CN100579094C - A kind of receiving handling method of frequency shift keyed signals - Google Patents
A kind of receiving handling method of frequency shift keyed signals Download PDFInfo
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Abstract
The invention discloses the receiving handling method of a kind of frequency shift keying (FSK) signal, one frame, one frame ground receives fsk signal and handles, this method comprises: 1) level parameters to received signal detects in real time, when the level parameters of received signal surpasses predetermined value, judge and receive frame signal, with phase shift coherent demodulation mode this frame signal is carried out demodulation, and carry out signal identification as the reference line with demodulation result amplitude zero line; During the regular signal 2) stipulated in identifying the frame synchronization head of this frame signal, the result samples to phase shift coherent demodulation, calculates the demodulation result amplitude mean value of two frequency signals of fsk signal; 3) with step 2) mean value that obtains is as the reference line, and the follow-up signal of this frame is carried out signal identification.Processing method of the present invention still can accurately receive and discern, improved the accuracy, the reliability that receive existing two frequencies certain interference or signal to exist under the situation of certain level difference.
Description
Technical field
The present invention relates to the signal processing technology in the communication system, the receiving handling method of particularly a kind of frequency shift keying (FSK) signal.
Background technology
At present, in the communication system information interaction, traditional aspects such as Dual Tone Multifrequency, because interactive speed is slow, can't meet of the requirement of present information interaction, and it is a lot of soon to use the fsk signal mode to carry out the signal interactive speed, particularly when transmission information is more to speed, this advantage is more obvious, so has used the fsk signal mode more and more in the communication system.
(Frequency Shift Keying, FSK) signal is a kind of signal that is used to carry out high speed data transfer to frequency shift keying.It has various ways, and more common a kind of form is the desired form of BELL202.The selected fsk signal of BELL202 is the signal of 1200Hz and 2200Hz, uses the signal indication logical one of 1200Hz, uses the signal indication logical zero of 2200Hz.The baud rate that information transmits is 1200 bauds.
On physical circuit, the load mode of a frame signal is referring to Fig. 1, and Fig. 1 is a fsk signal load mode schematic diagram.Fig. 1 has illustrated the roughly transport process of fsk signal, supposes that frequency of utilization is the signal indication logical one of f0, and frequency of utilization is the signal indication logical zero of f1.When the signal that transmits was 101 (binary systems), the signal on the circuit just as shown in Figure 1.Recognition methods for fsk signal is a lot, considers actual situation, can select for use the mode of phase shift coherent demodulation to carry out the identification of fsk signal usually.
Referring to Fig. 2, Fig. 3, fsk signal is that the form of a frame one frame sends.Fig. 2 is a part FSK primary signal, and original as can see from Figure 2 binary data signal is represented by the frequency signal of density interphase.Fig. 3 is for ideally having carried out figure after the phase shift coherent demodulation to the fsk signal among Fig. 2, and the b line is the absolute zero line of demodulation result amplitude among Fig. 3.Obviously, in this time, the waveform after the demodulation is similar to square-wave signal as can be seen, can discern the signal of reception according to this.For example, if it is 0 that the amplitude of demodulation result is less than or equal to 0, greater than 0 being 1, promptly the signal of demodulation result amplitude below absolute zero line is 0 among Fig. 3, signal above absolute zero line is 1, and therefore the signal that can obtain receiving from left to right is: 0101010100.
Fsk signal is that the form of a frame one frame sends at interval, and the form of frame is referring to Fig. 4, and Fig. 4 is the frame format of fsk signal, and as seen from Figure 4, a complete message frame comprises: frame synchronization head and frame data two parts.The frame synchronization head comprises two parts again: 01 alternate passage Seize ACK message, form the gap marker signal by complete 1.Frame data comprise the signal data of a plurality of bytes.This form mainly is to be used in aspects such as calling number identification and fixed net short message breath, and in other application, for example the frame synchronization head in the aspect frame format such as fax can be distinguished to some extent.
