Wideband filter with adjustable notch

Abstract

The present invention discloses a broadband filter with adjustable notch, comprising a single-layer quarter-mode substrate integrated waveguide resonant cavity, a signal metal layer in the form of an isosceles right triangle, and a signal input microstrip line and a signal output microstrip line are respectively arranged along two right-angled sides of the signal metal layer; a first slit is etched on the signal metal layer near the position of the signal input microstrip line, and a second slit is etched on the signal metal layer near the position of the signal output microstrip line, a first adjustable device is arranged in the first slit, and a second adjustable device is arranged in the second slit. The present invention loads a varactor diode in the port gap of the broadband filter, and loads a bias voltage at both ends of the varactor diode, and a narrow stop band can be superimposed on the original broadband of the broadband filter, thereby introducing a notch frequency, and the notch frequency can be continuously adjusted within the full passband range by changing the capacitance of the varactor diode, and a PIN diode is used to adjust the frequency, thereby enhancing the adaptive ability of the broadband filter.

Description

Technical Field

[0001] The invention belongs to the technical field of filters, and in particular relates to a broadband filter with adjustable notch. Background Art

[0002] Since the U.S. Federal Communications Commission (FCC) released the UWB frequency band communication standard in February 2002, UWB wireless communication technology has garnered significant attention due to its high data transmission rates, low loss, flexibility, and maneuverability. As a crucial component in this system, the UWB filter significantly impacts its performance.

[0003] In increasingly complex broadband and ultra-wideband communications, noise inevitably exists within the wide passband, disrupting the quality of broadband communications. Therefore, broadband filters often require a steep stopband at the noise frequency to suppress this noise. This stopband is often called a "notch." As a specialized band-stop filter, notch filters enable broadband and ultra-wideband filters to better adapt to complex communication environments, and therefore play a vital role in the RF front-ends of future civilian and military communication systems.

[0004] In recent years, scholars both domestically and internationally have conducted research on broadband and ultra-wideband microwave filters loaded with notch frequencies. A paper titled "Multiple Band Notched Filter Using C-Shaped and E-Shaped Resonator for UWB Applications," published in IEEE Microwave and Wireless Components Letters, proposes a notch filter designed using E-shaped and C-shaped microstrip lines and a triangular ring-loaded short resonator structure. This notch filter can generate three notches in the 3.09–10.618 GHz range. In a paper titled "Novel Wideband Bandpass Filter with Dual Notched Bands Using Stub-Loaded Resonators," also published in IEEE Microwave and Wireless Components Letters, the authors design a notch filter using two slot-loaded resonators to generate two fixed-frequency notches across a wideband. In a paper titled "Low-cost and compact wideband microwave notch filter based on miniaturized complementary metaresonator," a broadband filter with a single notch frequency is designed using a complementary circular spiral resonator (CCSR).

[0005] However, most of these designs combine a stopband-generating structure with a bandpass filter to create a fixed notch frequency. This results in a complex structure and a lack of dynamic adjustment. The resulting notch frequency cannot be adjusted with noise fluctuations, making it inflexible for eliminating interference signals within a wideband. Consequently, researchers both domestically and internationally have attempted to develop tunable notch frequency filters. For example, in a paper titled "Switchable Embedded Notch Structure for UWB Bandpass Filter," published in the IEEE Microwave and Wireless Components Letters, the authors manipulate the appearance of a broadband notch frequency by switching a PIN diode on and off. Regarding full tunability, due to the wide bandwidth, the center frequency adjustment effect is limited, making it difficult to achieve a wide frequency range. Consequently, recent efforts to develop fully tunable broadband and ultra-wideband filters have focused on both bandwidth and notch frequency adjustment. However, these technologies still suffer from a narrow notch adjustment range, failing to meet the flexible interference elimination requirements of broadband systems. Furthermore, the large number of electronic components required not only increases the filter's size and difficulty in processing and soldering, but also introduces significant losses during the filtering process. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to address the deficiencies in the above-mentioned prior art and provide a broadband filter with adjustable notch. The filter has a simple structure and a reasonable design. By loading a varactor diode at the port gap of the broadband filter and loading a bias voltage at both ends of the varactor diode, a narrow stopband can be superimposed on the original broadband of the broadband filter, thereby introducing a notch frequency. By changing the capacitance of the varactor diode, the notch frequency can be continuously adjusted within the full passband range. At the same time, a PIN diode is used to adjust the frequency, thereby enhancing the adaptive ability of the broadband filter and achieving good use effect.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a broadband filter with adjustable notch, characterized in that: it includes a single-layer quarter-mode substrate integrated waveguide resonant cavity, the single-layer quarter-mode substrate integrated waveguide resonant cavity includes a dielectric layer, a signal metal layer arranged on the upper surface of the dielectric layer, and a ground metal layer plated on the lower surface of the dielectric layer, the single-layer quarter-mode substrate integrated waveguide resonant cavity is obtained by cutting along the diagonal magnetic wall of the substrate integrated waveguide square resonant cavity on the surface of the signal metal layer, the signal metal layer is an isosceles right triangle, and along the two straight lines of the signal metal layer, the ground metal layer is cut into two diagonal lines. A signal input microstrip line and a signal output microstrip line are respectively provided at the corner edges; a plurality of metal through holes penetrating the signal metal layer and the ground metal layer are evenly distributed on the dielectric layer along the oblique side direction of the signal metal layer; a disturbance hole penetrating the signal metal layer and the ground metal layer is provided in the single-layer quarter-mode substrate integrated waveguide resonant cavity; a first gap is etched on the signal metal layer near the position of the signal input microstrip line, and a second gap is etched on the signal metal layer near the position of the signal output microstrip line; a first adjustable device is provided in the first gap, and a second adjustable device is provided in the second gap.

