JPH09200284A - Phase comparing method and quadrature amplitude modulated signal demodulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly perform phase comparison without excessively narrowing a distance from the border line of an error discrimination area in spite of where a symbol point is positioned. SOLUTION: At the time of carrier wave reproduction when demodulating a received quadrature amplitude modulated signal, points, where the C/N of each signal is made logically best, on an I-Q plane are defined as symbol points 1-16. Then, error discrimination areas 21-36 are respectively set to the symbol points 1-16 one by one, the point of the received quadrature amplitude modulated signal on the I-Q plane is defined as a signal point and a phase error signal is outputting for showing the position of this signal point has prescribed relation with the position of the symbol point inside the error discrimination area to which this signal point belongs. In this case, the border lines of the error discrimination areas 21-36 are deformed so that the distance between these border lines and the symbol points 1-16 can be extended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase comparison method in carrier recovery when demodulating a quadrature amplitude modulation (hereinafter abbreviated as CAM) signal and a demodulating apparatus therefor.

[0002]

2. Description of the Related Art Conventionally, there have been quadrature amplitude modulation signal demodulators of this type (hereinafter abbreviated as digital demodulators) and phase comparison methods using them as shown in FIGS. FIG. 5 is a block diagram showing a configuration of a conventional digital demodulator, and FIG. 6 is an IQ coordinate diagram showing an error judgment area and a phase comparison method used when demodulating a quadrature amplitude modulation signal by the digital demodulator shown in FIG. Is.

First, the configuration of the digital demodulation device will be described with reference to FIG. In FIG. 5, 101 is an AD converter for analog-digital converting a modulated wave indicating a received signal point to output a digital signal, and 102 is an in-phase signal or a component (I component) for the input digital component.
And a quadrature signal or a component (Q component) is decomposed and output, 103 is a roll-off filter for spectrally shaping the input digital I component and Q component to remove harmonic components, and 104 is a smooth A register for shaping the waveform into a rectangular wave, 105 is a numerically controlled oscillator 109
The phase of the digital I component and the Q component from the register 104 is rotated by the control of the phase correction vector (complex number, the same applies below) from
It is a complex multiplier that modifies the components.

Reference numeral 106 denotes an 8-to-2 converter which converts 8-valued data consisting of I and Q components of the input signal point into binary data and outputs it as received signal point data.
Reference numeral 7 denotes an error judgment area containing the modulated wave recorded in the ROM, which is judged from the phase of the modulated wave from the complex multiplier 105 (consisting of I component and Q component of the received signal point) and the phase of the modulated wave. The phase comparator 107 compares the phase of the reproduced carrier (the phase of the symbol point), which should be correct, with the detected phase difference and outputs it as a digital signal (indicated by + or −). The loop filter (LPF, low-pass filter) that smoothes the digital signal indicating the phase difference from and outputs the DC level signal indicating the phase difference, 109 is the phase signal of the modulated wave (signal point) by inputting the level signal of the phase difference. Is a numerically controlled oscillator that outputs a phase correction vector for rotating the phase of the modulated wave to match the phase of the reproduced carrier wave to the complex multiplier 105.

Next, the operation of the conventional digital demodulator will be described with reference to FIG. First, the received modulated wave is converted into a digital signal in the AD converter 101, decomposed into the in-phase signal (I component) and the quadrature signal (Q component) in the detector 102, and output. The in-phase signal and the quadrature signal are respectively fed to the roll-off filter 1
In 03, the spectrum is shaped to remove the harmonic component, and only the value at the timing of the signal point is taken into the register 104. In this way, the smoothed waveform is shaped into a rectangular wave in the register 104, and the complex multiplier 1
05 is output.

The complex multiplier 105 performs phase correction by complex-multiplying the digital signals of the I and Q components with the phase correction vector from the numerically controlled oscillator 109, that is, rotating the position on the IQ coordinate. , And outputs digital I and Q components, respectively. 8-2 converter 10
6 is an 8-value in-phase signal (I
Component) and quadrature signal (Q component) are generally easy to handle 2
Play and output the value data.

On the other hand, the phase comparator 107 is the complex multiplier 1
In the error judgment area including the modulated wave recorded in the ROM, which is judged from the phase of the modulated wave output from 05 (consisting of I component and Q component of the received signal (signal point)) and the phase of the modulated wave. The phase difference of the reproduced carrier wave (the phase of the symbol point) which should be correct is detected and the phase difference is detected and output as a digital signal (indicated by + or −).

The loop filter 108 smoothes the phase error signal (digital signal) indicating the phase difference output from the phase comparator 107, and determines the amount by which the phase of the signal point of the received modulated wave should be rotated or corrected. The DC level signal shown is output. The numerically controlled oscillator 109 outputs a phase correction vector (complex number) having a phase according to the magnitude of the input DC level signal to the complex multiplier 105. As described above, the complex multiplier 105 corrects the phase by multiplying the in-phase signal and the quadrature signal at the signal point of the received modulated wave by the phase correction vector.

Next, referring to FIG. 6, in the phase comparator 107 according to the above conventional example, the phase between the phase of the received modulated wave and the phase of the reproduced carrier wave which should be correct as judged from the phase of the modulated wave. The detection of the phase difference will be described. Here, for simplification of the drawing, only the first quadrant of the IQ coordinate diagram is shown, but also in the other second, third, and fourth quadrants, 90 degrees and 180 degrees centering on the origin O, respectively. Degree 2
Since the characteristic has been rotated by 70 degrees, its display and description will be omitted.

