CN111049554B - Method for constructing equalizer - Google Patents
Method for constructing equalizer Download PDFInfo
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- CN111049554B CN111049554B CN201911299679.8A CN201911299679A CN111049554B CN 111049554 B CN111049554 B CN 111049554B CN 201911299679 A CN201911299679 A CN 201911299679A CN 111049554 B CN111049554 B CN 111049554B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/005—Control of transmission; Equalising
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
- H04B10/114—Indoor or close-range type systems
- H04B10/116—Visible light communication
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Abstract
The invention provides a method for constructing an equalizer, which comprises the following steps: s1, measuring the visible light communication system to obtain the transfer function H of the equalizing circuitideal(s); s2, setting a full-throughNetwork transfer function Hallpass(s) passing the all-pass network transfer function HallpassZero position of(s) and equalizing circuit transfer function Hideal(s) the poles have the same position, and a zero pole positioned in a negative real number area of a complex frequency domain is obtained; s3, obtaining the transfer function H of the active circuit through the zero poleRC(s) transfer function H through equalization circuitideal(s) and pole zero obtaining passive circuit transfer function Hpassive(s) wherein the active circuit transfer function HRC(s) corresponding to the transfer function H of the active circuit, passive circuitpassive(s) corresponds to at least one first circuit; s4, connecting at least one first circuit to obtain a passive circuit; connecting the passive circuit to the active circuit to make the transfer function H of the active circuitRC(s) pole position and passive circuit transfer function HpassiveAnd(s) the poles are positioned the same to obtain the equalizer.
Description
Technical Field
The invention relates to the field of design of an indoor visible light communication system universal equalizer, in particular to a construction method of an equalizer.
Background
Conventional wireless communication systems have higher signal-to-noise ratios and lower data transmission rates, so that improvements are urgently needed for wireless communication applications. The Light Emitting Diode (LED) has the characteristics of good modulation performance and high response sensitivity, and can be used for both illumination and communication, and further can be applied to the field of optical communication, thereby meeting the demand of illumination and communication integration.
The most market share of the LED type white light LED in the field of LED optical communication is produced by mixing yellow light generated by fluorescence excited by blue light with blue light. However, the fluorescent LED has a low modulation bandwidth and a slow response speed, which makes it difficult to meet the requirement of high-speed communication. Therefore, the LED optical communication is expanded by combining various equalization technologies on the basis of the LED modulation bandwidth, and the method has important significance.
The existing analog equalization circuit is designed based on a design method of 'bottom-up', and the 'bottom-up' method comprises the following steps: firstly, a fixed circuit structure is provided, and then expected equalization effect is obtained by adjusting device parameters according to experimental results, so that the analog equalization circuit is obtained. The method can only aim at a circuit designed by a specific system and is difficult to be reused in other visible light communication systems, so that the application range of the equalizing circuit is limited by the bottom-up method. Therefore, it is highly desirable to design a universal design method for equalizing circuits.
Disclosure of Invention
Technical problem to be solved
The invention provides a construction method of an equalizer, which is at least used for solving the problem that an equalizing circuit designed by a specific system is difficult to be applied to other visible light communication systems.
(II) technical scheme
The invention provides a method for constructing an equalizer, which comprises the following steps: s1, measuring the visible light communication system to obtain the transfer function H of the equalizing circuitideal(s); s2, setting a full-pass network transfer function Hallpass(s) passing the all-pass network transfer function HallpassZero position of(s) and equalizing circuit transfer function Hideal(s) the poles have the same position, and a zero pole positioned in a negative real number area of a complex frequency domain is obtained; s3, obtaining the transfer function H of the active circuit through the zero poleRC(s) transfer function H through equalization circuitideal(s) and pole zero obtaining passive circuit transfer function Hpassive(s) wherein the active circuit transfer function HRC(s) corresponding to the transfer function H of the active circuit, passive circuitpassive(s) corresponds to at least one first circuit; s4, connecting at least one first circuit to obtain a passive circuit; connecting the passive circuit to the active circuit to make the transfer function H of the active circuitRC(s) pole position and passive circuit transfer function HpassiveAnd(s) the poles are positioned the same to obtain the equalizer.
