A negative group delay SSPP transmission circuit suitable for X-band and a control method thereof

Abstract

The application discloses a kind of transmission circuit of negative group delay SSPP suitable for X waveband and control method thereof, belong to microwave engineering technical field, the transmission circuit includes: SSPP transmission line and nested double-ring resonator being arranged in the same side of dielectric substrate;SSPP transmission line is used to provide the slow-wave dispersion characteristic of passband edge;Nested double-ring resonator is laterally coupled with SSPP transmission line, including outer ring resonator and inner ring resonator, for resonant coupling;First coupling gap is formed between the outer ring resonator and SSPP transmission line;The inner ring resonator is nested in the inside of outer ring resonator, and second coupling gap is formed between the inner ring resonator and outer ring resonator;Wherein, the size parameters of the outer ring resonator, inner ring resonator, first coupling gap and second coupling gap are set according to the generation requirement of X waveband negative group delay response and impedance matching requirement, can generate negative group delay effect in high frequency band while still maintaining good impedance matching.

Description

Technical Field

[0001] This invention belongs to the field of microwave engineering technology, and particularly relates to a negative group delay (SSPP) transmission circuit and its control method suitable for the X-band. Background Technology

[0002] Surface plasmon polaritons (SPPs) originated in the field of optics to describe strong localized electromagnetic modes at metal-dielectric interfaces. In the microwave and millimeter-wave frequency bands, metals are near-ideal conductors, making natural SPPs difficult to exist. By performing subwavelength periodic structuring on the metal surface, artificial surface plasmon polaritons (SSPPs) with SPP-like dispersion characteristics can be formed in the low-frequency band. SSPP structures typically possess advantages such as strong field confinement, slow-wave dispersion, and designable cutoff frequencies, providing a new realization path for high-density integrated microwave devices.

[0003] Group delay is a crucial indicator of the phase linearity of transmission networks. Group delay distortion can cause pulse broadening, waveform distortion, and increased bit error rate. Negative Group Delay (NGD) circuits can generate phase lead in specific frequency bands, thus serving as a means of link delay compensation and equalization. Existing NGD implementations include active feedback networks, passive phase shaping networks, and multi-resonant coupling networks. Especially in passive structures, NGD implementation often requires a trade-off between insertion loss and return loss. Meanwhile, achieving a compact structure that balances NGD values, bandwidth, and port matching remains challenging at higher frequency bands, such as the X-band.

[0004] Ring resonator coupling structures can utilize local phase abrupt changes near resonance to form NGD, but traditional microstrip transmission lines are easily limited in the high-frequency band by insufficient phase slope, increased insertion loss, or deteriorated matching. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a negative group delay (SSPP) transmission circuit and its control method suitable for the X-band. By utilizing the slow wave dispersion effect of SSPP and the double-ring nested modulation mechanism, a synergistic effect of large negative group delay and good impedance matching is achieved in the X-band.

[0006] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0007] In a first aspect, the present invention provides a negative group delay (SSPP) transmission circuit suitable for the X-band, comprising: a dielectric substrate based on PCB technology, an SSPP transmission line disposed on the same side of the dielectric substrate, and a nested double-ring resonator.

[0008] The SSPP transmission line includes SSPP transmission units periodically etched on the surface of the dielectric substrate to provide slow-wave dispersion characteristics at the passband edge.

[0009] The nested double-ring resonator is laterally coupled to the SSPP transmission line, including an outer ring resonator and an inner ring resonator, for resonant coupling;

[0010] The outer ring resonator and the SSPP transmission line form a first coupling gap, constituting the main coupling channel;

[0011] The inner ring resonator is nested inside the outer ring resonator and forms a second coupling gap with the outer ring resonator, constituting a secondary loading matching channel;

[0012] The dimensions of the outer ring resonator, inner ring resonator, first coupling gap, and second coupling gap are set according to the requirements for generating the X-band negative group delay response and impedance matching.

