Broadband band-pass filter based on GaAs technology
The broadband bandpass filter designed using GaAs technology, combined with the LC equivalent circuit model and specific geometry, solves the problem of large filter area in existing technologies, and realizes low-loss and miniaturized filter design, which is suitable for high-density RF front-end integration.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANJING UNIV OF INFORMATION SCI & TECH
- Filing Date
- 2026-02-13
- Publication Date
- 2026-05-19
AI Technical Summary
When implementing on-chip broadband bandpass filters with low insertion loss in semiconductor processes, existing technologies suffer from the problem of occupying a large chip area, making it difficult to simultaneously achieve filter miniaturization and low loss.
A broadband bandpass filter was designed using GaAs technology. By constructing an LC equivalent circuit model of the second metal layer, the geometric parameters of the filter structure were optimized. By combining capacitively coupled feed lines, T-strips, and inverted T-strips, the transmission zero point and center frequency can be flexibly adjusted, reducing insertion loss and shrinking the filter size.
It achieves a compact filter structure, low insertion loss, and wide operating bandwidth, adapting to the needs of different communication frequency bands and suitable for high-density RF front-end integration.
Smart Images
Figure CN122068264A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of radio frequency communication technology, and in particular to a broadband bandpass filter based on GaAs technology. Background Technology
[0002] In recent years, the rapid development of wireless communication has greatly fueled the research boom in bandpass filters. Bandpass filters are core components in radio frequency and millimeter-wave systems, including broadband bandpass filters, multi-band bandpass filters, and reconfigurable bandpass filters. Currently, various techniques and methods for realizing broadband bandpass filters have been proposed.
[0003] However, as radio frequency front-ends evolve from traditional microwave to millimeter-wave operating frequencies, realizing on-chip broadband bandpass filters with low insertion loss in semiconductor processes remains a challenging task.
[0004] To address this issue, lower insertion loss can be achieved through improved coupled-line hairpin cell designs and the use of SiGeBiCMOS technology. However, existing designs often result in a large chip area footprint.
[0005] Therefore, achieving low insertion loss while minimizing the size of the filter is a problem that urgently needs to be solved. Summary of the Invention
[0006] The purpose of this invention is to provide a broadband bandpass filter based on GaAs technology. The filter, from bottom to top, includes a metal ground plane, a substrate layer, and a dielectric film layer, a first metal layer embedded within the dielectric film layer, a second metal layer on the upper surface of the dielectric film layer, and a ground metal via connecting the second metal layer, the first metal layer, the dielectric film layer, and the substrate layer. The second metal layer is a key component of the filter, consisting of a pair of capacitively coupled feed lines, a pair of T-shaped stripes, and an inverted T-shaped stripe. The first and second metal layers have the same or different geometric structures and parameters, and are connected through the ground metal via. By constructing an LC equivalent circuit model of the second metal layer filter structure, the geometric parameters of the filter structure are optimized, enabling flexible adjustment of the transmission zero point and center frequency. The broadband bandpass filter provided by this invention has the advantages of compact size, low insertion loss, and wide operating bandwidth.
[0007] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a broadband bandpass filter based on GaAs technology, which, from bottom to top, includes a metal ground plane, a substrate layer and a dielectric film layer, a first metal layer embedded in the dielectric film layer and a second metal layer on the upper surface of the dielectric film layer, and a ground metal via connecting the second metal layer, the first metal layer, the dielectric film layer and the substrate layer. As one possible implementation, the first metal layer and the second metal layer have the same structure and equal geometric parameters; or, the first metal layer and the second metal layer have the same structure but different geometric parameters; or, the first metal layer and the second metal layer have different structures and different geometric parameters.
[0008] As one possible implementation, the cross-section containing the central axis of the through-hole is defined as the reference plane, and the second metal layer includes: A pair of capacitively coupled feed lines are distributed symmetrically with the reference plane as the symmetric plane. Each capacitively coupled feed line includes a feed line and a coupling line with a gap between them, wherein the feed line is located outside the coupling line. A pair of T-shaped strips are symmetrically distributed on the inner side of a pair of capacitively coupled feed lines with the reference plane as the symmetrical plane; the outward-extending end of the head of each T-shaped strip is connected to its corresponding coupling line, and the inward-extending ends of the heads of the two T-shaped strips are joined together. An inverted T-shaped strip is located inside a pair of T-shaped strips, and the central section of the inverted T-shaped strip is coplanar with the reference plane; there are gaps between the two ends of the head of the inverted T-shaped strip and the coupling line adjacent to it, and the bottom end of the tail of the inverted T-shaped strip is connected to the joint of the two T-shaped strips.
