JP7224722B2 - carrier recovery circuit - Google Patents

Description

The present invention relates to a carrier recovery circuit for recovering a carrier/received wave in digital wireless transmission.

In recent years, wireless traffic has been increasing more and more, and from the viewpoint of increasing the efficiency of frequency utilization, in digital wireless transmission, there is a growing demand for high-speed transmission using a high multilevel QAM (Quadrature Amplitude Modulation) method. . In this high multi-level QAM system, demodulation performance may be degraded due to phase noise (phase error) of carrier waves occurring in a transmitting device or a receiving device. For this reason, there is known a carrier recovery circuit that improves demodulation performance (bit error rate) based on the degree of influence of phase noise and thermal noise (see, for example, Patent Document 1).

Based on the phase error detected by the phase error detector and the amplitude error detected by the amplitude error detector, the carrier recovery circuit controls the bandwidth of the loop filter by the loop filter control unit to reduce phase noise and heat. An appropriate bandwidth is set according to the noise to improve the demodulation performance.

JP 2011-101177 A

By the way, in high multi-level modulation, the phase error detection range of carrier wave/carrier reproduction becomes extremely narrow. 23, the phase error detection range W1 is wide because the distance between the adjacent reference points S1 is large. Moreover, the phase error detection range W1 is narrowed because the distance between the adjacent reference points S1 is small. Then, since the phase error detection range is significantly narrowed, when the phase jitter (fluctuation of phase) increases in a phase noise environment as shown in FIG.

As a result, it becomes impossible to determine whether the phase is rotating in the advance direction or in the lagging direction, or which signal point S2 is shifted from which reference point S1. Here, the erroneous detection signal shown in hatching in FIG. 25 causes the phase to start rotating clockwise so that the signal point S2 approaches the reference point S1.

However, in the carrier recovery circuit described in Patent Document 1, the specifications of the carrier recovery loop at high multi-level are switched depending on whether priority is given to reduction of thermal noise or reduction of phase noise. Since no consideration is given to unstable operation due to a decrease in the phase error detection range associated with multi-leveling, it has been difficult to achieve stable operation of the demodulator in a low C/N environment.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a carrier recovery circuit capable of achieving stable and high demodulation performance even in high multi-level.

In order to solve the above problems, the invention according to claim 1 provides a phase rotator for rotating the phase of an input signal, and a phase rotation signal that is the input signal whose phase has been rotated by the phase rotator. a phase error detector that detects an error; and a rotation signal generator that generates a phase rotation control signal based on the phase error. A phase-rotating carrier recovery circuit , wherein the phase error detector arranges a plurality of reference points in advance on a complex plane at equal intervals vertically and horizontally, and divides the reference points vertically and horizontally at equal intervals. A rectangular phase error detection range centered on the reference point is set, and for all signal points on the complex plane, the phase in the phase error detection range centered on the reference point corresponding to the signal point A full-point error detector for detecting errors, and a signal point located outside a first radius from the origin on the complex plane, or located within a second radius smaller than the first radius from the origin on the complex plane. a polar error detector for detecting a phase error with respect to at least one signal point of the signal points to be detected; , a rectangular detection area is set with the outer edge of the entire reference point as the outer edge, and in which direction and how much all the signal point groups are shifted from the detection area centering on the origin on the complex plane and an area error detector for detecting the phase error based on the phase of either the full-point error detector or the polar error detector based on the phase error detected by the area error detector. The error is output to the rotation signal generator.

A phase rotator for rotating the phase of an input signal, and a phase error detector for detecting a phase error contained in a phase-rotated signal, which is the input signal whose phase has been rotated by the phase rotator. and a rotation signal generator for generating a phase rotation control signal based on the phase error, wherein the phase rotator is a carrier recovery circuit for rotating the phase of the input signal based on the phase rotation control signal. wherein the phase error detector has a plurality of reference points arranged in advance on a complex plane at equal intervals in the vertical and horizontal directions, and a quadrangle centered on the reference points so as to divide the reference points in the vertical and horizontal directions at equal intervals. and for all signal points on the complex plane, all-point error detection for detecting the phase error in the phase error detection range centered on the reference point corresponding to the signal point A plurality of reference points are arranged in advance on the complex plane at equal intervals vertically and horizontally, and a square detection area is set centered on the origin on the complex plane and having an outer edge of the entire reference points as an outer edge, an area error detection unit that detects the phase error based on how much and in which direction all the signal point groups are deviated from the detection area around the origin on the complex plane, wherein the area error According to the phase error detected by the detection section, either the phase error detected by the all-point error detection section or the area error detection section is output to the rotation signal generation section.

