A low-pass filter with small fluctuations and high out-of-band rejection

Abstract

A low-pass filter with small fluctuations and high out-of-band rejection according to the present invention can solve the technical problem of reducing the passband fluctuations while improving the out-of-band rejection. It includes an attenuation network, a 13th-order low-pass filter network, and an all-pass filter network connected in sequence; the 13th-order low-pass filter adopts a resonant absorption structure. The all-pass filter network of the present invention plays a role in fluctuation compensation and group delay compensation, and the specific capacitance, inductance, and resistance parameters can be adjusted and used according to actual needs. The low-pass filter with small fluctuations and high out-of-band rejection according to the present invention has the advantages of small passband fluctuations, high out-of-band rejection, and small group delay. Specifically, it has high out-of-band rejection and can effectively resist signal interference, and small passband fluctuations, which can improve the gain stability of the receiver. The circuit structure is simple, the cost is low, and it has good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of signal filtering processing, and particularly relates to a low-pass filter with small fluctuations and high out-of-band rejection. Background Art

[0002] With the development of communication technology, the signal transmission distance is getting longer and the signal interference is increasing, and the requirement for out-of-band rejection of the filter is getting higher and higher. At present, the known filters are obtained through engineering transformations of mathematical models such as Butterworth, Chebyshev, and elliptic. To improve the out-of-band rejection, it is necessary to increase the circuit order, which will increase the volume of the filter, the difficulty of process manufacturing and the cost, and will also increase the passband fluctuations and reduce the gain stability of the receiver. Summary of the Invention

[0003] A low-pass filter with small fluctuations and high out-of-band rejection proposed by the present invention can solve the technical problem of reducing the passband fluctuations while improving the out-of-band rejection.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A low-pass filter with small fluctuations and high out-of-band rejection includes an attenuation network, a 13th-order low-pass filter network, and an all-pass filter network connected in sequence;

[0006] Further, the 13th-order low-pass filter adopts a resonant absorption structure.

[0007] Further, the attenuation network includes a capacitor C1, an inductor L1, and a resistor R1;

[0008] One end of the capacitor C1 and the inductor L1 is grounded, the other ends of the capacitor C1 and the inductor L1 are connected to one end of the resistor R1, and the other end of the resistor R1 forms the output end of the attenuation network and is connected to the input end of the 13th-order low-pass filter network.

[0009] Further, the 13th-order low-pass filter network includes inductors L2, L3, L4, L5, L6, and L7 connected in series in sequence;

[0010] Among them, capacitors C4 and C8 are respectively connected in parallel at both ends of the inductors L3 and L6;

[0011] One end of each of the inductors L2, L3, L4, L5, L6, and L7 is also connected to one end of each of the capacitors C2, C3, C5, C6, C7, and C9. The other end of the inductor L7 is connected to one end of the capacitor C10. The other ends of the capacitors C2, C3, C5, C6, C7, C9, and C10 are all connected to ground. One end of the inductor L2 serves as the input end of the 13 - order low - pass filter network and is connected to the attenuation network. The other end of the inductor L7 serves as the output end of the 13 - order low - pass filter network and is connected to the input end of the all - pass filter network.

[0012] Further, the all - pass filter network includes capacitors C11 and C12 connected in series;

[0013] One end of the capacitor C11 and one end of the capacitor C12 are also connected to one end of the inductor L9. The other end of the inductor L9 is connected to one end of the capacitor C13. The other end of the capacitor C13 is connected to ground;

[0014] The other end of the capacitor C11 is connected to the inductor L8. The other end of the capacitor C12 is connected to the other end of the inductor L8. One end of the inductor L8 serves as the input end of the all - pass filter network and is connected to the 13 - order low - pass filter network. The other end of the inductor L8 serves as the output end of the all - pass filter network.

[0015] Further, the cut - off frequency of the 13 - order low - pass filter is 1210 MHz.

[0016] As can be seen from the above technical solutions, the low - pass filter with small ripple and high out - of - band rejection of the present invention is based on the interference signal frequency of the operating frequency of the receiver. The low - pass filter of the present invention can avoid out - of - band signal interference and ensure signal reception by being significantly filtered in the frequency range of DC~1210 MHz and 1420 MHz~5000 MHz. The cut - off frequency of the 13 - order low - pass filter network is 1210 MHz. The attenuation network plays a role in ripple compensation. The all - pass filter network plays roles in ripple compensation and group - delay compensation. Specific capacitance, inductance, and resistance parameters can be adjusted and used according to actual needs.

[0017] A low - pass filter with small ripple and high out - of - band rejection according to the present invention. This power splitter has the advantages of small pass - band ripple, high out - of - band rejection, and small group delay. Specifically, it has high out - of - band rejection and can effectively resist signal interference. It has small pass - band ripple and can improve the gain stability of the receiver. The circuit structure is simple, the cost is low, and it has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the circuit schematic diagram of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0020] As Figure 1 shown, the low-pass filter with small fluctuations and high out-of-band suppression in this embodiment includes an attenuation network, a 13th-order low-pass filter network, and an all-pass filter network. The attenuation network is connected to the 13th-order low-pass filter network, and the 13th-order low-pass filter network is connected to the all-pass filter network.

