CN110798175B - Broadband linear phase filter based on negative group delay circuit - Google Patents
Broadband linear phase filter based on negative group delay circuit Download PDFInfo
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- CN110798175B CN110798175B CN201911086686.XA CN201911086686A CN110798175B CN 110798175 B CN110798175 B CN 110798175B CN 201911086686 A CN201911086686 A CN 201911086686A CN 110798175 B CN110798175 B CN 110798175B
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H17/00—Networks using digital techniques
- H03H17/02—Frequency selective networks
- H03H17/0201—Wave digital filters
Abstract
The invention discloses a broadband linear phase filter based on a negative group delay circuit, which specifically comprises the following components: the power divider comprises an input port, a power divider, a first negative group delay circuit unit, a filtering unit, a second negative group delay circuit unit, a combiner and an output port; the first negative group delay circuit unit comprises a first negative group delay circuit unit I and a first negative group delay circuit unit II which have the same structure; the filtering unit comprises a filtering unit I and a filtering unit II which have the same structure; the second negative group time delay circuit unit comprises a second negative group time delay circuit unit I and a second negative group time delay circuit unit II which are identical in structure. The filter adopts the negative group delay circuit, so that the group delay fluctuation of the filter is less than 0.1ns in the passband range, the low group delay fluctuation of the full passband is realized, and the linear phase response is good. Meanwhile, the method has the characteristic of low manufacturing cost, and is very suitable for being applied to a broadband high-performance communication system.
Description
Technical Field
The invention relates to a filter, in particular to a broadband linear phase filter based on a negative group delay circuit.
Background
With the continuous development of scientific technology and the continuous improvement of the living standard of people, the demand and the requirement of a wireless communication transmission system are continuously improved. In measuring the performance of a transmission system, it is common to analyze the frequency domain characteristics and the time domain characteristics of the system at the same time, wherein the frequency domain characteristics include amplitude-frequency characteristics and phase-frequency characteristics. A good transmission system should have not only a flat amplitude-frequency characteristic but also a linear phase-frequency characteristic, i.e. a flat group delay characteristic. However, due to the non-uniformity of the group delay of each device in the transmission system, the fluctuation of the group delay of the whole system is usually caused, wherein the filter is the main cause of the fluctuation of the group delay in the system passband, and the filter is an indispensable part in the wireless communication system. Therefore, the group delay fluctuation of the filter is reduced, and the research on the filter with the linear phase is of great significance.
At present, there are two main methods for implementing a linear phase filter, one is a self-equalization method, and the other is an external equalization method. The self-equalization method is to introduce a transmission zero point in a real axis of a complex plane by using a cross coupling method, so that a flat group delay characteristic is generated in a filter passband. The self-equalization method must realize cross coupling, that is, in addition to the direct coupling of the adjacent resonators, the cross coupling between nonadjacent resonators exists, so the circuit structure is complex and the realization difficulty is high. The external equalization method is to add a delay equalizer in the circuit, the added delay equalizer has the group delay characteristic opposite to the fluctuation of the filter group delay, and the group delay of the whole system is flattened by the mutual superposition of the delay equalizer and the filter group delay, but the method can increase the overall delay of the system, which violates the requirement of low delay proposed in the 5G era.
With the proposal of the negative group delay circuit, a new idea and a new method are provided for improving the group delay characteristic. At present, a negative group delay circuit is used to offset the positive group delay, and the negative group delay circuit has been successfully applied in various fields such as improving the efficiency of an amplifier, widening the bandwidth of the amplifier, improving the integrity of signals, and the like. In view of the above, it is necessary to provide a wideband linear phase filter based on a negative group delay circuit to implement a wideband linear phase filter with small group delay fluctuation in the whole passband, so as to solve the problems in the prior art.