Existing technology is normally carried out energy measuring to signal, whether the energy by received signal reaches certain thresholding, judge whether the signal that receives is a frame normal signal, when within the energy threshold, just think normally to receive a frame fsk signal, just whole frame signal is discerned as the reference line with the absolute zero line of demodulation result with the mode of phase shift coherent demodulation.Because fsk signal has some losses or gain in communication process, for reliable reception, energy threshold is provided with lower usually, for example will be decided to be thresholding more than or equal to the signal energy of-35dBm level.Ill-considered situation can appear in such judgement: for example the useful signal level is-10dBm, noise is arranged this moment, noise signal is-35dBm, the noise signal energy of this level is still in the threshold range of accepting, and this signal can be considered to useful signal and influence the normal reception of signal this moment.
In addition, because fsk signal is made up of the signal of 2 frequencies, loss or the gain situation of the signal of these two frequencies in communication process is different.For example, frequency f0 and frequency are that the f1 level all is-10dBm when sending signal, through after the system transmissions, frequency is that the level of f0 signal becomes-15dBm, frequency is that the level of f1 signal becomes-20dBm, level difference has appearred in the signal that is to say two frequencies, and at this moment the result who carries out phase shift coherent demodulation is referring to Fig. 5, the figure when Fig. 5 has level difference for fsk signal after the demodulation.Among Fig. 5, the b line is the absolute zero line of demodulation result amplitude, obviously, this time, if still according to absolute zero line---the b line is discerned and just is easy to make mistakes, and any of signal disturbance slightly will cause wrong identification, for example, the H-I signal is current among Fig. 5 is identified as 00, if signal one is strengthened exceeding absolute zero line slightly, and can be identified as 10 or other wrong results.
As seen, prior art fsk signal receiving handling method can not guarantee accuracy, the reliability that fsk signal receives.
Summary of the invention
In view of this, the object of the present invention is to provide a kind of receiving handling method of fsk signal, improve accuracy, reliability that fsk signal receives.
For achieving the above object, technical scheme of the present invention specifically is achieved in that
The receiving handling method of a kind of frequency shift keying (FSK) signal, a frame one frame ground receives fsk signal and handles, and this method may further comprise the steps:
1) level parameters to received signal detects in real time, if the level parameters of received signal surpasses predetermined value, begin this signal to be carried out demodulation, and carry out signal with the absolute zero line of demodulation result amplitude as the reference line and discern in advance, otherwise do not discern in advance with phase shift coherent demodulation mode;
2) when identifying this signal and be the regular signal of stipulating in the frame synchronization head of a frame signal, the result samples to phase shift coherent demodulation, calculates the mean value of two frequency signal demodulation result of fsk signal amplitude;
3) with step 2) mean value that obtains is as the reference line, according to the frame structure of received signal, determines gap marker signal and frame data in this frame signal respectively, carries out signal identification.
Wherein, the described level parameters to received signal of step 1) detects in real time, can adopt the method for sliding window to carry out.
Described sliding window method can for: with N sampling point as a window, one constantly, sampling point in the window is x (1) ... x (N), level parameters in the detection window, next constantly, sampling point in the window is x (2) ... x (N+1), and this moment, level parameters was that level parameters in the former window deducts x (1), adds the level parameters behind the x (N+1).
Described level parameters detect can for: signal energy detects, or the signal amplitude average detection.
The regular signal of described identification can be the 01 alternate burst of representing the passage Seize ACK message in the identification frame synchronization head.
The described predetermined value of step 1), it is predefined the situation of loss to occur in transmission course according to signal.
Step 2) process of described identification frame synchronization head may further include, and once more the signal that receives is carried out level parameters and detects, and according to the level parameters testing result signal that receives is carried out automatic gain control, when signal level is high, reduces signal level; When signal level is low, improve signal level.
