Yes, it is possible to construct a phase difference detector for two low-frequency signals using an analog multiplier and a low-pass filter. Let's go through the basic steps to design such a circuit.
Analog Multiplier: An analog multiplier is a device that multiplies two input signals and produces an output signal proportional to their product. In this case, we need a multiplier to obtain the product of the two input signals, which represents the phase difference between them. There are various types of analog multipliers available, such as Gilbert cell multipliers or AD633 analog multipliers.
Input Signal Conditioning: The two low-frequency signals need to be properly conditioned before being fed into the analog multiplier. This may involve amplification, level shifting, and filtering, depending on the specific requirements of your signals and the input range of the multiplier.
Multiplication: Connect the two conditioned signals to the input ports of the analog multiplier. The output of the multiplier will be proportional to the product of the two input signals, which represents the phase difference.
Low-Pass Filtering: The output of the analog multiplier will contain not only the desired phase difference signal but also unwanted high-frequency components. To extract the low-frequency component, a low-pass filter is needed. The cutoff frequency of the filter should be chosen carefully to retain the desired frequency range of 10Hz-20Hz while attenuating higher frequencies.
Output Display or Measurement: Finally, you may choose to display or measure the filtered output signal. This could involve further conditioning or conversion, such as scaling the signal for display on a screen or converting it to a digital form for data logging or analysis.
It's important to note that the design details and specifications of the circuit will depend on the specific requirements of your application and the available components. Additionally, you might encounter challenges related to noise, signal conditioning, and calibration. Therefore, a thorough understanding of analog circuit design principles and signal processing techniques is necessary to successfully implement a phase difference detector using an analog multiplier and low-pass filter.