JP4120937B2 - Phase rotation method and phase rotation device - Google Patents

Description

  The present invention relates to a phase rotation method and a phase rotation apparatus for rotating a signal phase to a desired phase by digital signal processing.

  In various signal processing, various means for adjusting the signal phase are applied. In general, the phase of a signal represented on rectangular coordinates is subjected to multiplication / division or addition / subtraction processing on the in-phase component signal (I) and the quadrature component signal (Q) of the signal, and then combined. Can be rotated. Also, in the quadrature demodulation circuit of the receiving apparatus to which the quasi-synchronous detection method is applied, the received quadrature modulation signal is demodulated into I and Q quadrature signals by a demodulation carrier having a phase difference of π / 2, and each is converted into a digital signal A configuration in which a phase rotation circuit that converts and corrects a phase offset is provided is known (see, for example, Patent Document 1).

  In addition, navigation systems are known that can receive and demodulate radio waves from multiple satellites orbiting the earth and calculate the three-dimensional position and movement speed of the reception point of these radio waves. The machine has a function of processing a quadrature demodulated signal and is provided with means such as phase shift. As a configuration for that purpose, for example, signal points corresponding to the amplitude and phase of the signal are stored in the memory in correspondence with the X component value and the Y component value of the orthogonal coordinates of the X and Y axes, and the signal phase The phase rotation process is performed by reading the X component value and the Y component value corresponding to the signal point corresponding to the rotation position. However, in this configuration, when the signal point is moved by the phase rotation, depending on the rotation angle, the orthogonal lattice is obliquely crossed in addition to the vertical and horizontal directions, and the error greatly varies depending on the phase rotation position.

  Therefore, the trajectory along which the signal point moves according to the phase rotation is a concentric circle with the coordinate origin as the center, and the signal point is placed on each circle and stored in the memory. That is, by using a memory in which signal points are stored with a configuration similar to polar coordinates, changes in error due to the phase rotation position are reduced. In that case, the level of the input signal is once converted into a level corresponding to the radius of the circle in which the signal points are arranged, the signal points after phase rotation are read from the memory, and the levels are reconverted (for example, , See Patent Document 2).

Further, in the demodulating circuit in data transmission, the phase rotation of the I and Q signals orthogonal by digital processing is performed by, for example, trigonometric function multiplying units 21 to 24 and adders 25 and 26 as shown in FIG. Means for processing according to the provided configuration is known. In this case, with the I and Q signals and the phase rotation amount θ, the trigonometric function multipliers 21 to 24 and the adders 25 and 26
I ′ = I cos θ−Q sin θ
Q ′ = Isin θ + Q cos θ
The quadrature signals I ′ and Q ′ rotated in phase according to the phase rotation amount θ can be obtained. It is known that the trigonometric function can be expressed by a power of 2, and the trigonometric function multipliers 21 to 24 can be realized by a configuration including a plurality of shift registers, adders, and selectors (for example, And Patent Document 3).
JP-A-6-181475 Japanese Patent Laid-Open No. 11-17756 Japanese Patent Publication No. 7-65901

  Various methods have already been proposed for signal phase rotation processing as described above, but since the signal after phase rotation is also a digital signal, the maximum value that can be handled depending on the number of bits to be processed. Will be decided. For example, as shown in FIG. 5A, assuming that the maximum values of the I and Q signals are the same values of Imax and Qmax, the I and Q signals of the signal A having a phase angle of π / 4 are the maximum values. Imax and Qmax. When the signal A is rotated by the phase rotation amount φ, the signal A becomes a signal A ′. The signal A ′ has the same level (amplitude) as the signal A, but the in-phase component signal I is less than the maximum value Imax, the quadrature component signal Q exceeds the maximum value Qmax, and the signal processing is in an overflow state. Become. Therefore, as shown in FIG. 5B, the in-phase component signal I of the signal A ′ is less than or equal to the maximum value, but the quadrature component signal Q is limited to the maximum value Qmax. After that, the signal becomes A ″. Therefore, a phase difference of δ is generated between the phase-rotated signal A ′ and the signal A ″ processed so as not to exceed the maximum value. That is, there is a problem that a phase error δ is generated by the phase rotation process.

