JP3583932B2 - Demodulation device and demodulation method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a demodulation apparatus and a demodulation method for determining a modulation scheme from a received signal and demodulating data according to the modulation scheme.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a system for performing data communication by specifying one of a plurality of modulation schemes, for example, those described in JP-A-5-130082 and JP-A-7-122017 are known. .
[0003]
As shown in FIG. 20, the former Japanese Patent Application Laid-Open No. Hei 5-1300082 uses QPSK, which is a modulation method having high frequency use efficiency, for mobile terminals 2 and 3 close to the base station 1, and uses the base station 1 The mobile terminals 4 and 5 distant from the mobile terminal 4 and 5 use a variable modulation communication system in which communication is performed using 16QAM, which is a modulation system resistant to noise. The signal is received and its quality is checked. Based on the quality, the base station 1 is notified of the desired modulation scheme. The base station 1 checks the quality of the received signal to determine whether communication is possible with the desired modulation scheme. Judgment is made, a modulation method is designated, and communication is started.
[0004]
In the latter Japanese Unexamined Patent Publication No. Hei 7-123017, as shown in FIG. 21, an FM demodulation unit 11, a PM demodulation unit 12, and a BPSK demodulation unit 13 are provided in a receiving device, and a reception wave received by an antenna 14 is received. After the receiving unit 15 performs low noise amplification and frequency conversion to an intermediate frequency signal, the signals are distributed to the demodulation units 11, 12, and 13, and the corresponding modulation signals are input to the demodulation units 11, 12, and 13. And demodulates the signal and outputs a video signal to the signal switch 16 and outputs a demodulation determination signal to the demodulation determination circuit 17. The demodulation determination circuit 17 receives a demodulation determination signal from each demodulation unit, determines which demodulation unit is currently operating, and sends a switching control signal to the signal switch 16. The signal switch 16 receives the video signal from each demodulation unit, selects a video signal based on the demodulation determination signal from the demodulation determination circuit 17, and outputs the video signal to the monitor device 18 and the data processing device 19.
[0005]
[Problems to be solved by the invention]
However, according to the former publication, the mobile terminal must notify the base station of the desired modulation scheme, and therefore, each time there is a desire to change the modulation scheme, the mobile terminal notifies the base station of the desired modulation scheme. The setting of the modulation scheme between the base station and the mobile terminal is troublesome.
[0006]
Further, in the case of the latter publication, the receiving apparatus must be provided with a plurality of demodulators corresponding to various modulation schemes and a signal switch for selectively outputting a video signal from each of the demodulating sections. However, there was a problem that the configuration was complicated.
[0007]
Therefore, according to the first to third aspects of the present invention, it is possible to determine the modulation method on the receiving side, demodulate data according to the determination, and to simplify the configuration by using one demodulation unit. And a demodulation device capable of performing the above.
Further, the invention according to claim 3 further provides a demodulation device that can more reliably determine the modulation method.
[0008]
According to the invention of claims 4 to 6, it is possible to determine the modulation scheme on the receiving side, demodulate data according to the determination, and to simplify the configuration by using one demodulation unit. To provide a demodulation method capable of
Further, the invention according to claim 6 further provides a demodulation method capable of more reliably determining a modulation scheme.
[0009]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided an amplitude detecting means for detecting an amplitude of a received signal at an arbitrary timing between modulation symbols of a received modulated signal, and an amplitude detection result of the amplitude detecting means and a time point at which the modulation symbol is represented. The demodulation apparatus includes a determination unit that determines the modulation scheme by comparing the amplitude with the data, and a data demodulation unit that demodulates data according to the modulation scheme determined by the determination unit.
[0010]
According to a second aspect of the present invention, there is provided a received modulated signal. The in-phase component and the quadrature component detected in a plurality of stages are converted into bit data, respectively, and the combined data is represented by a continuous numerical value representing each signal point representing a modulation symbol. And performs a comparison operation with the data representing the immediately preceding signal point, based on a demodulation data table indicating the correspondence between the calculation result, the phase shift amount, and the demodulation data. Current signal point and previous signal point A phase shift amount detecting means for detecting a phase shift amount between the phase shift amounts, a determining means for determining a modulation method based on the phase shift amount detected by the phase shift amount detecting means, and a determining means for determining the phase shift amount. In a demodulation device provided with data demodulation means for demodulating in accordance with the modulation method.
[0011]
According to a third aspect of the present invention, there is provided an amplitude detecting means for detecting an amplitude of a received signal at an arbitrary timing between modulation symbols of a received modulated signal, and an amplitude detection result of the amplitude detecting means and a time point at which the modulation symbol is represented. First determining means for comparing the amplitude to determine the modulation scheme; phase shift detecting means for detecting a phase shift between modulation symbols of the received modulation signal; The demodulation apparatus includes a second determination unit that determines a modulation scheme based on the detected phase shift amount, and a data demodulation unit that demodulates data according to a determination result of each determination unit.