In FIG. 6, O indicates the origin of coordinates and I
Indicates an axis in the in-phase direction (hereinafter referred to as I axis), and Q indicates an axis in the orthogonal direction (hereinafter referred to as Q axis). Also, 111 to 12
Reference numeral 6 is a symbol point that represents a digital value defined by an angle (phase) from the in-phase direction I and a distance (amplitude) from the origin O. Reference numerals 131 to 146 each include one symbol point, and the I axis And the Q axis, two arcs of two concentric circles with the origin O as the center, and an error determination area surrounded by a boundary line formed by a perpendicular bisector of a line segment connecting two adjacent symbol points. The radius of each concentric circle is the average value of the distance from the origin O to each symbol point. In this way, the error determination area surrounded by each boundary line is stored in the ROM in the phase comparator 107.

Further, as shown in FIG. 6, each of the error judgment areas 131 to 146 is divided into two sections by a radial straight line extending from the origin O to each of the symbol points 111 to 126. Each of the areas is given a + or-sign and used to determine whether the received signal point is on the right side or the left side on the coordinates of the symbol point, as described above.

That is, the phase comparator 107 judges the signal point of the received signal from the magnitudes of its I component and Q component, and determines which symbol point (for example, the symbol point 111) within the error judgment area 131. By determining which side of, the phase shift from the symbol point is determined. If the signal point is on the + side in the error determination area 131 of the symbol point 111, the phase comparator 107 outputs the digital signal +, and if it is on the − side, the digital signal − is output.

Conventionally, regarding the error of the amplitude of the received signal point, the variation in the distance from the origin O to each signal point is contained within a narrow range due to the gain control performed by the demodulator. On the other hand, regarding the phase error, as described above, even in the above-described conventional phase comparison method and quadrature amplitude modulation signal demodulation device, an error determination area should be provided as large as possible in the circumferential direction centered on the origin O. Thus, it is possible to perform the phase comparison suitable for the application in which the phase difference is increased.

[0014]

However, in the above-described conventional phase comparison method and quadrature amplitude modulation signal demodulation device, for example, the symbol points 111, 117, 126 and the symbol points 112, 122 are located from the origin O. When there are symbol points with slightly different distances, the distance between the signal point and the circular arc that is the boundary line of the error judgment area becomes extremely short, and the erroneous comparison result due to noise components or linear / non-linear distortion components due to reflection etc. There was a high possibility that you would get

This problem is further increased because the number of symbol points slightly different from the origin O increases as the QAM multi-value number increases (the number of symbol points increases). there were.

The present invention has been made in view of the above problems. Regardless of where the position of the symbol point is, the distance from the boundary line of the error determination area is not excessively narrow, and the phase comparison is performed correctly. It is an object of the present invention to provide a phase comparison method and a quadrature amplitude modulation signal demodulation device capable of performing the above.

[0017]

In order to achieve the above object, a phase comparison method and a quadrature amplitude modulation signal demodulation device according to the present invention are provided in order to achieve the above-mentioned object by IQ in carrier recovery when demodulating a received quadrature amplitude modulation signal. A point on the plane where the carrier-to-noise ratio of each signal is logically the best is set as a symbol point, and one error determination region is set for each symbol point, and the received quadrature amplitude modulation signal on the IQ plane is set. A point is a signal point, and is configured to output a phase error signal indicating that the position of the signal point with respect to the position of the symbol point in the error determination region to which the signal point belongs has a predetermined relationship. The error determination area is defined by a circle whose radius is the average value of the distances from the origin between the two symbol points whose distances from the origin are closest to the symbol points. Serial is obtained so as to be longer than the distance to the symbol point.

According to the present invention, regardless of where the position of the symbol point is, the distance from the boundary line of the error determination area does not become excessively small, and the received signal is linear due to noise components or reflection. A phase comparison method and a quadrature amplitude modulation signal demodulation device that can correctly perform phase comparison even with a non-linear distortion component can be obtained.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The invention "Phase comparison method" according to claim 1 of the present invention is the carrier pair of each signal on the IQ plane in carrier recovery when demodulating a received quadrature amplitude modulation signal. The point at which the noise ratio is logically the best is defined as a symbol point, and the error determination area for each symbol point is set to 1
In the error determination region, the boundary line in the circumferential direction centered on the origin is defined as the radius, and the average value of the distances from the origin between the two symbol points having the closest distances from the origin to the symbol points is defined as the radius. The distance from the circle to the symbol point, and a point on the IQ plane of the received quadrature amplitude modulation signal is taken as a signal point, and the signal with respect to the position of the symbol point in the error determination region to which the signal point belongs It is designed to output a phase error signal indicating that the position of a point has a predetermined relationship, and the phase difference between the received signal point and the symbol point is large, and at the boundary line between the symbol point and the error determination area. Even if the distance to a certain arc is extremely short, the correct symbol point for the received signal point can be obtained.

According to the invention "Phase comparison method" of claim 2 of the present invention, the phase error signal indicating that the predetermined relationship is present is defined as follows:
The position rotated clockwise from the line segment connecting the symbol point and the origin is set to be positive, and the position rotated counterclockwise is set to be negative, so that the correct position of the signal point with respect to the symbol point can be determined. It has the effect of being able to.

In the invention "phase comparison method" according to claim 3 of the present invention, the phase error signal is changed stepwise as the angle from the line segment connecting the symbol point and the origin increases. This has the effect that the correct position of the received signal point can be determined.

In the “phase comparison method” according to the fourth aspect of the present invention, the error determination area is centered on the origin, and the distance from the origin to the symbol point is closest to the two symbol points. Based on a boundary line consisting of a circle whose radius is the average value of the distances and a vertical bisector of a line segment that connects two adjacent symbol points between two circles with the closest radius Further, the boundary line is modified so that the distance between the boundary line and the symbol point becomes large, and the phase difference between the received signal point and the symbol point is large, and the error between the symbol point and the symbol point is large. Even if the distance from the circular arc that is the boundary line of the determination area is extremely short, the correct symbol point for the received signal point can be obtained.

