CN108712358A - A kind of general QAM and APSK demodulators and demodulation method - Google Patents
A kind of general QAM and APSK demodulators and demodulation method Download PDFInfo
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- CN108712358A CN108712358A CN201810324489.6A CN201810324489A CN108712358A CN 108712358 A CN108712358 A CN 108712358A CN 201810324489 A CN201810324489 A CN 201810324489A CN 108712358 A CN108712358 A CN 108712358A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
- H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
- H04L27/38—Demodulator circuits; Receiver circuits
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
- H04L27/22—Demodulator circuits; Receiver circuits
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Abstract
The present invention provides a kind of general QAM and APSK demodulators, including intermediate-frequency filter, AD samplers, frequency mixer, low-pass filter, matched filter, balanced device, bit synchronizer, phase discriminator, carrier wave NCO and loop filter, wherein intermediate-frequency filter receives QAM/APSK signals, and decision feedback equalizer exports modulated signal to ppu.The demodulator of the present invention is according to QAM, APSK system signal constellation (in digital modulation) figure characteristic, innovative devises the closed loop of low-pass filter-matched filter-bit synchronizer and the closed loop of low-pass filter-matched filter-balanced device-phase discriminator-loop filter-carrier wave NCO, it is more that above-mentioned two closed loop solves QAM, APSK constellation figure constellation point well, the insurmountable demodulation problem of legacy demodulator.
Description
Technical field
The invention belongs to mobile communication, satellite communication and wireless relay fields, and in particular to a kind of general QAM, APSK solution
Adjust device.
Background technology
Digital communication system can more reliably transmit the information of higher rate compared to analog communication system.By channel coding
Coded modulation (Coded Modulation, CM) technology that technology is combined into digital modulation technique is digital communication system
One of core technology is the important means of the transmission reliability and efficiency of transmission that improve digital information.In order to adapt to digital information
Transmission demand under common channel, realize high efficient and reliable information transmission, design high performance coding modulation technique to close weight
It wants.
For typical digital communication system, constellation mapping is one of key technology of digital modulation.Constellation mapping refers to
The bit sequence for carrying information is become to the symbol for being suitable for transmission according to the mapping of specific constellation mapping scheme.Symbol takes
Value space can be the real number space of one-dimensional real number space, two-dimentional real number space or more higher-dimension.Constellation mapping include planisphere and
Two fundamentals of constellation mapping mode.Planisphere is the collection for the be possible to value (i.e. constellation point) that constellation mapping generates symbol
It closes, constellation mapping mode is mapping relations of the input bit sequence to constellation point.
According to information theory knowledge, believe at additive white Gaussian noise (Additive White Gaussian Noise, AWGN)
Under road, when transmission power is by limited time, only when channel inputs distribution Gaussian distributed, system can be only achieved channel capacity.
However, in actual digital communication system, input signal is constrained by planisphere set, disobeys Gaussian Profile, practical
There are gap between the rate of information throughput and channel capacity of system, this gap is also referred to as Shaping losses.Construction one
The important criteria of solid constellation mapping, key are so that in given spectrum efficiency or the condition of signal-to-noise ratio target
Under, the gap between the rate of information throughput upper limit and channel capacity limit of the code modulation system under constellation mapping limitation is as possible
It is small.
When input signal is limited by planisphere set χ, the Average Mutual of channel input signal X and channel output Y,
Referred to as Average Mutual (average mutual information of coded-modulation, CM- of coded modulation
), AMI it is the attainable transmission rate upper limit of actual coding modulating system institute.
In practical applications, using the reception scheme of independent demapping, independent demapping can cause to compile many systems
Code modulating system loss of energy, at this time the Average Mutual between channel input signal and output signal be known as BICM-AMI,
It is the attainable transmission rate upper limit of coded modulation scheme using independent demapping.
High-order constellation map is to improve one of the important means of the spectrum efficiency of digital communication system.The planisphere of early stage is set
In meter, it is generally recognized that the minimum euclidean distance between constellation point is bigger, and planisphere performance is better, practical to be according to this criterion
Common high-order constellation map of uniting is uniform quadrature amplitude modulation (the Quadrature Amplitude for having gray mappings
Modulation, QAM) planisphere, abbreviation Gray-QAM.However, the information transmission uniformly under Gray-QAM constellation constraint diagrams is fast
There are larger gaps between rate and channel capacity limit, up to 1.53dB under spectral efficient.It is uniform compared to traditional
Gray-QAM planispheres so that the technology that the output under constellation limitation more approaches Gaussian Profile is known as Shaping technologies, thus band
The gain come is known as Shaping gains.One important and common Shaping technology is non-homogeneous Shaping technologies, passes through order
Heterogeneous characteristics are presented in planisphere so that channel input signal after constellation mapping is closer to Gaussian Profile.
