Microstrip filter
By designing a microstrip line structure in a microstrip filter, the problems of power imbalance and impedance mismatch when the filter is connected to a high load are solved, achieving stable transmission of high-power signals and reducing heat loss of the system, which is suitable for long-distance communication of unmanned agricultural machinery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HEILONGJIANG HUIDA TECHNOLOGY CO LTD
- Filing Date
- 2024-01-10
- Publication Date
- 2026-06-26
AI Technical Summary
When a filter is connected to a high-load device, the signal power at the input and output terminals is uneven, which leads to unstable system performance. Furthermore, impedance mismatch can cause self-oscillation and heat loss.
A microstrip filter was designed, which adopts a microstrip line structure set on a dielectric substrate, including the first to seventh microstrip lines. Through the combination of hairpin structure and open stub, good impedance matching between the signal input and output ends is achieved, reducing self-oscillation effect and improving system stability.
It achieves high-power signal transmission at both the input and output ends, reduces heat loss, improves system stability and current carrying capacity, and is suitable for long-distance communication of unmanned agricultural machinery.
Smart Images
Figure CN117712651B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of filters, and more particularly to a microstrip filter. Background Technology
[0002] In the field of wireless communication, information transmission between various wireless devices relies on radio waves. In order to prevent information interference, multiple devices can be set to different operating frequency bands. Therefore, filters are needed to filter out other noise outside the required frequency band so that the signal wave passing through the filter is the signal wave of the required frequency band.
[0003] However, when a filter is connected to a high-load device, the signal power at its input and output terminals is different, which leads to unstable system performance; and impedance mismatch between the input and output terminals can cause self-oscillation, resulting in excessive heat loss. Summary of the Invention
[0004] This application provides a microstrip filter whose signal transmission port has good impedance matching characteristics, thereby enabling its input and output terminals to withstand high-power electrical signal input and output.
[0005] In a first aspect, a microstrip filter is provided. The microstrip filter includes a dielectric substrate on which a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a fifth microstrip line, a sixth microstrip line, and a seventh microstrip line are disposed.
[0006] One end of the first microstrip line is connected to the signal input terminal, and the other end is connected in parallel to the second microstrip line.
[0007] One end of the second microstrip line is connected in parallel with the first microstrip line, and the other end is connected in parallel with the fourth microstrip line. The second microstrip line constitutes the first resonator, which is a hairpin structure.
[0008] The third microstrip line forms an open-circuit stub structure. The length of the third microstrip line is perpendicular to the second and fourth microstrip lines, and it is connected in parallel with the second and fourth microstrip lines.
[0009] One end of the fourth microstrip line is connected in parallel to the second microstrip line, and the other end is connected in perpendicular to the sixth microstrip line. The fourth microstrip line constitutes the second resonator, which is a hairpin structure.
[0010] One end of the fifth microstrip line is open, and the other end is connected perpendicularly to the fourth microstrip line, thus forming an open stub.
[0011] One end of the sixth microstrip line is perpendicularly connected to the fourth microstrip line, and the other end is parallel to the seventh microstrip line.
[0012] One end of the seventh microstrip line is connected in parallel to the sixth microstrip line, and the other end is connected to the signal output terminal.
[0013] The signal input terminal is the signal input terminal of the microstrip filter, and the signal output terminal is the signal output terminal of the microstrip filter.
[0014] In conjunction with the first aspect, in some implementations of the first aspect, the hairpin structure of the first resonator formed by the second microstrip line includes an open end and a turning end, and the longitudinal dimension of the first resonator is greater than the transverse dimension.
[0015] In conjunction with the first aspect, in some implementations of the first aspect, the open end of the hairpin structure of the first resonator is formed by an input end bend and an output end bend with opposite bending directions, and the turning end of the hairpin structure of the first resonator is formed by two bends of the second microstrip line near the center, with the two bends having opposite bending directions and being mirror symmetrical; the open end and the turning end of the hairpin structure of the first resonator are parallel to the first microstrip line, and the open end and the turning end of the hairpin structure of the first resonator are located on the same vertical line.
