US5208829A — Communication satellite system having an increase…

Claim 1

Independent Claim 135 words

An earth station transmitter for transmitting a spread spectrum modulated data signal to a satellite comprising: a source of data signals; a spreading sequence generator for generating a spreading signal at a spreading signal chip rate f(c) synchronized with said data signals; a multiplier for multiplying said data signals with said spreading signal to produce a spread spectrum signal having an amplitude versus frequency function defined by ##EQU5## where X is frequency; a filter having an amplitude versus frequency characteristic defined by a 6-pole Butterworth function and by X/SIN X for filtering said spread spectrum signal to thereby produce a filtered spread spectrum signal which is amplitude normalized over at least a portion of said spread spectrum signal bandwidth; and, a converter for frequency upconverting said filtered spread spectrum signal for transmission to the satellite.

Claim 2

Dependent Claim 135 words

An earth station transmitter for transmitting a spread spectrum modulated data signal to a satellite comprising: a source of data signals; a spreading sequence generator for generating a spreading signal at a spreading signal chip rate f(c) synchronized with said data signals; a multiplier for multiplying said data signals with said spreading signal to produce a spread spectrum signal having an amplitude versus frequency function defined by ##EQU5## where X is frequency; a filter having an amplitude versus frequency characteristic defined by a 6-pole Butterworth function and by X/SIN X for filtering said spread spectrum signal to thereby produce a filtered spread spectrum signal which is amplitude normalized over at least a portion of said spread spectrum signal bandwidth; and, a converter for frequency upconverting said filtered spread spectrum signal for transmission to the satellite.

Claim 3

Dependent Claim 15 words

The earth station transmitter of claim 1 wherein said filter comprises a digital FIR filter.

Claim 4

Dependent Claim 27 words

The earth station transmitter of claim 1 wherein said Butterworth function has a passband ripple of less than 1 db over said portion of said signal bandwidth.

Claim 5

Dependent Claim 29 words

The earth station transmtter of claim 2, wherein said filter is a lowpass filter having a 3 db bandwidth substantially one half of the spreading signal chip rate f(c).

Claim 6

Dependent Claim 105 words

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.

Claim 7

Dependent Claim 105 words

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.

Claim 8

Dependent Claim 53 words

The satellite receiver of claim 5 wherein said demodulator means comprises: analog to digital converter means connected to digitize each of said I and Q signals; and, digital circuit means connected to receive digitized data signals from said analog to digital converter means, and provide therefrom a signal proportional to the data signal.

Claim 9

Dependent Claim 78 words

The satellite receiver of claim 6 wherein said baseband signal processing means comprises: a power divider connected to receive said intermediate frequency signal, and dividing said intermediate frequency signal into two signals; first and second mixers connected to receive said two signals; and, a voltage controlled oscillator means providing first and second reference signals having a phase quadrature relationship to said first and second mixers, whereby said first and second mixers produce first and second quadrature detected signals.

Claim 10

Dependent Claim 23 words

The satellite communication system of claim 7 wherein said FIR filter has an impulse response time inverse to said analog filter impulse response.

Claim 11

Dependent Claim 57 words

The satellite receiver of claim 5 wherein said demodulator means comprises: a programmable logic array, said array being programmable from first and second sets of configuration data to produce either a spread spectrum demodulator, or a non-spread spectrum demodulator; and, a microprocessor connected to said programmable logic array to supply programming data to said programmable logic array.

Claim 12

Dependent Claim 37 words

The satellite receiver of claim 7 wherein said programmable logic array supplies a control signal to said voltage controlled oscillator for maintaining said oscillator first and second reference signals in phase synchronism with said power divider signals.

Claim 13

Dependent Claim 33 words

The satellite communication system of claim 9 wherein said first and second filter means comprise first and second analog filters having an amplitude frequency response equal to said FIR filter amplitude frequency response.

Claim 14

Dependent Claim 195 words

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.

Claim 15

Dependent Claim 195 words

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.

Claim 16

Dependent Claim 122 words

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.

Claim 17

Dependent Claim 122 words

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.

Claim 18

Dependent Claim 89 words

The receiver of claim 13 wherein said demodulation means comprises: a microprocessor system for storing first and second sets of configuration data, one set of configuration data defining a despreading demodulator, the other set of data defining a demodulator for processing a data signal which is not spread; and, a programmable logic array for receiving one or the other of said sets of configuration data, said logic array providing first and second demodulators for demodulating either a spread spectrum data signal or a data signal which is not spread.

Claim 19

Dependent Claim 23 words

The receiver of claim 14, wherein said demodulator processing a data signal which is not spread is a binary phase shift key demodulator.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1996-05-03	1996-11-02	1997-05-04	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2000-05-03	2000-11-02	2001-05-04	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2004-05-03	2004-11-02	2005-05-04	$7700.00	Window Closed / Lapsed

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

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