Using non-uniform constellation figure Shaping technologies, Liu and Xie etc. are based on maximum mutual information criterion, it is proposed that a kind of tool
There is the planisphere of the uniform amplitude phase-shift keying (PSK) (Amplitude-Phase Shift Keying, APSK) of gray mappings, referred to as
Gray-APSK.In Gray-APSK, the APSK constellation figure of a M rank is made of R concentric ring, the number of constellation points phase on each ring
Deng and be 2 integral number power, the constellation point on each ring is uniformly distributed in phase.When constellation mapping, a length of log2The bit of M
Vector is mapped to a constellation point, and the partial bit in bit vectors is only related with phase, the phase of a corresponding gray mappings
Move keying (Phase Shift Keying, PSK), remaining bit is only related with amplitude, a corresponding gray mappings it is non-homogeneous
Pulse amplitude modulation (Pulse Amplitude Modulation, PAM).Compared to traditional Gray-QAM, Gray-APSK exists
Under awgn channel and fading channel, higher CM-AMI and BICM-AMI is suffered from common code check, i.e., is either being used
All there is better performance in the code modulation system of independent demapping or iterative demapping.
Due to the donut structure of APSK, performance is influenced by the constellation point distribution on each ring with each ring radius.
In Gray-APSK, the constellation point on each ring is uniformly distributed in phase, is equivalent to a uniform Gray-PSK.But it is worth
It is noted that for PSK constellation mappings, using non-homogeneous Shaping technologies, that is, it is non-equal so that the point on ring is presented in phase
The feature of even distribution, obtained PSK constellation mappings heterogeneous can have higher BICM-AMI.For common target signal to noise ratio
Value, the PSK constellation mappings based on maximum mutual information criterion design, heterogeneous characteristics are presented in constellation point in phase, this non-equal
Even feature is particularly evident in low signal-to-noise ratio.
QAM and APSK is current most commonly used high order modulation system, and traditional demodulator or is only applicable in QAM mono-
Kind system or a kind of system for being only applicable in APSK, it is difficult to all systems of compatible QAM and APSK.
Invention content
Present invention solves the technical problem that being：Overcome in the prior art QAM, APSK system planisphere constellation point it is more, lead to
With the defects such as property is low, a kind of general QAM, APSK demodulator is provided.
The present invention uses following technical scheme：A kind of general QAM and APSK demodulators, including intermediate-frequency filter, AD sampling
Device, frequency mixer, low-pass filter, matched filter, balanced device, bit synchronizer, phase discriminator, carrier wave NCO and loop filter；
QAM the or APSK signals that the intermediate-frequency filter receives input filter out signal noise after intermediate frequency filtering is handled
It, and will treated that signal exports gives AD samplers with out-of-band interference；
After the AD samplers receive QAM the or APSK signals of intermediate-frequency filter output, digital sample is carried out, simulation is believed
Number digital signal is converted to, and digital signal is exported to frequency mixer；
The frequency mixer receives the digital signal of AD samplers output and the same phase of carrier wave NCO outputs and orthogonal two-way is local
Carrier signal, and to digital signal respectively with same phase and orthogonal two signal multiplications, and complete be multiplied after signal down coversion at
Reason, by treated, I, Q two ways of digital signals are exported to low-pass filter；
The low-pass filter receives I, Q two ways of digital signals of frequency mixer output, carries out low-pass filtering treatment, filters out white
Two harmonics that noise and mixing generate, and I, Q two ways of digital signals are exported to bit synchronizer by treated；
The bit synchronizer receives I, Q two ways of digital signals of low-pass filter output, carries out the recovery of chip clock, and
I, Q two ways of digital signals after recovery is exported to matched filter；
The matched filter receives I, Q two ways of digital signals after the recovery of bit synchronizer output, carries out matched filtering
Processing, and I, Q two ways of digital signals are exported respectively to balanced device and phase discriminator by treated；Matched filter can be according to defeated
The bandwidth for entering signal adjusts the coefficient of matched filter；
The digital signal of equalizer input matched filter output, carries out equilibrium treatment, and will treated signal
It is exported respectively to phase discriminator and ppu；
The phase discriminator receives the digital signal of matched filter and balanced device output respectively, and carries out at phase demodulation respectively
Reason, and treated that digital signal is exported to loop filter by phase demodulation；
The loop filter receives the digital signal of phase discriminator output, carries out loop filtering processing, and by treated
Digital signal, which exports, gives carrier wave NCO；
The carrier wave NCO receives the digital signal of loop filter output, generates local carrier, and local carrier is exported
To frequency mixer.
