CN110719243B - Adaptive demodulation method and device for linear frequency modulation signal - Google Patents
Adaptive demodulation method and device for linear frequency modulation signal Download PDFInfo
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- CN110719243B CN110719243B CN201911270254.4A CN201911270254A CN110719243B CN 110719243 B CN110719243 B CN 110719243B CN 201911270254 A CN201911270254 A CN 201911270254A CN 110719243 B CN110719243 B CN 110719243B
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- H04B1/69—Spread spectrum techniques
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
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- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
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- H04B2001/6912—Spread spectrum techniques using chirp
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Abstract
The technical scheme of the invention compares the SF value of the linear frequency modulation signal with the current value of the Spreading Factor (SF) within the searching time through a certain searching time set by the timer, if the SF value is the same as the current value of the Spreading Factor (SF), the demodulation is carried out, if the SF value is different, the current value of the SF is reset, therefore, the linear frequency modulation signals with different SF values can be received and demodulated only by arranging one demodulation device at the receiving device end, the circuit scale is greatly reduced, and the power consumption and the cost are reduced.
Description
Technical Field
The present invention relates to the field of signal processing technologies, and in particular, to a method and an apparatus for adaptively demodulating a linear frequency modulated signal.
Background
A Linear Frequency Modulation (LFM) signal, also called a Chirp signal, is a special non-stationary signal, and a phase spectrum thereof has a square law characteristic, and a large compression ratio can be obtained in a pulse compression process. The Chirp spread spectrum modulation technology is a linear frequency modulation spread spectrum technology. The technology uses a Chirp signal with a certain Bandwidth (BW) and duration length T as a Symbol (Symbol) to carry modulation information. When the signal bandwidth BW is a fixed value, different Spreading Factors (SFs) can be realized by changing the duration length T.
In a wireless networking system based on the Chirp modulation technique, a plurality of terminals are placed on the same frequency channel, and each terminal uses the same signal bandwidth BW but uses a different spreading factor SF. A typical base station receiving apparatus implements the above automatic search and demodulation method by setting a demodulator for each possible spreading factor SF, and therefore, a plurality of demodulators are usually required to be set in a receiving apparatus to satisfy the requirements for demodulating different spreading factor SF values. This has a disadvantage that the circuit scale is large when implemented with a hardware circuit, resulting in high cost and high power consumption.
Disclosure of Invention
The technical scheme of the invention solves the problems of reducing the circuit scale and reducing the power consumption and the cost.
To solve the above problem, the present invention provides an adaptive demodulation method for a chirp signal, wherein the demodulation method uses a demodulation unit, and comprises: step S1, setting the current value of the spreading factor SF to be different from the previous value, wherein the current value of the spreading factor SF is one of N preset spreading factor SF values, the setting mode is a cycle setting, and each cycle comprises the N preset spreading factor SF values; step S2, starting a timer, starting timing, searching for a linear frequency modulation signal within the search time set by the timer, acquiring the spreading factor SF value of the linear frequency modulation signal, comparing the spreading factor SF value of the linear frequency modulation signal with the current value of the spreading factor SF, and if the values are different, turning to step S1 when the search time is over; if yes, the timing is stopped, and the process goes to step S3; step S3, keeping the current value of the spreading factor SF, demodulating the chirp signal until the demodulation is finished, and then go to step S1.
Optionally, the search time set by the timer is determined according to the current value of the spreading factor SF.
Optionally, the search time set by the timer is equal to Symbol duration T corresponding to the current value of spreading factor SF.
Optionally, the step S3 further includes: and judging whether the demodulation of the linear frequency modulation signal is finished or not.
The present invention also provides an adaptive demodulation apparatus for a chirp signal, comprising: the device comprises a configuration unit, a timer, a search comparison unit and a demodulation unit, wherein the configuration unit is used for setting the current value of the spreading factor SF to be different from the previous value, the current value of the spreading factor SF is one of N preset spreading factor SF values, the setting mode is set in a cycle mode, and each cycle comprises the N preset spreading factor SF values; the timer is used for setting search time and timing; the search comparison unit is used for searching for a chirp signal, acquiring a Spreading Factor (SF) value of the chirp signal within search time set by the timer, comparing the SF value of the chirp signal with a current value of the SF, if the SF value is different from the current value of the SF, ending the search when the set search time is over, and starting the configuration unit; if the two signals are the same, the timer stops working, and the demodulation unit starts; and the demodulation unit is used for keeping the current value of the spreading factor SF, demodulating the linear frequency modulation signal until the demodulation is finished, and starting the configuration unit.
Optionally, the timer configures a current timing mode according to the current value of the spreading factor SF.
Optionally, the demodulation unit further includes a selection module, and the selection module is configured to determine whether demodulation of the chirp signal is finished.
Compared with the prior art, the technical scheme of the embodiment of the invention has the following beneficial effects: the spread spectrum factor SF value of the linear frequency modulation signal is compared with the current value of the spread spectrum factor SF within the searching time through a certain searching time set by the timer, if the current value of the spread spectrum factor SF is the same, demodulation is carried out, if the current value of the spread spectrum factor SF is different, the current value of the spread spectrum factor SF is reset, therefore, the linear frequency modulation signals with different spread spectrum factor SF values can be received and demodulated only by arranging one demodulation device at a receiving device end, the circuit scale is greatly reduced, and the power consumption and the cost are reduced.