Optionally, in step S3, the active circuit transfer function H is obtained by pole-zeroRC(s) transfer function H through equalization circuitideal(s) and pole zero obtaining passive circuit transfer function Hpassive(s) comprising: setting the first order function of the pole zero as the transfer function H of the active circuitRC(s); transfer function H of equalizing circuitideal(s) times the active circuit transfer function HRCReciprocal of(s) to obtain transfer function H of passive circuitpassive(s)。
Optionally, in step S3, the passive circuit transfer function Hpassive(s) corresponds to at least one first circuit,the method comprises the following steps: transferring a passive circuit function Hpassive(s) is decomposed into at least one first transfer function, each first transfer function corresponding to a first circuit.
Optionally, in step S4, the passive circuit and the active circuit are connected such that the active circuit has a transfer function HRC(s) pole position and passive circuit transfer function Hpassive(s) the poles are located identically, resulting in an equalizer comprising: setting a second circuit; connecting the passive circuit and the active circuit via a second circuit to make the transfer function H of the active circuitRC(s) pole position and passive circuit transfer function HpassiveAnd(s) the poles are positioned the same to obtain the equalizer.
Optionally, providing the second circuit comprises: and setting the second circuit according to the value of the output impedance of the passive circuit and the value of the input impedance of the active circuit by adopting a filter synthesis method.
Optionally, in step S1, the visible light communication system is measured to obtain the transfer function H of the equalizing circuitideal(s) comprising: measuring the visible light communication system to obtain the transfer function H of the visible light communication systemsystem(s); transfer function H of visible light communication systemsystemReciprocal of(s) as transfer function H of equalizing circuitideal(s)。
Optionally, the equalizing circuit transfer function Hideal(s) includes a plurality of fits.
Optionally, transferring the function H to a passive circuitpassive(s) decomposing into at least one first transfer function comprising: transferring a passive circuit function Hpassive(s) is decomposed into at least one first transfer function of which the highest order is second order.
Optionally, each first transfer function corresponds to a first circuit, and includes: each first transfer function corresponds to a certain T-shaped circuit of the blocking bridge.
Optionally, connecting the passive circuit and the active circuit through a second circuit, including: the passive circuit and the active circuit are connected by an impedance matching circuit.
(III) advantageous effects
1. The invention relates to aOver-obtaining the transfer function H of the active circuitRC(s) and passive circuit transfer function Hpassive(s) further obtaining a connected active circuit and a connected passive circuit, and constructing an equalizer which accords with a compensation transfer function, wherein the structure of the equalizer can be changed along with the change of the system characteristics;
2. the invention obtains the transfer function H of the equalizing circuit by measuring the visible light communication systemideal(s) can solve the problems of limited modulation bandwidth, low transmission rate and serious intersymbol interference in optical communication.
Drawings
FIG. 1 is a flow chart of an equalizer construction method according to an embodiment of the present invention;
FIG. 2 is a diagram schematically illustrating the positions of the zero points of the transfer function of the all-pass network and the positions of the poles of the transfer function of the ideal equalizing circuit in the embodiment of the present invention;
FIG. 3A is a schematic diagram illustrating one type of fixed impedance bridge T-type circuit architecture in an embodiment of the present invention;
FIG. 3B is a schematic diagram illustrating another type of fixed impedance bridge T-type circuit configuration in accordance with an embodiment of the present invention;
FIG. 4 is a diagram schematically illustrating an active circuit structure in an embodiment of the present invention;
fig. 5 schematically shows a structure of an ideal equalizing circuit in the embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to specific embodiments and the accompanying drawings.
Referring to fig. 1, fig. 1 schematically illustrates a method for constructing an equalizer according to an embodiment of the present invention, including:
and S1, measuring the visible light communication system to obtain the transfer function of the equalizing circuit.
