JP2605549B2 - Complex angle converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a complex angle converter used in digital modulation to obtain phase information from a baseband signal of a demodulation unit for angle modulation.

[0002]

2. Description of the Related Art In recent years, in the field of mobile communication, miniaturization and low power consumption have been promoted in terms of portability. Also,
While digitization is progressing rapidly, each component is required to be similarly miniaturized and simplified.

[0003] A conventional complex angle converter will be described below. FIG. 5 shows a configuration of a conventional complex angle converter. In FIG. 5, reference numeral 501 denotes a complex baseband in-phase digital output (I-ch, m bits) after quadrature demodulation. Reference numeral 502 denotes the quadrature output (Q-ch, m bits). Reference numeral 503 denotes an arctangent ROM, which is input (m
-1) bits and output (n-2) bits. 504 is
Quadrant determination circuit , 505 outputs angle data (n bits)
It is.

The operation of the complex angle converter configured as described above will be described below. First, the demodulated digital angle-modulated wave is input as digital data 501 and 502 as in-phase and quadrature components, respectively.
If the quadrant is not considered, the angle data can be converted by taking the arc tangent from the lower (m-1) bits of each of I-ch and Q-ch. If this data is written in the arctangent ROM 503, complex-angle conversion can be performed. After that, if the quadrant is determined by each of the MSBs of the complex data by the quadrant determining circuit 504, the absolute phase angle can be output.

[0005]

However, in the above-mentioned conventional configuration, the arc tangent ROM 503 in which the arc tangent is calculated is required, and it is necessary to increase the capacity of the arc tangent ROM 503 in order to improve the accuracy. Had the problem of becoming

An object of the present invention is to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a complex angle converter having a simple configuration without using a large-scale ROM.

[0007]

In order to achieve this object, a first aspect of the present invention is to compare magnitudes of absolute values of an in-phase signal and a quadrature signal which are demodulated complex baseband signals of a digital angle-modulated wave. An absolute value comparator and a set of bits other than the most significant bit MSB of the in-phase signal and the most significant bit MSB of the quadrature signal, and the most significant bit MSB of the quadrature signal, based on the comparison result of the absolute value comparator A selector for switching and outputting a set of bits other than the most significant bit MSB of the in-phase signal; and a most significant bit MSB of the in-phase signal.
And the most significant bit MSB of the quadrature signal to determine in which quadrant the demodulated complex baseband signal is located , and the selector selects a most significant bit MSB of the in-phase signal and a bit other than the most significant bit MSB of the quadrature signal. Is determined based on the most significant bit MSB of the in-phase signal, whether or not to invert bits other than the most significant bit MSB of the quadrature signal is determined. Are output as angle data on the complex plane, while the selector outputs a set of bits other than the most significant bit MSB of the quadrature signal and the most significant bit MSB of the in-phase signal. Then, based on the most significant bit MSB of the quadrature signal, it is determined whether or not to invert bits other than the most significant bit MSB of the in-phase signal. Bits other than the most significant bit MSB of the inverted the phase signal is provided with a decoder for outputting as the angle data on the complex plane. In addition to the above configurations, the second configuration of the present invention is provided with a complex plane degenerating circuit that maps a fixed area on a complex plane to a certain point before the absolute value comparator.

[0008]

According to the present invention, a complex angle converter can be realized with the above-mentioned structure without using a complicated ROM or the like.

[0009]

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a basic configuration of a complex angle converter according to one embodiment of the present invention. In FIG. 1, 1
01 is in-phase demodulated baseband digital data, 1
02 is orthogonal data, 103 is data 101 and 102
, 104 is a selector, 105 is a decoder, and 106 is data of a complex plane phase angle. FIG. 2 shows a more specific configuration of FIG. In FIG. 2, reference numeral 201 denotes in-phase input (m-bit) data;
Reference numeral 202 denotes orthogonal input (m-bit) data, which correspond to the data 101 and 102 in FIG. 1, respectively. An absolute value comparator (m-bit) 203 compares the absolute values of the data 201 and 202 with each other, and corresponds to the absolute value comparator 103 in FIG. A selector 204 (m bits) corresponds to the selector 104 in FIG. 205 is a multi-input bit inverter (m-
1), 206 is an inverter, and 207 is an exclusive-OR gate .
Respond. Incidentally, 208 is at an angle data output (m + 1 bit), similar to the data 106 in the complex plane the phase angle of Fig. 1
Things.

The operation of the complex angle converter configured as described above will be described using a region on a complex plane shown in FIG.

First, the waveform on the baseband complex plane when the modulated wave that has been angle-modulated and transmitted on the transmission side is orthogonally detected on the reception side (an ideal case where the influence of noise and the like is not considered) is, for example, A or B of FIG. A is
This is the case where an analog mixer or the like is used as the detector.
Is a case where an EX-OR logic mixer is used as a detector.

