CN104580046A

CN104580046A - V-F conversion-based 2FSK modulation circuit

Info

Publication number: CN104580046A
Application number: CN201410811127.1A
Authority: CN
Inventors: 胡之惠; 王利平; 陈布雨; 杨宇
Original assignee: Shanghai Dianji University
Current assignee: Shanghai Dianji University
Priority date: 2014-12-19
Filing date: 2014-12-19
Publication date: 2015-04-29

Abstract

The invention discloses a 2FSK modulation circuit based on VF conversion, which at least includes: an integrating circuit for generating a triangular wave output proportional to the first input control voltage; a hysteresis comparator for converting the triangular wave output by the integrating circuit It is a square wave output to control the discharge switch circuit; the discharge switch circuit is used to regularly discharge the integral capacitance of the integral circuit under the control of the hysteresis comparator; the sine wave shaping circuit is used to convert the triangular wave into a continuous phase Sine wave, the present invention uses VF conversion to make the oscillation frequency of the output rectangular wave proportional to the control voltage, and improves the circuit, adding a series of waveform conversion circuits, according to the two level changes of the control voltage, the output is in two A sine wave varying between different frequencies, thus realizing phase continuous 2FSK modulation without an external frequency source.

Description

A 2FSK modulation circuit based on V-F conversion

技术领域technical field

本发明涉及一种2FSK调制电路，特别是涉及一种基于V-F转换的2FSK调制电路。The invention relates to a 2FSK modulation circuit, in particular to a 2FSK modulation circuit based on V-F conversion.

背景技术Background technique

随着电子计算机的普及，数字通信技术得到了迅速发展，数字频率调制是数字通信中常见的一种调制方式，频移键控(FSK)方法简单，易于实现，并且解调不需恢复本地载波，可以异步传输，抗噪声和抗衰落性能比较强，在中低速数据传输中应用十分广泛。With the popularization of electronic computers, digital communication technology has developed rapidly. Digital frequency modulation is a common modulation method in digital communication. The frequency shift keying (FSK) method is simple and easy to implement, and demodulation does not need to restore the local carrier , can be transmitted asynchronously, has strong anti-noise and anti-fading performance, and is widely used in medium and low-speed data transmission.

FSK利用载频频率的变化来传递数字信息。2FSK是指基带信号“1”对应于载频f1，基带信号“0”对应另一载频f0的已调波形，而且f1和f0之间的改变是瞬间完成的。表达式如式1所示。FSK uses changes in carrier frequency to transmit digital information. 2FSK means that the baseband signal "1" corresponds to the carrier frequency f1, and the baseband signal "0" corresponds to the modulated waveform of another carrier frequency f0, and the change between f1 and f0 is completed instantaneously. The expression is shown in formula 1.

2FSK调制方法主要有两种。一种是调频法，用一个矩形脉冲序列对一个载波进行调频，产生相位连续的数字调频信号；另一种是开关法，利用矩形脉冲序列控制的开关电路，对两个不同的独立频率源进行选通，由于频率源之间的相位互不相关，容易产生相位离散的数字调频信号。There are two main 2FSK modulation methods. One is the frequency modulation method, which uses a rectangular pulse sequence to modulate the frequency of a carrier to generate a phase-continuous digital frequency modulation signal; the other is the switching method, which uses a rectangular pulse sequence controlled switching circuit to control two different independent frequency sources. Gating, because the phases between frequency sources are not correlated with each other, it is easy to generate a digital FM signal with discrete phases.

综上所述，现有技术之2FSK调制方法存在需要外加频率源，并且由于频率源之间的相位互不相关，容易产生相位离散的数字调频信号的问题，因此，实有必要提出一种技术手段，以解决上述问题。In summary, the 2FSK modulation method in the prior art requires an external frequency source, and because the phases between the frequency sources are not correlated with each other, it is easy to generate a phase-discrete digital FM signal. Therefore, it is necessary to propose a technology means to solve the above problems.

发明内容Contents of the invention

为克服上述现有技术存在的不足，本发明之目的在于提供一种基于V-F转换的2FSK调制电路，其利用V-F转换使输出矩形波的振荡频率与控制电压成正比的特性，并对电路进行改进，增加系列波形变换电路，根据控制电压的两种电平变化，随之输出在两种不同频率间变化的正弦波，从而在无外加频率源的情况下，实现相位连续的2FSK调制。In order to overcome the deficiencies in the above-mentioned prior art, the object of the present invention is to provide a 2FSK modulation circuit based on V-F conversion, which utilizes V-F conversion to make the oscillation frequency of the output rectangular wave proportional to the control voltage, and improve the circuit , adding a series of waveform conversion circuits, according to the two level changes of the control voltage, the sine wave that changes between two different frequencies is output, so that the phase continuous 2FSK modulation can be realized without an external frequency source.