[0016] In conjunction with the first aspect, in some implementations of the first aspect, the input terminal is bent at the connection port between the second microstrip line and the first microstrip line, and the output terminal is bent at the connection port between the second microstrip line and the fourth microstrip line; the bending of the input terminal and the bending of the output terminal are not flush.
[0017] In conjunction with the first aspect, in some implementations of the first aspect, the second microstrip line is a low-impedance line.
[0018] In conjunction with the first aspect, in some implementations of the first aspect, the length of the open stub structure formed by the third microstrip line is 1 / 4 of the dielectric wavelength corresponding to the parasitic passband frequency.
[0019] In conjunction with the first aspect, in some implementations of the first aspect, the hairpin structure of the second resonator formed by the fourth microstrip line includes an open end and a turning end, and the longitudinal dimension of the second resonator is greater than the transverse dimension.
[0020] In conjunction with the first aspect, in some implementations of the first aspect, the open end of the hairpin structure of the second resonator is composed of two bends with opposite bending directions and radial symmetry, and the turning end of the hairpin structure of the second resonator is composed of two bends with opposite bending directions and mirror symmetry, located near the center of the fourth microstrip line; the open end and the turning end of the hairpin structure of the second resonator are parallel to the first microstrip line, and the open end and the turning end of the hairpin structure of the second resonator are located on the same vertical line.
[0021] In conjunction with the first aspect, in some implementations of the first aspect, the fourth microstrip line is a high-impedance line.
[0022] In conjunction with the first aspect, in some implementations of the first aspect, the opening stub of the fifth microstrip line is a serpentine structure, which is composed of multiple hairpin structures. The hairpin structure of the serpentine structure includes a turning end and an opening end, and the longitudinal dimension of the hairpin structure of the serpentine structure is greater than the transverse dimension.
[0023] In conjunction with the first aspect, in some implementations of the first aspect, the open end of the hairpin structure of the serpentine structure is composed of two bends with opposite bending directions, or is composed of one bend and an open path; the turning end of the hairpin structure of the serpentine structure is composed of two bends with opposite bending directions and mirror symmetry; the open end and turning end of the hairpin structure belonging to the same serpentine structure are parallel and located on the same vertical line; the open end and turning end of the hairpin structure of adjacent serpentine structures are located on the same horizontal line.
[0024] In conjunction with the first aspect, in some implementations of the first aspect, the serpentine structure consists of five hairpin structures, each comprising five turning ends and five opening ends.
[0025] In conjunction with the first aspect, in some implementations of the first aspect, the sixth microstrip line has a bend at the output end of the turning signal near the center, and the bend at the output end constitutes a turning angle.
[0026] In conjunction with the first aspect, in some implementations of the first aspect, the dielectric substrate is a dielectric substrate of a printed circuit board, the dielectric substrate is made of insulating and heat-insulating material, and the dielectric substrate has good bending resistance.
[0027] In conjunction with the first aspect, in some implementations of the first aspect, the length of the first microstrip line is 4.00 mm and the width is 1.63 mm; the length of the second microstrip line is 127.88 mm and the width is 5.98 mm; the length of the third microstrip line is 57.24 mm and the width is 10.00 mm; the length of the fourth microstrip line is 29.34 mm and the width is 1.21 mm; the length of the fifth microstrip line is 83.63 mm and the width is 1.00 mm; the length of the sixth microstrip line is 7.68 mm and the width is 1.00 mm; and the length of the seventh microstrip line is 4.00 mm and the width is 1.63 mm.
[0028] In conjunction with the first aspect, in some implementations of the first aspect, the microstrip filter is a 7th-order Butterworth low-frequency filter, and the microstrip line of the microstrip filter is made of a metal thin film.
[0029] In conjunction with the first aspect, in some implementations of the first aspect, the cutoff frequency of the microstrip filter is 433 MHz, the frequency range of the microstrip filter is 400 MHz-433 MHz, the maximum passband attenuation of the microstrip filter is 0.5 dB, and the minimum power of the microstrip filter is 35 watts.
