CN1756072B - Non-perfect carrier amplitude demodulation method and its device - Google Patents

Non-perfect carrier amplitude demodulation method and its device Download PDF

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CN1756072B
CN1756072B CN 200410066918 CN200410066918A CN1756072B CN 1756072 B CN1756072 B CN 1756072B CN 200410066918 CN200410066918 CN 200410066918 CN 200410066918 A CN200410066918 A CN 200410066918A CN 1756072 B CN1756072 B CN 1756072B
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王祥莉
韩明
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Shanghai Beiling Co Ltd
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Abstract

The invention relates to a amplitude demodulation method of non-ideal carrier wave which follows the step that multiplying the modulated signal and the carrier wave signal to realize the modulation, and comprises following steps: the first channel multiplies the modulates signal with carrier wave signal again to be output via the low-pass filter, and using said output signal as dividend; at the same time, the second channel squares the carrier wave signal to be output via the low-pass filter and using said output signal as divisor; at last, dividing the signals of said two channels in the divider to realize the amplitude demodulation of non-ideal carrier wave. The invention comprises the advantages that: it can realize the amplitude demodulation of non-ideal carrier wave; when the carrier wave is ideal, the invention also can realize the amplitude demodulation; the total structure of amplitude demodulation circuit is simple and easily to be realized and The invention can both apply the analog signal processing system and the digital signal processing system.