According to the first aspect of the present invention , since the phase error of either the full -point error detector or the polar error detector is output to the rotation signal generator, stable high demodulation performance is realized even at high multi-values. It becomes possible to In other words, since the all-point error detector detects the phase error for all signal points on the complex plane, it can detect the phase error with high accuracy, but with high multi-values, unstable operation occurs due to phase fluctuations. can lead to loss of synchronization of carrier recovery. On the other hand, the polar error detector detects phase errors only for signal points far outside or close to the origin on the complex plane. Since the detectable range (phase error detection range) is wide, unstable operation is unlikely to occur even at high multi-values, and it is possible to prevent or suppress loss of synchronization in carrier reproduction.

Therefore, it is possible to achieve stable and high demodulation performance even at high multi-levels by providing both the full-point error detection section and the polar error detection section and switching the output to the rotation signal generation section. It will be.

According to the first aspect of the present invention , at this time, which phase error is to be output to the rotation signal generation section is selected based on the phase error detected by the area error detection section. It becomes possible to output the phase error to the rotation signal generator.

This is because the area error detector detects the phase error based on how much and in which direction all the signal point groups around the origin on the complex plane deviate from the detection area around the origin on the complex plane. to detect In other words, whether the phase shift is in the leading direction or the lagging direction, and how much the phase shift is, are detected by the shift state of the entire signal point group with respect to the detection area, so unstable operation occurs even at high multi-values. Therefore, it is possible to prevent or suppress loss of synchronization of carrier wave reproduction. Then, based on the phase error detected by such an area error detection unit, either the phase error of the all-point error detection unit or the polar error detection unit is selected. can be output to the rotation signal generator.

According to the second aspect of the invention, based on the phase error detected by the area error detector, the phase error of either the all-point error detector or the area error detector is output to the rotation signal generator. Therefore, it is possible to achieve stable high demodulation performance even at high multi-values. In other words, since the all-point error detector detects the phase error for all signal points on the complex plane, it can detect the phase error with high accuracy, but with high multi-values, unstable operation occurs due to phase fluctuations. can lead to loss of synchronization of carrier recovery. On the other hand, the area error detector detects whether the phase shift is in the leading or lagging direction and how much the phase shift is based on the shift state of the entire signal point cloud with respect to the detection area. Even if there is, unstable operation is unlikely to occur, and it is possible to prevent or suppress loss of synchronization in carrier recovery.

Therefore, it is possible to achieve stable and high demodulation performance even at high multi-values by providing the all-point error detection section and the area error detection section together and switching the output to the rotation signal generation section. It will be.

1 is a schematic configuration block diagram showing a carrier recovery circuit according to Embodiment 1 of the present invention; FIG. 2 is a schematic configuration diagram showing a phase error detector in the carrier recovery circuit of FIG. 1; FIG. 3 is a conceptual diagram showing a detection method of a polar error detector of the phase error detector of FIG. 2; FIG. 3 is a conceptual diagram showing a detection method of a full-point error detection unit of the phase error detector of FIG. 2; FIG. FIG. 9 is a schematic configuration diagram showing a phase error detector of a carrier recovery circuit according to Embodiment 2 of the present invention; 6 is a first conceptual diagram showing a detection method of an area error detection section of the phase error detector of FIG. 5; FIG. FIG. 6 is a second conceptual diagram showing the detection method of the area error detector of the phase error detector of FIG. 5; FIG. 9 is a schematic configuration diagram showing a phase error detector of a carrier recovery circuit according to Embodiment 3 of the present invention; FIG. 11 is a schematic configuration diagram showing a phase error detector of a carrier recovery circuit according to Embodiment 4 of the present invention; FIG. 10 is a diagram showing the positional relationship between the lead region and the lag region in the phase error detector of FIG. 9; 11A and 11B are diagrams showing erroneous detection regions and normal detection regions in the lead region and the lag region of FIG. 10; FIG. 11 is a diagram showing an erroneously detected area and a normal detected area when the lead area and the lag area in FIG. 10 are extended; FIG. 13 is a diagram showing signal points that are not subject to error detection in the lead region and the lag region of FIG. 12; FIG. 10 is a diagram showing a detection state by a frequency detection unit in the phase error detector of FIG. 9; FIG. 10 is a diagram showing a lead region and a lag region when the first cross-shaped area error detector is selected in the phase error detector of FIG. 9; FIG. 10 is a diagram showing a lead region and a lag region when the second cross-shaped area error detector is selected in the phase error detector of FIG. 9; FIG. 9 is a diagram showing a state in which all signal point groups are rotated in the advancing direction in Embodiment 2 of the present invention; FIG. 18 is a diagram showing a state in which all signal point groups have further rotated in the advance direction, following FIG. 17 ; FIG. 10 is a diagram showing a phase error detection area in Embodiment 5 of the present invention; FIG. 10 is a diagram showing the positional relationship between signal points and phase error detection regions when all signal point groups are rotated in the advancing direction in Embodiment 5 of the present invention; FIG. 20 is a diagram showing the positional relationship between the signal points and the phase error detection area when all the signal point groups are further rotated in the advancing direction, following FIG. FIG. 22 is a diagram showing a state in which phase rotation is suppressed from the state of FIG. 21; FIG. 4 is a conceptual diagram showing a phase error detection range for one signal point in the case of low multi-values in the present invention; FIG. 4 is a conceptual diagram showing a phase error detection range for one signal point in the case of high multi-values in the present invention; FIG. 10 is a conceptual diagram showing a state in which phase jitter occurs due to high multi-values in the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on the illustrated embodiments.

