Signal Processor Using Multiple Frequency Bands

Patent metadata

Field	Value
Publication number	US-2017366151-A1
Application number	US-201715620084-A
Country	US
Kind code	A1
Filing date	Jun 12, 2017
Priority date	Jun 15, 2016
Publication date	Dec 21, 2017
Grant date	—

Abstract

A circuit and method is disclosed for filtering an audio signal. The circuit has a first quadrature source and multipliers for multiplying the input signal by the I and Q outputs of the quadrature source. The multiplied inputs are then passed through a pair of low pass filters, which may have an adjustable Q factor. The outputs of the low pass filters are then multiplied in a second pair of multipliers by the I and Q outputs, respectively, of a second quadrature source, which will typically be of the same frequency, but different amplitude and phase, of the first quadrature source. The twice-multiplied signals are then summed by an adder to provide an output signal. The circuit may be modified to include a companding circuit between the low pass filters and the second pair of multipliers that determines the amplitude of the input signal, filters it, and compands the signal in a compandor. The compandor may have adjustable parameters. The circuit thus allows for far greater flexibility and control of the processing of the input signal than prior art circuits.

First claim

1 . A method of processing an audio input signal, comprising:
multiplying the input signal by I and Q outputs of a first quadrature source; passing the input signal multiplied by the I output of the first quadrature source through a first low pass filter and the input signal multiplied by the Q output of the first quadrature source through a second low pass filter; multiplying an output of the first low pass filter by an I output of a second quadrature source and an output of the second low pass filter by a Q output of the second quadrature source, the second quadrature source having a different phase and amplitude than the first quadrature source, but the same frequency; and summing the outputs of the low pass filters multiplied by the outputs of the second quadrature source to provide an output signal.

2 . The method of claim 1 wherein the first and second low pass filters have adjustable Q factors.

3 . The method of claim 1 further comprising companding the outputs of the first and second low pass filters and providing a resulting companded signal as an input to the second quadrature source.

4 . The method of claim 3 further comprising:
creating an amplitude signal representing the amplitude of the input signal;
filtering the amplitude signal;
companding the filtered amplitude signal using a non-linear gain function; and
providing the companded signal as an input to the second quadrature source.

5 . The method of claim 4 wherein filtering the amplitude signal further comprises filtering the amplitude signal with a filter having differing attack and decay rates.

6 . An apparatus for processing an audio input signal, comprising:
a first quadrature source producing I and Q outputs; first and second multipliers for multiplying the input signal by the I and Q outputs of the first quadrature source, respectively; first and second low pass filters for filtering the input signal multiplied by the I output of the quadrature source and the input signal multiplied by the Q output of the quadrature source, respectively; a second quadrature source producing I and Q outputs; third and fourth multipliers for multiplying an output of the first low pass filter by the I output of the second quadrature source and an output of the second low pass filter by the Q output of the second quadrature source, the second quadrature source having a different phase and amplitude than the first quadrature source, but the same frequency; and an adder for summing the outputs of the low pass filters multiplied by the outputs of the second quadrature source to provide an output signal.

7 . The apparatus of claim 6 wherein the first and second low pass filters are configured so that their Q factors are adjustable.

8 . The apparatus of claim 6 further comprising a circuit for companding the outputs of the first and second low pass filters and providing a resulting companded signal as an input to the second quadrature source.

9 . The apparatus of claim 8 further comprising:
fifth and sixth multipliers for multiplying outputs from the first and second low pass filters by themselves to provide an amplitude signal representing the amplitude of the input signal;
a third filter for filtering the amplitude signal;
a compandor for companding the filtered amplitude signal using a non-linear gain function.

10 . The apparatus of claim 9 wherein the filter for filtering the amplitude signal has differing attack and decay rates.

Assignees

• Ess Technology Inc

Inventors

• Mallinson A Martin

Classifications

• H03G3/3005

  in amplifiers suitable for low-frequencies, e.g. audio amplifiers (H03G3/32, H03G3/34 take precedence) · CPC title

• H04R3/04

  for correcting frequency response · CPC title

• H03G5/165 Primary

  Equalizers; Volume or gain control in limited frequency bands · CPC title

• H04R2430/20

  Processing of the output signals of the acoustic transducers of an array for obtaining a desired directivity characteristic (H04R2203/12 takes precedence) · CPC title

• H04R3/007

  Protection circuits for transducers · CPC title