The process that the described follow-up signal to this frame of step 3) carries out signal identification may further include, and according to the frame structure of received signal, determines gap marker signal and frame data in this frame signal respectively.
By above-mentioned invention scheme as seen, the receiving handling method of this fsk signal of the present invention by the mode of twice signal trace, still can receive and discern under the situation that has certain interference reliably.Simultaneously, the characteristics that the present invention also sends at signal have been carried out the calculating of reference line, thereby having guaranteed that two frequencies at signal exist under the situation of certain level difference still can accurately receive and discern, and has improved accuracy, reliability that fsk signal receives.
Description of drawings
Fig. 1 is a fsk signal load mode schematic diagram;
Fig. 2 is part FSK primary signal figure;
Fig. 3 is for ideally having carried out figure after the phase shift coherent demodulation to the fsk signal among Fig. 2;
Fig. 4 is the frame format of fsk signal;
Figure when Fig. 5 has level difference for fsk signal after the demodulation;
Fig. 6 is the reception idiographic flow schematic diagram of present embodiment to fsk signal;
Fig. 7 is the initial fsk signal schematic diagram that receives.
Embodiment
For making the purpose, technical solutions and advantages of the present invention clearer, below in conjunction with embodiment and accompanying drawing, the present invention is described in more detail.
The present invention mainly utilizes in the fsk signal frame synchronization head agreement regulation, and the characteristics of the fixed signal of regular arrangement receive processing with the mode of phase shift coherent demodulation to signal.
Below be that embodiment is specifically described with the receiving handling method of the fsk signal of frame format shown in Figure 4.
Referring to the frame format of fsk signal shown in Figure 4, present embodiment is to have utilized 01 alternate passage Seize ACK message in its frame synchronization head to realize.The frame format of other application facet can be distinguished to some extent, and for example aspect frame format such as fax is just incomplete same with Fig. 4, and at this moment, the method for realization is as long as change accordingly according to the fixed signal of regular arrangement in its frame synchronization head.After the variation, still can receive processing with method of the present invention.
Referring to Fig. 6, present embodiment is specially the receiving course of fsk signal:
At first, step 601, level parameters is to received signal carried out real-time detection, and whether the decision level parameter surpasses predetermined value.It can be that detection to signal energy also can be that mean value to signal amplitude detects that level parameters detects, and is that the energy to signal detects in the present embodiment.The situation that in transmission course, has loss or gain according to signal, energy threshold is set, the method that is provided with is same as the prior art, in the time of in energy reaches threshold range, promptly judge the commencing signal of receiving a frame signal, and note at this moment energy value, and be used for the signal energy sliding window and detect, what carry out here is to following the tracks of the first time of signal.
Wherein, the method for energy measuring adopts the method for sliding window in real time, also can adopt additive method, fluctuation is little but the method that adopts sliding window can make energy value, when energy value upgrades, guarantees level and smooth, progressively upgrade, prevent the influence of energy value saltus step the stability of a system.
The processing method of sliding window is as follows: for example, window length is 20 points, so, at a time, the sampling point in the window is x (1) ... x (20), energy value in the record window, in next moment, the sampling point in the window is x (2) ... x (21), and this moment, energy value was that the interior energy value of last window deducts x (1), add the energy value behind the x (21), what adopt like this is exactly the method for slip.If next constantly, sampling point is x (21) in the window ... x (40), is not the method for the sliding window of usefulness just, the saltus step of energy value may occur, so present embodiment does not adopt this method.
If surpassed predetermined value, then execution in step 602, and energy is reached signal in the threshold range, use the mode of phase shift coherent demodulation to begin to discern in advance; Otherwise the signal of receiving is not discerned.When pre-identification is found on the circuit to calculate the energy of a line signal again, and note energy value at this moment when being 01 sequence in the frame signal frame synchronization head.This value will be used for gain controlling as the actual value of circuit energy.Note, because Seize ACK message 01 sequence is a fixed signal clocklike, its identification is relatively easy, therefore, though also do not finish the tracking of line signal this moment, with phase shift coherent demodulation as a result the absolute zero line of amplitude discern still and can rule out 01 sequence.