(Embodiment 1)
1 to 4 show this embodiment, and FIG. 1 is a schematic configuration block diagram showing a carrier recovery circuit 1 according to this embodiment. This carrier recovery circuit 1 is a circuit for recovering a carrier in digital wireless transmission, and mainly includes a first phase rotator (phase rotator) 2, an adaptive equalizer 3, a phase error detector 4, and an LPF 5. , an NCO (rotation signal generator) 6 , a second phase rotator 7 , and an equalizer 8 .

The first phase rotator 2 is a rotator/multiplier that rotates the phase of the input signal, and rotates the phase of the input signal based on a phase rotation control signal from the NCO 6, which will be described later. Specifically, each of the I-channel baseband signal and the Q-channel baseband signal converted into digital signals is subjected to phase rotation based on the sine wave and cosine wave of the phase rotation control signal of the NCO 6. is.

The adaptive equalizer 3 compensates for the frequency characteristic of the phase-rotated signal, which is the input signal whose phase has been rotated by the first phase rotator 2. In other words, the equalizer eliminates waveform distortion and data errors in the phase-rotated signal. It is a vessel. Here, the adaptive equalizer 3 is composed of a decision feedback equalizer (DFE: Decision Feedback Equalizer) or a linear equalizer. is to be updated.

The phase error detector 4 is a detector that detects a phase error included in the phase rotation signal compensated by the adaptive equalizer 3, and the details will be described later. The phase error includes the phase rotation direction (advance direction or lag direction) and the phase error amount (rotation amount).

The LPF 5 is a filter that removes high frequency components of the phase error detected by the phase error detector 4 according to a predetermined bandwidth, and is composed of a low pass filter.

The NCO 6 is a generator that generates a phase rotation control signal based on the phase error from which the high-frequency components have been removed by the LPF 5, and is composed of an NCO (Numerically Controlled Oscillator). Specifically, a sine wave and a cosine wave having opposite phases are generated based on the phase error from the LPF 5 and output to the first phase rotator 2, thereby controlling the phase rotation by the first phase rotator 2. It is something to do. Furthermore, it outputs the generated phase rotation control signal to the second phase rotator 7 .

The second phase rotator 7 is a rotator/multiplier that rotates the phase of the input signal, and rotates the phase of the input signal based on the phase rotation control signal from the NCO 6 to equalize the frequency characteristics. output to the device 8. That is, the phase of the input signal is rotated based on the sine wave and cosine wave from the NCO 6 based on the phase error detected after frequency characteristic compensation (waveform distortion, etc. is eliminated) by the adaptive equalizer 3 . Thus, the adaptive equalizer 3 is implemented in the carrier recovery loop (the loop of the first phase rotator 2, the phase error detector 4, the LPF 5 and the NCO 6), thereby compensating for the frequency characteristics. Phase noise in the input signal is canceled based on the later estimated phase error value.

Next, the phase error detector 4 will be described. As shown in FIG. 2, the phase error detector 4 includes a polar error detector 41, a full-point error detector 42, and a selection switch 44.

As shown in FIG. 3, the polar error detector 41 detects a signal point S2 located outside the first radius C1 from the origin (the intersection of the I axis and the Q axis) on the complex plane, or from the origin on the complex plane. It is a detector that detects a phase error for at least one of the signal points S2 located within a second radius C2 smaller than the first radius C1.

That is, on a complex plane in which a plurality of reference points (ideal points) S1 are arranged at regular intervals in advance, outside a first radius C1 from the origin, the reference point S1 and the corresponding signal point S2 are The number (3 points in FIG. 3) is small. Similarly, on a complex plane in which a plurality of reference points S1 are arranged in advance at regular intervals, inside a second radius C2 (C2 << C1) from the origin, the reference point S1 and its corresponding signal point The number of S2 (three points in FIG. 3) is small. In other words, the radii C1 and C2 are set so that such a small number of reference points S1 and signal points S2 are to be detected and unstable operation does not occur. Note that when there is no phase error, the reference point S1 and the signal point S2 overlap.

