JP2002163599A - Square circuit and signal processing circuit using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a signal processing circuit, which is applied for a physical quantity sensor that has sensitivity in all directions, with good accuracy, a low-cost and simple design. SOLUTION: A pulse-length modulated rectangular wave, which corresponds to a quantity change that is a detected value of a physical quantity sensor 10, is adjusting amplified by quantity corresponds to a quantity change in amplitude of the wave. Subsequently, a switch 23 converts the wave into a product of the changes of pulse length and amplitude, and then outputs. The product corresponds to the square of a quantity change corresponding to a quantity change of the pulse-length modulated rectangular wave. In addition, each detected value in X and Y axes of the physical quantity sensor 10 is converted into a product as described above, and then all products are added by an adder 12 to calculate the sum of the squares. With this circuit design, a square value, which is an absolute value independent on direction of physical quantity, can be outputted. Therefore, a signal processing circuit, which is applied for a physical sensor that has sensitivity in all directions, can perform the above- described operations, and be provided with a low-cost and simple design.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for calculating the sum of squares of components of a vector quantity on a plurality of reference axes when a vector quantity (acceleration etc.) is input to a physical quantity sensor (acceleration sensor etc.) having a plurality of reference axes. Further, the present invention relates to a signal processing circuit for calculating the magnitude of the vector amount.

[0002]

2. Description of the Related Art Force sensors, pressure sensors, acceleration sensors,
In the case of a physical sensor having two orthogonal axes such as an angular acceleration sensor, a magnetic sensor, an optical sensor, and a pyroelectric sensor, when an absolute amount that does not depend on the direction of the physical quantity detected by the sensor is required, conventionally, the sum of squares of the two orthogonal axes is conventionally used. Although the square root was required, the circuit to realize it was expensive and complicated. Generally, a circuit for calculating the square root of the sum of squares is mainly composed of a square circuit and a circuit for finding the root. A square-sum-square circuit consisting of a square circuit and a circuit for finding the root is less susceptible to the environment,
Each requires well-matched transistor pairs. Therefore, the square root of sum of squares circuit is complicated and expensive.

For example, a circuit shown in FIG. 4 has been published as a root-sum-square circuit composed of an integrated circuit. FIG. 4 is a circuit diagram of the operational amplifier described in P327-P332 of “Operational Amplifier” published by McGraw-Hill in 1983. By setting V1 = V2 in FIG. 4, a squaring circuit can be formed. In the circuit of FIG. 4, the field effect transistors Q1 and Q2 need to have well-matched characteristics. In the example of FIG. 4, the maximum error is estimated to be 4.4% of the full scale. The root generation circuit for obtaining the root can be realized by a circuit that feeds back the output of the divider to the input. The total error in the root generation circuit having such a circuit configuration is expected to be about 10%.

As described above, the conventional root-sum-square circuit is
In addition to being a complicated circuit, accurate physical quantity measurement requires further adjustment of the circuit, and cannot be a simple and inexpensive configuration. As a method of calculating the square root of the sum of squares with a simple and inexpensive configuration, the method described in JP-B-58-34865 has been proposed. This root-sum-square calculation method focuses on the first quadrant (0 to 90 degrees) of two orthogonal axes and divides the angle into three equal parts (0 to 90 degrees).
Degrees, 30 degrees, and 60 degrees), and a correction process is performed on the sensor output at each angle. Specifically, in the range from 0 to 30 degrees, the sensor output in the 0-degree direction is applied. In the range from 60 degrees to 90 degrees, a 90-degree sensor output is applied. In the range from 30 degrees to 60 degrees, a value obtained by multiplying the sum of the sensor output in the 0-degree direction and the sensor output in the 90-degree direction by COS45 ° = 0.707 as a coefficient is applied. According to this method, the error is estimated to be 7.6%. In the disclosed invention, the distance is divided into three, but the error can be further reduced by increasing the angle of division. Further, the root-sum-square calculation method can be realized by a circuit having a relatively simple configuration and capable of operating without adjustment.

