A millimeter-wave limiting filter chip based on collaborative fusion

Abstract

A millimeter wave limiting filter chip based on synergistic fusion belongs to the technical field of microwave passive devices, and solves the problems of low power capacity, high small signal insertion loss and large circuit size in the method of using a 50-ohm transmission line cascade limiter and filter in the prior art; the first-stage limiting circuit of the limiting filter in the technical solution of the present invention reflects high-power microwave signals in a transient limiting state, generates a filter passband and a transmission zero point on the left side of the filter passband in a steady-state filtering state, and a semi-lumped parallel resonator and a π-type structure respectively introduce a transmission zero point on both sides of the filter passband, thereby realizing a synergistic fusion design of the limiter and the filter; compared with the traditional method of using a 50-ohm transmission line cascade limiter and filter, the limiting filter based on synergistic fusion of the present invention reduces the insertion loss and circuit area of ​​the radio frequency front end while maintaining high power capacity, thereby improving the integration and stability of the radio frequency front end.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave passive devices and relates to a millimeter wave limiting filter chip based on collaborative fusion. Background Art

[0002] In recent years, with the rapid development of wireless communication technology, various wireless services and wireless communication products have also developed rapidly. A variety of high-density, high-integration and high-sensitivity device units are widely used in wireless communication systems, and the functions of the system are becoming more and more complex. In 5G or future wireless communication systems, the number of integrated RF transceivers will increase significantly compared with 4G systems. For example, as one of the four key wireless technologies of 5G, the massive multiple-input multiple-output (MIMO) system has dozens or hundreds of RF channels, which puts forward higher requirements on the multi-function, high-performance, miniaturization and stability of the device units in the system.

[0003] The RF front end is a key component of the wireless communication system, mainly including limiters, filters, low noise amplifiers, power amplifiers, switches, mixers and other devices. Among them, sensitive units such as low noise amplifiers are easily affected by interference noise and damaged by high-power microwaves. The filter placed at the front end is used to suppress out-of-band noise, and the limiter is used to reflect high-power incident energy to protect power-sensitive devices. In the traditional RF front-end receiving link, the limiter and filter are cascaded in front of the low noise amplifier using a 50-ohm transmission line. This simple cascade method results in a circuit size that is not compact enough and has low integration. In addition, the insertion loss of the limiter and filter will deteriorate the noise factor and gain of the RF front-end receiving channel, and the impedance matching when discrete devices are cascaded increases the design complexity.

[0004] The limiting filter is a multifunctional device with both limiting and filtering characteristics, which can eliminate the cascade structure between the traditional limiter and the filter. The working principle of the limiting filter is: when the input signal power is lower than the limiting threshold power, the limiting filter works in a steady-state filtering state to filter out useless signals and interference noise outside the band; when the input signal power is higher than the limiting threshold power, the limiting filter works in a transient limiting state. Based on the nonlinear limiting mechanism of microwave semiconductor diodes, a unique RF conductivity modulation effect will be generated under the action of high-power microwave signals. The equivalent impedance of the diode is controlled by the microwave power loaded on it, resulting in circuit impedance mismatch, thereby achieving effective attenuation of the input signal power.

[0005] At present, there are few studies on the design of limiting filters or the coordinated integration of limiters and filters. Among the proposed frequency selective limiters, most are based on loading discrete nonlinear limiting elements, such as Schottky diodes, PIN diodes, etc., on the resonator in the filter prototype to obtain the limiting function. However, Schottky diodes cannot withstand high power due to their thin depletion layer, low breakdown voltage and large reverse leakage current. Large-sized PIN diodes can withstand high power, but the corresponding large off-state capacitance makes it difficult for the device to operate in the millimeter wave frequency band; in addition, the parasitic effects of discrete devices seriously affect key performance such as power capacity and insertion loss; and the printed circuit board (PCB) process used cannot be miniaturized and integrated into the microwave circuit system, which does not meet the current trend of high performance, high density and high integration of RF front-end systems.

[0006] Therefore, in the design of limiters and filters, how to achieve effective collaborative fusion design, how to reduce insertion loss while ensuring high power capacity, how to miniaturize circuit size and improve integration are issues that need to be addressed urgently. Summary of the invention

[0007] The purpose of the present invention is to design a millimeter wave limiting filter chip based on synergistic fusion to solve the problems of low power capacity, high small signal insertion loss and large circuit size in the method of using 50 ohm transmission line cascade limiter and filter in the prior art.