Drawings
FIG. 1 is a flowchart of a demodulation method according to the present embodiment;
FIG. 2 is a graph of time versus frequency for three different spreading factors SF;
fig. 3 is a schematic diagram of a demodulation apparatus in this embodiment.
Detailed Description
In the related art, a receiving apparatus is provided with one demodulator for each possible spreading factor SF value, so that multiple demodulators are required to be provided in the receiving apparatus to meet the requirement of demodulating different spreading factor SF values, so that the circuit scale is very large, and the problems of high power consumption and high cost are caused.
According to the invention, through a certain search time set by the timer, the spread spectrum factor SF value of the linear frequency modulation signal is compared with the current value of the spread spectrum factor SF within the search time, if the spread spectrum factor SF value is the same as the current value of the spread spectrum factor SF, demodulation is carried out, and if the spread spectrum factor SF value is different from the current value of the spread spectrum factor SF, the current value of the spread spectrum factor SF is reset, so that the linear frequency modulation signals with different spread spectrum factor SF values can be received and demodulated only by arranging one demodulation device at a receiving device end, the circuit scale is greatly reduced, and the power consumption and.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
An embodiment of the present invention provides a method for adaptively demodulating a chirp signal, which is described in detail below with reference to fig. 1 through specific steps.
Step S1, setting the current value of spreading factor SF to a demodulation mode different from the previous value, where the current value of spreading factor SF is one of N preset spreading factor SF values, the setting mode is a cycle setting, and each cycle includes the N preset spreading factor SF values.
In practical applications, it is known that data is transmitted in a packetized manner in a radio communication system based on the burst communication scheme. A preamble (preamble) of a certain length is set at the header of each packet. In chirp spread spectrum communication, a radio receiving apparatus identifies packet data and a spreading factor thereof based on a preamble.
The embodiment of the invention provides a system with specific parameters, which comprises the following parameters: the working wireless channel is 433.0 MHz; n is 6, BW is 125 KHz; the spreading factor SF is defined to satisfy the following relation with BW and Symbol time length T: 1/BW (2^ SF) ═ T; the spread spectrum factor SF is defined to have the value range of 7, 8, 9, 10, 11 and 12. Therefore, in this embodiment, the spreading factor SF may be one of 7, 8, 9, 10, 11, and 12.
Step S2, starting a timer, starting timing, searching for a linear frequency modulation signal within the search time set by the timer, acquiring the spreading factor SF value of the linear frequency modulation signal, comparing the spreading factor SF value of the linear frequency modulation signal with the current value of the spreading factor SF, and if the values are different, turning to step S1 when the search time is over; if the result is the same, the timer is stopped, and the process proceeds to step S3.
Referring to fig. 2, the current timing manner of the timer is determined according to the current value of the spreading factor SF. Specifically, the search time set by the timer is equal to Symbol duration T corresponding to the current value of spreading factor SF, and can be calculated according to the formula, assuming that when the value of spreading factor SF is 7, T is 1 ms; when the spreading factor SF value is 8, T is 2 ms. Therefore, when the current value of the spreading factor SF is 7, the search time set by the timer is 1 ms; when the current value of the spreading factor SF is 8, the search time set by the timer is 2 ms.
Assume one: searching for a chirp signal within 1ms of the search time set by the timer, acquiring that the spreading factor SF value of the chirp signal is 8 and the current value is 7 are different, then going to step S1, that is, setting the current value of the spreading factor SF to be the next value of the spreading factor SF of 8, going to step S2, searching for a chirp signal within 2ms of the search time set by the timer, acquiring that the spreading factor SF value of the chirp signal is 8 and the current value is 8, then going to step S3, and simultaneously terminating the timer.
Step S3, keeping the current value of the spreading factor SF, demodulating the chirp signal until the demodulation is finished, and then go to step S1. Specifically, in a case of assuming that the current value of the spreading factor SF is 8, the spreading factor SF is maintained at 8, and demodulation of the chirp signal is started until the demodulation is finished, and the process goes to step S1.
Step S3 further includes: and judging whether the demodulation of the linear frequency modulation signal is finished or not. In this embodiment, if the demodulation is finished, the process goes to step S1, and if the demodulation is not finished, the demodulation is continued.
Assume two: in another case of this embodiment, a chirp signal is searched within 1ms of the search time set by the timer, and if the spreading factor SF value of the chirp signal is obtained to be 7 and the current value is 7, the process goes to step S3, and the timer is terminated at the same time, the current value of the spreading factor SF is maintained, and the chirp signal is demodulated until the demodulation is finished. Go to step S1, and so on.
In the present invention, this scheme avoids the need to set multiple demodulation means for different spreading factor SF values. According to the scheme, only one demodulation device is needed to be arranged, signals are searched in a time-sharing mode, the spreading factor SF value of the linear frequency modulation signals is compared with the current value of the spreading factor SF, if the spreading factor SF value is the same as the current value of the spreading factor SF, demodulation is carried out, if the spreading factor SF value is different from the current value of the spreading factor SF, the current value of the spreading factor SF is reset, the circuit scale is greatly reduced, and the power consumption and the.
