System for limiting the magnitude of sampled data
AssigneeEricsson Inc.
InventorVan E. Hanson
Life of this patent
Estimating the term…
Abstract
An analog signal is sampled at sampling rates which are low relative to the highest frequency components of the analog signal. The digitized sample signals are processed and amplitude limited in a digital signal processor. Real and imaginary components for each data sample are determined. The magnitude of the complex phasor corresponding to the data sample is calculated using those real and imaginary components. If the calculated magnitude of the complex phasor exceeds a preset limit, then the sample is scaled by a suitable scaling factor, (i.e. the ratio of the preset limit to the actual calculated phasor magnitude) without changing the phase of the input sample. By operating at minimum sampling rates, digital signal processing resources are conserved while still reliably limiting the processed signal.
Claims29
A method for producing an output signal of limited amplitude from an input signal of variable amplitude, comprising:
- transforming the variable amplitude input signal to obtain an in-phase signal from the input signal and a corresponding quadrature signal from the input signal in which desired component frequencies of said quadrature signal are 90-degrees phase rotated relative to corresponding frequency components of said in-phase signal;
- determining a magnitude of said variable amplitude input signal by combining said in-phase and quadrature signals obtained from the variable amplitude input signal;
- comparing said determined magnitude with a limiting threshold;
- and
- if said determined magnitude exceeds said limiting threshold, scaling at least one of said in-phase or quadrature signals based on said determined magnitude to produce the output signal of limited amplitude, wherein said in-phase and quadrature signals used in said determining step are independent of said output signal.
An amplitude limiter for processing an input signal into an output signal, comprising:
- a transformer having an input port to receive the input signal and to separate the input signal into an in-phase component and a quadrature component;
- an arithmetic circuit, connected to receive the in-phase component and the quadrature component, said circuit to calculate the magnitude of the in-phase and quadrature components, to compare said magnitude to a predetermined limit value and to output a gain control signal based on said comparison;
- and
- a gain control device, connected to receive the in-phase signal, the quadrature signal, and the gain control signal, and connected to output said output signal, said gain control device creating said output signal by scaling at least one of the in-phase or quadrature signals by a scaling factor controlled by said gain control signal.
A method for producing an output signal of limited amplitude from a variable amplitude input signal, comprising:
- sampling the input signal;
- transforming the sampled signal to obtain its in-phase and quadrature components;
- determining the phasor magnitude of the sampled signal based only on the in-phase and quadrature components;
- and
- comparing the phasor magnitude to a predetermined limit value;
- limiting at least one of the in-phase and quadrature components based on the relation of the phasor magnitude to the predetermined limit value to generate an output sample of limited amplitude, wherein said in-phase and quadrature signals used in said determining step are independent of said output signal.
A method for limiting an output signal generated in response to an input signal comprising:
- determining the real and imaginary parts of the input signal;
- calculating the magnitude of a complex signal comprising the real and imaginary parts of the input signal;
- comparing the complex magnitude to a predetermined value;
- limiting the complex magnitude to the predetermined value;
- and
- generating a limited output signal based on the limited complex magnitude wherein said real and imaginary parts used in said calculating step are independent of said limited output signal.
In an audio signal processor, a method for limiting the magnitude an output signal from a received analog audio signal comprising:
- sampling the analog audio signal at a sampling rate about twice the frequency of the analog audio signal to generate an input sample;
- transforming the input sample into its complex real and imaginary components using a Hilbert transform;
- determining the magnitude of a complex signal using the real and imaginary components;
- comparing the complex magnitude to a predetermined threshold;
- if the complex magnitude exceeds the predetermined threshold, scaling at least one of the real and imaginary components by the ratio of the predetermined threshold to the complex magnitude;
- and
- converting the at least one scaled component to an analog output signal, wherein said step of determining is performed without feeding said output signal back to said real and imaginary components.
A signal processor for limiting the magnitude of an output signal from a variable amplitude input signal, comprising:
- an analog to digital converter for sampling the input signal at a sampling rate about twice the frequency of the analog audio signal to generate a digitized input sample;
- a transformer for transforming the input sample into its complex real and imaginary components;
- a processor for inputting the real and imaginary components and for determining the magnitude of a complex signal consisting of the real and imaginary components;
- a comparator for comparing the complex magnitude to a predetermined threshold;
- an attenuator for inputting at least one of the real and imaginary components and for scaling at least one of the real and imaginary components by a ratio of the predetermined threshold to the complex magnitude if the complex magnitude exceeds the predetermined threshold;
- and
- a digital to analog converter for converting the scaled portion of the complex magnitude to analog form.
An apparatus for producing an output signal of limited amplitude from an input signal of variable amplitude comprising:
- a transformer for transforming an input signal into an in-phase signal and a corresponding quadrature signal in which desired component frequencies of said quadrature signal are 90.degree. phase rotated relative to corresponding frequency components of said in-phase signal, and
- electronic circuitry for receiving the in-phase and quadrature signals and for performing the following processing steps including:
- determining a magnitude of said input signals by combining said in-phase and quadrature signals;
- and
- comparing said determined magnitude with a limiting threshold;
- and
- a gain controller receiving at least one of the in-phase and quadrature signals and, if said determined magnitude exceeds the limiting threshold, scaling at least one of said in-phase or quadrature signals based on said determined magnitude to produce an output signal of limited amplitude.
Dependencies are inferred from the claim text.