[0005]

[Problems to be Solved by the Invention] However, Japanese Patent Publication No. Sho 58
The method of -34865 focuses only on the first quadrant of two orthogonal axes. In order to realize a circuit that applies the method to the sensor output in the range of 0 to 360 degrees, it is necessary to provide an absolute value circuit for obtaining the absolute value of the sensor output of two orthogonal axes as a front circuit. Since an absolute value circuit is required as a pre-circuit, a root-sum-square calculation circuit that applies the method of Japanese Patent Publication No. 58-34865 in the range of 0 to 360 degrees cannot be realized with a simple configuration, and costs are reduced. Was difficult. The present invention has been made in view of the above problems, and is applied to a physical quantity sensor having sensitivity in a range of 0 to 360 degrees, and a vector quantity component detected on a plurality of axes of the physical quantity sensor. It is an object of the present invention to provide a signal processing circuit which can calculate the sum of squares of the above with a simple configuration and can be manufactured at low cost.

[0006]

The gist of the present invention to achieve the above object lies in the following inventions.

[1] The amount of change in the pulse width of the rectangular wave in the first rectangular wave signal having the repetition frequency f represents a certain amount A, and the first rectangular wave signal is processed. A squaring circuit that generates a square value signal representing ² ; a first averaging unit that generates a first average signal representing an average of the amplitude of the first rectangular wave signal; and the first average signal and the ground. A constant value such as a voltage is alternately selected in synchronization with the first rectangular wave signal, the amplitude is a value of a difference between the first average value and the constant value, and the pulse width is the first value. Selecting means for generating a second rectangular wave signal having a pulse width of the rectangular wave signal, and generating a second average signal representing an average of the amplitude of the second rectangular wave signal; A second averaging means for outputting a change amount as the square value signal.

[2] The first averaging means comprises: a first filter for inputting the first rectangular wave signal; and an amplifier for amplifying or attenuating an output of the first filter. The amplitude adjusting circuit for generating an average signal, wherein the second averaging means is a second filter that receives the second rectangular wave signal as an input. Square circuit.

[3] When an acceleration or other vector quantity is input, an n-axis which senses the component of the vector quantity on the n-axis (n is 2 or 3) orthogonal to each other and outputs each component of the n-axis In a signal processing circuit that receives each of the components of the n-axis from a sensor and generates a sum of squares of the components of the n-axis, the n squaring circuits according to the above [1] or [2], and the n squaring circuits An adder that adds the square signal that is the output of the circuit and outputs the sum as the square sum,
The n squaring circuits are provided corresponding to the n axes respectively, and each squaring circuit includes a pulse width modulator that generates the first rectangular wave signal, and each of the pulse width modulators A signal processing circuit for modulating a pulse width of the first rectangular wave signal in accordance with a component of the corresponding axis.

[4] A clock circuit for outputting a clock signal which is a rectangular wave signal is provided, and the pulse width modulator receives the clock signal and modulates a pulse width of the clock signal with a component of the corresponding axis. [3] wherein the first rectangular wave signal is generated by performing
3. The signal processing circuit according to claim 1.

[0011]

FIG. 1 is a block diagram showing a signal processing circuit according to an embodiment of the present invention. However, FIG. 1 includes a physical quantity sensor 10 to which this signal processing circuit is applied. The physical quantity sensor 10 is a capacitance detection type sensor such as an acceleration sensor, and uses orthogonal X and Y axes as sensing axes. Therefore, when a vector quantity such as acceleration is input to the physical quantity sensor 10, the physical quantity sensor 10 outputs an X-axis component x and a Y-axis component y of the vector quantity. The capacitance detection type sensor converts the X-axis component x and the Y-axis component y of the input vector amount into a change amount of the capacitance and outputs them as an X-axis sensor signal x and a Y-axis sensor signal y, respectively.

The X-axis sensor signal x is transmitted to a first pulse width modulator 20, and the Y-axis sensor signal is transmitted to a second pulse width modulator 30. First, a circuit for processing the X-axis sensor signal x will be described. The clock circuit 11 outputs a clock signal that is a rectangular wave to the first pulse width modulator 20 and the second pulse width modulator 30. The first pulse width modulator 20 synchronizes with the clock signal output from the clock circuit 11 and outputs a pulse width modulation signal whose pulse width is modulated according to the level of the X-axis sensor signal x output from the physical quantity sensor 10. Since the X-axis sensor signal x is a change in capacitance, the first pulse width modulator 20 generates a pulse width modulated signal by changing the pulse width of the input clock signal according to the change in the capacitance. The pulse width modulation signal is a rectangular wave, and corresponds to the above-described first rectangular wave signal. This pulse width modulation signal is a signal having a constant amplitude and a pulse width change amount corresponding to the X-axis sensor signal x.
Therefore, the average value of the pulse width modulation signal is proportional to the pulse width of the pulse width modulation signal. Therefore, the amount of change in the average value of the pulse width modulation signal corresponds to the X-axis sensor signal x (change in capacitance in the X-axis capacitance element of the physical quantity sensor 10).