[0008] The above-mentioned broadband filter with adjustable notch is characterized in that a first connecting medium and a second connecting medium are respectively provided on the two right-angled sides of the signal metal layer, the first connecting medium is connected to the anode of the first diode, and the cathode of the first diode is grounded, and the second connecting medium is connected to the anode of the second diode, and the cathode of the second connecting medium is grounded.

[0009] The above-mentioned broadband filter with adjustable notch is characterized in that the first connecting medium and the second connecting medium are symmetrically arranged along the symmetry axis of the single-layer quarter-mode substrate integrated waveguide resonant cavity.

[0010] The above-mentioned broadband filter with adjustable notch is characterized in that the first adjustable component is a first varactor diode, the second adjustable component is a second varactor diode, and the sizes of the first varactor diode and the second varactor diode are adjustable.

[0011] The above-mentioned broadband filter with adjustable notch is characterized in that the number of the first adjustable component is at least one, and the number of the second adjustable component is at least one.

[0012] The above-mentioned broadband filter with adjustable notch is characterized in that the sizes of the first gap and the second gap are adjustable respectively.

[0013] The above-mentioned broadband filter with adjustable notch is characterized in that the first slot and the second slot are symmetrically arranged along the symmetry axis of the single-layer quarter-mode substrate integrated waveguide resonant cavity.

[0014] The above-mentioned broadband filter with adjustable notch is characterized in that the slot shapes of the first slot and the second slot are respectively any one of C-type, L-type, I-type and rectangular.

[0015] The above-mentioned broadband filter with adjustable notch is characterized in that the distance between two adjacent metal through holes is less than a quarter of a wavelength.

[0016] The above-mentioned broadband filter with adjustable notch is characterized in that: the first slot is parallel to the signal input microstrip line, and the second slot signal metal layer is parallel to the signal output microstrip line.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. The present invention has a simple structure, reasonable design, and is easy to implement and operate.

[0019] 2. The present invention divides the full-mode SIW resonant cavity twice along the diagonal line to obtain a single-layer quarter-mode substrate integrated waveguide resonant cavity, whose area is only 25% of the full-mode SIW resonant cavity. In addition, the QMSIW resonant cavity obtained by division can approach the effect produced by the full-mode SIW resonant cavity and has good use effect.

[0020] 3. The present invention loads a varactor diode at the port gap of the broadband filter. By loading a bias voltage at both ends of the varactor diode, a specific capacitance can be formed at the gap, thereby generating a high impedance to suppress the noise at that frequency point. In this way, a narrow stopband is formed on the frequency response. The stopband is superimposed on the broadband of the original broadband filter, and the resulting composite effect is a broadband filter with a notch frequency. By adjusting the capacitance of the varactor diode within a certain range, the notch frequency can be continuously adjusted within the full passband range, and the bandwidth can be kept stable, with good out-of-band suppression.

