CN106789787B - A kind of PCM/DPSK/FM modulation /demodulation module and method - Google Patents
A kind of PCM/DPSK/FM modulation /demodulation module and method Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
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Abstract
The invention discloses a kind of PCM/DPSK/FM modulation /demodulation module and method, the module includes modulation and demodulation module, and transmission information code is carried out pulse code modulation first by modulation module, and the subcarrier for then carrying out DPSK to pulse code modulation signal is modulated.FM modulation is carried out to DPSK modulated signal again, finally obtains dual modulation signal.Demodulation module carries out lower side frequency to the signal received first and extraction is handled, and then carries out FM demodulation to the signal for reducing rate, saves hardware resource.FM demodulation module output signal enters DPSK demodulation module, carries out front and back symbol phases to DPSK modulated signal and compares, to demodulate modulation intelligence.Last DPSK demodulated signal enters bit timing module, optimal determination point is obtained, to demodulate transmission information.The present invention substantially reduces the bit error rate, improves system performance.
Description
Technical field
The present invention relates to peaces to control the communications field, in particular to a kind of PCM/DPSK/FM modulation /demodulation FPGA implementation method.
Background technique
As international community is military, the development of politics, economic situation, the requirement to Safety system is higher and higher.From China
Current peace control signal sees that rate is usually relatively low, generally at several hundred bps to tens kilobits/second, the signal band of occupancy
Width is narrow, and the Doppler shift maximum as caused by spacecraft movement can reach several hundred kHz, have exceeded signal already
Bandwidth range.If directlying adopt PSK modulation, receiver can not carry out trace demodulation to signal.Even if there is part using FM/
DPSK secondary modulation is also mostly the implementation method of half simulation Semi-digital, and data processing is more difficult, and development difficulty is big.With
The development of the peace control communications field, this modulation system have been unable to satisfy the demand of people.
Summary of the invention
The invention proposes a kind of PCM/DPSK/FM modulation /demodulation module and methods.
The technical solution for realizing the aim of the invention is as follows: a kind of PCM/DPSK/FM modulation /demodulation module, including modulation mould
Block and demodulation module two parts, the modulation module include sequentially connected pulse code modulation module, differential encoding module,
BPSK subcarrier modulation module and secondary FM modulation module, wherein pulse code modulation module is used for the safety control information that will be received
Pulse code is carried out, and the signal after coding is sent to BPSK subcarrier modulation module by differential encoding module, difference is compiled
Code module is used to carry out differential encoding to the signal after pulse code, after BPSK subcarrier modulation module is used for differential encoding
Signal carries out the subcarrier modulation of BPSK, and gives the modulated signal of output to secondary FM modulation module, secondary FM modulation module
For carrying out the secondary modulation of FM to BPSK modulated subcarrier signal；
Demodulation module includes down conversion module, CIC abstraction module, FM demodulation module, DPSK demodulation module, bit timing mould
Block；
Wherein down conversion module is used to reception signal frequency converting pass through CIC to zero-frequency, and by the signal after down coversion
Abstraction module gives FM demodulation module, and CIC abstraction module carries out 200 points of extraction to the signal after down coversion；FM demodulation module
Demodulation for carrying out FM to the signal after extraction obtains DPSK modulated subcarrier signal, and gives output signal to DPSK demodulation
Module；DPSK demodulation module is used to carry out differential ference spiral to input signal, and gives output signal to bit timing module；Bit timing
Module obtains optimal determination point, to demodulate safety control information for doing bit timing processing to the signal after differential ference spiral.