The first filter 21 filters a component near the clock frequency of the input pulse width modulation signal,
A DC signal is generated by rectifying the pulse width modulation signal.
The amplitude of the DC signal represents the average value of the amplitude of the pulse width modulation signal. The first amplifier 22 includes a first filter 21
, Amplifies the level of the DC signal, and supplies the adjusted DC signal to the first switch 2.
Supply 3 The amplification of the level of the DC signal by the first amplifier 22 is performed by changing the level of the input DC signal to a level equal to the average value of the pulse width modulation signal output from the first pulse width modulator 20 and guided to the first switch 23. This is performed to adjust the level and supply the level-adjusted DC signal to the first switch 23. Therefore, the level of the DC signal output from the first amplifier 22 represents the X-axis sensor signal x. The circuit composed of the first filter 21 and the first amplifier 22 corresponds to the above-mentioned first averaging means.

Each time the level of the pulse width modulation signal transmitted from the first pulse width modulator 20 rises or falls, the first switch 23 changes the DC signal output from the first amplifier 22 and the ground voltage. Are alternately selected and output. Therefore, the output of the first switch 23 is a rectangular wave signal. The amplitude of this rectangular wave signal is the DC level output from the first amplifier 22. The pulse width of the rectangular wave signal is the pulse width of the pulse width modulation signal transmitted from the first pulse width modulator 20. Therefore, in the rectangular wave signal output from the first switch 23, both the amplitude and the pulse width represent the X-axis sensor signal x. The first switch 23 corresponds to the above-described first selecting means. The rectangular wave signal output from the first switch 23 corresponds to the above-described second rectangular wave signal. Third
The filter 24 filters a component near the clock frequency of the input rectangular wave signal and generates a DC signal obtained by rectifying the rectangular wave signal. The amount of change in the amplitude of the DC signal represents the average value of the rectangular wave signal input to the third filter 24. Then, the amplitude of variation of the direct current signal is representative of the square x ² of the X-axis sensor signal x.

Next, a processing circuit for the Y-axis sensor signal will be described. The processing circuit for the Y-axis sensor signal has basically the same configuration as the X-axis sensor signal processing circuit. The difference between the two processing circuits is that the signal to be processed is an X-axis sensor signal x in the X-axis sensor signal processing circuit, but a Y-axis sensor signal y in the Y-axis sensor signal processing circuit. Therefore, the second
In the rectangular wave signal output from the switch 33, the amplitude and the pulse width both represent the Y-axis sensor signal y. 4th
The DC signal output from the filter 34 is input to the adder 12. The output of the fourth filter 34 is a DC signal, and the amount of change in the amplitude of the DC signal represents the average value of the rectangular wave signal input to the fourth filter 34.
Then, the amplitude of variation of the direct current signal is representative of the square y ² of Y-axis sensor signal y.

The adder 12 calculates a square x ² of the X-axis sensor signal x.
Signal (output of the third filter 24) representing the amount of change
And the DC signal (the output of the fourth filter 34) representing the square y ² of the Y-axis sensor signal y by the amount of change, and sums the square sum x ^{2 of the} X-axis sensor signal x and the Y-axis sensor signal y. + to generate a y ^2. The operation of the circuit of FIG. 1 will now be described in detail with reference to FIG.

As described with reference to FIG. 1, the switching process is performed by the first switch 23 and the second switch 33,
The averaging process is performed on the rectangular wave signals output from these switches by the filter 24 and the fourth filter 34. By the switching process and the averaging process, the operation of obtaining the square of the change amount of the pulse width of the pulse modulated wave signal generated by each of the first pulse width modulator 20 and the second pulse width modulator 30 is shown in FIG. It will be described based on.