[0030] In conjunction with the first aspect, in some implementations of the first aspect, the microstrip filter is large, with a size of 98.5 mm × 71.0 mm, or the microstrip filter is medium-sized, with a size of 61.8 mm × 70.4 mm, or the microstrip filter is small, with a size of 59.0 mm × 53.0 mm.
[0031] The signal transmission port of the aforementioned microstrip filter is connected to the resonator via a microstrip line. This microstrip line has good impedance matching characteristics with the signal transmission port, thus giving the microstrip line good current carrying capacity. When the signal power flowing through the signal transmission port is large, high-power signals can be transmitted through this microstrip line. That is, transmitting electrical signals through a microstrip line with good impedance matching characteristics avoids the self-excitation effect at the signal transmission port, thereby reducing the system's heat loss and increasing the system's stability. This allows the output of the microstrip filter to transmit high-power electrical signals.
[0032] Secondly, an unmanned agricultural machine is provided, including the microstrip filter in the first aspect or any possible implementation thereof.
[0033] Microstrip filters transmit electrical energy to the signal transmission port through microstrip lines with good impedance matching characteristics, which can avoid the self-excitation effect of the signal transmission port and improve the heat dissipation problem caused by the self-excitation effect. This enables the microstrip filter to withstand the transmission of signals with higher power, and can achieve high-gain output in the field of agricultural autonomous driving, such as the self-built station of unmanned agricultural machinery, to achieve the purpose of long-distance communication. This is beneficial for high-precision operations in agriculture in remote suburbs without signal. Attached Figure Description
[0034] Figure 1 A schematic block diagram of the microstrip filter provided in this application.
[0035] Figure reference numerals: 10-microstrip filter, 101-first microstrip line, 102-second microstrip line, 103-third microstrip line, 104-fourth microstrip line, 105-fifth microstrip line, 106-sixth microstrip line, 107-seventh microstrip line, 110-dielectric plate. Detailed Implementation
[0036] In the description of the embodiments of this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be a single item or multiple items.
[0037] The use of prefixes such as "first" and "second" in this application embodiment is solely for distinguishing different descriptive objects and does not limit the position, order, priority, quantity, or content of the described objects. The use of ordinal numbers and other prefixes to distinguish descriptive objects in this application embodiment does not constitute a limitation on the described objects. The description of the described objects is found in the claims or the context of the embodiments, and the use of such prefixes should not constitute unnecessary restrictions.
[0038] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.
[0039] In the field of wireless communication, information transmission between various wireless devices relies on radio waves. In order to prevent information interference, multiple devices can be set to different operating frequency bands. Therefore, filters are needed to filter out other noise outside the required frequency band so that the signal wave passing through the filter is the signal wave of the required frequency band.
[0040] However, when a filter is connected to high-load, high-power devices, the difference in signal power that its input and output terminals can handle can cause the filter to be unable to transmit high-power signals, leading to system instability. Furthermore, impedance mismatch between the filter's input and output terminals can cause self-oscillation, resulting in excessive heat loss.
[0041] In microwave integrated circuits, microstrip lines are widely used as transmission lines. They can be connected to other devices, allowing for flexible structural designs, and microstrip patch resonators can be used to design filters. A stepped impedance resonator (SIR) is a resonator composed of two or more transmission lines with different characteristic impedances. Its geometry is varied and can be flexibly combined, giving it freedom in structural and performance design.
[0042] Therefore, to address the above problems, this application proposes a microstrip filter. For example... Figure 1 As shown, the microstrip filter 10 includes a dielectric substrate 110, on the surface of which a first microstrip line 101, a second microstrip line 102, a third microstrip line 103, a fourth microstrip line 104, a fifth microstrip line 105, a sixth microstrip line 106, and a seventh microstrip line 107 are disposed.
[0043] The microstrip filter 10 can be made by electronic printing on a printed circuit board (PCB). There is a thin metal film on the surface of the circuit board. The lines obtained after etching during the manufacturing process are used to provide circuit connections for the components on the PCB.
