CN105471794A - Digital pulse shaping intermediate-frequency modulation method - Google Patents

Digital pulse shaping intermediate-frequency modulation method Download PDF

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Publication number
CN105471794A
CN105471794A CN201510786356.7A CN201510786356A CN105471794A CN 105471794 A CN105471794 A CN 105471794A CN 201510786356 A CN201510786356 A CN 201510786356A CN 105471794 A CN105471794 A CN 105471794A
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China
Prior art keywords
signal
digital
frequency modulation
filter
sampling
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CN201510786356.7A
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Chinese (zh)
Inventor
蒋友邦
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CETC 10 Research Institute
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CETC 10 Research Institute
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Priority to CN201510786356.7A priority Critical patent/CN105471794A/en
Publication of CN105471794A publication Critical patent/CN105471794A/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2626—Arrangements specific to the transmitter only
    • H04L27/2627—Modulators
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2626—Arrangements specific to the transmitter only
    • H04L27/2627—Modulators
    • H04L27/264—Pulse-shaped multi-carrier, i.e. not using rectangular window

Abstract

The invention puts forward a digital pulse shaping intermediate-frequency modulation method, and aims to provide a digital pulse shaping intermediate-frequency modulation method which has the characteristics of fixed filter coefficient, simple implementation, reliability and low resource consumption and can be applied to arbitrarily configurable symbol rate. The method is implemented through the following technical scheme: a baseband digital signal is constellation-mapped into I and Q branch signals; L-time up-sampling of the I and Q branch signals is carried out through an up-sampler, and an obtained over-sampling signal of which the rate is Rs is filtered by a shaping filter, thus completing baseband spectrum shaping of the I and Q branches; then, an interpolation filter is introduced into a direct digital synthesizer (DDS), and the I and Q branches are interpolated at DA sampling rate in the interpolation filter to complete sampling rate conversion; after digital intermediate-frequency modulation of the combined I and Q signal, the signal is sent to a digital-to-analog converter DA and reconstructed into an analog signal; and the out-band spectrum of the analog signal is filtered by an analog band-pass filter, and a shaped intermediate-frequency modulation signal is obtained.