Referring to fig. 3, an adaptive demodulation apparatus 30 for a chirp signal in an embodiment of the present invention is provided, including: configuration unit 301, search comparison unit 302, demodulation unit 303, timer 304, wherein: the configuration unit 301 is configured to set a current value of a spreading factor SF to a demodulation mode different from a previous value, where the current value of the spreading factor SF is one of N preset spreading factor SF values, a setting manner is a cycle setting, and each cycle includes the N preset spreading factor SF values; the timer 304 is used for setting the search time and timing; the search comparing unit 302 is configured to search for a chirp signal, acquire a spreading factor SF value of the chirp signal within a search time set by the timer 304, compare the spreading factor SF value of the chirp signal with a current value of the spreading factor SF, if the spreading factor SF value is different from the current value of the spreading factor SF, end the search when the set search time ends, and start the configuration unit 301; if the two signals are the same, the demodulation unit 303 is started; the demodulation unit 303 is configured to maintain a current value of the spreading factor SF, demodulate the chirp signal until demodulation is completed, and start the configuration unit 301.
In the embodiment of the present invention, the timer 304 is configured to stop timing when the spreading factor SF value of the chirp signal is the same as the current spreading factor SF value.
In this embodiment of the present invention, the timer 304 configures a current timing mode according to the current value of the spreading factor SF.
In this embodiment of the present invention, the demodulation unit further includes a selection module, and the selection module is configured to determine whether demodulation of the chirp signal is finished.
An embodiment of the present invention provides an apparatus for adaptively demodulating a chirp signal, including a memory and a processor, where the memory stores computer instructions executable on the processor, and the processor executes the computer instructions to perform the steps of the method for adaptively demodulating a chirp signal provided in the above embodiment of the present invention.
Those skilled in the art will appreciate that all or part of the steps in the methods of the above embodiments may be implemented by instructing the relevant hardware through a program, which may be stored in a computer-readable storage medium, and the storage medium may include: ROM, RAM, magnetic or optical disks, and the like.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (8)
1. A method for adaptive demodulation of a chirp signal, the demodulation method using a demodulation unit, comprising:
step S1, setting the current value of the spreading factor SF to be different from the previous value, wherein the current value of the spreading factor SF is one of N preset spreading factor SF values, the setting mode is a cycle setting, and each cycle comprises the N preset spreading factor SF values; step S2, starting a timer, starting timing, searching for a linear frequency modulation signal within the search time set by the timer, acquiring the spreading factor SF value of the linear frequency modulation signal, comparing the spreading factor SF value of the linear frequency modulation signal with the current value of the spreading factor SF,
if not, when the search time is over, go to step S1;
if yes, the timing is stopped, and the process goes to step S3;
step S3, keeping the current value of the spreading factor SF, demodulating the chirp signal until the demodulation is finished, and then go to step S1.
2. A method for adaptive demodulation of a chirp signal in accordance with claim 1, wherein the search time set by the timer is determined in accordance with the current value of the spreading factor SF.
3. The method as claimed in claim 2, wherein the search time set by the timer is equal to Symbol duration T corresponding to the current value of spreading factor SF.
4. The method for adaptively demodulating a chirp signal according to claim 1, wherein the step S3 further comprises: and judging whether the demodulation of the linear frequency modulation signal is finished or not.
5. An apparatus for adaptively demodulating a chirp signal, comprising: a configuration unit, a timer, a search comparison unit and a demodulation unit, wherein,
the configuration unit is used for setting the current value of the spreading factor SF to be different from the previous value, the current value of the spreading factor SF is one of N preset spreading factor SF values, the setting mode is set in a cycle mode, and each cycle comprises the N preset spreading factor SF values;
the timer is used for setting search time and timing;
the searching and comparing unit is used for searching for a linear frequency modulation signal, acquiring a spread spectrum factor SF value of the linear frequency modulation signal within the searching time set by the timer, comparing the spread spectrum factor SF value of the linear frequency modulation signal with the current value of the spread spectrum factor SF,
if the set search time is different from the set search time, ending the search when the set search time is ended, and starting the configuration unit;
if the two signals are the same, the timer stops working, and the demodulation unit starts;
and the demodulation unit is used for keeping the current value of the spreading factor SF, demodulating the linear frequency modulation signal until the demodulation is finished, and starting the configuration unit.
6. An apparatus for adaptive demodulation of a chirp signal as claimed in claim 5, wherein said timer configures a current timing mode based on a current value of said spreading factor SF.
7. An apparatus for adaptive demodulation of a chirp signal as claimed in claim 5 wherein said demodulation unit further comprises a selection module for determining whether demodulation of the chirp signal is complete.
8. A user equipment comprising a memory and a processor, said memory having stored thereon computer instructions executable on said processor, wherein said processor when executing said computer instructions performs the steps of the method for adaptive demodulation of chirp signals according to any one of claims 1 to 4.
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