[0044] One end of the first microstrip line 101 is connected to the signal input terminal, and the other end is connected in parallel to the second microstrip line 102. One end of the second microstrip line 102 is connected in parallel to the first microstrip line 101, and the other end is connected in parallel to the fourth microstrip line 104. The second microstrip line 102 constitutes a first resonator, which is a hairpin structure. The third microstrip line 103 constitutes an open-circuit stub structure. The length of the third microstrip line 103 is perpendicular to the second microstrip line 102 and the fourth microstrip line 104, and it is connected in parallel with the second microstrip line 102 and the fourth microstrip line 104. One end of the fourth microstrip line 104 is connected in parallel to the second microstrip line 102, and the other end is connected perpendicularly to the sixth microstrip line 106. The fourth microstrip line 104 constitutes a second resonator, which is also a hairpin structure. One end of the fifth microstrip line 105 is open-circuited, and the other end is connected perpendicularly to the fourth microstrip line 104, thus forming an open stub. One end of the sixth microstrip line 106 is perpendicularly connected to the fourth microstrip line 104, and the other end is parallel to the seventh microstrip line 107. One end of the seventh microstrip line 107 is parallel to the sixth microstrip line 106, and the other end is connected to the signal output terminal.
[0045] The microstrip filter 10 has a simple structure, which can reduce the cost of the filter and facilitate miniaturization design.
[0046] The dielectric substrate 110 is a dielectric substrate for a printed circuit board and can be made of high-frequency, high-dielectric materials such as ceramics. It has good bending resistance and circuits can be formed on its surface according to a predetermined design.
[0047] The signal input terminal connected to the first microstrip line 101 is the signal input terminal of the filter, and the signal wave containing clutter is transmitted from the signal input terminal to the filter.
[0048] The first microstrip line 101 has a length of 4.00 mm and a width of 1.63 mm.
[0049] The first microstrip line 101 has good impedance matching characteristics with the signal input terminal, thereby increasing the current carrying capacity of the first microstrip line 101.
[0050] The second microstrip line 102 constitutes the first resonator, and the hairpin structure of the first resonator includes an open end and a turning end.
[0051] The hairpin structure of the first resonator has an open end formed by an input end bend and an output end bend with opposite bending directions. The turning end of the hairpin structure of the first resonator is formed by two bends of the second microstrip line 102 near the center. The two bends have opposite bending directions and are mirror symmetrical. The open end and the turning end of the hairpin structure of the first resonator are parallel to the first microstrip line 101, and the open end and the turning end of the hairpin structure of the first resonator are located on the same vertical line.
[0052] The input end of the first resonator is bent at the connection port between the second microstrip line 102 and the first microstrip line 101, and the output end is bent at the connection port between the second microstrip line 102 and the fourth microstrip line 104; the bends at the input end and the output end are not flush.
[0053] The second microstrip line 102 is a low-impedance line.
[0054] The second microstrip line 102 bends at its connection ports with the first microstrip line 101 and the fourth microstrip line 104. The bend at the connection port between the second microstrip line 102 and the first microstrip line 101 is an input bend. The bend at the connection port between the second microstrip line 102 and the fourth microstrip line 104 is an output bend. The bending directions at the input and output ends are opposite, thus forming an open end. The second microstrip line 102 has two mirror-symmetrical bends in opposite directions near its center, thus forming a turning end.
[0055] The input bend and the output bend may or may not be flush. That is, the input bend and the output bend may not be on the same horizontal line, or they may be on the same horizontal line.
[0056] The second microstrip line 102 has a length of 127.88 mm and a width of 5.98 mm.
[0057] The first resonator, formed by the hairpin structure of the second microstrip line 102, is used to filter clutter, thereby improving the performance of the microstrip filter 10.
