JP2021002758A - Demodulator - Google Patents

Abstract

To provide a demodulator capable of reducing demodulation errors owing to phase error even when an excessively large signal is input thereto.SOLUTION: A demodulator 1 comprises: an IQ signal generating unit 10 for performing quadrature demodulation and AD conversion on a modulated wave subjected to phase modulation to generate an IQ signal; a phase-amplitude signal calculating unit 11 for calculating a phase and amplitude of the IQ signal; an amplitude detector unit 12 for comparing the amplitude with a threshold; a correcting unit 13 which outputs the phase when the amplitude is equal to or under the threshold, and which corrects the phase and outputs a phase after the correction when the amplitude is above the threshold; and a demodulation unit 25 for demodulating the IQ signal on the basis of the phase output by the correcting unit 13.SELECTED DRAWING: Figure 1

Description

The present invention relates to a demodulator that demodulates a phase modulated signal.

Conventionally, a delay detection method is known as a method of demodulating a phase-modulated signal. For example, Patent Document 1 discloses a demodulator 20 that demodulates a π / 4 shift QPSK modulated signal, as shown in FIG. In the demodulation device 20, the orthogonal demodulation processing unit 21 converts the modulated wave into a baseband signal of the I signal and the Q signal, the band limiting unit 22 band-limits the IQ signal, and the AD conversion unit 23 converts it into digital data. .. Then, the phase signal calculation unit 24 calculates the phase of the IQ signal, and the demodulation unit 25 performs delayed detection to determine the data and outputs it as a data string.

Japanese Unexamined Patent Publication No. 2001-177587

However, in the conventional demodulation device, when the input is excessive, a phase error may occur due to saturation of the AD converter, and a demodulation error may occur. This problem will be described with reference to FIG. FIG. 15A is a diagram showing an example of IQ signal points when the signal input to the AD converter is below the output range. In this case, assuming that the range surrounded by the square is the output range of the AD converter, the signal point A of the IQ signal is located inside the square. Assuming that the coordinates of the point A are (x, y), the phase θ of the IQ signal is calculated by θ = tan ^-1 (y / x).

FIG. 15B is a diagram showing an example of IQ signal points when the signal input to the AD converter exceeds the output range. In this case, assuming that the range surrounded by the square is the output range of the AD converter, the signal point A of the IQ signal input to the AD converter is located outside the square. However, since the AD converter is saturated, the signal point of the IQ signal output from the AD converter is clipped to the point B. Assuming that the coordinates of the point B are (x', y), the phase φ of the IQ signal is calculated by φ = tan ^-1 (y / x'), so that a phase error occurs with respect to the originally desired phase θ. It ends up.

An object of the present invention made in view of such circumstances is to provide a demodulation device capable of reducing a demodulation error due to a phase error when an excessive signal (a signal exceeding the output range of an AD converter) is input. To do.

In order to solve the above problems, the demodulation apparatus according to the present invention calculates an IQ signal generator that generates an IQ signal by orthogonal demodulating and AD converting a phase-modulated modulated wave, and the phase and amplitude of the IQ signal. A phase / amplitude signal calculation unit, an amplitude detection unit that compares the amplitude with a threshold, and an output of the phase when the amplitude is equal to or less than the threshold, and the phase when the amplitude exceeds the threshold. A correction unit that corrects and outputs the corrected phase, and a demodulation unit that demodulates the IQ signal based on the phase output by the correction unit are provided.

Further, in the demodulator according to the present invention, the correction unit is a phase determination unit that determines the position of a signal point of the IQ signal on the IQ plane based on the phase of the IQ signal, and the amplitude determines the threshold value. If it exceeds, a phase output selection unit is provided which outputs a phase obtained by adding or subtracting a fixed phase correction amount to the phase as the corrected phase according to the determination result of the phase determination unit.

Further, in the demodulator according to the present invention, the correction unit includes a phase determination unit that determines in which region of the IQ plane the IQ signal is located, and the IQ signal according to the determination result of the phase determination unit. The amplitude correction unit that corrects the amplitude of the above, the phase signal calculation unit that calculates the phase of the IQ signal after the amplitude correction by the amplitude correction unit, and the phase signal calculation unit if the amplitude exceeds the threshold value. It includes a phase output selection unit that outputs the corrected phase as the corrected phase.

Further, in the demodulator according to the present invention, the correction unit refers to a phase correction table in which the phase and the phase correction amount are associated with each other, and the phase correction unit that corrects the phase of the IQ signal and the amplitude are the same. When it exceeds the threshold value, it includes a phase output selection unit that outputs the phase corrected by the phase correction unit as the corrected phase.

Further, in the demodulation device according to the present invention, the correction unit includes a function calculation unit that corrects the phase of the IQ signal by using a phase correction function, and the function calculation unit when the amplitude exceeds the threshold value. A phase output selection unit that outputs the phase corrected by the above as the corrected phase is provided.

Further, in the demodulation device according to the present invention, when the amplitude exceeds the threshold value, the phase output selection unit uses the corrected phase in consideration of the difference between the amplitude and the threshold value as the corrected phase. Output.

