Tone receiver for digital data communication systems

Details Tone receiver for digital data communication systems Tone receiver for digital data communication systems

1983-06-13

1986-01-07

Caldwell, Sr., John W.

Communications: electrical

Continuously variable indicating

With meter reading

364572, 364574, 364724, 375103, H04Q 500, G06F 738

Patent

active

045636818

ABSTRACT:
A device for detecting the presence of an alarm tone of a given frequency within a received signal carrying digital data in addition to said tone. The receiver comprises an analog-to-digital converter (42) the output of which is applied to a first recursive bandpass filter centered at the frequency of the alarm tone and the feedback loop of which includes a limiter. In addition, an input feedforward loop is provided for adding (at 58) the output signal from the converter (42), as multiplied by a coefficient .gamma., to the output signal from the limiter. The output signal from the adder (58) is hard limited (at 44), then passed through a second bandpass filter. The energy of the signal obtained at the output of said second filter is then measured to provide indication of a tone's being received when said energy exceeds a predetermined threshold.

REFERENCES:
patent: 3502986 (1970-03-01), Lucky
patent: 4053750 (1977-10-01), Constant
patent: 4156919 (1979-05-01), Constant
patent: 4228517 (1980-10-01), Constant
patent: 4305133 (1981-12-01), Amada et al.

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