[0021] 4. The present invention protrudes a connecting medium on each of the two right-angled sides of the signal metal layer, which serves as a bridge between the signal metal layer and the PIN diode. The PIN diode is used to change the bandwidth, enhance the adaptability of the broadband filter, and has a strong out-of-band suppression characteristic.

[0022] In summary, the present invention has a simple structure and a reasonable design. By loading a varactor diode at the port gap of the broadband filter and loading a bias voltage at both ends of the varactor diode, a narrow stopband can be superimposed on the original broadband of the broadband filter, thereby introducing a notch frequency. By changing the capacitance value of the varactor diode, the notch frequency can be continuously adjusted within the full passband range. At the same time, the PIN diode is used to adjust the frequency, thereby enhancing the adaptability of the broadband filter and achieving good use effect.

[0023] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of the present invention.

[0025] Figure 2 Schematic diagram of the structure of the signal metal layer of the present invention.

[0026] Figure 3 This is a dimension diagram of the signal metal layer of the present invention.

[0027] Figure 4 The figure is a relationship diagram of the capacitance of the varactor diode of the present invention, the notch frequency and the no-load Q value.

[0028] Figure 5 This is a simulation diagram of the notch frequency of the present invention.

[0029] Description of the accompanying drawings:

[0030] 1—Signal metal layer; 2—Dielectric layer; 3—Ground metal layer;

[0031] 101—metal through hole; 102—disturbance hole; 103—signal input microstrip line;

[0032] 104—Signal output microstrip line; 105—Second slot; 106—First slot;

[0033] 107—first varactor diode; 108—second varactor diode; 109—first connecting medium;

[0034] 110—first diode; 111—second connecting medium; 112—second diode. DETAILED DESCRIPTION

[0035] The method of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments of the present invention.

[0036] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0037] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0038] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can, for example, be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0039] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used herein to describe the spatial positional relationship of a device or feature to other devices or features as shown in the figures. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figures. For example, if the device in the drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0040] like Figure 1 and Figure 2 As shown, the present invention includes a single-layer quarter-mode substrate integrated waveguide resonant cavity, which includes a dielectric layer 2, a signal metal layer 1 disposed on the upper surface of the dielectric layer 2, and a ground metal layer 3 plated on the lower surface of the dielectric layer. The single-layer quarter-mode substrate integrated waveguide resonant cavity is obtained by cutting the surface of the signal metal layer 1 along the diagonal magnetic wall of the substrate integrated waveguide square resonant cavity. The signal metal layer 1 is an isosceles right triangle, and a signal input microstrip line 103 and a signal output microstrip line 104 are respectively disposed along the two right-angled sides of the signal metal layer 1. The dielectric layer 2 has a plurality of metal through-holes 101 uniformly distributed along the hypotenuse direction of the signal metal layer 1, penetrating the signal metal layer 1 and the ground metal layer 3. The single-layer quarter-mode substrate integrated waveguide resonant cavity is provided with a perturbation hole 102 penetrating the signal metal layer 1 and the ground metal layer 3.

[0041] In specific implementation, the present application adopts a QMSIW resonant cavity, and realizes a broadband filter by plating a signal metal layer 1 and a ground metal layer 3 on the upper and lower surfaces of the dielectric layer 2 respectively.

[0042] In actual use, the main body size of the broadband filter is 36mm×36mm×1mm. The signal input microstrip line 103 and the signal output microstrip line 104 are both 50 ohm microstrip lines, and their lengths are as follows: Figure 3 As shown, L1 is 17.5 mm. The signal input microstrip line 103 is parallel to one right-angled side of the signal metal layer 1 , and the signal output microstrip line 104 is parallel to the other right-angled side of the signal metal layer 1 .

[0043] The QMSIW resonant cavity of this application is a full-mode SIW resonant cavity divided twice evenly along the diagonal. Its area is only 25% of the full-mode SIW resonant cavity, reducing its volume and achieving a near-full-mode SIW resonant cavity effect. The signal metal layer 1 in the resulting QMSIW resonant cavity forms an isosceles right triangle, with its two right-angled sides forming two equivalent magnetic walls and the hypotenuse forming an equivalent electric wall. Metal vias 101 are evenly distributed along the hypotenuse.

[0044] In actual use, the diameter of the metal through-hole 101 is 0.6 mm, and the distance between two adjacent metal through-holes 101 is less than a quarter of a wavelength. Preferably, the distance between two adjacent metal through-holes 101 is 0.75 mm.