为达上述及其它目的，本发明提出一种基于V-F变换的2FSK调制电路，至少包括：For reaching above-mentioned and other purposes, the present invention proposes a kind of 2FSK modulation circuit based on V-F conversion, at least comprises:

积分电路，用于产生一与第一输入控制电压成比例的三角波输出；an integrating circuit for generating a triangular wave output proportional to the first input control voltage;

迟滞比较器，用于将该积分电路输出的三角波转换为方波输出以控制放电开关电路；A hysteresis comparator is used to convert the triangular wave output by the integrating circuit into a square wave output to control the discharge switch circuit;

放电开关电路，用于在该迟滞比较器的控制下定时对该积分电路的积分电容进行放电；A discharge switch circuit, used to regularly discharge the integral capacitance of the integral circuit under the control of the hysteresis comparator;

正弦波整形电路，用于将该三角波转换为相位连续的正弦波。A sine wave shaping circuit for converting the triangular wave into a phase continuous sine wave.

进一步地，该积分电路包括第一电阻、第三电阻、第四电阻、第一电容及第一比较器，该第三电阻一端连接第一输入控制电压，另一端接该第一电容和第一比较器的反相输入端，该第一电容另一端接该第一比较器的输出端，该第一输入控制电压经该第四电阻、第一电阻分压后得到一电压，该电压接入该第一比较器的同相输入端以控制该积分电路的积分时间，该第一比较器的输出为近似三角波的充放电电压。Further, the integrating circuit includes a first resistor, a third resistor, a fourth resistor, a first capacitor and a first comparator, one end of the third resistor is connected to the first input control voltage, and the other end is connected to the first capacitor and the first The inverting input terminal of the comparator, the other terminal of the first capacitor is connected to the output terminal of the first comparator, the first input control voltage is divided by the fourth resistor and the first resistor to obtain a voltage, and the voltage is connected to The non-inverting input terminal of the first comparator is used to control the integration time of the integrating circuit, and the output of the first comparator is a charge-discharge voltage approximately triangular wave.

进一步地，该第一比较器的输出一路接至该迟滞比较器，另一路接至该正弦波整形电路。Further, one output of the first comparator is connected to the hysteresis comparator, and the other output is connected to the sine wave shaping circuit.

进一步地，该放电开关电路包括第二电阻、第五电阻及第一三极管，该第一三极管发射极接地，其集电极经该第二电阻连接至该第一比较器的反相输入端，其基极经该第五电阻连接至该迟滞比较器的输出端。Further, the discharge switch circuit includes a second resistor, a fifth resistor and a first triode, the emitter of the first triode is grounded, and its collector is connected to the inverting phase of the first comparator through the second resistor The input terminal, the base of which is connected to the output terminal of the hysteresis comparator via the fifth resistor.

进一步地，该迟滞比较器包括第六电阻、第七电阻和第二比较器，该第六电阻一端接第二控制电压，另一端接该第七电阻和该第二比较器的同相输入端，该第七电阻另一端接该第二比较器的输出端，该第二比较器的输出经该第五电阻连接至该第一三极管的基极。Further, the hysteresis comparator includes a sixth resistor, a seventh resistor and a second comparator, one end of the sixth resistor is connected to the second control voltage, and the other end is connected to the seventh resistor and the non-inverting input end of the second comparator, The other end of the seventh resistor is connected to the output end of the second comparator, and the output of the second comparator is connected to the base of the first triode through the fifth resistor.

