.5V; the positive electrode of the adjustable bias voltage source VDC is connected with the anode of the diode D2, and the negative electrode is grounded; with the gradual increase of the adjustable bias voltage source VDC from-2V to 0V, the equivalent conduction voltage of the diode D2 gradually increases, and the limiting level and the limiting level of the limiting circuit gradually increase; conversely, the limiting level is adjustable.

7. The tunable amplitude limiting filter chip based on synergistic fusion of claim 5, wherein, The bypass capacitor C4 is used for filtering the alternating component in the output voltage of the adjustable bias voltage source VDC.

8. The tunable amplitude limiting filter chip based on synergistic fusion of claim 1, wherein, The quarter-wavelength microstrip line TL1 is used as an inter-stage impedance transformer to realize impedance transformation and improve the isolation degree; the open quarter-wavelength microstrip line TL3 introduces a transmission zero point on each side of the passband; the electric length at the zero point frequency on the left side of the passband generated by the open quarter-wavelength microstrip line TL3 is one quarter of a wavelength, and the electric length at the zero point frequency on the right side of the passband generated by the open quarter-wavelength microstrip line TL3 is three quarters of a wavelength.

9. The tunable amplitude limiting filter chip based on synergistic fusion of claim 1, wherein, The parallel resonant tank is composed of a spiral inductor L5 and a MIM capacitor C5 in parallel, and a transmission zero point is introduced at the resonant frequency of the parallel resonant tank, which is located on the right side of the filter passband, and is used for improving the stopband rejection at high frequencies.

10. The tunable amplitude limiting filter chip based on synergistic fusion of claim 2, wherein, The input DC blocking capacitor C1 and the output DC blocking capacitor C6 are respectively used for isolating the DC signals of the input end and the output end of the main input line; and the input impedance matching inductor L1 is used for input impedance matching.

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