Method and system for digital modulation for burst mode applications

• US 20030174784A1
• Filed: 12/26/2002
• Published: 09/18/2003
• Est. Priority Date: 12/26/2001
• Status: Abandoned Application

• Current Assignee: Spacebridge Semiconductor Corporation (Advantech AMT, Inc.)
• Original Assignee: Spacebridge Semiconductor Corporation (Advantech AMT, Inc.)
• Inventors: Samarasooriya, Vajira N. S., Lee, Din, Johnson, Eric, Wood, Robert
• Application Number:
  US10/327,931
• Publication Number:
  US 20030174784A1
• Time in Patent Office: Days
• US Class Current: 375/308
• CPC Class Codes: H04B 1/7136 Arrangements for generation of hop frequencies, e.g. using a bank of frequency sources, using continuous tuning or using a transform
• CPC Class Codes: H04B 2001/71365 using continuous tuning of a single frequency source
• CPC Class Codes: H04B 7/18517 Transmission equipment in earth stations

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.

Claims

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.