A kind of PCM/DPSK/FM modulation-demo-demodulation method based on above-mentioned PCM/DPSK/FM modulation /demodulation module, the modulation
Method the following steps are included:
Step 1 carries out pulse code modulation to safety control information；
Step 2 carries out the modulation of DPSK subcarrier to the signal after pulse code modulation, specifically: first to pulse code tune
Signal processed carries out differential encoding, then carries out bpsk signal modulation to the signal after differential encoding, and modulation carrier wave is a low frequency
Subcarrier signal；
Step 3 carries out secondary FM modulation to signal after the modulation of DPSK subcarrier, first carries out to DPSK modulated subcarrier signal
The signal of two branch of I, Q is added, then the signal of addition is multiplied a scale factor k, finally goes to control with the signal for multiplying scale factor
The frequency control word for making a DDS module obtains secondary FM modulated signal, will obtain final modulated signal and exports；
The demodulation method, comprising the following steps:
Step A, bandpass sampling is carried out to the intermediate-freuqncy signal received；
Step B, Digital Down Convert processing is carried out to the data after sampling, signal frequency is changed near zero-frequency, then under
Signal after side frequency carries out 200 point CIC filtering extractions, obtains I, Q two paths of signals；
Step C, the signal after extracting to CIC carries out FM demodulation, and FM demodulation carries out difference frequency discrimination using small angle approximation method,
To obtain the frequency information of signal, DPSK modulated signal is exported；
Step D, DPSK demodulation is carried out to obtained DPSK modulated signal, DPSK demodulation uses differential ference spiral, first solves to FM
It adjusts signal to carry out the processing of one symbol lengths of delay, then non-time delayed signal is multiplied with time delayed signal and carries out the phase of front and back symbol
Position comparison, to demodulate DPSK modulated subcarrier signal；
Step E, bit timing processing is carried out to DPSK demodulated signal, point eight tunnels first is carried out to DPSK demodulated signal and are added up,
In the different location in a symbol, accumulation length is the length of a symbol for cumulative starting point；And after adding up
Value is saved, and the frame head EB90 of accumulated value and information frame that eight tunnel Zai Dui saves carries out matching treatment, finds matching value maximum
All the way；Finally this road signal is exported, obtains safety control information.
Compared with prior art, the present invention its remarkable advantage are as follows: 1) present invention has abandoned traditional dual modulation demodulation
The implementation method of half simulation Semi-digital modulation /demodulation more meets the reality of software radio instantly using digital implementation method
Existing mode.It is short with the development cycle, it may modify the advantage strong with programmability.2) it avoids and adopts in FM demodulation module of the invention
With the conventional method for seeking phase by arctangent cp cp operation, but small angle approximation demodulation method is used, is extracted by difference frequency discrimination
Frequency information.3) DPSK demodulation module does not first pass through PSK demodulation, the rear method for carrying out code inverse transformation using traditional.But
Differential ference spiral is directly carried out, the method for differential ference spiral is the phase by comparing front and back symbol, to know its phase change.
Phase bit comparison is to carry out the realization that is multiplied with the signal for postponing a symbol to it by FM demodulated signal.4) timing module in order to
System reliability is improved, eight road signals have been separated.Every road signal adds up since the different initial positions of a symbol, and cumulative one
Saved after a symbol lengths it is cumulative after value, then matching treatment is done with safety control information frame frame head EB90 to the value of preservation, finds out
With maximum signal all the way is worth as final decision signal, the bit error rate can be substantially reduced in this way, improves system performance.
Detailed description of the invention
Fig. 1 is PCM/DPSK/FM modulation principle block diagram.
Fig. 2 is PCM/DPSK/FM demodulation principle block diagram.
Fig. 3 is difference frequency discrimination functional block diagram.
Fig. 4 is the FM demodulation waveforms figure that FPGA is realized.
Fig. 5 is DPSK demodulation principle block diagram.
Fig. 6 is bit timing realization principle block diagram.
Fig. 7 is the DPSK demodulation waveforms figure that FPGA is realized.