进一步地，该正弦波整形电路包括第八至第十五电阻、第十八电阻、第一可变电阻、第二可变电阻、第二NPN三极管、第三NPN三极管、第四PNP三极管、第五PNP三极管，该第十五电阻的一端连接该第一比较器的输出端，另一端接该第二可变电阻之可变电阻端，该第二可变电阻的可变电阻端和一端短接而另一端接该第二NPN三极管基极和第十三电阻的一端，该第一可变电阻接在正电源和地之间，在其可变电阻端输出一偏置电压，该偏置电压经该第十四电阻连接至该第二NPN三极管的基极使该第二NPN三极管工作于S形曲线的中心，该第二NPN三极管和第三NPN三极管发射极通过该第十电阻、第十一电阻连接至该第十二电阻的一端，该第十二电阻的另一端接负电源，该第二NPN三极管的集电极接该第四PNP三极管的基极和集电极，该第三NPN三极管的集电极接该第五PNP三极管的集电极和第十八电阻的一端，该第十八电阻的另一端和该第三NPN三极管的基极接地，该第四PNP三极管和该第五PNP三极管的基极背靠背连接，该第四PNP三极管和该第五PNP三极管的发射极分别通过该第八电阻、第九电阻连接至正电源。Further, the sine wave shaping circuit includes eighth to fifteenth resistors, an eighteenth resistor, a first variable resistor, a second variable resistor, a second NPN transistor, a third NPN transistor, a fourth PNP transistor, a fourth Five PNP transistors, one end of the fifteenth resistor is connected to the output end of the first comparator, the other end is connected to the variable resistance end of the second variable resistance, and the variable resistance end of the second variable resistance is shorted to one end. The other end is connected to the base of the second NPN transistor and one end of the thirteenth resistor, the first variable resistor is connected between the positive power supply and the ground, and a bias voltage is output at its variable resistor end, the bias The voltage is connected to the base of the second NPN transistor through the fourteenth resistor to make the second NPN transistor work in the center of the S-shaped curve, and the emitters of the second NPN transistor and the third NPN transistor pass through the tenth resistor, the first The eleventh resistor is connected to one end of the twelfth resistor, the other end of the twelfth resistor is connected to a negative power supply, the collector of the second NPN transistor is connected to the base and collector of the fourth PNP transistor, and the third NPN The collector of the transistor is connected to the collector of the fifth PNP transistor and one end of the eighteenth resistor, the other end of the eighteenth resistor and the base of the third NPN transistor are grounded, the fourth PNP transistor and the fifth PNP The bases of the transistors are connected back to back, and the emitters of the fourth PNP transistor and the fifth PNP transistor are respectively connected to the positive power supply through the eighth resistor and the ninth resistor.

进一步地，该第一比较器的输出经隔直电容连接至该第十五电阻的一端。Further, the output of the first comparator is connected to one end of the fifteenth resistor through a DC blocking capacitor.

进一步地，该第十电阻与该第十一电阻为等值电阻，该第八电阻与该第九电阻为等值电阻。Further, the tenth resistor and the eleventh resistor are equivalent resistors, and the eighth resistor and the ninth resistor are equivalent resistors.

与现有技术相比，本发明一种基于V-F转换的2FSK调制电路通过设置控制电压的电平变化，使V-F转换电路输出在两种不同频率间变化的矩形波，并对V-F转换电路进行改进，根据控制电压的两种电平变化，随之输出在两种不同频率间变化的正弦波，一方面可以减少电路的复杂程度，让电路结构简洁，另一方面可以减少波形转换过程中的误差，提高了电路的精准性。Compared with the prior art, a 2FSK modulation circuit based on V-F conversion in the present invention makes the V-F conversion circuit output a rectangular wave that changes between two different frequencies by setting the level change of the control voltage, and improves the V-F conversion circuit , according to the two level changes of the control voltage, a sine wave that changes between two different frequencies is output accordingly. On the one hand, it can reduce the complexity of the circuit and make the circuit structure simple. On the other hand, it can reduce the error in the waveform conversion process , which improves the accuracy of the circuit.

附图说明Description of drawings

图1为典型的V-F转换电路图；Figure 1 is a typical V-F conversion circuit diagram;

图2为差分管的传输特性示意图；Figure 2 is a schematic diagram of the transmission characteristics of the differential tube;

图3为本发明一种基于V-F变换的2FSK调制电路的电路结构图；Fig. 3 is the circuit structural diagram of a kind of 2FSK modulation circuit based on V-F conversion of the present invention;

图4、图5、图6分别为本发明仿真结果的V-F转换结果、三角波输出及输出的2FSK信号。Fig. 4, Fig. 5, Fig. 6 are the V-F conversion result of the simulation result of the present invention, triangular wave output and the 2FSK signal of output respectively.

具体实施方式Detailed ways

以下通过特定的具体实例并结合附图说明本发明的实施方式，本领域技术人员可由本说明书所揭示的内容轻易地了解本发明的其它优点与功效。本发明亦可通过其它不同的具体实例加以施行或应用，本说明书中的各项细节亦可基于不同观点与应用，在不背离本发明的精神下进行各种修饰与变更。The implementation of the present invention is described below through specific examples and in conjunction with the accompanying drawings, and those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific examples, and various modifications and changes can be made to the details in this specification based on different viewpoints and applications without departing from the spirit of the present invention.