  Such a problem also occurs when the signal points described above are arranged concentrically and stored in the memory. In order to reduce such a phase error δ, when the I and Q signals after phase rotation exceed the maximum values Imax and Qmax, it is necessary to perform a process of reducing the signal that does not exceed according to the exceeding ratio. There arises a problem that the phase rotation processing becomes complicated.

  An object of the present invention is to limit a signal component after phase rotation to a maximum value and reduce a phase error by a relatively simple process and configuration.

  According to the phase rotation method of the present invention, the in-phase component signal and the quadrature component signal of the signal for phase rotation are converted into an amplitude component and an angle component by polar coordinate conversion, and a rotation angle component obtained by adding a phase rotation amount to the angle component. When the amplitude component obtained by polar coordinate conversion exceeds the maximum value, the amplitude component is limited to the maximum value, and the amplitude component and the amplitude component This includes a process of converting into an in-phase component signal and a quadrature component signal by orthogonal coordinate transformation based on the rotation angle component obtained by adding the phase rotation amount.

  The phase rotation device according to the present invention includes a polar coordinate conversion unit that receives an in-phase component signal and a quadrature component signal of a signal that performs phase rotation and converts the signal into an amplitude component and an angle component, and the angle component from the polar coordinate conversion unit. A phase rotation unit that adds a phase rotation amount to the rotation angle component and outputs a rotation angle component; obtains a maximum value of an amplitude component corresponding to the rotation angle component from the phase rotation unit; and calculates the maximum value and the amplitude component from the polar coordinate conversion unit And an amplitude adjustment unit that outputs an amplitude component in which the amplitude component is limited to the maximum value or less, an amplitude component from the amplitude adjustment unit, and a rotation angle component from the phase rotation unit are input to be in phase An orthogonal coordinate conversion unit for converting into a component signal and an orthogonal component signal is provided.

  The amplitude adjustment unit of the phase rotation device stores the maximum value of the amplitude component with respect to the angle component, and reads out the maximum value using the rotation angle component from the phase rotation unit as an address, and the maximum value read from the memory. And a calculation unit that compares the value with the amplitude component from the polar coordinate conversion unit and limits the amplitude component so as not to exceed the maximum value.

  When the signal phase is rotated by the phase rotation amount φ by digital signal processing, it is converted to polar coordinates, phase rotation processing is performed by adding the phase rotation amount to the angle component, and the amplitude component after the phase rotation is maximized Since conversion into rectangular coordinates is performed by limiting the value, the in-phase component and the orthogonal component after conversion do not exceed the maximum value, that is, overflow does not occur, so that no phase error occurs. Also, the amplitude can be adjusted to the minimum necessary.

  In the phase rotation method of the present invention, the in-phase component signal I and the quadrature component signal Q of the signal for phase rotation are converted into an amplitude component r and an angle component θ by polar coordinate conversion, and the phase rotation amount φ is set as the angle component θ. The maximum value r′max of the amplitude component in the added rotation angle component θ ′ is obtained, and when the amplitude component r obtained by polar coordinate conversion exceeds the maximum value r′max, the amplitude component r is converted to the maximum value r. An amplitude component r limited to “max” is converted into an in-phase component signal I ′ and a quadrature component signal Q ′ by orthogonal coordinate conversion based on the amplitude component and a rotation angle component θ ′ obtained by adding the phase rotation amount φ. Process.

  The phase rotation device according to the present invention receives a in-phase component signal I and a quadrature component signal Q of a signal for phase rotation and converts them into an amplitude component r and an angle component θ, and the polar coordinate conversion unit 1 The phase rotation unit 3 that adds the phase rotation amount φ to the angle component θ from the output and outputs the rotation angle component θ ′, and the maximum value r ′ of the amplitude component corresponding to the rotation angle component θ ′ from the phase rotation unit 3 When max is obtained, the maximum value r′max is compared with the amplitude component r from the polar coordinate conversion unit 1, and when the amplitude component r does not exceed the maximum value, it is output as it is, and when it exceeds the maximum value Is supplied with the amplitude adjustment unit 2 that outputs the amplitude component r ′ limited to the maximum value, the amplitude component r ′ from the amplitude adjustment unit 2 and the rotation angle component θ ′ from the phase rotation unit 3 and inputs the same phase. An orthogonal coordinate conversion unit 4 for converting the component signal I and the orthogonal component signal Q is provided. To have.

