Wide-range lock-in amplifier
AssigneeThe United States of America as represented by the United States Department of Energy
InventorDavid R. McNeilly
Life of this patent
Estimating the term…
Abstract
A lock-in amplifier is provided which allows detection of a signal buried in noise without preprocessing of the input signal. An analog signal multiplier is used to obtain a dc output which is the product of the signal being detected and a high-purity sine wave signal. A reference signal of a known selectable frequency is applied to a sine-wave generator to generate the sine wave of the same frequency. The sine wave is applied to a multiplier through a phase shift arrangement to allow the detection of both amplitude of the detected signal and the phases relative to the reference signal. The multiplier output is filtered by a low-pass filter to eliminate unwanted frequency components from the output signal.
Claims4
A lock-in amplifier for detecting a particular frequency component of an input signal, comprising:
- a first sine wave generating means responsive to an input reference signal at an input thereof having a frequency equal to the frequency of said component of said input signal to be detected for generating a first sine wave reference signal at an output thereof which is equal in frequency to and 90.degree. out-of-phase with said input reference signal;
- a second sine wave generating means responsive to the output of said first sine wave generating means for generating a second sine wave reference signal at an output thereof which is equal in frequency to and in phase with said input reference signal;
- a first multiplier means having a first input for receiving said input signal and a second input for receiving said first sine wave reference signal for generating a first dc signal at an output thereof which is a product of said component of said input signal to be detected and said first sine wave reference signal;
- a second multiplier means having a first input for receiving said input signal and a second input for receiving said second sine wave reference signal for generating a second dc signal at an output thereof which is a product of said component of said input signal to be detected and said second sine wave reference signal;
- and
- first and second low-pass filtering means connected respectively in series with the outputs of said first and second multiplier means.
Dependencies are inferred from the claim text.