CN103457892B - A kind of carrier extract new method for binary frequency shift keying signal - Google Patents

Abstract

The invention belongs to the communication technical field in electronic information technical field, relate to Principle of Communication and signal processing subject, it is specifically related to a kind of carrier extract new method for Binary Frequency Shift Keying (Binary Frequency Shift Keying is called for short 2FSK) signal；The input signal of this module has two kinds, and a kind of is the 2FSK modulated signal received, and another kind is bit synchronization signal, and output is continuous print central carrier signal, this central carrier signal；It provides the benefit that: is capable of the detection of continuous print carrier error, thus obtains the higher coherent carrier of precision.

Description

A kind of carrier extract new method for binary frequency shift keying signal

Technical field

The invention belongs to the communication technical field in electronic information technical field, relate to Principle of Communication and signal processing Section, is specifically related to a kind of for Binary Frequency Shift Keying (Binary Frequency Shift Keying is called for short 2FSK) signal Carrier extract new method.

Background technology

In a communications system, receiving terminal wants to recover original digital baseband signal from the high-frequency signal modulated, It is accomplished by the docking collection of letters number to be demodulated.Demodulation method currently mainly is divided into coherent demodulation and the big class of non-coherent demodulation two；Its The decoding performance of middle coherent demodulation method is the most excellent, and under normal conditions, coherent demodulation has 3dB's relative to non-coherent demodulation Gain, but coherent demodulation needs to recover coherent carrier, for 2FSK signal, owing to having not for different digital baseband codes Same carrier wave (correspondence respectivelyWith), currently in the coherent demodulation method that 2FSK signal uses, carrier extract is led to Around-France frequently with square, the principle of this method is to obtain two different carrier frequency points respectively through two wave filter, this The shortcoming of method is: the two-way carrier signal obtained is discontinuous.Signal-noise ratio threshold and the bit error rate will be increased, thus reduce Decoding performance.Therefore, the carrier extract technology of a kind of continuous tracking is studied for realizing more excellent solution for 2FSK modulated signal Code performance has the most real meaning.

Summary of the invention

The present invention be directed to 2FSK modulated signal carry out during coherent demodulation method, providing a kind of new carrier extract method, energy Enough realize the reproduction of continuous print coherent carrier.

To achieve these goals, technical scheme is as follows:

A kind of new carrier extract method for 2FSK signal is realized by carrier extract module, the input signal of this module Having two kinds, a kind of is the 2FSK modulated signal received, and another kind is bit synchronization signal, and output is continuous print centered carrier letter Number, this central carrier signal。

First digital controlled oscillator in carrier extract module produces the central carrier signal that there is certain phase error, should Signal is divided into two-way, wherein leads up to 90 ° of phase shift block, thus obtains the orthogonal central carrier signal of two-way, more respectively with connect The 2FSK modulated signal received carries out multiplication operation, and the result obtained, respectively through a band filter, filters multiplication operation The high fdrequency component obtained, obtains comprising the two-way orthogonal signalling of center carrier frequence phase error information, then through a phase discriminator mould Block, it is possible to be digitally controlled existence between the center carrier frequence center carrier frequence corresponding with 2FSK modulated signal that agitator produces Control information, shown in the mathematical model of this information such as formula (a).

(a)

Wherein,Phase error signal for phase discriminator output；For two frequencies that digital baseband signal is corresponding Frequency-splitting between point and center carrier frequencies, i.e.；Produce for digital controlled oscillator Phase error between the center carrier frequence that center carrier frequence is corresponding with 2FSK modulated signal；For digital baseband signal at that time Value.

In order to eliminate, formula (a) comprises frequency difference information, phase error signal is divided into two-way, wherein a-road-through Crossing a chronotron, the time delay of this chronotron is controlled by the bit synchronization signal inputted often, afterwards, by this two paths of signals by one Individual multiplier, filters high fdrequency component through a loop filter the most again, is the most only comprised the control of phase error information Signal, shown in the mathematical model of this signal such as formula (b).

(b)

Wherein,For the phase error control signal finally given, it can be seen that this signal only comprises numerical control and shakes Swing the phase error information between the center carrier frequence center carrier frequence corresponding with 2FSK modulated signal that device produces。

Finally this phase error control signal is used for controlling digital controlled oscillator, so that in the output of carrier extract module Heart carrier signal realizes the purpose with frequency homophase with the central carrier signal in the 2FSK modulated signal that receives.

The invention has the beneficial effects as follows: utilize this invention, it is possible to realize the detection of continuous print carrier error, thus obtain precision Higher coherent carrier.

Accompanying drawing explanation

Fig. 1 is the input/output interface figure of the carrier extract module map of the present invention；

Fig. 2 be the carrier extract extracting method of the present invention realize structured flowchart；

Fig. 3 is to utilize the present invention at 2FSK coherent receiver logic diagram.

Reference is as follows: 1, carrier extract module, and 2,2FSK modulated signal, 3, bit synchronization signal, 4, centered carrier letter Number, 5, multiplier, 6,90 ° of phase shift block, 7, band filter, 8, digital controlled oscillator, 9, phase discriminator, 10, chronotron, 11, ring Path filter, 12, coherent demodulation module, 13, sampling judging module.