Description

A kind of amplitude demodulation method of non-perfect carrier and device thereof
Technical field
The present invention relates to a kind of amplitude demodulation method and device thereof of non-perfect carrier.
Background technology
In signal amplitude modulation field, usually carrier wave is a single high-frequency signal, and the amplitude of carrier wave under the ideal situation, frequency are constant, the same carrier wave of modulation and demodulation.But in the practical application, what be used as carrier wave may not be an ideal signal, can regard the interference signal that contains low frequency in the useful high-frequency signal as.
If according to desirable amplitude modulation(PAM) demodulation, as shown in Figure 1, suppose that modulated signals is A 0+ Asin (2 π f 0T), wherein: A is the interchange amplitude of modulated signals, and A0 is the direct current amplitude of modulated signals, and f0 is the frequency of modulated signals, and t is the time; Carrier signal is Bsin (2 π fmt), wherein fm＞＞f0, B is the interchange amplitude of carrier signal, fm is the frequency of carrier signal.Modulated signals and carrier signal multiplied each other in multiplier 200 carry out amplitude modulation(PAM), the signal after obtaining modulating is [A 0+ Asin (2 π f 0T)] * Bsin (2 π f mT)=A 0Bsin (2 π f mT)+(AB/2) { cos[2 π (f m+ f 0) t]-cos[2 π (f m-f 0) t], so just the amount of information of needs is modulated to high frequency and transmits.
In amplitude demodulation device 100 ', modulated signal and carrier signal are multiplied each other [A in multiplier 11 0+ Asin (2 π f 0T)] * Bsin (2 π f mT) * Bsin (2 π f mT)=(A 0B 2/ 2) { cos[2 π (2f m) t]-cos[2 π (0) t]+(AB 2/ 4) { sin[2 π (2f m+ f 0) t]+sin[2 π (f 0) t]+sin[2 π (f 0) t]+sin[2 π (2f m-f 0) t], the amount of information of Xu Yaoing is separated and is transferred to low frequency like this, and unnecessary high fdrequency component is passed through low pass filter 12 with its elimination.
See also Fig. 2, summarized the amplitude modulation(PAM) demodulating process with frequency spectrum.The frequency spectrum of modulated signals is at low frequency (f 0) and the direct current place; The frequency spectrum of carrier signal is at high frequency (f m) locate; After modulation signal and carrier signal multiplied each other, the signal spectrum that obtains was at high frequency (f mAnd f m± f 0) locate, promptly finished modulation function, the modulated signals of low frequency is modulated to high frequency; With the signal after the modulation with after carrier signal multiplies each other once more, the signal spectrum that obtains is at high frequency (2f mAnd 2f m± f 0) locate and low frequency (direct current and ± f 0) locate, by low pass filter, the elimination HFS stays low frequency part, has promptly finished demodulation function, signal after the modulation of high frequency is separated be transferred to low frequency, obtains original modulated signals with this signal.
The hypothesis modulated signals is A in the above-mentioned application 0+ Asin (2 π f 0T), and carrier wave is not the signal of a single high frequency, can regard a desirable carrier signal Bsin (2 π f as mT) by the signal [C of a low frequency 0+ Csin (2 π f 1T)] modulation, wherein f m＞＞f 0, f 1≈ f 0, C0 ≈ B, C are the interchange amplitude of this low frequency signal, and C0 is the direct current amplitude of this low frequency signal, and f1 is the frequency of this low frequency signal.After common amplitude modulation(PAM) demodulation, the signal that obtains low frequency (direct current, ± f0 and ± f1) locate, that is to say that the signal that demodulation is come out has the amount of information that needs, and unnecessary carrier wave medium and low frequency component is also arranged, and then can't realize demodulation function.
Summary of the invention
The object of the present invention is to provide a kind of simple in structure, the amplitude demodulation method of the non-perfect carrier that is easy to realize and device thereof.
The amplitude demodulation method of a kind of non-perfect carrier provided by the present invention, its continue modulated signals and carrier signal multiply each other realize modulation step after, its characteristics are, comprise following demodulation step: the signal after first passage will be modulated is by multiplying each other once more with carrier signal, and by low-pass filter output signal, this output signal is standby as dividend; Simultaneously, second channel with the carrier signal involution after, by low-pass filter output signal, that this output signal is standby as divisor; At last first passage low-pass filter output signal and second channel low-pass filter output signal are divided by in divider, realize the amplitude demodulation of non-perfect carrier.
In the amplitude demodulation method of above-mentioned non-perfect carrier, before carrying out demodulation step, analog signal after the modulation that will import and analog carrier signal and suppress low frequency component in the signal by high pass filter from the analog signal conversion to the digital signal earlier.