[0012]
According to a fourth aspect of the present invention, the amplitude of the received signal is detected at an arbitrary timing between the modulation symbols of the received modulation signal, and the detection result is compared with the amplitude at the time when the modulation symbol is represented to determine the modulation scheme. There is a demodulation method for making a decision and demodulating data in accordance with the decided modulation scheme.
[0013]
According to a fifth aspect of the present invention, there is provided a received modulated signal. The in-phase component and the quadrature component detected in a plurality of stages are converted into bit data, respectively, and the combined data is represented by a continuous numerical value representing each signal point representing a modulation symbol. And performs a comparison operation with the data representing the immediately preceding signal point, based on a demodulation data table indicating the correspondence between the calculation result, the phase shift amount, and the demodulation data. Current signal point and previous signal point There is a demodulation method in which a phase shift amount between the two is detected, a modulation scheme is determined based on the detected phase shift amount, and demodulation is performed in accordance with the modulation scheme in which the phase shift amount is determined.
[0014]
The invention according to claim 6 detects the amplitude of the received signal at an arbitrary timing between the modulation symbols of the received modulation signal, compares the detection result with the amplitude at the time when the modulation symbol is represented, and determines the modulation scheme. If the determination is not possible, subsequently, the phase shift amount between the modulation symbols of the received modulation signal is detected, the modulation method is determined based on the detected phase shift amount, and the time when the modulation method is determined is determined. The demodulation method demodulates data according to the determination result.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. In this embodiment, an example in which two modulation schemes, that is, an MSK modulation scheme and a π / 4 shift QPSK modulation scheme are used as a modulation scheme will be described.
[0016]
First, the signal point arrangement of the MSK modulation method and the π / 4 shift QPSK modulation method will be described.
FIG. 1 shows the reception level of the in-phase component (I) and the reception level of the quadrature component (Q) of the received signal on a quadrature coordinate axis, and four “x” represent signal arrangement points of MSK modulation. Eight “○” represent signal arrangement points of π / 4 shift QPSK modulation. The in-phase component (I) and the quadrature component (Q) are each assigned a level in three stages “+1, 0, −1”, and the three-stage levels are converted into 2-bit data “01, 00, 10”. As a result, the in-phase component (I) becomes 2 bits of “a1, a3” and the quadrature component (Q) becomes 2 bits of “a2, a4”. Finally, as shown in FIG. The signal point represents one modulation symbol with 4 bits “a3, a4”.
[0017]
(First Embodiment)
FIG. 3 is a block diagram showing a configuration of the demodulation device. A receiving antenna 21 for receiving a radio wave, a receiving unit 22 for amplifying a received signal received by the antenna 21 and performing frequency conversion as necessary, and a receiving unit 22 , A synchronous detector (I) 24 for detecting an in-phase component (I) using a reference carrier from the received signal branched by the branching unit 23, A synchronous detector (Q) 25 for detecting a quadrature component (Q) using a reference carrier from the received signal that has been branched, and a clock synchronization / reference carrier recovery unit for synchronizing a clock from the received signal and reproducing the reference carrier 26 are provided. The reference carrier from the clock synchronization / reference carrier recovery unit 26 is directly supplied to the synchronous detector (I) 24 and supplied to the synchronous detector (Q) 25 with a phase shift of π / 2.
[0018]
The clock synchronization and reference carrier recovery unit 26 detects the amplitude level at the time when the modulation symbol is represented by the clock synchronized from the received signal, and shifts the clock by an integral multiple or shifts the phase so that the modulation symbol can be interpolated. The amplitude level detecting section 27 as an amplitude detecting means for detecting an amplitude level at an arbitrary timing, and outputs the three-stage level signals "+1, 0, -1" synchronously detected by the synchronous detector (I) 24 to 2 A ternary-to-binary conversion unit (I) 28 that converts the data into bit data “01,00,10”, and a three-level level signal “+ 1,0, −” synchronously detected by the synchronous detector (Q) 25. A ternary / binary conversion unit (Q) 29 for converting “1” into 2-bit data “01, 00, 10” is provided.
