CN115529016A - High-rejection band-pass filter based on cascade structure - Google Patents
High-rejection band-pass filter based on cascade structure Download PDFInfo
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- CN115529016A CN115529016A CN202211259439.7A CN202211259439A CN115529016A CN 115529016 A CN115529016 A CN 115529016A CN 202211259439 A CN202211259439 A CN 202211259439A CN 115529016 A CN115529016 A CN 115529016A
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- pass filter
- capacitor
- band
- resonance unit
- rejection
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
- H03H7/01—Frequency selective two-port networks
- H03H7/0115—Frequency selective two-port networks comprising only inductors and capacitors
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- Power Engineering (AREA)
- Filters And Equalizers (AREA)
Abstract
The invention discloses a high-rejection band-pass filter based on a cascade structure. The filter is composed of a low-pass filter, a band-pass filter, an input port RFin and an output port RFout. The input signal enters the low-pass filter through the input port RFin, then passes through the band-pass filter, and finally is output through the output port RFout. The filter has the characteristics of low insertion loss and high out-of-band rejection.
Description
Technical Field
The invention belongs to the technical field of radio frequency integrated circuits.
Background
Filters are frequency selective filter devices that pass desired frequencies and attenuate and reject other unwanted and harmful frequencies. With the rapid development of radio frequency integrated circuits, communication devices put higher demands on the performance of filters, and the filters are required to have low insertion loss and high out-of-band rejection. Conventional filter structures are easy to implement radio frequency filters but have poor out-of-band rejection, especially at the third and fourth harmonics.
Disclosure of Invention
The purpose of the invention is as follows: in order to solve the problems in the prior art, the invention provides a high-rejection band-pass filter based on a cascade structure.
The technical scheme is as follows: the invention provides a high-rejection band-pass filter based on a cascade structure, which comprises a low-pass filter and a band-pass filter which are in cascade connection with each other.
Furthermore, the low-pass filter comprises a first resonance unit, a first capacitor and a second capacitor, one end of the first resonance unit is used as the input end of the whole high-rejection band-pass filter to receive radio-frequency signals and is connected with one end of the first capacitor, and the other end of the first capacitor is grounded; the other end of the first resonance unit is connected with the band-pass filter and one end of the second capacitor; the other end of the second capacitor is grounded.
Further, the band-pass filter comprises second to fifth resonance units and a third capacitor; one end of the second resonance unit is connected with the low-pass filter, the other end of the second resonance unit is connected with one end of the third resonance unit and one end of the fourth resonance unit, the other end of the fourth resonance unit is grounded, the other end of the third resonance unit is connected with one end of the fifth resonance unit and one end of the third capacitor, one end of the fifth resonance unit is grounded, and one end of the third capacitor is used as the output end of the whole high-suppression band-pass filter.
Further, the resonance unit is composed of a capacitor and an inductor which are connected in parallel.
Has the beneficial effects that: the filter improves the suppression of the third harmonic and the fourth harmonic, and meanwhile, the high-suppression band-pass filter has the advantages of low insertion loss and high out-of-band suppression.
Drawings
FIG. 1 is an overall topology of the present invention;
FIG. 2 is a simulation diagram of the present invention;
FIG. 3 is a simulation of an unsynchronized bandpass filter;
figure 4 is a graph comparing simulation results of the present invention with those of an unsynchronized bandpass filter.
Detailed Description
The accompanying drawings, which are included to provide a further understanding of the invention, illustrate embodiments of the invention and together with the description serve to explain the invention and do not constitute a limitation of the invention.
As shown in fig. 1, the present embodiment provides a high-rejection band-pass filter based on a cascade structure, which includes a low-pass filter, a band-pass filter, an input port RFin and an output port RFout, where the input port RFin receives a radio-frequency signal, the radio-frequency signal passes through the low-pass filter and the band-pass filter, and then is output from the output port RFout, the low-pass filter includes a first resonant unit 1, a first capacitor and a second capacitor, the band-pass filter includes a second resonant unit 2, a third resonant unit 3, a fourth resonant unit 4, a fifth resonant unit 5 and a third capacitor, the first resonant unit is connected to the input port RFin at one end, the other end is connected to the second resonant unit, the first capacitor is connected to the input port RFin at one end, the other end is connected to ground, the second capacitor is connected to the first resonant unit at one end, the other end is connected to ground, the third resonant unit is connected to the second resonant unit at one end, the other end is connected to one end of the third capacitor, the other end of the third capacitor is connected with the output port RFout, one end of the fourth resonance unit is connected with the ground, the other end of the fourth resonance unit is connected with the second resonance unit and the third resonance unit, one end of the fifth resonance unit is connected with the ground, the other end of the fifth resonance unit is connected with one end of the third resonance unit and one end of the capacitor, the resonance unit is formed by connecting the inductor and the capacitor in parallel, as shown in figure 1, the first resonance unit comprises an inductor L1 and a capacitor C1, one end of the inductor L1 and the capacitor C1 after being connected in parallel is connected with an input port RFin, the second resonance unit comprises an inductor L2 and a capacitor C2, one end of the inductor L2 and the capacitor C2 after being connected in parallel is connected with the other end of the inductor L1 and the capacitor C1 after being connected in parallel, the third resonance unit comprises an inductor L3 and a capacitor C3, one end of the inductor L3 and the capacitor C3 after being connected in parallel is connected with the other end of the inductor L2 and the capacitor C2 after being connected in parallel with the capacitor C4, the other end of the fifth resonance unit is grounded, the fifth resonance unit comprises an inductor L5 and a capacitor C5, one end of the inductor L5 and the capacitor C5 after being connected in parallel is connected with the other end of the inductor L3 and the capacitor C3 in parallel, the other end of the inductor L5 and the capacitor C5 is grounded, the first capacitor is connected with C6, one end of the first capacitor is grounded, the other end of the first capacitor is connected with an output port RFin, the second capacitor is C7, one end of the second capacitor is connected with the inductor L1, the other end of the first capacitor is grounded, the third capacitor is C8, one end of the third capacitor is connected with the other end of the inductor L3 and the capacitor C3 in parallel, and the other end of the third capacitor is connected with an output port RFout.