Whether adopt above-mentioned method to exist under certain noise jamming situation, can effectively improve identification is the accuracy of a frame FSK commencing signal.Fig. 7 is the initial fsk signal schematic diagram that receives.Method with above-mentioned sliding window can identify, and b is later on the signal that real fsk signal begins among Fig. 7, and the difference of the frequency of the signal that for simplicity do not draw in order to draw need be calculated current signal energy value because need carry out the problem of gain controlling.
Because in actual applications, the level range that requires receiver to receive is very big, therefore, adopts a lower thresholding to carry out usually, the requirement when hanging down to satisfy level.If this time, the level ratio of noise was higher, if for example the ab section surpassed-energy value of 35dBm, will pass through thresholding.If be used as the energy of this segment signal this time is the true energy of signal, will go wrong, therefore when identifying when being 01 signal, need carry out the calculating of primary energy again, the energy value that obtains this time is just very accurate.This energy value is used to carry out automatic gain control.So just realized under there is the situation of certain noise in signal, signal energy being followed the tracks of accurately.
Usually in order to realize that signal can both receive exactly in certain amplitude range, all need to do the automatic gain control (AGC) of certain form, obtain that energy value is also very beneficial for carrying out effective AGC accurately, present embodiment begins just signal have been carried out AGC in 01 series processing, be signal level when high, reduce signal level; When signal level is hanged down, improve signal level.Like this, can improve the accuracy of signal identification.
When judgement is found current when being 01 synchronous head, execution in step 603, the phase shift coherent demodulation result one section continuous sampling point of sampling is calculated a mean value of two frequency signal demodulation result of fsk signal amplitude, with this mean value as the follow-up reference line of discerning.When frequency is that the signal of f0 and f1 is when existing level difference, the possibility of result after the phase shift coherent demodulation as shown in Figure 5, the b line is the absolute zero line of demodulation result amplitude among Fig. 5, obviously, this time, just be easy to make mistakes if still discern according to absolute zero line, any of signal disturbance slightly will cause the unusual of reception.Among Fig. 5, the a line is a mean value line of 01 signal demodulation result amplitude, obviously, the present invention uses a line to discern as the reference line, for signal, can obtain the result accurately, also can improve simultaneously the tolerance limit of noise greatly, guarantee to realize when there is certain level difference in signal that reliable signal receives.
After mean value calculation is finished,, use this mean value to come the follow-up signal in the frame is discerned, obtain concrete frame of data information with regard to execution in step 604.
Below according to frame structure the receiving course of one frame signal is described.Being found out by frame structure shown in Figure 4, behind the alternate passage Seize ACK message of frame synchronization 01, is the complete 1 gap marker signal of forming, and is frame data then, and each byte frame data is with 0 beginning, 1 ending.According to such frame structure, the process that receives a frame signal comprises following three steps:
01 of step 1, reception predetermined quantity, for example transmit leg has sent 50 pairs 01 signals, if receiving terminal is received 20 pairs 01 signals continuously, then is judged to be and has received the passage Seize ACK message, and it is fixed that the quantity that the quantity of reception sends according to reality is come;
Step 2, receive continuous 1 after, carry out record, when receive predetermined quantity 1 the time, for example transmit leg has sent 80 1 signals, if receiving terminal is received 50 1 signals continuously, then be judged to be and received the gap marker signal, it is fixed that the quantity that the quantity of reception also sends according to reality is come;
Present embodiment has made full use of the characteristics of the frame structure of fsk signal transmission, and the process that receives is also carried out suitable division.In addition, in the reception practice of reality, the reception of occupied information 01 sequence of channel is normally quite reliable, and, because this 01 sequence itself has an average meaning, therefore, the energy of signal calculated in the process of this sequential reception, also carry out the calculating of reference zero, can not influence the reception of 01 sequence like this, and can improve the reliability that follow-up signal receives in this stage.
