Phase feedback modulation driving circuit for reducing quantization noise of fiber-optic gyroscope

Abstract

The utility model provides a phase feedback modulation drive circuit for reducing quantization noise of a fiber-optic gyroscope, the circuit comprises a D / A converter module, a mutual impedance I / V conversion amplifier module and a reference voltage source VREF module, the D / A converter module comprises a D / A converter U1 and a D / A converter U2, the D / A converter U1 is connected with the mutual impedance I / V conversion amplifier module, and the D / A converter U2 is connected with the mutual impedance I / V conversion amplifier module. Differential current output ends IOUTO1 and IOUTB1 of the D / A converter U1 are respectively and correspondingly connected in parallel with differential current output ends IOUYA2 and IOUTB2 of the D / A converter U2, and current source output signals IOUTA and IOUTB are generated; the mutual impedance I / V conversion amplifier module comprises a differential mutual impedance I / V conversion amplifier U3, a resistor R2 and a resistor R6, the current source outputs signals IOUTA and IOUTB, and the signals IOUTA and IOUTB are connected with the input end of the differential mutual impedance I / V conversion amplifier U3 through the resistor R2 and the resistor R6.

Description

Technical Field

[0001] The utility model relates to the technical field of fiber optic gyroscopes, in particular to a phase feedback modulation driving circuit for reducing quantization noise of a fiber optic gyroscope. Background Art

[0002] Fiber optic gyroscopes have the advantages of small size, light weight, fast startup, high reliability and long life, and are therefore widely used in navigation and control systems.

[0003] Among the many performance indicators of a fiber optic gyroscope (FOG), the random walk coefficient (RWC) represents the magnitude of random noise in the FOG and is a key indicator of its accuracy. In a digital closed-loop FOG, random noise is primarily concentrated in the optical path system and the signal processing system that comprise the FOG.

[0004] The noise in the signal processing system primarily comes from the photodetector and preamplifier circuits at the signal demodulation end, and the phase feedback modulation circuit at the signal feedback control end. The phase feedback modulation circuit in a digital closed-loop fiber optic gyroscope typically consists of a high-speed, high-resolution D / A converter and a broadband differential op amp.

[0005] like Figure 1 The typical phase feedback modulation drive circuit in a fiber optic gyroscope (FOG) shown in Figure 1 consists of a high-speed, high-resolution D / A converter and a high-precision, wideband differential operational amplifier. The D / A converter converts the feedback modulation signal, generated by adding a digital staircase signal to a digital modulation signal, into an analog signal. The differential operational amplifier conditions and amplifies the signal and drives the Y-waveguide phase modulator.

[0006] The Y-waveguide phase modulator's functions are: first, to improve the gyro's detection sensitivity and scale factor linearity, it provides a stable and accurate phase bias operating point for the SAGNAC phase interferometer-based detection system through phase modulation. Second, it processes the phase shift signal from the photoelectric detection and demodulation system to generate a digital feedback step wave signal, which is quickly and accurately fed back to the fiber optic gyroscope's optical path via the Y-waveguide. It can be inferred that by improving the noise characteristics of the phase modulation drive circuit, the random walk and bias stability of the closed-loop fiber optic gyroscope can be effectively improved.

[0007] The D / A converter is the core component of the phase feedback modulation circuit and must meet two requirements:

[0008] First, high speed, wide bandwidth, and short settling time. If the settling time is long, the width of the transient peak in the detector's output signal will be widened, causing a high-frequency harmonic noise signal to be superimposed on the signal of the preamplifier circuit.

[0009] Second, high resolution and low quantization error. Resolution refers to the smallest analog quantity that can be distinguished during D / A conversion and is generally determined by the number of bits (N) in the D / A converter. Reducing the number of bits (N) in the D / A converter will increase the feedback system's blind spot for smaller feedback steps, leading to increased quantization noise in the D / A converter.

[0010] In a fiber optic gyroscope, the quantization noise caused by the D / A converter can be represented by a random walk of the detected phase:

[0011]

[0012] Where N is the number of bits of the D / A converter, f m is the modulation frequency, K SF The random walk formula shows that for every increase in the number of bits N of the D / A converter, its quantization noise is halved.

[0013] However, due to limitations in device manufacturing processes, when selecting a high-speed, high-resolution D / A converter, when the settling time meets the requirements (approximately 25 to 50 ns), the maximum resolution of a single D / A converter is restricted, generally only reaching around 14 bits. This is obviously not conducive to the high-precision gyroscope's need to reduce random noise.

