CN103872989B - Am signals demodulator circuit - Google Patents
Am signals demodulator circuit Download PDFInfo
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- CN103872989B CN103872989B CN201210548292.3A CN201210548292A CN103872989B CN 103872989 B CN103872989 B CN 103872989B CN 201210548292 A CN201210548292 A CN 201210548292A CN 103872989 B CN103872989 B CN 103872989B
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Abstract
The invention discloses a kind of am signals demodulator circuit, including：One average detection circuit, for detecting the average value V of am signals, its output end is connected with the reverse input end of comparator；One level shift circuit, for being shifted to the instantaneous value V+ of am signals, its output end is connected with the comparator positive input；Envelope signal is separately input to the input of the average detection circuit and level shift circuit；The demodulated signal that the comparator is exported after being compared to the instantaneous value V+ of the am signals and the average value V of am signals.The present invention can more significantly improve demodulation ability and antijamming capability.
Description
Technical field
The present invention relates to signal to demodulate field, more particularly to a kind of am signals demodulator circuit.
Background technology
Am signals demodulator circuit is typically by detecting am signals instantaneous value（That is envelope signal instantaneous value）
Difference between average value judges whether signal is modulated.Traditional demodulator circuit is as shown in figure 1, the envelope letter of input
Number instantaneous value is obtained after processing（Peak value）V+ and average value V-, by one with sluggishness comparator come compare instantaneous value V+ and
Average value V- difference.When being modulated without am signals, instantaneous value V+ and average value V- are of substantially equal, the high electricity of comparator output
It is flat；When am signals are modulated, instantaneous value V+ rapid decreases and average value slowly declines, as instantaneous value V+ and average value V-
Difference when exceeding comparator threshold, comparator output step-down, until modulation terminates, instantaneous value V+ is climbed to again to be exceeded
Or the high level before modulation is returned again close to average value V-, comparator output, modulated signal is detected.
But there is both sides in this demodulator circuit：First, antijamming capability is seriously asymmetric, during modulation
When a negative interference occur in am signals, as long as interference magnitude is no more than the demodulation threshold of comparator, it would not cause
Misread and adjust, and during modulation（Instantaneous value is low）When there is a positive pulse so that average value V- and instantaneous value V+'s is poor small
In the demodulation threshold of comparator, comparator output will return to the high level before modulation so that demodulated signal width is less than actual
Modulated signal.Second, working as modulated signal narrower bandwidth, it is demodulated in order to avoid the change of strength of carrier is taken as modulated signal,
The time constant of average value signal typically can not set too big, so when am signals pulsewidth is wider, average value letter
Number instantaneous value can be reduced close to quickly, at this moment comparator output can also return to high level, cause to misread and adjust.For solution asking above
Topic, there are many follow-on average value demodulator circuits, such as using the sluggish comparator structure of two-way tape, but these are improved
Type circuit generally there are the deficiencies of circuit structure is more complicated, and parameter designing adjustment is inconvenient.
The content of the invention
The technical problem to be solved in the present invention is to provide a kind of am signals demodulator circuit, can more significantly improve
Demodulation ability and antijamming capability.
In order to solve the above technical problems, the am signals demodulator circuit of the present invention, including：
One average detection circuit, for detecting the average value V- of am signals, its output end and comparator it is anti-
It is connected to input；
One level shift circuit, for being shifted to the instantaneous value V+ of am signals, its output end and the ratio
It is connected compared with device positive input；
Envelope signal is separately input to the input of the average detection circuit and level shift circuit；
The comparator compares the instantaneous value V+ of the am signals and the average value V- of am signals
The demodulated signal exported more afterwards.
The present invention realizes that new amplitude modulation(PAM) is believed by simplest comparator, resistance and current source, digital feedback combination
Number demodulator circuit, compared with traditional am signals demodulator circuit, there is simple circuit, higher bandwidth, higher anti-
It the features such as jamming performance, adjusting thresholds facilitate, can substantially optimize demodulation characteristics, improve RF（Radio frequency）Chip performance, but also can
More to save chip area.