[0009] As one possible implementation, an LC equivalent circuit of a broadband bandpass filter is constructed. The relationship between the changes in inductance and capacitance in the LC equivalent circuit and the position of the transmission zero point and the center frequency is analyzed. The geometric parameters of the metal lines included in the capacitively coupled feed line, T-strip, and inverted T-strip are optimized. The geometric parameters include the length and width of each metal line and the spacing between adjacent metal lines.
[0010] As one possible implementation, the LC equivalent circuit can be constructed as follows: The feeder is equivalent to a pair of inductors in series. L 4 and capacitor C 2; The capacitive coupling formed by the gap between each feed line and its adjacent coupling line is equivalent to a capacitor. C 1. Each capacitor C 1 is connected in series with an inductor. L 4 and capacitor C 2 in parallel; A pair of T-shaped strips can be equated to a pair of inductors. L 1. Inductor L 2. Inductance L 5 and capacitor C A circuit consisting of 3 components; where the inductor... L 1 and inductor L 2. Series, Inductance L 5 and capacitorC 3. Series connection, series inductors L 1 and inductor L 2. Inductors in series L 5 and capacitor C 3 inductors connected in parallel and in series L 1 and inductor L 2 and capacitor C 1. Series connection; The inverted T-shaped strip is equivalent to an inductor L 6. Capacitor 2 C 4 and capacitor 2 C A 5-element LC resonant circuit is formed, and the LC resonant circuit is connected in series with an inductor. L 5 and capacitor C 3 in parallel; The grounding metal via is equivalent to an inductor. L 3. Inductance L 3 is connected in series with the LC resonant circuit.
[0011] As one possible implementation, the LC equivalent circuit is further equivalent to an odd-mode circuit and an even-mode circuit. Using the odd-mode calculation method, the odd-mode input impedance and even-mode input impedance are calculated separately, and the expression for generating a transmission zero at frequency f is further derived. The independent variable in the expression for the transmission zero includes inductance. L 4 and capacitor C 2. The position of the transmission zero point is adjusted in the following way: Fixed capacitor C 2. Adjust the inductance L 4. Change the position of the transmission zero point until the first preset position is reached, then fix the inductor. L 4. Change the capacitance C 2. Fine-tune the position of the transmission zero point until it reaches the second preset position, so as to finally determine the inductance. L 4 and capacitor C 2. Determine the length and width of the feeder.
[0012] As one possible implementation, the expression for the transmission zero generated at frequency f is: .
[0013] As one possible implementation, this can be achieved by adjusting the capacitor. C 4. Adjust the center frequency position to the preset position. Based on this, determine the length and width of the tail of the inverted T-shaped strip, the length and width of the head, and the spacing between the T-shaped strip and the coupling line.
[0014] As one possible implementation, the substrate layer has a thickness of 100 μm and a relative permittivity of 12.9; The dielectric film has a thickness of 4.69 μm and a relative permittivity of 6.9; The thickness of the first metal layer is 1.065 μm, and its conductivity is 4 × 10⁻⁶. 7 S / m; the second metal layer has a thickness of 3.5 μm and a conductivity of 4 × 10⁻⁶. 7 S / m.
[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The broadband bandpass filter based on GaAs technology provided by this invention reduces insertion loss while simplifying the structure and miniaturizing the size, effectively solving the technical problem of "miniaturization and low loss". Attached Figure Description
[0016] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the structure of a broadband bandpass filter provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the second metal layer structure of the broadband bandpass filter provided in an embodiment of the present invention; Figure 3 The LC equivalent circuit diagram of the broadband bandpass filter provided in the embodiment of the present invention; Figure 4 The odd-mode equivalent circuit diagram of the LC equivalent circuit of the broadband bandpass filter provided in the embodiment of the present invention; Figure 5 The even-mode equivalent circuit diagram of the LC equivalent circuit of the broadband bandpass filter provided in the embodiment of the present invention; Figure 6 The electromagnetic model and LC equivalent circuit simulation S-parameter diagram of the broadband bandpass filter provided in the embodiments of the present invention; Figure 7 The effect of inductor L4 adjustment on transmission zero in the LC equivalent circuit of the broadband bandpass filter provided in this embodiment of the invention; Figure 8 The effect of adjusting capacitor C2 on the transmission zero point in the LC equivalent circuit of the broadband bandpass filter provided in this embodiment of the invention; Figure 9 The effect of changing capacitor C4 on the center frequency of the broadband bandpass filter provided in the embodiment of the present invention. Figure 10 The simulation results of the broadband bandpass filter provided in the embodiments of the present invention and the test results of the broadband bandpass filter prototype using a GSG probe and a vector network analyzer are presented.