[0045] An identical isosceles right triangle was cut from each acute angle of the signal metal layer 1 as a micro-perturbation mechanism. The two isosceles right triangles were symmetrically arranged along the perpendicular line from the right angle vertex to the hypotenuse. Simultaneously, a perturbation hole 102 was opened along the symmetry axis of the single-layer quarter-mode substrate integrated waveguide resonant cavity. The hypotenuse length L3 of the signal metal layer 1 was 15.5 mm, and the right angle side L4 of the cut isosceles right triangle was 2.8 mm.

[0046] In this embodiment, a first slit 106 is etched on the signal metal layer 1 near the signal input microstrip line 103 , and a second slit 105 is etched on the signal metal layer 1 near the signal output microstrip line 104 . A first adjustable device is provided in the first slit 106 , and a second adjustable device is provided in the second slit 105 .

[0047] Both the signal input microstrip line 103 and the signal output microstrip line 104 are 50Ω microstrip lines. These lines serve as ports for the broadband filter. To load tunable components and introduce notches within the broadband, slots are provided at each port. These slots alter the distribution of the electric and magnetic fields in the signal metal layer 1, significantly reducing the filter's resonant frequency.

[0048] It should be noted that the length of the slot determines the bandwidth of the filter. The longer the slot, the narrower the bandwidth. The length and width of the first slot 106 and the second slot 105 can be calculated according to the actual needs of the broadband filter. The length of the first slot 106 and the second slot 105 determines the miniaturization degree of the substrate integrated waveguide. The length and width of the first slot 106 and the second slot 105 are adjustable. The shape of the first slot 106 and the second slot 105 is determined according to the actual length. Figure 3 As shown, both the first slot 106 and the second slot 105 are rectangular slots. The first slot 106 is parallel to the signal input microstrip line 103, and the second slot 105 signal metal layer 1 is parallel to the signal output microstrip line 104. The length of the first slot 106 and the second slot 105 are both L6 = 1 mm, and the width of the first slot 106 and the second slot 105 are both L5 = 0.4 mm.

[0049] In actual use, the first adjustable component is a first varactor diode 107, and the second adjustable component is a second varactor diode 108. There is at least one first adjustable component, and at least one second adjustable component. In this embodiment, there is one first varactor diode 107 and one second varactor diode 108.

[0050] A varactor diode is loaded at the port gap of the broadband filter. The varactor diode is a diode whose junction capacitance changes with the bias voltage. By loading a bias voltage at both ends of the varactor diode, a specific capacitance can be formed at the gap, thereby generating a high impedance to suppress the noise at that frequency. In this way, a narrow stopband is formed in the frequency response. This stopband is superimposed on the broadband of the original broadband filter, thereby introducing a notch frequency. The broadband filter is a broadband filter with a notch frequency.

[0051] According to the formula It can be seen that the capacitance value C of the varactor diode is negatively correlated with the notch frequency ω. Changing the capacitance value C of the varactor diode can change the notch frequency ω. Increasing the capacitance value C of the varactor diode decreases the notch frequency ω; decreasing the capacitance value C of the varactor diode increases the notch frequency ω. Therefore, by adjusting the capacitance value C of the varactor diode within a certain range, the notch frequency ω can be continuously adjusted across the entire passband, while maintaining a stable bandwidth and achieving good out-of-band suppression.

[0052] like Figure 4 As shown in the figure, when the capacitance C of the varactor diode varies in the range of 0.6 to 1.65 pF, the notch frequency ω can be continuously adjusted in the range of 4 to 6.3 GHz, almost covering the entire passband of the broadband filter. At the same time, the unloaded Q value of the filter remains between 313 and 315 without significant changes.

[0053] like Figure 5 As shown, the horizontal axis represents the notch frequency ω, and the vertical axis represents the return loss. By adjusting the capacitance C of the varactor diode within the range of 0.6 to 1.47 pF, the notch frequency ω can be continuously adjusted within the full passband range, while maintaining bandwidth stability and achieving good out-of-band suppression. In this embodiment, a first connecting medium 109 and a second connecting medium 111 are respectively provided on the two right-angled sides of the signal metal layer 1. The first connecting medium 109 is connected to the anode of the first diode 110, and the cathode of the first diode 110 is grounded. The second connecting medium 111 is connected to the anode of the second diode 112, and the cathode of the second connecting medium 111 is grounded.