在介绍本发明之前，先描述一下V-F转换原理：Before introducing the present invention, first describe the V-F conversion principle:

图1为典型的V-F转换电路图。如图1所示，A1，C1，R1等构成积分电路。A2，R5，R7等构成滞回比较器，其参考电压为E2，其输出包含输出上限VOM和输出下限-VOM两种状态。电路输出vO经过反馈支路控制三极管T1的导通和截止，进而控制电容C1的充放电时间。输入电压E1的数值变化决定A1同相输入端电位VP1，从而控制积分电路的积分时间，使输出信号的频率随之改变。Figure 1 is a typical V-F conversion circuit diagram. As shown in Figure 1, A1, C1, R1, etc. constitute an integrating circuit. A2, R5, R7, etc. form a hysteresis comparator, its reference voltage is E2, and its output includes two states: output upper limit VOM and output lower limit -VOM. The circuit output vO controls the turn-on and cut-off of the triode T1 through the feedback branch, and then controls the charging and discharging time of the capacitor C1. The value change of the input voltage E1 determines the potential VP1 of the non-inverting input terminal of A1, thereby controlling the integration time of the integration circuit and changing the frequency of the output signal accordingly.

对A2，R5，R7等构成的滞回比较器电路分析可得，A2同相输入电压如式(2)所示Analyzing the hysteresis comparator circuit composed of A2, R5, R7, etc., it can be obtained that the non-inverting input voltage of A2 is shown in formula (2)

${v v}_{P P 22} = = \frac{{R R}_{77}}{{R R}_{55} + + {R R}_{77}} {E E.}_{22} + + \frac{{R R}_{55}}{{R R}_{55} + + {R R}_{77}} {v v}_{O o} - - - - - - ((22))$

比较器翻转阈值对应如下：The comparator flipping threshold corresponds to the following:

v_O＝+V_OM时，When v _O ＝+V _OM ,

${V V}_{AH AH} = = \frac{{R R}_{77}}{{R R}_{55} + + {R R}_{77}} {E E.}_{22} + + \frac{{R R}_{55}}{{R R}_{55} + + {R R}_{77}} {V V}_{OM om} - - - - - - ((33))$

v_O＝-V_OM时，When v _O ＝-V _OM ,

${V V}_{AL AL} = = \frac{{R R}_{77}}{{R R}_{55} + + {R R}_{77}} {E E.}_{22} - - \frac{{R R}_{55}}{{R R}_{55} + + {R R}_{77}} {V V}_{OM om} - - - - - - ((44))$

假设R₅＝100KΩ，R₇＝200KΩ，由式(3)、式(4)得Suppose R ₅ =100KΩ, R ₇ =200KΩ, from formula (3) and formula (4)

${V V}_{AH AH} = = \frac{22}{33} {E E.}_{22} + + \frac{11}{33} {V V}_{OM om} - - - - - - ((55))$

${V V}_{AL AL} = = \frac{22}{33} {E E.}_{22} - - \frac{11}{33} {V V}_{OM om} - - - - - - ((66))$

当v_O＝+V_OM时，三极管T1饱和，忽略饱和压降，得When v _O ＝+V _OM , the transistor T1 is saturated, ignoring the saturation voltage drop, we get

$\frac{{E E.}_{11} - - {V V}_{P P 11}}{{R R}_{11}} + + {C C}_{11} \frac{d d (({v v}_{C C} - - {V V}_{P P 11}))}{dt dt} = = \frac{{V V}_{P P 11}}{{R R}_{33}} - - - - - - ((77))$

其中式(7)化简得in Equation (7) simplifies to get

${C C}_{11} \frac{{dv dv}_{C C}}{dt dt} = = ((\frac{11}{{R R}_{33}} + + \frac{11}{{R R}_{11}})) {V V}_{P P 11} - - \frac{{E E.}_{11}}{{R R}_{11}} - - - - - - ((88))$

设R₁＝100KΩ，R₂＝R₃＝R₄＝50KΩ，得Let R ₁ =100KΩ, R ₂ =R ₃ =R ₄ =50KΩ, get

${v v}_{C C} = = \frac{11}{22 \times \times 1010^{55}} \frac{{E E.}_{11}}{{C C}_{11}} &Integral; &Integral; dt dt + + {V V}_{AL AL} - - - - - - ((99))$

当v_O＝-V_OM时，三极管T1截止，得When v _O =-V _OM , the transistor T1 is cut off, and

$\frac{{E E.}_{11} - - {V V}_{P P 11}}{{R R}_{11}} = = - - {C C}_{11} \frac{d d (({v v}_{C C} - - {V V}_{P P 11}))}{dt dt} = = - - {C C}_{11} \frac{{dv dv}_{C C}}{dt dt} - - - - - - ((1010))$

${v v}_{C C} = = - - \frac{11}{22 \times \times 1010^{55}} \frac{{E E.}_{11}}{{C C}_{11}} &Integral; &Integral; dt dt + + {V V}_{AH AH} - - - - - - ((1111))$