Specific embodiment
In conjunction with attached drawing, a kind of PCM/DPSK/FM modulation /demodulation module of the invention, including modulation module and demodulation module two
Part, the modulation module include sequentially connected pulse code modulation module, differential encoding module, BPSK subcarrier modulation mould
Block and secondary FM modulation module, wherein pulse code modulation module is used to the safety control information received carrying out pulse code, and
The signal after coding is sent to BPSK subcarrier modulation module by differential encoding module, differential encoding module is used for pulse
Signal after coding carries out differential encoding, and BPSK subcarrier modulation module is used to carry out the signal after differential encoding the pair of BPSK
Carrier modulation, and give the modulated signal of output to secondary FM modulation module, secondary FM modulation module is used for BPSK subcarrier
The secondary modulation of modulated signal progress FM；
Demodulation module includes down conversion module, CIC abstraction module, FM demodulation module, DPSK demodulation module, bit timing mould
Block；
Wherein down conversion module is used to reception signal frequency converting pass through CIC to zero-frequency, and by the signal after down coversion
Abstraction module gives FM demodulation module, and CIC abstraction module carries out 200 points of extraction to the signal after down coversion；FM demodulation module
Demodulation for carrying out FM to the signal after extraction obtains DPSK modulated subcarrier signal, and gives output signal to DPSK demodulation
Module；DPSK demodulation module is used to carry out differential ference spiral to input signal, and gives output signal to bit timing module；Bit timing
Module obtains optimal determination point, to demodulate safety control information for doing bit timing processing to the signal after differential ference spiral.
A kind of PCM/DPSK/FM modulation-demo-demodulation method based on above-mentioned PCM/DPSK/FM modulation /demodulation module, the modulation
Method the following steps are included:
Step 1 carries out pulse code modulation to safety control information；
Step 2 carries out the modulation of DPSK subcarrier to the signal after pulse code modulation, specifically: first to pulse code tune
Signal processed carries out differential encoding, then carries out bpsk signal modulation to the signal after differential encoding, and modulation carrier wave is a low frequency
Subcarrier signal；
DPSK subcarrier modulates formula used are as follows:
I (t)=a (t) cos (2 π f1t+θ)
Q (t)=a (t) sin (2 π f1t+θ)
In formula, i (t) is that DPSK modulates the road I signal, and q (t) is that DPSK modulates the road Q signal, and a (t) is to have carried out differential encoding
Safety control information, f1For subcarrier frequency, θ is subcarrier initial phase.
Step 3 carries out secondary FM modulation to signal after the modulation of DPSK subcarrier, first carries out to DPSK modulated subcarrier signal
The signal of two branch of I, Q is added, then the signal of addition is multiplied a scale factor k, finally goes to control with the signal for multiplying scale factor
The frequency control word for making a DDS module obtains secondary FM modulated signal, will obtain final modulated signal and exports；
Secondary FM modulates formula used are as follows:
S (t)=i (t)+q (t)
Ffm=ks (t)
In formula, s (t) is I after subcarrier modulation, and the sum of the road Q signal, k is scale factor, FfmFor the frequency control word of DDS.
The demodulation method, comprising the following steps:
Step A, bandpass sampling is carried out to the intermediate-freuqncy signal received；
Step B, Digital Down Convert processing is carried out to the data after sampling, signal frequency is changed near zero-frequency, then under
Signal after side frequency carries out 200 point CIC filtering extractions, obtains I, Q two paths of signals；
Step C, the signal after extracting to CIC carries out FM demodulation, and FM demodulation carries out difference frequency discrimination using small angle approximation method,
To obtain the frequency information of signal, DPSK modulated signal is exported；FM demodulates formula used are as follows:
X (n)=Δ θ (n)=sin Δ θ (n)=Q (n) I (n-1)-I (n) Q (n-1)
Wherein, X (n) is the output of difference frequency discrimination, and Δ θ (n) is phase difference, and (I (n-1), Q (n-1)) is one on planisphere
Point, (I (n), Q (n)) are another points on planisphere, and the two o'clock time difference is the length of a sampling clock.