In the embodiment of the invention, the transfer function H of the visible light communication system is obtained by measuring the visible light communication system and fitting the spectral response curve vectorsystem(s); the reciprocal of the transfer function of the visible light communication system is the transfer function H of the equalizing circuitideal(s). In the embodiment of the invention, the transfer function H of the visible light communication system is obtained after vector fitting calculationsystem(s) transfer function H of the visible light communication systemsystem(s) is a polynomial fit, which may be expressed, for example, as follows:
in the formula, aN，bMCoefficients of the numerator and denominator terms, respectively, fitted to the polynomial, s is a complex parameter variable in the laplacian domain and can be expressed as s ═ α + j ω, α is the real part of the complex frequency domain, j ω is the imaginary part of the complex frequency domain, and ω is the angular frequency, equal to 2 π f, and M ═ N + 1.
Transfer function H of equalizing circuit in the embodiment of the inventionideal(s) is the reciprocal of the transfer function of the visible light communication system, so the equalizing circuit transfer function Hideal(s) is expressed as:
in the formula, aN，bMS is a complex parameter variable in the laplacian domain and can be expressed as s ═ α + j ω, α is the real part of the complex frequency domain, j ω is the imaginary part of the complex frequency domain, and ω is the angular frequency, equal to 2 π f, and M ═ N + 1.
S2, setting a full-pass network transfer function Hallpass(s) passing said all-pass network transfer function Hallpass(s) zero position and said equalization circuit transfer function Hideal(s) the pole positions are the same, and the transfer function H of the equalizing circuit is obtainedideal(s) is located at the pole-zero of the negative real number region.
Referring to fig. 2, fig. 2 schematically illustrates a diagram of the positions of the zero points of the transfer function of the all-pass network and the positions of the poles of the transfer function of the ideal equalizing circuit according to the embodiment of the present invention. Transfer function H through a specific all-pass networkallpass(s) andconstant circuit transfer function HidealThe product of(s) yields the transfer function Hfeasible(s) the transfer function Hfeasible(s) is represented as follows:
Hfeasible(s)＝Hideal(s)×Hallpass(s) (3)
"x" in fig. 2 denotes the equalizer transfer function Hideal(s) pole locations; "Diamond" denotes the equalizer transfer function HidealZero position and transfer function H of(s)feasible(s) zero position; "Port" means the all-pass network transfer function Hallpass(s) zero position; "+" indicates the all-pass network transfer function Hallpass(s) pole location and transfer function Hfeasible(s) pole location.
As can be seen from the positive real number region of the complex frequency domain in FIG. 2, the all-pass network transfer function HallpassZero position of(s) and equalizer transfer function HidealThe pole positions of(s) are the same, so that the transfer function H of the equalizer can be realizedideal(s) zero pole point in positive and real number region of complex frequency domain and all-pass network transfer function HallpassAnd(s) canceling the zero values in the positive real number region of the complex frequency domain to obtain the zero pole in the negative real number region of the complex frequency domain. Furthermore, as can be seen from fig. 2, the all-pass network transfer function H in the embodiment of the present inventionallpass(s) has a frequency response curve in the full frequency domain, so that the transfer function H is described abovefeasible(s) and equalizer transfer function Hideal(s) have the same frequency response curve and a transfer function Hfeasible(s) avoid the equalizer transfer function HidealAnd(s) oscillation phenomenon caused by the pole in the positive real number area of the complex frequency domain.
S3, obtaining the transfer function H of the active circuit through the zero poleRC(s) transferring a function H through said equalization circuitideal(s) and said pole-zero obtaining a passive circuit transfer function Hpassive(s), wherein the active circuit transfer function HRC(s) corresponds to the active circuit, the passive circuit transfer function Hpassive(s) corresponds to at least one first circuit.
In the embodiment of the invention, the transfer function H of the active circuit is obtained through the zero poleRC(s) transfer function H through equalization circuitideal(s) and pole zero obtaining passive circuit transfer function Hpassive(s) comprises: setting the-order function of the pole zero as the transfer function H of the active circuitRC(s); make the equalizing circuit transfer function Hideal(s) times the active circuit transfer function HRCReciprocal of(s) to obtain transfer function H of passive circuitpassive(s)。
Passive circuit transfer function H in the embodiments of the present inventionpassive(s) corresponding to the at least one first circuit comprises: transferring a passive circuit function Hpassive(s) is decomposed into at least one first transfer function, each first transfer function corresponding to at least one first circuit.