According to the present invention, it is possible to reduce a demodulation error due to a phase error when an excessive signal is input.

It is a block diagram which shows the structural example of the demodulation apparatus which concerns on 1st Embodiment. It is a block diagram which shows the structural example of the amplitude detection part and the correction part in the demodulation apparatus which concerns on 1st Embodiment. It is a figure for demonstrating the correction method of the demodulation apparatus which concerns on 1st Embodiment. It is a block diagram which shows the structural example of the amplitude detection part and the correction part in the demodulation apparatus which concerns on 2nd Embodiment. It is a figure for demonstrating the correction method of the demodulation apparatus which concerns on 2nd Embodiment. It is a block diagram which shows the structural example of the amplitude detection part and the correction part in the demodulation apparatus which concerns on 3rd Embodiment. It is a figure which shows an example of the phase correction table in the demodulation apparatus which concerns on 3rd Embodiment. It is a figure for demonstrating the correction method of the demodulation apparatus which concerns on 3rd Embodiment. It is a block diagram which shows the structural example of the amplitude detection part and the correction part in the demodulation apparatus which concerns on 4th Embodiment. It is a figure for demonstrating the correction method of the demodulation apparatus which concerns on 4th Embodiment. It is a block diagram which shows the structural example of the amplitude detection part and the correction part in the demodulation apparatus which concerns on 5th Embodiment. It is a block diagram which shows the structural example of the amplitude detection part and the correction part in the modification of the demodulation apparatus which concerns on 5th Embodiment. It is a figure for demonstrating the correction method of the modification of the demodulation apparatus which concerns on 5th Embodiment. It is a block diagram which shows the structural example of the conventional demodulation apparatus. It is a figure for demonstrating the problem of the conventional demodulation apparatus. It is a figure for demonstrating the problem of the conventional demodulation apparatus.

Embodiments of the present invention will be described in detail with reference to the drawings. In the embodiment shown below, a demodulation device that demodulates the π / 4 shift QPSK modulation signal will be described, but the demodulation is not limited to the demodulation of QPSK. For example, the data determination method is different only for the demodulation of FSK, and the present invention can be applied in the same manner.

FIG. 1 is a block diagram showing a configuration example of the demodulation device 1 according to the embodiment of the present invention. The demodulation device 1 inputs a phase-modulated modulated wave and demodulates the modulated wave to generate a data string. The demodulation device 1 shown in FIG. 1 includes an IQ signal generation unit 10, a phase / amplitude signal calculation unit 11, an amplitude detection unit 12, a correction unit 13, and a demodulation unit 25.

The IQ signal generation unit 10 generates an IQ signal by performing orthogonal demodulation and AD conversion of the phase-modulated modulated wave, and outputs the IQ signal to the phase / amplitude signal calculation unit 11. The IQ signal generation unit 10 includes an orthogonal demodulation processing unit 21, a band limiting unit 22, and an AD conversion unit 23.

The orthogonal demodulation processing unit 21 converts the phase-modulated modulated wave into a baseband signal of the I signal and the Q signal, and outputs the I signal and the Q signal to the band limiting unit 22, respectively.

The band limiting unit 22 band limits the baseband signal of the IQ signal and outputs it to the AD conversion unit 23. More specifically, the band limiting unit 22 includes a low-pass filter 221 and a low-pass filter 222. The low-pass filter 221 band-limits the baseband signal of the I signal, and the low-pass filter 222 band-limits the baseband signal of the Q signal.

The AD conversion unit 23 converts the analog IQ signal (baseband signal) input from the band limiting unit 22 into a digital IQ signal and outputs it to the phase / amplitude signal calculation unit 11. More specifically, the AD conversion unit 23 includes an AD converter 231 and an AD converter 232. The AD converter 231 converts the I signal input from the low-pass filter 221 from an analog signal to a digital signal, and the AD converter 232 converts the Q signal input from the low-pass filter 222 from an analog signal to a digital signal.

The phase / amplitude signal calculation unit 11 calculates the phase and amplitude of the IQ signal generated by the IQ signal generation unit 10, outputs the calculated phase to the correction unit 13-1, and outputs the calculated amplitude to the amplitude detection unit 12. Output.

The amplitude detection unit 12 compares the amplitude calculated by the phase / amplitude signal calculation unit 11 with a predetermined threshold value, and outputs a correction enable signal indicating whether or not the amplitude exceeds the threshold value to the correction unit 13. In all embodiments, the correction enable signal shall indicate "1" when the amplitude exceeds the threshold and "0" when the amplitude is below the threshold.

When the correction enable signal input from the amplitude detection unit 12 is “0” (that is, when the amplitude calculated by the phase / amplitude signal calculation unit 11 is equal to or less than the threshold value), the correction unit 13 determines the phase. The phase calculated by the amplitude signal calculation unit 11 is output to the demodulation unit 25 as it is. Further, the correction unit 13 has a phase when the correction enable signal input from the amplitude detection unit 12 is “1” (that is, when the amplitude calculated by the phase / amplitude signal calculation unit 11 exceeds the threshold value). -The phase calculated by the amplitude signal calculation unit 11 is corrected, and the corrected phase is output to the demodulation unit 25. The details of the correction unit 13 will be described later.