According to a fifth aspect of the present invention, a "quadrature amplitude modulation signal demodulating device" is a complex multiplier for multiplying I and Q components of a received signal by a phase correction vector, and an output of the complex multiplier. A phase comparator that compares the phase of the signal point of the received signal with the phase of the corresponding symbol point by the phase comparison method according to claim 4, and outputs a level corresponding to the comparison result by the phase comparator. A loop filter and a numerically controlled oscillator that outputs a phase correction vector corresponding to the level to the complex multiplier, and is configured to perform carrier recovery through a phase-locked loop composed of each of the components described above. Received signal point even if the phase difference between the signal point and the symbol point is large and the distance between the symbol point and the circular arc that is the boundary line of the error determination area is extremely short. An effect that it is possible to obtain the correct symbol points against.

In the "phase comparison method" according to the sixth aspect of the present invention, the error determination area is centered on the origin, and the distance from the origin to the symbol point is the closest to the two symbol points. Among the circles whose radius is the average value of the distances of the circles, the circle from which the distance from the symbol point is smaller than a predetermined value is excluded, and the adjacent circle between the two circles with the closest radius. A radial line centered on the origin passing through the midpoint of a line segment connecting two matching symbol points is used as a boundary line, and the phase difference between the received signal point and the symbol point is large. In addition, even if the distance between the symbol point and the circular arc that is the boundary line of the error determination area is extremely short, it is possible to easily obtain the correct symbol point for the received signal point by designing easily.

According to a seventh aspect of the present invention, a quadrature amplitude modulation signal demodulating device, a complex multiplier for multiplying I and Q components of a received signal by a phase correction vector, and an output of the complex multiplier. A phase comparator for comparing the phase of the signal point of the received signal with the phase of the corresponding symbol point by the phase comparison method according to claim 6, and outputs a level corresponding to the comparison result by the phase comparator. A loop filter and a numerically controlled oscillator that outputs a phase correction vector corresponding to the level to the complex multiplier, and is configured to perform carrier recovery through a phase-locked loop composed of each of the components described above. Even if the phase difference between the signal point and the symbol point is large and the distance between the symbol point and the circular arc that is the boundary of the error determination area is extremely short, the design can be easily performed. Has the effect of a correct symbol point for the signal points can be easily obtained.

In the "phase comparison method" according to the eighth aspect of the present invention, the phase error signal has an angle of a line segment connecting the signal point and the origin with respect to a line segment connecting the symbol point and the origin. When the value is positive, the first level is set, and when the value is negative, the second level is set to be smaller than the first level, and it is possible to obtain a more accurate phase comparison result.

In the invention "phase comparison method" according to claim 9 of the present invention, the error determination area is centered on the origin, and the distance from the origin to the symbol point is the closest from the origin of the two symbol points. Based on a boundary line consisting of a circle whose radius is the average value of the distances and a vertical bisector of a line segment that connects two adjacent symbol points between two circles with the closest radius Further, the boundary line is modified to increase the distance between the boundary line and the symbol point, and the phase difference between the received signal point and the symbol point is large, and the error between the symbol point and the symbol point is large. Even if the distance to the circular arc that is the boundary line of the determination area is extremely short, it is possible to easily obtain the correct symbol point for the received signal point and obtain a more accurate phase comparison result. Have.

According to a tenth aspect of the present invention, "a quadrature amplitude modulation signal demodulating device" is a complex multiplier for multiplying I and Q components of a received signal by a phase correction vector, and an output of the complex multiplier. A phase comparator that compares the phase of the signal point of the received signal with the phase of the corresponding symbol point by the phase comparison method according to claim 9, and outputs a level corresponding to the comparison result by the phase comparator. A loop filter and a numerically controlled oscillator that outputs a phase correction vector corresponding to the level to the complex multiplier, and is configured to perform carrier recovery through a phase-locked loop composed of each of the components described above. The received signal is received even if the phase difference between the signal point and the symbol point is large and the distance between the symbol point and the circular arc that is the boundary of the error determination area is extremely short. On can be obtained easily correct symbol point for, such an action can be obtained more accurate phase comparison.

According to an eleventh aspect of the present invention, which is the "phase comparison method", the error determination area is centered on the origin, and the distance from the origin to the symbol point is closest to the two symbol points. Among the circles whose radius is the average value of the distances of the circles, the circle from which the distance from the symbol point is smaller than a predetermined value is excluded, and the adjacent circle between the two circles with the closest radius. A radial line centered on the origin passing through the midpoint of a line segment connecting two matching symbol points is used as a boundary line, and the phase difference between the received signal point and the symbol point is large. Moreover, even if the distance between the symbol point and the circular arc that is the boundary line of the error determination area is extremely short, the correct symbol point for the received signal point can be easily obtained with a high degree of accuracy in designing. To obtain the phase comparison result It has the effect of kill.

According to a twelfth aspect of the present invention, "a quadrature amplitude modulation signal demodulating device", a complex multiplier for multiplying I and Q components of a received signal by a phase correction vector, and an output of the complex multiplier A phase comparator that compares the phase of the signal point of the received signal with the phase of the corresponding symbol point by the phase comparison method according to claim 11, and outputs a level corresponding to the comparison result by the phase comparator. A loop filter, and a numerically controlled oscillator that outputs a phase correction vector corresponding to the level to the complex multiplier,
The carrier is reproduced through a phase locked loop consisting of the above-mentioned components, and the phase difference between the received signal point and the symbol point is large, and the symbol point and the arc which is the boundary line between the error determination areas Even if the distance between them is extremely short, it is possible to easily obtain a correct symbol point for the received signal point and to obtain a more accurate phase comparison result, easily in designing.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings and FIGS. 1 to 5. FIG. 5 is a block diagram of a quadrature amplitude modulation signal demodulating device for implementing the phase comparison method according to the embodiment of the present invention. However, since it is apparently the same as the conventional configuration (as will be described later, the phase comparator The characteristics are different), and it was used for both the embodiment of the present invention and the conventional example.