In the embodiment of the invention, the transfer function H of the passive circuit is converted into the transfer functionpassive(s) decomposing into at least one first transfer function comprising: transferring a passive circuit function Hpassive(s) is decomposed into at least one first transfer function of which the highest order is second order.
In an embodiment of the present invention, each first transfer function corresponds to a first circuit, and includes: each first transfer function corresponds to a certain T-shaped circuit of the blocking bridge.
In the embodiment of the invention, the function H can be transferred through a passive circuitpassive(s) grouping adjacent conjugate zero poles by distance to obtain the following formula:
where s is a complex parametric variable in the Laplace domain, ZnRepresenting a pole zero.
Referring to fig. 3A, fig. 3A schematically illustrates a structure diagram of a type of fixed-resistance bridge T-type circuit according to an embodiment of the present invention; and fig. 3B, fig. 3B schematically shows another type of fixed resistance bridge T-type circuit structure according to an embodiment of the present invention. The first circuit may be, for example, a fixed resistance bridge T-type circuit. In FIG. 3, Z11、Z21Indicating resistanceAnd R represents a resistance value. Taking c as 1, Z11Z21＝R2Transfer function H of constant resistance bridge T-type circuitbridge(s) can be expressed as:
when R is set to 50 omega, the element parameter values of the T-shaped structure of the fixed impedance bridge can be calculated through a filter synthesis method.
The zero pole in the embodiment of the present invention can be represented as ZRC，aRCRepresenting the amplification factor, the active circuit transfer function HRC(s) is represented as follows:
HRC(s)＝aRC(s-ZRC) (6)
transfer function H of passive circuitpassve(s) is represented as follows:
in the formula, aN、bMS is a complex parameter variable in the laplacian domain and can be expressed as s ═ α + j ω, α is the real part of the complex frequency domain, j ω is the imaginary part of the complex frequency domain, and ω is the angular frequency, equal to 2 π f, and M ═ N + 1. The transfer function H of the passive circuitpassiveThe numerator of(s) is the same as the highest order of the denominator.
S4, connecting the at least one first circuit to obtain a passive circuit; connecting the passive circuit and the active circuit such that the active circuit has a transfer function HRC(s) pole position and the passive circuit transfer function HpassiveAnd(s) the poles are positioned the same to obtain the equalizer.
In the embodiment of the invention, the passive circuit and the active circuit are connected to ensure that the transfer function H of the active circuit is enabledRC(s) pole position and the passive circuit transfer function Hpassive(s) the poles are located identically, resulting in an equalizer comprising: providing a second circuit(ii) a The passive circuit and the active circuit are connected by a second circuit to make the transfer function H of the active circuitRC(s) pole position and the passive circuit transfer function HpassiveAnd(s) the poles are positioned the same to obtain the equalizer.
In the embodiment of the present invention, the connecting the passive circuit and the active circuit through the second circuit includes: the passive circuit and the active circuit are connected by an impedance matching circuit.
Referring to fig. 4, fig. 4 schematically shows a structure of an active circuit according to an embodiment of the present invention, which may be, for example, a single-pole RC active circuit. In fig. 4, R denotes a resistor, V denotes a voltage, C denotes a capacitor, and Q denotes a transistor. Thus, the active circuit transfer function HRC(s) can also be expressed as:
thus, it can be derived that the pole zero can be expressed as:
the second circuit provided in the embodiment of the present invention includes: and setting the second circuit according to the value of the output impedance of the passive circuit and the value of the input impedance of the active circuit by adopting a filter synthesis method.
The second circuit in an embodiment of the present invention includes an impedance matching circuit.