Now, it is assumed that the complex waveform after detection is contained in a substantially constant area by an appropriate means (limiter, AGC, etc.) in the receiving unit. Then, in the case of A, the area can be divided on the plane as follows. That is, the absolute value comparator 2
03, data 2 of the in-phase component (hereinafter referred to as Ich)
01 and the distance from the origin of the data 202 of the orthogonal component (hereinafter referred to as Qch), and the most significant bit MSB with the larger distance at that time can be divided into four areas. A portion of | I |> | Q | and I> 0, which is a part of the region, is indicated by a thick line E on the circumference in FIG. Then, in this part, the increasing direction of the Qch data coincides with the increasing direction of the angle, and the lower (m-1) bit of the Qch and the lower (m-1) bit of the angle can be expressed almost one-to-one. , The lower (m-1) bits of Qch can be used as they are as angle bits. Hereinafter, the reason will be described in detail with reference to FIG. In the case of an analog mixer, the angle is approximately converted into an angle.
The output of the analog mixer is a limiter signal as shown in FIG. 3A, and the level is considered as a circle inscribed in the locus B of the digital mixer. Now, in FIG. 6, FIG.
Among the outputs A of the analog mixer shown in FIG. 6, consider the one existing in the first quadrant, and compare the absolute values of the in-phase and quadrature components into two regions. | In-phase component |> |
A description will be given of a region E corresponding to the orthogonal component |, that is, a portion corresponding to 0 to π / 4 rad in terms of the absolute angle of the complex plane. Thinking in this range does not lose generality
No. For example, the range of π / 4 to π / 2 in the first quadrant holds when the above range is replaced with the in-phase and quadrature components. First, in FIG. 6, A: output distribution of analog mixer B: output distribution of digital mixer D: point where A and B meet (corresponding to π / 4 rad) E: in the first quadrant of analog mixer output A | component
|> | Rectangular component | area (0 to π / 4 in absolute angle)
rad range) F: A = (r, 0 point of intersection is in phase axis (I)) G: is a perpendicular line to the phase axis that intersects the phase axis from D =
(R / R2, 0) (where R2 represents the square root of 2 = sqrt (2)) H: Point where the perpendicular drawn from P to the orthogonal axis intersects line segment DG P: Output with analog mixer R: radius of the circle of A θ: phase difference between the received modulation signal and the internal phase reference (that is, the input of the complex angle converter). Now, in FIG. 6, the phase of the received signal is
Assuming that the angle data θ (0 <θ <π / 4) and the output of the analog mixer is P = (x, y), x = r · cos θ and y = r · sin θ hold. Since the lower data having the smaller absolute value is used, the y component corresponds to the angle. That is, y = r · sin θ (0 <θ <π / 4) (1) However, θ and y have a one-to-one correspondence
However, y does not actually change linearly with respect to the angle θ.
No. Therefore, the angle θ is reset via the orthogonal component y of P.
New angle data by approximation that changes near
to θ '. That is, θ: 0 <θ <π / 4 → y: 0 <y <r / R2 → θ ′: Conversion is performed such that 0 <θ ′ <π / 4, and y and θ ′ have a linear relationship.
Suppose there is. However, because of conversion by approximation, θ = 0 and
When θ = π / 4, θ = θ ′ holds, but in addition,
Is θ ≒ θ ', and when replacing θ with θ'
An error occurs. Below, the conversion procedure from θ to θ 'and its
The error will be described. When θ moves from 0 to π / 4, y
Moves from 0 to r / R2. At this time, the relationship between θ and y is
It is expressed by equation (1). Next, when y moves from 0 to r / R2,
And data θ ' that moves linearly in the range of 0 to π / 4 with y
Is assumed. That is, the relationship between y and θ ′ is

(Equation 1) Is defined as From the above equations (1) and (2), θ and θ ′
The relationship is

(Equation 2) Becomes In this equation, when θ = 0, θ ′ = 0, θ =
When π / 4, θ ′ = π / 4 holds. Furthermore, 0 <θ <
The mean square of the error △ θ between θ and θ 'in the range of π / 4
When evaluated with