[0017] Figure Labels 1-Grounded metal layer; 2-Substrate layer; 3-Dielectric film layer 4-Second metal layer M2; 40 - Capacitively coupled feeder, 401 - Feeder, 402 - Coupler; 41-T-shaped strip, 42-Inverted T-shaped strip, 43-Through hole; 5-First metal layer M1; 6-Grounding metal via; 60 - Through hole. Detailed Implementation
[0018] To facilitate a clear description of the technical solutions in the embodiments of the present invention, the terms "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect. For example, the first threshold and the second threshold are merely used to distinguish different thresholds and do not limit their order. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and that the terms "first" and "second" are not necessarily different.
[0019] It should be noted that in this invention, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.
[0020] In this invention, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one" or similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, "at least one of a, b, or c" can represent: a, b, c, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple.
[0021] To achieve low insertion loss while minimizing filter size, this invention provides a broadband bandpass filter based on GaAs technology. The filter, from bottom to top, includes a metal ground plane, a substrate layer, and a dielectric film layer; a first metal layer embedded within the dielectric film layer and a second metal layer on the upper surface of the dielectric film layer; and a ground metal via connecting the second metal layer, the first metal layer, the dielectric film layer, and the substrate layer. The second metal layer is a key component of the filter, consisting of a pair of capacitively coupled feed lines, a pair of T-shaped stripes, and an inverted T-shaped stripe. The first and second metal layers have the same or different geometric structures and parameters and are connected through the ground metal via. By constructing an LC equivalent circuit model of the second metal layer filter structure, the geometric parameters of the filter structure are optimized, enabling flexible adjustment of the transmission zero point and center frequency. The broadband bandpass filter provided by this invention has the advantages of compact size, low insertion loss, and wide operating bandwidth.
[0022] This invention provides a broadband bandpass filter based on GaAs technology, which includes, from bottom to top, a metal ground plane 1, a substrate layer 2 and a dielectric film layer 3, a first metal layer 5 embedded in the dielectric film layer and a second metal layer 4 on the upper surface of the dielectric film layer 3, and a ground metal via 6 connecting the second metal layer 4, the first metal layer 5, the dielectric film layer 3 and the substrate layer 2.
[0023] Among them, GaAs process refers to a series of precision manufacturing technologies based on gallium arsenide (GaAs) semiconductor material to manufacture integrated circuits, optoelectronic devices and power devices. The filter provided in this embodiment of the invention includes a GaAs substrate layer to provide mechanical support and electrical insulation; the dielectric film layer is made of SiN material and is located above the substrate layer to isolate different conductive layers and form the required electromagnetic field distribution.
[0024] In this design, the first metal layer is embedded within the dielectric layer, and the second metal layer is located on the upper surface of the dielectric film. Both the first and second metal layers form the resonant structure of the filter and are used to adjust the filter's frequency selectivity.
[0025] Among them, the grounding metal via is a component that runs through the entire structure, used to connect the layers to provide a good grounding path and improve the performance of the filter.
[0026] The broadband bandpass filter provided in this embodiment of the invention allows for adjustment of the geometric parameters of the second metal layer, such as its shape, size, or relative position. Simultaneously, the geometric parameters of the first metal layer, in conjunction with those of the second metal layer, can be designed to be adjustable or non-adjustable according to actual needs, thereby ultimately adjusting the transmission zero position and center frequency of the filter to optimize frequency selection characteristics and adapt to different communication frequency band requirements.
[0027] As an example, see Figure 1 The structure shown in this embodiment of the invention employs a stacked structure using a 0.25μm GaAs process, including a GaAs substrate layer, a metal ground plane on the lower layer of the GaAs substrate layer, and a SiN dielectric film layer, a first metal layer M1, and a second metal layer M2 on the upper layer of the GaAs substrate layer; wherein, the first metal layer M1 is embedded in the SiN dielectric film layer, and the second metal layer M2 is on the upper surface of the SiN dielectric film layer.
[0028] The GaAs substrate layer can be set to a thickness of 100 μm and a relative permittivity of 12.9; the SiN dielectric film layer can be set to a thickness of 4.69 μm and a relative permittivity of 6.9; the first metal layer M1 can be set to a thickness of 1.065 μm, the second metal layer M2 can be set to a thickness of 3.5 μm, and the conductivity of both metal layers is 4 × 10⁻⁶. 7 S / m, both metal layers can be used for circuit implementation.
[0029] The broadband bandpass filter based on GaAs technology provided in this embodiment of the invention adopts GaAs technology and multi-layer structure design, which can achieve a wide operating bandwidth; while the multi-layer stacked structure is beneficial to reduce the filter size and facilitates integration in high-density RF front-ends. Stable filtering effect can be obtained by precisely controlling the metal layer parameters.