[0058] The second microstrip line 102 is connected to the signal input terminal via the first microstrip line 101. The first microstrip line 101 has good impedance matching characteristics with the signal input terminal, thereby increasing the current carrying capacity of the first microstrip line 101. When the signal power input to the signal input terminal is large, the high-power signal input to the signal input terminal is transmitted through the first microstrip line 101. That is, the electrical signal of the signal input terminal is transmitted through the first microstrip line 101 with good impedance matching characteristics, avoiding the self-excitation effect at the signal input terminal, thereby reducing the heat loss of the system and increasing the stability of the system, enabling the input terminal of the microstrip filter 10 to transmit a large-power electrical signal.
[0059] The length of the open stub structure formed by the third microstrip line 103 can be 1 / 4 of the dielectric wavelength corresponding to the parasitic passband frequency.
[0060] The third microstrip line 103 has a length of 57.24 mm and a width of 10 mm.
[0061] When the impedances of the microstrip lines connected to the two ends of the third microstrip line 103 are different, the stub microstrip line structure formed by the third microstrip line 103 can match microstrip lines with different impedances, thus making the design of the microstrip filter 10 flexible and versatile.
[0062] The hairpin structure of the second resonator formed by the fourth microstrip line 104 includes an open end and a turning end, and the longitudinal dimension of the second resonator is larger than the transverse dimension.
[0063] The opening end of the hairpin structure of the second resonator is formed by two bends with opposite bending directions and mirror symmetry. The turning end of the hairpin structure of the second resonator is formed by two bends with opposite bending directions and mirror symmetry, located near the center of the fourth microstrip line 104. The opening end and the turning end of the hairpin structure of the second resonator are parallel to the first microstrip line 101, and the opening end and the turning end of the hairpin structure of the second resonator are located on the same vertical line.
[0064] The fourth microstrip line, 104, is a high-impedance line.
[0065] The fourth microstrip line 104 bends at the connection ports with the second microstrip line 102 and the sixth microstrip line 106. The two bends are in opposite directions and mirror-symmetrical, thus forming an open end. The fourth microstrip line 104 has two mirror-symmetrical bends in opposite directions near the center, thus forming a turning end.
[0066] The fourth microstrip line 104 has a length of 29.34 mm and a width of 1.21 mm.
[0067] The hairpin structure of the fourth microstrip line 104 constitutes the second resonator. The electrical signal output from the input end flows out of the second microstrip line 102 and is filtered. By placing the fourth microstrip line 104 after the second microstrip line 102, noise can be further filtered, thus improving the performance of the microstrip filter 10.
[0068] The opening stub of the fifth microstrip line 105 is a serpentine structure, which can be regarded as being composed of multiple hairpin structures. The hairpin structure of the serpentine structure includes a turning end and an opening end. The longitudinal dimension of the hairpin structure of the serpentine structure is greater than the transverse dimension.
[0069] The opening end of a serpentine hairpin structure is formed by two bends in opposite directions, or by one bend and an open path; the turning end of a serpentine hairpin structure is formed by two bends in opposite directions and mirror-symmetrical; the opening end and turning end of a hairpin structure belonging to the same serpentine structure are parallel and located on the same vertical line; the opening end and turning end of adjacent serpentine hairpin structures are located on the same horizontal line.
[0070] The serpentine structure can be viewed as consisting of five hairpin structures, including five bends and five open ends.
[0071] The hairpin structure of this serpentine structure is similar to the hairpin structure of the fourth microstrip line 104 mentioned above.
[0072] The fifth microstrip line 105 has a length of 83.63 mm and a width of 1.00 mm.
[0073] The hairpin structure of the fifth microstrip line 105 forms a fifth-order resonator, which improves the performance of the microstrip filter 10. The open stub formed by its vertical connection with the fourth microstrip line 104 reduces the complexity of the microstrip filter 10, thereby reducing the cost of the microstrip filter 10.
[0074] The sixth microstrip line 106 has a bend at the turn signal output end near the center, thus forming a turning angle.
[0075] The sixth microstrip line 106 has a length of 7.68 mm and a width of 1.00 mm.
[0076] The desired frequency band signal wave, which has been filtered of noise by the filter, can flow out of the filter from the signal output terminal connected to the seventh microstrip line 107.