[0013] Optionally, the microstrip transmission line includes, in sequence along the signal propagation direction, an input / output feed section, a transition section, and a transmission waveguide section:

[0014] The input / output feed section adopts a microstrip line structure, with a length L1=1mm and a width W1=2.6mm.

[0015] The transition section adopts a step-type gradient structure, which includes multiple gradient units. The height of the initial gradient unit is H1=0.5mm, the height of the final gradient unit is H2=3mm, the height step of the gradient unit is Step=0.5mm, the repeat period of the gradient unit is P=4mm, and the width of the gradient unit is M=2mm.

[0016] Multiple periodically cascaded SSPP transmission units constitute the transmission waveguide segment, with a total length L3=24mm. Each SSPP transmission unit is a T-shaped unit with a height H2=3mm, a width M=2mm, and a repetition period P=4mm.

[0017] Optionally, the specific structural parameters of the nested double-ring resonator are as follows:

[0018] The major axis dimension Ra1 = 12mm and the minor axis dimension Rb1 = 6mm of the outer ring resonator;

[0019] The major axis dimension Ra2 = 4.7 mm and the minor axis dimension Rb2 = 2.0 mm of the inner ring resonator;

[0020] The linewidth of both the outer ring resonator and the inner ring resonator is RW=0.3mm.

[0021] Optionally, the first coupling gap Gap1 = 0.2 mm and the second coupling gap Gap2 = 1 mm.

[0022] Optionally, the dielectric substrate is an F4B high-frequency dielectric substrate with a thickness of 1 mm, a relative permittivity of 2.65, a loss tangent of 0.002, and a copper thickness of 35 μm.

[0023] Optionally, the negative group delay center frequency of the transmission circuit is 10.62 GHz, the group delay magnitude is -6 ns, the negative group delay bandwidth is 90 MHz, and the return loss S in the 8~11 GHz frequency band is... 11 <-18dB.

[0024] Optionally, the nested double-ring resonator adopts an elliptical ring structure.

[0025] In a second aspect, the present invention provides a control method applied to a negative group delay (SSPP) transmission circuit suitable for the X-band as described in any of the first aspects, comprising:

[0026] Based on the requirements for generating a negative group delay response in the X-band and impedance matching requirements, the size parameters of the outer ring resonator, inner ring resonator, first coupling gap and second coupling gap are adjusted respectively.

[0027] By adjusting the size of the SSPP transmission line, the slow wave dispersion and the resonant coupling of the nested double-ring resonator work together to generate a negative group delay response in the X-band.

[0028] Optionally, adjusting the dimensional parameters of the outer ring resonator, inner ring resonator, first coupling gap, and second coupling gap according to the requirement of generating a negative group delay response in the X-band includes:

[0029] Adjust the geometry of the outer ring resonator according to the center frequency of the target negative group time delay response;

[0030] Adjust the width of the first coupling gap based on the target negative group delay value;

[0031] Adjust the geometry of the inner ring resonator and the width of the second coupling gap according to the port impedance matching requirements.

[0032] Optionally, the dispersion characteristics of the SSPP transmission line are achieved by adjusting the height, width, and period parameters of the SSPP transmission unit.

[0033] Compared with existing technologies, the beneficial effects achieved by this invention are as follows: Utilizing the slow-wave high dispersion characteristics of SSPP transmission lines near the cutoff frequency, compared with traditional microstrip lines, the phase slope can be significantly enhanced under the same physical size, thereby achieving a larger negative group delay value. Furthermore, the introduction of the inner-loop resonator provides additional tuning freedom, effectively improving port impedance matching at the resonant frequency and achieving a low reflection coefficient. By combining strong dispersion slow-wave characteristics with a size-adjustable multi-resonant coupling structure, a stronger negative group delay effect is obtained in the X-band, while simultaneously strengthening impedance matching and improving the tunability of the negative group delay effect. The transmission circuit of this invention is based on planar PCB technology and adopts an elliptical double-ring nested structure, which further reduces the planar size of the circuit structure compared to a circular ring structure, making it easier to integrate into X-band microwave communication systems for delay compensation. Attached Figure Description

[0034] Figure 1 The diagram shown is a schematic of an SSPP transmission circuit structure based on PCB technology in one embodiment of the present invention.

