An IQ signal processing module for a laser interferometer system

Abstract

The present invention provides an IQ signal processing module for a laser interferometer system, involving signal demodulation technology. The module comprises three components: a local oscillator signal generation and distribution circuit, an IQ quadrature signal demodulation circuit, and a DC LDO voltage regulator. The local oscillator signal generation and distribution circuit comprises an active crystal oscillator network, a frequency multiplier, a low-noise amplifier A, a low-noise amplifier B, a low-noise amplifier C, a 1 / 2 power splitter, and a 1 / 3 power splitter, enabling the generation, frequency multiplication, amplification, and distribution of the module's 110MHz local oscillator original signal. The IQ quadrature signal demodulation circuit comprises a low-noise amplifier D, a low-pass filter, a balun transformer, a differential demodulator, an operational amplifier, and a filtering network, enabling the amplification, filtering, demodulation, and differential operation of the IQ quadrature signals within the module. The DC LDO voltage regulator comprises a linear LDO and its peripheral circuits, providing a suitable power supply for each functional chip in the module. The present invention simplifies the signal chain structure, reduces the number of photodetectors used in a multi-channel interferometer system, and saves manufacturing costs.

Description

Technical Field

[0001] The present invention relates to a signal demodulation technology, and in particular to an IQ signal processing module of a laser interference system. Background Art

[0002] Plasma density is a very important physical quantity in plasma physics research. Plasma density diagnosis is achieved indirectly by measuring the laser phase, which is based on the physical relationship between the phase of the laser and the refractive index of the path material during its transmission in the plasma. The conventional method is to calibrate the phase of the intermediate frequency signal of the reference channel and the detection channel using instruments such as a phase difference meter, calculate the difference between the two, and perform phase-density inversion to obtain the plasma density data in the fusion device. This method has a complex optical path structure, and the density information of a diagnostic channel needs to be obtained through the combination of two photodetectors. Due to the non-correlation between the two photodetectors, key indicators such as noise suppression and bandwidth are not ideal. Summary of the Invention

[0003] To address these issues, a novel IQ signal processing module for a laser interferometer system was proposed. Direct photoelectric detection of the beat frequency between the reference and detection channels generates an RF signal containing phase variation information. This signal is then orthogonally demodulated with the system's LO local oscillator (LO) signal. Cotangent or tangent calculations are performed on the zero-IF I and Q signals to determine the time-varying phase variation, thereby retrieving plasma density information within the time-varying range. This method utilizes only a single photodetector in any diagnostic optical path, significantly improving key performance indicators such as phase resolution, noise suppression, bandwidth, and response time.

[0004] The present invention proposes an IQ signal processing module for a laser interferometer system, comprising three parts: a local oscillator signal generation and distribution circuit, an IQ quadrature signal demodulation circuit, and a DC LDO voltage regulator. The local oscillator signal generation and distribution circuit comprises an active crystal oscillator network, a frequency multiplier, a low-noise amplifier A, a low-noise amplifier B, a low-noise amplifier C, a 1 / 2 power splitter A, a 1 / 2 power splitter B, and a 1 / 3 power splitter, and implements the generation, frequency multiplication, amplification, and distribution of a 110 MHz original local oscillator signal in the module. The IQ quadrature signal demodulation circuit comprises a low-noise amplifier D, a low-pass filter, a balun transformer, a differential demodulator, an operational amplifier, and a filter network, and implements the amplification, filtering, demodulation, and differential operation of the IQ quadrature signals in the module. The DC LDO voltage regulator comprises a linear LDO and its peripheral circuits, and provides a suitable power supply for each functional chip in the module.

[0005] The active crystal oscillator network outputs a 110MHz original local oscillator signal; the 1 / 2 power splitter A receives the original local oscillator signal output by the active crystal oscillator network and splits the power into two paths. One path is gain-amplified by the low-noise amplifier A and used as the modulation signal of the laser interference system and output to the diagnostic channel optical carrier; the other path is gain-amplified by the low-noise amplifier B and output to the 1 / 2 power splitter B; the 1 / 2 power splitter B again splits the power of the amplified local oscillator signal into two paths, one of which is transmitted to the frequency multiplier, and the other is used as the backup output of the local oscillator signal of the entire module; the frequency multiplier doubles the spectrum of the local oscillator signal with a frequency of 110MHz and outputs a 220MHz local oscillator signal; the frequency-multiplied local oscillator signal is gain-amplified by the low-noise amplifier C and then passes through the 1 / 3 power splitter in sequence. The 1 / 2 power divider realizes the six-way power equalization of the LO local oscillator signal after doubling the frequency, and distributes it to the local oscillator input end of the IQ orthogonal signal demodulation circuit; the RF signal containing plasma density information is amplified by the low-noise amplifier D gain, and then filtered out by the low-pass filter; the balun transformer performs differential conversion on the input RF signal; the differentially converted RF signal and the frequency-doubled local oscillator signal enter the corresponding port of the differential demodulator, and the differential demodulator outputs the orthogonal zero intermediate frequency and second harmonic signal; the operational amplifier and filtering network realizes the differential to single-ended conversion of the intermediate frequency signal, appropriately amplifies the power and filters out the second harmonic signal, and matches the output port impedance; the DC LDO voltage regulator source and its peripheral circuit realize DC-DC voltage conversion output, and power all components of the entire IQ processing module.

