JPH0736286Y2 - Temperature compensated demodulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a device for demodulating a signal obtained by changing the phase of a carrier wave with a detected value.

[Prior Art] For example, a sensing element such as a rotating piezoelectric element senses an angular velocity vector or an acceleration vector in a plane perpendicular to its rotation axis to change the phase of a carrier wave, and the signals of the angular velocity sensor and the acceleration sensor are used as rotational coordinates. Used to convert from a system to a fixed coordinate system.

Conventionally, in order to demodulate this signal, a full-wave rectification demodulator is used, and the reference signal is used for the carrier wave to determine the code. FIG. 2 is a block diagram of a conventional full-wave rectification demodulator. In FIG. 2, MS is a modulation input signal, and V = Kcos
It is represented by (ωt−φ), 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. INV is an inverter that inverts the modulation input signal MS, and S1 and S2 are analog switches, each of which consists of a pair of switches, and when one is on, the other is off. LPF1 and LPF2 are low-pass filters, DM1 and DM2 are demodulated signals, and NS is a reference signal, which is a rectangular wave with an angular frequency ω equal to the angular frequency ω of the carrier wave of the input signal MS. The PLL inputs the reference signal NS and outputs a 0 ° reference signal P1 and a 90 ° reference signal P2.

The modulation input signal MS is the analog switch S1 and
Although it is guided to the low pass filters LPF1 and LPF2 by S2, the 0 ° or 90 ° reference signal P1 or P2 is high (HIGH).
The input signals MS that are turned on when S11 and S21 are not turned on are directly connected to the low pass filters LPF1 and LPF2, and the switches S11 and S21 are turned off when the 0 ° or 90 ° reference signal P2 is low (LOW), S12 and S22 are turned on, and the input signal MS inverted by the inverter INV is connected to the low pass filters LPF1 and LPF2. As described above, in the full-wave rectification demodulator, V = Kcos at that time according to high or low that changes every half cycle of the reference signal P1 or P2.
Demodulation is performed by changing the polarity of the input signal MS of (ωt−φ). The relationship between the waveform after this demodulation and φ is shown in FIG. By measuring the DC component of this signal waveform, the direction and magnitude of the vector can be known. Connect this demodulated signal to the low-pass filters LPF1 and LPF2, and
The / D converter CON performs A / D conversion and sends it to the control processing device CPU.

[Problems to be Solved by the Invention] As described above, the full-wave rectifier demodulator has the reference signal NS.
The input signal MS is switched by the analog switches S1 and S2, and the demodulated signal is obtained through the low-pass filters LPF1 and LPF2.Therefore, the fluctuation of the offset voltage due to the fluctuation of the switching speed of the analog switch and the offset voltage due to the drift of the analog IC There was a problem that there was a large fluctuation. Further, A / D conversion is performed in order to digitally process the obtained data, but there is a problem that the error increases at this time.

[Means for Solving the Problems] A temperature-compensated demodulator according to the present invention comprises an A / D converter for analog-digital conversion of a modulation input signal whose phase is changed with respect to a carrier and temperature information, and the A
A data calibration unit consisting of a memory for reading digital format calibration data using the temperature information from the / D converter as an address, a digital phase synchronization circuit that synchronizes the phase with a reference signal of the same cycle as the carrier wave, and the output of the phase synchronization circuit. Cos or sin generating means for generating a digital signal of a cos or sin signal temperature-corrected by the output of the calibration data section, and the A /
Digital conversion signal of modulation input signal from D converter and digital cos or sin from cos or sin generating means
The digital multiplication means performs multiplication with a signal, the digital filter that passes the low frequency component of the multiplication output from the digital multiplication means, and the means for calibrating the output of the digital filter with the calibration data from the data configuration unit. Configured by

[Operation] The phase φ of the modulation input signal changes according to the direction of the detection vector, and its amplitude is modulated according to the size of the detection vector. This modulation signal and the temperature information from the sensor are input to the A / D converter.
This input signal is converted into a digital signal by an A / D converter by sampling at appropriate intervals. On the other hand, the reference signal having the same frequency as the carrier wave is phase-synchronized to divide one cycle of the reference signal with a predetermined time interval, and the co
The value of s or sin is output as a digital value from the cos or sin generating means. At this time, the time position of the predetermined time interval is temperature-corrected by the temperature information converted by the A / D converter. The A / D-converted modulation input signal and the digital cos or sin signal are multiplied by the multiplying means. The outputs of these multiplications can be passed through a digital low-pass filter, and the temperature-corrected cosφ or sinφ can be obtained from the output from the calibration data section.

