Satellite Payload Characterization via Adjustable Thermal Noise
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Solution Overview
Problem
Current satellite in-orbit testing methods are limited by the need for ground stations to be positioned within the intersection of receive and transmit antenna coverage areas, leading to incomplete antenna characterization, increased complexity for multibeam or multi-frequency antennas, and interference with adjacent satellites due to high power spectral density test signals.
Innovation Solution
A method using a test thermal noise signal with adjustable power spectral density, generated by a ground station, to characterize the uplink receive antenna's radiation pattern and transponder performance, allowing for broader angular range characterization and reduced interference by matching the noise floor to the satellite's internal noise, thus enabling efficient characterization without requiring specific frequency coordination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If unmodulated carrier test signals are used, then the radiation pattern of the receive antenna can be tested, but the ground station must be positioned in the intersection of coverage areas which limits the angular range of characterization
Solution Approach 1:
The invention changes the test signal from an unmodulated carrier to a modulated carrier, and further to a spread spectrum modulated signal. This parameter change in the signal structure allows the ground station to transmit test signals that can be distinguished from noise across the entire angular coverage of the receive antenna, eliminating the need to be positioned in the intersection of coverage areas and enabling full angular range characterization.
2Adaptability or versatility
If multi-carrier test signals are used to test multibeam or multi-frequency receive antennas, then the operation of these complex antennas can be tested, but the complexity of the test system increases
Solution Approach 1:
The invention extracts the complexity from the ground-based test signal generation equipment and transfers it to the satellite payload itself. By using spread spectrum modulation with a pseudo-random code, the complex signal generation is performed by the satellite's own transponder, which then retransmits the modulated signal. This allows the ground station to test multibeam and multi-frequency antennas without requiring complex multi-carrier signal generation equipment.
3Measurement precision
If high power spectral density unmodulated carriers are transmitted for testing, then the test signal can be detected, but interference is created with adjacent operational satellites
Solution Approach 1:
The invention introduces spread spectrum modulation as an intermediary technique. The test signal is modulated with a wide-band pseudo-random code, which spreads the power spectral density over a wide frequency range. This reduces the peak spectral density to levels that do not interfere with adjacent satellites, while the correlation processing at the receiver recovers the test signal with the same detection capability as high-power unmodulated carriers.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for comprehensive characterization of satellite payloads in their service orbit, reducing testing time and complexity while minimizing interference with adjacent satellites, thereby facilitating more robust and efficient in-orbit testing.
Implementation Method 1
A method using a test thermal noise signal with adjustable power spectral density, generated by a ground station
Implementation Method 2
The payload of the satellite receives the unmodulated test signal via an uplink receive antenna
Implementation Method 3
the signal is propagated through the transponder and retransmitted to the ground station via a downlink transmit antenna
Data Source
AI summary
A method of characterizing the performance of the payload of a satellite in orbit is executed with the aid of a test ground station including first radio-frequency amplification means and a radio-frequency transmit ground antenna. The method includes a step of providing first amplification means that can be configured to generate at the input of the transmit ground antenna a wide-band test thermal noise the power spectral density of which can be adjusted to a test thermal noise reference power spectral density Dref so that the ratio of the test thermal noise spectral density received at the input of the transponder and that corresponds to it to the thermal noise floor spectral density generated by the satellite alone internally and the natural thermal noise of the Earth is greater than or equal to a first threshold Ds1 equal to 10 dB. An IOT system is configured to execute the method.