[0030] As one possible implementation, the first metal layer 5 and the second metal layer 4 have the same structure and equal geometric parameters; or, the first metal layer 5 and the second metal layer 4 have the same structure but different geometric parameters; or, the first metal layer 5 and the second metal layer 4 have different structures and different geometric parameters.
[0031] Specifically, the frequency selectivity of the filter is optimized by designing the specific structure and geometric parameters of each metal layer. See, as an example... Figure 2 The specific geometric structure of the metal layer can be composed of geometric shapes such as T-shaped strips and inverted T-shaped strips; geometric parameters include the gap distance between the feed line and the coupling line, the length of the T-shaped strip, etc.
[0032] As one possible implementation, the cross-section containing the central axis of the through-hole 60 is defined as the reference plane, and the second metal layer 4 includes: A pair of capacitively coupled feed lines 40 are distributed symmetrically with the reference plane as the symmetric plane. Each capacitively coupled feed line 40 includes a feed line 401 and a coupling line 402 with a gap between them, wherein the feed line 401 is located outside the coupling line 402. A pair of T-shaped strips 41 are symmetrically distributed on the inner side of a pair of capacitively coupled feed lines 40 with the reference plane as the symmetrical plane; the outward end of the head of each T-shaped strip 41 is connected to the corresponding coupling line 402, and the inward ends of the heads of the two T-shaped strips 41 are joined together. An inverted T-shaped strip 42 is located inside a pair of T-shaped strips 41, and the central section of the inverted T-shaped strip 42 is coplanar with the reference plane; there is a gap between the two ends of the head of the inverted T-shaped strip 42 and the coupling line 402 that is close to it, and the bottom end of the tail of the inverted T-shaped strip 42 is connected to the joint of the two T-shaped strips 41.
[0033] Among them, vias serve as electrical connection channels between different metal layers. Inserting grounding metal vias enables vertical connection between the first metal layer M1 and the second metal layer M2, ensuring good electrical connectivity between the metal layers. Secondly, vias connect the metal layers to the grounding metal vias, forming a complete grounding loop to ensure the stability of the filter.
[0034] Feed lines are critical transmission structures in microwave and radio frequency systems, used to transmit signals from one component to another. Their performance directly affects the transmission efficiency and frequency response characteristics of the entire system. Couplers are also critical transmission structures in microwave and radio frequency circuits, primarily used to achieve coupled signal transmission. In filter design, couplers are used in conjunction with feed lines, and the coupling strength can be adjusted by controlling the gap and geometric parameters between them.
[0035] Among them, the T-shaped strip and the inverted T-shaped strip are the shapes of the key distributed elements in the filter of the present invention, which are used to realize the design of a highly selective and compact bandpass filter. It consists of a main transmission line (vertical arm) and a transverse transmission line (horizontal arm) perpendicular to its end, and the whole is in the shape of "T". It is usually printed on a dielectric substrate to form a microstrip structure.
[0036] As an example, see Figure 2 The structure of the second metal layer is shown. In this embodiment, a low-loss broadband bandpass filter with a center frequency of 45.6 GHz was designed based on the second metal layer M2 using GaAs technology. The filter consists of a pair of capacitively coupled feed lines, a pair of T-shaped stripes, an inverted T-shaped stripe, and a grounding metal via.
[0037] Specifically, the cross-section containing the central axis of the through hole is defined as the reference plane; the distance between the location of the through hole and the horizontal arm of the T-shaped strip is s3; the central axis of the through hole is collinear with the connection line between the two horizontal arms of the T-shaped strip; and the half-width of the connection area where the location of the through hole and the horizontal arm meet is... w6; The feed line of the capacitively coupled feed line is L-shaped with a width of w2 and a vertical side length of l1; the coupling line of the capacitively coupled feed line has a width of w4 and a length of l2; the two capacitively coupled feed lines are symmetrically distributed with the reference plane as the symmetrical plane. Each capacitively coupled feed line includes a feed line and a coupling line with a gap between them. The feed line is located outside the coupling line, and the gap distance between the feed line and the coupling line is s1. Two T-shaped strips are symmetrically distributed on the inner side of a pair of capacitively coupled feed lines with the reference plane as the symmetrical plane. Each T-shaped strip has a horizontal arm half-arm length of l6, a vertical arm length of l3, and a width of w3. The total length of the horizontal arm is 2l6+w3. The outward-extending end of the head of each T-shaped strip is connected to its corresponding coupling line, and the inward-extending ends of the heads of the two T-shaped strips are joined together. The inverted T-shaped strip is located inside a pair of T-shaped strips, and the central section of the inverted T-shaped strip is coplanar with the reference plane. The vertical arm of the inverted T-shaped strip is l4 in length and w5 in width, the horizontal half-arm is l5 in length and w1 in width, and the total length of the horizontal arm is 2l5+w5. There is a gap between the two ends of the head of the inverted T-shaped strip and the coupling line that is close to it, and the gap distance is s2. The bottom end of the tail of the inverted T-shaped strip is connected to the joint of the two T-shaped strips.
