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US 5,471,534 AGranted
Devices, systems and methods for composite signal decoding employing interpolation filter
AssigneeTexas Instruments Incorporated
InventorMark E. Utter
Life of this patent
Estimating the term…
Abstract
A device and method for composite signal decoding is provided in which an analog-to-digital converter (15) digitizes an incoming FM composite signal. The digitized signal is filtered by an interpolator (13) which uses filter coefficients developed as a function of a sampled pilot signal's phase without synchronizing the decoder sample rate to the pilot signal to reconstruct the composite signal at points Where the pilot signal phase is a multiple of 45.degree..
Claims47
A decoder for decoding a composite signal sampled during a sample interval at a pre-determined sample rate;
- said composite signal synchronized with a pilot signal;
- said decoder including
- a filter for filtering selected portions of said composite signal;
- said filter including filter coefficients for operating on said composite signal;
- means for developing said filter coefficients as a function of said pilot signal;
- an interpolator filter for constructively determining a value of said composite signal in said sample interval and at such instances as the phase of said pilot signal obtains an integral multiple of a pre-determined phase angle;
- and
- said sample interval of said pre-determined sample rate being asynchronous to said pilot signal.
5 more elements
A decoder comprising
- a polyphase filter for obtaining a filtered output signal from a sample of an input composite signal, said polyphase filter comprising a plurality of sub-filters;
- said sample including a pilot signal;
- each of said sub-filters being associated with a pre-determined offset from a reference pilot phase angle;
- a pilot phase calculator for determining a phase angle of said pilot signal;
- a filter bank selector for selecting one of said sub-filters for filtering said sample, said pre-determined offset of the one corresponding to an offset of said phase angle;
- and
- a channel selector for selecting a first and second channel signal from said filtered output signal.
4 more elements
A signal receiver system including
- an antenna for receiving an input composite signal;
- an amplifier for amplifying said input composite signal;
- and
- a decoder for decoding a composite signal sampled during a sample interval at a pre-determined sample rate;
- said composite signal synchronized with a pilot signal;
- said decoder including
- a filter for filtering selected portions of said composite signal;
- said filter including filter coefficients for operating on said composite signal;
- means for determining said filter coefficients as a function of said pilot signal;
- an interpolator filter for constructively determining a value of said composite signal in said sample interval and at such instances as the phase of said pilot signal obtains an integral multiple of a pre-determined phase angle;
- and
- said sample interval of said pre-determined sample rate being asynchronous to said pilot signal.
9 more elements
A method for decoding a composite signal with a decoder, said method including:
- a) sampling said composite signal during a time interval and obtaining a sampled composite signal, said sampled composite signal including a pilot signal;
- b) calculating a phase offset of said pilot signal from a reference pilot signal with a phase calculator;
- c) filtering said sampled composite signal with an interpolation filter to obtain a constructive composite signal corresponding to said reference pilot signal;
- and,
- d) selecting portions of said constructive composite signal with a channel selector.
2 more elements
A method for decoding a composite signal in a signal receiver system, said method including;
- a) receiving said composite signal with an antenna;
- b) amplifying said composite signal;
- c) discretizing said composite signal with a digital-to-analog converter;
- d) decoding said composite signal with a decoder, said decoding step including:
- i) sampling said composite signal during a time interval and obtaining a sampled composite signal, said sampled composite signal including a pilot signal;
- ii) calculating a phase offset of said pilot signal from a reference pilot signal with a phase calculator;
- iii) filtering said sampled composite signal with an interpolation filter to obtain a constructive composite signal corresponding to said reference pilot signal;
- and,
- iv) selecting portions of said constructive composite signal with a channel selector;
- e) converting said portions to time-varying output signals with a digital-to-analog converter;
- and,
- f) filtering noise from said time-varying output signals using a filter.
9 more elements
A decoder for decoding a composite signal sampled during a sample interval at a pre-determined sample rate;
- said composite signal synchronized with a pilot signal;
- said decoder including
- a filter for filtering selected portions of said composite signal;
- said filter including filter coefficients for operating on said composite signal;
- means for developing said filter coefficients as a function of said pilot signal;
- a pilot signal suppressor for removing said pilot signal from said composite signal, said pilot signal suppressor including;
- a pilot magnitude calculator for determining a value of said pilot signal in a sampled portion of said composite signal;
- a subtractor for subtracting said value of the pilot signal from said sampled portion of the composite signal;
- and
- said sample interval of said pre-determined sample rate being asynchronous to said pilot signal.
7 more elements
A decoder for decoding a composite signal sampled during a sample interval at a pre-determined sample rate;
- said composite signal synchronized with a pilot signal;
- said decoder including
- a filter for filtering selected portions of said composite signal;
- said filter including filter coefficients for operating on said composite signal;
- means for developing said filter coefficients as a function of said pilot signal;
- a filter coefficient generator for generating said filter coefficients as a function of said pilot signal, said filter coefficient generator including:
- a transformer for generating a frequency-dependent signal by transforming a sampled portion of said composite signal at the frequency of said pilot signal with a transform algorithm,
- a pilot phase calculator for determining the phase of said pilot signal associated with said frequency-dependent signal, and
- a filter coefficient selector for developing said filter coefficients as a function of the phase of said pilot signal and for providing said filter coefficients to said filter;
- and
- said sample interval of said pre-determined sample rate being asynchronous to said pilot signal.
8 more elements
Dependencies are inferred from the claim text.