The demodulation unit 25 demodulates the IQ signal based on the phase output by the correction unit 13. The demodulation unit 25 shown in FIG. 1 includes a delay detection unit 251, a data determination unit 252, and a parallel serial conversion unit 253.

The delay detection unit 251 acquires the phase of the IQ signal from the correction unit 13 and calculates the phase difference from the IQ signal one symbol ahead. Then, the delay detection unit 251 decodes the data based on the phase difference and outputs the data to the data determination unit 252. In the embodiment, since the signal input to the demodulation device 1 is a π / 4 shift QPSK modulated signal, the delay detection unit 251 outputs 2-bit data (X, Y) for each IQ signal.

The data determination unit 252 determines the data (X, Y) input from the delay detection unit 251 based on the synchronous clock signal, and outputs the data (X, Y) to the parallel serial conversion unit 253.

The parallel serial conversion unit 253 converts the parallel data (X, Y) input from the data determination unit 252 into serial data, and outputs the data string to the outside of the demodulation device 1.

(First Embodiment)
Next, each embodiment will be described. Since the configurations other than the amplitude detection unit 12 and the correction unit 13 are common to each embodiment, the amplitude detection unit 12 and the correction unit 13 will be described in detail below. In this embodiment, the amplitude detection unit 12 and the correction unit 13 are referred to as an amplitude detection unit 12-1 and a correction unit 13-1 in order to distinguish them from other embodiments.

FIG. 2 is a block diagram showing a configuration example of the amplitude detection unit 12-1 and the correction unit 13-1 according to the first embodiment.

The amplitude detection unit 12-1 shown in FIG. 2 includes a comparator 121. The comparator 121 compares the amplitude calculated by the phase / amplitude signal calculation unit 11 with a predetermined threshold value, and outputs a correction enable signal indicating whether or not the amplitude exceeds the threshold value to the correction unit 13-1. To do.

The correction unit 13-1 shown in FIG. 2 includes a phase determination unit 131, a phase correction unit 132, and a phase output selection unit 133.

The phase determination unit 131 determines the position of the signal point (IQ signal point) of the IQ signal on the IQ plane based on the phase calculated by the phase / amplitude signal calculation unit 11, and determines the phase of the determination signal indicating the determination result. Output to the output selection unit 133.

The phase correction unit 132 adds and subtracts a predetermined phase correction amount to the phase calculated by the phase / amplitude signal calculation unit 11, and outputs the corrected phase to the phase output selection unit 133. In the present embodiment, the phase correction amount is set to a predetermined fixed value.

The phase output selection unit 133 acquires the phase θ of the IQ signal before correction from the phase / amplitude signal calculation unit 11, and acquires the phase θ'of the IQ signal after correction from the phase correction unit 132. Then, when the correction enable signal input from the comparator 121 is “0”, the phase output selection unit 133 selects the phase θ calculated by the phase / amplitude signal calculation unit 11 and causes the demodulation unit 25 to select the phase θ. When the output is output and the correction enable signal is "1", the phase θ'corrected by the phase correction unit 132 is selected and output to the demodulation unit 25 according to the determination result of the phase determination unit 131. That is, when the amplitude of the IQ signal generated by the IQ signal generation unit 10 is equal to or less than the threshold value, the phase output selection unit 133 outputs the phase θ calculated by the phase / amplitude signal calculation unit 11 and outputs the IQ signal. When the amplitude of the IQ signal generated by the generation unit 10 exceeds the threshold value, the phase θ'in which a predetermined phase correction amount is added or subtracted from the phase θ is output according to the determination result of the phase determination unit 131. To do.

FIG. 3 is a diagram for explaining a correction method of the demodulation device 1 according to the first embodiment. The range surrounded by the square indicates the output range of the AD conversion unit 23, and the circle inside the output range indicates the threshold value of the amplitude detection unit 12-1 and is surrounded by the circle outside the output range. The range indicates the range of the baseband signal input to the AD conversion unit 23. As shown in FIG. 3, when the signal point of the IQ signal input to the AD conversion unit 23 is located at the point A on the IQ plane, the I signal is out of the output range of the AD conversion unit 23, so that the AD conversion unit 23 The signal point of the IQ signal output from 23 is clipped to point B.

の領域に位置すると判定された場合には、位相θから位相補正量Δθを減算した位相θ’を選択し、復調部２５に出力する。また、位相出力選択部１３３は、比較器１２１から入力された補正イネーブル信号が“１”のときに、位相判定部１３１によりＩＱ信号点がＩＱ平面上で

の領域に位置すると判定された場合には、位相θに位相補正量Δθを加算した位相θ’を選択し、復調部２５に出力する。 In the phase output selection unit 133, when the correction enable signal input from the comparator 121 is “1”, the IQ signal point is set on the IQ plane by the phase determination unit 131.