FIG. 2 is a timing chart of signals of respective parts in the circuit of FIG. 1 for processing the sensor signals x and y. Fig. 2-1
3 is a timing chart of a clock signal output from the clock circuit 11. FIG. The clock signal has a duty ratio of 50%
It is a rectangular wave signal, and its clock cycle is 1 μS.
The amplitude of the clock signal is 5 Vpp, and its low potential is the ground potential. FIG. 2-2 illustrates a sensor signal output from the physical quantity sensor 10 as a change in capacitance. Sensor signal x,
y is the change in capacitance. Here, instead of the sensor signal x,
The sensor signal x is represented by the change amount a of the capacitance. Similarly, the sensor signal y is represented by a change amount b of the capacitance instead of the sensor signal y.

In the X-axis sensor signal x and the Y-axis sensor signal y output from the physical quantity sensor 10, the change in the capacitance of the X-axis sensor is a [pF] and the change in the capacitance of the Y-axis sensor is b [pF].
And FIG. 2-2 shows that the X-axis sensor signal x has decreased from a reference capacitance of 50 [pF] by a [pF].

As described with reference to FIG. 1, the X axis and the Y axis
The processing of the sensor signal of the axis is the same up to the adder 12, so the processing of the sensor signal x of the X axis will be described in the following figures (from FIG. 2-3 to FIG. 2-7). Fig. 2-3
As shown in (1), the first pulse width modulator 20 has a time width α corresponding to the capacitance change amount a [pF], which is the output of the physical quantity sensor 10, according to the pulse width modulation characteristics of the first pulse width modulator 20. Only the pulse width modulation signal in which the pulse width of the clock signal is changed is generated. In FIG. 2-3, the rising edge and the falling edge of the rectangular wave that is the clock signal have α /
A pulse width modulation signal having a pulse width narrower by α time than the clock signal is generated by giving a change for two hours. Since the first filter 21 outputs the average of the amplitude of the pulse width modulation signal as a DC signal, the level of the DC signal decreases by a value proportional to α. The level of the DC signal output from the first filter 21 is a value slightly lower than 1/2 of 5 Vdc when the duty ratio of the input pulse width modulation signal is 50%.

FIG. 2D shows the degree of amplification by the first amplifier 22. The operation of the first amplifier 22 has been described with reference to FIG. First amplifier 22
Is the average voltage (5 Vdc) of the pulse width modulated signal from the first pulse width modulator 20 branched and input to the first switch 23.
１ ／) of the first filter 2
Amplify the DC signal at the output of No. 1. In the pulse width modulation signal from the first pulse width modulator 20, the pulse widths of the continuous rectangular waves are all reduced by α. Considering the area of the ON region of the pulse width modulation signal that is a rectangular wave,
It can be seen that the pulse width modulation signal output from the pulse width modulator 20 has a value reduced by [alpha] from 1/2 (reference voltage) of the average voltage 5 Vdc. Accordingly, FIG. 2-4 shows that the amplification effect of the first amplifier 22 is from α of Ｖ of 5 Vdc to α.
This indicates that the value has been adjusted to a reduced value.

FIG. 2-5 shows a rectangular wave signal output by the switching process in the first switch 23. That is,
A pulse width modulation signal having a pulse width narrower by α than the clock signal is input from the first pulse width modulator 20, and a switching process timing in the first switch 23 is given. Further, a DC signal reduced by α from the reference voltage of 5 Vdc is input to the first switch 23 from the first amplifier 22. When the switching process is performed at the above timing in response to these signal inputs, a rectangular wave signal whose pulse width and height are reduced by α in FIG. 2-5 is generated and output. Considering the change amount of the pulse width and the amplitude of the rectangular wave signal, the average level of the rectangular wave signal output from the first switch 23 is equal to the average level of the pulse modulated signal transmitted from the first pulse width modulator 20. This corresponds to the square of the pulse width change amount α.

FIG. 2-6 shows the level of the DC signal obtained by filtering the rectangular wave signal transmitted from the first switch 23 by the third filter 24 (the rectangular wave signal output from the first switch 23). represents the average level of) is a voltage value 5Vdc-alpha ^2.

In the processing of the Y-axis sensor signal, if the voltage change amount is β with respect to the capacitance change amount b [pF] output from the physical quantity sensor 10 in the second pulse width modulator 30, the process is performed in the same manner, the level 5Vdc-beta ² of the DC signal is to be outputted to the adder 12 in the fourth filter 34. FIG.
Is the value obtained by adding the DC signals related to the X axis and the Y axis.
Vdc- (α ² + β ² ) is output. However, since the adder 12 is a logic circuit made of a semiconductor integrated circuit, the addition in the adder 12 is performed on the changes α ² and β ² from the fixed value 5 Vdc component at the input. Also, due to the characteristics of this logic circuit, the output of the adder 12 is also a fixed value of 5 Vd
The level is obtained by subtracting the change (α ² + β ² ) from c. An added value can be obtained as a change in the output of the adder 12.