FIG. 1 is an IQ coordinate showing an error judgment area and a phase comparison method in the first embodiment of the present invention used when demodulating a quadrature amplitude modulation signal by the quadrature amplitude modulation signal demodulation device shown in FIG. (Or IQ plane, same below)
FIG. 2 is an IQ coordinate diagram showing an error judgment area and a phase comparison method in the second embodiment of the present invention, and FIG. 3 is an error judgment area and a phase comparison method in the third embodiment of the present invention. FIG. 4 is an IQ coordinate diagram showing the I.Q.
It is a-Q coordinate figure.

First, the configuration of the quadrature amplitude modulation signal demodulation device applied to the embodiment of the present invention will be described with reference to FIG. However, in FIG. 5, the AD converter 101,
Detector 102, roll-off filter 103, register 1
04, the complex multiplier 105, the 8-2 converter 106, the loop filter 108, and the numerically controlled oscillator 109 are the same as those of the above-mentioned conventional ones, and thus detailed description thereof will be omitted. However, the characteristics of the phase comparator 107 are different from those of the conventional one. That is, the characteristic relates to the shape of the boundary line of the error determination area, which will be described in detail in the description of the first to fourth embodiments. The complex multiplier 1
05, the phase comparator 107, and the loop filter 108.
And the numerically controlled oscillator 109 form a phase locked loop.

Next, in addition to FIG. 5, the first embodiment of the present invention will be described with reference to FIG. 1 which is an IQ plane mainly showing the characteristics of the phase comparator 107.
The error determination area and the phase comparison method in the embodiment will be described. In the first embodiment, the phase comparator 107 detects the phase difference between the phase of the received modulated wave and the phase of the reproduced carrier wave which should be correct by judging from the phase of the modulated wave. It is in the form of. Here, for simplification of the drawing, only the first quadrant of the IQ coordinate diagram is shown, but also in the other second, third, and fourth quadrants, 90 degrees and 180 degrees centering on the origin O, respectively. Degree 2
Since the characteristic has been rotated by 70 degrees, its display and description will be omitted.

In FIG. 1, O indicates the origin of coordinates and I
Indicates an axis in the in-phase direction (hereinafter referred to as I axis), and Q indicates an axis in the orthogonal direction (hereinafter referred to as Q axis). Further, 1 to 16 are symbol points that represent digital values defined by the angle (phase) from the in-phase direction I and the distance (amplitude) from the origin O, and 21 to 36 are each one symbol point. Including the I-axis and the Q-axis, one or two curves, and a perpendicular line segment connecting two adjacent symbol points (points on the IQ plane where the carrier-to-noise ratio of a signal is logically best) The error judgment area | region enclosed by the boundary line which consists of a bisector is shown.
Each curve is based on a concentric circle whose center is the origin O and whose radius is the average value of the distances from the origin O to each symbol point, and the distance from each symbol point to the curve does not become shorter than a predetermined value. In particular, it is modified so that the vicinity of the symbol point becomes wide.

That is, in the present embodiment, instead of the concentric circle having the origin O as the center, the concentric circle having the origin O as the center is deformed to use an error determination area in which the vicinity of the symbol point is widened. Here, the predetermined value means the phase comparator 10
7 is a distance that does not cause an erroneous comparison result. In the present embodiment, for example, about 1/4 to 1/5 of the distance between symbol points depends on the signal state.
A longer extent seems desirable.

Further, as shown in FIG. 1, each of the error judgment areas 21 to 36 is divided into two sections by a radial straight line extending from the origin O to each of the symbol points 1 to 16. Each of the areas is given a + or-sign and is used to determine a predetermined relationship with the symbol point, that is, whether the received signal point is on the right side or the left side on the coordinate of the symbol point. . The boundary line and each section of each error determination area formed in this way are the phase comparator 107.
Stored in a ROM (or any other storage means) located at (any other location).

That is, the phase comparator 107 judges which symbol point (for example, symbol point 1) the signal point of the received signal is judged from the magnitudes of its I and Q components.
The phase shift from the symbol point is determined by determining which side of the error determination area 21 there is. If the received signal point is on the + side in the error judgment area 21 of the symbol point 1, the phase comparator 107 outputs the digital signal +, and if it is on the-side, the digital signal −.
(Also referred to as a digital signal − and + phase error signal, the same applies hereinafter) is output. Then, as described above, the loop filter 108, the numerically controlled oscillator 109, and the complex multiplier 10
It operates so that the value of the signal point received through 5 etc. approaches the value of the symbol point 1 (the position of the symbol point 1 in coordinates).

As described above, in this embodiment, the origin O
The error judgment area should be set as large as possible in the circumferential direction of the concentric circles centered on the center of the circle. Since the shape of the determination area is modified, the error in the amplitude of the received signal point is contained within a narrow range of the distance from the origin O to each signal point due to gain control performed by the demodulator. However, since the phase difference between the received signal points is large and the distance between the symbol point and the circular arc that is the boundary of the error judgment area is extremely short, noise components or linear / non-linear distortion components due to reflection, etc. If you have to demodulate the received signal in a situation where there is a high probability that
It can be effectively used for applications where it is desired to remove it.

According to the present embodiment, the phase comparator 107 performs the operation of the boundary line of the error judgment area thus formed, each area and the judgment of the comparison using the area (anywhere else. It may be stored in a ROM (or other storage means) and easily embodied.