If it is determined that the position is located in the region of, the phase θ'by subtracting the phase correction amount Δθ from the phase θ is selected and output to the demodulation unit 25. Further, in the phase output selection unit 133, when the correction enable signal input from the comparator 121 is “1”, the IQ signal point is set on the IQ plane by the phase determination unit 131.

If it is determined that the position is located in the region of, the phase θ', which is the sum of the phase θ and the phase correction amount Δθ, is selected and output to the demodulation unit 25.

In the example shown in FIG. 3, the phase output selection unit 133 outputs the phase θ', which is obtained by subtracting the phase correction amount Δθ from the phase θ, to the demodulation unit 25. By this correction, the error between the phase of the point A originally desired to be calculated and the phase of the point B can be reduced.

As described above, the correction unit 13-1 according to the present embodiment includes the phase determination unit 131 that determines in which region of the IQ plane the IQ signal is located, and when the amplitude of the IQ signal exceeds the threshold value. It is provided with a phase output selection unit 133 that outputs a phase obtained by adding or subtracting a fixed phase correction amount with respect to the phase of the IQ signal according to the determination result. Therefore, according to the present embodiment, a demodulation error when an excessive signal is input can be reduced by a simple configuration in which only a fixed value is added or subtracted with respect to the phase of the IQ signal.

(Second Embodiment)
Next, the demodulation device 1 according to the second embodiment of the present invention will be described. In the present embodiment, the amplitude detection unit 12 and the correction unit 13 are referred to as an amplitude detection unit 12-2 and a correction unit 13-2 in order to distinguish them from other embodiments. In the present embodiment, the AD conversion unit 23 shown in FIG. 1 outputs the IQ signal to the phase / amplitude signal calculation unit 11 and also outputs the IQ signal to the correction unit 13-2.

FIG. 4 is a block diagram showing a configuration example of the amplitude detection unit 12-2 and the correction unit 13-2 in the second embodiment.

The correction unit 13-2 shown in FIG. 4 includes a phase determination unit 131, an amplitude correction unit 134, a phase signal calculation unit 135, and a phase output selection unit 133. Since the phase determination unit 131 and the amplitude detection unit 12-2 are the same as those in the first embodiment, the description thereof will be omitted.

The amplitude correction unit 134 corrects the amplitude of the IQ signal converted by the AD conversion unit 23 according to the determination result of the phase determination unit 131, and outputs the corrected IQ signal amplitude to the phase signal calculation unit 135. More specifically, the amplitude correction unit 134 includes an I signal amplitude correction unit 1341 and a Q signal amplitude correction unit 1342.

The I signal amplitude correction unit 1341 corrects the amplitude of the input I signal according to the determination result of the phase determination unit 131. The Q signal amplitude correction unit 1342 corrects the amplitude of the input Q signal according to the determination result of the phase determination unit 131.

The phase signal calculation unit 135 calculates the phase θ'of the IQ signal after the amplitude correction by the amplitude correction unit 134, and outputs the phase θ'to the phase output selection unit 133.

The phase output selection unit 133 acquires the phase θ of the IQ signal before correction from the phase / amplitude signal calculation unit 11, and acquires the phase θ'of the IQ signal after correction from the phase signal calculation unit 135. Then, when the correction enable signal input from the comparator 121 is “0”, the phase output selection unit 133 selects the phase θ and outputs the phase θ to the demodulation unit 25, and the correction enable signal is “1”. In some cases, the phase θ'is selected and output to the demodulation unit 25. That is, when the amplitude of the IQ signal generated by the IQ signal generation unit 10 is equal to or less than the threshold value, the phase output selection unit 133 outputs the phase θ calculated by the phase / amplitude signal calculation unit 11 and outputs the IQ signal. When the amplitude of the IQ signal generated by the generation unit 10 exceeds the threshold value, the phase θ'calculated by the phase signal calculation unit 135 is output.

FIG. 5 is a diagram for explaining a correction method of the demodulation device 1 according to the second embodiment. The range surrounded by the square indicates the output range of the AD conversion unit 23, and the circle inside the output range indicates the threshold value of the amplitude detection unit 12-2, and is surrounded by the circle outside the output range. The range indicates the range of the baseband signal input to the AD conversion unit 23.

の領域に位置すると判定された場合には、Ｉ信号が＋側に飽和しているとして、Ｉ座標に一定値ΔＩを加算する。このとき、補正後のＩＱ座標は（Ｉ＋ΔＩ，Ｑ）となる。また、Ｉ信号振幅補正部１３４１は、位相判定部１３１によりＩＱ信号点がＩＱ平面上で

の領域に位置すると判定された場合には、Ｉ信号が−側に飽和しているとして、Ｉ座標から一定値ΔＩを減算する。このとき、補正後のＩＱ座標は（Ｉ−ΔＩ，Ｑ）となる。 In the I signal amplitude correction unit 1341, the IQ signal point is set on the IQ plane by the phase determination unit 131.

If it is determined that the signal is located in the region of, it is assumed that the I signal is saturated on the + side, and a constant value ΔI is added to the I coordinate. At this time, the corrected IQ coordinates are (I + ΔI, Q). Further, in the IQ signal amplitude correction unit 1341, the IQ signal point is set on the IQ plane by the phase determination unit 131.

