JPH0241005A - Demodulation device - Google Patents

Abstract

PURPOSE:To increase the accuracy of a pulse width by constituting the demodulation device by a memory read by an address generated at a prescribed period in one period (T) of a reference signal S in phase with the signal S synchronously with the reference signal S and generating a pulse width corresponding to a cos or sin value using a timewise location of the T as a variable, and a switch switched by a pulse width. CONSTITUTION:An address generating means 9 generates an address signal 10 at a prescribed time interval in one period of a reference signal 6 synchronously with the reference signal 6 and in phase with the signal. A PROM 11 is read by the address signal 10 and generates a pulse (cos) 121 and a pulse (sin) 122 having a width corresponding to the cos or sin value using a timewise position in one period as a variable. Then a modulation input signal 1 is expressed in V=Kcos(omegat-phi), where K is a constant, omega is an angular velocity and phi is a phase, and the switch 31 obtains a switching period of 1/2Kcosphi and the switch 32 obtains a switching period of 1/2Ksinphi to obtain a pulse with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for demosulating a signal obtained by changing the phase of a carrier wave as a detected value.

[Prior Art] For example, an angular velocity sensor in which a rotating piezoelectric element or other sensing element senses an angular velocity vector or an acceleration vector in a plane perpendicular to its rotation axis, and the phase of the carrier wave changes, or an acceleration sensor signal is converted to a rotating coordinate. Used to transform from a system to a fixed coordinate system.

Conventionally, in order to demosulate this signal, a full-wave rectification demosimulator is used, and a reference signal is used for the carrier wave to determine its sign. FIG. 5 is a block diagram of a conventional full-wave rectification demosimulator. In FIG. 5, 1 is the modulation input signal, V=KCO6
It is expressed as (ωt-φ), where ω is the angular velocity of the sensing element, and φ is the angle that the detected vector makes with the fixed coordinate X-axis, which is proportional to the magnitude of the detected vector.

2 is an inverter for inverting the module input signal 1; 31;
．． Reference numeral 32 designates analog switches, each of which consists of a pair of switches, one of which is on and the other is off.

41 and 42 are low-pass filters, 51 and 52 are demodulated signals, and 6 is a reference signal consisting of a rectangular wave having an angular frequency ω equal to the angular frequency ω of the carrier wave of the input signal 1. 7 is a PLL or timing circuit which inputs the reference signal @6, shapes the waveform, and outputs a 0° reference signal 81 and a 90' reference signal 82. Here, the 0° reference signal 81 is a reference signal that has the same phase as the input signal when the input vector direction is the X-axis direction, and the 90' reference signal 82 has the same phase as the input signal when the input vector direction is the Y-axis direction. is the reference signal. Therefore, the phase difference between these signals is 90°.

Modulation input signal 1 is guided to low-pass filters 41 and 42 by analog switches 31 and 32, but when Oo or 90° reference signal 81 or 82 is high (HIGH), switches 311 and 321 are turned on and the input is not inverted. Signal 1 is low pass filter 41.4
2 connected to O.

Or, when the 90" reference signal 8 is LOW, the switches 311 and 321 are turned off, and the switches 312 and 322 are turned off.
is turned on, and input signal 1 inverted by inverter 2 is connected to low-pass filters 41 and 42. In this way, in the full-wave rectification type demosimulator, M single signal 81 or 8
The demosulation is performed by changing the polarity of the input signal 1 of V-Kcos (ω = 1 φ) at that time in accordance with the high or low level that changes every 20 half cycles. The relationship between the waveform after demosulation and φ is shown in FIG. By measuring the DC component of this signal waveform, the direction and magnitude of the vector can be determined. This demosulated signal is connected to a low-pass filter 4 in order to be supplied to a predetermined process.

[Problems to be Solved by the Invention] As mentioned above, the full-wave rectifier demosimulator uses the reference signal 8
Since the polarity of the input signal 1 is changed by 1 and 82, this is equivalent to multiplying the carrier wave by a rectangular wave having a value of ±1. Therefore, the demosulated signal is expressed as:

VX ”=s i gn (cosωt)XKcO5(
ω is one φ) VY ”=s i gn (s i nωt)XKC
O5 (ωt-φ) However, sign (f>= 1 f≧O-1f<O 8i has Jn (CO8ωt), S i has 7n (
When S i nωt) is expanded into a Fourier series, S i gn (cosωt) = (4/π) (cosωt − (1/3) cos3ωt+...) S i Qn (S i nωt> = (4/π) ( sinωt + (1/3) sin3ωt+・) Therefore, VX ′= (4/l Kcos (ωt−φ)x (
cosωt - (1/3) cos3ω is 10...) = (2/π) K [cosφ + cos (2ω is 1φ) - (1/3) (cos (4ωt-φ) 10cos (2
ωt+φ))+...]=(2/π)Kcosφ+(2/7r)K [cos (2ωt-φ)−(1
/3) (cos (4ω to 1φ) + cos (2ω to 1φ)) 10...ko VY' = (4/π) Kcos (ω to 1φ) x (s i nωt + (1/3) s i n3ωt+・)=(2/π)K
[Sinφ + s i n (2ω to 1 φ) + (1/3) (s i n (4ωt-φ) + s i
n (2ωt+φ))+...bow=(2/π))(si
nφ + (2/7r) K [s i n (2ωt−φ)
+ (1/3>(s i n (4ωt-φ)+s
i n (2ωt+φ)) +...C As shown above, when a square wave is Fourier expanded, it contains many harmonic components that are odd multiples of the fundamental frequency; therefore, it is demonstrated that the general transmission wave contains similar frequency components. There is a problem in that a DC shift occurs in the signal after demosulation, and the linearity between the sensor detection target and the voltage output signal after demosulation deteriorates.

Also, if the phase of the carrier wave is shifted by 90' from the reference signal as shown in Figure 6(C), the ripple included in the signal after demosulation is large, and it is necessary to use a low-pass filter to sufficiently reduce this ripple. However, there was a problem in that the frequency characteristics of the sensor were impaired.

[Means for Solving the Problems] The present invention provides a demodulation device that switches a modulation input signal whose phase has been changed with respect to a carrier wave in synchronization with a reference signal. an address generation circuit that generates address signals at predetermined time intervals within one cycle of a signal, and a cosine or It consists of a memory that generates a pulse with a width corresponding to the value of sin, and a switching means that performs switching based on the pulse width from the memory.

[Operation] In the address generation means, one period of the reference signal is divided into predetermined time intervals. Separated time t1゜t2. ...
For tn, address a'(, a2...an is generated. These addresses al, a2...an are sequentially sent to the memory at a predetermined time and the corresponding contents are read out. Cos and sin values whose variables are the time positions within the cycle, that is, the time positions divided by the address generation means, are written, and when they are sequentially read out using the addresses from the address generation means, the cos or sin values are stored.
It is output corresponding to the value of n. When the cos or sin signal output from this memory is integrated, it becomes cosωt, respectively.
It has a pulse width of Sinωt and turns the analog switch on and off. At this time, when the reference signal is high, the modulation input signal is switched, and when the reference signal is low, a signal obtained by inverting the modulation input signal is switched. In this way, by switching the modulation input signal at predetermined time intervals and at time intervals proportional to the cos and sin signals, a signal containing cos φ or sin φ is generated.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of an embodiment. Reference numeral 9 denotes address generation means, which generates address signals 10 in synchronization with the reference signal 6 and in the same phase at predetermined time intervals within one cycle of the reference signal.

11 is a FROM, which is read by an address 10 generated at a predetermined interval, and has a width corresponding to the value of cos or sin where the time position within one cycle is a variable; in other words, by integrating cosω and s Pulse (cos) 121 and pulse (sin>122) with a width of r nωt
occurs. Other symbols that are the same as those in FIG. 5 indicate similar parts.

First and second examples of the address generation means 9 are shown in detailed block diagrams in FIGS. 2 and 3(a), and FIG. 3(b)
The timing waveform diagram of FIG. 3(a) is shown in FIG. In FIG. 2, the address generation means 9 includes a phase comparator 91, a low-pass filter 92, a VCO 93, and a counter 94.
A signal whose phase is synchronized with the reference signal 6 is obtained, and the VCO 93 generates pulses at predetermined time intervals within one cycle of the reference signal @6. A counter 94 counts these pulses and outputs the count as an address signal 10. In FIG. 3(a), the address generation means 9 consists of a clock generator 95, a timing circuit 96, and a counter 94.
As shown in FIG. 3(b), the timing circuit 96 generates pulses at predetermined time intervals within one period of the reference signal 6 in phase synchronization with the reference signal 6. A counter 94 counts these pulses and outputs the count as an address signal 10.