结合式(5)和式(9)分析得Combining formula (5) and formula (9) to analyze

$\frac{22}{33} {E E.}_{22} + + \frac{11}{33} {V V}_{OM om} = = \frac{11}{22 \times \times 1010^{55}} \frac{{E E.}_{11}}{{C C}_{11}} &Integral; &Integral; dt dt + + \frac{22}{33} {E E.}_{22} - - \frac{11}{33} {V V}_{OM om} - - - - - - ((1212))$

vO低电平时间为vO low level time is

${T T}_{L L} = = \frac{44 \times \times 1010^{55}}{33} \frac{{V V}_{OM om} \cdot \cdot {C C}_{11}}{{E E.}_{11}} - - - - - - ((1313))$

结合式(6)和式(11)分析得Combining formula (6) and formula (11) to analyze

$\frac{22}{33} {E E.}_{22} - - \frac{11}{33} {V V}_{OM om} = = - - \frac{11}{22 \times \times 1010^{55}} \frac{{E E.}_{11}}{{C C}_{11}} &Integral; &Integral; dt dt + + \frac{22}{33} {E E.}_{22} + + \frac{11}{33} {V V}_{OM om} - - - - - - ((1414))$

vO高电平时间为vO high level time is

${T T}_{H h} = = \frac{44 \times \times 1010^{55}}{33} \frac{{V V}_{OM om} \cdot &Center Dot; {C C}_{11}}{{E E.}_{11}} - - - - - - ((1515))$

所以，振荡频率为Therefore, the oscillation frequency is

$f f = = \frac{11}{{T T}_{H h} + + {T T}_{L L}} = = \frac{{33 E E.}_{11}}{88 \times \times 1010^{55} {V V}_{OM om} \cdot &Center Dot; {C C}_{11}} - - - - - - ((1616))$

综上，振荡输出信号为矩形波，频率随输入电压E1线性变化。In summary, the oscillation output signal is a rectangular wave, and the frequency varies linearly with the input voltage E1.

可见，V-F转换电路能使输出矩形波的振荡频率与控制电压成正比，为实现2FSK调制，本发明在V-F转换电路基础上做进一步改进，实现根据两种不同输入电平，对应输出两种不同频率的正弦波。一般地，要将矩形波先经过积分转换为三角波，然后再经过波形变换转换为正弦波。经电路分析得，V-F转换电路中的积分电路本身能产生和通过滞回比较器之后产生的矩形波频率相同的三角波，因此，本发明将直接把该三角波作为变换电路的输入信号，经过系列电路变换后产生对应的正弦波，一方面可以减少电路的复杂程度，让电路结构简洁，另一方面可以减少波形转换过程中的误差，提高了电路的精准性。It can be seen that the V-F conversion circuit can make the oscillation frequency of the output rectangular wave proportional to the control voltage. In order to realize 2FSK modulation, the present invention makes further improvements on the basis of the V-F conversion circuit, and realizes two different output levels according to two different input levels. frequency of the sine wave. Generally, the rectangular wave should be converted into a triangular wave through integration first, and then converted into a sine wave through waveform transformation. Through circuit analysis, the integral circuit in the V-F conversion circuit itself can produce the same triangular wave with the frequency of the rectangular wave produced after passing through the hysteresis comparator. Therefore, the present invention will directly use the triangular wave as the input signal of the conversion circuit, and pass through a series of circuits. The corresponding sine wave is generated after conversion. On the one hand, it can reduce the complexity of the circuit and make the circuit structure simple. On the other hand, it can reduce the error in the waveform conversion process and improve the accuracy of the circuit.

在本发明中，利用差分放大电路的非线性传输特性实现三角波—正弦波的变换。根据典型差分放大电路的差模传输特性，它的输出电流(电压)与差模输入电压之间的关系符合双曲正切函数的变化规律。当三角波输入接近差分管的饱和区时,输出波形被如图2所示的S形曲线削平，即输入合适电压时,可使输出非常接近于正弦波。为了使输出波形更接近正弦波，差分放大电路的传输特性应尽可能对称，且线性区越窄越好。In the present invention, the conversion of triangular wave to sine wave is realized by utilizing the non-linear transmission characteristic of the differential amplifier circuit. According to the differential mode transmission characteristics of a typical differential amplifier circuit, the relationship between its output current (voltage) and differential mode input voltage conforms to the change law of the hyperbolic tangent function. When the triangular wave input is close to the saturation area of the differential tube, the output waveform is flattened by the S-shaped curve shown in Figure 2, that is, when the appropriate voltage is input, the output can be very close to the sine wave. In order to make the output waveform closer to a sine wave, the transmission characteristics of the differential amplifier circuit should be as symmetrical as possible, and the narrower the linear region, the better.

