Method and an apparatus for converting an input frequency to a voltage signal using a passive filter

A method for converting an input frequency to a voltage signal using a passive filter, the method comprising:

• providing an input signal having a specified frequency and amplitude to a passive filter, wherein the passive filter is configured to attenuate the input signal based on the specified frequency being out of a pass band of the passive filter;
• obtaining an attenuated signal corresponding to the input signal from the passive filter;
• and
• providing the attenuated signal to a peak detector to obtain a direct current (DC) signal having an output voltage proportional to the specified frequency.

An apparatus for converting an input frequency to a voltage signal using passive circuitry, the passive circuitry comprising:

• a first circuit to:
• receive an input signal having a specified frequency and amplitude, the specified frequency of the input signal being out of a pass band of the first circuit, and
• output an attenuated signal corresponding to the input signal;
• and
• a second circuit to convert the attenuated signal to a direct current (DC) signal having an output voltage proportional to the specified frequency.