Brief description of the drawings
The present invention is further detailed explanation with embodiment below in conjunction with the accompanying drawings：
The existing am signals demodulator circuit schematic diagram that Fig. 1 is；
Fig. 2 is the embodiment schematic diagram of am signals demodulator circuit one of the present invention.
Embodiment
Am signals demodulator circuit shown in Figure 2, of the invention, in the following embodiments, including：One is average
Value detection circuit, a level shift circuit and a comparator.
Envelope signal is separately input to the input of the average detection circuit and level shift circuit.
The average detection circuit, for detecting the average value V- of am signals, its output end and the comparison
Device reverse input end is connected.
The level shift circuit, for being shifted to the instantaneous value V+ of am signals, its output end with it is described
Comparator positive input is connected.
The comparator compares the instantaneous value V+ of the am signals and the average value V- of am signals
The demodulated signal exported more afterwards.
It is 1 in the output of the comparator, i.e., when unmodulated, control level shift circuit makes instantaneous value V+ than true envelope
The high level of signal, accordingly even when envelope signal is more lower slightly than average value V- but not up to demodulation threshold, the comparator it is defeated
Going out will not also overturn as 0；It is 0 in the output of the comparator, that is, when modulating, control level shift circuit makes instantaneous value V+ than true
The low level of real envelope signal, accordingly even when envelope signal is more slightly higher than average value V-, but as long as not up to demodulation threshold, described
The output of comparator will not be also overturn as 1.Therefore, level shift circuit can play jamproof effect.
The level shift circuit is made up of current source I0, resistance R0 and change-over switch S0, S1；Change-over switch S0, S1 are equal
It is in parallel for two-way.When change-over switch S0 is closed, one is formed from power supply to ground by current source I0, change-over switch S0, resistance R0
Path；When change-over switch S1 is closed, another is formed from power supply to ground by current source I0, change-over switch S1, resistance R0
Path.Current flowing resistance R0's is in opposite direction in the case of two kinds, wherein, power supply can be by envelope signal or suitable independent electrical
Source powers.
When demodulating beginning, the output of the comparator is set to original state 1, and change-over switch S1 closures, electric current is through turning
Change switch S1 and flow through resistance R0, produce voltage I0*R0, then the instantaneous value V+ of am signals lifted on the basis of envelope signal
High I0*R0, so unless envelope signal occurs being more than I0*R0The decline of amplitude, otherwise comparator will not overturn.Once envelope
Signal occurs being more than I0*R0The decline of amplitude thinks that, there occurs amplitude modulation(PAM), comparator output switching activity is 0, while change-over switch
S1 disconnects, and change-over switch S0 closures, electric current flows through resistance R in opposite direction0, again so that the instantaneous value V+ of am signals
I has been dragged down on the basis of envelope signal0*R0, so, during modulation, even if the average value V- of am signals is at any time
Between be slowly declined to it is high as the instantaneous value V+ of am signals, or even occur be slightly above am signals instantaneous value
V+ interference, as long as | V--V+ | less than I0*R0, comparator output will not also be overturn, until modulated signal terminates.Due to demodulation
Threshold value and I0*R0It is linear, as long as suitably adjustment constant-current source I0Or resistance R0Size, just can easily adjust demodulator
Threshold value." * " represents multiplication sign in above-mentioned.
Although the present invention is illustrated using specific embodiment, the present invention's is not intended to limit to the explanation of embodiment
Scope.One skilled in the art is by reference to explanation of the invention, without departing substantially from the spirit and scope of the present invention
In the case of, easily carry out various modifications or embodiment can be combined.
Claims (3)
- A kind of 1. am signals demodulator circuit, it is characterised in that including：One average detection circuit, for detecting the average value V- of am signals, its output end and comparator it is reverse defeated Enter end to be connected；One level shift circuit, for being shifted to the instantaneous value V+ of am signals, its output end and the comparator Positive input is connected；Envelope signal is separately input to the input of the average detection circuit and level shift circuit；After the comparator is compared to the instantaneous value V+ of the am signals and the average value V- of am signals The demodulated signal exported.