[0035] Figure 2 The figure shown is a schematic diagram of the dimensions of the SSPP transmission line and the nested double-ring resonator in one embodiment of the present invention;

[0036] Figure 3 The figure shown is a schematic diagram of the simulation results of the SSPP transmission line dispersion curve in one embodiment of the present invention;

[0037] Figure 4 The figure shown is a schematic diagram of the simulation results of the transmission coefficient and reflection coefficient of the SSPP circuit structure in one embodiment of the present invention;

[0038] Figure 5 The figure shown is a schematic diagram of the simulation results of the SSPP circuit structure in the X-band group delay performance in one embodiment of the present invention.

[0039] Figure 1 In the middle: 1. Dielectric substrate; 2. SSPP transmission line; 3. Nested double-ring resonator. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0041] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0042] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0043] Example 1

[0044] See Figure 1 The present invention discloses a negative group delay (SSPP) transmission circuit suitable for the X-band, comprising a dielectric substrate 1; an SSPP transmission line 2 is constructed on the top layer of the dielectric substrate 1 to form slow wave dispersion and field localization characteristics of the target frequency band; a nested double-ring resonator 3 is disposed on one side of the SSPP transmission line 2 to realize the negative group delay effect and matching adjustment, wherein the nested double-ring resonator is in the form of a concentric ellipse; the bottom layer of the dielectric substrate 1 is a complete metal ground layer to realize broadband signal propagation.

[0045] See Figure 2 The dielectric substrate 1 is an F4B (polytetrafluoroethylene vinyl composite material) high-frequency dielectric substrate with a thickness of 1 mm, a relative permittivity of 2.65, a loss tangent of 0.002, a copper thickness of 35 μm, a length of L = 74 mm, and a width of W = 33.4 mm.

[0046] The SSPP transmission line consists of an input / output feed section, a transition section, and an SSPP waveguide section with a periodic metal structure. The input / output feed section uses a microstrip line structure, with a length of L1 = 2 mm, a width of W1 = 2.6 mm, and a distance of W2 = 10 mm from the edge of the dielectric substrate. It is used to connect to an external SMA connector. The input impedance is adjusted by optimizing the length and width of the input / output feed section. The transition section connects to the microstrip line at one end and to the SSPP waveguide section at the other end. It adopts a step structure and contains 6 gradient units. The initial gradient unit height is H1 = 0.5 mm, the final gradient unit height is H2 = 3 mm, and the transition unit height is... The waveguide segment length L2 = 24 mm, and signal matching conversion is achieved by adjusting the number of gradient units and the height difference. The total length of the waveguide segment L3 = 24 mm is composed of 6 cascaded periodic SSPP transmission units, each of which is a T-type unit with a height H2 = 3 mm. The width of the gradient unit and the periodic T-type unit is M = 2 mm, and the unit repetition period is P = 4 mm. The dispersion characteristics and target cutoff frequency are adjusted by adjusting the height, width, and period of the SSPP transmission unit.

[0047] In the nested double-ring resonator 3, the outer ring resonator has a major axis dimension of Ra1 = 12 mm and a minor axis dimension of Rb1 = 6 mm, while the inner ring resonator has a major axis dimension of Ra2 = 4.7 mm and a minor axis dimension of Rb2 = 2 mm. A lateral first coupling gap of Gap1 = 0.2 mm exists between the outer ring resonator and the SSPP transmission line 2. An internal second coupling gap of Gap2 = 1 mm exists between the outer and inner ring resonators. The linewidth of both the inner and outer rings is Rw = 0.3 mm.