The present invention also provides a kind of amplitude demodulation device of non-perfect carrier, its external modulating device, comprise first branch road, i.e. first multiplier and a low pass filter that links to each other with this first multiplier, the input signal of first multiplier is signal and carrier signal after modulating, its characteristics are that it also comprises second branch road identical and in parallel with this first branch road, and a divider; Wherein: second branch road, i.e. second multiplier and second low pass filter that links to each other with this second multiplier, with carrier signal by the second multiplier involution after by second low-pass filter output signal; This divider respectively with first branch road on first low pass filter link to each other with second low pass filter on second branch road, and with the signal of first low pass filter on first branch road output as dividend, with the signal of second low pass filter on second branch road output as divisor, in divider, be divided by, realize the amplitude demodulation of non-perfect carrier.
The amplitude demodulation device of above-mentioned non-perfect carrier also comprises first A/D converter, second A/D converter, first high pass filter and second high pass filter; The input signal of first A/D converter is the analog signal after modulating, and the output of first A/D converter links to each other with the input of first high pass filter, and the output of first high pass filter links to each other with an input of first multiplier; The input signal of second A/D converter is a carrier signal, the output of second A/D converter links to each other with the input of second high pass filter, and the output of second high pass filter links to each other with another input of first multiplier and two inputs of second multiplier.
Owing to adopted technique scheme, make it compared with prior art, have the following advantages and good effect: under the situation of non-perfect carrier, realize amplitude demodulation; When carrier wave was ideal situation, the present invention can realize amplitude demodulation equally; Whole amplitude demodulation circuit simple in structure is easy to realize; The present invention all is suitable for analog system and digital information processing system.
Description of drawings
Embodiment by following amplitude demodulation method to a kind of non-perfect carrier of the present invention can further understand purpose of the present invention, specific structural features and advantage in conjunction with the description of its accompanying drawing.Wherein, accompanying drawing is:
Fig. 1 is desirable demodulation structure schematic diagram;
Fig. 2 is desirable modulation spectrum diagram;
Fig. 3 is the demodulation structure schematic diagram of imperfect carrier wave;
Fig. 4 (a) and Fig. 4 (b) are respectively that the modulation spectrum schematic diagram of imperfect carrier wave is conciliate frequency modulation spectrum schematic diagram;
Fig. 5 is the specific embodiment of the invention (being applied to digital information processing system)
Embodiment
The amplitude demodulation method of a kind of non-perfect carrier of the present invention, its continue modulated signals and carrier signal multiply each other realize modulation step after, comprise following demodulation step:
A channel, the signal after the modulation is by multiplying each other once more with carrier signal, and by low-pass filter output signal, standby as dividend with this output signal; Simultaneously,
The B passage, after the carrier signal involution,, that this output signal is standby as divisor by low-pass filter output signal;
Signal with two passages is divided by in divider 3 at last, realizes the amplitude demodulation of non-perfect carrier.
As shown in Figure 3, in modulating part, modulated signals and carrier signal multiply each other in multiplier 200 and realize modulation.The present invention, it is the amplitude demodulation device 100 of non-perfect carrier, comprise first branch road, be a multiplier 11 and a low pass filter 12 that links to each other with this multiplier 11, signal and carrier signal after the modulation are multiplied each other in multiplier 11 once more, and, be characterized in by low pass filter 12 output signals, it also comprises second branch road identical and in parallel with this first branch road, and a divider 3.
Second branch road, i.e. a multiplier 21 and a low pass filter 22 that links to each other with this multiplier 21, with carrier signal by multiplier 21 involutions after by low pass filter 22 output signals.
This divider 3 respectively with first branch road on low pass filter 12 link to each other with low pass filter 22 on second branch road, with the signal of the low pass filter on first branch road 12 output as dividend, with the signal of the low pass filter on second branch road 22 output as divisor, signal with two passages is divided by in divider 3 at last, realizes demodulation.