If it is determined that the signal is located in the region of, it is assumed that the I signal is saturated on the − side, and a constant value ΔI is subtracted from the I coordinate. At this time, the corrected IQ coordinates are (I−ΔI, Q).

の領域に位置すると判定された場合には、Ｑ信号が＋側に飽和しているとして、Ｑ座標に一定値ΔＱを加算する。このとき、補正後のＩＱ座標は（Ｉ，Ｑ＋ΔＱ）となる。
また、Ｑ信号振幅補正部１３４２は、位相判定部１３１によりＩＱ信号がＩＱ平面上で

の領域に位置すると判定された場合には、Ｑ信号が−側に飽和しているとして、Ｑ座標から一定値ΔＱを減算する。このとき、補正後のＩＱ座標は（Ｉ，Ｑ−ΔＱ）となる。 In the Q signal amplitude correction unit 1342, the IQ signal is transmitted by the phase determination unit 131 on the point IQ plane.

If it is determined that the signal is located in the region of, it is assumed that the Q signal is saturated on the + side, and a constant value ΔQ is added to the Q coordinate. At this time, the corrected IQ coordinates are (I, Q + ΔQ).
Further, in the Q signal amplitude correction unit 1342, the IQ signal is transmitted on the IQ plane by the phase determination unit 131.

If it is determined that the signal is located in the region of, it is assumed that the Q signal is saturated on the − side, and a constant value ΔQ is subtracted from the Q coordinate. At this time, the corrected IQ coordinates are (I, Q−ΔQ).

In the example shown in FIG. 5, the signal point A of the IQ signal output from the AD conversion unit 23 is located outside the threshold value of the amplitude detection unit 12-2. Therefore, the I signal amplitude correction unit 1341 adds a constant value ΔI to the I coordinate assuming that the I signal is saturated on the + side. As a result, the signal point is corrected to point B. Next, the phase signal calculation unit 135 calculates the phase θ'of the signal point B. The phase output selection unit 133 selects the phase θ'and outputs the phase to the demodulation unit 25.

As described above, the correction unit 13-2 according to the present embodiment has the phase determination unit 131 for determining in which region of the IQ plane the IQ signal is located, and the IQ signal according to the determination result of the phase determination unit 131. The amplitude correction unit 134 that corrects the amplitude of the above, the phase signal calculation unit 135 that calculates the phase of the IQ signal after the amplitude correction by the amplitude correction unit 134, and the phase signal calculation unit 135 that calculates the phase when the amplitude exceeds the threshold value. It is provided with a phase output selection unit 133 that outputs the generated phase. Therefore, according to the present embodiment, by correcting the amplitude of the saturated region, it is possible to reduce the demodulation error when an excessive signal is input.

(Third Embodiment)
Next, the demodulation device 1 according to the third embodiment of the present invention will be described. In this embodiment, the amplitude detection unit 12 and the correction unit 13 are referred to as an amplitude detection unit 12-3 and a correction unit 13-3 in order to distinguish them from other embodiments.

FIG. 6 is a block diagram showing a configuration example of the amplitude detection unit 12-3 and the correction unit 13-3 in the third embodiment. Since the amplitude detection unit 12-3 is the same as that of the first embodiment, the description thereof will be omitted.

The correction unit 13-3 shown in FIG. 6 includes a phase correction unit 136 and a phase output selection unit 133. The phase correction unit 136 has a phase correction table 1361.

The phase correction table 1361 is a table in which the phase and the phase correction amount are associated with each other, and is a table for determining the phase correction amount according to the phase input from the phase / amplitude signal calculation unit 11. FIG. 7 is a diagram showing an example of the phase correction table 1361. The phase correction unit 136 refers to the phase correction table 1361 and determines the phase correction amount Δθ corresponding to the phase θ calculated by the phase / amplitude signal calculation unit 11. Then, the phase correction unit 136 adds the determined phase correction amount Δθ to the phase θ, and outputs the corrected phase θ'to the phase output selection unit 133.

The phase output selection unit 133 acquires the phase θ of the IQ signal before correction from the phase / amplitude signal calculation unit 11, and acquires the phase θ'of the IQ signal after correction from the phase correction unit 136. Then, when the correction enable signal input from the comparator 121 is “0”, the phase output selection unit 133 selects the phase θ calculated by the phase / amplitude signal calculation unit 11 and causes the demodulation unit 25 to select the phase θ. When the output is output and the correction enable signal is “1”, the phase θ ′ corrected by the phase correction unit 136 is selected and output to the demodulation unit 25. That is, when the amplitude of the IQ signal generated by the IQ signal generation unit 10 is equal to or less than the threshold value, the phase output selection unit 133 outputs the phase θ calculated by the phase / amplitude signal calculation unit 11 and outputs the IQ signal. When the amplitude of the IQ signal generated by the generation unit 10 exceeds the threshold value, the corrected phase θ'is output with reference to the phase correction table 1361.