[0021] The 13th-order low-pass filter network adopts a resonant absorption structure, which improves the out-of-band suppression of the filter.

[0022] The attenuation network includes a capacitor C1, an inductor L1, and a resistor R1. One end of the capacitor C1 and the inductor L1 is grounded, and the other ends of the capacitor C1 and the inductor L1 are connected to one end of the resistor R1. The other end of the resistor R1 forms the input end of the attenuation network and also forms the output end and is connected to the input end of the 13th-order low-pass filter network.

[0023] The 13th-order low-pass filter network includes inductors L2, L3, L4, L5, L6, L7 connected in series, and the other end of the previous inductor is connected to one end of the next inductor. Capacitors C4 and C8 are respectively connected in parallel at both ends of the inductors L3 and L6. One ends of the inductors L2, L3, L4, L5, L6, L7 are also respectively connected to one ends of capacitors C2, C3, C5, C6, C7, C9. The other end of the inductor L7 is connected to one end of the capacitor C10. The other ends of the capacitors C2, C3, C5, C6, C7, C9, C10 are all grounded. One end of the inductor L2 serves as the input end of the 13th-order low-pass filter network and is connected to the attenuation network. The other end of the inductor L7 serves as the output end of the 13th-order low-pass filter network and is connected to the input end of the all-pass filter network.

[0024] The all-pass filter network includes capacitors C11 and C12 connected in series. The other end of the capacitor C11 is connected to one end of the capacitor C12. The other end of the capacitor C11 and one end of the capacitor C12 are also connected to one end of the inductor L9. The other end of the inductor L9 is connected to one end of the capacitor C13. The other end of the capacitor C13 is grounded. One end of the capacitor C11 is connected to the inductor L8. The other end of the capacitor C12 is connected to the other end of the inductor L8. One end of the inductor L8 serves as the input end of the all-pass filter network and is connected to the 13th-order low-pass filter network. The other end of the inductor L8 serves as the output end of the all-pass filter network.

[0025] According to the interference signal frequency of the operating frequency of the receiver, in the low-pass filter of the embodiment of the present invention, the frequency in the range of DC to 1210 MHz and 1420 MHz to 5000 MHz is greatly filtered out, which can avoid out-of-band signal interference and ensure signal reception. The cut-off frequency of the 13th-order low-pass filter network is 1210 MHz. The attenuation network plays a role in ripple compensation, and the all-pass filter network plays roles in ripple compensation and group delay compensation. The specific capacitance, inductance, and resistance parameters can be adjusted and used according to actual needs.

[0026] As can be seen from the above technical solutions, the low-pass filter with small ripple and high out-of-band suppression described in the embodiment of the present invention has high out-of-band suppression, can effectively resist signal interference, has small passband ripple, and can improve the gain stability of the receiver. The circuit structure is simple, the cost is low, and it has good application prospects.

[0027] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-pass filter with small fluctuations and high out-of-band rejection, characterized in that: It includes an attenuation network, a 13th-order low-pass filter network, and an all-pass filter network connected in sequence; The 13th-order low-pass filter adopts a resonant absorption structure; The attenuation network includes a capacitor C1, an inductor L1, and a resistor R1; One end of the capacitor C1 and the inductor L1 is grounded, the other ends of the capacitor C1 and the inductor L1 are connected to one end of the resistor R1, and the other end of the resistor R1 constitutes the output end of the attenuation network and is connected to the input end of the 13th-order low-pass filter network; The 13th-order low-pass filter network includes inductors L2, L3, L4, L5, L6, L7 connected in series in sequence; Among them, capacitors C4 and C8 are respectively connected in parallel at both ends of the inductors L3 and L6; One ends of the inductors L2, L3, L4, L5, L6, L7 are also respectively connected to one ends of capacitors C2, C3, C5, C6, C7, C9, one end of the inductor L7 is connected to one end of the capacitor C10, the other ends of the capacitors C2, C3, C5, C6, C7, C9, C10 are all connected to the ground, one end of the inductor L2 serves as the input end of the 13th-order low-pass filter network and is connected to the attenuation network, and the other end of the inductor L7 serves as the output end of the 13th-order low-pass filter network and is connected to the input end of the all-pass filter network; The all-pass filter network includes capacitors C11 and C12 connected in series; One end of the capacitor C11 and one end of the capacitor C12 are also connected to one end of the inductor L9, the other end of the inductor L9 is connected to one end of the capacitor C13, and the other end of the capacitor C13 is connected to the ground; The other end of the capacitor C11 is connected to the inductor L8, the other end of the capacitor C12 is connected to the other end of the inductor L8, one end of the inductor L8 serves as the input end of the all-pass filter network and is connected to the 13th-order low-pass filter network, and the other end of the inductor L8 serves as the output end of the all-pass filter network.

2. The low-pass filter with small fluctuations and high out-of-band rejection according to claim 1, characterized in that: The cut-off frequency of the 13th-order low-pass filter is 1210 MHz.

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