Nonlinear-least squares based method and apparatus for FSK signal decoding
Assignee3Com Corporation
InventorZheng-She Liu
Life of this patent
Estimating the term…
Abstract
Disclosed is a method and apparatus for receiving FSK signals using estimation theory. A received signal is filtered to obtain energy estimates for a first frequency corresponding to a binary “0” and a second frequency corresponding to a binary “1”. The energy estimates are subtracted to obtain a difference value and an odd number of samples of a series of difference values is smooth filtered in order to produce a series of average values. A sliding window is applied to the series of average values that detects a clear majority of sample corresponding to either the binary “0” frequency or the binary “1” frequency in order to produce a binary output signal that corresponds to the received signal.
Claims27
A receiver for receiving a FSK signal having a first frequency corresponding to a binary “0” and a second frequency corresponding to a binary “1”, the receiver comprising:
- a first filter having an input terminal for receiving the FSK signal and an output terminal, where the first filter is configured to pass a first phase of the first frequency to the output terminal of the first filter;
- a second filter having an input terminal for receiving the FSK signal and an output terminal, where the second filter is configured to pass a second phase of the first frequency to the output terminal of the second filter;
- a first adder having a first input terminal coupled to the output terminal of the first filter, a second input terminal coupled to the output terminal of the second filter and an output terminal;
- a third filter having an input terminal for receiving the FSK signal and an output terminal, where the third filter is configured to pass a first phase of the second frequency to the output terminal of the third filter;
- a fourth filter having an input terminal for receiving the FSK signal and an output terminal, where the fourth filter is configured to pass a second phase of the second frequency to the output terminal of the fourth filter;
- a second adder having a first input terminal coupled to the output terminal of the third filter, a second input terminal coupled to the output terminal of the fourth filter and an output terminal;
- a subtractor having a positive input terminal coupled to the output terminal of the first adder, a negative terminal coupled to the output terminal of the second adder and an output terminal;
- a smoothing filter having an input terminal coupled to the output terminal of the subtractor and an output terminal, wherein the smoothing filter averages a sequence of samples from the subtractor to produce an average value signal having a sign value;
- and
- a window decoder having an input terminal coupled to the output terminal of the smoothing filter and an output terminal for outputting a binary data signal, wherein the window decoder is configured to monitor a sequence of average value signals from the smoothing filter, and wherein the binary data signal matches the sign value of each of the average value signals.
A method for decoding a received signal having a first frequency representing a binary “0” and a second frequency representing a binary “1”, the method comprising the steps:
- determining a first energy level of the received signal corresponding to the first frequency;
- determining a second energy level of the received signal corresponding to the second frequency;
- comparing the first and second energy levels in order to obtain a difference signal;
- averaging a predetermined number of samples of the difference signal to obtain an average signal;
- and
- monitoring a predetermined number of samples of the average signal in order to detect a sequence in which each of the average signal samples correspond to one of the first and second frequencies and generating a corresponding binary bit in a binary data signal responsive thereto.
A receiver for decoding a received signal having a first frequency representing a binary “0” and a second frequency representing a binary “1”, the receiver comprising:
- first energy detecting means for detecting an energy level in the received signal corresponding to the first frequency;
- second energy detecting means for detecting an energy level in the received signal corresponding to the second frequency;
- subtracting means for producing a difference signal by subtracting the energy level corresponding to the second frequency from the energy level corresponding to the first frequency;
- smoothing means for averaging a number of sequential difference value samples in order to generate an average value sample having a sign value;
- and
- window decoding means for monitoring a window of a number of sequential average value samples in order to generate a binary data signal matching the sign value of each of the average value samples.
Dependencies are inferred from the claim text.