[0008] The present invention solves the above technical problems through the following technical solutions:

[0009] A millimeter wave limiting filter chip based on collaborative fusion comprises: a first-stage limiting circuit (11) attached to a microwave dielectric substrate (10), a second-stage limiting circuit (12), an input end main transmission line (13), a quarter-wavelength transmission line (14), a semi-lumped parallel resonator (15), an output DC isolation capacitor (16), an output end transmission line (17), and a π-type structure (18);

[0010] The input end main transmission line (13), the quarter-wavelength transmission line (14), the semi-lumped parallel resonator (15), the output DC blocking capacitor (16), and the output end transmission line (17) are connected end to end in sequence to form a transmission channel for radio frequency signals; the first stage limiting circuit (11), the second stage limiting circuit (12), and the π-shaped structure (18) are all loaded on the transmission channel;

[0011] When the limiting filter is in a transient limiting state, the first-stage limiting circuit (11) and the second-stage limiting circuit (12) are used to reflect high-power incident signals and reduce the limiting output level; when the limiting filter is in a steady-state filtering state, the first-stage limiting circuit (11) is used to generate a filtering passband and a first transmission zero point on the left side of the filtering passband; the quarter-wavelength transmission line (14) located between the first-stage limiting circuit (11) and the second-stage limiting circuit (12) is used as an inter-stage impedance transformer to achieve impedance transformation to improve limiting isolation; the semi-lumped parallel resonator (15) is used to generate a transmission zero point on the right side of the filtering passband to improve the rectangular coefficient on the right side of the filtering passband; the π-type structure (18) is used to generate a second transmission zero point on the left side of the filtering passband to improve the rectangular coefficient on the left side of the passband and achieve wide stopband suppression at low frequencies.

[0012] The first-stage limiting circuit (11) of the limiting filter in the technical solution of the present invention reflects high-power microwave signals in a transient limiting state, generates a filter passband and a transmission zero on the left side of the filter passband in a steady-state filtering state, and the semi-lumped parallel resonator (15) and the π-type structure (18) introduce a transmission zero on both sides of the filter passband, respectively, thereby realizing a synergistic fusion design of the limiter and the filter. Compared with the traditional method of using a 50-ohm transmission line to cascade a limiter and a filter, the limiting filter based on synergistic fusion of the present invention reduces the insertion loss and circuit area of ​​the RF front end while maintaining a high power capacity, thereby improving the integration and stability of the RF front end.

[0013] Furthermore, the first-stage limiting circuit (11) comprises: two limiting units and two first MIM capacitors (113), each limiting unit is symmetrically loaded on the input end main transmission line (13) in the form of reverse parallel connection through one first MIM capacitor (113), and the specific connection relationship is as follows: each limiting unit comprises: two groups of PIN diode series branches (111), one short-circuit transmission line (112), each group of PIN diode series branches (111) is composed of three PIN diodes stacked in series; the first group of PIN diode series in each limiting unit The anode of the connecting branch (111) is grounded, the cathode of the first group of PIN diode series-connected branches (111) is connected to one end of the first MIM capacitor (113), the cathode of the second group of PIN diode series-connected branches (111) is grounded, the anode of the second group of PIN diode series-connected branches (111) is connected to one end of the first MIM capacitor (113), one end of the short-circuit transmission line (112) is grounded, the other end of the short-circuit transmission line (112) is connected to one end of the first MIM capacitor (113), and the other end of the first MIM capacitor (113) is connected to the input end main transmission line (13).

[0014] Furthermore, the second-stage limiting circuit (12) comprises: two PIN diode single tubes (121), the two PIN diode single tubes (121) are symmetrically loaded on the input end main transmission line (13) in the form of reverse parallel connection, and the specific connection relationship is as follows: the anode of the first PIN diode single tube (121) is grounded, and the cathode of the first PIN diode single tube (121) is connected to the quarter-wavelength transmission line (14), and the cathode of the second PIN diode single tube (121) is grounded, and the anode of the second PIN diode single tube (121) is connected to the output end of the quarter-wavelength transmission line (14).

[0015] Furthermore, the input end main transmission line (13) is a rectangular microstrip line, one end of the input end main transmission line (13) is loaded with a radio frequency incident signal, and the other end of the input end main transmission line (13) is connected to a common connection point of two limiting units of the first-stage limiting circuit (11); the output end transmission line (17) is a section of a gradient microstrip line, one end of the output end transmission line (17) is connected to an output DC blocking capacitor (16), and the other end of the output end transmission line (17) serves as an output end of the radio frequency signal.

[0016] Furthermore, the quarter-wavelength transmission line (14) is a segment of a gradient microstrip line, one end of the quarter-wavelength transmission line (14) is connected to a common connection point of two limiting units of the first-stage limiting circuit (11), and the other end of the quarter-wavelength transmission line (14) is connected to a common connection point of two PIN diodes (121).

[0017] Furthermore, the semi-lumped parallel resonator (15) comprises: a U-shaped bending transmission line (151) and a second MIM capacitor (152); the U-shaped bending transmission line (151) has an electrical length less than a 45° transmission line; the input end of the U-shaped bending transmission line (151) is connected to a common connection point of two PIN diodes (121); the output end of the U-shaped bending transmission line (151) is connected to an output DC isolation capacitor (16); and the two ends of the second MIM capacitor (152) are bridged between the input end and the output end of the U-shaped bending transmission line (151).