Description

Digit pulse shaping intermediate frequency Modulation method
Technical field
The present invention relates in a kind of satellite communication field, Spacecraft TT&C, number pass, and baseband digital signal carries out the method for pulse shaping intermediate frequency Modulation.
Background technology
Transmitting data stream code element is square-wave signal, has unlimited wide spectrum after baseband modulation, directly carries out digital modulation to intermediate frequency carrier, transmits in band-limited wireless channel, can cause interference to closing on wireless channel.In Practical Project, generally there are two kinds of modes to process this.
First kind of way uses analog bandpass filtering device directly to block filtering frequency spectrum out of band components to modulated intermediate-freuqncy signal.This blocking can cause certain frequency spectrum to lose, be one lose hand down in a direct line from the master defeated.If it is less that modulation signal transmission bandwidth compares channel width, filter directly blocks the correct transmission that also can realize more than 98% spectrum energy, and distortion can be ignored.The second way carries out pulse shaping to spectrum modulation signal.Forming filter, in order to suppressed sidelobes, transmits after being concentrated by spectrum energy in band-limited wireless channel.Design of filter, for meeting Nyquist criteria, sends signal and can realize undistorted transmission.First kind of way is easy owing to realizing, and resources conservation is adopted in this way in satellite communication more.
Along with space flight measurement and control, the high speed development of satellite communication field, improve the availability of frequency spectrum, the demand realizing more high speed data transfer business in bandwidth efficient channel is day by day urgent.Pulse shaping technique can suppressed sidelobes, and compression spectral bandwidth, is just progressively incorporated in satellite communication field at present.But satellite signal transit requires that information rate can be arranged by 1bps stepping usually, this information rate be almost equal to specifying arranges in scope, design the pulse shaping intermediate frequency Modulation realized for optional sign rate modulation signal.Because the cut-off frequecy of passband parameter in Design of Shaping Filter is relevant to signal sampling rate and character rate respectively, namely correspondence one mode filter coefficient can be formed in theory to specific character rate, this will cause great resource occupation and be difficult to realize, process the mode of speed piecewise approximation even if adopt, resource occupation is also huge.How reasonable in design pulse shaping modulation circuit of intermediate frequency, realize resources conservation, signal undistorted transmission is a difficult point.
Summary of the invention
In order to solve above-mentioned technical barrier, the invention provides one and realizing reliably easy, resources conservation, be applicable to the digit pulse shaping intermediate frequency Modulation method that optional sign speed can be established.
Above-mentioned purpose of the present invention can be realized by following measures: a kind of digit pulse shaping intermediate frequency Modulation method, and first it is characterized in that comprising the steps: becomes I, Q two tributary signal by baseband digital signal through constellation mapping; Two branch road I, Q signal carry out L doubly upper sampling respectively by upper sampler, and will obtain speed is R soversampled signals through forming filter filtering complete I, Q branch road baseband frequency spectrum be shaped; Then direct frequency synthesizing device DDS is incorporated in interpolation filter, in interpolation filter, respectively interpolation is carried out to I, Q branch road with digital to analog converter DA sample rate, complete the conversion of sampling rate; Involutory road I, Q signal send digital to analog converter DA to be reconstructed into analog signal after carrying out digital intermediate frequency modulation; Analog signal through analog bandpass filtering device filter out-band external spectrum, thus obtains the modulated intermediate frequency signal of modulated shaping.
The present invention has following beneficial effect compared to prior art:
The present invention, by configuration DDS phase control words, can realize not changing in circuit structure situation, complete pulse shaping intermediate frequency Modulation to any scheduled rate modulation signal.Circuit structure of the present invention, the design of forming filter departs from completely in character rate, according to specific shaping window demand, only need design 1 group of filter coefficient, save resource occupation greatly; Meanwhile, direct frequency synthesizing device DDS is incorporated in interpolation filter the conversion completing sampling rate by the present invention, is easy to realize, and method is reliably easy; Further, digital signal is mapped as IQ branch road and processes respectively, does not force agreement, be specially adapted to the pulse shaping intermediate frequency Modulation of Different Modulations digital signal to the modulation system of digital signal.
Below in conjunction with the drawings and specific embodiments, this method is further illustrated.
Accompanying drawing explanation
Fig. 1 is digit pulse shaping modulation circuit of intermediate frequency theory diagram involved in the present invention.
Embodiment
Consult Fig. 1.In embodiment described below, first baseband digital signal is become I, Q two tributary signal through constellation mapping; Two branch road I, Q signal carry out L doubly upper sampling respectively by upper sampler, and will obtain speed is R soversampled signals through forming filter filtering complete I, Q branch road baseband frequency spectrum be shaped; Then direct frequency synthesizing device DDS is incorporated in interpolation filter, in interpolation filter, respectively interpolation is carried out to I, Q branch road with digital to analog converter DA sample rate, complete the conversion of sampling rate; Involutory road I, Q signal send digital to analog converter DA to be reconstructed into analog signal after carrying out digital intermediate frequency modulation; Analog signal through analog bandpass filtering device filter out-band external spectrum, thus obtains the modulated intermediate frequency signal of modulated shaping.
The shaping window function that forming filter adopts is not limit, and design of filter has nothing to do with supplied with digital signal speed or spectral bandwidth, only needs to meet passband normalization cut-off frequency f cutfor:
f c u t = 1 2 × L
In formula, multiple that L representative is sampled is natural number, the desirable L=4 of representative value.
The interpolation filter transfer function of design is:
y ( kT i ) = Σ i = - N / 2 N / 2 - 1 x [ ( m - i ) R s ] h [ ( i + μ ) R s ]
In formula, N is interpolation filter exponent number; T ibe i-th and export sampling period, i.e. i-th digital to analog converter DA sampling clock cycle; R sinput sample frequency, i.e. oversampled digital signal sample frequency; μ is sampling rate conversion factor, and its accounting equation is:
μ＝k-mR DA/R s
In formula, k, m are integer, and m is for meeting m≤kT ir smaximum integer.Sampling rate conversion factor μ value is realized by direct frequency synthesizing device DDS, and DDS phase control words is:
p h a s e = R s R D A × 2 M
In formula, R sfor the modulation symbol speed after upper sampling, R dAfor DA sample clock frequency, M is DDS phase control words bit wide.

