Method and system for digital modulation for burst mode applications
First Claim
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1. A digital demodulator for a satellite communication system, comprising:
- a QPSK mapper for receiving an input analog signal and mapping input signal to I and Q data streams, respectively;
a pair of root raised cosine filters for filtering the I and Q data streams, respectively;
a corresponding pair of interpolators for interpolating the filtered data streams;
a digital up-converter, receiving sine and cosine signals from a numerically controlled oscillator, for up-converting the interpolated signals; and
a pair of digital to analog converters for converting the up-converted digital signals to analog signals.
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Abstract
A method and system for digital modulation, particularly in burst mode applications, using a root raised cosine filter operating at a rate of four-samples-per-symbol. The raised cosine pulse-shaped baseband signal is interpolated in order to achieve a sampling rate of 44.96 MHz at the digital up-converter. The two-stage interpolation provides an overall interpolation ratio of 20. The digital upconverter performs the frequency adjustments for channelization and Doppler correction.
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Citations
1 Claim
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1. A digital demodulator for a satellite communication system, comprising:
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a QPSK mapper for receiving an input analog signal and mapping input signal to I and Q data streams, respectively;
a pair of root raised cosine filters for filtering the I and Q data streams, respectively;
a corresponding pair of interpolators for interpolating the filtered data streams;
a digital up-converter, receiving sine and cosine signals from a numerically controlled oscillator, for up-converting the interpolated signals; and
a pair of digital to analog converters for converting the up-converted digital signals to analog signals.
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Specification