FIG. 8 is a diagram for explaining a correction method of the demodulation device 1 according to the third embodiment. The range surrounded by the square indicates the output range of the AD conversion unit 23, and the circle inside the output range indicates the threshold value of the amplitude detection unit 12-3.

In the example shown in FIG. 8, the signal point A of the IQ signal output from the AD conversion unit 23 is located outside the threshold value of the amplitude detection unit 12-3. Therefore, the phase correction unit 136 refers to the phase correction table 1361 and acquires the phase correction amount Δθ corresponding to the phase θ of the signal point A. Then, the phase correction unit 136 calculates the phase θ'by adding the phase correction amount Δθ to the phase θ. The phase output selection unit 133 selects the phase θ'and outputs the phase to the demodulation unit 25.

As described above, the correction unit 13-3 according to the present embodiment refers to the phase correction table 1361 in which the phase and the phase correction amount are associated with each other, and the phase correction unit 136 for correcting the phase of the IQ signal and the amplitude. When the value exceeds the threshold value, a phase output selection unit 133 that outputs the phase corrected by the phase correction unit 136 is provided. Therefore, according to the present embodiment, the phase correction amount can be changed by the phase correction table 1361 with respect to the input phase, so that a demodulation error when an excessive signal is input can be detected in the first embodiment and the first embodiment. It can be further reduced as compared with the second embodiment.

(Fourth Embodiment)
Next, the demodulation device 1 according to the fourth embodiment of the present invention will be described. In this embodiment, the amplitude detection unit 12 and the correction unit 13 are referred to as an amplitude detection unit 12-4 and a correction unit 13-4 in order to distinguish them from other embodiments.

FIG. 9 is a block diagram showing a configuration example of the amplitude detection unit 12-4 and the correction unit 13-4 according to the fourth embodiment. Since the amplitude detection unit 12-4 is the same as that of the first embodiment, the description thereof will be omitted.

The correction unit 13-4 shown in FIG. 9 includes a function calculation unit 137 and a phase output selection unit 133.

The function calculation unit 137 performs a function calculation on the phase θ input from the phase / amplitude signal calculation unit 11 by using the phase correction function to correct the phase. Then, the function calculation unit 137 outputs the corrected phase θ'to the phase output selection unit 133. The phase correction function is a function that calculates the phase θ'by performing a predetermined operation with the phase θ as an argument.

The phase output selection unit 133 acquires the phase θ of the IQ signal before correction from the phase / amplitude signal calculation unit 11, and acquires the phase θ'of the IQ signal after correction from the function calculation unit 137. Then, when the correction enable signal input from the comparator 121 is “0”, the phase output selection unit 133 selects the phase θ calculated by the phase / amplitude signal calculation unit 11 and causes the demodulation unit 25 to select the phase θ. When the output is output and the correction enable signal is “1”, the phase θ ′ corrected by the function calculation unit 137 is selected and output to the demodulation unit 25. That is, when the amplitude of the IQ signal generated by the IQ signal generation unit 10 is equal to or less than the threshold value, the phase output selection unit 133 outputs the phase θ calculated by the phase / amplitude signal calculation unit 11 and outputs the IQ signal. When the amplitude of the IQ signal generated by the generation unit 10 exceeds the threshold value, the phase θ'corrected by the function calculation unit 137 is output.

FIG. 10 is an IQ plan view for explaining a correction method of the demodulation device 1 according to the fourth embodiment. The range surrounded by the square indicates the output range of the AD conversion unit 23, and the circle inside the output range indicates the threshold value of the amplitude detection unit 12-4, and is surrounded by the circle outside the output range. The range indicates the range of the baseband signal input to the AD conversion unit 23. As shown in FIG. 10, when the signal point of the IQ signal input to the AD conversion unit 23 is located at the point A on the IQ plane, the I signal is out of the output range of the AD conversion unit 23, so that the AD conversion unit 23 The signal point of the IQ signal output from 23 is clipped to point B.

In the example shown in FIG. 10, the signal point B of the IQ signal output from the AD conversion unit 23 is located outside the threshold value of the amplitude detection unit 12-3. Therefore, the phase output selection unit 133 selects the phase θ'corrected by the function calculation unit 137 and outputs it to the demodulation unit 25. As an example, the maximum output of the AD conversion unit 23 is 1, the maximum output of the baseband signal is 1.5, and the phase correction function F (θ) is set to the following equation (1).

For example, when the phase of the point A is 30 degrees, when the phase calculation is performed at the clipped point B, the phase θ becomes 36.8 degrees, and a phase error of 6.8 degrees occurs. Here, when the calculation is performed by the phase correction function F (θ) of the equation (1), the phase θ'is F (30) = 28.1 degrees, and the phase error is as small as 1.9 degrees.

As described above, the correction unit 13-4 according to the present embodiment is a function calculation unit 137 that corrects the phase of the IQ signal by using the phase correction function F (θ), and when the amplitude exceeds the threshold value, It includes a phase output selection unit 133 that outputs the phase corrected by the function calculation unit 137. Therefore, according to the present embodiment, the phase correction amount can be made variable by the phase correction function F (θ) with respect to the input phase, so that a demodulation error when an excessive signal is input can be prevented. It can be further reduced as compared with the first embodiment and the second embodiment. Further, as compared with the third embodiment, since it is not necessary to provide a table in this embodiment, the configuration can be simplified.