A method of it is demodulated using above-mentioned general QAM and APSK demodulators, steps are as follows：
1) QAM or APSK signals are received, digital sample is carried out, convert analog signals into digital signal, and number is believed
Number output to frequency mixer；
2) frequency mixer receives the same phase of digital signal and carrier wave NCO outputs and orthogonal two-way local carrier signal, and logarithm
Word signal with same phase and orthogonal two signal multiplications, and completes the down-converted of signal after being multiplied respectively, will treated I, Q
Two ways of digital signals is exported to bit synchronizer；
3) bit synchronizer receives treated I, Q two ways of digital signals, carries out the recovery of chip clock, and will be after recovery
I, Q two ways of digital signals is exported to matched filter；
4) matched filter receives I, Q two ways of digital signals after the recovery of bit synchronizer output, carries out at matched filtering
Reason, and I, Q two ways of digital signals are exported respectively to balanced device and phase discriminator by treated；
5) digital signal of equalizer input matched filter output carries out equilibrium treatment, and signal divides by treated
It does not export to phase discriminator and ppu；
6) phase discriminator receives the digital signal of matched filter and balanced device output respectively, and carries out phase demodulation processing respectively,
And treated that digital signal exports gives carrier wave NCO by phase demodulation；
7) carrier wave NCO receives the digital signal of phase discriminator output, generates local carrier, and local carrier is exported to mixing
Device.
Treated that digital signal exports to before carrier wave NCO by phase demodulation for the step 6), and by phase demodulation, treated that number is believed
Number carry out loop filtering processing.
After I, Q two ways of digital signals of step 2) frequency mixer output, carry out low-pass filtering treatment, filter out white noise and
Two harmonics generated are mixed, and I, Q two ways of digital signals are exported to bit synchronizer by treated.
A kind of computer readable storage medium, the computer-readable recording medium storage have computer program, the meter
Calculation machine program is performed the step of realizing the above method.
Compared with prior art the beneficial effects of the invention are as follows：
1, for demodulator of the invention according to QAM, APSK system signal constellation (in digital modulation) figure characteristic, innovative devises low-pass filtering
The closed loop and low-pass filter-matched filter-balanced device-phase discriminator of device-matched filter-bit synchronizer-loop filter
The closed loop of wave device-carrier wave NCO, it is more that above-mentioned two closed loop solves QAM, APSK constellation figure constellation point well,
The insurmountable demodulation problem of legacy demodulator；
2, the present invention is designed, enhancing is in high speed to adapt to high-speed transfer requirement using the matched filter of customized parameter
Demodulation performance when transmission, while extending the bit rate range that can be demodulated；
3, the technology of the present invention side has cross-species transferability, can be compatible with two kinds of system signals of QAM, APSK, only does a little more
Change the demodulation of the systems such as the demodulation that can be completed to other modulation system signals, such as PSK, GMSK.
Description of the drawings
Fig. 1 is the system diagram of general QAM, APSK modulator.
Specific embodiment
To keep the purpose of the present invention, content and advantage clearer, below in conjunction with attached drawing 1 to embodiment of the present invention
It is described in further detail.