Claims (5)

1. a digit pulse shaping intermediate frequency Modulation method, is characterized in that comprising the steps: first baseband digital signal being become I, Q two tributary signal through constellation mapping; Two branch road I, Q signal carry out L doubly upper sampling respectively by upper sampler, and will obtain speed is R soversampled signals through forming filter filtering complete I, Q branch road baseband frequency spectrum be shaped; Then direct frequency synthesizing device DDS is incorporated in interpolation filter, in interpolation filter, respectively interpolation is carried out to I, Q branch road with digital to analog converter DA sample rate, complete the conversion of sampling rate; Involutory road I, Q signal send digital to analog converter DA to be reconstructed into analog signal after carrying out digital intermediate frequency modulation; Analog signal through analog bandpass filtering device filter out-band external spectrum, thus obtains the modulated intermediate frequency signal of modulated shaping.
2. by digit pulse shaping intermediate frequency Modulation method according to claim 1, it is characterized in that: the shaping window function that forming filter adopts is not limit, design of filter has nothing to do with supplied with digital signal speed or spectral bandwidth, only needs to meet passband normalization cut-off frequency f cutfor:
f c u t = 1 2 × L
In formula, multiple that L representative is sampled is natural number.
3., by digit pulse shaping intermediate frequency Modulation method according to claim 1, it is characterized in that: transfer function set by interpolation filter is:
y ( kT i ) = Σ i = - N / 2 N / 2 - 1 x [ ( m - i ) R s ] h [ ( i + μ ) R s ]
In formula, N is interpolation filter exponent number; T ibe i-th and export sampling period, i.e. i-th digital to analog converter DA sampling clock cycle; R sinput sample frequency, i.e. oversampled digital signal sample frequency; μ is sampling rate conversion factor.
4., by digit pulse shaping intermediate frequency Modulation method according to claim 3, it is characterized in that: the accounting equation of sampling rate conversion factor μ is:
μ＝k-mR DA/R s
In formula, k, m are integer, and m is for meeting m≤kT ir smaximum integer.
5., by the digit pulse shaping intermediate frequency Modulation method described in claim 3 or 4, it is characterized in that, interpolation filter sampling rate conversion factor μ value is realized by direct frequency synthesizing device DDS, and DDS phase control words is:
p h a s e = R s R D A × 2 M
In formula, R sfor the modulation symbol speed after upper sampling, R dAfor DA sample clock frequency, M is DDS phase control words bit wide.By configuration DDS phase control words, can realize not changing in circuit structure situation, to the data signal rate variable sampling rate preset arbitrarily to digital to analog converter DA sample frequency.
CN201510786356.7A 2015-11-16 2015-11-16 Digital pulse shaping intermediate-frequency modulation method Pending CN105471794A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
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CN107707263A (en) * 2017-08-04 2018-02-16 上海航天电子有限公司 Adapt to the universal integrated remote measurement ground checkout equipment of wide scope code check
CN112346091A (en) * 2020-10-20 2021-02-09 中国电子科技集团公司第五十四研究所 Non-homologous data receiving and modulating device based on digital resampling

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WO2012088926A1 (en) * 2010-12-30 2012-07-05 中兴通讯股份有限公司 Method and device for dealing with signal transmission with different bandwidths in wireless communication system
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CN101257482A (en) * 2008-01-31 2008-09-03 清华大学 Method and device for realizing digital baseband variable velocity to convert modulating system
WO2012088926A1 (en) * 2010-12-30 2012-07-05 中兴通讯股份有限公司 Method and device for dealing with signal transmission with different bandwidths in wireless communication system
CN103269222A (en) * 2013-04-23 2013-08-28 中国电子科技集团公司第四十一研究所 Achieving method and device of variable code element rate vector signal

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107707263A (en) * 2017-08-04 2018-02-16 上海航天电子有限公司 Adapt to the universal integrated remote measurement ground checkout equipment of wide scope code check
CN112346091A (en) * 2020-10-20 2021-02-09 中国电子科技集团公司第五十四研究所 Non-homologous data receiving and modulating device based on digital resampling
CN112346091B (en) * 2020-10-20 2022-07-01 中国电子科技集团公司第五十四研究所 Digital resampling-based non-homologous data receiving and modulating device

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Application publication date: 20160406