[Embodiment] An embodiment of a temperature compensation demodulator according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a functional block diagram of the embodiment. 1a and 1b are, for example, an angular velocity sensor installed on a rotating body, a modulation input signal of an angular frequency ω of a carrier wave from an acceleration sensor, and 2a and 2b are a low-pass filter for anti-aliasing and a high-pass filter for cutting a DC component. The pre-stage filters 3a and 3b consisting of are rotation reference signals of the rotating body on which the sensors are installed, and are rectangular waves that regulate the angular frequency ω and the phase φ of the carrier wave. Four
Is an A / D converter, and 5 is a cos or sin generating means, which is composed of a PROM and outputs the value of cos or sin corresponding to the time position within one cycle of the reference signals 3a and 3b in digital form. Reference numeral 6 is a digital signal processor, which is a digital PLL 61 for phase synchronization of the cos or sin generating means 5, an A / D converter 4 and a co.
From multiplying means 621 and 622 for multiplying the digital outputs of the s or sin generating means 5, digital low-pass filters 631 and 632 for removing high frequency components of the outputs of the multiplying means 621 and 622, and adders 641, 642 and 643 as data calibrating means. Become. Reference numeral 7 is a control processing device for using the demodulation signal obtained by the digital signal processor 6 for other control and the like, and 8a and 8b are temperature information of the sensor. Reference numeral 9 denotes a calibration data section, which is configured by a PROM, stores necessary calibration information in advance based on temperature information of the sensor, and reads out by an address from the A / D converter 4 corresponding to each temperature,
Output configuration data in digital format.

The digital PLL 61 obtains a signal that is phase-synchronized with the reference signals 3a and 3b, generates a pulse by timing one cycle of the reference signals 3a and 3b at a predetermined interval. This pulse is calibrated by adding the calibration data read from the calibration data section 9 by the adder 641, and the result is used as an address, cos.
Alternatively, the memory contents are read from the PROM of the sin generating means 5.
The memory contents store the values of cos and sin corresponding to the angle at intervals of a predetermined angle for one cycle (2π).

In the multiplying means 621 and 622 of the digital signal processor 6, the digital signal read from the PROM of the cos or sin generating means 5 is multiplied by the digital signal obtained by A / D converting the modulation input signals 1a and 1b.

By the way, the modulation input signal 1 is expressed as V = Kcos (ωt−φ). K is a constant, ω is the angular frequency of the carrier, and φ is the phase angle. The multiplication in the multiplication means 621 is c from the PROM.
For osωt, VX = Kcosωt · cos (ωt−φ) = (1/2) Kcosφ + (1/2) Kcos (2ωt−φ) For multiplication of sinωt in the multiplication means 622, VY = Ksinωt · cos (ωt−φ) ) = (1/2) Ksinφ + (1/2) Ksin (2ωt−φ), and (1/2) Kcosφ, (1/2) K · sinφ are obtained. This is a value in the fixed coordinate system (X, Y) of the detection value from the rotating angle sensor or the acceleration sensor, for example. Also, (1/2) Kcos (2ωt−φ), (1/2) sin (2ωt
−φ) can be easily smoothed by the digital filters 631 and 632. After the digital filtering, the calibration coefficient is read from the calibration data section 9 based on the temperature information converted into the digital signal by the A / D converter 4, and the data is calibrated by adding them by the adders 642 and 643 to perform the control processing. To the device 7.

[Advantage of Device] As described above, according to the present invention, an analog input signal is converted into a digital signal at an early stage, and signal processing is performed digitally. The influence of temperature on the output of the phase locked loop circuit and the output of the digital filter is calibrated with the same digital data from the memory, so the data for temperature correction does not vary and is the same. As described above, it has an advantage that it can be easily calibrated and a highly accurate device can be obtained with a relatively simple device. or,
Since a digital signal can be directly obtained, there is an advantage that accuracy does not deteriorate due to A / D conversion.

[Brief description of drawings]

FIG. 1 is a functional block diagram of an embodiment of a temperature compensation demodulator according to the present invention, FIG. 2 is a block diagram for explaining a conventional technique, and FIG. 3 is an analog switch S1 (S of FIG. 2).
It is a waveform diagram explaining the output of 2). 1a, 1b …… Modulation input signal, 2a, 2b …… Pre-stage filter, 3a, 3b …… Rotation reference signal, 4 …… A / D converter, 5
...... Cos or sin generating means, 6 ... Digital signal processor, 621,622 ... Multiplication means, 631,632 ... Digital filter, 7 ... Control processing device, 9 ... Calibration data section.

Claims (1)

[Scope of utility model registration request] 1. A modulation input signal whose phase is changed with respect to a carrier wave and an A / D converter for analog / digital conversion of temperature information, and digital calibration data using temperature information from the A / D converter as an address. A data calibration unit consisting of a memory for reading out, a digital phase synchronization circuit that is in phase synchronization with a reference signal having the same period as the carrier wave, and a cos or sin signal whose temperature is corrected by the output of the phase synchronization circuit and the calibration data unit output. Cos or sin generating means for generating a digital signal, a digital conversion signal of the modulation input signal from the A / D converter and a digital cos from the cos or sin generating means
Or a digital multiplication means for multiplying with a sin signal, a digital filter that passes a low frequency component of the multiplication output from the digital multiplication means, and means for calibrating the output of the digital filter with the calibration data from the data calibration unit. A temperature compensating demodulator comprising: