SPREAD SPECTRUM CHANNEL MEASUREMENT INSTRUMENT

Transcription

1 SPACE SPREAD SPECTRUM CHANNEL MEASUREMENT INSTRUMENT Satellite communications, earth observation, navigation and positioning and control stations indracompany.com

2 SSCMI SPREAD SPECTRUM CHANNEL MEASUREMENT INSTRUMENT An innovative solution for high accuracy channel measurement Introduction The Spread Spectrum Channel Measurement Instrument (SSCMI) provides an innovative solution for high accuracy channel measurement characterization that can be performed in presence of interfering signals. The product is conceived for satellite operators to allow them to carry out in orbit test measurements while in operation, that is, without requiring to shutdown traffic carriers transmission as in the case of classical IOT measurement procedures. System overview The spread spectrum modem measurement concept is based on a mechanism that uses Spread Spectrum (SS) signals for the in orbit test transponder characterization. These spread spectrum signals exhibit a low-power spectral density, that causes no measurable degradation on the performance of the traffic signal transmitted in the same band. The procedure involves the transmission of two carriers simultaneously: The reference carrier, fixed to one frequency and continuously being transmitted and received to compensate for the propagation and satellite doppler effects The sounding carrier, which is swept over the measurement bandwidth SSCMI

3 Highlights High precision and accuracy instrument for channel measurement Channel characterization in presence of high power interfering signals Satellite transponder characterization during in orbit test campaigns Transponder characterization in presence of payload carriers, not requiring to shutdown the traffic Frequency response measurement: group delay accuracy of 1 ns and magnitude accuracy of 0.1 db Absolute transmitter to receiver delay measurement up to 1 ns accuracy, applicable for high accuracy satellite round trip delay Precision frequency error measurement, useful to calibrate transponder converter frequency stability Open and closed loop modes of operation Monitoring and control interface of IP Ethernet RJ45 Low rate data for command and control in case of open loop Measurements A monitoring and control application controls the instrument operation and allows to carry out systematic measurements during long periods of time, allowing to detect possible deviations of the transponder characteristics. Frequency response measurement Flexible selection of measurement parameters for each frequency point or band Measurements integrity provided simultaneous with the real measurements Configured measurement duration or controlled using measurements integrity TWTA characteristics computation from magnitude measurement Procedure to measure up to 200 MHz bands, divided in sub-bands of 40 MHz Round trip delay Maximum delay accuracy in closed loop mode Open loop mode accuracy depending on GPS receiver generated clock stability High accuracy frequency error measurement in presence of doppler Specifications MEASUREMENT Measurement bandwidth Frequency resolution Group delay accuracy Magnitude accuracy Minimum signal to traffic ratio Frequency error measurement resolution Delay accuracy (for round trip delay) INTERFACE Monitoring and control Data interface IF interface External frequency reference 40 MHz 500 KHz 1 ns 0.1 db -30 db for 20 Mchip/s 1 Hz 1 ns Ethernet RJ45 Serial RS 232 C 70 MHz, 40 MHz bandwidth 10 MHz high quality, 1 PPS signal SPACE

4 System specification Measurement waveform Spread spectrum QPSK Chip Rates Reference carrier Sounding carrier Processing gain Data transmission capacity 10, 20 Mchip/s 0.5, 1, 2.5 Mchip/s Up to 45 db Up to 750 bps Modes of operation Closed Loop Open Loop Transmitter and receiver at same location Maximum accuracy Transmitter and receiver at different locations A GPS receiver is used for measurement synchronization SATELLITE Propagation effects Propagation effects Transmition station Reception station Indra spread spectrum channel measurement instrument Reference transmitter Sounding transmitter Reference receiver Sounding receiver 70 MHz (Typical) MHz Frequency error round trip delay Frequency response (Magnitude group delay) SPACE

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