Disclosure of Invention
According to the problems existing in the prior art, the invention discloses a broadband linear phase filter based on a negative group delay circuit, which specifically comprises the following components:
the device comprises an input port, a power divider, a first negative group time delay circuit unit, a filtering unit, a second negative group time delay circuit unit, a combiner and an output port;
the first negative group delay circuit unit comprises a first negative group delay circuit unit I and a first negative group delay circuit unit II which have the same structure; the filtering unit comprises a filtering unit I and a filtering unit II which have the same structure; the second negative group delay circuit unit comprises a second negative group delay circuit unit I and a second negative group delay circuit unit II which have the same structure;
the input signal transmitted to the power divider is output by two transmission paths, wherein the first transmission path comprises a first negative group delay circuit unit I, a filter unit I and a second negative group delay circuit unit I which are connected in sequence, and the second transmission path comprises a second negative group delay circuit unit II, a filter unit II and a first negative group delay circuit unit II which are connected in sequence; and the output signals of the second negative group time delay circuit unit I and the first negative group time delay circuit unit II are transmitted to the combiner to be combined into a signal and output by the output port.
The first negative group time delay circuit unit I comprises a microstrip transmission line I, a resistor I and a short circuit transmission line I; one end of the microstrip transmission line I is connected with the resistor I and the short-circuit transmission line I at the same time, the other end of the microstrip transmission line I is connected with the power divider, and the other end of the resistor I is grounded.
The filtering unit I comprises N resonators and N-1 admittance converters, and N is the order of the filter.
The second negative group time delay circuit unit I comprises a microstrip transmission line II, a resistor II and a short circuit transmission line II; one end of the microstrip transmission line II is simultaneously connected with the resistor II and the short circuit transmission line II, the other end of the microstrip transmission line II is connected with the combiner, and the other end of the resistor II is grounded.
The length of the microstrip transmission line I and the length of the short circuit transmission line I are one fourth of the wavelength corresponding to the working frequency of the first negative group delay circuit unit.
And the length of the microstrip transmission line II and the short circuit transmission line II is one fourth of the wavelength corresponding to the working frequency of the second negative group delay circuit unit.
The working frequency of the first negative group of delay circuit units is different from that of the second negative group of delay circuit units.
Furthermore, the working frequency of the first negative group delay circuit unit is f 0 -0.5 Δ f, the frequency f 0 Is the center frequency of the filter, Δ f is the bandwidth of the filter; the working frequency of the second negative group delay circuit unit is f 0 +0.5Δf。
Due to the adoption of the technical scheme, the broadband linear phase filter based on the negative group delay circuit provided by the invention has the advantages that the circuit structure realizes low group delay fluctuation of the full passband and has good linear phase response. Meanwhile, the method has the characteristic of low manufacturing cost, and is very suitable for being applied to a broadband high-performance communication system.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present application, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a schematic diagram of a wideband linear phase filter based on a negative group delay circuit according to the present invention;
FIG. 2 is a graph of the S-parameter of a broadband linear phase filter based on a negative group delay circuit according to the present invention;
FIG. 3 is a group delay plot of a broadband linear phase filter based on a negative group delay circuit according to the present invention;
in the figure: 1. an input port, 2, a power divider, 3, a first negative group delay circuit unit, 31, a first negative group delay circuit unit i, 311, a microstrip transmission line i, 312 in the first negative group delay circuit unit i, a resistance i, 313 in the first negative group delay circuit unit i, a short circuit transmission line i, 32 in the first negative group delay circuit unit i, a first negative group delay circuit unit ii, 4, a filter unit, 41, a filter unit i, 411, N resonators in the filter unit i, 412, N-1 admittance converters in the negative group delay filter unit i, 5, a second negative group delay circuit unit, 51, a second negative group delay circuit unit i, 511, a microstrip transmission line ii, 512 in the second negative group delay circuit unit i, a resistance ii, 513 in the second negative group delay circuit unit i, a short circuit transmission line ii in the second negative group delay circuit unit i, 52, a second negative group delay circuit unit, 6, a combiner, 7, and an output port.