[0019]
Further, the 2-bit data from each of the ternary-to-binary conversion units 28 and 29 are combined into 4 bits, and the amplitude level at an arbitrary timing between the modulation symbols of the reception signal detected by the amplitude level detection unit 27 is obtained. The information and amplitude level information at the time of representing the modulation symbol stored in the memory 30 are compared to determine the modulation method, and the data is demodulated according to the determined modulation method from the combined 4-bit data. A receiving buffer 31 having both a judging means for outputting and a data demodulating means, and a control section 32 for controlling the clock synchronization / reference carrier recovery section 26, amplitude level detecting section 27, memory 30, and receiving buffer 31 are provided.
[0020]
As shown in FIG. 4, the amplitude level detecting section 27 extracts the envelope from the received signal output from the branching section 23, and detects the level of the envelope from the signal passing through the band filter 271. The envelope detector 272 fetches a synchronization clock output from the clock synchronization / reference carrier recovery unit 26 according to a control signal from the control unit 32, and represents an amplitude level and a modulation symbol at an arbitrary timing between modulation symbols. A sample clock generator 273 for generating a sample clock for detecting an amplitude level at a certain point in time, and an amplitude level is sampled at the timing of the sample clock from the sample clock generator 273, and an amplitude level signal is supplied to the reception buffer 31. It is constituted by a level determiner 274 that performs the operation.
[0021]
Next, the operation of the demodulation device will be described.
The envelope characteristic of the received signal from the receiving antenna 21 differs depending on whether it is MSK modulation or π / 4 shift QPSK modulation. FIG. 5 shows the characteristics of the envelope of MSK modulation, and FIG. 6 shows the characteristics of the envelope of π / 4 shift QPSK modulation.
[0022]
In the case of the MSK modulation, even if the signal point representing the modulation symbol is phase-shifted from point A to point B to point C as shown in FIG. 5A, the envelope level remains as shown in FIG. As shown in FIG. On the other hand, in the case of π / 4 shift QPSK modulation, when the signal point representing the modulation symbol is phase-shifted from point X to point Y to point Z as shown in FIG. 6A, the envelope level becomes As shown in FIG. 6B, during the shift from the point X to the point Y and from the point Y to the point Z, the envelope level once decreases and returns to the original level.
[0023]
Therefore, for example, the amplitude level detection unit 27 represents a modulation symbol at the double interval of the clock synchronized by the clock synchronization / reference carrier recovery unit 26 (points A, B, C or X, The amplitude levels at the Y and Z points) and the amplitude levels at the intermediate points (AB and BC points or XY and YZ points) between the modulation symbols are alternately detected, the two detection results are compared, and the detected level changes. If not, MSK modulation can be determined, and if there is a change in level, it can be determined to be π / 4 shift QPSK modulation.
[0024]
Therefore, the reception buffer 31 indicates the amplitude level information at the intermediate point between the modulation symbols detected by the amplitude level detection unit 27 and the modulation symbol detected immediately before and stored in the memory 30. The amplitude level information at the time is compared, and if there is a change larger than a certain threshold, it is determined to be π / 4 shift QPSK modulation, and if there is no change larger than the threshold, it is determined to be MSK modulation, and demodulation is performed in accordance with the modulation method. And output demodulated data.
[0025]
FIG. 7 is a flowchart showing a series of processes in the demodulator. That is, in S1, the amplitude level detecting section 27 detects the amplitude level of the received signal received by the receiving antenna 21 at twice the interval of the reproduced clock synchronized by the clock synchronization / reference carrier reproducing section 26. Subsequently, in S2, the reception buffer 31 sets the amplitude level at the intermediate point between the detected modulation symbols and the amplitude level at the time when the immediately preceding detected modulation symbol represents the modulation symbol stored in the memory 30 in advance. Compare with Then, in S3, it is checked whether or not there is a change in the amplitude level equal to or greater than a certain threshold. If there is a change in excess of the threshold, it is determined in S4 that π / 4 shift QPSK modulation is performed. If there is no change, it is determined in S5 that the modulation is the MSK modulation.
[0026]
Subsequently, in S6, reception is performed from the data of the in-phase component (I) and the quadrature component (Q) input via the receiving unit 22, the respective synchronous detectors 24 and 25, and the respective ternary / binary converting units 28 and 29. The buffer 31 detects a signal point representing the current modulation symbol. Subsequently, in S7, demodulated data corresponding to the signal point detected next from the signal point representing the previous modulation symbol is obtained in advance, and based on the demodulated data table stored in the memory 30, Demodulate the data.
[0027]
Then, in S8, demodulated data corresponding to the signal point detected next from the signal point representing the current modulation symbol is obtained and stored in the memory 30 as a demodulated data table. For example, as shown in FIG. 8A, when the signal point representing the modulation symbol at the current time is “2”, if the next signal point is “0”, the demodulated data is “1”. If the next signal point is “1”, the demodulated data corresponds to “10”, and if the next signal point is “3”, the demodulated data corresponds to the next detected signal point, such as “00”. The demodulated data to be obtained can be obtained, and a demodulated data table as shown in FIG. 8B can be created.
