IQ signal processing module of laser interference system

Abstract

The invention provides an IQ signal processing module of a laser interference system, which relates to a signal demodulation technology and comprises a local oscillator signal generation and distribution circuit, an IQ orthogonal signal demodulation circuit and a direct-current LDO (Low Dropout Regulator) voltage stabilization source. The local oscillator signal generation and distribution module is composed 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 and a 1 / 3 power divider, and generation, frequency multiplication, amplification and distribution of a 110MHz local oscillator original signal in the module are achieved. The IQ orthogonal signal demodulation circuit consists of a low-noise amplifier D, a low-pass filter, a balun transformer, a differential demodulator and an operational amplifier and filter network, and is used for realizing amplification, filtering, demodulation and differential operation of IQ orthogonal signals in the module; the direct-current LDO voltage stabilization source is composed of a linear LDO and a peripheral circuit of the linear LDO and provides a proper power source for all functional chips of the module. According to the invention, the signal link structure is simplified, the number of photoelectric detectors used in the multichannel interference system is reduced, and the manufacturing cost is saved.

Description

Technical Field

[0001] The 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. The plasma density is diagnosed indirectly by measuring the laser phase, based on the physical relationship between the phase of the laser and the refractive index of the path material when the laser is transmitted in the plasma. The conventional method is to calibrate the phase of the intermediate frequency signal of the reference channel and the detection channel through 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. The optical path structure of this method is complex, and the density information of a diagnostic channel needs to be obtained by combining two photodetectors. Due to the non-correlation of the two photodetectors, the key indicators such as noise suppression and bandwidth are not ideal. Summary of the invention

[0003] In order to solve the above problems, an IQ signal processing module of a laser interferometer system is proposed. When the reference channel and the detection channel optical path directly photoelectrically detect the beat frequency output of the RF signal containing phase change information, it is then orthogonally demodulated with the system LO local oscillator signal, and the mathematical cotangent or tangent calculation is performed on the output zero intermediate frequency I and Q two-way signals to obtain the phase time change amount and invert the plasma density information within the time change range. This method uses only one photodetector for any diagnostic optical path, and the key indicators such as phase resolution, noise suppression, bandwidth, and response time are greatly improved.

[0004] The present invention proposes an IQ signal processing module of a laser interferometer system, comprising three parts: a local oscillator signal generation and distribution circuit, an IQ orthogonal signal demodulation circuit, and a direct current LDO voltage regulator; the local oscillator signal generation and distribution circuit is composed 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, so as to realize the generation, frequency multiplication, amplification and distribution of a 110MHz original local oscillator signal in the module; the IQ orthogonal signal demodulation circuit is composed of a low noise amplifier D, a low-pass filter, a balun transformer, a differential demodulator, an operational amplifier and a filtering network, so as to realize the amplification, filtering, demodulation and differential operation of the IQ orthogonal signal in the module; the direct current LDO voltage regulator is composed of a linear LDO and its peripheral circuits, so as to provide a suitable power supply for each functional chip of the module;

[0005] The active crystal oscillator network outputs a 110MHz original local oscillator signal; the 1 / 2 power divider A receives the original local oscillator signal output by the active crystal oscillator network and performs two-way power splitting, one of which is gain-amplified by the low-noise amplifier A and used as the laser interference system modulation signal, and is output to the diagnostic channel optical carrier; the other is gain-amplified by the low-noise amplifier B and output to the 1 / 2 power divider B; the 1 / 2 power divider B again splits the amplified local oscillator signal into two ways of power splitting, 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 frequency of the 110MHz local oscillator signal 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 divider in sequence. , a 1 / 2 power divider realizes 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 doubled local oscillator signal enter the corresponding port of the differential demodulator, and the differential demodulator outputs an 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 and its peripheral circuits realize DC-DC voltage conversion output to 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 the present invention can realize phase demodulation of the input RF signal and obtain the phase change of the RF signal per unit time, and is suitable for the IQ mode time-resolved diagnostic system for obtaining the plasma density of the fusion device by laser interferometry. Compared with the traditional plasma density laser interferometer phase meter, the system signal link structure is simplified, the cost of the photoelectric detector is saved, and the key indicators such as noise suppression, bandwidth, and response time of the input RF signal demodulation are improved. 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 purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above-mentioned purpose, the present invention adopts the following technical scheme.

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

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

[0013] Figure 1The IQ orthogonal signal demodulation circuit in the circuit is composed of a low noise amplifier D, a low pass filter, a balun transformer, a differential demodulator, an operational amplifier and a filtering network and its peripheral circuits. The RF signal containing plasma density information is amplified by a low noise amplifier D with a gain of 15dB, and then filtered out by a low pass filter to remove spurious and other interferences outside the 150MHz band, thereby improving the signal quality; the balun transformer performs differential conversion on the input RF signal, which not only meets the signal input type requirements of the lower-level IQ demodulation chip, but also improves the signal common mode rejection ratio; the differentially converted RF signal and the frequency-multiplied LO signal enter the differential demodulator through the designated pins, and output differential mutually orthogonal zero intermediate frequency and second harmonic signals; the operational amplifier and filtering network realize the differential to single-ended conversion of the intermediate frequency signal, and at the same time appropriately amplifies the power and filters out the second harmonic signal, and matches the output port impedance to the conventional 50 ohms.

[0014] Figure 2 The figure shows the DC LDO voltage regulator part, which is composed of TPS54300DA, TPS78501BQWDRBRQ1, ME6214A33PG and related peripheral circuits, realizing +24V input, ±7V, +6V, +5V, +3.3V output, and powering 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 is of model IGB-004B-X.

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

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

[0021] Preferably, the low noise amplifier D is of model 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 filter network is THS4001.

[0026] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any technician in the relevant technical field, without departing from the scope of the technical solution of the present invention, makes any form of equivalent replacement or modification to the technical solution and technical content disclosed in the present invention, which does not depart from the content of the technical solution of the present invention and still falls within the protection scope 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 is composed 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 is composed 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 is composed 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 divider A receives the original local oscillator signal output from the active crystal oscillator network and performs two-way power equalization, one of which is gain-amplified by the low-noise amplifier A and used as the modulation signal of the laser interference system, and is output to the diagnostic channel optical carrier; the other is gain-amplified by the low-noise amplifier B and output to the 1 / 2 power divider B; the 1 / 2 power divider 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 of 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 local oscillator signal after frequency multiplication is gain-amplified by the low-noise amplifier C, and then passes through the 1 / 3 power divider and the 1 / 2 power divider in turn to achieve six-way power equalization of the local oscillator signal after double frequency multiplication, and 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 low noise amplifier D gain, and then filtered by the low pass filter to remove the spurious; the balun transformer performs differential conversion on the input RF signal; the differentially converted RF signal and the frequency-multiplied local oscillator signal enter the corresponding port of the differential demodulator, and the differential demodulator outputs orthogonal zero intermediate frequency and second harmonic signals; the operational amplifier and filter network realizes the differential to single-ended conversion of the zero intermediate frequency signal, appropriately amplifies the power and filters 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 and provide power for all components of the entire IQ processing module.

2. According to the IQ signal processing module of the laser interferometer system according to claim 1, 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 of model IGB-003B-X; the low noise amplifier C is of model IGB-004B-X; and the low noise amplifier D is of 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 divider A and the 1 / 2 power divider B are SBTC-2-10L; the model of the 1 / 3 power divider 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 filter 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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