图3为本发明一种基于V-F变换的2FSK调制电路的电路结构图。如图3所示，本发明一种V-F变换的2FSK调制电路，包含积分电路10、迟滞比较器20、放电开关电路30、正弦波整形电路40，积分电路10由电阻R1、R3-4、电容C1和比较器U1组成，用于产生一和第一输入控制电压成比例的三角波输出，迟滞比较器20由电阻R6、R7和比较器U2组成，用于将积分电路10输出的三角波转换为方波输出以控制放电开关电路30，放电开关电路30由电阻R5、R2和三极管Q1组成，用于在迟滞比较器20的控制下定时对积分电路10的积分电容C1进行放电，正弦波整形电路40由电阻R8-15、R18、可变电阻R16-17(分别为第一可变电阻与第二可变电阻)、NPN对管Q2-3和PNP对管Q4-5组成，其中PNP对管Q4-5和电阻R8-9组成镜像恒流源(比例电流源)，NPN对管Q2-3和电阻R10-11组成差分放大器，用于将三角波转换为相位连续的正弦波，C2为隔直电容。将第一输入控制电压V4换成数字“0”、“1”系列，则可在NPN三极管Q3之集电极输出已调制的连续相位的正弦波2FSK电压。FIG. 3 is a circuit structure diagram of a 2FSK modulation circuit based on V-F conversion in the present invention. As shown in Fig. 3, the 2FSK modulation circuit of a kind of V-F conversion of the present invention comprises integral circuit 10, hysteresis comparator 20, discharge switch circuit 30, sine wave shaping circuit 40, and integral circuit 10 is composed of resistance R1, R3-4, electric capacity Composed of C1 and comparator U1, used to generate a triangular wave output proportional to the first input control voltage, the hysteresis comparator 20 is composed of resistors R6, R7 and comparator U2, used to convert the triangular wave output by the integrating circuit 10 into a square Wave output to control the discharge switch circuit 30, the discharge switch circuit 30 is composed of resistors R5, R2 and transistor Q1, used to regularly discharge the integral capacitor C1 of the integral circuit 10 under the control of the hysteresis comparator 20, the sine wave shaping circuit 40 It is composed of resistors R8-15, R18, variable resistors R16-17 (respectively the first variable resistor and the second variable resistor), NPN pair tube Q2-3 and PNP pair tube Q4-5, of which PNP pair tube Q4 -5 and resistor R8-9 form a mirror constant current source (proportional current source), NPN pair tube Q2-3 and resistor R10-11 form a differential amplifier, which is used to convert the triangular wave into a continuous phase sine wave, and C2 is a DC blocking capacitor . If the first input control voltage V4 is replaced by digital "0" and "1" series, the collector of the NPN transistor Q3 can output a modulated continuous-phase sine wave 2FSK voltage.

电阻R3、电容C1和比较器U1组成积分器之积分电路，R3一端连接第一输入控制电压V4，另一端接电容C1和比较器U1的反相输入端，C1另一端接比较器U1之输出端，V4为第一输入控制电压，其经电阻R4、R1分压后得到电压Vp1，该电压Vp1接入比较器U1之同相输入端以控制积分器的积分时间，电阻R2和三极管Q1组成积分电路的放电通道，比较器U1输出为充放电电压，该电压近似为一三角波(当时间常数R3×C1较大时)，该三角波一路接至电阻R6、R7和比较器U2组成的迟滞比较器的反相输入端，电阻R6一端接第二控制电压V2，另一端接电阻R7和比较器U2之同相输入端，电阻R7另一端接比较器U2之输出端，比较器U2之输出经电阻R5连接至三极管Q1的基极，三极管Q1发射极接地，其集电极经电阻R2连接至比较器U1之反相输入端，比较器U1输出之三角波另一路经隔直电容C2后连接至正弦波整形电路之输入端即电阻R15之一端，电阻R15另一端接可变电阻R17之可变电阻端，可变电阻R17之可变电阻端和一端短接而另一端接NPN三极管Q2基极和电阻R13之一端，可变电阻R16接在VCC和地间，在其可变电阻端输出一偏置电压，该偏置电压经电阻R14连接至NPN三极管Q2之基极使Q2工作于S形曲线的中心，NPN三极管Q2和Q3发射极通过等值电阻R10、R11连接至电阻R12之一端，电阻R12之另一端接负电源VEE，NPN三极管Q2之集电极接PNP三极管Q4之基极和集电极，NPN三极管Q3之集电极接PNP三极管Q5之集电极和电阻R18之一端，电阻R18另一端和NPN三极管Q3之基极接地，PNP三极管Q4和Q5的基极背靠背连接，PNP三极管Q4和Q5的发射极分别通过等值电阻R8、R9连接至正电源VCC。Resistor R3, capacitor C1, and comparator U1 form an integrating circuit of the integrator. One end of R3 is connected to the first input control voltage V4, the other end is connected to capacitor C1 and the inverting input end of comparator U1, and the other end of C1 is connected to the output of comparator U1. terminal, V4 is the first input control voltage, which is divided by resistors R4 and R1 to obtain voltage Vp1, and this voltage Vp1 is connected to the non-inverting input terminal of comparator U1 to control the integration time of the integrator, resistor R2 and transistor Q1 form an integral In the discharge channel of the circuit, the output of the comparator U1 is the charging and discharging voltage, which is approximately a triangular wave (when the time constant R3×C1 is large), and the triangular wave is connected to the hysteresis comparator composed of resistors R6, R7 and comparator U2. One end of the resistor R6 is connected to the second control voltage V2, the other end is connected to the non-inverting input end of the resistor R7 and the comparator U2, the other end of the resistor R7 is connected to the output end of the comparator U2, and the output of the comparator U2 passes through the resistor R5 Connect to the base of the transistor Q1, the emitter of the transistor Q1 is grounded, and its collector is connected to the inverting input of the comparator U1 through the resistor R2. The input end of the circuit is one end of the resistor R15, the other end of the resistor R15 is connected to the variable resistor end of the variable resistor R17, the variable resistor end of the variable resistor R17 is shorted to one end and the other end is connected to the base of the NPN transistor Q2 and the resistor R13 At one end, the variable resistor R16 is connected between VCC and ground, and a bias voltage is output at the variable resistor end, which is connected to the base of the NPN transistor Q2 through the resistor R14 so that Q2 works in the center of the S-shaped curve , The emitters of NPN transistor Q2 and Q3 are connected to one end of resistor R12 through equivalent resistors R10 and R11, the other end of resistor R12 is connected to the negative power supply VEE, the collector of NPN transistor Q2 is connected to the base and collector of PNP transistor Q4, NPN The collector of transistor Q3 is connected to the collector of PNP transistor Q5 and one end of resistor R18, the other end of resistor R18 is grounded to the base of NPN transistor Q3, the bases of PNP transistors Q4 and Q5 are connected back to back, and the emitters of PNP transistors Q4 and Q5 Connect to the positive power supply VCC through equivalent resistors R8 and R9 respectively.