[0038] The filter provided in this embodiment of the invention has a regular and compact arrangement of each structure, which reduces the manufacturing difficulty and effectively reduces the area, thus facilitating miniaturization and integration. By changing the geometric parameters of the second metal layer structure, the center frequency and transmission zero point can be flexibly designed without adding additional structures or components.
[0039] As one possible implementation, an LC equivalent circuit of a broadband bandpass filter is constructed. The relationship between the changes in inductance and capacitance in the LC equivalent circuit and the position of the transmission zero point and the center frequency is analyzed. The geometric parameters of the metal lines included in the capacitively coupled feed line, T-strip, and inverted T-strip are optimized. The geometric parameters include the length and width of each metal line and the spacing between adjacent metal lines.
[0040] Specifically, the filter structure in the second metal layer is transformed into an LC equivalent circuit. That is, the geometric parameters of the metal lines included in the capacitively coupled feed line, T-shaped strip and inverted T-shaped strip contained in the filter are transformed into an LC equivalent circuit. In order to analyze the relationship between the changes in inductance and capacitance in the LC equivalent circuit and the position of the transmission zero point and the center frequency, these geometric parameters are optimized.
[0041] As an example, see Figure 3 The circuit shown and Figure 2 The filter structure shown is as follows. Figure 2 The inverted T-shaped metal strip in the filter structure shown is equivalent to... Figure 3The LC resonant circuit shown consists of L6, 2C4, and 2C5. C4 is the key capacitor in the LC resonant circuit; its value directly changes the equivalent capacitance of the resonant system, thereby adjusting the resonant frequency and ultimately changing the center frequency of the filter. Furthermore, adjusting C4 does not affect the position of the transmission zero, allowing for precise fine-tuning of the center frequency while ensuring filter selectivity, thus adapting to design requirements.
[0042] As one possible implementation, the LC equivalent circuit can be constructed as follows: The feeder 40 is equivalent to a pair of inductors in series. L 4 and capacitor C 2; The capacitive coupling formed by the gap between each feed line 401 and its adjacent coupling line 402 is equivalent to a capacitor. C 1. Each capacitor C 1 is connected in series with an inductor. L 4 and capacitor C 2 in parallel; The pair of T-shaped strips 41 are equivalent to a pair of inductors L 1. Inductor L 2. Inductance L 5 and capacitor C A circuit consisting of 3 components; where the inductor... L 1 and inductor L 2. Series, Inductance L 5 and capacitor C 3. Series connection, series inductors L 1 and inductor L 2. Inductors in series L 5 and capacitor C 3 inductors connected in parallel and in series L 1 and inductor L 2 and capacitor C 1. Series connection; The inverted T-shaped strip 42 is equivalent to an inductor L 6. Capacitor 2 C 4 and capacitor 2 C A 5-element LC resonant circuit is formed, and the LC resonant circuit is connected in series with an inductor. L 5 and capacitor C 3 in parallel; The grounding metal via 6 is equivalent to an inductor. L 3. Inductance L 3 is connected in series with the LC resonant circuit.
[0043] As an example, see Figure 3 The circuit shown, Figure 3 The constructed circuit is Figure 2The LC equivalent circuit of the filter structure is shown. A metal strip of length l1 connected to the feed lines is equivalent to a series combination of inductor L4 and capacitor C2. A T-shaped metal strip is equivalent to three inductors L1, L2, and L5 and one capacitor C3. Furthermore, an inverted T-shaped metal strip is equivalent to an LC resonant circuit composed of L6, 2C4, and 2C5. Capacitive coupling between the capacitively coupled feed lines and the T-shaped metal strip, formed by a gap, is equivalent to capacitor C1. A grounding metal via is equivalent to an inductor L3.
[0044] The parameters of the LC equivalent circuit are: C1=995pF, C2=0.04pF, C3=1.6pF, C4=0.14pF, C5=17pF, L1=0.08nH, L2=0.03nH, L3=0.8nH, L4=0.16nH, L5=0.1nH, L6=0.1nH.
[0045] The center frequency of the filter can be changed by altering the value of capacitor C4. (See...) Figure 9 The test results shown demonstrate that increasing C4 will lower the center frequency of the filter.