[0018] Furthermore, the π-type structure (18) comprises: a section of bent microstrip line (181) and two third MIM capacitors (182); the bent microstrip line (181) is a transmission line with an electrical length less than 90°; one end of the bent microstrip line (181) is connected to one end of a first third MIM capacitor (182), and the other end of the first third MIM capacitor (182) is connected to a grounding through hole (21); the other end of the bent microstrip line (181) is connected to one end of a second third MIM capacitor (182), and the other end of the second third MIM capacitor (182) is connected to a grounding through hole (21); wherein a common connection point between the bent microstrip line (181) and the first third MIM capacitor (182) is connected to the input end of the U-shaped bent transmission line (151).

[0019] Furthermore, the calculation formulas for the center frequency of the filtering passband of the limiting filter and the first transmission zero point on the left side of the filtering passband are respectively:

[0020]

[0021]

[0022] Where f0 is the center frequency of the filter passband, f TZ1 is the first transmission zero point on the left side of the filter passband, L1 is the equivalent inductance of the short-circuited transmission line (112), Z1 is the characteristic impedance of the short-circuited transmission line (112), θ1 is the electrical length of the short-circuited transmission line (112), C D is the total off-state capacitance value of the PIN diode in each limiting unit in the first-stage limiting circuit (11), and C1 is the capacitance value of the first MIM capacitor (113).

[0023] Furthermore, the calculation formula of a transmission zero point on the right side of the filtering passband is:

[0024]

[0025] Among them, f TZ2 is a transmission zero point on the right side of the filter passband, L2 is the equivalent inductance of the U-shaped bending transmission line (151), Z2 is the characteristic impedance of the U-shaped bending transmission line (151), θ2 is the electrical length of the U-shaped bending transmission line (151), and C2 is the capacitance value of the second MIM capacitor (152).

[0026] Furthermore, the calculation formula of the second transmission zero point on the left side of the filter passband is:

[0027]

[0028] Where C is the speed of light in free space, ε ris the relative dielectric constant of the microwave dielectric substrate (10), and l0 is the physical length of the quarter-wavelength transmission line (14).

[0029] The advantages of the present invention are:

[0030] (1) The first-stage limiting circuit (11) of the limiting filter in the technical solution of the present invention reflects high-power microwave signals in a transient limiting state, generates a filter passband and a transmission zero on the left side of the filter passband in a steady-state filtering state, and the semi-lumped parallel resonator (15) and the π-type structure (18) introduce a transmission zero on both sides of the filter passband, respectively, thereby realizing a synergistic fusion design of the limiter and the filter. Compared with the conventional method of using a 50-ohm transmission line to cascade a limiter and a filter, the limiting filter based on synergistic fusion of the present invention reduces the insertion loss and circuit area of ​​the RF front end while maintaining a high power capacity, thereby improving the integration and stability of the RF front end.

[0031] (2) In the technical solution of the present invention, each group of PIN diode series branches (111) of each limiting unit in the first-stage limiting circuit (11) are stacked in series, thereby increasing the breakdown voltage and improving the steady-state power capacity of the limiting circuit; two groups of PIN diode series branches (111) in the same limiting unit are connected in reverse parallel to reduce the on-resistance, increase the reflected power, and improve the transient power capacity of the limiting circuit; the total off-state capacitance of the PIN diode in the first-stage limiting circuit (11) and the equivalent inductance of the short-circuit transmission line (112) form a parallel resonant circuit and are coupled to the input end main transmission line (13) through the first MIM capacitor (113), providing a filtering passband and a transmission zero point on the left side of the filtering passband for the limiting filter, wherein the total off-state capacitance of the PIN diode is integrated into the parallel resonance to reduce the insertion loss, and the short-circuit transmission line is used to replace the traditional large-size, low-Q lumped spiral inductor. , which can further reduce the insertion loss and the circuit size; the semi-lumped parallel resonant circuit is used to introduce a transmission zero point on the right side of the passband to achieve a high rectangular coefficient on the right side of the passband. Compared with the traditional lumped parallel resonant circuit using spiral inductors, the semi-lumped topology loaded with the transmission line can reduce the insertion loss and the circuit area; the π-type structure (18) connected in parallel to the main transmission line (13) at the main input end is equivalent to an open-circuited quarter-wavelength transmission line, and a second transmission zero point is introduced on the left side of the limiting filter passband to improve the frequency selectivity and achieve low-frequency wide stopband suppression. Compared with the traditional quarter-wavelength transmission line, the π-type structure composed of two third MIM capacitors (182) and a bent microstrip line (181) with an electrical length less than 90 degrees can effectively shorten the electrical length of the transmission line, that is, shorten the corresponding physical length of the transmission line, reduce the chip area, and meet the current trend of miniaturization and high integration of RF front-ends.