图4、图5、图6分别为本发明仿真结果的V-F转换结果、三角波输出及输出的2FSK信号。电路的ERC检查无误后，在2FSK调制电路的输入端，加入二进制序列“0101”，设定合适的偏置电压后，如图4所示，码元“1”和“0”对应输出2.5KHz和833Hz的矩形波，基本符合原理分析结果。积分电路输出的三角波如图5所示，与矩形波频率一致。经过三角波—正弦波变换后，输出的2FSK信号如图6所示，对应码元“1”和“0”分别输出2.5KHz和833Hz的正弦波，相位连续，波形过渡较平稳，振幅一致。Fig. 4, Fig. 5, Fig. 6 are the V-F conversion result of the simulation result of the present invention, triangular wave output and the 2FSK signal of output respectively. After the ERC check of the circuit is correct, add the binary sequence "0101" to the input terminal of the 2FSK modulation circuit, and set the appropriate bias voltage, as shown in Figure 4, the code elements "1" and "0" correspond to output 2.5KHz and 833Hz rectangular wave, basically in line with the principle analysis results. The triangular wave output by the integrating circuit is shown in Figure 5, which is consistent with the frequency of the rectangular wave. After the triangle wave-sine wave conversion, the output 2FSK signal is shown in Figure 6, corresponding to the code elements "1" and "0" respectively output 2.5KHz and 833Hz sine waves, the phase is continuous, the waveform transition is relatively smooth, and the amplitude is consistent.

通过仿真结果分析，本发明之2FSK调制电路在无外加频率源的情况下，对应基带信号“1”和基带信号“0”分别输出了两种频率的正弦波，并且相位连续，波形过渡较平滑，与电路理论分析相符，达到预期设计要求。Through the analysis of simulation results, the 2FSK modulation circuit of the present invention outputs sine waves of two frequencies respectively corresponding to the baseband signal "1" and the baseband signal "0" without an external frequency source, and the phase is continuous, and the waveform transition is relatively smooth , which is consistent with the theoretical analysis of the circuit and meets the expected design requirements.

综上所述，本发明一种基于V-F转换的2FSK调制电路通过设置控制电压的电平变化，使V-F转换电路输出在两种不同频率间变化的矩形波，并对V-F转换电路进行改进，根据控制电压的两种电平变化，随之输出在两种不同频率间变化的正弦波，一方面可以减少电路的复杂程度，让电路结构简洁，另一方面可以减少波形转换过程中的误差，提高了电路的精准性。In summary, a 2FSK modulation circuit based on V-F conversion in the present invention makes the V-F conversion circuit output a rectangular wave that changes between two different frequencies by setting the level change of the control voltage, and improves the V-F conversion circuit, according to Two levels of the control voltage change, and then output a sine wave that changes between two different frequencies. On the one hand, it can reduce the complexity of the circuit and make the circuit structure simple. On the other hand, it can reduce the error in the waveform conversion process and improve accuracy of the circuit.