Detailed Description
In order to make the technical solutions and advantages of the present invention clearer, the following describes the technical solutions in the embodiments of the present invention clearly and completely with reference to the drawings in the embodiments of the present invention:
as shown in fig. 1, the broadband linear phase filter based on the negative group delay circuit specifically includes an input port 1, a power divider 2, a first negative group delay circuit unit 3, a filtering unit 4, a second negative group delay circuit unit 5, a combiner 6, and an output port 7; the input signal of the input port 1 is divided into two paths of signals by the power divider 2 with equal power, the first path of signal sequentially passes through the first negative group delay circuit unit i 31, the filter unit i 41 and the second negative group delay circuit unit i 51, the second path of signal sequentially passes through the second negative group delay circuit unit ii 52, the filter unit ii 42 and the first negative group delay circuit unit ii 32, and the two paths of signals are finally combined into one path of signal by the combiner 6 and output by the output port 7. The first negative group delay circuit unit 3 comprises a first negative group delay circuit unit I31 and a first negative group delay circuit unit II 32 which have the same structure; the first negative group delay circuit unit I31 comprises a microstrip transmission line I311, a resistor I312 and a short circuit transmission line I313; one end of the microstrip transmission line 311 is connected with the resistor I312 and the short-circuit transmission line I313 at the same time, and the other end of the microstrip transmission line is connected with the power divider 2; the other end of the resistor I312 is grounded. The filtering unit 4 comprises a filtering unit I41 and a filtering unit II 42 which have the same structure; the filtering unit I41 comprises N resonators 411 and N-1 admittance converters 412; the N is the order of the filter; the second negative group delay circuit unit 5 comprises a second negative group delay circuit unit I51 and a second negative group delay circuit unit II 52 which have the same structure; the second negative group delay circuit unit I51 comprises a microstrip transmission line II 511, a resistor II 512 and a short circuit transmission line II 513; one end of the microstrip transmission line II 511 is connected with the resistor II 512 and the short-circuit transmission line II 513 at the same time, and the other end of the microstrip transmission line II 511 is connected with the combiner 6; the other end of the resistor II 512 is grounded.
Further, the working frequency of the first negative group delay circuit unit 4 is f 0 -0.5 Δ f, the frequency f 0 Is the center frequency of the filter, Δ f is the bandwidth of the filter; the working frequency of the second negative group time delay circuit unit 5 is f 0 +0.5 Δ f; the length of the microstrip transmission line I411 and the short circuit transmission line I413 is one quarter of the wavelength corresponding to the working frequency of the first negative group delay circuit unit 4; the length of the microstrip transmission line II 511 and the short circuit transmission line II 513 is one fourth of the wavelength corresponding to the working frequency of the second negative group delay circuit unit 5.
Further, the power divider 2 and the combiner 6 are used for realizing input-output port matching.
Example (b):
this embodiment lists the center frequency f 0 A3-order filter with the relative bandwidth of 30% is designed and explained at 2.45GHz, and a Chebyshev low-pass prototype with the ripple coefficient of 0.05dB is used for design. As shown in FIG. 2, the passband of the broadband linear phase filter based on the negative group delay circuit is 2.115 GHz-2.761 GHz, the passband bandwidth is 646MHz, and the return loss in the passband range is better than 12dB. As shown in fig. 3, the group delay of the broadband linear phase filter based on the negative group delay circuit fluctuates by less than 0.1ns in the whole passband range, so that the low group delay fluctuation of the full passband is realized, and the broadband linear phase filter has good linear phase response.