Multiplier 11 on first branch road is with modulated signal [A 0+ Asin (2 π f 0T)] * { Bsin (2 π f mT) * [C 0+ Csin (2 π f 1T)] } with carrier wave Bsin (2 π f mT) * [C 0+ Csin (2 π f 1T)] multiply each other, the signal that obtains is [A 0+ Asin (2 π f 0T)] * { Bsin (2 π f mT) * [C 0+ Csin (2 π f 1T)] } * { Bsin (2 π f mT) * [C 0+ Csin (2 π f 1T)] }, i.e. (A 0B 2/ 4-A 0B 2C 0 2/ 2)-(A 0B 4C 0 2/ 2) sin (2 π f 1T)-(A 0B 2/ 4) cos[2 π (2f 1) t]+(A 0B 2C 0 2/ 2-A 0B 2/ 4) cos[2 π (2f m) t]+(A 0B 2C 0/ 2) { sin[2 π (2f m+ f 1) t]-sin[2 π (2f m-f 1) t]+(A 0B 2/ 8) { cos[2 π (2f m+ 2f 1) t]+cos[2 π (2f m-2f 1) t]+(AB 2/ 4-AB 2C 0 2/ 2) sin (2 π f 0T)-(AB 4C 0 2/ 4) { cos[2 π (f 0+ f 1) t]+cos[2 π (f 0-f 1) t]-(AB 2/ 8) { sin[2 π (f 0+ 2f 1) t]-sin[2 π (f 0-2f 1) t]+(AB 2C 0 2/ 4-AB 2/ 8) { sin[2 π (2f m+ f 0) t]-sin[2 π (2f m-f 0) t]+(AB 2C 0/ 4) { cos[2 π (2f m+ f 1+ f 0) t]-cos[2 π (2f m+ f 1-f 0) t]-cos[2 π (2f m-f 1+ f 0) t]+cos[2 π (2f m-f 1-f 0) t]+(AB 2/ 16) { sin[2 π (2f m+ 2f 1+ f 0) t]-sin[2 π (2f m+ 2f 1-f 0) t]+sin[2 π (2f m-2f 1-f 0) t]-sin[2 π (2f m-2f 1+ f 0) t];
Multiplier 21 on second branch road is the carrier wave involution, the signal that obtains { Bsin (2 π f mT) * [C 0+ Csin (2 π f 1T)] } * { Bsin (2 π f mT) * [C 0+ Csin (2 π f 1T)] }, i.e. (B 2/ 4-B 2C 0 2/ 2)-(B 4C 0 2/ 2) sin (2 π f 1T)-(B 2/ 4) cos[2 π (2f 1) t]+(B 2C 0 2/ 2-B 2/ 4) cos[2 π (2f m) t]+(B 2C 0/ 2) { sin[2 π (2f m+ f 1) t]-sin[2 π (2f m-f 1) t]+(B 2/ 8) { cos[2 π (2f m+ 2f 1) t]+cos[2 π (2f m-2f 1) t].
Multiplier 11 output signals by low pass filter 12, are suppressed its high fdrequency component, obtain (A 0B 2/ 4-A 0B 2C 0 2/ 2)-(A 0B 4C 0 2/ 2) sin (2 π f 1T)-(A 0B 2/ 4) cos[2 π (2f 1) t]+(AB 2/ 4-AB 2C 0 2/ 2) sin (2 π f 0T)-(AB 4C 0 2/ 4) { cos[2 π (f 0+ f 1) t]+cos[2 π (f 0-f 1) t]-(AB 2/ 8) { sin[2 π (f 0+ 2f 1) t]-sin[2 π (f 0-2f 1) t];
Multiplier 21 output signals by low pass filter 22, are suppressed its high fdrequency component, obtain (B 2/ 4-B 2C 0 2/ 2)-(B 4C 0 2/ 2) sin (2 π f 1T)-(B 2/ 4) cos[2 π (2f 1) t].
Two repressed signals of high frequency are divided by, have just obtained the amount of information [A that needs 0+ Asin (2 π f 0T)], realized function to non-perfect carrier digitlization amplitude demodulation.
Fig. 4 (a) is the modulation spectrum schematic diagram of imperfect carrier wave.The frequency spectrum of modulated signals is at low frequency (f 0) and the direct current place; Carrier signal can regard as one desirable, frequency spectrum is at high frequency (f m) signal located and frequency spectrum low frequency (direct current and ± f 1) signal multiplication located, its frequency spectrum of actual carrier signal after multiplying each other is at high frequency (f mAnd f m± f 1) locate; After modulation signal and carrier signal multiplied each other, the signal spectrum that obtains was at high frequency (f m, f m± f 0, f m± f 1And f m± f 0± f 1) locate, promptly finished modulation function, the modulated signals of low frequency is modulated to high frequency.
Fig. 4 (b) is the demodulation spectrum diagram of imperfect carrier wave.After signal after passage A will modulate and carrier signal multiplied each other once more, the signal spectrum that obtains was at high frequency (2f m, 2f m± f 0, 2f m± f 1, 2f m± 2f 1, 2f m± f 0± f 1, and 2f m± 2f 1± f 0) locate and low frequency (direct current, f 1, 2f 1, f 0, f 0± f 1And f 0± 2f 1) locate, by low pass filter, the elimination HFS stays low frequency part with this signal; Channel B is with the carrier signal involution, and the signal spectrum that obtains is at high frequency (2f m, 2f m± f 1And 2f m± 2f 1) locate and low frequency (direct current, f 1And 2f 1) locate, by low pass filter, the elimination HFS stays low frequency part with this signal; Signal with two passages is divided by at last, has promptly finished demodulation function, signal after the modulation of high frequency is separated be transferred to low frequency, and the frequency spectrum of signal is at low frequency (f 0) and the direct current place, obtain original modulated signals.
When the design sensor detection circuit, general carrier wave is not a desired carrier signal, uses the modulation function that the present invention has realized non-perfect carrier, has reached the circuit design requirement.
If in sensor detection circuit, what need demodulation is the tolerance signal of a low frequency (dominant frequency is approximately 50Hz), comprise high frequency (dominant frequency the is 2.9KHz) signal that low frequency (about 10Hz) disturbs and be one, can not obtain the tolerance signal of needs with the method for common desirable carrier wave demodulation as the drive signal of carrier wave.
Referring to shown in Figure 5, can be in the amplitude demodulation device earlier the modulated tolerance signal of input and drive signal respectively in mould/number conversion module 13,23 from the analog signal conversion to the digital signal, and by the low frequency component in two signals of high pass filter 14,24 inhibition, use the demodulation structure 100 of non-perfect carrier of the present invention again, realize the modulation function of digitized non-perfect carrier, finished the sensor detection circuit design.