By the above signal processing, the sensor outputs of the two orthogonal axes are converted into the square value of the absolute quantity independent of the direction of the physical quantity α ² + β ² . In the following processing, the square value may be used, or a square root circuit may be added to obtain the root 根 (α ² +
β ² ) can also be used. In FIG. 1, the square value of the sensor output of the two orthogonal axes is processed by an adder through a filter. However, the processing shown in FIG. The square value of the absolute quantity independent of the direction of the physical quantity can be obtained as in the case of the embodiment. Further, when the sensor outputs of the two orthogonal axes of the capacitance detection type physical quantity sensor are output as pulse width modulation values,
The square value of the output of each axis of the original physical quantity sensor can be obtained by turning on / off the pulse width modulation outputs of the physical quantity sensor on the X axis and the Y axis and the output obtained by averaging these outputs using a switch. This value is processed by the filter described with reference to FIG. 1 and added by the adder to obtain the sum of squares of the absolute quantity independent of the direction of the physical quantity. According to this configuration, since it is not a configuration for converting into a voltage signal as shown in FIG. 1, the number of elements, which is an error factor, can be reduced, and an error of about 2% as a total error of the switch and the adder is required. It turns out that. The processing configuration for converting the sensor output into the square value described above is not limited to the orthogonal two-axis physical quantity sensor, but can be applied to the orthogonal three-axis physical quantity sensor. A configuration may be adopted in which each of the outputs of the three axes is processed and converted into the square value of the sensor output, and the adder calculates the sum of squares for the three axes.

FIG. 3 is a circuit diagram showing the configuration of FIG. 1 using more specific elements. The physical quantity sensor 10 of FIG.
It is assumed that a two-axis capacitance detection type accelerometer 100 is used. 2-axis capacitance detection type accelerometer 10
The capacitances of the X-axis and the Y-axis, which are two orthogonal axes of 0, have two outputs as a differential capacitance (unit: pF) that increases and decreases with a change in the respective acceleration. Further, a first exclusive OR element section 200 and a second exclusive OR element section 300 are provided as equivalent to the first pulse width modulator 20 and the second pulse width modulator 30.

The flow of processing and conversion of the X-axis sensor output of the two-axis capacitance detection type accelerometer 100 will be described. First, the internal configuration of the first exclusive OR element unit 200 will be described. The rectangular wave output from the clock circuit 11 is branched and input to the first exclusive OR element unit 200. Two positive and negative X-axis sensor outputs are respectively joined to the respective signal lines extending from the parallel resistor 201, and are connected to the exclusive OR element 202. With this configuration, the rectangular wave output of the clock circuit 11 has its pulse width modulated by the sensor capacitance of the two-axis capacitance detection type accelerometer 100 and the parallel resistor 201, and further subjected to an exclusive OR element 202 as a first filtering as a charge / discharge waveform. The signal is branched and output to the switch 210 and the first switch 230.

The first filter 210 specifically represents the first filter 21 of FIG. 1 and includes a resistor 211 and a ground capacitor 212. The operation is the same as that of the first filter 21, and the rectangular wave is filtered and converted into a DC voltage signal.
The signal is transmitted to the first amplifier 22. The first amplifier 22 adjusts and amplifies the DC signal from the first filter 210 so as to be equal to the average voltage of the voltage signal input to the first switch 230, and inputs the DC signal to the first switch 230. . The first switch 230 is a C-MOS transistor. The first pulse width modulator 2 is switched by the switching operation described with reference to FIG.
A DC signal corresponding to the square of the voltage signal output from 00 is generated and output to the second filter 240. The second filter 240 is a specific example of the third filter 24 shown in FIG. 1 and includes a resistor 241 and a ground capacitor 242. The operation is the same as that of the third filter 24, in which the rectangular wave is filtered, converted into a DC signal again, and transmitted to the adder 12. The flow of process conversion of the Y-axis sensor output of the two-axis capacitance detection type accelerometer 100 is exactly the same as the flow of the X-axis process described above. The squared voltage signal transmitted from the second filter 240 and the squared voltage signal transmitted from the fourth filter 340 are both transmitted to the adder 12 and added together in the direction of acceleration. It is possible to obtain the sum of squares of the absolute values of acceleration independent of each other.