[0028]
Subsequently, in S9, the amplitude level detector 27 detects the amplitude level at the time when the modulation symbol is represented. Then, in S10, the detected amplitude level is stored in the memory 30, and the routine returns to S1.
[0029]
In this way, the demodulation device on the receiving side compares the amplitude level at the time when the modulation symbol is represented from the received signal with the amplitude level at the intermediate point between the detected modulation symbols, and looks at the level change to determine the modulation method. Judgment and data demodulation can be performed according to the judgment. Moreover, one of the two modulation schemes, MSK modulation and π / 4 shift QPSK modulation, is determined, and control for demodulating data based on the determination can be performed by one demodulator, thereby simplifying the configuration. be able to.
[0030]
In this embodiment, the determination means for determining the modulation method is provided in the reception buffer. However, the present invention is not limited to this. The determination means may be provided in the amplitude level detection unit. In this case, a memory for storing the amplitude level information at the time when the modulation symbol is represented is provided in the amplitude level detection unit, or the amplitude level information at the time when the amplitude level detection unit represents the modulation symbol is stored in the memory 30 whenever necessary. May be read.
[0031]
(Second embodiment)
As shown in FIG. 9, this embodiment has basically the same configuration as that of the first embodiment except that the amplitude level detector is omitted, the function of the reception buffer, and the data stored in the memory. It is. The reception buffer 311 determines a modulation method based on a difference in the amount of phase shift between received symbols of MSK modulation and π / 4 shift QPSK modulation.
[0032]
That is, the amount of phase shift of the received signal from the receiving antenna 21 differs depending on whether it is MSK modulation or π / 4 shift QPSK modulation. FIG. 10 shows the phase shift amount of the MSK modulation, and FIG. 11 shows the phase shift amount of the π / 4 shift QPSK modulation. In the MSK modulation, if the phase shift amount is π / 2, the data indicates “0”, and if the phase shift amount is −π / 2, the data indicates “1”. In the π / 4 shift QPSK modulation, if the phase shift amount is π / 4, the data represents “00”. If the phase shift amount is 3π / 4, the data represents “01”. It represents data of “10”, and if −3π / 4, it represents data of “11”.
[0033]
For example, as shown in FIG. 10, when the signal point representing the modulation symbol of the MSK modulation shifts from point A → point B → point C → point B, the amount of phase shift corresponding thereto is π / 2 → π. / 2 → −π / 2, and the demodulated data becomes “001”. Further, as shown in FIG. 11, when a signal point representing a modulation symbol of π / 4 shift QPSK modulation shifts from X point → Y point → Z point → W point, the amount of phase shift corresponding thereto is 3π. / 4 → π / 4 → −3π / 4, and the demodulated data is “010011”.
[0034]
Therefore, in the reception buffer 311, the 2-bit data of the in-phase component (I) from the ternary / binary conversion unit (I) 28 and the quadrature component (Q) from the ternary / binary conversion unit (Q) 29 Are converted into 4 bits by summing up the signal points representing the current modulation symbol from the 4-bit data. The signal point information representing the previous modulation symbol stored in the memory 30 in advance and A comparison operation is performed to determine the amount of phase shift between received symbols. If the amount of shift is ± π / 2, it is determined to be MSK modulation, and if the amount of shift is ± π / 4, ± ππ shift QPSK modulation. Then, the received data is demodulated and output in accordance with the determined modulation scheme.
[0035]
Next, the operation of the demodulation device will be described.
The reception signal from the reception antenna 21 is amplified and frequency-converted by the reception unit 22, branched into two by the branch unit 23, and supplied to the synchronous detector (I) 24 and the synchronous detector (Q) 25, respectively. Then, the in-phase component (I) is synchronously detected by the synchronous detector (I) 24, and the quadrature component (Q) is synchronously detected by the synchronous detector (Q) 25.
[0036]
The synchronous detector (I) 24 divides the received signal into three levels of “+1, 0, −1” and supplies it to a ternary / binary converter (I) 28. Further, the synchronous detector (Q) 25 divides the received signal into three levels of “+1, 0, −1” and supplies it to a ternary / binary converter (Q) 29.