[0048] See Figure 3 This figure shows the dispersion curves of the basic unit of the dual-ring matched X-band SSPP circuit with negative group delay characteristics according to the present invention. The horizontal axis represents the normalized phase constant, and the vertical axis represents the frequency. The solid black line represents the microstrip transmission line dispersion curve, and the dashed red line represents the SSPP transmission line dispersion curve. Figure 3 As shown, the microstrip transmission line exhibits approximately linear dispersion characteristics across the entire frequency band, which can be considered as light in this medium environment. In contrast, the dispersion curve of the SSPP transmission line basically coincides with that of the microstrip line in the low-frequency range, but as the frequency increases, the curve gradually deviates downward from the microstrip line, exhibiting significant nonlinear slow-wave characteristics. As the normalized phase constant approaches the Brillouin zone boundary, i.e., kp / π→1, the SSPP curve tends to flatten and approach the asymptote, with a corresponding cutoff frequency of 13.5 GHz.

[0049] See Figure 4The figure illustrates the transmission coefficient and reflection coefficient curves of an embodiment of the present invention. As shown, three attenuation poles appear throughout the passband, caused by the resonant absorption of the dual-ring resonator, corresponding to the fundamental frequency of the resonant ring (3.54 GHz), the second harmonic (7.08 GHz), and the third harmonic (10.62 GHz), respectively. The center frequency of this design is 10.62 GHz, which actually corresponds to the third harmonic mode of the dual-ring resonator, with an insertion loss of -11.5 dB. Simultaneously, thanks to the modulation effect of the inner ring on the coupling impedance, the reflection coefficient S... 11 The signal strength is below -18dB within the 8-11GHz operating passband. This excellent matching characteristic is a key feature that distinguishes it from traditional NGD circuits, ensuring signal integrity when the circuit is cascaded.

[0050] See Figure 5 The paper presents the group delay curves of an embodiment of the present invention in the 8-12 GHz range. The results show that the NGD center frequency is 10.62 GHz, the group delay is -6 ns, and the negative group delay bandwidth can reach 90 MHz. The large value of NGD here originates from the dispersion enhancement effect, that is, the SSPP transmission line exhibits extremely strong slow wave characteristics in the high-frequency band near the cutoff frequency. This dispersion, combined with the steep phase abrupt change at the third harmonic of the resonator, significantly amplifies the phase slope. This mechanism enables the circuit to achieve significant negative delay performance in the X-band while being easy to fabricate.

[0051] In this embodiment, the strong dispersion characteristics of the SSPP transmission line are utilized to generate a negative group delay by laterally coupling a dual-ring resonator to the SSPP transmission line. Through the synergistic effect of the resonator's higher-order modes and the slow-wave effect of SSPP, a significant delay lead for X-band transmitted signals is achieved. Furthermore, for the nested dual-ring structure, by adjusting the coupling strength between the inner and outer rings and the geometry of the inner ring, a negative group delay effect can be achieved at high frequencies while maintaining good impedance matching. This SSPP circuit structure combines miniaturization, design flexibility, and large-amplitude negative group delay with good matching characteristics in the X-band, effectively overcoming the bottlenecks of traditional microstrip NGD circuits in high-frequency applications and providing broad prospects for microwave communication, radar systems, and sensing applications.

[0052] Example 2

[0053] This embodiment provides a control method applied to the negative group delay (SSPP) transmission circuit suitable for the X-band described in any step of Embodiment 1, including:

[0054] Adjust the geometry of the outer ring resonator according to the center frequency of the target negative group time delay response;

[0055] Adjust the width of the first coupling gap based on the target negative group delay value;

[0056] Adjust the geometry of the inner ring resonator and the width of the second coupling gap according to the port impedance matching requirements;

[0057] By adjusting the size, the slow-wave dispersion characteristics of SSPP transmission line 2, in conjunction with the resonant coupling of the nested double-ring resonator, generate a negative group delay response in the X-band.