[0046] As one possible implementation, the LC equivalent circuit is further equivalent to an odd-mode circuit and an even-mode circuit. Using the odd-mode / even-mode calculation method, the odd-mode input impedance and even-mode input impedance are calculated separately, further deriving the expression for the transmission zero point generated at the center frequency. The independent variable in the expression for the transmission zero point includes the series inductance equivalent to the feeder. L 4 and grounding capacitor C 2. The position of the transmission zero point is adjusted in the following way: Fixed grounding capacitor C 2. Adjust the inductance L 4. Change the position of the transmission zero point until the first preset position is reached, then fix the inductor. L 4. Change the grounding capacitance C 2. Fine-tune the position of the transmission zero point until it reaches the second preset position, so as to finally determine the inductance. L 4 and grounding capacitor C 2. Determine the length and width of the feeder.
[0047] Specifically, the position of the transmission zero point is adjusted by fixing the capacitor C2 and adjusting the inductor L4 according to specific needs. Since changing L4 can cause a significant change in the position of the transmission zero point, the capacitor C2 is fixed first, and the inductor L4 is changed to quickly and effectively adjust the position of the transmission zero point to the required position or range, such as to increase the roll-off rate of the filter and improve frequency selectivity.
[0048] Then fix inductor L4 and fine-tune capacitor C2 until the desired position or range is achieved. For example, adjust the transmission zero point to be close to the edge of the passband to increase the filter's roll-off rate and improve frequency selectivity. If there is fixed frequency band interference in the application scenario, the position of the transmission zero point can be precisely adjusted to that frequency to achieve deep suppression of interference signals.
[0049] As an example, such as Figure 6 As shown, the simulation S-parameters of the LC equivalent circuit are... Figure 1 The S-parameters of the structural model shown (the electromagnetic model obtained using full-wave simulation software) agree well, and both have three transmission poles and one transmission zero. Due to the symmetry of the proposed broadband bandpass filter structure, the circuit structure can be divided into two parts along the central plane, and the odd-even mode analysis method can be used for analysis. The corresponding odd-mode and even-mode equivalent circuits are shown in [reference 1]. Figure 4 and Figure 5 .
[0050] Among them, the odd-mode input impedance Z odd It can be represented as: Even-mode input impedance Z even It can be represented as: Where ω is the operating angular frequency and j is the imaginary unit.
[0051] According to Z odd and Z even The reflection coefficient S11 and transmission coefficient S21 of the bandpass filter were further calculated: Where Z0 is the characteristic impedance of the input / output port.
[0052] As one possible implementation, the expression for the transmission zero generated at the center frequency is: .
[0053] As an example, based on the impedance formula, by introducing the condition Zeven=Zodd for a transmission zero, and ignoring negative solutions, the formula for calculating the transmission zero at frequency f can be derived: As shown in the above formula, the position of the transmission zero point depends only on capacitor C2 and inductor L4. Therefore, to investigate the influence of capacitor C2 and inductor L4 on the position of the transmission zero point (i.e., whether they change with the same trend or with opposite trends), we first fix capacitor C2 and change inductor L4 to change the position of the transmission zero point. See [link to relevant documentation]. Figure 7It can be seen that when L4 increases from 135pH to 165pH, the position of the transmission zero point changes from 65.8GHz to 49.5GHz, showing an opposite trend. Subsequently, with inductor L4 fixed, the position of the transmission zero point is finely adjusted by changing capacitor C2. (See [reference needed]). Figure 8 It can be seen that when capacitor C2 is changed from 42.5fF to 44.5fF, the position of the transmission zero point changes from 61.8GHz to 60.4GHz, showing the opposite trend. By exploring the influence of inductance and capacitance on the trend of the zero point position change, a foundation is laid for subsequent center frequency adjustment.
[0054] As one possible implementation, this can be achieved by adjusting the capacitor. C 4. Adjust the center frequency position to the preset position. Based on this, determine the length and width of the tail of the inverted T-shaped strip, the length and width of the head, and the spacing between the T-shaped strip and the coupling line.
[0055] Specifically, adjusting the capacitor to achieve the desired center frequency position is crucial. Since the inverted T-shaped metal strip is equivalent to an LC resonant circuit composed of L6, 2C4, and 2C5, C4, as the key capacitor in the LC resonant circuit, directly alters the equivalent capacitance of the resonant system, thus adjusting the resonant frequency and ultimately changing the filter's center frequency. Therefore, adjusting C4 allows for precise fine-tuning of the center frequency while maintaining filter selectivity, without affecting the position of the transmission zero, to meet design requirements. See also... Figure 9 As shown, increasing C4 can lower the center frequency of the filter. Therefore, the value of C4 should be adjusted to achieve the designed center frequency.