[0037]
Then, as shown in FIG. 12, the ternary-to-binary converter (I) 28 converts the three levels inputted from the synchronous detector (I) 24 into 2-bit data “I” of the in-phase component (I). a1, a3 ". That is, if the level of the three stages is +1, it is converted to 2-bit data "01", if it is 0, it is converted to 2-bit data "00", and if it is -1, it is 2-bit data "10". And supplies it to the reception buffer 311. Further, the ternary-to-binary conversion unit (Q) 29 converts the three-stage levels input from the synchronous detector (Q) 25 into 2-bit data “a2, a4” of the quadrature component (Q). . That is, if the level of the three stages is +1, it is converted to 2-bit data "01", if it is 0, it is converted to 2-bit data "00", and if it is -1, it is 2-bit data "10". And supplies it to the reception buffer 311.
[0038]
As shown in FIG. 13, the reception buffer 311 includes a 2-bit in-phase component (I) “a1, a3” from each of the ternary-binary conversion units 28 and 29 and a 2-bit quadrature component (Q) “ a2, a4 "are combined into 4-bit data" a1, a2, a3, a4 ", which is further converted into 3-bit data representing eight signal points. That is, if the 4-bit data is "0010", it is converted to "000 (decimal; 0)"; if it is "0011", it is converted to "001 (decimal; 1)"; It is converted to "010 (decimal; 2)". If it is "1001", it is converted to "011 (decimal; 3)". If it is "1000", it is converted to "100 (decimal; 4)". , “1100” is converted to “101 (decimal; 5)”, “0100” is converted to “110 (decimal; 6)”, and “0110” is converted to “111 (decimal)”. ; 7) ".
[0039]
Then, the reception buffer 311 calculates the phase shift amount between the modulation symbols from the signal point information indicating the current modulation symbol and the signal point information indicating the immediately preceding modulation symbol stored in the memory 30 in advance. Subtraction is performed to obtain the value. As shown in FIG. 14, if the operation result is a decimal number +2 or -6, the phase shift amount is π / 2, and if the operation result is −2 or +6, the phase shift amount is −π. / 2, which is determined to be MSK modulation, and outputs “0” when the phase shift amount is π / 2 as demodulated data, and outputs “1” when the phase shift amount is −π / 2. .
[0040]
Further, as shown in FIG. 15, if the calculation result is a decimal number +1 or -7, the phase shift amount is π / 4, and if the calculation result is +3 or -5, the phase shift amount is 3π / 4, -1 or If it is +7, the phase shift amount is -π / 4, and if it is -3 or +5, the phase shift amount is -3π / 4, and it is determined that the phase shift amount is π / 4 shift QPSK modulation. Is output when the phase shift amount is π / 4, “01” is output when the phase shift amount is 3π / 4, and “10” is output when the phase shift amount is −π / 4. When the amount of phase shift is -3π / 4, “11” is output.
[0041]
FIG. 16 is a flowchart showing a series of processes in the demodulation device. That is, in S11, the reception buffer 311 converts the in-phase component (I) and the quadrature component (Q) input via the receiving unit 22, each of the synchronous detectors 24 and 25, and each of the ternary-to-binary converting units 28 and 29. , A signal point representing the current modulation symbol is detected. Subsequently, in S12, reception buffer 311 compares and subtracts the detected signal point information with the signal point information representing the previous modulation symbol stored in memory 30 in advance.
[0042]
If the subtraction result is ± 2, ± 6, that is, if the phase shift amount is ± π / 2, the MSK modulation is determined in S13, and the demodulation data table storing the relationship shown in FIG. Demodulates the data based on That is, if the subtraction result is +2 or -6 and the phase shift amount is π / 2, the data is demodulated as “0”, and the subtraction result is -2 or +6 and the phase shift amount is −π / 2. If so, the data is demodulated as "1". Then, in S15, the detected current signal point information is stored in the memory 30, and the routine returns to the processing of S11 again.
[0043]
If the subtraction result is ± 1, ± 3, ± 5, ± 7, that is, if the phase shift amount is ± π / 4, ± 3π / 4, it is determined that the π / 4 shift QPSK modulation is performed in S16, At S17, the data is demodulated based on the demodulation data table storing the relationship shown in FIG. That is, if the subtraction result is +1 or -7 and the phase shift amount is π / 4, the data is demodulated as “00”, and if the subtraction result is +3 or -5 and the phase shift amount is 3π / 4. If the subtraction result is -1 or +7 and the phase shift amount is -π / 4, the data is demodulated as "10" and the subtraction result is -3 or +5. If the shift amount is −3π / 4, the data is demodulated as “11”. Then, in S15, the detected current signal point information is stored in the memory 30, and the routine returns to the processing of S11 again.
[0044]
In this way, the demodulation device on the receiving side determines the modulation scheme by determining the amount of phase shift between received symbols of the received signal, and can demodulate data according to the determination. Moreover, one of the two modulation schemes, MSK modulation and π / 4 shift QPSK modulation, is determined, and control for demodulating data based on the determination can be performed by one demodulator, thereby simplifying the configuration. be able to.