By the above embodiments as seen, the characteristics that the signal that the receiving handling method of this fsk signal of the present invention takes into full account sends by the mode of twice signal trace, still can receive and discern under the situation that has certain interference reliably.Simultaneously, the characteristics that the present invention also sends at signal have been carried out the calculating of reference line, thereby having guaranteed that two frequencies at signal exist under the situation of certain level difference still can accurately receive and discern, and has improved accuracy, reliability that fsk signal receives.
Claims (7)
1, the receiving handling method of a kind of frequency shift keying (FSK) signal, a frame one frame ground receives fsk signal and handles, and it is characterized in that this method may further comprise the steps:
1) level parameters to received signal detects in real time, if the level parameters of received signal surpasses predetermined value, begin this signal to be carried out demodulation, and carry out signal with the absolute zero line of demodulation result amplitude as the reference line and discern in advance, otherwise do not discern in advance with phase shift coherent demodulation mode;
2) when identifying this signal and be the regular signal of stipulating in the frame synchronization head of a frame signal, the result samples to phase shift coherent demodulation, calculates the mean value of two frequency signal demodulation result of fsk signal amplitude;
3) with step 2) mean value that obtains is as the reference line, according to the frame structure of received signal, determines gap marker signal and frame data in this frame signal respectively, carries out signal identification.
2, receiving handling method as claimed in claim 1 is characterized in that: the described level parameters to received signal of step 1) detects in real time, adopts the method for sliding window to carry out.
3, receiving handling method as claimed in claim 2, it is characterized in that, described sliding window method is: with N sampling point as a window, in a moment, the sampling point in the window is x (1) ... .x (N), the level parameters in the detection window, next constantly, sampling point in the window is x (2) ... .x (N+1), and this moment, level parameters was that level parameters in the former window deducts x (1), adds the level parameters behind the x (N+1).
As claim 1,2 or 3 described receiving handling methods, it is characterized in that 4, described level parameters detects and is: signal energy detects, or the signal amplitude average detection.
5, receiving handling method as claimed in claim 1 is characterized in that, the regular signal of described identification is: the 01 alternate burst of representing the passage Seize ACK message in the identification frame synchronization head.
6, receiving handling method as claimed in claim 1 is characterized in that: the described predetermined value of step 1) is that the situation of loss to occur according to signal in transmission course predefined.
7, receiving handling method as claimed in claim 1, it is characterized in that: step 2) process of described identification frame synchronization head further comprises, once more the signal that receives being carried out level parameters detects, according to the level parameters testing result signal that receives is carried out automatic gain control, when signal level is high, reduce signal level; When signal level is low, improve signal level.
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| CN03105352A CN100579094C (en) | 2003-02-25 | 2003-02-25 | A kind of receiving handling method of frequency shift keyed signals |
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| CN03105352A CN100579094C (en) | 2003-02-25 | 2003-02-25 | A kind of receiving handling method of frequency shift keyed signals |
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| JP5343439B2 (en) * | 2008-07-31 | 2013-11-13 | アイコム株式会社 | Frame synchronization detection circuit and FSK receiver using the same |
| CN107968757B (en) * | 2016-10-20 | 2020-12-18 | 国民技术股份有限公司 | Demodulation method and system for frequency shift keying modulation signal |
| CN107181540B (en) * | 2017-05-31 | 2021-01-22 | 珠海市杰理科技股份有限公司 | Bluetooth signal processing device and Bluetooth data frame detection method |
| CN115174325B (en) * | 2022-06-07 | 2024-02-09 | 中国南方电网有限责任公司超高压输电公司 | Double-tone FSK modulation-demodulation system for wireless energy-carrying communication |
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