[0006] The present invention has the following beneficial effects:

[0007] The IQ signal processing module of this invention can demodulate the phase of the input RF signal, determining the phase change per unit time. It is suitable for use in IQ mode time-resolved diagnostic systems for fusion device plasma density using laser interferometry. Compared to traditional plasma density laser interferometers, this system simplifies the signal chain structure, reduces photodetector costs, and improves key performance indicators for input RF signal demodulation, such as noise suppression, bandwidth, and response time. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is the IQ signal processing module structure of the laser interferometer system;

[0009] Figure 2 This is the structure diagram of the DC LDO voltage regulator. DETAILED DESCRIPTION

[0010] In order to make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other. To achieve the above-mentioned objectives, the present invention adopts the following technical solutions.

[0011] like Figure 1 The figure shows the IQ signal processing module structure of a laser interferometer system. The IQ signal processing module includes three parts: local oscillator signal generation and distribution circuit, IQ orthogonal signal demodulation circuit, and DC LDO voltage regulator. They are distinguished based on their functions and signal flow.

[0012] Figure 1 The local oscillator signal generation and distribution circuit in the laser interferometer system consists of an active crystal oscillator network, a frequency multiplier, a low-noise amplifier A, a low-noise amplifier B, a low-noise amplifier C, a 1 / 2 power splitter A, a 1 / 2 power splitter B, and a 1 / 3 power splitter. The active crystal oscillator network outputs a stable oscillation signal as the original local oscillator LO signal for the entire laser interferometer system, with a frequency of 110MHz and a phase noise of less than -124dBc / Hz@1KHz. The frequency multiplier chip multiplies the LO signal to 220MHz to meet the LO frequency requirements of the IQ quadrature demodulation circuit. The 1 / 2 power splitter A receives the original LO signal output from the active crystal oscillator network and divides the power into two paths. One path is amplified by a low-noise amplifier A with a gain of 20dB and then used as the laser interferometer system modulation signal, which is modulated onto the diagnostic channel optical carrier. The other path is amplified by a low-noise amplifier B is amplified with a gain of 20dB and then output to 1 / 2 power divider B; 1 / 2 power divider B divides the amplified LO signal into two paths, one of which is transmitted to the frequency multiplier, and the other is used as a backup output for the LO signal of the entire module; the frequency multiplier doubles the LO signal with a frequency of 110MHz and outputs a 220MHz LO signal; the multiplied LO signal is amplified by low-noise amplifier C with a gain of 15dB, and then passes through the 1 / 3 power divider and the 1 / 2 power divider in sequence to achieve six-path power equalization of the doubled LO signal, which can be distributed to the LO input end of the IQ orthogonal signal demodulation circuit.

[0013] Figure 1The IQ quadrature signal demodulation circuit in the circuit consists of a low-noise amplifier (LNA), a low-pass filter (LPF), a balun transformer, a differential demodulator, an operational amplifier (OPA), a filtering network, and its peripheral circuits. The RF signal containing plasma density information is amplified by the LNA (LNA) with a gain of 15dB. It then passes through a low-pass filter to filter out spurious signals and other interference outside the 150MHz band, improving signal quality. The balun transformer performs differential conversion on the input RF signal, meeting the input signal type requirements of the downstream IQ demodulation chip and improving the signal's common-mode rejection ratio (CMRR). The differentially converted RF signal and the frequency-multiplied LO signal enter the differential demodulator through designated pins, outputting differential, mutually orthogonal zero-IF and second-harmonic signals. The OPA and filtering network converts the IF signal from differential to single-ended, while also providing appropriate power amplification and filtering of the second-harmonic signal. The output port impedance is matched to a standard 50 ohm.

[0014] Figure 2 The figure shows the DC LDO voltage regulator section, which consists of the TPS54300DA, TPS78501BQWDRBRQ1, ME6214A33PG, and related peripheral circuits. It implements +24V input and ±7V, +6V, +5V, and +3.3V outputs to power the entire IQ processing module.

[0015] Preferably, the crystal oscillator model in the active crystal oscillator network is SiT5157AE-FK-33E0-110T.

[0016] Preferably, the frequency multiplier model is AMK-2-13+.

[0017] Preferably, the low noise amplifier A and the low noise amplifier B are both of model IGB-003B-X.

[0018] Preferably, the low noise amplifier C model is IGB-004B-X.

[0019] Preferably, the 1 / 2 power splitter A and the 1 / 2 power splitter B are of model SBTC-2-10L.

[0020] Preferably, the 1 / 3 power splitter model is AD3PS-1+.

[0021] Preferably, the low noise amplifier D model is IGB-004B-S89.

