Patent EP0505771A1 successfully refreshed from Google Patents.
EP0505771A1
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Communication satellite system having an increased power output density per unit of bandwidth
Assignee: Raytheon Co
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Filing: 1992-03-03
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Granted: —
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Expires: 2012-03-03
Abstract
Abstract A satellite communication system for providing maximum power output in a spread spectrum signal transmission is disclosed. Spectral shaping is provided at a satellite transmitter (Q) to shape a spread spectrum so that over a bandwidth of interest, the spectrum has a maximally flat characteristic. By maximizing the spectrum amplitude flatness, the required bandwidth power density limitation imposed to prevent interference with other communication facilities is maintained. In each earth station (10) receiving the transmission from the satellite, filtering of the demodulated baseband satellite signal is provided such that the spectrum is restored to its original shape. The filters (31,32) on the receive side may be analog, having the same amplitude-frequency function as the transmitter spectrum shaping filter, but having an inverse phase response. This ensures a matched filter condition at transmitter and receiver, maximizing signal transfer. A programmable demodulator (35) is provided to select a demodulation mode. The programmable demodulator may receive microcode from a microprocessor (36) configuring the PLA into a despreader demodulator (35) for spread spectrum applications or into a straight BPSK demodulator where the data signal has not been subject to spectrum spreading.
Inventors
- 👤 Mohammad Soleimani
- 👤 Sasan Rostami
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 05:17
CPC Classifications
H; H04; H04B; H04B7/00; H04B7/14; H04B7/15; H04B7/204; H04B7/216; H04B1/00; H04B1/69; H04B1/707; H04L; H04L27/00; H04L27/18; H04L27/22; H04L27/227; H04L27/2271; H04L27/2273; H04L27/0014; H04L2027/0024; H04L2027/0026; H04L2027/0028; H04L2027/0044; H04L2027/0053; H04L2027/0057
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
127 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 where X is frequency; a filter having an amplitude versus frequency characteristic defined 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, means for frequency upconverting said filtered spread spectrum signal for transmission to the satellite.
Claim 2
Dependent Claim
24 words
The earth station transmitter of claim 1 wherein said filter comprises a digital FIR filter which produces a maximally flat 6-pole Butterworth filter function.
Claim 3
Dependent Claim
30 words
The earth station transmitter of claim 2 wherein said Butterworth filter function has a passband ripple of less than 1 dB over said amplitude normalized portion of said signal bandwidth.
Claim 4
Dependent Claim
31 words
The earth station transmtter of claim 3, wherein said digital FIR filter is a lowpass filter having a 3 db bandwidth substantially one half of said spreading signal chip rate f(c).
Claim 5
Dependent Claim
113 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 spread spectrum modulated data signal to an intermediate frequency signal; a baseband signal processing means for dividing said intermediate frequency signal into I and Q phase quadrature signals; first and second filters for filtering of said I and Q signals, respectively, said filters having an impulse response time inverse to said Butterworth filtered characteristic; and, demodulator means connected to receive said filtered I and Q signals for demodulating said spread spectrum modulated data signal to produce an output data signal therefrom.
Claim 6
Dependent Claim
56 words
The satellite receiver of claim 5 wherein said demodulator means comprises: analog to digital converter means connected to digitize each of said filtered I and Q signals; and, digital circuit means connected to receive said digitized I and Q data signals from said analog to digital converter means, and to provide therefrom said output data signal.
Claim 7
Dependent Claim
60 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 control data to produce either a spread spectrum demodulator, or a non-spread spectrum demodulator; and, a microprocessor connected to said programmable logic array to selectively supply said control data to said programmable logic array.
Claim 8
Dependent Claim
84 words
The satellite receiver of claim 7 wherein said baseband signal processing means comprises: a power divider connected to receive said intermediate frequency signal, and divide said intermediate frequency signal into I and Q signals; first and second mixers connected to receive said I and Q signals, respectively; and, a voltage controlled oscillator means for 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 9
Dependent Claim
40 words
The satellite receiver of claim 8 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 I and Q signals.
Claim 10
Dependent Claim
205 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 where X is a frequency; an FIR filter for producing from said spread spectrum signal a filtered 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 filtered signal on a carrier signal to produce a modulated carrier signal; and, antenna means for transmitting said modulated carrier signal to a satellite for 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, and for producing I and Q quadrature baseband signals therefrom; first and second filter means for filtering said I and Q quadrature baseband signals, respectively, said first and second 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 quadrature baseband signals.
Claim 11
Dependent Claim
32 words
The satellite communications system of claim 10 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 12
Dependent Claim
29 words
The satellite communication system of claim 11 wherein said FIR filter has an impulse response time inverse to the impulse response time of said first and second analog filters.
Claim 13
Dependent Claim
127 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 therefrom; first and second analog Butterworth filters for filtering said I and Q quadrature signals, said first and second filters having an amplitude frequency response matched to said FIR filter which spectrally shapes said carrier signal; and, demodulation means for despreading said spread spectrum signal and producing therefrom said data signal.
Claim 14
Dependent Claim
90 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 selectively receiving one of said sets of configuration data, said logic array, thereby selectively providing first and second demodulator configurations for demodulating either a spread spectrum data signal or a data signal which is not spread.
Claim 15
Dependent Claim
26 words
The receiver of claim 14, wherein said demodulator configuration for processing a data signal which is not spread is a binary phase shift key demodulator configuration.
References Cited (Backward Citations)
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