Voice activated circuit and radio using same

• US 6,633,847 B1
• Filed: 01/05/2000
• Issued: 10/14/2003
• Est. Priority Date: 01/05/2000
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Fang, Jing
• Primary Examiner(s): Banks-Harold, Marsha D.
• Assistant Examiner(s): Han, Qi
• Application Number:
  US09/478,075
• Time in Patent Office: 1,378 Days
• Field of Search: 704/367, 704/207, 704/275, 379/388.02, 379/388.01, 379/388.03, 379/388.04, 379/203.01, 379/204.04, 375/316, 375/150
• US Class Current: 704/270
• CPC Class Codes: G10L 2025/783 based on threshold decision
• CPC Class Codes: G10L 25/78 Detection of presence or absence of voice signals switching of direction of transmission by voice frequency in two-way loud-speaking telephone systems H04M9/10

Abstract

A voice-activated circuit such as a VOX circuit (100) includes a quadratic detector (108). Quadratic detector (108) uses a sum of weighted instantaneous autocorrelation with multiple lags and where the instantaneous autocorrelation is the product of the signal or a time-advanced version of the signal multiplied by a time delayed version of itself. In one embodiment of the invention a quantized delayed signal is used where changing the sign of the signal without using real multiplication forms the quantized delayed signal. By avoiding the use of multipliers, the complexity and therefore the cost of the VOX circuit (100) is significantly reduced.

Claims

1. A voice-activated circuit, comprising:

an input port for receiving a signal;

a quadratic detector coupled to the input port and the quadratic detector implements the equation;

$\underset{m}{\sum <br><br>}<br><br>{\mathrm{\omega <br><br>}}_m<br><br>x<br><br>\left(k\right)<br><br>x<br><br>\left(k-m\right),$

where

x(k) is the signal in time (k) and ω

_m is a weighting coefficient in lag (m); and

wherein said quadratic detector comprises a quantizer and a finite impulse response (FIR) filter with Canonical Signed Digit (CSD) coefficients coupled in parallel.

2. A voice-activated circuit as defined in claim 1, wherein said quadratic detector uses a sum of weighted instantaneous autocorrelation with a plurality of lags and multiplies said signal by a quantized delayed signal.

3. A voice-activated circuit as defined in claim 1, wherein the quantizer and the FIR filter each have an input and an output, and the inputs of the quantizer and the FIR filter are connected together, the voice-activated circuit further comprising:

a multiplexer coupled to the outputs of the quantizer and the FIR filter.

4. A voice-activated circuit as defined in claim 3, further comprising:

an inverter coupled between the output of the FIR filter and the multiplexer.

5. A radio, comprising:

a transmitter; and

a VOX circuit coupled to the transmitter, said VOX circuit comprising;

a quadratic detector responsive to a signal and that implements the equation;

$\underset{m}{\sum <br><br>}<br><br>{\mathrm{\omega <br><br>}}_m<br><br>x<br><br>\left(k\right)<br><br>x<br><br>\left(k-m\right),$

where

x(k) is the signal in time (k) and ω

_m is a weighting coefficient in lag (m); and

wherein said quadratic detector comprises a quantizer and a finite impulse response (FIR) filter with Canonical Signed Digit (CSD) coefficients coupled in parallel.

6. A radio as defined in claim 5, wherein the radio further comprises:

a lowpass filter and a highpass filter which are shared between the VOX circuit and the radio, and said lowpass and highpass filters are coupled together in series and filter the signal prior to being provided to the quadratic detector.

7. A voice-activated circuit, comprising:

an input port for receiving a signal; and

a quadratic detector coupled to the input port and the quadratic detector implements the equation;

$\underset{m}{\sum <br><br>}<br><br>{\mathrm{\omega <br><br>}}_m<br><br>x<br><br>\left(k+m\right)<br><br>x<br><br>\left(k-m\right),$

where

x(k) is the signal in time (k) and ω

_m is a weighting coefficient in lag (m); and

wherein said quadratic detector comprises a quantizer and a finite impulse response (FIR) filter with Canonical Signed Digit (CSD) coefficients coupled in parallel.

8. A voice-activated circuit as defined in claim 7, wherein the quadratic detector uses a sum of weighted instantaneous autocorrelation which is determined by taking the product of a time-advanced version of the signal and a time-delayed version of the signal.

9. A radio, comprising:

a transmitter; and

a VOX circuit coupled to the transmitter, said VOX circuit comprising;

a quadratic detector responsive to a signal and that implements the equation;

$\underset{m}{\sum <br><br>}<br><br>{\mathrm{\omega <br><br>}}_m<br><br>x<br><br>\left(k+m\right)<br><br>x<br><br>\left(k-m\right),$

where

x(k) is the signal in time (k) and ω

_m is a weighting coefficient in lag (m); and

wherein said quadratic detector comprises a quantizer and a finite impulse response (FIR) filter with Canonical Signed Digit (CSD) coefficients coupled in parallel.