[0032] (3) The chip size is reduced by using a π-type structure (18) to replace the traditional quarter-wavelength transmission line and using a transmission line with an electrical length less than 45° to replace the lumped spiral inductor in the semi-lumped parallel resonator (15). BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A three-dimensional structural diagram of a millimeter-wave limiting filter chip based on collaborative fusion according to an embodiment of the present invention;

[0034] Figure 2 It is a schematic diagram of an equivalent circuit of a millimeter-wave limiting filter chip based on collaborative fusion according to an embodiment of the present invention;

[0035] Figure 3 A block diagram of the collaborative fusion design principle of a millimeter wave limiting filter chip based on collaborative fusion according to an embodiment of the present invention;

[0036] Figure 4 An equivalent model diagram of a lumped parallel resonant circuit and a semi-lumped parallel resonator according to an embodiment of the present invention;

[0037] Figure 5 A conventional quarter-wavelength transmission line and an equivalent π-type structure model diagram of an embodiment of the present invention;

[0038] Figure 6 : is a small signal circuit equivalent flow chart of the first stage limiting circuit of the millimeter wave limiting filter chip based on collaborative fusion according to an embodiment of the present invention;

[0039] Figure 7 A diagram showing the comparison of power capacity results of the first-stage limiting circuit with different numbers of PIN diode series branches of the millimeter-wave limiting filter chip based on collaborative fusion according to an embodiment of the present invention;

[0040] Figure 8 A diagram showing the comparison of insertion loss results of the first-stage limiting circuit with different total off-capacitors of the millimeter-wave limiting filter chip based on collaborative fusion according to an embodiment of the present invention;

[0041] Fig. 9 This is a diagram showing the comparison of insertion loss results of first-stage limiting circuits with different structures of a millimeter-wave limiting filter chip based on collaborative fusion according to an embodiment of the present invention;

[0042] Fig.10 A schematic diagram of the effect of the transmission zero introduced by the first-stage limiting circuit of the millimeter-wave limiting filter chip based on collaborative fusion on the filtering performance of the limiting filter in an embodiment of the present invention;

[0043] Fig.11A schematic diagram of the effect of the transmission zero introduced by the semi-lumped parallel resonator of the millimeter-wave limiting filter chip based on collaborative fusion on the filtering performance of the limiting filter according to an embodiment of the present invention;

[0044] Fig.12 A schematic diagram of the effect of the zero point introduced by the π-type structure of the millimeter-wave limiting filter chip based on collaborative fusion on the filtering performance of the limiting filter in an embodiment of the present invention;

[0045] Fig.13 A comparison diagram showing the results of S parameters when the millimeter wave limiting filter chip based on collaborative fusion according to an embodiment of the present invention has three transmission zero points and has no transmission zero point;

[0046] Fig.14 This is a graph showing the output power and limiting isolation results of the millimeter-wave limiting filter chip based on collaborative fusion in an embodiment of the present invention. DETAILED DESCRIPTION

[0047] To make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments:

[0049] Embodiment 1

[0050] 1. Structure of the millimeter wave limiting filter chip based on collaborative fusion of the present invention

[0051] like Figure 1 and Figure 2 As shown, a millimeter-wave limiting filter chip based on collaborative fusion includes: a first-stage limiting circuit 11 attached to a microwave dielectric substrate 10, a second-stage limiting circuit 12, an input main transmission line 13, a quarter-wavelength transmission line 14, a semi-lumped parallel resonator 15, an output DC blocking capacitor 16, an output transmission line 17, a π-type structure 18, 6 pads 20 and 14 grounding through holes 21 opened on the microwave dielectric substrate 10.

[0052] The first stage limiting circuit 11 includes: 2 limiting units and 2 first MIM capacitors 113, each limiting unit is symmetrically loaded on the input end main transmission line 13 in the form of reverse parallel connection through a first MIM capacitor 113, and the specific connection relationship is as follows:

[0053] Each limiting unit includes: 2 groups of PIN diode series branches 111 and 1 short-circuit transmission line 112, and each group of PIN diode series branches 111 is composed of 3 PIN diodes stacked in series; the anode of the first group of PIN diode series branches 111 in each limiting unit is connected to the ground through hole 21, and the cathode of the first group of PIN diode series branches 111 is connected to one end of the first MIM capacitor 113, the cathode of the second group of PIN diode series branches 111 is connected to the ground through hole 21, and the anode of the second group of PIN diode series branches 111 is connected to one end of the first MIM capacitor 113, one end of the short-circuit transmission line 112 is connected to the ground through hole 21, and the other end of the short-circuit transmission line 112 is connected to one end of the first MIM capacitor 113, and the other end of the first MIM capacitor 113 is connected to the input main transmission line 13.

[0054] The second-stage limiting circuit 12 includes: two PIN diode single tubes 121, which are symmetrically loaded on the input end main transmission line 13 in the form of reverse parallel connection, and the specific connection relationship is as follows: the anode of the first PIN diode single tube 121 is connected to the ground through hole 21, the cathode of the first PIN diode single tube 121 is connected to the quarter-wavelength transmission line 14, the cathode of the second PIN diode single tube 121 is connected to the ground through hole 21, and the anode of the second PIN diode single tube 121 is connected to the output end of the quarter-wavelength transmission line 14.