Step D, DPSK demodulation is carried out to obtained DPSK modulated signal, DPSK demodulation uses differential ference spiral, first solves to FM
It adjusts signal to carry out the processing of one symbol lengths of delay, then non-time delayed signal is multiplied with time delayed signal and carries out the phase of front and back symbol
Position comparison, to demodulate DPSK modulated subcarrier signal；
Step E, bit timing processing is carried out to DPSK demodulated signal, point eight tunnels first is carried out to DPSK demodulated signal and are added up,
In the different location in a symbol, accumulation length is the length of a symbol for cumulative starting point；And after adding up
Value is saved, and the frame head EB90 of accumulated value and information frame that eight tunnel Zai Dui saves carries out matching treatment, finds matching value maximum
All the way；Finally this road signal is exported, obtains safety control information.
The present invention adds up since the different initial positions of a symbol, is saved after adding up after the symbol lengths that add up
Value, then matching treatment is done with safety control information frame frame head EB90 to the value of preservation, the maximum signal all the way of matching value is found out as most
Whole decision signal can substantially reduce the bit error rate in this way, improve system performance.
It is described in detail below with reference to embodiment.
Embodiment
The present embodiment safety control information rate is 2.4kbps, subcarrier frequency 12KHz, demodulates intermediate frequency 12MHz, sampling frequency
Rate 57.6MHz, it is 1MHz that receiver, which receives signal bandwidth,.
For modulation module, first to safety control information after pulse code modulation, then DPSK subcarrier modulation is carried out to it,
The signal of output is dpsk signal, finally carries out secondary FM modulation again using DPSK modulated signal.
Peace control pcm stream first carries out differential encoding as shown in Figure 1:, carries out PSK tune to the sine and cosine signal that DDS is generated
It is made:
I (t)=a (t) cos (2 π f1t+θ) (1)
Q (t)=a (t) sin (2 π f1t+θ) (2)
S (t)=i (t)+q (t) (3)
Wherein f1For subcarrier frequency, θ is phase of the modulated signal with respect to width carrier frequency.
Further, s (t) result is inputted into FM modulator.FM realization principle are as follows: by input signal directly as modulator
DDS frequency control word, i.e. the frequency of FM signal are as follows:
Ffm=s (t) (4)
But specific modulation bandwidth in order to obtain, it needs before s (t) multiplied by a coefficient, it may be assumed that
Ffm=ks (t) (5)
In above formula, the master clock of modulator is 100MHz, and the bit wide of s (t) is 16bit, it is assumed that the bit wide of the NCO of DDS is
32bit, thus multiplied by coefficient k can be the numbers of 16 bits, in this way when k=1, obtained minimum frequency is inclined
It moves:
min(Ffm)=216/232×100×106=1.53k (6)
It can satisfy requirement.
It is postulated that in order to obtaining maximum frequency deviation Fmax, seek scale factor k:
k×216/232×100×106=Fmax (7)
K=6.5536 × 10-4×Fmax (8)
The parameter can be obtained by host computer operation.
For demodulation module, first to signal progress Digital Down Convert is received, signal frequency is changed near zero-frequency, to following
Signal after frequency carries out CIC extraction.Signal enters FM demodulating unit after extraction, and the output of FM demodulating unit is DPSK modulation letter
Number, the demodulation of DPSK is finally carried out, safety control information is therefrom extracted.
As shown in Figure 2: CIC is extracted using 200 points of extractions, and since sampling rate is 57.6MHz, data rate is after extraction
288kHz, character rate 2.4Kbps, so a symbol has 120 data points.FM and DPSK is carried out to the signal after extraction
Demodulation.
Further, the data after extracting to CIC carry out FM demodulation.
It is as shown in Figure 3: the method that the demodulation of FM uses difference frequency discrimination.Here frequency discrimination algorithm does not use traditional arc tangent
Operation frequency discrimination, but use a kind of method for avoiding arctangent cp cp operation.
A kind of small angle approximation method is proposed thus, and since system is a kind of PSK modulating system, and PSK modulation is a kind of
The modulation of permanent envelope, that is, all points from planisphere are all on unit circle, it is possible to it obtains:
Wherein θ1It is point on planisphere (I (n-1), Q (n-1)) phase, θ2It is the phase of point on planisphere (I (n), Q (n)).