Referring to fig. 5, fig. 5 schematically shows a structure of an ideal equalizing circuit in the embodiment of the present invention. The circuit in block "a" in fig. 5 may be represented, for example, as a passive fixed-resistance cascaded bridge T-type circuit; the circuit in block "B" may be represented, for example, as an impedance matching circuit; the circuit in block "C" may be represented, for example, as an active RC circuit. An impedance matching circuit is connected between the passive circuit and the active circuit, and the impedance matching circuit enables the transfer function H of the active circuitRC(s) pole position and passive circuit transfer function Hpassive(s) have the same pole positionTo obtain the equalizer in the embodiment of the present invention.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method of constructing an equalizer, comprising:
s1, measuring the visible light communication system to obtain the transfer function H of the equalizing circuitideal(s)；
S2, setting a full-pass network transfer function Hallpass(s) passing said all-pass network transfer function Hallpass(s) zero position and said equalization circuit transfer function Hideal(s) the poles have the same position, and a zero pole positioned in a negative real number area of a complex frequency domain is obtained;
s3, obtaining the transfer function H of the active circuit through the zero poleRC(s) transferring a function H through said equalization circuitideal(s) and said pole-zero obtaining a passive circuit transfer function Hpassive(s), wherein the active circuit transfer function HRC(s) corresponds to the active circuit, the passive circuit transfer function Hpassive(s) corresponds to at least one first circuit;
s4, connecting the at least one first circuit to obtain a passive circuit; connecting the passive circuit and the active circuit such that the active circuit has a transfer function HRC(s) pole position and the passive circuit transfer function HpassiveAnd(s) the poles are positioned the same to obtain the equalizer.
2. The method of claim 1, wherein in step S3, the obtaining of the active circuit transfer function H through the pole-zero point is performedRC(s) transferring a function H through said equalization circuitideal(s) and said pole-zero obtaining a passive circuit transfer functionNumber Hpassive(s) comprising:
setting a first order function of the pole zero as the active circuit transfer function HRC(s)；
Transferring the equalizing circuit to function Hideal(s) multiplied by the active circuit transfer function HRCReciprocal of(s) to obtain the transfer function H of the passive circuitpassive(s)。
3. The building method according to claim 1, wherein in step S3, the passive circuit transfer function Hpassive(s) corresponds to at least one first circuit comprising:
transferring the passive circuit to a function Hpassive(s) is decomposed into at least one first transfer function, each of the first transfer functions corresponding to one of the first circuits.
4. The method of claim 1, wherein in step S4, the connecting the passive circuit and the active circuit causes the active circuit to transfer a function HRC(s) pole position and the passive circuit transfer function Hpassive(s) the poles are located identically, resulting in an equalizer comprising:
setting a second circuit;
connecting the passive circuit and the active circuit through the second circuit to make the transfer function H of the active circuitRC(s) pole position and the passive circuit transfer function HpassiveAnd(s) the poles are positioned the same to obtain the equalizer.
5. The build method of claim 4, wherein the providing a second circuit comprises:
and setting a second circuit according to the value of the output impedance of the passive circuit and the value of the input impedance of the active circuit by adopting a filter synthesis method.
6. The building method according to claim 1, wherein the step S1 of measuring the visible light communication system to obtain the equalizing circuit transfer function includes:
measuring the visible light communication system to obtain the transfer function H of the visible light communication systemsystem(s)；
Taking the reciprocal of the transfer function of the visible light communication system as the transfer function H of the equalizing circuitideal(s)。
7. The method of construction of claim 1 wherein the equalization circuit transfer function Hideal(s) includes a plurality of fits.
8. The method of construction of claim 3 wherein the transferring the passive circuit transfer function Hpassive(s) decomposing into at least one first transfer function comprising: transferring the passive circuit to a function Hpassive(s) is decomposed into at least one first transfer function of which the highest order is second order.
9. The method of claim 3, wherein each of the first transfer functions corresponds to a first circuit, comprising: each first transfer function corresponds to a certain blocking bridge T-shaped circuit.
10. The method of building of claim 4, wherein said connecting the passive circuit and the active circuit through the second circuit comprises: connecting the passive circuit and the active circuit through an impedance matching circuit.
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