(Fifth Embodiment)
Next, the demodulation device 1 according to the fifth embodiment of the present invention will be described. In the present embodiment, the amplitude detection unit 12 and the correction unit 13 are referred to as an amplitude detection unit 12-5 and a correction unit 13-5 in order to distinguish them from other embodiments.

FIG. 11 is a block diagram showing a configuration example of the amplitude detection unit 12-5 and the correction unit 13-5 according to the fifth embodiment.

The comparator 121 included in the amplitude detection unit 12-5 compares the amplitude calculated by the phase / amplitude signal calculation unit 11 with a predetermined threshold value, and corrects the difference information indicating the difference between the amplitude and the threshold value. Output to 5. The difference information may be the difference value itself between the amplitude and the threshold value, or may be information indicating a guideline for the difference between the amplitude and the threshold value.

Further, the comparator 121 outputs a correction enable signal indicating whether or not the amplitude calculated by the phase / amplitude signal calculation unit 11 exceeds the threshold value to the correction unit 13-5.

FIG. 11 shows an example in which the amplitude detection unit 12-5 is applied to the correction unit 13-1 of the first embodiment. The amplitude detection unit 12-5 is similarly applied to the correction unit 13-2 of the second embodiment, the correction unit 13-3 of the third embodiment, and the correction unit 13-4 of the fourth embodiment. It is possible.

The correction unit 13-5 shown in FIG. 11 includes a phase determination unit 131, a phase correction unit 132, a phase correction amount selection unit 138, and a phase output selection unit 133. It is the same as the first embodiment except for the phase correction amount selection unit 138.

The phase correction amount selection unit 138 stores a plurality of phase correction amounts in advance. Then, the phase correction amount selection unit 138 selects the phase correction amount based on the difference information input from the comparator 121, and outputs the selected phase correction amount to the phase correction unit 132.

The phase correction unit 132 adds and subtracts the phase correction amount selected by the phase correction amount selection unit 138 with respect to the phase calculated by the phase / amplitude signal calculation unit 11, and sets the corrected phase as the phase output selection unit. Output to 133.

The phase output selection unit 133 acquires the phase θ of the IQ signal before correction from the phase / amplitude signal calculation unit 11, and acquires the phase θ'of the IQ signal after correction from the phase correction unit 132. Then, when the correction enable signal input from the comparator 121 is “0”, the phase output selection unit 133 selects the phase θ calculated by the phase / amplitude signal calculation unit 11 and causes the demodulation unit 25 to select the phase θ. When the output is output and the correction enable signal is "1", the phase θ'corrected by the phase correction unit 132 is selected and output to the demodulation unit 25 according to the determination result of the phase determination unit 131.

FIG. 12 is a block diagram showing a modified example of the amplitude detection unit 12-5 and the correction unit 13-5 shown in FIG. As shown in FIG. 12, the amplitude detection unit 12-5 may compare the amplitude calculated by the phase / amplitude signal calculation unit 11 with a plurality of predetermined threshold values. In this case, the comparator 121 outputs to the phase correction amount selection unit 138 information indicating which threshold value the amplitude of the amplitude and the minimum threshold value is within. Further, the comparator 121 outputs a correction enable signal indicating whether or not the amplitude exceeds the minimum threshold value to the correction unit 13-5.

FIG. 13 is a diagram for explaining a correction method of the demodulation device 1 according to the modified example of the fifth embodiment. Here, the comparator 121 compares the amplitude with the first threshold (minimum threshold) and the second threshold. The range surrounded by the square indicates the output range of the AD conversion unit 23, and the solid line circle inside the output range indicates the first threshold value of the amplitude detection unit 12-5, and the solid line circle outside the output range. Indicates the second threshold value of the amplitude detection unit 12-5, and the range surrounded by the outermost dashed circle indicates the range of the baseband signal input to the AD conversion unit 23. As shown in FIG. 13, when the signal point of the IQ signal input to the AD conversion unit 23 is located at the point A on the IQ plane, the I signal is out of the output range of the AD conversion unit 23, so that the AD conversion unit The signal point of the IQ signal output from 23 is clipped to point B. Further, when the signal point of the IQ signal input to the AD conversion unit 23 is located at the point D on the IQ plane, the Q signal is out of the output range of the AD conversion unit 23, so that it is output from the AD conversion unit 23. The signal point of the IQ signal is clipped to point E.

When the amplitude calculated by the phase / amplitude signal calculation unit 11 exceeds the first threshold value, the phase correction unit 132 adds or subtracts the phase correction amount to the phase θ. The phase correction amount selection unit 138 sets the phase correction amount to Δθ when the amplitude> the second threshold value, and sets the phase correction amount to Δφ when the first threshold value <amplitude ≦ the second threshold value.