Since the phase error detection range (detectable range) is wide in such a region where there are few reference points S1 and signal points S2, unstable operation due to phase fluctuations is unlikely to occur, and loss of synchronization in carrier wave reproduction is prevented. can be prevented and suppressed. That is, by determining the deviation direction of the signal point S2 with respect to the reference line L with an inclination of 45 degrees, it is possible to reliably detect whether the phase is rotating in the leading direction or in the lagging direction. , the phase error amount can be reliably detected by calculating the shift amount and the rotation amount of the signal point S2 from the reference line L. On the other hand, since the phase error is detected only for a small number of signal points S2, the phase error detection accuracy is low.

Here, the phase error is detected only at the signal point S2 located outside the first radius C1, the phase error is detected only at the signal point S2 located within the second radius C2, or both signals Whether or not to detect the phase error at point S2 is set based on the required accuracy, the predicted amount of phase error, and the like.

The all-point error detection unit 42 detects the phase error within a predetermined range (phase error detection range) W1 centering on the reference point S1 corresponding to the signal point S2 for all the signal points S2 on the complex plane. It is the detection part.

That is, as shown in FIG. 4, a plurality of reference points S1 are arranged in advance on a complex plane at equal intervals in the vertical and horizontal directions. A rectangular phase error detection range W1 is set densely. Then, in each phase error detection range W1, a phase error is calculated and detected as to how much the signal point S2 deviates from the reference point S1 in the advancing direction or the lagging direction. Here, only the signal point S2 located within the phase error detection range W1 is detected, and the signal point S2 located outside the phase error detection range W1 is not detected.

Since the all-point error detector 42 detects the phase error for all the signal points S2 on the complex plane, the phase error can be detected with high accuracy. When this happens, unstable operation may occur due to phase fluctuations, etc., and loss of synchronization may occur in carrier recovery.

The selection switch 44 is a switch that outputs the phase error of one of the polar error detection section 41 and the all-point error detection section 42 to the NCO 6 (LPF 5), and switches the switch according to the switching signal from the polar error detection section 41 .

That is, detection by the polar error detection unit 41 and all-point error detection unit 42 as described above is performed in parallel and input to the selection switch 44, and based on the phase error detected by the polar error detection unit 41, the polar error The phase error of either the detector 41 or the all-point error detector 42 is output to the NCO 6 . Specifically, normally, the phase error of the all-point error detector 42 is output to the NCO 6, and when the phase error detected by the polar error detector 41 is equal to or greater than a predetermined threshold value, unstable operation occurs. A switching signal for outputting the phase error of the polar error detector 41 to the NCO 6 is transmitted from the polar error detector 41 to the selection switch 44 assuming that there is a possibility that the carrier recovery will be out of synchronization. After that, when the phase error detected by the polar error detector 41 becomes less than a predetermined threshold value (or a value lower than that), a switching signal for outputting the phase error of the all-point error detector 42 to the NCO 6 is transmitted from the polar error detector 41 to the selection switch 44 .

Here, the switching signal is transmitted from the polar error detection unit 41 to the selection switch 44. The selection switch 44 determines whether the phase error detected by the polar error detection unit 41 is equal to or greater than a predetermined threshold, You may make it change a switch.

As described above, according to the carrier recovery circuit 1, the phase error of either the polar error detector 41 or the all-point error detector 42 is detected by the NCO 6 based on the phase error detected by the polar error detector 41. Since it is output, it is possible to achieve stable high demodulation performance even at high multi-values. That is, since the all-point error detection unit 42 detects the phase error for all signal points S2 on the complex plane, the phase error can be detected with high precision, but unstable operation due to phase fluctuations due to high multi-valued operation is possible. can lead to loss of synchronization of carrier recovery. On the other hand, the polar error detector 41 detects the phase error only for the signal point S2 that is far outside or near the origin on the complex plane. Since the detectable range of point S2 is wide, unstable operation is unlikely to occur even at high multi-values, and it is possible to prevent or suppress loss of synchronization in carrier wave reproduction.

Therefore, by providing the polar error detection unit 41 and the full-point error detection unit 42 together and switching the output to the NCO 6, it is possible to realize stable and high demodulation performance even at high multi-values. It is.

On the other hand, the phase rotation control signal is generated based on the phase error of the phase rotation signal whose frequency characteristics are compensated (waveform distortion, etc. are eliminated) by the adaptive equalizer 3, and the phase of the input signal is rotated. Even if there is waveform distortion, the phase noise of the carrier wave can be estimated with high accuracy (detected by the phase error detector 4), and high demodulation performance and carrier wave reproduction can be realized. Furthermore, since the adaptive equalizer 3 compensates for the frequency characteristics of the phase rotation signal, it is possible to reduce the influence of thermal noise.