A kind of general QAM and APSK demodulators, it is characterised in that：Including intermediate-frequency filter, AD samplers, frequency mixer, low
Bandpass filter, matched filter, balanced device, bit synchronizer, phase discriminator, carrier wave NCO and loop filter；Intermediate-frequency filter receives
APSK signals, balanced device export modulated signal to ppu.The intermediate-frequency filter receives QAM or the APSK letter of input
Number, after intermediate frequency filtering is handled, filter out signal noise and out-of-band interference, and will treated that signal exports gives AD samplers；
After the AD samplers receive QAM the or APSK signals of intermediate-frequency filter output, digital sample is carried out, is converted analog signals into
Digital signal, and digital signal is exported to frequency mixer；The frequency mixer receives the digital signal and carrier wave of AD samplers output
NCO output same phase and orthogonal two-way local carrier signal, and to digital signal respectively with same phase and orthogonal two signal multiplications,
And the down-converted of signal after being multiplied is completed, by treated, I, Q two ways of digital signals are exported to low-pass filter；It is described low
Bandpass filter receives I, Q two ways of digital signals of frequency mixer output, carries out low-pass filtering treatment, filters out white noise and mixing generates
Two harmonics, and will treated that I, Q two ways of digital signals are exported to bit synchronizer；The bit synchronizer receives low pass filtered
I, Q two ways of digital signals of wave device output carry out the recovery of chip clock, and I, Q two ways of digital signals after recovery are exported
To matched filter；The matched filter receives I, Q two ways of digital signals after the recovery of bit synchronizer output, is matched
It is filtered, and I, Q two ways of digital signals are exported respectively to balanced device and phase discriminator by treated；Matched filter being capable of root
According to the bandwidth of input signal, the coefficient of matched filter is adjusted；The digital signal of the equalizer input matched filter output,
Equilibrium treatment is carried out, and signal is exported respectively to phase discriminator and ppu by treated；The phase discriminator receives respectively
The digital signal of matched filter and balanced device output, and carry out phase demodulation processing respectively, and by phase demodulation treated digital signal
It exports to loop filter；The loop filter receives the digital signal of phase discriminator output, carries out loop filtering processing, and will
Digital signal that treated, which exports, gives carrier wave NCO；The carrier wave NCO receives the digital signal of loop filter output, generates this
Ground carrier wave, and local carrier is exported to frequency mixer, the signal of output is further processed in the ppu.
Application example
General QAM, APSK demodulator of the present invention is applied in satellite communication receiver, QAM, APSK signal are completed
Demodulation, and demodulation performance is investigated, test connection figure is as shown in Fig. 2, result such as following table：
Specific examples are used herein to describe the principles and implementation manners of the present invention, the explanation of above example
It is merely used to help understand the core idea of the present invention；Meanwhile for those of ordinary skill in the art, think of according to the present invention
Think, there will be changes in the specific implementation manner and application range, in conclusion the content of the present specification should not be construed as pair
The limitation of the present invention.
Claims (10)
1. a kind of general QAM and APSK demodulators, it is characterised in that：Including AD samplers, frequency mixer, matched filter, equilibrium
Device, bit synchronizer, phase discriminator and carrier wave NCO；
After the AD samplers receive QAM or APSK signals, digital sample is carried out, digital signal is converted analog signals into, and
Digital signal is exported to frequency mixer；
The frequency mixer receives the digital signal of AD samplers output and same phase and the orthogonal two-way local carrier of carrier wave NCO outputs
Signal, and to digital signal respectively with same phase and orthogonal two signal multiplications, and complete be multiplied after signal down-converted, will
Treated, and I, Q two ways of digital signals are exported to bit synchronizer；
I, Q two ways of digital signals that the bit synchronizer receives that treated, carry out the recovery of chip clock, and by after recovery I,
Q two ways of digital signals is exported to matched filter；
The matched filter receives I, Q two ways of digital signals after the recovery of bit synchronizer output, carries out matched filtering processing,
And I, Q two ways of digital signals are exported respectively to balanced device and phase discriminator by treated；
The digital signal of the equalizer input matched filter output carries out equilibrium treatment, and signal is distinguished by treated
It exports to phase discriminator and ppu；
The phase discriminator receives the digital signal of matched filter and balanced device output respectively, and carries out phase demodulation processing respectively, and
By phase demodulation, treated that digital signal exports gives carrier wave NCO；
The carrier wave NCO receives the digital signal of phase discriminator output, generates local carrier, and local carrier is exported to mixing
Device.
2. a kind of general QAM and APSK demodulators according to claim 1, it is characterised in that：The matched filter energy
Enough bandwidth according to input signal adjust the coefficient of matched filter.
