www.andyware.com/abox2/library/equipment.txt

    Mostly circuits having to with spectral analysis

spectrum_analyzer.abox2
spec_zoom.abox2

    Uses downsampling and decimation to zoom in on a spectrum.
    
    The smaller the span, the longer it takes to get a reading.
    This is the uncertainy principle in action.

    The center frequency circuit doesn't quite work up to standards.
    For best results, use at zero center frequency.

    The zoom circuit uses 6th order filters.
    This results in bleed through at the upper and lower ends of the 
    measured spectrum. Higher order filters could be devised.

spec_hold.abox2

    Uses a feedback loop to store the highest peaks measured over a long
    period of time. Set the d input as the hold length.

mag_spec.abox2

    This circuit returns a filled magnitude spectrum, 512 pair of (mag,mag).
    Contrast this the 'power' mode of the FFTOP object which returns 512 pairs of (mag^2,0).

4_mag_spec.abox2

    This circuit takes one input stream and builds 4 output spectrums.
    Each spectrum is separated in time by 1/4 of a sample frame, 
    approximately 5.8 ms. In this way a better indication of arrival time is
    achieved without sacrificing frequency resolution.

4_mag_extract_mux.abox2

    Used with 4_mag_spec.
    This circuit will extract 1 frequency from each of the 4 input spectrums
    and build an output stream indicating the magnitude of said frequency.
    The output will have only 4 values, each running for 256 samples.