Abstract
In order to extract the weak terahertz signal in the terahertz time-domain spectroscopy (THz-TDS), and to solve the problem of single amplification of the existing lock-in amplifier or manual adjustment of the amplification, a lock-in amplifier with self-adaptive adjustment function for phase and amplification is designed. Compared with the traditional lock-in amplifier, it reduces the use of electronic components such as phase shifters, modulators and summators, and reduces the development cost of the circuit.
Highlights
IntroductionThe terahertz time domain spectroscopy system [13,14] is mainly composed of femtosecond lasers, modulated bias modules, phase and amplification adaptive lock-in amplifiers, optical delay lines, THz photoconductive transmitting and receiving antennas, lens groups, and PC terminals
Terahertz wave [1,2] refers to electromagnetic waves with a frequency of 0.1 THz ~ 10 THz (1 THz = 1012 Hz), located between the microwave and infrared
The terahertz time domain spectroscopy system [13,14] is mainly composed of femtosecond lasers, modulated bias modules, phase and amplification adaptive lock-in amplifiers, optical delay lines, THz photoconductive transmitting and receiving antennas, lens groups, and PC terminals
Summary
The terahertz time domain spectroscopy system [13,14] is mainly composed of femtosecond lasers, modulated bias modules, phase and amplification adaptive lock-in amplifiers, optical delay lines, THz photoconductive transmitting and receiving antennas, lens groups, and PC terminals. The lock-in amplifier can extract the weak signal proportional to the intensity of the THz pulse electric field [15] and record the time-domain waveform of the terahertz pulse through the PC terminal host computer module. The phase and amplification adaptive lock-in amplifier is mainly composed of 7 parts, pre-current amplifier, band-pass filter, modem, low-pass filter, post-amplifier, ADC module and MCU control unit [16]. X1 (t ) is sampled by the ADC module after passing through the post amplifier and uploaded to the MCU unit
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