3. a kind of general QAM and APSK demodulators according to claim 1 or 2, it is characterised in that：Further include being located at phase demodulation
Loop filter between device and carrier wave NCO；The loop filter receives the digital signal of phase discriminator output, carries out loop filter
Wave processing, and will treated that digital signal exports gives carrier wave NCO.
4. a kind of general QAM and APSK demodulators according to claim 1 or 2, it is characterised in that：Further include being placed on AD
The intermediate-frequency filter for filtering out noise before sampler；The intermediate-frequency filter receives QAM the or APSK signals of input, warp
After crossing intermediate frequency filtering processing, signal noise and out-of-band interference are filtered out, and will treated that signal exports gives AD samplers.
5. a kind of general QAM and APSK demodulators according to claim 1 or 2, it is characterised in that：Further include being located at phase demodulation
Loop filter between device and carrier wave NCO；The loop filter receives the digital signal of phase discriminator output, carries out loop filter
Wave processing, and will treated that digital signal exports gives carrier wave NCO.
6. a kind of general QAM and APSK demodulators according to claim 1 or 2, it is characterised in that：Further include be placed on it is mixed
Low-pass filter between frequency device and bit synchronizer；The low-pass filter receives I, Q two ways of digital signals of frequency mixer output,
Low-pass filtering treatment is carried out, filters out white noise and two harmonics that mixing generates, and will treated I, Q two ways of digital signals
It exports to bit synchronizer.
7. a kind of method demodulated using above-mentioned general QAM and APSK demodulators, it is characterised in that steps are as follows：
1) QAM or APSK signals are received, digital sample is carried out, converts analog signals into digital signal, and digital signal is defeated
Go out to frequency mixer；
2) frequency mixer receives the same phase of digital signal and carrier wave NCO outputs and orthogonal two-way local carrier signal, and believes number
Number respectively with same phase and orthogonal two signal multiplications, and the down-converted of signal after being multiplied is completed, it will treated I, Q two-way
Digital signal is exported to bit synchronizer；
3) bit synchronizer receives treated I, Q two ways of digital signals, carries out the recovery of chip clock, and by I, Q after recovery
Two ways of digital signals is exported to matched filter；
4) matched filter receives I, Q two ways of digital signals after the recovery of bit synchronizer output, carries out matched filtering processing, and
By treated, I, Q two ways of digital signals are exported respectively to balanced device and phase discriminator；
5) digital signal of equalizer input matched filter output carries out equilibrium treatment, and signal difference is defeated by treated
Go out to phase discriminator and ppu；
6) phase discriminator receives the digital signal of matched filter and balanced device output respectively, and carries out phase demodulation processing respectively, and will
Treated that digital signal exports gives carrier wave NCO for phase demodulation；
7) carrier wave NCO receives the digital signal of phase discriminator output, generates local carrier, and local carrier is exported to frequency mixer.
8. a kind of general QAM and APSK demodulation methods according to claim 7, it is characterised in that：The step 6) will reflect
Digital signal after phase processor is exported to before carrier wave NCO, and by phase demodulation, treated that digital signal carries out loop filtering processing.
9. a kind of general QAM and APSK demodulation methods according to claim 7, it is characterised in that：Step 2) the mixing
After I, Q two ways of digital signals of device output, low-pass filtering treatment is carried out, filters out two harmonics of white noise and mixing generation,
And I, Q two ways of digital signals are exported to bit synchronizer by treated.
10. a kind of computer readable storage medium, the computer-readable recording medium storage has computer program, feature to exist
In：The computer program is performed realization such as claim 7 or 8 or the step of 9 the method.
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| CN110071891A (en) * | 2019-04-28 | 2019-07-30 | 中国传媒大学 | Phase demodulating method, apparatus and system based on CE-OFDM technology |
| CN113726716A (en) * | 2021-08-25 | 2021-11-30 | 北京理工大学 | Carrier phase error identification method based on decision feedback |
| RU2786159C1 (en) * | 2022-07-18 | 2022-12-19 | Федеральное государственное бюджетное образовательное учреждение высшего образования "Майкопский государственный технологический университет" | Digital signal demodulator with amplitude-phase keying |
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| CN113726716A (en) * | 2021-08-25 | 2021-11-30 | 北京理工大学 | Carrier phase error identification method based on decision feedback |
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Application publication date: 20181026 |