In FROMll, CO3 and sin pulses 121 and 122 at the time position specified by the address signal 10
is output. In this way, a pulse with a predetermined width of cos or sin is applied to turn on and off the analog switches 31 and 32, but in the first half cycle of the reference signal 6, the first analog switches 311 and 321 are turned on and off. The second analog switch 32 is turned off, the modulation input signal 1 is connected to the low-pass filter 41.42, and in the second half period of the reference signal @6, the second analog switch 312, 322 is turned on, and the first analog Switches 311 and 321 are turned off, and the modulation input signal 1 inverted by inverter 2 is passed through low-pass filter 41.4.
Connect to 2.

By the way, the modulation input signal 1 is V=Kcos
It is expressed as (ωt-4). K is a constant, ω is the angular frequency of the carrier wave, and φ is the phase angle. On the other hand, since the angular frequency of the reference signal 6 is also the same ω, the cos
, sin signal 12 is also defined by ω. Since the analog switches 31 and 32 switch with pulse widths related to cosωt and sinωt, C05(
Regarding the switching of the analog switch 31 by JJt, VX = KOO3(c)i' -CO3(ωt-
φ) = (1/2)Kcosφ + (1/2)Kcos(2ωt-φ) Regarding the switching of the analog switch 32 by Slnωt, VY = Ks in(I)t -cos (ωt-φ
)=(1/2)Ks i nφ + (1/2)Ks i n (2ωt−φ),
(1/2>Kcosφ, (1/2)K·sinφ is obtained. This is the value in the fixed coordinate system (X, Y) of the detected value from, for example, a rotating angle sensor or acceleration sensor. Also, (1/2)Kcos (2ωt-φ>, (1/2)
2) Ksin (2ωt-φ) is a ripple, but since the frequency is twice that of the carrier wave, it can be easily smoothed by the low-pass filters 41 and 42. Furthermore, at this time,
The low-pass filters 41 and 42 may be constructed by connecting a notch filter that sharply attenuates at 2ω before an LC filter having low-pass characteristics.

[Effects of the Invention] As explained above, according to the present invention, the modulation input signal is switched using the pulse width read out from the memory, so it can be easily configured. Since it corresponds to the value, it has the advantage of being highly accurate and less affected by ripples.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
A block diagram of a first example of address generation means in the figure,
FIG. 3 is a diagram explaining a second example of the address generation means in FIG. 1, and FIG. 3(a) is a block diagram, and FIG.
b) is a timing waveform diagram, FIG. 4 is a waveform diagram of a signal output from the PROM of FIG. 1, FIG. 5 is a block diagram explaining the conventional technology, and FIG. 6 is a diagram of the analog switch 31 of FIG.
(32) is a waveform diagram illustrating the output. 1... Modulation input signal, 2... Inverter,
31.32...Analog switch, 41.42...
Low pass filter, 51.52...Output, 6...Reference signal, 9...Address generation means, 10...Address, 11...PROM. Figure 4 'yc72 Figure 2 Figure 'v36! I"t3 Seki (b) Spontaneous writing of procedural amendments) August 8, 1986 Commissioner of the Patent Office Furu 1) Moon Takeshi 2. Name of the invention Duration device 3. Relationship with the person making the amendment Patent application Address: 13-16 Mita 3-chome, Minato-ku, Tokyo Name:
Mitsubishi Precision Co., Ltd. Representative Hideo Ota 4 Address of agent 2-1-8-602 Sanno, Ota-ku, Tokyo 143 Attachment 6 Contents of amendment (1) Specification, page 10, line 19 to page 11 In the 5th line, "Turn off... of reference signal 6" to rco
s signal 121 or sin signal @122 is high (HIGtl
), switch 311 and 321 are turned on, switch 3
12, 322 and modulation input signal 1.
are connected to low-pass filters 41 and 42, and the cos signal 1
21 or sin signal 122 is low (LOW), switches 312 and 322 are turned on, switches 311 and 321
"Turn it off," he corrects. Above 6, the contents of the amendment

Claims (1)

[Claims] In a demodulation device that switches a modulation input signal whose phase has been changed with respect to a carrier wave in synchronization with a reference signal, the modulation input signal is switched within one period of the reference signal in synchronization with the reference signal and in the same phase. an address generation circuit that generates address signals at time intervals; and a width corresponding to a cos or sin value that is read by the addresses generated at the predetermined time intervals and whose variable is the time position within the one cycle. 1. A demodulation device comprising: a memory that generates a pulse; and switching means that performs switching according to the width of the pulse from the memory.