System and method for bi-phase modulation decoding

Abstract

One embodiment of the invention includes a decoder system (10) that decodes a bi-phase modulated signal (BI-F_IN) to generate an output code. The system includes a first filter (12) associated with a first logic state configured to generate a first dot product of a plurality of consecutive digital samples of the bi-phase modulated signal and a respective plurality of tap weights of the first filter. The system also includes a second filter (14) associated with a second logic state configured to generate a second dot product of the plurality of consecutive digital samples of the bi-phase modulated signal with a respective plurality of tap weights of the second filter. The system further includes a comparator (16) configured to compare the first and second dot products and to provide the output code as a bit having one of the first logic state and the second logic state based on the comparison.

Description

technical field [0001] The present invention relates generally to communications, and in particular to systems and methods for bi-phase modulation decoding. Background technique [0002] One example of a coding scheme utilized for transmitting data is bi-phase modulation. Each bit-window / bit-window (i.e. period) of a biphase modulated signal represents a single logical bit, where each bit-window begins with a logic state transition. A logic low is represented by a substantially constant logic state throughout the bit window, while a logic high is represented by an additional logic state transition in the approximate center of the bit window. [0003] Any of a variety of different decoding algorithms can be implemented to decode the biphase modulated signal when the amplitude of the biphase modulated signal is sufficient. However, when the signal amplitude is reduced, eg due to filtering and / or transmission medium loss, decoding a biphase modulated signal may be difficult b...

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Problems solved by technology

However, when the signal amplitude is reduced, e.g. due to filtering and / or transmission medium losses, decoding biphase modulated signals can be difficult based on noise that is more likely to present as valid logic transitions

Additionally, in some biphase modulated signal transmission implementations, there may be no external clock to align the phase and / or frequency of the biphase modulated signal, which may further complicate the decoding of the biphase modulated signal

Furthermore, when the biphase modulated signal is low-pass filtered, for example by removing the carrier frequency, the amplitude of a logic high code may be attenuated more than a logic low code, which is half the frequency of a logic high code

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