(Embodiment 2)
FIG. 5 is a schematic configuration diagram showing the phase error detector 4 of the carrier recovery circuit 1 according to this embodiment. In this embodiment, based on the phase error detected by the area error detector 43, the phase error of either the polar error detector 41 or the all-point error detector 42 is output to the NCO 6, which is the same as the first embodiment. The configuration is different from that of the first embodiment, and the configuration equivalent to that of the first embodiment is denoted by the same reference numeral, and the description thereof is omitted.

As shown in FIGS. 6 and 7, the area error detection unit 43 detects a detection area DA centered at the origin (the intersection of the I-axis and the Q-axis) on the complex plane. This is a detector that detects a phase error based on how much and in which direction the group of all signal points S2 is shifted.

That is, a plurality of reference points S1 are arranged in advance on the complex plane at equal intervals in the vertical and horizontal directions, and the outer edge thereof is the outer edge of the square detection area DA. The outside of each of the four sides of this detection area DA is divided into two by the I axis or the Q axis, and the eight areas divided in this way are identified as A area and B area sequentially and alternately. there is

Then, the phase error is detected by detecting how far the signal point S2 group deviates from the detection area DA, that is, how much the signal point S2 protrudes into the A area or the B area. For example, as shown in FIG. 6, when the signal point S2 largely protrudes into the A region, the phase rotates in the advance direction, and as shown in FIG. 7, the signal point S2 protrudes largely into the B region. In this case, it is determined and detected that the phase is rotating in the lagging direction. Also, the phase error amount is calculated based on the ratio of the signal point S2 protruding into the A region or the B region (protrusion amount). That is, the correspondence relationship between the protrusion amount and the phase error amount is calculated and stored in advance, and the phase error amount is calculated from the protrusion amount based on this relationship.

Based on the phase error detected by the area error detector 43, the phase error of either the polar error detector 41 or the all-point error detector 42 is output to the NCO 6. FIG. Specifically, during normal operation, the phase error of the all-point error detector 42 is output to the NCO 6, and when the phase error detected by the area error detector 43 is equal to or greater than a predetermined threshold value, an unstable operation occurs. A switching signal for outputting the phase error of the polar error detector 41 to the NCO 6 is transmitted from the area error detector 43 to the selection switch 44 assuming that there is a possibility of loss of synchronization in carrier reproduction. After that, when the phase error detected by the area error detector 43 becomes less than a predetermined threshold value (or a value lower than that), a switching signal for outputting the phase error of the all-point error detector 42 to the NCO 6 is transmitted from the area error detector 43 to the selection switch 44 .

The selection switch 44 switches according to the switching signal from the area error detection section 43 . Here, the switching signal is transmitted from the area error detection unit 43 to the selection switch 44. The selection switch 44 determines whether the phase error detected by the area error detection unit 43 is equal to or greater than a predetermined threshold value. You may make it change a switch.

Thus, according to this embodiment, the phase error of either the polar error detector 41 or the all-point error detector 42 is output to the NCO 6 as in the first embodiment. It is also possible to achieve stable high demodulation performance. At this time, which phase error is to be output to the NCO 6 is selected based on the phase error detected by the area error detector 43, so that an appropriate phase error can be output to the NCO 6.

This is because, in the area error detection unit 43, based on how much and in which direction the group of all signal points S2 around the origin on the complex plane is deviated from the detection area DA around the origin on the complex plane, , to detect the phase error. In other words, whether the phase shift is in the leading direction or the lagging direction and how much the phase shift amount is are detected by the shift state of the entire signal point S2 group with respect to the detection area DA. This makes it possible to prevent or suppress loss of synchronization in carrier reproduction. Based on the phase error detected by the area error detector 43, the phase error of either the polar error detector 41 or the all-point error detector 42 is selected. phase error can be output to the NCO 6.

(Embodiment 3)
FIG. 8 is a schematic configuration diagram showing the phase error detector 4 of the carrier recovery circuit 1 according to this embodiment. This embodiment includes a full-point error detector 42 and an area error detector 43. Based on the phase error detected by the area error detector 43, either the full-point error detector 42 or the area error detector 43 The configuration differs from that of the first embodiment in that the phase error is output to the NCO 6, and the same components as those of the first and second embodiments are denoted by the same reference numerals and descriptions thereof are omitted.

In this embodiment, the phase error of the all-point error detector 42 is normally output to the NCO 6, and when the phase error detected by the area error detector 43 is equal to or greater than a predetermined threshold value, unstable operation occurs. A switching signal for outputting the phase error of the area error detector 43 to the NCO 6 is transmitted from the area error detector 43 to the selection switch 44 . After that, when the phase error detected by the area error detector 43 becomes less than a predetermined threshold value (or a value lower than that), a switching signal for outputting the phase error of the all-point error detector 42 to the NCO 6 is transmitted from the area error detector 43 to the selection switch 44 .