[0077] The seventh microstrip line 107 has a length of 4.00 mm and a width of 1.63 mm.
[0078] The seventh microstrip line 107 has good impedance matching characteristics with the signal output terminal, thereby increasing the current carrying capacity of the seventh microstrip line 107.
[0079] The sixth microstrip line 106 is connected to the signal output terminal via a seventh microstrip line 107. The seventh microstrip line 107 has good impedance matching characteristics with the signal output terminal, thus giving it good current-carrying capacity. When the signal power output from the signal output terminal is large, the high-power signal output from the signal output terminal is transmitted through the seventh microstrip line 107. That is, the electrical signal from the signal input terminal is transmitted through the seventh microstrip line 107 with good impedance matching characteristics, avoiding the self-excitation effect at the signal output terminal, thereby reducing the heat loss of the system and increasing the stability of the system, enabling the output terminal of the microstrip filter 10 to transmit a large-power electrical signal.
[0080] As an example, the impedance at the signal input terminal is 50.00 ohms. When the first microstrip line 101 is connected to the second microstrip line 102, the impedance changes from 50.00 ohms to 19.60 ohms; when the second microstrip line 102 is connected to the third microstrip line 103, the impedance changes from 19.60 ohms to 12.73 ohms; when the second microstrip line 102 is connected to the fourth microstrip line 104, the impedance changes from 19.60 ohms to 59.40 ohms; when the fourth microstrip line 104 is connected to the fifth microstrip line 105, the impedance remains unchanged at 59.40 ohms; when the fourth microstrip line 104 is connected to the sixth microstrip line 106, the impedance changes from 59.40 ohms to 65.80 ohms; when the sixth microstrip line 106 is connected to the seventh microstrip line 107, the impedance changes from 65.8 ohms to 50.00 ohms.
[0081] The length and width of the microstrip line of the microstrip filter 10 are shown in Table 1:
[0082] Table 1 Dimensions of the microstrip line
[0083] Serial Number Length / mm Width / mm 101 4.00 1.63 102 127.88 5.98 103 57.24 10.00 104 29.34 1.21 105 83.63 1.00 106 7.68 1.00 107 4.00 1.63
[0084] The signal transmission port of the microstrip filter 10 in this embodiment is connected to the resonator via a microstrip line. The microstrip line and the signal transmission port have good impedance matching characteristics, which gives the microstrip line good current carrying capacity. When the signal power flowing through the signal transmission port is large, the high-power signal is transmitted through the microstrip line. That is, the electrical energy of the signal transmission port is transmitted through the microstrip line with good impedance matching characteristics, avoiding the self-excitation effect of the signal transmission port, thereby reducing the heat loss of the system and increasing the stability of the system, so that the output terminal of the microstrip filter 10 can transmit a large-power electrical signal.
[0085] The microstrip filter 10 is a 7th-order Butterworth low-frequency filter, and the microstrip line of the microstrip filter 10 can be made of metal thin film.
[0086] The microstrip filter 10 has a cutoff frequency of 433 MHz and a frequency range of 400-433 MHz. Its maximum passband attenuation is 0.5 dB, and its minimum power is 35 watts. The microstrip lines of the microstrip filter 10 can be fabricated using a thin metal film. The microstrip filter 10 can be large (98.5 mm × 71.0 mm), medium (61.8 mm × 70.4 mm), or small (59.0 mm × 53.0 mm).
[0087] In some embodiments, the filter can be applied in a power amplifier.
[0088] The power amplifier may include: a pre-stage filter, an input matching circuit, a bias circuit, a transistor, an output matching circuit, and a post-stage filter. The pre-stage filter is connected to the input matching circuit, the transistor is connected to the input matching circuit, the bias circuit, and the output matching circuit, and the output matching circuit is connected to the post-stage filter. The microstrip filter provided in this embodiment can be used as the post-stage filter.
