Communication satellite system having an increased power output density per unit of bandwidth

A satellite earth station receiver system for receiving a spread spectrum modulated data signal spectrum shaped to have a maximally flat Butterworth filtered characteristic comprising:

• a down converter for frequency translating said modulated spread spectrum signal to an intermediate frequency signal;
• a baseband signal processor for dividing said intermediate frequency signal into I and Q phase quadrature signals;
• first and second filters for filtering respective of said I and Q signals, said filters having an impulse response time inverse to said Butterworth filtered characteristic;
• and,
• demodulator means connected to receive said I and Q signals demodulating data contained in said spread spectrum modulated data signal.

A satellite communications system comprising:

• means for producing a spread spectrum signal from a data signal with a spreading signal having a chip rate f(c) and having an amplitude of ##EQU6## where X is a frequency;
• an FIR filter for producing from said spread spectrum signal a signal having a flat amplitude function over a substantial portion of said filter 3 db bandwidth which is substantially equal to one half of said spreading signal chip rate f(c);
• modulation means for modulating said signal having said substantially flat amplitude function on a carrier signal;
• and,
• antenna means for transmitting said carrier signal to a satellite, wherein it is rebroadcast on a different carrier signal;
• and,
• a receiver including a down converter for producing an intermediate frequency signal from said satellite rebroadcast carrier signal;
• a baseband demodulation means for removing said spread spectrum signal from said intermediate frequency signal, producing I and Q quadrature baseband signals;
• first and second filter means for filtering said I and Q signals, said filter means having an amplitude frequency response substantially identical to said FIR filter response;
• and,
• demodulator means for removing said data signal from said I and Q signals.

In a satellite communications system for transmitting and receiving a spread spectrum data signal which is filtered by an FIR filter to spectrally shape said spread spectrum data signal, a receiver comprising:

• a down converter for converting a carrier signal having said spread spectrum data signal modulated thereon to an intermediate frequency signal;
• a baseband demodulator means for removing said spread spectrum data signal from said intermediate frequency signal, and forming I and Q quadrature signals;
• first and second analog Butterworth filters for filtering said I and Q signals having an amplitude frequency response matched to said FIR filter which spectrally shapes said spread spectrum data signal;
• and,
• demodulation means for despreading said spread spectrum signal and producing therefrom said data signal.