[0056] After determining the center frequency, the geometric parameters of the second metal layer are optimized using an LC equivalent circuit: First, the design center frequency value is determined, and then adjusted using capacitor C4 to achieve this preset center frequency value. Once the preset center frequency value is reached, the inductance and capacitance of the equivalent circuit of the corresponding inverted T-shaped strip are also determined accordingly. Then, based on the determined inductance and capacitance, the geometric parameters of the inverted T-shaped strip are adjusted to meet the equivalent effect of the determined inductance and capacitance. For example, simulation software can be used to adjust each geometric parameter, and after achieving the preset effect, the corresponding filter structure can be manufactured based on the simulation results.
[0057] As an example, the geometric parameters of the second metal layer M2 are optimized using an LC equivalent circuit model when the filter's center frequency is 45.6 GHz. Figure 2The geometric parameters of the second metal layer filter structure shown are specifically optimized as follows: l1=336μm, l2=300μm, l3=210μm, l4=275μm, l5=160μm, l6=66μm, w1=15μm, w2=10μm, w3=15μm, w4=10μm, w5=30μm, w6=50μm, s1=7μm, s2=86μm, s3=17μm.
[0058] As one possible implementation, the substrate layer has a thickness of 100 μm and a relative permittivity of 12.9; The dielectric film has a thickness of 4.69 μm and a relative permittivity of 6.9; The thickness of the first metal layer is 1.065 μm, and its conductivity is 4 × 10⁻⁶. 7 S / m; the second metal layer has a thickness of 3.5 μm and a conductivity of 4 × 10⁻⁶. 7 S / m.
[0059] As an example, this embodiment fabricates an on-chip broadband bandpass filter prototype using a 0.25μm GaAs process. The filter substrate has a thickness of 100μm and a relative permittivity of 12.9; the dielectric film has a thickness of 4.69μm and a relative permittivity of 6.9; and the first metal layer has a thickness of 1.065μm and a conductivity of 4×10⁻⁶. 7 S / m; the second metal layer has a thickness of 3.5 μm and a conductivity of 4 × 10⁻⁶. 7 S / m.
[0060] The filter was tested using a GSG probe and a vector network analyzer. The test results for the on-chip filter's reflection coefficient / transmission coefficient are shown below. Figure 10 As shown, the size of the filter without the feed line is 418×405μm².
[0061] This invention presents a prototype on-chip broadband bandpass filter fabricated using a 0.25 μm GaAs process. The GaAs substrate of this filter has a thickness of 100 μm and a relative permittivity of 12.9; the SiN dielectric film has a thickness of 4.69 μm and a relative permittivity of 6.9; metal layer M1 has a thickness of 1.065 μm, and metal layer M2 has a thickness of 3.5 μm. The conductivity of both metal layers is 4 × 10⁻⁶. 7 S / m; The structure of its second metal layer is shown in the figure. Figure 2The specific geometric parameters are: l1=336μm, l2=300μm, l3=210μm, l4=275μm, l5=160μm, l6=66μm, w1=15μm, w2=10μm, w3=15μm, w4=10μm, w5=30μm, w6=50μm, s1=7μm, s2=86μm, s3=17μm.
[0062] The structure and geometric parameters of its first metal layer are the same as those of its second metal layer.
[0063] The filter was tested using a GSG probe and a vector network analyzer. The on-chip filter is as follows: Figure 10 As shown in the illustration, the dimensions without the feed line are 418 × 405 μm². Figure 10 As shown, the measured results of the filter's reflection coefficient / transmission coefficient are in good agreement with the simulation results.
[0064] Test results show that the filter provided in this embodiment of the invention has a center frequency of 45.6 GHz, a 3dB fractional bandwidth of 42.1%, an in-band insertion loss of 1.1 dB, and a size of 0.0039λ0². Insertion loss is an important indicator of filter performance, representing the power loss of a signal passing through the filter. In microwave filter design, insertion loss is usually expressed in dB; a smaller value indicates better filter performance.
[0065] The results demonstrate that the filter proposed in this invention achieves both wide bandwidth and compact size while exhibiting a lower level of in-band insertion loss.
[0066] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings, disclosure, and other materials. In this specification, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple components. A single processor or other unit can implement several functions listed in the specification. While certain measures are described in different embodiments, this does not mean that these measures cannot be combined to produce good results.
[0067] Although the invention has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made therein without departing from the spirit and scope of the invention. Accordingly, this specification and drawings are merely illustrative of the invention and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if such modifications and modifications fall within the scope of the invention and its equivalents, the invention is also intended to include such modifications and modifications.
Claims
1. A broadband bandpass filter based on GaAs technology, characterized in that, From bottom to top, it includes a metal ground plane, a substrate layer and a dielectric film layer, a first metal layer embedded in the dielectric film layer and a second metal layer on the upper surface of the dielectric film layer, and a ground metal via connecting the second metal layer, the first metal layer, the dielectric film layer and the substrate layer.