[0045]
(Third embodiment)
As shown in FIG. 17, this embodiment has basically the same configuration as the above-described first embodiment except for the function of a reception buffer and data stored in a memory. The reception buffer 312 determines whether the amplitude level is the MSK modulation or the π / 4 shift QPSK modulation. When the determination is impossible, the reception buffer 312 determines whether the MSK modulation or the π / 4 shift QPSK is performed based on a difference in the phase shift amount between the received symbols. This is to determine whether modulation is performed.
[0046]
That is, if the received signal from the receiving antenna 21 is MSK modulation, the envelope will always remain constant, and if π / 4 shift QPSK modulation, the envelope will once decrease during the phase shift, and Return to level. If the received signal is MSK modulation, the phase shift amount is π / 2 or -π / 2, and if the received signal is π / 4 shift QPSK modulation, the phase shift amount is π / 4, 3π / 4, -π. / 4 or -3π / 4.
[0047]
Therefore, first, the amplitude level detecting section 27 alternately detects the amplitude level at the time of representing the modulation symbol and the amplitude level at the intermediate point of the modulation symbol. Then, the reception buffer 312 detects the amplitude level information at the intermediate point between the modulation symbols detected by the amplitude level detection unit 27 and the immediately preceding amplitude level information, and displays the modulation symbol stored in the memory 30 at the point in time. The amplitude level information is compared, and as shown in FIG. 18A, when the level change is equal to or more than the π / 4 shift QPSK threshold, it is determined that the π / 4 shift QPSK modulation is performed. As shown in (2), when the level change is equal to or less than the threshold for MSK, it is determined that the modulation is the MSK modulation, and the data is demodulated and output in accordance with the determined modulation scheme.
[0048]
Also, as shown in FIG. 18 (c), the level change falls between the π / 4 shift QPSK threshold value and the MSK threshold value due to noise and deviation of the detection timing in the amplitude level detection unit 27, and so on. If the determination cannot be made, the modulation method is not determined at the amplitude level, but the modulation method is determined from the phase shift amount between the received symbols. That is, two bits (a1, a3) of the in-phase component (I) from the ternary-binary conversion unit (I) 28 and two bits (a2) of the quadrature component (Q) from the ternary-binary conversion unit (Q) 29 , A4), a signal point representing the current modulation symbol is derived from the 4-bit data (a1, a2, a3, a4), and a signal representing the previous modulation symbol stored in the memory 30 in advance. A comparison operation with the point information is performed to determine the amount of phase shift between received symbols. If the amount of shift is ± π / 2, it is determined that MSK modulation is performed, and the amount of shift is ± π / 4, ± 3π / 4. If so, it is determined that the modulation is π / 4 shift QPSK modulation, and the data is demodulated and output in accordance with the determined modulation scheme.
[0049]
FIG. 19 is a flowchart showing a series of processes in this demodulation device. That is, in S21, the amplitude level detecting unit 27 detects the amplitude level of the received signal received by the receiving antenna 21 at twice the interval of the reproduced clock synchronized by the clock synchronization / reference carrier reproducing unit 26. Subsequently, in S22, the reception buffer 312 stores the amplitude level at the intermediate point between the detected modulation symbols and the amplitude level at the time when the immediately preceding detected modulation symbol represents the modulation symbol stored in the memory 30 in advance. Compare with Then, in S23, if the change in the amplitude level is equal to or more than the π / 4 shift QPSK threshold, it is determined in S24 that the modulation is π / 4 shift QPSK modulation. It is determined that the modulation is the MSK modulation, and otherwise, it is determined that the determination is impossible.
[0050]
When the modulation method is determined, subsequently, in S26, the in-phase component (the in-phase component input through the receiving unit 22, the synchronous detectors 24 and 25, and the ternary / binary converting units 28 and 29) is input. The reception buffer 312 detects a signal point representing the current modulation symbol from the data of I) and the quadrature component (Q). Subsequently, in S27, demodulated data corresponding to the next detected signal point is determined in advance from the signal point representing the previous modulation symbol, and based on the demodulated data table stored in the memory 30, Demodulate the data. Then, in S28, demodulated data corresponding to the signal point detected next from the signal point representing the current modulation symbol is obtained, and stored in the memory 30 as a demodulated data table.
[0051]
Subsequently, in S29, the amplitude level detecting section 27 detects the amplitude level at the time when the modulation symbol is represented. Then, in S30, the detected amplitude level is stored in the memory 30, and the routine returns to the process of S21 again.