As shown in FIG. 13, when the signal point of the IQ signal output from the AD conversion unit 23 is the point B, the amplitude exceeds the second threshold value, so that the phase correction amount selection unit 138 uses Δθ as the phase correction amount. Select. The phase correction unit 132 calculates the phase θ'by subtracting Δθ from the phase θ of the point B. The phase output selection unit 133 selects the phase θ'and outputs the phase to the demodulation unit 25.

Further, as shown in FIG. 13, when the signal point of the IQ signal output from the AD conversion unit 23 is the point E, the amplitude exceeds the first threshold value and is equal to or less than the second threshold value, so that the phase correction amount The selection unit 138 selects Δφ as the phase correction amount. The phase correction unit 132 calculates the phase φ'by adding Δφ to the phase θ of the point E. The phase output selection unit 133 selects the phase φ'and outputs the phase to the demodulation unit 25.

As described above, in each of the first to fourth embodiments, when the amplitude exceeds the threshold value (the minimum threshold value when a plurality of threshold values are used), the phase output selection unit 133 determines the difference between the amplitude and the threshold value. The phase corrected by adding may be output. That is, when the amplitude detection unit 12-5 is applied in the first embodiment, the phase correction amount can be set to a different value according to the difference between the amplitude and the threshold value as described above. Similarly, when the amplitude detection unit 12-5 is applied in the second embodiment, the amplitude correction unit 134 sets the correction amount of the amplitude of the IQ signal to a different value according to the difference between the amplitude and the threshold value. Can be done. Further, when the amplitude detection unit 12-5 is applied in the third embodiment, the phase correction table 1361 can be set to a different table according to the difference between the amplitude and the threshold value. Further, when the amplitude detection unit 12-5 is applied in the fourth embodiment, the phase correction function can be a different function depending on the difference between the amplitude and the threshold value. In this way, by applying the amplitude detection unit 12-5 in each embodiment, the demodulation device 1 of each embodiment can further reduce the phase error.

Although the above embodiments have been described as typical examples, it will be apparent to those skilled in the art that many modifications and substitutions can be made within the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited by the above embodiments, and various modifications and modifications can be made without departing from the scope of claims. For example, it is possible to combine a plurality of constituent blocks described in the configuration diagram of the embodiment into one, or to divide one constituent block.

1 Demodulator 10 IQ signal generator 11 Phase / amplitude signal calculation unit 12-1, 12-2, 12-3, 12-4, 12-5 Amplitude detection unit 13-1, 13-2, 13-3, 13 -4, 13-5 Correction unit 21 Orthogonal demodulation processing unit 22 Band limiting unit 23 AD converter 25 Demodulation unit 131 Phase determination unit 132, 136 Phase correction unit 133 Phase output selection unit 137 Function calculation unit 138 Phase correction amount selection unit 221 , 222 Low-pass filter 231,232 AD converter 251 Delay detection unit 252 Data judgment unit 253 Parallel serial conversion unit 1341 I signal amplitude correction unit 1342 Q signal amplitude correction unit 1361 Phase correction table

Claims (6)

An IQ signal generator that generates an IQ signal by performing orthogonal demodulation and AD conversion of a phase-modulated modulated wave,
A phase / amplitude signal calculation unit that calculates the phase and amplitude of the IQ signal,
An amplitude detection unit that compares the amplitude with the threshold value,
When the amplitude is equal to or less than the threshold value, the phase is output, and when the amplitude exceeds the threshold value, the phase is corrected and the corrected phase is output.
A demodulation unit that demodulates the IQ signal based on the phase output by the correction unit, and
A demodulator equipped with. The correction unit
A phase determination unit that determines the position of a signal point of the IQ signal on the IQ plane based on the phase of the IQ signal.
When the amplitude exceeds the threshold value, a phase output selection that outputs a phase obtained by adding or subtracting a fixed phase correction amount to the phase as the corrected phase according to the determination result of the phase determination unit. Department and
The demodulation apparatus according to claim 1. The correction unit
A phase determination unit that determines in which region of the IQ plane the IQ signal is located,
An amplitude correction unit that corrects the amplitude of the IQ signal according to the determination result of the phase determination unit, and
A phase signal calculation unit that calculates the phase of the IQ signal after amplitude correction by the amplitude correction unit, and
When the amplitude exceeds the threshold value, a phase output selection unit that outputs the phase calculated by the phase signal calculation unit as the corrected phase, and
The demodulation apparatus according to claim 1. The correction unit
With reference to the phase correction table in which the phase and the phase correction amount are associated with each other, the phase correction unit for correcting the phase of the IQ signal and the phase correction unit
When the amplitude exceeds the threshold value, a phase output selection unit that outputs the phase corrected by the phase correction unit as the corrected phase, and
The demodulation apparatus according to claim 1. The correction unit
A function calculation unit that corrects the phase of the IQ signal using a phase correction function,
When the amplitude exceeds the threshold value, a phase output selection unit that outputs the phase corrected by the function calculation unit as the corrected phase, and
The demodulation apparatus according to claim 1. Any of claims 2 to 5, wherein when the amplitude exceeds the threshold value, the phase output selection unit outputs the corrected phase in consideration of the difference between the amplitude and the threshold value as the corrected phase. The demodulator according to item 1.

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