[0089] The test results of the power amplifier using this microstrip filter are shown in Table 2:
[0090] Table 2 Test Results of Power Amplifiers
[0091]
[0092] For example, the target output power (output stage power) of the power amplifier is 35W (approximately 45.44 dBmW). To achieve the target output power, the output signal of the power amplifier can be amplified, such as through a gain stage (first-stage amplification) or a driver stage (second-stage amplification).
[0093] By amplifying the input signal of the power amplifier through a gain stage and a driver stage, the output power of the power amplifier with a microstrip filter is generally above 46 dBmW, which meets the target output power requirement. Furthermore, the power amplifier with a microstrip filter has a high signal-to-noise ratio, which reduces clutter generated when the output signal passes through the power amplifier, thereby reducing the impact of clutter on the effective signal.
[0094] In other words, the microstrip filter provided in this application embodiment can be applied to a power amplifier to reduce noise generated when a signal passes through the power amplifier, and at the same time enable the power amplifier to output a signal with higher power.
[0095] This application provides an unmanned agricultural machine, which includes a power amplifier or microstrip filter provided in this application.
[0096] The signal transmission port of the microstrip filter is connected to the resonator via a microstrip line. This microstrip line has excellent impedance matching characteristics with the signal transmission port, thus giving it good current-carrying capacity. When the signal power flowing through the signal transmission port is high, the high-power signal is transmitted through this microstrip line. By transmitting power to the signal transmission port through the microstrip line with good impedance matching characteristics, the microstrip filter avoids self-oscillation at the signal transmission port, improving heat dissipation problems caused by self-oscillation. This allows the microstrip filter to withstand high-power signal transmission, enabling high-gain output for self-built stations in agricultural autonomous driving applications, achieving long-distance communication, and facilitating high-precision operations in remote, signal-free agricultural settings.
[0097] In addition, the power amplifier included in this unmanned agricultural machine has a simple structure, which can reduce the cost of the drone and facilitate the miniaturization of the drone design.
[0098] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A microstrip filter, characterized in that, include: A dielectric substrate, wherein a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a fifth microstrip line, a sixth microstrip line, and a seventh microstrip line are disposed on the surface of the dielectric substrate; One end of the first microstrip line is connected to the signal input terminal, and the other end is connected in parallel to the second microstrip line. One end of the second microstrip line is connected in parallel to the first microstrip line, and the other end is connected in parallel to the fourth microstrip line. The second microstrip line constitutes the first resonator, and the first resonator is a hairpin structure. The third microstrip line forms an open-circuit stub structure. The length of the third microstrip line is perpendicular to the second microstrip line and the fourth microstrip line, and is connected in parallel with the second microstrip line and the fourth microstrip line. One end of the fourth microstrip line is connected in parallel to the second microstrip line, and the other end is connected in perpendicular to the sixth microstrip line. The fourth microstrip line constitutes a second resonator, and the second resonator is a hairpin structure. One end of the fifth microstrip line is open, and the other end is connected perpendicularly to the fourth microstrip line, thus forming an open branch; One end of the sixth microstrip line is perpendicularly connected to the fourth microstrip line, and the other end is parallel to the seventh microstrip line; One end of the seventh microstrip line is connected in parallel to the sixth microstrip line, and the other end is connected to the signal output terminal. The signal input terminal is the signal input terminal of the microstrip filter, and the signal output terminal is the signal output terminal of the microstrip filter.
2. The microstrip filter according to claim 1, characterized in that, The hairpin structure of the first resonator formed by the second microstrip line includes an open end and a turning end, and the longitudinal dimension of the first resonator is greater than the transverse dimension.
3. The microstrip filter according to claim 2, characterized in that, The hairpin structure of the first resonator has an open end formed by bends at the input end and the output end with opposite bending directions. The hairpin structure of the first resonator is formed by two bends of the second microstrip line near the center, and the two bends are in opposite directions and mirror-symmetrical. The open end and the turning end of the hairpin structure of the first resonator are parallel to the first microstrip line, and the open end and the turning end of the hairpin structure of the first resonator are located on the same vertical line.