The selection switch 44 switches according to the switching signal from the area error detection section 43 . Here, the switching signal is transmitted from the area error detection unit 43 to the selection switch 44. The selection switch 44 determines whether the phase error detected by the area error detection unit 43 is equal to or greater than a predetermined threshold value. You may make it change a switch.

Thus, according to this embodiment, based on the phase error detected by the area error detector 43, the phase error of either the all-point error detector 42 or the area error detector 43 is output to the NCO 6. Therefore, it is possible to achieve stable high demodulation performance even at high multi-values. That is, since the all-point error detection unit 42 detects the phase error for all signal points S2 on the complex plane, the phase error can be detected with high precision, but unstable operation due to phase fluctuations due to high multi-valued operation is possible. can lead to loss of synchronization of carrier recovery. On the other hand, the area error detector 43 detects whether the phase shift is in the leading direction or the lagging direction and how much the phase shift amount is based on the shift state of the entire signal point S2 group with respect to the detection area DA. Unstable operation is less likely to occur even with multiple values, and it is possible to prevent or suppress loss of synchronization in carrier reproduction.

Therefore, by providing the all-point error detection section 42 and the area error detection section 43 together and switching the output to the NCO 6, it is possible to realize stable and high demodulation performance even at high multilevel. It is. Moreover, unlike the second embodiment, the polar error detection unit 41 is not provided, so the configuration can be simplified.

(Embodiment 4)
FIG. 9 is a schematic configuration diagram showing the phase error detector 4 of the carrier recovery circuit 1 according to this embodiment. In this embodiment, a first cross area error detection unit 45, a second cross area error detection unit 46, and a frequency detection unit 47 are provided. The configuration differs from that of the first embodiment in that the phase error of either the error detection unit 45 or the second cross-shaped area error detection unit 46 is output to the NCO 6. The description will be omitted by adding it.

In this embodiment, as shown in FIG. 10, the constellation CL, which is the area in which the reference points are arranged on the complex plane, is substantially cross-shaped, and the outside of the constellation CL advances along the I-axis or the Q-axis. It is divided into a region and a lag region. That is, a thick cross-shaped constellation CL extending in the I-axis direction and the Q-axis direction is provided around the origin of the complex plane, and reference points (black circles in the figure) are arranged in this constellation CL. Leading regions and lagging regions are alternately provided outside the constellation CL at 45-degree and 135-degree oblique lines that pass through the I-axis, the Q-axis, and the origin.

Specifically, the lead region is on the horizontal end side of the cross in the first quadrant, the lag region is on the Q-axis side of the intersecting interior angle of the cross adjacent thereto, the lead region is on the I-axis side, and the vertical direction of the cross is in the first quadrant. A lag region is provided on the end side. Such lead regions and lag regions are sequentially provided for the second, third and fourth quadrants so as to rotate clockwise. When the number of reference points is an odd power of 2, the constellation CL becomes substantially cross-shaped.

Such leading and lagging regions are provided only outside the outer edge of the constellation CL. Then, the first cross-shaped area error detector 45 determines in which direction and how much the entire signal point group is shifted around the origin on the complex plane, depending on whether more signal points are located in the lead region or the lag region. phase error is detected. In other words, when the signal point protrudes into the lead region more than the lag region, the phase rotates in the lead direction, and when the signal point protrudes into the lag region more than the lead region, the phase rotates in the lag direction. is rotating and detected. Next, the phase error amount is calculated based on the ratio of signal points protruding into the lead region or the lag region (protrusion amount). That is, the correspondence relationship between the protrusion amount and the phase error amount is calculated and stored in advance, and the phase error amount is calculated from the protrusion amount based on this relationship.

In such a first cross-shaped area error detection unit 45, for example, as shown in FIG. 11, the phase error is large and all signal point groups (black circles in the figure) are greatly delayed from the origin (counterclockwise in the figure). ), the number of signal points located in the leading or lagging region is greater in the leading region (erroneous detection region) than in the lagging region (normal detection region), resulting in erroneous detection. Therefore, as shown in FIG. 12, the second cross-shaped area error detection unit 46 expands the leading region and the lagging region to a part inside the constellation CL, and the signal points The phase error is detected by judging in which direction and how much all the signal point groups are deviated from the origin on the complex plane.

That is, the leading region and the lagging region are expanded inside the outer edge of the constellation CL as compared with FIG. Here, the amount of enlargement is set so that the direction of rotation can be accurately detected even when all the signal point clouds rotate significantly. As a result, for example, even when all the signal point groups are largely rotated in the delay direction as in the case of FIG. 11, as shown in FIG. The delay area (normal detection area) is larger than the area), and the rotation direction can be accurately detected. Further, similarly to the first cross-shaped area error detection unit 45, the phase error amount is calculated based on the ratio of signal points that protrude into the lead region or the lag region (protrusion amount).