The invention relates to a broadband linear phase filter based on a negative group delay circuit, which adopts the proposed circuit structure, and the negative group delay circuit is adopted, so that the group delay fluctuation of the filter is less than 0.1ns in the passband range, the low group delay fluctuation of the full passband is realized, and the broadband linear phase filter has good linear phase response. Meanwhile, the method has the characteristic of low manufacturing cost, and is very suitable for being applied to a broadband high-performance communication system.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (7)
1. A broadband linear phase filter based on a negative group delay circuit is characterized by comprising: the power divider comprises an input port (1), a power divider (2), a first negative group delay circuit unit (3), a filtering unit (4), a second negative group delay circuit unit (5), a combiner (6) and an output port (7);
the first negative group delay circuit unit (3) comprises a first negative group delay circuit unit I (31) and a first negative group delay circuit unit II (32) which are identical in structure; the filtering unit (4) comprises a filtering unit I (41) and a filtering unit II (42) which have the same structure; the second negative group delay circuit unit (5) comprises a second negative group delay circuit unit I (51) and a second negative group delay circuit unit II (52) which are identical in structure;
the input signal transmitted to the power divider (2) is output by two transmission paths, wherein the first transmission path comprises a first negative group delay circuit unit I (31), a filtering unit I (41) and a second negative group delay circuit unit I (51) which are sequentially connected, and the second transmission path comprises a second negative group delay circuit unit II (52), a filtering unit II (42) and a first negative group delay circuit unit II (32) which are sequentially connected; output signals of the second negative group time delay circuit unit I (51) and the first negative group time delay circuit unit II (32) are transmitted to the combiner (6) to be combined into a signal and output by the output port (7).
2. The negative group delay circuit based wideband linear phase filter of claim 1 further characterized by: the first negative group delay circuit unit I (31) comprises a microstrip transmission line I (311), a resistor I (312) and a short circuit transmission line I (313); one end of the microstrip transmission line I (311) is connected with the resistor I (312) and the short-circuit transmission line I (313) at the same time, the other end of the microstrip transmission line I is connected with the power divider (2), and the other end of the resistor I (312) is grounded.
3. The negative group delay circuit based wideband linear phase filter of claim 1 further characterized by: the filtering unit I (41) comprises N resonators (411) and N-1 admittance converters (412), wherein N is the order of the filter.
4. The negative group delay circuit based wideband linear phase filter of claim 1 further characterized by: the second negative group delay circuit unit I (51) comprises a microstrip transmission line II (511), a resistor II (512) and a short circuit transmission line II (513); one end of the microstrip transmission line II (511) is connected with the resistor II (512) and the short circuit transmission line II (513) at the same time, the other end of the microstrip transmission line II is connected with the combiner (6), and the other end of the resistor II (512) is grounded.
5. The negative group delay circuit-based wideband linear phase filter of claim 2, further characterized by: the length of the microstrip transmission line I (311) and the length of the short circuit transmission line I (313) are one fourth of the wavelength corresponding to the working frequency of the first negative group time delay circuit unit (3).
6. The negative group delay circuit based wideband linear phase filter of claim 4 further characterized by: the length of the microstrip transmission line II (511) and the length of the short circuit transmission line II (513) are one fourth of the wavelength corresponding to the working frequency of the second negative group time delay circuit unit (5).
7. The negative group delay circuit based wideband linear phase filter of claim 5 or 6, further characterized by: the working frequency of the first negative group delay circuit unit (3) is different from the working frequency of the second negative group delay circuit unit (5).
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| CN201911086686.XA CN110798175B (en) | 2019-11-08 | 2019-11-08 | Broadband linear phase filter based on negative group delay circuit |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104882658A (en) * | 2015-04-28 | 2015-09-02 | 南京信息工程大学 | Combiner including three paths of VHFs and one path of UHF |
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| CN104882658A (en) * | 2015-04-28 | 2015-09-02 | 南京信息工程大学 | Combiner including three paths of VHFs and one path of UHF |
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| 刘乾易 ; 李勇 ; 胡斯佳 ; 罗隆福 ; 曹一家 ; .电力感应调控滤波系统滤波机理与运行特性分析.(第14期),全文. * |
| 唐毅 ; 童玲 ; .高频头中微带滤波器和振荡器的设计与实现.(第05期),全文. * |
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