Then have:
After carrier frequency acquisition, the general very little of frequency difference knows sin by small angle approximation rule when Δ θ (n) very little
Δ θ (n) and Δ θ (n) are approximately equal, it is possible to obtain:
X (n)=Δ θ (n)=sin Δ θ (n)=Q (n) I (n-1)-I (n) Q (n-1) (11)
This algorithm is to seek phase not over arc tangent is calculated, but seeks phase by seeking its sine function.
Certain condition is that this difference phase cannot be too big.Due to there was only subtraction of 2 multiplication, calculation amount is greatly reduced, and hardware is real
It is now also simple and convenient.Therefore higher Sampling Rate can also be used, but being limited in for it can be only applied to modulation angle
In the case where very little.
Fig. 4 is that FM demodulation is realized inside FPGA, the actual waveform caught by Chipscope debugging tool, Cong Tuzhong
It is seen to be a DPSK modulated signal.Using the XC7A100T of XILINX company, Chipscope version is FPGA
ChipScope Pro Analyzer Version:14.7P.20131013。
Further, DPSK demodulation is carried out to the data after FM demodulation.
As shown in Figure 5: FM demodulated output signal is the DPSK modulated subcarrier signal of frequency stabilization, this signal enters difference
Demodulation module is divided to be demodulated.The principle of differential ference spiral is the phase difference of direct relatively front and back symbol, to restore send two
Binary information.Due to completing the effect of yard inverse transformation while demodulation, therefore a yard inverse transformer is not needed in demodulator, that is, be not required to
Want special coherent carrier.
Further, bit timing realization is carried out to the data after DPSK demodulation.
As shown in fig. 6, since signal is burst mode, so to go detection to believe by sending the synchronous head of signal frame
Number, while being gone to do relevant matches with DPSK demodulated signal with synchronous head, find optimal judgement position.By in different startings
Position starts to add up, and cumulative length is exactly a symbol lengths.Finally accumulated value is deposited in each cumulative finish time.This
A little values are exactly the specifying information solved.Only if not optimal cumulative position, accumulated value may will affect judgement, thus
Cause the appearance of error code.And the cumulative value of information solved of different location is matched here with synchronous head, matching value is maximum
The value of information solved all the way be most reliable.Result is considered the information code current solved after its cumulative deposit, finally to output
As a result it adjudicates, is information code 1 greater than 0, minus is information code 0.Information can thus be demodulated and.
Fig. 7 is that DPSK demodulation is realized inside FPGA, the actual waveform caught by Chipscope debugging tool, from figure
In find out after DPSK demodulation symbol is cumulative, safety control information frame has correctly been demodulated, can significantly be seen in figure
Value after adding up out is divided to two kinds of positive and negative values distributions, is information code 1 in 0, and minus is information code 0.Only add up starting
Point is different, and final accumulation result value is of different sizes, in order to improve the reliability of symbol judgement, so do bit timing when
It waits, to divide eight different initial positions to add up respectively, to find out optimal judgement position.FPGA is using XILINX
The XC7A100T of company, Chipscope version are ChipScope Pro Analyzer Version:14.7P.20131013.
Embodiment described above, the description thereof is more specific and detailed, but can not be interpreted as the limit to this patent range
System.It should be pointed out that for those of ordinary skill in the art, under the premise of not departing from this programme design, may be used also
To make several modifications and improvements, these are all belonged to the protection scope of this patent.