- 2. am signals demodulator circuit as claimed in claim 1, it is characterised in that the level shift circuit is by an electricity Liu Yuan, a resistance, the first change-over switch and the second change-over switch are formed, and the first change-over switch and the second change-over switch are two-way It is in parallel；When the first change-over switch closes, leading to from power supply to ground is formed by current source, the first change-over switch and resistance Road；When the second change-over switch closes, another leading to from power supply to ground is formed by current source, the second change-over switch and resistance Road；Current flowing resistance is in opposite direction in the case of two kinds；Wherein power supply can by envelope signal or suitable independent current source Lai Power supply.
- 3. am signals demodulator circuit as claimed in claim 1 or 2, it is characterised in that：In the output of the comparator For 1, i.e., when unmodulated, control level shift circuit makes an instantaneous value V+ level higher than true envelope signal；In the comparison The output of device is 0, that is, when modulating, control level shift circuit makes an instantaneous value V+ level lower than true envelope signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201210548292.3A CN103872989B (en) | 2012-12-17 | 2012-12-17 | Am signals demodulator circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201210548292.3A CN103872989B (en) | 2012-12-17 | 2012-12-17 | Am signals demodulator circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN103872989A CN103872989A (en) | 2014-06-18 |
| CN103872989B true CN103872989B (en) | 2018-02-13 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201210548292.3A Active CN103872989B (en) | 2012-12-17 | 2012-12-17 | Am signals demodulator circuit |
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Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104486269B (en) * | 2014-12-30 | 2018-02-16 | 广州极汇信息科技有限公司 | Index of modulation automatic circuit |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1289188A (en) * | 1999-09-22 | 2001-03-28 | 松下电子工业株式会社 | Non-contact type IC card preventing data from error restoring while AM wave-carrier demodulation |
| CN1988523A (en) * | 2005-12-21 | 2007-06-27 | 上海贝岭股份有限公司 | Demodulating method and its circuit for amplitude modulation signal |
| CN102075144A (en) * | 2010-12-30 | 2011-05-25 | 天津南大强芯半导体芯片设计有限公司 | Electronic tag demodulation circuit |
| CN102111108A (en) * | 2009-12-24 | 2011-06-29 | 上海华虹集成电路有限责任公司 | Demodulation circuit for amplitude keying modulation signals |
| CN102810180A (en) * | 2012-07-04 | 2012-12-05 | 广州中大微电子有限公司 | ASK (Amplitude Shift Keying) demodulation circuit with wide demodulation range used for passive RFID (Radio Frequency Identification) label chips |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4706761B2 (en) * | 2009-01-29 | 2011-06-22 | 日本テキサス・インスツルメンツ株式会社 | Receiver circuit |
-
2012
- 2012-12-17 CN CN201210548292.3A patent/CN103872989B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1289188A (en) * | 1999-09-22 | 2001-03-28 | 松下电子工业株式会社 | Non-contact type IC card preventing data from error restoring while AM wave-carrier demodulation |
| CN1988523A (en) * | 2005-12-21 | 2007-06-27 | 上海贝岭股份有限公司 | Demodulating method and its circuit for amplitude modulation signal |
| CN102111108A (en) * | 2009-12-24 | 2011-06-29 | 上海华虹集成电路有限责任公司 | Demodulation circuit for amplitude keying modulation signals |
| CN102075144A (en) * | 2010-12-30 | 2011-05-25 | 天津南大强芯半导体芯片设计有限公司 | Electronic tag demodulation circuit |
| CN102810180A (en) * | 2012-07-04 | 2012-12-05 | 广州中大微电子有限公司 | ASK (Amplitude Shift Keying) demodulation circuit with wide demodulation range used for passive RFID (Radio Frequency Identification) label chips |
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| CN103872989A (en) | 2014-06-18 |
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