[0022] Preferably, the low-pass filter model is HLCB0110S.

[0023] Preferably, the balun transformer model is ETC1-1-13.

[0024] Preferably, the differential demodulator model is ADL5387.

[0025] Preferably, the operational amplifier model of the operational amplifier and filtering network is THS4001.

[0026] The above description is merely a preferred embodiment of the present invention and does not limit the present invention in any way. Any person skilled in the art who, without departing from the scope of the present invention, makes any equivalent substitution, modification, or other changes to the technical solution and technical content disclosed in the present invention shall be deemed to be within the scope of the present invention and still fall within the scope of protection of the present invention.

Claims

1. An IQ signal processing module for a laser interferometer system, characterized in that: It includes three parts: local oscillator signal generation and distribution circuit, IQ orthogonal signal demodulation circuit, and DC LDO voltage regulator. The local oscillator signal generation and distribution circuit consists of an active crystal oscillator network, a frequency multiplier, a low-noise amplifier A, a low-noise amplifier B, a low-noise amplifier C, a 1 / 2 power divider A, a 1 / 2 power divider B, and a 1 / 3 power divider, which realizes the generation, frequency multiplication, amplification, and distribution of the 110MHz original local oscillator signal in the module. The IQ orthogonal signal demodulation circuit consists of a low-noise amplifier D, a low-pass filter, a balun transformer, a differential demodulator, an operational amplifier, and a filter network, which realizes the amplification, filtering, demodulation, and differential operation of the IQ orthogonal signal in the module. The DC LDO voltage regulator consists of a linear LDO and its peripheral circuits, which provides a suitable power supply for each functional chip of the module. The active crystal oscillator network outputs a 110MHz original local oscillator signal; the 1 / 2 power splitter A receives the original local oscillator signal from the active crystal oscillator network and performs two-way power equalization. One way is gain-amplified by the low-noise amplifier A and used as the laser interferometer system modulation signal, which is output to the diagnostic channel optical carrier; the other way is gain-amplified by the low-noise amplifier B and output to the 1 / 2 power splitter B; the 1 / 2 power splitter B again performs two-way power equalization on the amplified local oscillator signal, one of which is transmitted to the frequency multiplier, and the other is used as a backup output for the local oscillator signal of the entire module; the frequency multiplier performs two-fold spread spectrum on the local oscillator signal with a frequency of 110MHz and outputs a 220MHz local oscillator signal; the frequency-multiplied local oscillator signal is gain-amplified by the low-noise amplifier C, and then passes through the 1 / 3 power splitter and the 1 / 2 power splitter in sequence to achieve six-way power equalization of the doubled local oscillator signal, which is distributed to the local oscillator input end of the IQ orthogonal signal demodulation circuit; The RF signal containing plasma density information is amplified by the D gain of a low-noise amplifier and then filtered out by a low-pass filter to remove spurious signals. The balun transformer performs differential conversion on the input RF signal. The differentially converted RF signal and the frequency-doubled local oscillator signal enter the corresponding ports of the differential demodulator, which outputs orthogonal zero-IF and second-harmonic signals. The operational amplifier and filtering network realizes the differential-to-single-ended conversion of the zero-IF signal, appropriately amplifies the power, filters out the second-harmonic signal, and matches the output port impedance. The DC LDO voltage regulator and its peripheral circuits realize DC-DC voltage conversion output, providing power for all components of the entire IQ processing module.

2. The IQ signal processing module of a laser interferometer system according to claim 1, wherein the crystal oscillator model in the active crystal oscillator network is SiT5157AE-FK-33E0-110T.

3. The IQ signal processing module of a laser interferometer system according to claim 1, characterized in that: The frequency multiplier model is AMK-2-13+.

4. The IQ signal processing module of a laser interferometer system according to claim 1, characterized in that: The low noise amplifier A and the low noise amplifier B are both model IGB-003B-X; the low noise amplifier C is model IGB-004B-X; and the low noise amplifier D is model IGB-004B-S89.

5. The IQ signal processing module of a laser interferometer system according to claim 1, characterized in that: The models of the 1 / 2 power splitter A and the 1 / 2 power splitter B are SBTC-2-10L; the model of the 1 / 3 power splitter is AD3PS-1+.

6. The IQ signal processing module of a laser interferometer system according to claim 1, characterized in that: The low-pass filter model is HLCB0110S.

7. The IQ signal processing module of a laser interferometer system according to claim 1, characterized in that: The balun transformer model is ETC1-1-13.

8. The IQ signal processing module of a laser interferometer system according to claim 1, characterized in that: The differential demodulator model is ADL5387.

9. The IQ signal processing module of a laser interferometer system according to claim 1, characterized in that: The operational amplifier model of the operational amplifier and filtering network is THS4001.

10. The IQ signal processing module of a laser interferometer system according to claim 3, characterized in that: The linear LDO and its peripheral circuits are composed of a DC-DC power supply network with models TPS54300DA, TPS78501BQWDRBRQ1, TPS564201, and ME6214A33PG.

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