Next, referring to FIG. 2 of the IQ plane showing mainly the characteristics of the phase comparator 107 in addition to FIG. 5, the second embodiment of the present invention will be described.
The error determination area and the phase comparison method in the embodiment will be described. The second embodiment is the second phase comparison method in which the phase comparator 107 detects the phase difference between the phase of the received modulated wave and the phase of the reproduced carrier wave which should be correct by judging from the phase of the modulated wave. It is in the form of. Here, for simplification of the drawing, only the first quadrant of the IQ coordinate diagram is shown, but also in the other second, third, and fourth quadrants, 90 degrees and 180 degrees centering on the origin O, respectively. Degree 2
Since the characteristic has been rotated by 70 degrees, its display and description will be omitted.

In FIG. 2, O indicates the origin of coordinates, and I
Indicates an axis in the in-phase direction, and Q indicates an axis in the orthogonal direction. Further, 1 to 16 are symbol points that represent digital values defined by the angle (phase) from the in-phase direction I and the distance (amplitude) from the origin O, and 41 to 56 are each one symbol point. Including the I and Q axes and one or two curves,
An error determination area surrounded by a boundary line formed by a perpendicular bisector of a line segment connecting two adjacent symbol points is shown. Each curve is based on a concentric circle whose center is the origin O and whose radius is the average value of the distances from the origin O to each symbol point, and the distance from each symbol point to the curve does not become shorter than a predetermined value. In particular, it is modified so that the vicinity of the symbol point becomes wide.

That is, in the present embodiment, instead of the concentric circle having the origin O as the center, the concentric circle having the origin O as the center is deformed to use an error determination region in which the vicinity of the symbol point is widened. Here, the predetermined value means the phase comparator 10
7 is a distance that does not cause an erroneous comparison result. In the present embodiment, for example, about 1/4 to 1/5 of the distance between symbol points depends on the signal state.
A longer extent seems desirable. Further, as shown in FIG. 2, each of the error determination areas 41 to 56 is divided into two areas by a radial straight line extending from the origin O to each of the symbol points 1 to 16, and each of the areas is +.
Or, a sign of-is used to determine whether the received signal point is on the right side or the left side on the coordinates of the symbol point, as described above.

In addition, the error determination area in this embodiment is a straight line extending from the origin O to each of the symbol points 1 to 16 in a radial direction and rotated by a certain angle from the straight line (dotted line in FIG. 2). +) Respectively
The area and the − area are further divided into two areas, and as shown in FIG. 2, are divided into four areas of +, ++, −−, and −. The angle rotated from the straight line extending from the origin O in the radial direction by a constant angle is about ± 3 degrees in the present embodiment, but it may be any number of times. In addition, the boundary line and each section of each error determination area formed in this manner are the phase comparator 10
7 stored in a ROM (or any other storage location) ROM (or other storage means).

That is, the phase comparator 107 determines which symbol point (for example, symbol point 1) the signal point of the received signal is judged from the magnitudes of its I and Q components.
The phase shift from the symbol point is determined by determining which area in the error determination area 21 of. Now, if the received signal point is in the + or ++ area in the error determination area 21 of the symbol point 1, the phase comparator 10
7 outputs a digital signal + or ++, and-or-
-If it is in the zone, it outputs a digital signal -or-.

Then, the loop filter 108, to which the digital signal −, −−, ++ or + is input from the phase comparator 107, has a level (in the present embodiment, according to the input digital signal −, −−, ++, +). As for the height of the level, for example, positive is the first level, negative is the second level, and the respective levels have a relationship of − <−− <0 <++ <+). Numerically controlled oscillator 109
Output to As described above, this DC signal is passed through the numerically controlled oscillator 109, the complex multiplier 105, etc., and the value of the received signal point is converted into the value of the symbol point 1 (the symbol point 1 in the coordinates).
Position).

As described above, in the present embodiment, as in the first embodiment, the error determination area is provided as large as possible in the circumferential direction of the concentric circle centered on the origin O, and each symbol point Since the shape of the error determination area is modified so that the distance between the symbol determination point and the boundary line of the error determination area, in particular the arc or curve, is large, the phase difference between the received signal points is large and the error determination area is different from the symbol point. Since the distance between the circular arc, which is the boundary line of the area, is extremely short, the situation in which there is a high possibility that an incorrect comparison result will be obtained due to noise components or linear / non-linear distortion components due to reflection, etc. It can be effectively used for applications where it is desired to demodulate a signal.

In addition, in the present embodiment, the level (depending on the area −, −−, ++, +) corresponding to the magnitude of the phase difference is used for the purpose where the phase difference between the received signal point and the symbol point is large. Since the output can be obtained, it is possible to more efficiently demodulate the received signal.

Further, in the present embodiment, the angle of rotating a fixed angle from the straight line passing from the origin O to each symbol point,
That is, the range of angles for determining the phase difference between the symbol point and the signal point and outputting the same determination level is set to about ± 3 degrees, but it may be any number of times depending on the application, and the loop filter 108 The area of the error judgment area for changing the output level is divided into four areas (area −, −−, ++, +), but it is divided into other areas to obtain a more accurate phase comparison result. You can

According to the present embodiment, the boundary line of the error judgment area formed in this way, each area and the operations such as judgment of comparison using the same are performed by the phase comparator 107 as in the first embodiment. It can be easily embodied by storing it in a ROM (which may be placed elsewhere) (or another storage means). It should be noted that the first embodiment has an advantage in terms of hardware configuration that the number of output bits of the ROM may be one less than that of the present embodiment.

Next, referring to FIG. 3 of the IQ plane showing mainly the characteristics of the phase comparator 107 in addition to FIG. 5, the third embodiment of the present invention will be described.
The error determination area and the phase comparison method in the embodiment will be described. In the third embodiment, the phase comparator 107 detects the phase difference between the phase of the received modulated wave and the phase of the reproduced carrier wave which should be correct by judging from the phase of the modulated wave. It is in the form of. Here, for simplification of the drawing, only the first quadrant of the IQ coordinate diagram is shown, but also in the other second, third, and fourth quadrants, 90 degrees and 180 degrees centering on the origin O, respectively. Degree 2
Since the characteristic has been rotated by 70 degrees, its display and description will be omitted.