4. The microstrip filter according to claim 3, characterized in that, The input terminal is bent at the connection port between the second microstrip line and the first microstrip line, and the output terminal is bent at the connection port between the second microstrip line and the fourth microstrip line; The input bend is not flush with the output bend.
5. The microstrip filter according to claim 2, characterized in that, The second microstrip line is a low-impedance line.
6. The microstrip filter according to claim 1, characterized in that, The length of the open stub structure formed by the third microstrip line is 1 / 4 of the dielectric wavelength corresponding to the parasitic passband frequency.
7. The microstrip filter according to claim 1, characterized in that, The hairpin structure of the second resonator formed by the fourth microstrip line includes an open end and a turning end, and the longitudinal dimension of the second resonator is greater than the transverse dimension.
8. The microstrip filter according to claim 7, characterized in that, The hairpin structure of the second resonator has an open end consisting of two bends with opposite bending directions and radial symmetry. The hairpin structure of the second resonator is composed of two bends that are close to the center of the fourth microstrip line, with opposite bending directions and mirror symmetry. The opening and turning ends of the hairpin structure of the second resonator are parallel to the first microstrip line, and the opening and turning ends of the hairpin structure of the second resonator are located on the same vertical line.
9. The microstrip filter according to claim 7 or 8, characterized in that, The fourth microstrip line is a high-impedance line.
10. The microstrip filter according to claim 1, characterized in that, The opening stub of the fifth microstrip line has a serpentine structure, which is composed of multiple hairpin structures. The hairpin structure of the serpentine structure includes a turning end and an opening end, and the longitudinal dimension of the hairpin structure of the serpentine structure is greater than the transverse dimension.
11. The microstrip filter according to claim 10, characterized in that, The open end of the hairpin structure in the serpentine shape is formed by two bends in opposite directions, or by one bend and an open path. The turning point of the serpentine hairpin structure is composed of two bends with opposite bending directions and mirror symmetry. The opening end and the turning end of the hairpin structure belonging to the same snake-shaped structure are parallel and located on the same vertical line; The opening end and turning end of the adjacent serpentine hairpin structure are located on the same horizontal line.
12. The microstrip filter according to claim 10 or 11, characterized in that, The serpentine structure consists of five hairpin structures, each comprising five bends and five open ends.
13. The microstrip filter according to claim 1, characterized in that, The sixth microstrip line has a bend near the center that turns towards the signal output terminal, and the bend at the output terminal forms a turning angle.
14. The microstrip filter according to claim 1, characterized in that, The dielectric substrate is a dielectric substrate for a printed circuit board. The dielectric substrate is made of insulating and heat-insulating materials and has good bending resistance.
15. The microstrip filter according to claim 1, characterized in that, The first microstrip line has a length of 4.00 mm and a width of 1.63 mm; The second microstrip line has a length of 127.88 mm and a width of 5.98 mm; The third microstrip line has a length of 57.24 mm and a width of 10.00 mm; The fourth microstrip line has a length of 29.34 mm and a width of 1.21 mm; The fifth microstrip line has a length of 83.63 mm and a width of 1.00 mm; The sixth microstrip line has a length of 7.68 mm and a width of 1.00 mm; The seventh microstrip line has a length of 4.00 mm and a width of 1.63 mm.
16. The microstrip filter according to claim 1, characterized in that, The microstrip filter is a 7th-order Butterworth low-frequency filter, and the microstrip lines of the microstrip filter are made of metal thin films.
17. The microstrip filter according to claim 1, characterized in that, The microstrip filter has a cutoff frequency of 433 MHz, a frequency range of 400-433 MHz, a maximum passband attenuation of 0.5 dB, and a minimum power of 35 watts.
18. The microstrip filter according to claim 1, characterized in that, The microstrip filter is large, with dimensions of 98.5 mm × 71.0 mm, or medium, with dimensions of 61.8 mm × 70.4 mm, or small, with dimensions of 59.0 mm × 53.0 mm.
19. An unmanned agricultural machine, characterized in that, Including the microstrip filter as described in any one of claims 1-18.