[0054] In actual use, the first connecting dielectric 109 and the second connecting dielectric 111 are used to improve the performance of the filter passband and serve as a bridge between the signal metal layer 1 and the PIN diode. The presence or position of the connecting dielectric will affect the out-of-band suppression capability of the passband. The size of the first connecting dielectric 109 and the second connecting dielectric 111 are both adjustable. It should be noted that in this embodiment, the first connecting dielectric 109 and the second connecting dielectric 111 are both rectangular, with a length L8 = 2.4 mm and a width L7 = 1.4 mm. The closest vertical distance L2 between the first connecting dielectric 109 and the second connecting dielectric 111 and the right-angled vertex of the signal metal layer 1 is 6 mm.

[0055] In a specific implementation, the first diode 110 and the second diode 112 are both PIN diodes. When the PIN diodes are connected, they cause electromagnetic field disturbances at their locations, thereby achieving the effect of frequency regulation, improving the performance of the filter passband, enhancing the adaptability of the broadband filter, and having strong out-of-band suppression characteristics.

[0056] The above description is merely an embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A broadband filter with adjustable notch, characterized in that: The invention comprises a single-layer quarter-mode substrate integrated waveguide resonant cavity, the single-layer quarter-mode substrate integrated waveguide resonant cavity comprising a dielectric layer (2), a signal metal layer (1) arranged on the upper surface of the dielectric layer (2), and a grounding metal layer (3) plated on the lower surface of the dielectric layer, the single-layer quarter-mode substrate integrated waveguide resonant cavity is obtained by cutting the surface of the signal metal layer (1) along the diagonal magnetic wall of the substrate integrated waveguide square resonant cavity, the signal metal layer (1) is an isosceles right triangle, and a signal input microstrip line (103) and a signal output microstrip line (104) are respectively arranged along two right-angled sides of the signal metal layer (1), the dielectric layer (2) has a plurality of metal through holes (101) that penetrate the signal metal layer (1) and the grounding metal layer (3) uniformly distributed along the hypotenuse direction of the signal metal layer (1), and a disturbance hole (102) that penetrates the signal metal layer (1) and the grounding metal layer (3) is arranged in the single-layer quarter-mode substrate integrated waveguide resonant cavity; The signal metal layer (1) is etched with a first slit (106) near the signal input microstrip line (103), and the signal metal layer (1) is etched with a second slit (105) near the signal output microstrip line (104); a first adjustable component is arranged in the first slit (106), and a second adjustable component is arranged in the second slit (105); A first connecting medium (109) and a second connecting medium (111) are respectively arranged on two right-angled sides of the signal metal layer (1), the first connecting medium (109) is connected to the anode of the first diode (110), the cathode of the first diode (110) is grounded, the second connecting medium (111) is connected to the anode of the second diode (112), and the cathode of the second connecting medium (111) is grounded; The first adjustable component is a first variable capacitance diode (107), and the second adjustable component is a second variable capacitance diode (108). The sizes of the first variable capacitance diode (107) and the second variable capacitance diode (108) are adjustable.

2. The broadband filter with adjustable notch according to claim 1, characterized in that: The first connecting medium (109) and the second connecting medium (111) are symmetrically arranged along the symmetry axis of the single-layer quarter-mode substrate integrated waveguide resonant cavity.

3. The broadband filter with adjustable notch according to claim 1, characterized in that: The number of the first adjustable components is at least one, and the number of the second adjustable components is at least one.

4. The broadband filter with adjustable notch according to claim 1, characterized in that: The sizes of the first gap (106) and the second gap (105) are both adjustable.

5. The broadband filter with adjustable notch according to claim 1, characterized in that: The first slot (106) and the second slot (105) are symmetrically arranged along the symmetry axis of the single-layer quarter-mode substrate integrated waveguide resonant cavity.

6. The broadband filter with adjustable notch according to claim 5, characterized in that: The shapes of the first gap (106) and the second gap (105) include any one of C-type, L-type, I-type and rectangular type.

7. The broadband filter with adjustable notch according to claim 1, characterized in that: The distance between two adjacent metal through holes (101) is less than a quarter of a wavelength.

8. The broadband filter with adjustable notch according to claim 5, characterized in that: The first slot (106) is parallel to the signal input microstrip line (103), and the second slot (105) signal metal layer (1) is parallel to the signal output microstrip line (104).

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