In FIG. 3, O indicates the origin of the coordinates, and I
Indicates an axis in the in-phase direction, and Q indicates an axis in the orthogonal direction. In addition, 1 to 16 are symbol points that represent digital values defined by an angle (phase) from the in-phase direction I and a distance (amplitude) from the origin O, and 61 to 76 are each one symbol point. Including the I-axis and the Q-axis, two arcs of two concentric circles centered on the origin O, and a line segment extending in the radial direction between the two arcs between two adjacent symbol points from the origin O,
The error judgment area | region enclosed by the boundary line consisting of is shown.

However, for each concentric circle, the distance from each symbol point to the concentric circle serving as the boundary line is the center of the origin O and the radius of the average value of the distances from the origin O to each symbol point. It excludes concentric circles that are shorter than a predetermined value. Therefore, when the concentric circles are removed, the symbol points located there include those having different distances from the origin O, and the boundary line that divides the error determination region of the two symbol points is the two symbol points from the origin O. It is composed of a component connecting two concentric circles on a radial line passing through the midpoint of the connecting line segment (hereinafter referred to as a radial boundary line).

That is, in the present embodiment, of the concentric circles having the origin O as the center, the error judgment is performed except for the concentric circles whose distances from the respective symbol points to the concentric circles which are the boundary lines are shorter than a predetermined value. Use a wide area. Here, the predetermined value means a distance that may cause an erroneous comparison result in the phase comparator 107, and in the present embodiment, for example, between the symbol points depending on the state of the received signal. About 1/4 to 1/5 of the distance
It is shorter.

Further, as shown in FIG. 3, each of the error judgment areas 61 to 76 is divided into two sections by a radial straight line extending from the origin O to each of the symbol points 1 to 16. Each of the areas is given a + or-sign and used to determine whether the received signal point is on the right side or the left side on the coordinates of the symbol point, as described above. The boundary line and each area of each error determination area formed in this way are stored in the ROM (or other storage means) in the phase comparator 107 (which may be placed elsewhere).

That is, the phase comparator 107 determines which symbol point (for example, symbol point 1) the signal point of the received signal is judged from the magnitudes of its I and Q components.
The phase shift from the symbol point is determined by determining which side the error determination area 61 is located. If the received signal point is on the + side in the error judgment area 61 of the symbol point 1, the phase comparator 107 outputs the digital signal +, and if it is on the-side, the digital signal − is output.

The loop filter 108, to which the digital signal − or + is input from the phase comparator 107, has a level corresponding to the input digital signal − or + (in the present embodiment, the level height is − <+ The DC signal of the relationship (1) is output to the numerically controlled oscillator 109. As described above, this DC signal passes through the numerically controlled oscillator 109, the complex multiplier 105, etc., and operates so that the value of the received signal point approaches the value of the symbol point 1 (the position of the symbol point 1 in coordinates).

As described above, in the present embodiment, concentric circles of short arcs are formed so that the distance between the arcs forming the boundary line of the error determination area of each symbol point and the symbol points is sufficiently long. Since it was removed, the phase difference of the received signal point is large, but the distance between the symbol point and the circular arc which is the boundary line of the error judgment area is extremely short, so noise components or linear / non-linear distortion components due to reflection etc. It can be effectively used for the purpose of desiring to demodulate the received signal by eliminating the situation that there is a high possibility that an erroneous comparison result is obtained. Further, since the boundary line of the error determination area in the present embodiment is formed only by straight lines and arcs,
It has a hardware advantage that the ROM can be easily designed.

According to the present embodiment, the phase comparator 107 performs the operation of the boundary line of the error judgment area thus formed, each area and the judgment of the comparison using the area (anywhere else. It may be stored in a ROM (or other storage means) and easily embodied. It should be noted that the first and second embodiments can demodulate a received signal having a longer error determination region in the circumferential direction and a larger phase difference than the present embodiment.

Next, in addition to FIG. 5, referring to FIG. 4 which is an IQ plane mainly showing the characteristics of the phase comparator 107, the fourth embodiment of the present invention will be described.
The error determination area and the phase comparison method in the embodiment will be described. The fourth embodiment is the fourth phase comparison method in which the phase comparator 107 detects the phase difference between the phase of the received modulated wave and the phase of the reproduced carrier wave that should be correct based on the phase of the modulated wave. It is in the form of. Here, for simplification of the drawing, only the first quadrant of the IQ coordinate diagram is shown, but also in the other second, third, and fourth quadrants, 90 degrees and 180 degrees centering on the origin O, respectively. Degree 2
Since the characteristic has been rotated by 70 degrees, its display and description will be omitted.

In FIG. 4, O indicates the origin of coordinates and I
Indicates an axis in the in-phase direction, and Q indicates an axis in the orthogonal direction. Further, 1 to 16 are symbol points that represent digital values defined by the angle (phase) from the in-phase direction I and the distance (amplitude) from the origin O, and 81 to 96 are each one symbol point. Including the I-axis and the Q-axis, two arcs of two concentric circles centered on the origin O, and a line segment extending in the radial direction between the two arcs between two adjacent symbol points from the origin O,
The error judgment area | region enclosed by the boundary line consisting of is shown.

However, for each concentric circle, the distance from each symbol point to the concentric circle that becomes the boundary line is the center of the origin O and the radius of the average value of the distance from the origin O to each symbol point. It excludes concentric circles that are shorter than a predetermined value. Therefore, when the concentric circles are removed, the symbol points located there include those having different distances from the origin O, and the boundary line that divides the error determination region of the two symbol points is the two symbol points from the origin O. It is composed of a component connecting two concentric circles on a radial line passing through the midpoint of the connecting line segment (hereinafter referred to as a radial boundary line).