In the band-pass filter of the embodiment, the fourth resonance unit (4) and the fifth resonance unit (5) form transmission poles, the working frequency band of the filter is determined, the flatness in the band is enhanced, the second resonance unit (2) forms transmission zeros on one side of the high frequency of the pass band, the out-of-band rejection of the low frequency band is promoted, and the third resonance unit (3) forms transmission zeros on one side of the high frequency of the pass band, and the out-of-band rejection of the high frequency band is promoted. The low-pass filter is an elliptical low-pass filter, the first resonator element (1) forming a transmission zero at the third harmonic, enhancing the rejection of the filter at the third and fourth harmonics. The simulation result of the invention is shown in figure 2, the dotted line represents the return loss of the filter, the solid line represents the insertion loss of the filter, the working frequency band of the filter is 3.3GHz-4.2GHz, the insertion loss is 1.5dB, the inhibition at 2.4GHz is-20dB, the inhibition at DC-2.1GHz is less than-35dB, the inhibition at 5.15GH is-16 dB, the inhibition at the second harmonic is less than-33 dB, the inhibition at the third harmonic is less than-44 dB, the inhibition at the fourth harmonic is less than-43 dB, and the high inhibition on the third harmonic and the fourth harmonic is realized.
Fig. 3 shows simulation results of an unsynchronized bandpass filter, which shows poor suppression performance at high frequencies, especially at the third and fourth harmonics.
As shown in fig. 4, the black solid line and the dotted line are simulation results of the present invention, and the gray solid line and the dotted line are simulation results of the bandpass filter that is not cascaded, which has the following significant advantages compared with the prior art: the filter has an increased rejection of the third and fourth harmonics.
It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. The invention is not described in detail in order to avoid unnecessary repetition.
Claims (4)
1. A high-rejection band-pass filter based on a cascade structure is characterized by comprising a low-pass filter and a band-pass filter which are cascaded with each other.
2. The cascade structure-based high-rejection band-pass filter according to claim 1, wherein the low-pass filter includes a first resonant unit, a first capacitor and a second capacitor, one end of the first resonant unit is used as an input end of the whole high-rejection band-pass filter to receive a radio-frequency signal and is connected with one end of the first capacitor, and the other end of the first capacitor is grounded; the other end of the first resonance unit is connected with the band-pass filter and one end of the second capacitor; the other end of the second capacitor is grounded.
3. The high-rejection band-pass filter based on the cascade structure as claimed in claim 1, wherein the band-pass filter comprises second to fifth resonant units and a third capacitor; one end of the second resonance unit is connected with the low-pass filter, the other end of the second resonance unit is connected with one end of the third resonance unit and one end of the fourth resonance unit, the other end of the fourth resonance unit is grounded, the other end of the third resonance unit is connected with one end of the fifth resonance unit and one end of the third capacitor, one end of the fifth resonance unit is grounded, and one end of the third capacitor is used as the output end of the whole high-suppression band-pass filter.
4. A high-rejection band-pass filter based on a cascade structure according to any one of claims 2 and 3, wherein the resonance unit is composed of a capacitor and an inductor connected in parallel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211259439.7A CN115529016A (en) | 2022-10-14 | 2022-10-14 | High-rejection band-pass filter based on cascade structure |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211259439.7A CN115529016A (en) | 2022-10-14 | 2022-10-14 | High-rejection band-pass filter based on cascade structure |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN115529016A true CN115529016A (en) | 2022-12-27 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211259439.7A Pending CN115529016A (en) | 2022-10-14 | 2022-10-14 | High-rejection band-pass filter based on cascade structure |
Country Status (1)
| Country | Link |
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| CN (1) | CN115529016A (en) |
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2022
- 2022-10-14 CN CN202211259439.7A patent/CN115529016A/en active Pending
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