(Equation 3) And the error is considered to be small. Therefore, 0 <
New angle data θ by approximation in the range of θ <π / 4
It can be replaced with the new angle data θ ′. You
That is, the y component of the output of the analog mixer and the angle data
Is strictly expressed by equation (1), but by approximation
Expression by equation (2) by replacing θ with θ '
Becomes possible. From the above description, the lower Qch (m-
1) It can be seen that the bit can be used as an angle bit almost as it is. As a result, two bits for determining the area can be output as (m + 1) -bit angle data. In some cases, it is necessary to invert the direction of one of the lower (m-1) bits selected by the selector 204 based on the relationship between the increasing direction and the increasing direction of the angle. As shown in FIG. 2, the inverter 206 and the multi-input bit inverter 20
5 is required. That is, the Ich
Are output, a bit set other than the most significant bit MSB of Qch and the most significant bit MSB of Qch is output.
In 05, it is determined whether or not bits other than the most significant bit MSB of the Qch are to be inverted based on the most significant bit MSB of the Ich, and the inverted and non-inverted bits other than the most significant bit MSB of the Qch are converted to a complex plane. Output as upper angle data. On the other hand, when a set of bits other than the most significant bit MSB of Qch and the most significant bit MSB of Ich is output from the selector 204, the most significant bit M of the Qch is output.
Based on the SB, it is determined whether or not bits other than the most significant bit MSB of the Ich are inverted, and the inverted and non-inverted bits other than the most significant bit MSB of the Ich are output as angle data on a complex plane. . Note that inverter 2
06 and the exclusive OR gate 207 determine which quadrant the demodulated complex baseband signal is in from the most significant bit MSB of Ich and the most significant bit MSB of Qch.

In the case of B, the same argument holds because the phase and angle of the complex plane correspond linearly.

As described above, according to this embodiment, the absolute value comparator 203 and the selector 20 can be used without using a ROM.
4. A complex angle converter can be provided by a simple logic circuit such as the inverter 206.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 4 differs from the configuration of FIG. 2 in that a complex plane degenerating circuit 403 is added. Accordingly, the data 401 and 402 become complex inputs in the present embodiment.

The operation of the complex angle converter configured as described above will be described below. Complex plane degeneration circuit 4
The role of 03 is to map the area C in FIG. 3 to a point D where A and B intersect, respectively. Until now, an ideal case such as the complex envelopes A and B in FIG. 3 has been considered. However, when the complex data falls into the region C due to noise, system imperfection, or the like, the mistake is made. Will give the result. This is because, when a certain area is determined as described above, one lower-order (m-1) bit is directly converted into angle data, so that when the data enters an area such as C, the data becomes one round. And may output incorrect results. Therefore, the data that enters this area is regarded as being at point D, and the result is output.

As described above, the complex input data 201,
By providing the complex plane degeneration circuit 403 at the front of 202, data errors due to noise or the like can be avoided.

[0020]

As described above, the present invention uses a simple logic circuit such as a comparator, a selector, an inverter, etc.
An excellent complex angle converter configured without using a circuit such as an OM can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of a complex angle converter according to a first embodiment of the present invention.

FIG. 2 is a detailed block diagram of the complex angle converter.

FIG. 3 is a conceptual diagram showing a region where an input complex signal of the complex angle converter exists.

FIG. 4 is a block diagram of a complex angle converter according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a conventional complex angle converter.

FIG. 6 is a detailed conceptual diagram of FIG. 3;

[Explanation of symbols]

 103, 203 Absolute value comparator 104, 204 Selector 105 Decoder 205 Multi-input bit inverter 206 Inverter 207 Exclusive OR gate 403 Complex plane degeneration circuit

Claims (2)

(57) [Claims] 1. An absolute value comparator for comparing magnitudes of absolute values of an in-phase signal and a quadrature signal, which are demodulated complex baseband signals of a digital angle-modulated wave, and the absolute value comparator based on a comparison result of the absolute value comparator. A set of bits other than the most significant bit MSB of the phase signal and the most significant bit MSB of the orthogonal signal, and a set of bits other than the most significant bit MSB of the orthogonal signal and the most significant bit MSB of the in-phase signal are switched and output. To determine in which quadrant the demodulated complex baseband signal is located from the most significant bit MSB of the in-phase signal and the most significant bit MSB of the quadrature signal, and determine from the selector the most significant bit of the in-phase signal. When a set of bits other than the MSB and the MSB of the quadrature signal is output, the MSB of the quadrature signal is output based on the MSB of the in-phase signal. It is determined whether or not bits other than the bit MSB are to be inverted, and bits other than the most significant bit MSB of the inverted / non-inverted quadrature signal are output as angle data on a complex plane. When a set of bits other than the most significant bit MSB of the quadrature signal and the most significant bit MSB of the in-phase signal is output, bits other than the most significant bit MSB of the in-phase signal are based on the most significant bit MSB of the quadrature signal. Is determined, and the most significant bit M of the inverted / non-inverted in-phase signal is determined.
A decoder that outputs bits other than SB as angle data on a complex plane. In front of wherein the absolute value comparator for receiving the demodulated complex baseband signal, the complex angle converter of claim 1 in which a complex plane compression circuit that maps a point in a certain region of the complex plane.