[0052]
If it is determined that the modulation method cannot be determined based on the amplitude level, in S31, the reception buffer 312 controls the receiving unit 22, the synchronous detectors 24 and 25, and the ternary-binary converting units 28 and 29. A signal point representing the current modulation symbol is detected from the data of the in-phase component (I) and the quadrature component (Q) input via the. Subsequently, in S32, reception buffer 312 compares the detected signal point information with the signal point information previously stored in memory 30 and representing the previous modulation symbol, and subtracts it.
[0053]
If the subtraction result is ± 2, ± 6, that is, if the phase shift amount is ± π / 2, it is determined that the MSK modulation is performed in S33, and the data is demodulated based on the demodulation data table in S34. . That is, if the subtraction result is +2 or -6 and the phase shift amount is π / 2, the data is demodulated as “0”, and the subtraction result is -2 or +6 and the phase shift amount is −π / 2. If so, the data is demodulated as "1". Then, in S35, the detected current signal point information is stored in the memory 30, and the routine returns to the processing of S21 again.
[0054]
If the subtraction result is ± 1, ± 3, ± 5, ± 7, that is, if the phase shift amount is ± π / 4, ± 3π / 4, it is determined in step S36 that π / 4 shift QPSK modulation is performed. At S37, the data is demodulated based on the demodulated data table. That is, if the subtraction result is +1 or -7 and the phase shift amount is π / 4, the data is demodulated as “00”, and if the subtraction result is +3 or -5 and the phase shift amount is 3π / 4. If the subtraction result is -1 or +7 and the phase shift amount is -π / 4, the data is demodulated as "10" and the subtraction result is -3 or +5. If the shift amount is −3π / 4, the data is demodulated as “11”. Then, in S35, the detected current signal point information is stored in the memory 30, and the routine returns to the processing of S21 again.
[0055]
In this way, the demodulation device on the receiving side compares the amplitude level at the time when the modulation symbol is represented from the received signal with the amplitude level at the intermediate point between the detected modulation symbols, and looks at the level change to determine the modulation method. Judgment and data demodulation can be performed according to the judgment. When it is not possible to determine the modulation method based on the level change, the modulation method is determined by calculating the amount of phase shift between received symbols of the received signal, and data can be demodulated according to the determination. Therefore, the modulation method can be determined more reliably.
[0056]
Moreover, one of the two modulation schemes, MSK modulation and π / 4 shift QPSK modulation, is determined, and control for demodulating data based on the determination can be performed by one demodulator, thereby simplifying the configuration. be able to.
[0057]
In each of the above-described embodiments, a case has been described in which one of two modulation schemes of the MSK modulation scheme and the π / 4 shift QPSK modulation scheme is determined and demodulated, but the present invention is not necessarily limited to this. For example, another two modulation schemes having different envelope characteristics such as CPFSK modulation and QPSK modulation, BPSK modulation and π / 4 shift QPSK modulation, CPFSK modulation and MSK modulation, or GMSK modulation and π / 4 shift QPSK modulation In this case, one of two or three or more modulation schemes having different phase shift amounts such as BPSK modulation and the like may be determined and demodulated.
[0058]
Further, in the first and third embodiments described above, the point in time when the amplitude level detection unit represents the modulation symbol at twice the interval of the reproduced clock synchronized by the clock synchronization / reference carrier recovery unit. Although the amplitude level at the intermediate point between the amplitude level and the modulation symbol is detected, the invention is not necessarily limited to this as long as the amplitude level can be detected at an arbitrary timing between the modulation symbols of the received signal.
[0059]
【The invention's effect】
According to the first to third aspects of the present invention, it is possible to determine the modulation method on the receiving side, demodulate data according to the determination, and to simplify the configuration by using one demodulation unit. And a demodulation device capable of performing the above.
Further, according to the third aspect of the present invention, it is possible to provide a demodulation device that can more reliably determine the modulation method.
[0060]
Further, according to the inventions described in claims 4 to 6, the modulation method can be determined on the receiving side, and the data can be demodulated according to the determination. Further, the configuration can be simplified by using one demodulation unit. A demodulation method that can be achieved can be provided.
Further, according to the invention of claim 6, it is possible to provide a demodulation method that can more reliably determine the modulation method.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining signal point constellations of an MSK modulation method and a π / 4 shift QPSK modulation method.
FIG. 2 is a diagram showing a data structure indicating a signal point representing a modulation symbol.
FIG. 3 is a block diagram showing a first embodiment of the present invention.
FIG. 4 is a block diagram showing a configuration of an amplitude level detection unit according to the embodiment;
FIG. 5 is a diagram for explaining characteristics of an envelope of MSK modulation in the embodiment.