[0058] In this embodiment, the dispersion characteristics of the SSPP transmission line 2 are achieved by adjusting the height, width, and period parameters of the SSPP transmission unit.

[0059] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A control method for a negative group delay (SSPP) transmission circuit suitable for the X-band, characterized in that, The transmission circuit includes: a dielectric substrate based on PCB technology, an SSPP transmission line disposed on the same side of the dielectric substrate, and a nested double-ring resonator. The SSPP transmission line includes SSPP transmission units periodically etched on the surface of the dielectric substrate to provide slow-wave dispersion characteristics at the passband edge. The nested double-ring resonator is laterally coupled to the SSPP transmission line, including an outer ring resonator and an inner ring resonator, for resonant coupling; The outer ring resonator and the SSPP transmission line form a first coupling gap, constituting the main coupling channel; The inner ring resonator is nested inside the outer ring resonator and forms a second coupling gap with the outer ring resonator, constituting a secondary loading matching channel; The nested double-ring resonator adopts an elliptical ring structure; the size parameters of the outer ring resonator, inner ring resonator, first coupling gap and second coupling gap are set according to the generation requirements of X-band negative group delay response and impedance matching requirements. The control method includes: Adjust the geometry of the outer ring resonator according to the center frequency of the target negative group time delay response; Adjust the width of the first coupling gap based on the target negative group delay value; Adjust the geometry of the inner ring resonator and the width of the second coupling gap according to the port impedance matching requirements; By adjusting the size of the SSPP transmission line, the slow wave dispersion and the resonant coupling of the nested double-ring resonator work together to generate a negative group delay response in the X-band. The dispersion characteristics of the SSPP transmission line are achieved by adjusting the height, width and period parameters of the SSPP transmission unit.

2. The control method for negative group delay SSPP transmission circuits applicable to the X-band according to claim 1, characterized in that, The SSPP transmission line, along the signal propagation direction, includes, in sequence, an input / output feed section, a transition section, and a transmission waveguide section: The input / output feed section adopts a microstrip line structure, with a length L1=1mm and a width W1=2.6mm. The transition section adopts a step-type gradient structure, which includes multiple gradient units. The height of the initial gradient unit is H1=0.5mm, the height of the final gradient unit is H2=3mm, the height step of the gradient unit is Step=0.5mm, the repeat period of the gradient unit is P=4mm, and the width of the gradient unit is M=2mm. Multiple periodically cascaded SSPP transmission units constitute the transmission waveguide segment, with a total length L3=24mm. Each SSPP transmission unit is a T-shaped unit with a height H2=3mm, a width M=2mm, and a repetition period P=4mm.

3. The control method for negative group delay SSPP transmission circuits applicable to the X-band according to claim 1, characterized in that, The specific structural parameters of the nested double-ring resonator are as follows: The major axis dimension Ra1 = 12mm and the minor axis dimension Rb1 = 6mm of the outer ring resonator; The major axis dimension Ra2 = 4.7 mm and the minor axis dimension Rb2 = 2.0 mm of the inner ring resonator; The linewidth of both the outer ring resonator and the inner ring resonator is RW=0.3mm.

4. The control method for negative group delay SSPP transmission circuits applicable to the X-band according to claim 1, characterized in that, The first coupling gap Gap1 = 0.2 mm, and the second coupling gap Gap2 = 1 mm.

5. The control method for negative group delay SSPP transmission circuits applicable to the X-band according to claim 1, characterized in that, The dielectric substrate is an F4B high-frequency dielectric substrate with a thickness of 1 mm, a relative permittivity of 2.65, a loss tangent of 0.002, and a copper thickness of 35 μm.

6. The control method for negative group delay SSPP transmission circuits applicable to the X-band according to claim 1, characterized in that, The negative group delay center frequency of the transmission circuit is 10.62GHz, the group delay is -6ns, the negative group delay bandwidth is 90MHz, and the return loss S11 is <-18dB in the 8~11GHz frequency band.

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