  FIG. 1 is an explanatory diagram of Embodiment 1 of the present invention, where 1 is a polar coordinate conversion unit, 2 is an amplitude adjustment unit, 3 is a phase rotation unit, and 4 is an orthogonal coordinate conversion unit. I and Q signals represented by orthogonal coordinates are input to the polar coordinate conversion unit 1 and converted into polar coordinates (r, θ) by an amplitude (radial radius) component r and an angle component θ. The phase rotation unit 3 adds the phase rotation amount φ to the angle component θ converted by the polar coordinate conversion unit 1 and inputs the added rotation angle component θ ′ to the amplitude adjustment unit 2 and the orthogonal coordinate conversion unit 4.

The amplitude adjustment unit 2 obtains the maximum value r′max of the amplitude component corresponding to the rotation angle component θ ′ input from the phase rotation unit 3, and determines whether the amplitude component r from the polar coordinate conversion unit 1 exceeds the maximum value. Determine whether. This maximum value r'max is shown in parentheses for the Q signal:
r′max = I (Q) max / cos θ ′
(However, 0 ≦ | θ ′ | ≦ π / 4 and 3π / 4 ≦ | θ ′ | ≦ π)
r′max = I (Q) max / sin θ ′
(However, π / 4 ≦ | θ ′ | ≦ 3π / 4)
Can be obtained as

  If the amplitude component r does not exceed the maximum value r′max when rotated in accordance with the rotation angle component θ ′, the amplitude component r ′ is output as it is, and if it exceeds, the amplitude component r is output as the rotation angle component θ ′. Is output as an amplitude component r ′ limited to the maximum value, and the amplitude component is input to the orthogonal coordinate transformation unit 4, and the adjustment amount rc = (amplitude component r−maximum value of the amplitude component after phase rotation) r′max) is output to the subsequent processing circuit. When the amplitude component r does not exceed the maximum value, r = r ′ is input to the orthogonal coordinate conversion unit 4 and the adjustment amount rc = 0 at that time is set.

The orthogonal coordinate conversion unit 4 is based on the amplitude component r ′ and the rotation angle component θ ′.
I ′ = r′cos θ ′
Q ′ = r′sin θ ′
Thus, the orthogonal I ′ and Q ′ signals after phase rotation can be output. In this case, the maximum value is not exceeded. That is, since no overflow occurs, no phase error occurs. When the amplitude component is limited according to the maximum value, it can be corrected so as to become the original amplitude component by the adjustment amount rc in the subsequent processing circuit.

  FIG. 2 is an explanatory diagram of the phase rotation processing. As shown in FIG. 2A, the in-phase component signal I of the signal of the amplitude (radial) component r at the phase angle of π / 4 has a maximum value Imax and is orthogonal. When the component signal Q is also the maximum value Qmax, the polar coordinate conversion unit 1 converts the input in-phase component signal I and the quadrature component signal Q into an amplitude (radial) component r and an angle component θ (in this case, θ = π). / 4), and when rotating according to the phase rotation amount φ as the control information, the phase rotation unit 3 adds the rotation angle component θ ′ obtained by the processing of θ ′ = θ + φ to the amplitude adjustment unit 2.

  The amplitude adjustment unit 2 obtains the maximum value r′max of the amplitude component of the signal after phase rotation by using the amplitude component r and the rotation angle component θ ′, and compares it with the amplitude component r. When r exceeds the maximum value r′max, the amplitude component r is set to r ′ limited to the maximum value.

  When the amplitude component r ′ limited to the maximum value is rotated according to the phase rotation amount φ, the state shown in FIG. 2B is obtained, and the amplitude component r ′ after the phase rotation exceeds the maximum value Qmax of the quadrature component signal Q. And no phase error occurs. For example, if the angle component θ = π / 4 and the phase rotation amount φ = π / 12, the rotation angle phase θ ′ = θ + φ = π / 3. When the amplitude component r = 1, the maximum value of the in-phase component I and the quadrature component Q when the angle component θ = π / 4 is about 0.7. The maximum value r′max of the amplitude component when the rotation angle phase θ ′ = π / 3 is about 0.8. Accordingly, the amplitude component r ′ in which the amplitude component r = 1 is limited to the maximum value r′max≈0.8 is output to the orthogonal transform unit 4. The orthogonal coordinate conversion unit 4 converts the in-phase component signal I ′ and the orthogonal component signal Q ′ based on the amplitude component r ′ and the rotation angle phase θ ′. The same applies to the case where the rotation direction is reversed. In this case, the amplitude component r can be limited so as not to exceed the maximum value Imax of the in-phase component signal I.