上述实施例仅例示性说明本发明的原理及其功效，而非用于限制本发明。任何本领域技术人员均可在不违背本发明的精神及范畴下，对上述实施例进行修饰与改变。因此，本发明的权利保护范围，应如权利要求书所列。The above-mentioned embodiments only illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Any person skilled in the art can modify and change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be listed in the claims.

Claims

1. A 2FSK modulation circuit based on V-F conversion, comprising at least:

an integrating circuit for generating a triangular wave output proportional to the first input control voltage;

A hysteresis comparator is used to convert the triangular wave output by the integrating circuit into a square wave output to control the discharge switch circuit;

A discharge switch circuit, used to regularly discharge the integral capacitance of the integral circuit under the control of the hysteresis comparator;

A sine wave shaping circuit for converting the triangular wave into a phase continuous sine wave.

2. A kind of 2FSK modulation circuit based on V-F conversion as claimed in claim 1, characterized in that: the integrating circuit comprises a first resistor, a third resistor, a fourth resistor, a first capacitor and a first comparator, the first One end of the three resistors is connected to the first input control voltage, the other end is connected to the first capacitor and the inverting input end of the first comparator, the other end of the first capacitor is connected to the output end of the first comparator, and the first input control voltage A voltage is obtained after being divided by the fourth resistor and the first resistor, and the voltage is connected to the non-inverting input terminal of the first comparator to control the integration time of the integrating circuit. discharge voltage.

3. A 2FSK modulation circuit based on V-F conversion as claimed in claim 2, wherein one output of the first comparator is connected to the hysteresis comparator, and the other is connected to the sine wave shaping circuit.

4. A kind of 2FSK modulation circuit based on V-F conversion as claimed in claim 3, it is characterized in that: the discharge switch circuit comprises a second resistor, a fifth resistor and a first triode, and the emitter of the first triode Its collector is connected to the inverting input terminal of the first comparator through the second resistor, and its base is connected to the output terminal of the hysteresis comparator through the fifth resistor.

5. A kind of 2FSK modulation circuit based on V-F conversion as claimed in claim 4, it is characterized in that: this hysteresis comparator comprises the 6th resistor, the 7th resistor and the second comparator, this 6th resistor one end connects the second control voltage, the other end is connected to the seventh resistor and the non-inverting input end of the second comparator, the other end of the seventh resistor is connected to the output end of the second comparator, and the output of the second comparator is connected to the the base of the first triode.

6. A kind of 2FSK modulation circuit based on V-F transformation as claimed in claim 5, characterized in that: the sine wave shaping circuit comprises eighth to fifteenth resistors, eighteenth resistors, a first variable resistor, a second Variable resistor, second NPN transistor, third NPN transistor, fourth PNP transistor, fifth PNP transistor, one end of the fifteenth resistor is connected to the output end of the first comparator, and the other end is connected to the second variable resistor The variable resistor end, the variable resistor end of the second variable resistor is short-circuited with one end and the other end is connected to the base of the second NPN transistor and one end of the thirteenth resistor, and the first variable resistor is connected to the positive power supply and ground, output a bias voltage at its variable resistance end, the bias voltage is connected to the base of the second NPN transistor through the fourteenth resistor to make the second NPN transistor work in the center of the S-shaped curve , the emitters of the second NPN transistor and the third NPN transistor are connected to one end of the twelfth resistor through the tenth resistor and the eleventh resistor, the other end of the twelfth resistor is connected to a negative power supply, and the second NPN transistor The collector of the fourth PNP transistor is connected to the base and collector of the fourth PNP transistor, the collector of the third NPN transistor is connected to the collector of the fifth PNP transistor and one end of the eighteenth resistor, and the other end of the eighteenth resistor is connected to The base of the third NPN transistor is grounded, the bases of the fourth PNP transistor and the fifth PNP transistor are connected back to back, and the emitters of the fourth PNP transistor and the fifth PNP transistor pass through the eighth resistor and the ninth resistor respectively. The resistor is connected to the positive supply.

7. A 2FSK modulation circuit based on V-F conversion as claimed in claim 6, wherein the output of the first comparator is connected to one end of the fifteenth resistor via a DC blocking capacitor.

8. A 2FSK modulation circuit based on V-F conversion as claimed in claim 6, characterized in that: the tenth resistor and the eleventh resistor are equivalent resistors, and the eighth resistor and the ninth resistor are equivalent resistance.