Claims (5)
1. a kind of PCM/DPSK/FM modulation /demodulation module, which is characterized in that including modulation module and demodulation module two parts, institute
Stating modulation module includes sequentially connected pulse code modulation module, differential encoding module, BPSK subcarrier modulation module and two
Secondary FM modulation module, wherein pulse code modulation module is used to carry out the safety control information received pulse code, and will coding
Signal afterwards sends BPSK subcarrier modulation module to by differential encoding module, after differential encoding module is used for pulse code
Signal carry out differential encoding, BPSK subcarrier modulation module be used for after differential encoding signal carry out BPSK subcarrier tune
System, and give the modulated signal of output to secondary FM modulation module, secondary FM modulation module, which is used to modulate BPSK subcarrier, to be believed
Number carry out FM secondary modulation；Demodulation module includes down conversion module, CIC abstraction module, FM demodulation module, DPSK solution mode transfer
Block, bit timing module；Wherein down conversion module is for leading to reception signal frequency converting to zero-frequency, and by the signal after down coversion
It crosses CIC abstraction module and gives FM demodulation module, CIC abstraction module carries out 200 points of extraction to the signal after down coversion；FM demodulation
The demodulation that module is used to carry out the signal after extraction FM obtains DPSK modulated subcarrier signal, and gives output signal to DPSK
Demodulation module；DPSK demodulation module is used to carry out differential ference spiral to input signal, and gives output signal to bit timing module；Position
Timing module obtains optimal determination point, to demodulate peace control letter for doing bit timing processing to the signal after differential ference spiral
Breath；
Above system modulator approach the following steps are included:
Step 1 carries out pulse code modulation to safety control information；
Step 2 carries out the modulation of DPSK subcarrier to the signal after pulse code modulation, specifically: first pulse code modulation is believed
Number differential encoding is carried out, then bpsk signal modulation is carried out to the signal after differential encoding, modulation carrier wave is that the secondary of low frequency carries
Wave signal；
Step 3 carries out secondary FM modulation to signal after the modulation of DPSK subcarrier, first carries out I, Q to DPSK modulated subcarrier signal
The signal of two branches is added, then the signal of addition is multiplied a scale factor, finally goes control one with the signal for multiplying scale factor
The frequency control word of a DDS module obtains secondary FM modulated signal, will obtain final modulated signal and exports；
Above system demodulation method the following steps are included:
Step A, bandpass sampling is carried out to the intermediate-freuqncy signal received；
Step B, Digital Down Convert processing is carried out to the data after sampling, signal frequency is changed near zero-frequency, then to lower side frequency
Signal afterwards carries out 200 point CIC filtering extractions, obtains I, Q two paths of signals；
Step C, the signal after extracting to CIC carries out FM demodulation, and FM demodulation carries out difference frequency discrimination using small angle approximation method, thus
The frequency information of signal is obtained, DPSK modulated signal is exported；
Step D, DPSK demodulation is carried out to obtained DPSK modulated signal, DPSK demodulation uses differential ference spiral, first demodulates and believe to FM
Number carry out the processing of one symbol lengths of delay, then non-time delayed signal is multiplied with time delayed signal carry out before and after symbol phase pair
Than to demodulate DPSK modulated subcarrier signal；
Step E, bit timing processing is carried out to DPSK demodulated signal, point eight tunnels first is carried out to DPSK demodulated signal and are added up, added up
In the different location in a symbol, accumulation length is the length of a symbol for starting point；And will it is cumulative after value into
Row saves, and the frame head EB90 of accumulated value and information frame that eight tunnel Zai Dui saves carries out matching treatment, finds matching value maximum one
Road；Finally this road signal is exported, obtains safety control information.