[0029]

As described in the above embodiment, the present invention modulates a pulse width modulator by a detection value of a physical quantity sensor, generates a rectangular wave pulse width modulation signal, and generates a rectangular wave pulse width. The detected value of the physical quantity sensor is represented by expressing the detected value by the change of Has gained the square of Further, a process of converting each of the detection values of the physical quantity sensor along the plurality of reference axes into the above-described product is performed, and finally all the products are added by an adder to calculate a sum of squares. With this configuration, a signal processing circuit applied to a physical quantity sensor that can output a square value of an absolute quantity independent of the direction of a physical quantity and has a sensitivity in a range of 0 to 360 degrees is provided. It is possible to provide a signal processing circuit which is inexpensive and has a simple configuration and performs high-precision calculations.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a signal processing circuit including a physical quantity sensor according to an embodiment of the present invention.

FIG. 2 is a timing chart when processing a sensor signal in the configuration of FIG. 1;

FIG. 3 is a circuit configuration diagram showing the configuration of FIG. 1 with more specific elements.

4 is an example of a conventional squaring circuit. P327-P33 of "Operational Amplifier" published in 1983 by McGraw-Hill Company.
FIG. 3 is a circuit diagram of the operational amplifier described in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Physical quantity sensor 11 ... Clock circuit 12 ... Adder 20 ... First pulse width modulator 21 ... First filter 22 ... First amplifier 23 ... First switch 24 ... Third filter 30 ... Second pulse width modulator 30 Second pulse width modulator 31 Second filter 32 Second amplifier 33 Second switch 34 Fourth filter 100 Biaxial capacitance detection type Accelerometer 200: first exclusive-OR element 201: parallel resistor 202: exclusive-OR element 210: first filter 211: resistor 212: ground capacitor 230: first switch 240: second Filter 241, resistor 242, ground capacitor 300, second exclusive OR element 301, parallel resistor 302, exclusive OR element 310, second filter 311, resistor 312, ground capacitor 330, second Switch 340: fourth filter 341: resistor 342: ground capacitor

Claims (4)

[Claims] 1. A method according to claim 1, wherein the amount of change in the pulse width of the rectangular wave in the first rectangular wave signal having the repetition frequency f represents a certain amount A, the first rectangular wave signal is processed, and the square value A ^{2 of the} amount A A first averaging means for generating a first average signal representing an average of the amplitude of the first rectangular wave signal; and a first average signal and a ground voltage. And a constant value such as the first rectangular wave signal are alternately selected in synchronization with the first rectangular wave signal, the amplitude is the value of the difference between the first average value and the constant value, and the pulse width is the first rectangular wave signal. Selecting means for generating a second rectangular wave signal that is the pulse width of the wave signal; generating a second average signal representing an average of the amplitude of the second rectangular wave signal; and changing the second average signal. A second averaging means for outputting a quantity as the square value signal. 2. The first averaging means includes: a first filter for inputting the first rectangular wave signal; and an amplifier for amplifying or attenuating an output of the first filter. The squaring circuit according to claim 1, wherein the second averaging means is a second filter that receives the second rectangular wave signal as an input. . 3. An n-axis sensor which senses components of the vector quantity on the n-axis (n is 2 or 3) orthogonal to each other and outputs each component of the n-axis when an acceleration or other vector quantity is input. A signal processing circuit that receives the components of the n-axis from each other and generates a sum of squares of the components of the n-axis, wherein the n squaring circuits according to claim 1 and 2, and the outputs of the n squaring circuits An adder that adds the square signal and outputs the sum as the square sum, wherein the n square circuits are provided corresponding to the n axes, respectively, and each square circuit is the first rectangle. A signal processing circuit comprising: a pulse width modulator that generates a wave signal; wherein each of the pulse width modulators modulates a pulse width of the first rectangular wave signal according to a component of the corresponding axis. . 4. A clock circuit for outputting a clock signal that is a square wave signal, wherein the pulse width modulator receives the clock signal and modulates a pulse width of the clock signal with a component of the corresponding axis. 4. The signal processing circuit according to claim 3, wherein the first rectangular wave signal is generated.