[0014] It can be seen from this that how to improve the accuracy of the fiber optic gyroscope under the limited number of bits of a single D / A converter to reduce the quantization noise caused by the D / A converter. Utility Model Content

[0015] In order to solve the above technical problems, the utility model provides a phase feedback modulation drive circuit for reducing the quantization noise of a fiber optic gyroscope. The circuit includes a D / A converter module, a transimpedance I / V conversion amplifier module, and a reference voltage source VREF module, wherein:

[0016] The D / A converter module includes a D / A converter U1 and a D / A converter U2, wherein the differential current output terminal I OUTA1 , I OUTB1 The differential current output terminal I OUTA2 , I OUTB2 They are connected in parallel and generate a current source output signal I OUTA , I OUTB ;

[0017] The mutual impedance I / V conversion amplifier module includes a differential mutual impedance I / V conversion amplifier U3, a resistor R2 and a resistor R6, and the current source outputs a signal I OUTA , I OUTBIt is connected to the input end of the differential mutual impedance I / V conversion amplifier U3 via the resistor R2 and the resistor R6.

[0018] Furthermore, the circuit also includes a matching resistor pair RREFx2, one end of the matching resistor pair RREFx2 is connected to the reference voltage source VREF module, and the other end of the matching resistor pair RREFx2 is respectively connected to the IREF end of the D / A converter U1 and the IREF end of the D / A converter U2.

[0019] Furthermore, the circuit further includes an integrated optical device MIOC, and the output end of the differential mutual impedance I / V conversion amplifier U3 is connected to the integrated optical device MIOC via a matching resistor R3 and a matching resistor R7 respectively.

[0020] Furthermore, the matching resistor tracks the resistance value of RREFx2 with an accuracy of less than 10 ppm.

[0021] Furthermore, the reference voltage source VREF module includes a serial digital-to-analog converter U4, an operational amplifier U5, a resistor R12 and a resistor R13, wherein the output end of the serial digital-to-analog converter U4 is connected to the non-inverting input end of the operational amplifier U5 via the resistor R12 and the resistor R13.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The utility model uses two D / A converters directly in parallel, so that the phase modulation and phase feedback of the digital closed-loop fiber optic gyroscope can be divided into two channels in digital signal processing, and are applied to the two D / A converters respectively to realize analog addition, thereby improving the effective number of bits of the D / A converter at the signal feedback control end of the fiber optic gyroscope, reducing the requirement for higher resolution of a single high-speed D / A converter, and improving the accuracy of the fiber optic gyroscope. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a typical phase feedback modulation drive circuit diagram in existing fiber optic gyroscopes;

[0025] Figure 2 This is the overall circuit diagram of the utility model;

[0026] Figure 3 It is an enlarged view of the corresponding part A in the overall circuit diagram of the present utility model;

[0027] Figure 4 It is an enlarged view of the corresponding part B in the overall circuit diagram of the present utility model;

[0028] Figure 5 It is an enlarged view of the corresponding C part in the overall circuit diagram of the present utility model. DETAILED DESCRIPTION

[0029] In order to make the technical solution and technical effect of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments.

[0030] The utility model aims to provide a phase feedback modulation driving circuit for reducing the quantization noise of a fiber optic gyroscope, so as to expand the effective number of bits of a D / A converter and thus improve the accuracy of the fiber optic gyroscope.

[0031] The utility model adopts a dual D / A converter parallel scheme to increase the effective number of bits of the phase modulation drive circuit, that is, when two N-bit D / A converters are used in parallel, the effective number of bits of the phase modulation drive circuit can be increased to N+1 bits.

[0032] refer to Figure 2-5 ,The circuit mainly includes a D / A converter module, a mutual impedance I / V conversion amplifier module and a reference voltage source VREF module.

[0033] Furthermore, in the design of expanding the effective number of bits by implementing a dual D / A converter parallel scheme, it is necessary to solve the consistency problem of the two D / A converter devices, which is reflected in the complementary current output high-speed D / A converter. The main issues include the consistency of the D / A converter's digital-to-analog conversion accuracy and the consistency of the temperature characteristics of the D / A converter's output current.

[0034] refer to Figure 3 The D / A converter module includes a D / A converter U1 and a D / A converter U2. The differential current output terminal I OUTA1 , I OUTB1 The differential current output terminal I OUTA2 , I OUTB2 They are connected in parallel and generate a current source output signal I OUTA , I OUTB Because I OUTA and I OUTB The two not only complement each other in terms of function, but also maintain the same current output direction. Therefore, by directly superimposing the output current signals of the two D / A converters, the equivalent conversion bit number of the D / A converter in the phase modulation feedback system is increased from N to N+1.