That is, in the present embodiment, the error determination is performed except for the concentric circles whose center points are the origin O and the distances from the respective symbol points to the concentric circles that are the boundary lines are shorter than a predetermined value. Use a wide area. Here, the predetermined value means a distance that may cause an erroneous comparison result in the phase comparator 107, and in the present embodiment, for example, between the symbol points depending on the state of the received signal. About 1/4 to 1/5 of the distance
It is shorter.

Further, as shown in FIG. 4, each of the error judgment areas 81 to 96 is divided into two sections by a radial straight line extending from the origin O to each of the symbol points 1 to 16. Each of the areas is given a + or-sign and used to determine whether the received signal point is on the right side or the left side on the coordinates of the symbol point, as described above.

In addition, the error determination area in this embodiment is a straight line which is rotated by a certain angle from the straight line extending in the radial direction from the origin O to each of the symbol points 1 to 16 (dotted line in FIG. 4). +) Respectively
The area and the − area are further divided into two areas, and as shown in FIG. 4, are divided into four areas of +, ++, −−, −. The angle rotated from the straight line extending from the origin O in the radial direction by a constant angle is about ± 3 degrees in the present embodiment, but it may be any number of times. In addition, the boundary line and each section of each error determination area formed in this manner are the phase comparator 10
7 stored in a ROM (or any other storage location) ROM (or other storage means).

That is, the phase comparator 107 determines which symbol point (for example, symbol point 1) the signal point of the received signal is judged from the magnitudes of its I and Q components.
The phase shift from the symbol point is determined by determining which area in the error determination area 81 of. If the received signal point is in the + or ++ area in the error judgment area 81 of the symbol point 1, the phase comparator 10
7 outputs a digital signal + or ++, and-or-
-If it is in the zone, it outputs a digital signal -or-.

Then, the loop filter 108, to which the digital signal −, −−, ++ or + is input from the phase comparator 107, has a level (in the present embodiment, according to the input digital signal −, −−, ++, +). The height of the level outputs a DC signal of − <−− <0 <++++> to the numerically controlled oscillator 109. This DC signal is
As described above, the numerically controlled oscillator 109 and the complex multiplier 1
05, the value of the received signal point is made to approach the value of the symbol point 1 (the position of the symbol point 1 in coordinates).

Further, in the present embodiment, the angle rotated from the origin O by a constant angle from the straight line passing through each symbol point,
That is, the range of angles for determining the phase difference between the symbol point and the signal point and outputting the same determination level is set to about ± 3 degrees, but it may be any number of times depending on the application, and the loop filter 108 The area of the error judgment area for changing the output level is divided into four areas (area −, −−, ++, +), but it is divided into other areas to obtain a more accurate phase comparison result. You can

As described above, in the present embodiment, concentric circles having short arcs are formed so that the distance between the arcs forming the boundary line of the error determination area of each symbol point and the symbol points is sufficiently long. Since it was removed, the phase difference of the received signal point is large, but the distance between the symbol point and the circular arc which is the boundary line of the error judgment area is extremely short, so noise components or linear / non-linear distortion components due to reflection etc. It can be effectively used for the purpose of desiring to demodulate the received signal by eliminating the situation that there is a high possibility that an erroneous comparison result is obtained.

In addition, in the present embodiment, the level (depending on the area −, −−, ++, +) corresponding to the magnitude of the phase difference is used for the purpose where the phase difference between the received signal point and the symbol point is large. Since the output can be obtained, it is possible to more efficiently demodulate the received signal. Since the boundary line of the error determination area in this embodiment is formed only by a straight line and a circular arc, there is a hardware advantage that the ROM can be easily designed.

According to the present embodiment, the operation of the boundary line of the error judgment area thus formed, each area and the judgment of the comparison using the same is in the phase comparator 107 as in the other embodiments. It can be easily embodied by storing it in a ROM (which may be placed anywhere else) (or other storage means).

However, in the first and second embodiments, the error determination region in the circumferential direction is longer, and the received signal having a larger phase difference than that in the present embodiment can be demodulated. Further, the third embodiment has an advantage in terms of hardware configuration that the number of output bits of the ROM may be one less than that of the present embodiment.

[0073]

As apparent from the above description, the phase comparison method and the quadrature amplitude modulation signal demodulation device according to the present invention are as follows.
Use a curve instead of the arc that forms the boundary of the error judgment area of the symbol point, or if the distance from the symbol point to the arc is shorter than a certain length, remove it to secure a sufficiently large error judgment area. By doing so,
Regardless of the position of the symbol point, the distance from the boundary line of the error judgment area does not become excessively small, and even if the received signal has noise components or linear / non-linear distortion components due to reflection, etc. Phase comparison can be performed, and the loop gain of the carrier recovery loop can be increased.
Further, by subdividing the error determination region, more efficient signal point comparison processing can be performed.

[Brief description of drawings]

1 is an IQ coordinate diagram showing an error determination area and a phase comparison method in the first embodiment of the present invention used when demodulating a quadrature amplitude modulation signal by the quadrature amplitude modulation signal demodulation device shown in FIG. 5;

FIG. 2 is an IQ coordinate diagram showing an error determination region and a phase comparison method according to the second embodiment of the present invention, similar to FIG.

FIG. 3 is an IQ coordinate diagram showing an error determination region and a phase comparison method according to the third embodiment of the present invention, similar to FIG.

FIG. 4 is an IQ coordinate diagram showing an error determination region and a phase comparison method according to the fourth embodiment of the present invention, similar to FIG.

FIG. 5 is a block diagram showing a configuration of a quadrature amplitude modulation signal demodulation device according to an embodiment of the present invention and a conventional example.