FIG. 6 is a view for explaining characteristics of an envelope of π / 4 shift QPSK modulation in the embodiment.
FIG. 7 is a flowchart showing a series of processes of the demodulation device in the embodiment.
FIG. 8 is a view for explaining creation of a demodulation data table in the embodiment.
FIG. 9 is a block diagram showing a second embodiment of the present invention.
FIG. 10 is a diagram for explaining a phase shift amount of MSK modulation in the embodiment.
FIG. 11 is a diagram for explaining a phase shift amount of π / 4 shift QPSK modulation in the embodiment.
FIG. 12 is a diagram for explaining the operation of the ternary-binary conversion unit according to the embodiment;
FIG. 13 is an exemplary view for explaining data conversion of a reception buffer according to the embodiment;
FIG. 14 is an exemplary view for explaining demodulation processing in MSK modulation of the reception buffer in the embodiment.
FIG. 15 is a diagram for explaining demodulation processing in π / 4 shift QPSK modulation of the reception buffer according to the embodiment.
FIG. 16 is a flowchart showing a series of processes of the demodulation device in the embodiment.
FIG. 17 is a block diagram showing a third embodiment of the present invention.
FIG. 18 is a view for explaining determination of a modulation method based on level detection of an envelope of a received signal in the embodiment.
FIG. 19 is a flowchart showing a series of processes of the demodulation device in the embodiment.
FIG. 20 is a diagram showing a conventional data communication system.
FIG. 21 is a block diagram showing a configuration of a conventional receiving apparatus.
[Explanation of symbols]
24, 25… Synchronous detector
26: Clock synchronization / reference carrier recovery unit
27 ... amplitude level detector
28, 29 ... ternary-two-value conversion unit
31 ... Reception buffer

Claims (6)

Amplitude detection means for detecting the amplitude of the received signal at an arbitrary timing between the modulation symbols of the received modulation signal; and comparing the amplitude detection result of the amplitude detection means with the amplitude at the time when the modulation symbol is represented. And a data demodulating means for demodulating data in accordance with the modulation scheme determined by the determining means. The data obtained by converting the in-phase component and the quadrature component detected in a plurality of stages from the received modulated signal into bit data, respectively, and combining the two, among the data represented by continuous numerical values at each signal point representing a modulation symbol, A demodulation data table which converts the data to the corresponding data indicating the current signal point, performs a comparison operation with the data representing the immediately preceding signal point, and indicates the correspondence between the calculation result, the phase shift amount, and the demodulated data. A phase shift amount detecting means for detecting a phase shift amount between the current signal point and the immediately preceding signal point, and a modulation method based on the phase shift amount detected by the phase shift amount detecting means. A demodulation apparatus comprising: a judging means for judging; and a data demodulating means for demodulating the phase shift amount in accordance with the modulation method judged by the judging means. Amplitude detection means for detecting the amplitude of the received signal at an arbitrary timing between the modulation symbols of the received modulation signal; and comparing the amplitude detection result of the amplitude detection means with the amplitude at the time when the modulation symbol is represented. First determining means for determining the phase shift amount, phase shift amount detecting means for detecting a phase shift amount between modulation symbols of a received modulation signal, and modulation based on the phase shift amount detected by the phase shift amount detecting means. A demodulator comprising: a second judging means for judging a system; and a data demodulating means for demodulating data according to the judgment result of each judging means. The amplitude of the received signal is detected at an arbitrary timing between the modulation symbols of the received modulation signal, and the modulation result is determined by comparing the detection result with the amplitude at the time when the modulation symbol is represented. A demodulation method characterized in that data is demodulated in accordance with (1). The data obtained by converting the in-phase component and the quadrature component detected in a plurality of stages from the received modulated signal into bit data, respectively, and combining the two, among the data represented by continuous numerical values at each signal point representing a modulation symbol, A demodulation data table which converts the data to the corresponding data indicating the current signal point, performs a comparison operation with the data representing the immediately preceding signal point, and indicates the correspondence between the calculation result, the phase shift amount, and the demodulated data. Based on this, the amount of phase shift between the current signal point and the immediately preceding signal point is detected, the modulation scheme is determined based on the detected phase shift, and the modulation scheme is determined based on the determined phase shift. A demodulation method characterized by performing demodulation together. The amplitude of the received signal is detected at an arbitrary timing between the modulation symbols of the received modulation signal, the detection result is compared with the amplitude at the time when the modulation symbol is represented, and the modulation method is determined. Then, the phase shift between the modulation symbols of the received modulation signal is detected, the modulation scheme is determined based on the detected phase shift, and when the modulation scheme is determined, the data is determined according to the determination result. A demodulation method characterized by demodulating a signal.

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