In the second cross-shaped area error detection unit 46, the leading region and the lagging region are expanded inside the constellation CL. Therefore, when the phase error is small, the number of signal points subject to detection error is reduced. . That is, as shown in FIG. 13, in the area where the constellation CL overlaps with the leading region and the lagging region (the dashed ellipse in the figure), when the phase error is small, there is no change in the number of signal points in the leading region and the lagging region. Therefore, phase error detection cannot be performed.

Therefore, the frequency detection unit 47 detects the phase error of either the first cross area error detection unit 45 or the second cross area error detection unit 46 based on the frequency with which the signal points are positioned outside the constellation CL. Determines whether to output to NCO 6. That is, as shown in FIG. 14, the frequency at which signal points (black circles in the figure) are positioned outside the constellation CL and the number of signal points (the number positioned within the ellipse in the figure) are detected. When the frequency is low, as shown in FIG. 15, a switching signal for outputting the phase error detected by the first cross-shaped area error detector 45 to the NCO 6 is transmitted to the selection switch 44, and the frequency is high. In this case, as shown in FIG. 16, a switching signal for outputting the phase error detected by the second cross-shaped area error detector 46 to the NCO 6 is transmitted to the selection switch 44 . In accordance with this, the selection switch 44 switches and outputs the phase error of either the first cross-shaped area error detection section 45 or the second cross-shaped area error detection section 46 to the NCO 6 .

Thus, according to this embodiment, either the first cross area error detection section 45 or the second cross area error detection section 46 is detected based on the frequency with which the signal points are positioned outside the constellation CL. is output to the NCO 6, it is possible to achieve stable and high demodulation performance even with high multi-values. That is, the first cross-shaped area error detection unit 45 determines in which direction and how much the entire signal point group is shifted depending on whether more signal points are located in the leading region or the lagging region, which are outside the constellation CL. is determined to detect the phase error, it is possible to secure a large number of signal points from which the phase error can be detected. On the other hand, in the second cross-shaped area error detection unit 46, the directions of all the signal points are determined depending on whether more signal points are located in the leading region or the lagging region expanded to a part inside the constellation CL. Since the phase error is detected by determining how much the deviation is, it is possible to more accurately determine in which direction the deviation occurs.

Therefore, by providing the first cross-shaped area error detection section 45 and the second cross-shaped area error detection section 46 together and switching the output to the NCO 6, stable high demodulation performance can be achieved even at high multi-values. It is possible to realize it.

(Embodiment 5)
FIGS. 19 to 22 show this embodiment, which differs from the second embodiment in that it has a phase error detection area SA. The description is omitted by attaching the reference numerals.

First, in the second embodiment, as shown in FIG. 17, when all signal point groups (black circles in the figure) rotate in the leading direction (counterclockwise in the figure), there are more signal points in the leading region than in the lagging region. position, it can be determined that the entire signal point cloud has rotated in the forward direction. However, after that, if the rotation due to the frequency error is fast and all the signal point clouds are further rotated in the lead direction before loop entrainment (compensation of frequency characteristics) starts, the lag region will be larger than the lead region, as shown in FIG. Since many signal points are located at , it is determined that all signal points have rotated to the lag region. That is, if the frequency error is large, it becomes difficult to pull in the loop.

Therefore, in this embodiment, a phase error detection area SA is provided. That is, as shown in FIG. 19, similarly to the second embodiment, the constellation CL, which is the region in which the reference points (black circles in the figure) are arranged on the complex plane, has a substantially rectangular shape, and the outside of the constellation CL is divided into a leading region and a lagging region with the I-axis and Q-axis as boundaries. Then, the area including the corners of the constellation CL and the outside thereof is defined as the phase error detection area SA. In other words, the phase error detection area SA is a substantially rectangular area that includes the corners of the constellation CL and the ends of the lead area and the lag area. The size of the phase error detection area SA is set so as to accurately determine in which direction all the signal point groups are shifted, as will be described later.

In the phase error detector 4 according to this embodiment, as shown in FIG. 20, when a signal point (black circle in the drawing) is positioned in the phase error detection area SA, the signal point is in the lead area and the lag area. It is determined in which direction all the signal points are deviated from the origin on the complex plane, depending on which of the two is most located. For example, in the case of FIG. 20, it is determined that there is a deviation in the advancing direction. On the other hand, as shown in FIG. 21, when the signal point is not positioned in the phase error detection area SA, it is determined that all the signal point groups are deviated in the previously determined direction. In other words, the previous judgment is maintained. For example, when the state shown in FIG. 20 shifts to the state shown in FIG. 21, it is determined that the state shown in FIG.