6 is an IQ coordinate diagram showing a conventional error determination area and phase comparison method used when demodulating a quadrature amplitude modulation signal by the quadrature amplitude modulation signal demodulation device shown in FIG.

[Explanation of symbols]

 1 to 16 symbol points 21 to 36 error determination area 41 to 56 error determination area 61 to 76 error determination area 81 to 96 error determination area 101 AD converter 102 detector 103 roll-off filter 104 register 105 complex multiplier 106 8-2 Converter 107 Phase comparator 108 Loop filter 109 Numerically controlled oscillator 111-126 Symbol point 131-146 Error determination area

Claims (12)

[Claims] 1. In carrier recovery when demodulating a received quadrature amplitude modulation signal, a point at which the carrier-to-noise ratio of each signal is logically best on the IQ plane is set as a symbol point, and for each symbol point One error determination area is set for each of the error determination areas, and the boundary line in the circumferential direction centered on the origin is closest to the symbol point from the origin.
A point on the IQ plane of the received quadrature amplitude modulation signal is set as a signal point, which is longer than the distance from the circle whose radius is the average value of the distance between the two symbol points from the origin. A phase comparison method comprising the steps of outputting a phase error signal indicating that the position of the signal point with respect to the position of the symbol point in the error determination region to which the point belongs has a predetermined relationship. 2. The phase error signal indicating that the predetermined relationship is present is positive or counterclockwise in a position rotated clockwise from a line segment connecting the symbol point and the origin within an error determination area to which the symbol point belongs. 2. The phase comparison method according to claim 1, wherein the position rotated in the direction is made negative. 3. The phase comparison method according to claim 2, wherein the phase error signal is changed stepwise as the angle from a line segment connecting the symbol point and the origin increases. 4. A circle whose center is the origin of the error determination area and whose radius is an average value of distances of the two symbol points closest to the origin from the origin.
Based on a boundary line consisting of a perpendicular bisector of a line segment that connects two adjacent symbol points between two circles having the closest radius, the boundary line is further modified to change the boundary line. The distance between the line and the symbol point is increased, and the distance between the line and the symbol point is increased.
The phase comparison method described in 2 or 3. 5. A complex multiplier for multiplying I and Q components of a received signal by a phase correction vector, and a phase of a signal point of the received signal and a phase of a symbol point corresponding to the output of the complex multiplier. 5. A phase comparator for comparison by the phase comparison method according to claim 4, a loop filter for outputting a level corresponding to a comparison result by the phase comparator, and a phase correction vector corresponding to the level for the complex multiplier. A quadrature amplitude modulation signal demodulation device including a numerically controlled oscillator for outputting a carrier wave and performing carrier wave recovery through a phase locked loop composed of the above-mentioned respective components. 6. The error determination area is a symbol of a circle whose center is the origin and whose radius is an average value of distances from the origin of two symbol points whose distances from the origin are closest. An origin that passes through the midpoint of a line segment that connects a circle excluding a circle in which the distance from the point to the circle is smaller than a predetermined value and two adjacent symbol points between the two circles with the closest radius. 4. The phase comparison method according to claim 3, wherein a line in a radial direction centered on is used as a boundary line. 7. A complex multiplier for multiplying I and Q components of a received signal by a phase correction vector, and a phase of a signal point of a received signal and a phase of a symbol point corresponding to the output of the complex multiplier. 7. A phase comparator for comparison by the phase comparison method according to claim 6, a loop filter for outputting a level corresponding to a comparison result by the phase comparator, and a phase correction vector corresponding to the level for the complex multiplier. A quadrature amplitude modulation signal demodulation device including a numerically controlled oscillator for outputting a carrier wave and performing carrier wave recovery through a phase locked loop composed of the above-mentioned respective components. 8. The phase error signal has a first level when the angle of a line segment connecting the signal point and the origin with respect to a line segment connecting the symbol point and the origin is positive, and the first level when the angle is negative. 3. The phase comparison method according to claim 2, wherein the second level is smaller than the first level. 9. A circle whose center is the origin and whose radius is an average value of distances from the origin of two symbol points having the closest distance from the origin to the symbol point,
Based on a boundary line consisting of a perpendicular bisector of a line segment that connects two adjacent symbol points between two circles having the closest radius, the boundary line is further modified to change the boundary line. 9. The phase comparison method according to claim 8, wherein the distance between the line and the symbol point is increased. 10. A complex multiplier for multiplying I and Q components of a received signal by a phase correction vector, and a phase of a signal point of the received signal and a phase of a corresponding symbol point at the output of the complex multiplier. A phase comparator for comparison by the phase comparison method according to claim 9, a loop filter for outputting a level corresponding to a comparison result by the phase comparator, and a phase correction vector corresponding to the level for the complex multiplier. A quadrature amplitude modulation signal demodulation device including a numerically controlled oscillator for outputting a carrier wave and performing carrier wave recovery through a phase locked loop composed of the above-mentioned respective components. 11. The error determination area is centered on an origin,
Of the circles whose radius is the average value of the distances from the origin of the two symbol points having the closest distances from the origin to the symbol points, except for circles in which the distance from the symbol point to the circle is smaller than a predetermined value Circle and a radial line centered on the origin that passes through the midpoint of the line segment that connects two adjacent symbol points between the two circles with the closest radius. 9. The phase comparison method according to claim 8. 12. A complex multiplier for multiplying I and Q components of a received signal by a phase correction vector, and a phase of a signal point of the received signal and a phase of a symbol point corresponding to the output of the complex multiplier. A phase comparator for comparing by the phase comparing method according to claim 11, and a loop filter for outputting a level corresponding to a comparison result by the phase comparator,
A quadrature amplitude modulation signal demodulation device including a numerical control oscillator that outputs a phase correction vector corresponding to the level to the complex multiplier, and performs carrier recovery through a phase locked loop composed of the respective components.