Claims (4)

1. the amplitude demodulation method of a non-perfect carrier, its continue modulated signals and carrier signal multiply each other realize modulation step after, it is characterized in that, comprise following demodulation step:
Signal after first passage will be modulated is by multiplying each other once more with carrier signal, and by low-pass filter output signal, this output signal is standby as dividend; Simultaneously,
Second channel with the carrier signal involution after, by low-pass filter output signal, that this output signal is standby as divisor;
At last first passage low-pass filter output signal and second channel low-pass filter output signal are divided by in divider, realize the amplitude demodulation of non-perfect carrier.
2. the amplitude demodulation method of non-perfect carrier according to claim 1, it is characterized in that: before carrying out demodulation step, analog signal after the modulation that will import and analog carrier signal be from the analog signal conversion to the digital signal earlier, and suppress low frequency component in the signal by high pass filter.
3. the amplitude demodulation device of a non-perfect carrier, its external modulating device, comprise first branch road, i.e. first multiplier (11) and first low pass filter (12) that links to each other with this first multiplier (11), the input signal of described first multiplier (11) is signal and carrier signal after modulating, it is characterized in that it also comprises second branch road identical and in parallel with this first branch road, and a divider (3); Wherein:
Second branch road, i.e. second multiplier (21) and second low pass filter (22) that links to each other with this second multiplier (21), with carrier signal by second multiplier (21) involution after by second low pass filter (22) output signal;
This divider (3) respectively with first branch road on first low pass filter (12) link to each other with second low pass filter (22) on second branch road, and with the signal of first low pass filter (12) on first branch road output as dividend, with the signal of second low pass filter (22) on second branch road output as divisor, in divider (3), be divided by, realize the amplitude demodulation of non-perfect carrier.
4. the amplitude demodulation device of non-perfect carrier according to claim 3 is characterized in that: also comprise first A/D converter (13), second A/D converter (23), first high pass filter (14) and second high pass filter (24); The input signal of described first A/D converter (13) is the analog signal after modulating, the output of first A/D converter (13) links to each other with the input of described first high pass filter (14), and the output of first high pass filter (14) links to each other with an input of described first multiplier (11); The input signal of described second A/D converter (23) is a carrier signal, the output of second A/D converter (23) links to each other with the input of described second high pass filter (24), and the output of second high pass filter (24) links to each other with another input of described first multiplier (11) and two inputs of second multiplier (21).
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1032474A (en) * 1987-09-25 1989-04-19 菲利浦光灯制造公司 Carrier recovery circuit in the digital transmission system
CN1152210A (en) * 1995-08-22 1997-06-18 松下电器产业株式会社 Demodulation method and device
US6580314B1 (en) * 2000-10-11 2003-06-17 The United States Of America As Represented By The Secretary Of The Navy Demodulation system and method for recovering a signal of interest from a modulated carrier sampled at two times the phase generated carrier frequency

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1032474A (en) * 1987-09-25 1989-04-19 菲利浦光灯制造公司 Carrier recovery circuit in the digital transmission system
CN1152210A (en) * 1995-08-22 1997-06-18 松下电器产业株式会社 Demodulation method and device
US6580314B1 (en) * 2000-10-11 2003-06-17 The United States Of America As Represented By The Secretary Of The Navy Demodulation system and method for recovering a signal of interest from a modulated carrier sampled at two times the phase generated carrier frequency

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