The direction of deviation is determined in this manner, and the phase error is detected based on how far the signal point is positioned in the lead region or the lag region. That is, the phase error amount is calculated based on the ratio (extension amount) of the signal points located in the lead region or the lag region determined to be in the direction of deviation. At this time, the correspondence relationship between the protrusion amount and the phase error amount is calculated and stored in advance, and the phase error amount is calculated from the protrusion amount based on this relationship.

Thus, according to this embodiment, only when the signal point is located in the phase error detection area SA, it is determined in which direction all the signal points are deviated, and the signal point is located in the phase error detection area SA. , it is determined that all the signal points are deviated in the direction determined immediately before. Therefore, even if the rotation due to the frequency error is fast and the position area of the signal point immediately reverses to the lead area and the lag area before the loop pull-in (compensation of frequency characteristics) starts, it is easier to know in which direction the deviation is. Accurate judgment is possible.

For example, as shown in FIG. 20, when the entire signal point group rotates counterclockwise, it is determined that the signal point is shifted in the advance direction because the signal point is located in the phase error detection area SA. Subsequently, as shown in FIG. 21, even if all the signal point groups further rotate counterclockwise and the signal points are no longer located in the phase error detection area SA, all the signals continue to move in the previously determined direction, that is, the advance direction. It is judged that the point cloud is deviated. Even if the counterclockwise rotation progresses further and many signal points are located in the delay area (FIG. 18), the signal points are not located in the phase error detection area SA. to decide. Therefore, as shown in FIG. 22, clockwise loop pull-in with respect to the advance direction acts to suppress the phase rotation. As a result of accurately judging the direction of deviation in this way, it is possible to achieve stable high demodulation performance even at high multi-values.

Although the embodiments of the present invention have been described above, the specific configuration is not limited to the above-described embodiments. Included in the invention.

1 carrier recovery circuit 2 first phase rotator (phase rotator)
3 adaptive equalizer 4 phase error detector 41 polar error detector 42 all-point error detector 43 area error detector 44 selection switch 45 first cross area error detector 46 second cross area error detector 47 frequency detector Part 5 LPF
6 NCO (rotation signal generator)
7 second phase rotator 8 equalizer S1 reference point S2 signal point DA detection area CL constellation SA phase error detection area

Claims (2)

a phase rotator that rotates the phase of an input signal; a phase error detector that detects a phase error included in a phase rotated signal that is the input signal whose phase has been rotated by the phase rotator; a rotation signal generation unit that generates a rotation control signal, wherein the phase rotator is a carrier recovery circuit that rotates the phase of the input signal based on the phase rotation control signal,
The phase error detector is
A plurality of reference points are arranged in advance on a complex plane at equal intervals in the vertical and horizontal directions, and a quadrangular phase error detection range centered on the reference points is set so as to divide the reference points in the vertical and horizontal directions at equal intervals, and an all-point error detection unit for detecting, for all signal points on a complex plane, the phase error in the phase error detection range centered on the reference point corresponding to the signal point;
At least one of signal points located outside the first radius from the origin on the complex plane, or signal points located within a second radius smaller than the first radius from the origin on the complex plane. a polar error detector that detects a phase error for the
A plurality of reference points are arranged in advance on a complex plane at regular intervals vertically and horizontally, and a square detection area centered on the origin on the complex plane and having an outer edge of the entire reference points is set as an outer edge, and the detection area is On the other hand, an area error detection unit that detects the phase error based on how much and in which direction all the signal point groups are deviated from the origin on the complex plane;
and outputting the phase error of either the full-point error detection unit or the polar error detection unit to the rotation signal generation unit based on the phase error detected by the area error detection unit.
A carrier recovery circuit characterized by: a phase rotator that rotates the phase of an input signal; a phase error detector that detects a phase error included in a phase rotated signal that is the input signal whose phase has been rotated by the phase rotator; a rotation signal generation unit that generates a rotation control signal, wherein the phase rotator is a carrier recovery circuit that rotates the phase of the input signal based on the phase rotation control signal,
The phase error detector is
A plurality of reference points are arranged in advance on a complex plane at equal intervals in the vertical and horizontal directions, and a quadrangular phase error detection range centered on the reference points is set so as to divide the reference points in the vertical and horizontal directions at equal intervals, and an all-point error detection unit for detecting, for all signal points on a complex plane, the phase error in the phase error detection range centered on the reference point corresponding to the signal point;
A plurality of reference points are arranged in advance on a complex plane at regular intervals vertically and horizontally, and a rectangular detection area centered on the origin on the complex plane and having an outer edge of the entire reference points is set as an outer edge, and the detection area is On the other hand, an area error detection unit that detects the phase error based on how much and in which direction all the signal point groups are deviated from the origin on the complex plane;
and outputting the phase error of either the all-point error detection unit or the area error detection unit to the rotation signal generation unit based on the phase error detected by the area error detection unit.
A carrier recovery circuit characterized by:

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