Signal detector and method for detecting signals having selected frequency characteristics

A signal detector for monitoring a universe of oscillatory signals and operative to produce detector output in response to the present of one or more target signals wherein the target signals have frequency characteristics within a selected range, said signal detector comprising:

• input processing means for receiving said oscillatory signals and for processing said oscillatory signals to remove oscillatory signals which do not have frequency characteristics within the selected range and for producing an input signal corresponding to target signals which are present in said oscillatory signals, said input signal having an input frequency and an input amplitude corresponding to said target signals;
• a first control circuit means electrically coupled to said input signal for producing a first control signal proportional to the amplitude of said input signal;
• processing circuit means receiving said input signal for producing an intermediate signal having an intermediate frequency proportional to the frequency of said input signal;
• and
• first amplifier means for amplifying said intermediate signal to produce a detector output signal at an output frequency and amplitude, said amplifier means having first variable gain control circuitry operative to controllably vary the gain of said amplifier means, said variable gain control circuitry responsive to said first control signal to vary the gain of said amplifier means in proportion to the amplitude of the input signal.

A method for monitoring oscillatory signals in order to indicate when the presence of selected signals having a frequency within a selected frequency range, comprising the steps of:

• receiving said oscillatory signals;
• filtering said oscillatory signals to remove substantially all oscillatory signals which do not have a frequency within the selected frequency range and producing an input signal when at least one of said selected signals is present such that said input signal has an input amplitude and an input frequency representative of the frequency and amplitude of all of the selected signals which are then present;
• amplifying input signal at an amplification gain to produce a detector output wherein the amplification gain of the input signal is adjustably varied as a function of the input amplitude;
• and
• displaying said detector output.