The invention of the first Lock-in Amplifier (LIA) of EG & G PARC (predecessor of SIGNAL RECOVERY) in the United States in 1962 made a breakthrough in weak signal detection technology and greatly promoted basic science and engineering. Development of technology. At present, the continuous improvement of weak signal detection technology and instruments has been widely used in many scientific and technical fields. Future scientific research not only puts higher requirements on weak signal detection technology, but also the development of new science and technology has in turn promoted The birth of a new principle and new method for weak signal detection.
The early LIA was realized by analog circuits. With the development of digital technology, there has been a mix of analog and digital LIA. This LIA only uses digital filters in the signal input channel, reference signal channel and output channel to suppress noise. Or add analog-to-digital conversion (ADC), digital-to-analog conversion (DAC) and various general digital interface functions on the basis of analog lock-in amplifier (referred to as ALIA), which can realize auxiliary functions such as computer control, monitoring and display However, its core phase-sensitive detector (PSD) or demodulator is still implemented using analog electronic technology, which is essentially ALIA. Until the phase-sensitive detector or demodulator was implemented with digital signal processing, a digital lock-in amplifier (DLIA) appeared. DLIA has many outstanding advantages over ALIA and has been favored. However, in some special occasions, ALIA still plays an irreplaceable role in DLIA.