[0035] refer to Figure 4 The mutual impedance I / V conversion amplifier module includes a differential mutual impedance I / V conversion amplifier U3, a resistor R2 and a resistor R6. Among them, the current source output signal I OUTA , IOUTB The current source output signal I is directly superimposed on the output current signals of the two D / A converters. OUTA , I OUTB The I / V conversion and amplification are performed by the differential drive circuit shared by the subsequent stage, which can essentially eliminate the conversion error caused by the inconsistency of the characteristic parameters of components such as the operational amplifier and its external resistors.

[0036] refer to Figure 5 The reference voltage source VREF module includes a serial DAC U4, an operational amplifier U5, a resistor R12, and a resistor R13. The output of the serial DAC U4 is connected to the non-inverting input of the operational amplifier U5 via the resistors R12 and R13.

[0037] The circuit also includes a multifunctional integrated optical device MIOC with a push-pull function. The output end of the differential mutual impedance I / V conversion amplifier U3 is connected to the integrated optical device MIOC via matching resistors R3 and R7 respectively.

[0038] Since the two D / A converters can share a common reference voltage, while the external resistors must be set independently, the only issue that needs to be addressed is the consistency of the performance parameters of the two external resistors, thereby ensuring that the accuracy and temperature coefficient (TCR) of the two reference current sources remain consistent.

[0039] To this end, the circuit also includes a matching resistor pair RREFx2, one end of which is connected to the reference voltage source VREF module, and the other end of which is connected to the IREF terminal of D / A converter U1 and D / A converter U2, respectively. The matching resistor pair RREFx2 can be manufactured using precision laser resistance trimming combined with a thin-film resistor process. The matching resistor pair RREFx2 is used to provide a reference current source for D / A converter U1 and D / A converter U2, respectively.

[0040] Since the matching resistor pair RREFx2 is made entirely of semiconductor thin film materials on the same ceramic substrate, which has a very small linear expansion coefficient and the two resistors are exposed to exactly the same ambient temperature, their temperature characteristics (TCR) can be highly consistent.

[0041] Furthermore, through precise laser resistance trimming, the matching resistor can track the resistance value of RREFx2 to within 10ppm.

[0042] Therefore, under the action of the same reference voltage, the error of the reference current source of the D / A converter U1 and the D / A converter U2 can be made ≤0.001%, which is much smaller than the error value of 0.006% corresponding to the least significant bit 1LSB of the 14-bit D / A converter. In other words, it can fully meet the accuracy requirements after the dual D / A converters are connected in parallel.

[0043] Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A phase feedback modulation drive circuit for reducing quantization noise of a fiber optic gyroscope, characterized in that: The circuit includes a D / A converter module, a transimpedance I / V conversion amplifier module, and a reference voltage source VREF module, wherein: The D / A converter module includes a D / A converter U1 and a D / A converter U2, wherein the differential current output terminal I OUTA1 , I OUTB1 The differential current output terminal I OUTA2 , I OUTB2 They are connected in parallel and generate a current source output signal I OUTA , I OUTB ; The mutual impedance I / V conversion amplifier module includes a differential mutual impedance I / V conversion amplifier U3, a resistor R2 and a resistor R6, and the current source outputs a signal I OUTA , I OUTB It is connected to the input end of the differential mutual impedance I / V conversion amplifier U3 via the resistor R2 and the resistor R6.

2. The phase feedback modulation driving circuit for reducing quantization noise of an optical fiber gyroscope according to claim 1, characterized in that: The circuit further includes a matching resistor pair RREFx2, one end of the matching resistor pair RREFx2 is connected to the reference voltage source VREF module, and the other end of the matching resistor pair RREFx2 is connected to the IREF end of the D / A converter U1 and the IREF end of the D / A converter U2.

3. The phase feedback modulation driving circuit for reducing quantization noise of an optical fiber gyroscope according to claim 2, characterized in that: The circuit further includes an integrated optical device MIOC, and the output end of the differential mutual impedance I / V conversion amplifier U3 is connected to the integrated optical device MIOC via a matching resistor R3 and a matching resistor R7 respectively.

4. The phase feedback modulation driving circuit for reducing quantization noise of an optical fiber gyroscope according to claim 2, characterized in that: The matching resistor tracks the resistance value of RREFx2 within an accuracy of 10ppm.

5. The phase feedback modulation driving circuit for reducing quantization noise of an optical fiber gyroscope according to claim 1, characterized in that: The reference voltage source VREF module includes a serial digital-to-analog converter U4, an operational amplifier U5, a resistor R12 and a resistor R13, wherein the output end of the serial digital-to-analog converter U4 is connected to the non-inverting input end of the operational amplifier U5 via the resistors R12 and R13.

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