[0055] The input end main transmission line 13 is a rectangular microstrip line, the input port and the output port of the chip are both in the GSG form, and the wafer-level GaAs PINAB process is adopted. The material of the microwave dielectric substrate 10 is GaAs, with a dielectric constant of 12.9, an insertion loss tangent of 0.001, and a thickness of 0.1 mm. A row of three pads 20 are arranged at one end of the microwave dielectric substrate 10, one end of the input end main transmission line 13 is connected to the middle pad 20 and loaded with a radio frequency incident signal, and the other two pads 20 are respectively connected to the ground through holes 21 and loaded with ground signals, and the other end of the input end main transmission line 13 is connected to the common connection point of the two limiting units of the first-stage limiting circuit 11.

[0056] The quarter-wavelength transmission line 14 is a segment of a gradient microstrip line, one end of which is connected to a common connection point of two limiting units of the first-stage limiting circuit 11, and the other end of which is connected to a common connection point of two PIN diodes 121.

[0057] The semi-lumped parallel resonator 15 includes: a U-shaped bend transmission line 151 and a second MIM capacitor 152. The U-shaped bend transmission line 151 has an electrical length less than 45°. The input end of the U-shaped bend transmission line 151 is connected to the common connection point of two PIN diode single tubes 121, and the output end of the U-shaped bend transmission line 151 is connected to the output DC isolation capacitor 16; the two ends of the second MIM capacitor 152 are bridged between the input end and the output end of the U-shaped bend transmission line 151.

[0058] The output transmission line 17 is a section of gradient microstrip line, one end of the output transmission line 17 is connected to the output DC blocking capacitor 16, and a row of three pads 20 are also arranged at the other end of the microwave dielectric substrate 10. The other end of the output transmission line 17 is connected to the middle pad 20 as the output end of the RF signal, and the other two pads 20 are respectively connected to the ground through holes 21 and loaded with ground signals.

[0059] The π-type structure 18 includes: a bent microstrip line 181 and two third MIM capacitors 182, wherein the bent microstrip line 181 is a transmission line with an electrical length less than 90°, one end of the bent microstrip line 181 is connected to one end of the first third MIM capacitor 182, and the other end of the first third MIM capacitor 182 is connected to the grounding through hole 21, the other end of the bent microstrip line 181 is connected to one end of the second third MIM capacitor 182, and the other end of the second third MIM capacitor 182 is connected to the grounding through hole 21, wherein the common connection point between the bent microstrip line 181 and the first third MIM capacitor 182 is connected to the input end of the U-shaped bent transmission line 151.

[0060] 2. Working principle of the millimeter wave limiting filter chip based on collaborative fusion proposed in the present invention

[0061] When the limiting filter is in a transient limiting state, the first-stage limiting circuit 11 and the second-stage limiting circuit 12 are used to reflect high-power incident signals and reduce the limiting output level;

[0062] When the limiting filter is in a steady-state filtering state, the first-stage limiting circuit 11 is used to generate a filter passband and a first transmission zero on the left side of the filter passband; the quarter-wavelength transmission line 14 located between the first-stage limiting circuit 11 and the second-stage limiting circuit 12 is used as an inter-stage impedance transformer to achieve impedance transformation to improve the limiting isolation; the semi-lumped parallel resonator 15 is used to generate a transmission zero on the right side of the filter passband to improve the rectangular coefficient on the right side of the filter passband; the π-type structure 18 is used to generate a second transmission zero on the left side of the filter passband to improve the rectangular coefficient on the left side of the passband and achieve wide stopband suppression at low frequencies.

[0063] like Figure 3As shown in FIG. 1 , it is a block diagram of the principle of cooperative fusion of the limiting filter proposed in the present invention. The principle of cooperative fusion is as follows: the first-stage limiting circuit 11 reflects high-power microwave signals in the transient limiting state, generates a filter passband and a transmission zero on the left side of the filter passband in the steady-state filtering state, and the semi-lumped parallel resonator 15 and the π-type structure 18 introduce a transmission zero on both sides of the filter passband, respectively, so as to realize the cooperative fusion of the limiter and the filter. The center frequency f0 of the filter passband of the limiting filter and the first transmission zero f on the left side of the filter passband TZ1 The calculation formulas are:

[0064]

[0065]

[0066] Wherein, L1 is the equivalent inductance of the short-circuited transmission line (112), Z1 is the characteristic impedance of the short-circuited transmission line (112), θ1 is the electrical length of the short-circuited transmission line (112), C D is the total off-state capacitance value of the PIN diode in each limiting unit in the first-stage limiting circuit (11), and C1 is the capacitance value of the first MIM capacitor (113).

[0067] like Figure 4 As shown, the semi-lumped parallel resonator (15) is used to generate a transmission zero point on the right side of the filter passband to increase the rectangular coefficient on the right side of the passband to improve the frequency selectivity of the limiting filter. In addition, a transmission line TL2 with an electrical length less than 45° is used to replace the spiral inductor L2 in the lumped parallel resonant circuit to form a semi-lumped resonator to reduce the circuit size. The introduced transmission zero point f TZ2 The calculation formula is:

[0068]

[0069] Wherein, L2 is the equivalent inductance of the U-shaped bending transmission line (151), Z2 is the characteristic impedance of the U-shaped bending transmission line (151), θ2 is the electrical length of the U-shaped bending transmission line (151), and C2 is the capacitance value of the second MIM capacitor (152).

[0070] like Figure 5 As shown, the quarter-wavelength transmission line (14) is used as an inter-stage impedance converter to achieve impedance transformation, so as to improve the limiting isolation; the π-type structure (18) is used to generate a second transmission zero point on the left side of the filter passband, so as to improve the rectangular coefficient on the left side of the passband and achieve wide stopband suppression at low frequencies; using the proposed π-type structure (18) to replace the traditional quarter-wavelength transmission line can significantly shorten the electrical length of the transmission line, and the physical length of the corresponding transmission line is effectively shortened, which can further reduce the chip area. The relevant parameter calculation formula is:

[0071]

[0072]

[0073]

[0074] Where C is the speed of light in free space, ε r is the relative dielectric constant of the microwave dielectric substrate (10), l0 is the physical length of the quarter-wavelength transmission line (14), Z4 is the characteristic impedance of the quarter-wavelength transmission line (14), θ3 is the electrical length of the bent microstrip line (181) in the π-type structure (18), Z3 is the characteristic impedance of the bent microstrip line (181) in the π-type structure (18), and C3 is the capacitance value of the third MIM capacitor (182) in the π-type structure (18).

[0075] 3. Performance analysis of the millimeter wave limiting filter chip based on collaborative fusion of the present invention

[0076] 3.1. Reduced insertion loss

[0077] like Figure 6 (a) with Figure 6 As shown in (b), the PIN diode D1 in the first stage limiting circuit (11) is equivalent to its corresponding off-state capacitance C when the signal is small. D1 , at this time, the insertion loss IL of the first stage limiting circuit (11) is calculated as:

[0078] IL=4.343Z0(2πfC off ') 2 R s (7)

[0079]

[0080] Wherein, Z0 is the characteristic impedance of the input end main transmission line (13), f is the operating frequency of the first stage limiting circuit (11), C off is the total off capacitance of the PIN diode of the first stage limiting circuit (11), R s is the parasitic resistance of the first stage limiting circuit (11), N S is the number of diodes stacked in series in each group of PIN diode series branches (111) of each limiting unit in the first stage limiting circuit (11), and Np is the number of PIN diode series branches (111) of each limiting unit in the first stage limiting circuit (11).

[0081] like Figure 6 As shown in (c), the total off-state capacitance C of the PIN diode in each limiting unit in the first stage limiting circuit 11D The equivalent inductance L1 of the short-circuited transmission line 112 in the limiting unit forms a parallel resonant circuit, and is coupled to the input main transmission line 13 through the first MIM capacitor 113, providing a filter passband for the limiting filter chip and introducing a transmission zero point on the left side of the filter passband. The total off-state capacitance C of the PIN diode in each limiting unit in the first stage limiting circuit 11 is D is incorporated into the parallel resonant circuit to reduce insertion loss; in addition, Figure 6 As shown in (d), the present invention utilizes a short-circuit transmission line 112 to replace a conventional large-sized, low-Q lumped spiral inductor, which can further reduce insertion loss.

[0082] 3.2. Improved steady-state power capacity of the limiting circuit

[0083] like Figure 6 As shown in (a), each PIN diode in the first-stage limiting circuit 11 will be subjected to a corresponding reverse bias voltage when in a steady state. Each group of PIN diode series branches 111 is composed of three PIN diodes stacked in series, which increases the breakdown voltage and thus increases the steady-state power capacity. The steady-state power capacity formula of the limiting circuit is:

[0084]

[0085] Among them, N S is the number of diodes stacked in series in each group of PIN diode series branches 111 of each limiting unit in the first stage limiting circuit 11, V BR is the breakdown voltage of each PIN diode.

[0086] 3.3. Improved transient power capacity of the limiting circuit

[0087] According to the principle of resistor parallel connection, resistor parallel connection can reduce the resistance value. In the first stage limiting circuit 11, two limiting units are connected in reverse parallel and symmetrically loaded on the input end main transmission line 13, and two groups of PIN diode series branches 111 in each limiting unit are connected in parallel. The on-resistance of the PIN diode is reduced by the resistor parallel connection, and the total on-resistance of the first stage limiting circuit 11 is reduced. The transient power capacity formula of the limiting circuit is:

[0088]

[0089] Among them, P DM is the maximum allowable power dissipation of the PIN diode, Ron is the on-resistance of the PIN diode, N Sis the number of diodes stacked in series in each group of PIN diode series branches 111 of each limiting unit in the first stage limiting circuit 11 , and Np is the number of PIN diode series branches 111 of each limiting unit in the first stage limiting circuit 11 .

[0090] 3.4. Reduce the output power of the limiting circuit

[0091] The multiple PIN diodes in the first-stage limiter circuit 101 are connected in series to increase the breakdown voltage and the total on-resistance, thereby increasing the output power. In addition, the threshold level is also increased accordingly. The second-stage limiter circuit 12 reduces the output power of the limiter circuit by reducing the on-resistance. The second-stage limiter circuit 12 adopts the reverse parallel structure of the PIN diode single tube 121 to reduce the on-resistance of the limiter circuit. The output power formula of the limiter circuit is:

[0092]

[0093] Among them, R' on is the total on-resistance of the second-stage limiting circuit 12, and Pin is the incident power of the second-stage limiting circuit 12, that is, the output power of the first-stage limiting circuit 11.

[0094] like Figure 7 and Figure 8 As shown, a comparison diagram of the power capacity and insertion loss results of the first-stage limiting circuit 11 with different numbers of PIN diode series branches based on the collaborative fusion millimeter-wave limiting filter chip is displayed; the figure shows that the first-stage limiting circuit 11 proposed in the present invention can further reduce the insertion loss while maintaining sufficient power capacity, thereby solving the trade-off problem between the insertion loss and power capacity of the limiter.

[0095] like Fig. 9 As shown, a comparison diagram of the insertion loss results of the first-stage limiting circuit 11 with different structures of the millimeter-wave limiting filter chip based on collaborative fusion is displayed. The figure shows that the design of the short-circuit transmission line 112 adopted in the present invention can further reduce the insertion loss compared with the design using spiral inductor and the traditional design.

[0096] like Figures 10 to 13 As shown, a comparative display of the filtering performance of the millimeter-wave limiting filter chip based on collaborative fusion by gradually introducing transmission zero points is shown. The figure shows that the present invention can effectively improve the frequency selection characteristics of the limiting filter by introducing zero points.

[0097] like Fig.14 As shown, the output power and limiting isolation results of the millimeter-wave limiting filter chip based on collaborative fusion are displayed, which shows that the limiting filter of the present invention has good limiting performance.

[0098] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A millimeter wave limiting filter chip based on collaborative fusion, characterized in that: include: A first-stage limiting circuit (11), a second-stage limiting circuit (12), an input-end main transmission line (13), a quarter-wavelength transmission line (14), a semi-lumped parallel resonator (15), an output DC-isolating capacitor (16), an output-end transmission line (17), and a π-shaped structure (18) attached to a microwave dielectric substrate (10); The input end main transmission line (13), the quarter-wavelength transmission line (14), the semi-lumped parallel resonator (15), the output DC blocking capacitor (16), and the output end transmission line (17) are connected end to end in sequence to form a transmission channel for radio frequency signals; the first stage limiting circuit (11), the second stage limiting circuit (12), and the π-shaped structure (18) are all loaded on the transmission channel; When the limiting filter is in a transient limiting state, the first-stage limiting circuit (11) and the second-stage limiting circuit (12) are used to reflect high-power incident signals and reduce the limiting output level; when the limiting filter is in a steady-state filtering state, the first-stage limiting circuit (11) is used to generate a filtering passband and a first transmission zero point on the left side of the filtering passband; the quarter-wavelength transmission line (14) located between the first-stage limiting circuit (11) and the second-stage limiting circuit (12) is used as an inter-stage impedance transformer to achieve impedance transformation to improve limiting isolation; the semi-lumped parallel resonator (15) is used to generate a transmission zero point on the right side of the filtering passband to improve the rectangular coefficient on the right side of the filtering passband; the π-type structure (18) is used to generate a second transmission zero point on the left side of the filtering passband to improve the rectangular coefficient on the left side of the passband and achieve wide stopband suppression at low frequencies.

2. The millimeter wave limiting filter chip based on collaborative fusion according to claim 1 is characterized in that: The first-stage amplitude limiting circuit (11) comprises: two amplitude limiting units and two first MIM capacitors (113), each of which is symmetrically loaded on the input end main transmission line (13) in the form of reverse parallel connection through one first MIM capacitor (113), and the specific connection relationship is as follows: each amplitude limiting unit comprises: two groups of PIN diode series branches (111) and one short-circuit transmission line (112), each group of PIN diode series branches (111) is composed of three PIN diodes stacked in series; the first group of PIN diode series branches in each amplitude limiting unit The anode of the first group of PIN diode series branches (111) is grounded, the cathode of the first group of PIN diode series branches (111) is connected to one end of the first MIM capacitor (113), the cathode of the second group of PIN diode series branches (111) is grounded, the anode of the second group of PIN diode series branches (111) is connected to one end of the first MIM capacitor (113), one end of the short-circuit transmission line (112) is grounded, the other end of the short-circuit transmission line (112) is connected to one end of the first MIM capacitor (113), and the other end of the first MIM capacitor (113) is connected to the input end main transmission line (13).