Detailed description of the invention

The 2FSK carrier extract module of the present invention is a functional module in 2FSK signal receiver, needs to mate rear end Coherent demodulation module and sampling judging module jointly realize the demodulation output of digital baseband signal to 2FSK modulated signal, tool The composition structure of body is as shown in Figure 3.

Using vector signal generator to produce a digital baseband signal is 0 yard and the 1 yard 2FSK modulation letter being alternately present Number.Mid frequency is set to 455KHz, and frequency deviation is ± 1.2KHz.

2FSK modulated signal used by test is divided into two-way, and the input of a road access carrier extraction module, another road connects Enter the input of coherent demodulation module (12).

The data-interface of the bit synchronization signal access carrier extraction module that sampling judging module (13) exports.

The output interface of the carrier extract module of the present invention is linked into coherent demodulation module.

Oscillograph is used to observe the output interface of sampling judging module, it is possible to obtain 0 yard and 1 yard be alternately present.

Use the output interface of the carrier extract module of the oscillograph observation present invention, it can be seen that in the carrier wave of tenacious tracking Frequency of heart, is 455KHz through testing this carrier frequency, and produces the center frequency point of frequency with frequency with vector signal generator Homophase.

Claims (1)

1. the carrier extract new method for binary frequency shift keying signal, it is characterised in that concrete grammar is as follows: 1) make Producing a digital baseband signal with vector signal generator is 0 yard and the 1 yard 2FSK modulated signal being alternately present；2) will test Signal is divided into two-way, the input interface of a road access carrier extraction module, and the input of coherent demodulator is accessed on a road；3) sampling The data-interface of the bit synchronization signal access carrier extraction module of decision device output；4) output interface of carrier extract module accesses To coherent demodulator；5) use oscillograph to observe the output interface of sampling judging module, obtain 0 yard and 1 yard be alternately present；6) Using oscillograph to observe the output interface of carrier extract module, the center frequency point obtaining producing frequency with vector signal generator is same Frequently homophase the centre carrier frequency of tenacious tracking；

Carrier extract method for binary frequency shift keying signal is to be realized by carrier extract module, the input signal of this module Having two kinds, a kind of is the 2FSK modulated signal received, and another kind is bit synchronization signal, and output is continuous print centered carrier letter Number, this central carrier signal f_c=(f₁+f₂)/2；

First digital controlled oscillator in carrier extract module produces the central carrier signal that there is certain phase error, by this signal Be divided into two-way, wherein lead up to 90 ° of phase shift block, thus obtain the orthogonal central carrier signal of two-way, more respectively with receive 2FSK modulated signal carry out multiplication operation, the result obtained, respectively through a band filter, filters multiplication operation and obtains High fdrequency component, obtain comprising the two-way orthogonal signalling of center carrier frequence phase error information, then through a phase discriminator module, just The error of existence between the center carrier frequence center carrier frequence corresponding with 2FSK modulated signal that agitator produces can be digitally controlled Information, shown in the mathematical model of this information such as formula (a):

$f_{\mathrm{\θ}}\left(t\right)=\left\{\begin{array}{cc}\sin \[2{\mathrm{\Δ\ω}}_{half}t+2\mathrm{\θ}\]& {\mathrm{\α}}_k=-1\\ \sin \[2{\mathrm{\Δ\ω}}_{half}t+(\mathrm{\π}-2\mathrm{\θ})\]& {\mathrm{\α}}_k=+1\end{array}\right.---\left(a\right)$

Wherein, f_θT () is the phase error signal of phase discriminator output, Δ ω_halfFor two frequency bins corresponding to digital baseband signal with Frequency-splitting between center carrier frequencies, i.e. Δ ω_half=| f₁-f_c|=| f₂-f_c|, θ be digital controlled oscillator produce center Phase error between the center carrier frequence that carrier frequency is corresponding with 2FSK modulated signal, α_kFor digital baseband signal value at that time；

In order to eliminate, formula (a) comprises frequency difference information Δ ω_half, phase error signal is divided into two-way, wherein leads up to one Individual chronotron, the time delay of this chronotron is controlled by the bit synchronization signal inputted often, afterwards, is taken advantage of by one by this two paths of signals Musical instruments used in a Buddhist or Taoist mass, filters high fdrequency component through a loop filter the most again, is the most only comprised the control signal of phase error information, Shown in the mathematical model of this signal such as formula (b):

$f_{\mathrm{\θ}L}\left(t\right)=\left\{\begin{array}{cc}-\frac{1}{2}& {\mathrm{\α}}_k={\mathrm{\α}}_{k-1}\\ \±\frac{1}{2}sin\left(4\mathrm{\θ}\right)& {\mathrm{\α}}_k\≠{\mathrm{\α}}_{k-1}\end{array}\right.---\left(b\right)$

Wherein, f_θLT () is the phase error control signal finally given, it can be seen that only comprise digital controlled oscillator in this signal and produce Phase error information θ between the center carrier frequence that raw center carrier frequence is corresponding with 2FSK modulated signal；

Finally this phase error control signal is used for controlling digital controlled oscillator, so that the center of carrier extract module output carries Ripple signal realizes the purpose with frequency homophase with the central carrier signal in the 2FSK modulated signal that receives.