  FIG. 3 is an explanatory diagram of Embodiment 2 of the present invention, and the same reference numerals as those in FIG. 1 denote the same names. In this embodiment, the amplitude adjustment unit 2 includes a memory 5 and a calculation unit 6, and the memory 5 stores data on the relationship between the rotation angle component θ ′ and the maximum value r′max of the amplitude component. The rotation angle component θ ′ from the phase rotation unit 3 is input to the memory 5 as an address, the maximum value is read and input to the calculation unit 6.

  The calculation unit 6 compares the amplitude component r from the polar coordinate conversion unit 1 with the maximum value r′max from the memory 5. If r ≧ r′max, the calculation unit 6 directly converts the amplitude component r to the orthogonal coordinate conversion unit 4. When the amplitude component r ′ is input, and r ≦ r′max, the maximum value is input to the orthogonal coordinate conversion unit 4 as the amplitude component r ′. Similarly to the above-described embodiment, the orthogonal coordinate conversion unit 4 converts the in-phase component signal I ′ and the orthogonal component signal Q ′ after phase rotation by orthogonal coordinate conversion based on the amplitude component r ′ and the angle component θ ′. Convert and output.

  The memory 5 does not store the maximum value r′max over the angle range of 2π, for example, stores the maximum value r′max over the angle range of 0 to π / 2, and the angle component θ ′ is 0 to π. If it is not in the range of / 2, it is possible to read out the maximum value by converting the address and accessing. Thereby, the memory 5 can be downsized. The arithmetic unit 6 can be realized with a simple configuration having comparison and subtraction processing functions.

It is explanatory drawing of Example 1 of this invention. It is explanatory drawing of a phase rotation process. It is explanatory drawing of Example 2 of this invention. It is explanatory drawing of a prior art example. It is explanatory drawing of the phase rotation process of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polar coordinate conversion part 2 Amplitude adjustment part 3 Phase rotation part 4 Cartesian coordinate conversion part 5 Memory 6 Calculation part

Claims (3)

In the phase rotation method of rotating the signal phase,
The in-phase component signal and the quadrature component signal of the signal for phase rotation are converted into an amplitude component and an angle component by polar coordinate conversion, and the amplitude component obtained by the polar coordinate conversion adds the phase rotation amount to the angle component. When the maximum value of the amplitude component in the rotation angle component is exceeded, the amplitude component is limited to the maximum value, and based on the rotation angle component obtained by adding the amplitude component and the phase rotation amount A phase rotation method comprising a step of converting into an in-phase component signal and a quadrature component signal by orthogonal coordinate transformation. In a phase rotation device that rotates a signal phase,
A polar coordinate conversion unit that inputs an in-phase component signal and a quadrature component signal of a signal that performs phase rotation and converts them into an amplitude component and an angle component;
A phase rotation unit that adds a phase rotation amount to the angle component from the polar coordinate conversion unit and outputs a rotation angle component;
The maximum value of the amplitude component corresponding to the rotation angle component from the phase rotation unit is obtained, the maximum value is compared with the amplitude component from the polar coordinate conversion unit, and the amplitude component in which the amplitude component is limited to the maximum value or less is obtained. An amplitude adjustment unit to output;
A phase rotation apparatus comprising: an orthogonal coordinate conversion unit that inputs an amplitude component from the amplitude adjustment unit and a rotation angle component from the phase rotation unit and converts the component into an in-phase component signal and a quadrature component signal .   The amplitude adjustment unit stores a maximum value of an amplitude component with respect to an angle component, reads out the maximum value using the rotation angle component from the phase rotation unit as an address, and converts the maximum value read from the memory and the polar coordinate conversion The phase rotation device according to claim 2, further comprising: an arithmetic unit that compares the amplitude component from the unit and limits the amplitude component so as not to exceed the maximum value.

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