3. The millimeter wave limiting filter chip based on collaborative fusion according to claim 2 is characterized in that: The second-stage amplitude limiting circuit (12) comprises: two PIN diode single tubes (121), the two PIN diode single tubes (121) are symmetrically loaded on the input end main transmission line (13) in the form of reverse parallel connection, and the specific connection relationship is as follows: the anode of the first PIN diode single tube (121) is grounded, and the cathode of the first PIN diode single tube (121) is connected to the quarter-wavelength transmission line (14), and the cathode of the second PIN diode single tube (121) is grounded, and the anode of the second PIN diode single tube (121) is connected to the output end of the quarter-wavelength transmission line (14).

4. The millimeter wave limiting filter chip based on collaborative fusion according to claim 3 is characterized in that: The input end main transmission line (13) is a rectangular microstrip line, one end of the input end main transmission line (13) is loaded with a radio frequency incident signal, and the other end of the input end main transmission line (13) is connected to a common connection point of two limiting units of a first-stage limiting circuit (11); the output end transmission line (17) is a section of a gradient microstrip line, one end of the output end transmission line (17) is connected to an output DC blocking capacitor (16), and the other end of the output end transmission line (17) serves as an output end of the radio frequency signal.

5. The millimeter wave limiting filter chip based on collaborative fusion according to claim 4 is characterized in that: The quarter-wavelength transmission line (14) is a section of a gradient microstrip line, one end of the quarter-wavelength transmission line (14) is connected to a common connection point of two limiting units of a first-stage limiting circuit (11), and the other end of the quarter-wavelength transmission line (14) is connected to a common connection point of two PIN diodes (121).

6. The millimeter wave limiting filter chip based on collaborative fusion according to claim 5 is characterized in that: The semi-lumped parallel resonator (15) comprises: a U-shaped bending transmission line (151) and a second MIM capacitor (152); the U-shaped bending transmission line (151) has an electrical length less than a 45° transmission line; the input end of the U-shaped bending transmission line (151) is connected to a common connection point of two PIN diodes (121); the output end of the U-shaped bending transmission line (151) is connected to an output DC isolation capacitor (16); and the two ends of the second MIM capacitor (152) are bridged between the input end and the output end of the U-shaped bending transmission line (151).

7. The millimeter wave limiting filter chip based on collaborative fusion according to claim 6 is characterized in that: The π-shaped structure (18) comprises: a section of bent microstrip line (181) and two third MIM capacitors (182); the bent microstrip line (181) is a transmission line with an electrical length less than 90°; one end of the bent microstrip line (181) is connected to one end of a first third MIM capacitor (182), and the other end of the first third MIM capacitor (182) is connected to a grounding through hole (21); the other end of the bent microstrip line (181) is connected to one end of a second third MIM capacitor (182), and the other end of the second third MIM capacitor (182) is connected to a grounding through hole (21); wherein a common connection point between the bent microstrip line (181) and the first third MIM capacitor (182) is connected to an input end of the U-shaped bent transmission line (151).

8. The millimeter wave limiting filter chip based on collaborative fusion according to claim 7 is characterized in that: The calculation formulas for the center frequency of the filtering passband of the limiting filter and the first transmission zero point on the left side of the filtering passband are respectively: Where f0 is the center frequency of the filter passband, f TZ1 is the first transmission zero point on the left side of the filter passband, L1 is the equivalent inductance of the short-circuited transmission line (112), Z1 is the characteristic impedance of the short-circuited transmission line (112), θ1 is the electrical length of the short-circuited transmission line (112), C D is the total off-state capacitance value of the PIN diode in each limiting unit in the first-stage limiting circuit (11), and C1 is the capacitance value of the first MIM capacitor (113).

9. The millimeter wave limiting filter chip based on collaborative fusion according to claim 7, characterized in that: The calculation formula of a transmission zero point on the right side of the filtering passband is: Among them, f TZ2 is a transmission zero point on the right side of the filter passband, L2 is the equivalent inductance of the U-shaped bending transmission line (151), Z2 is the characteristic impedance of the U-shaped bending transmission line (151), θ2 is the electrical length of the U-shaped bending transmission line (151), and C2 is the capacitance value of the second MIM capacitor (152).

10. The millimeter wave limiting filter chip based on collaborative fusion according to claim 7, characterized in that: The calculation formula for the second transmission zero point on the left side of the filter passband is: Where C is the speed of light in free space, ε r is the relative dielectric constant of the microwave dielectric substrate (10), and l0 is the physical length of the quarter-wavelength transmission line (14).

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