2. a kind of PCM/DPSK/FM modulation-demo-demodulation method based on PCM/DPSK/FM modulation /demodulation module described in claim 1,
It is characterized in that, the modulator approach the following steps are included:
Step 1 carries out pulse code modulation to safety control information；
Step 2 carries out the modulation of DPSK subcarrier to the signal after pulse code modulation, specifically: first pulse code modulation is believed
Number differential encoding is carried out, then bpsk signal modulation is carried out to the signal after differential encoding, modulation carrier wave is that the secondary of low frequency carries
Wave signal；
Step 3 carries out secondary FM modulation to signal after the modulation of DPSK subcarrier, first carries out I, Q to DPSK modulated subcarrier signal
The signal of two branches is added, then the signal of addition is multiplied a scale factor k, finally goes control one with the signal for multiplying scale factor
The frequency control word of a DDS module obtains secondary FM modulated signal, will obtain final modulated signal and exports；
The demodulation method, comprising the following steps:
Step A, bandpass sampling is carried out to the intermediate-freuqncy signal received；
Step B, Digital Down Convert processing is carried out to the data after sampling, signal frequency is changed near zero-frequency, then to lower side frequency
Signal afterwards carries out 200 point CIC filtering extractions, obtains I, Q two paths of signals；
Step C, the signal after extracting to CIC carries out FM demodulation, and FM demodulation carries out difference frequency discrimination using small angle approximation method, thus
The frequency information of signal is obtained, DPSK modulated signal is exported；
Step D, DPSK demodulation is carried out to obtained DPSK modulated signal, DPSK demodulation uses differential ference spiral, first demodulates and believe to FM
Number carry out the processing of one symbol lengths of delay, then non-time delayed signal is multiplied with time delayed signal carry out before and after symbol phase pair
Than to demodulate DPSK modulated subcarrier signal；
Step E, bit timing processing is carried out to DPSK demodulated signal, point eight tunnels first is carried out to DPSK demodulated signal and are added up, added up
In the different location in a symbol, accumulation length is the length of a symbol for starting point；And will it is cumulative after value into
Row saves, and the frame head EB90 of accumulated value and information frame that eight tunnel Zai Dui saves carries out matching treatment, finds matching value maximum one
Road；Finally this road signal is exported, obtains safety control information.
3. PCM/DPSK/FM modulation-demo-demodulation method according to claim 2, which is characterized in that DPSK subcarrier in step 2
Modulate formula used are as follows:
I (t)=a (t) cos (2 π f1t+θ)
Q (t)=a (t) sin (2 π f1t+θ)
In formula, i (t) is that DPSK modulates the road I signal, and q (t) is that DPSK modulates the road Q signal, and a (t) is to have carried out the peace of differential encoding
Control information, f1For subcarrier frequency, θ is subcarrier initial phase.
4. PCM/DPSK/FM modulation-demo-demodulation method according to claim 2, which is characterized in that secondary FM modulation in step 3
Formula used are as follows:
S (t)=i (t)+q (t)
Ffm=ks (t)
In formula, s (t) is I after subcarrier modulation, and the sum of the road Q signal, k is scale factor, FfmFor the frequency control word of DDS.
5. PCM/DPSK/FM modulation-demo-demodulation method according to claim 2, which is characterized in that in step C used in FM demodulation
Formula are as follows:
X (n)=Δ θ (n)=sin Δ θ (n)=Q (n) I (n-1)-I (n) Q (n-1)
Wherein, X (n) is the output of difference frequency discrimination, and Δ θ (n) is phase difference, and (I (n-1), Q (n-1)) is a point, (I on planisphere
(n), Q (n)) it is another point on planisphere, the two o'clock time difference is the length of a sampling clock.
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| CN108429711B (en) * | 2018-01-29 | 2020-09-04 | 北京航空航天大学 | Safety control method for target range |
| CN112019272B (en) * | 2020-08-04 | 2021-07-06 | 大连理工大学 | Digital-analog signal hybrid transmission system based on OOK and FM |
| CN112073151B (en) * | 2020-09-07 | 2023-02-17 | 中电科思仪科技股份有限公司 | Telemetry PCM decoding and frame synchronization method based on FPGA |
| CN112737710B (en) * | 2020-12-24 | 2023-02-17 | 重庆航天火箭电子技术有限公司 | PCM-DPSK-FM safety control receiver index testing method |
| CN112737619B (en) * | 2020-12-24 | 2022-05-13 | 重庆航天火箭电子技术有限公司 | Design method of full open loop PCM-DPSK-FM safety control receiver |
| CN117768034B (en) * | 2023-12-08 | 2024-07-09 | 重庆邮电大学 | Coding method of space optical communication high-order DPSK simplified system |
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| JPH01185802A (en) * | 1988-01-21 | 1989-07-25 | Sanyo Electric Co Ltd | Recording and reproducing system for satellite broadcasting |
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| CN105847205A (en) * | 2016-03-21 | 2016-08-10 | 常州大学 | Square wave differential phase shift keying modulation-demodulation method based on gradient |
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