2. The broadband bandpass filter based on GaAs technology according to claim 1, characterized in that, The first metal layer and the second metal layer have the same structure and equal geometric parameters; or, the first metal layer and the second metal layer have the same structure but different geometric parameters. Alternatively, the first metal layer and the second metal layer may have different structures and different geometric parameters.
3. The broadband bandpass filter based on GaAs technology according to claim 1, characterized in that, Define the cross-section containing the central axis of the through hole as the reference plane. The second metal layer includes: A pair of capacitively coupled feed lines are distributed symmetrically with the reference plane as the symmetric plane. Each capacitively coupled feed line includes a feed line and a coupling line with a gap between them, wherein the feed line is located outside the coupling line. A pair of T-shaped strips are symmetrically distributed on the inner side of a pair of capacitively coupled feed lines with the reference plane as the symmetrical plane; the outward-extending end of the head of each T-shaped strip is connected to its corresponding coupling line, and the inward-extending ends of the heads of the two T-shaped strips are joined together. An inverted T-shaped strip is located inside a pair of T-shaped strips, and the central section of the inverted T-shaped strip is coplanar with the reference plane; there are gaps between the two ends of the head of the inverted T-shaped strip and the coupling line adjacent to it, and the bottom end of the tail of the inverted T-shaped strip is connected to the joint of the two T-shaped strips.
4. The broadband bandpass filter based on GaAs technology according to claim 3, characterized in that, Construct the LC equivalent circuit of a broadband bandpass filter, analyze the relationship between the changes in inductance and capacitance in the LC equivalent circuit and the position of the transmission zero point and the center frequency, and optimize the geometric parameters of the metal lines included in the capacitively coupled feed line, T-strip and inverted T-strip. The geometric parameters include the length and width of each metal line and the spacing between adjacent metal lines.
5. The broadband bandpass filter based on GaAs technology according to claim 4, characterized in that, The LC equivalent circuit is constructed as follows: The feeder is equivalent to a pair of inductors in series. L 4 and capacitor C 2; The capacitive coupling formed by the gap between each feed line and its adjacent coupling line is equivalent to a capacitor. C 1. Each capacitor C 1 is connected in series with an inductor. L 4 and capacitor C 2 in parallel; A pair of T-shaped strips can be equated to a pair of inductors. L 1. Inductor L 2. Inductance L 5 and capacitor C A circuit consisting of 3 components; where the inductor... L 1 and inductor L 2. Series, Inductance L 5 and capacitor C 3. Series connection, series inductors L 1 and inductor L 2. Inductors in series L 5 and capacitor C 3 inductors connected in parallel and in series L 1 and inductor L 2 and capacitor C 1. Series connection; The inverted T-shaped strip is equivalent to an inductor L 6. Capacitor 2 C 4 and capacitor 2 C A 5-element LC resonant circuit is formed, and the LC resonant circuit is connected in series with an inductor. L 5 and capacitor C 3 in parallel; The grounding metal via is equivalent to an inductor. L 3. Inductance L 3 is connected in series with the LC resonant circuit.
6. The broadband bandpass filter based on GaAs technology according to claim 5, characterized in that, The LC equivalent circuit is further equivalent to odd-mode and even-mode circuits. Using odd-mode and even-mode calculation methods, the odd-mode and even-mode input impedances are calculated separately. This leads to the derivation of an expression for the transmission zero at frequency f, where the independent variable in the expression for the transmission zero includes inductance. L 4 and capacitor C 2. The position of the transmission zero point is adjusted in the following way: Fixed grounding capacitor C 2. Adjust the inductance L 4. Change the position of the transmission zero point until the first preset position is reached, then fix the inductor. L 4. Change the grounding capacitance C 2. Fine-tune the position of the transmission zero point until it reaches the second preset position, so as to finally determine the inductance. L 4 and grounding capacitor C 2. Determine the length and width of the feeder.
7. The broadband bandpass filter based on GaAs technology according to claim 6, characterized in that, The expression for generating a transmission zero at frequency f is: 。 8. The broadband bandpass filter based on GaAs technology according to claim 5, characterized in that, By adjusting the capacitor C 4. Adjust the center frequency position to the preset position. Based on this, determine the length and width of the tail of the inverted T-shaped strip, the length and width of the head, and the spacing between the T-shaped strip and the coupling line.
9. The broadband bandpass filter based on GaAs technology according to claim 1, characterized in that, The substrate layer has a thickness of 100 μm and a relative permittivity of 12.9; The dielectric film has a thickness of 4.69 μm and a relative permittivity of 6.9; The thickness of the first metal layer is 1.065 μm, and its conductivity is 4 × 10⁻⁶. 7 S / m; the second metal layer has a thickness of 3.5 μm and a conductivity of 4 × 10⁻⁶. 7 S / m.