Multiport Amplifier Calibration Using Below-Noise Spread Spectrum
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Solution Overview
Problem
Communication satellites, particularly beamforming satellites, face calibration drift issues over time due to harsh space conditions, requiring frequent recalibration to maintain signal integrity and beam formation accuracy.
Innovation Solution
The implementation of a spread spectrum calibration signal with a power level below the thermal noise floor allows for continuous calibration of satellite channels during active operation, using probes to inject and extract the signal across multiple channels, and calibrating relative path-to-path differences to reduce calibration frequency and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional calibration methods are used for satellite channels, then calibration can be performed, but it requires frequent recalibration due to calibration drift in harsh space conditions, disrupting user signals and increasing operational complexity
Solution Approach 1:
The patent applies preliminary action by pre-calibrating the relative path-to-path differences between channels during manufacturing or initial setup. This pre-calibration creates a stable reference framework that remains valid over time despite harsh space conditions, eliminating the need for frequent recalibration and allowing only absolute calibration drift to be corrected during operation.
Solution Approach 2:
The patent extracts the calibration process into two separate components: relative path-to-path difference calibration (done preliminarily and fixed) and absolute calibration drift correction (done continuously or frequently). By separating these functions, the system avoids the need for frequent complete recalibrations, reducing operational disruption and time loss.
2Ease of operation
If spread spectrum calibration signals are injected into satellite channels, then calibration can be performed during active operation without disrupting user signals, but the calibration signal power level must be below the thermal noise floor, requiring precise signal injection and extraction
Solution Approach 1:
The patent uses spread spectrum calibration signals as an intermediary that operates below the thermal noise floor, allowing calibration to proceed without interfering with user signals. The spread spectrum technique disperses the calibration signal energy across a wide frequency band, making it indistinguishable from noise to user receivers while still detectable through correlation processing at the calibration receiver.
Solution Approach 2:
The patent changes the power level parameter of the calibration signal to be below the thermal noise floor, enabling simultaneous operation with user signals. This parameter change, combined with spread spectrum modulation, allows the calibration signal to be injected continuously without causing interference, while still being measurable through signal processing techniques.
3Reliability
If complete channel calibration is performed frequently, then signal integrity can be maintained, but operational complexity and cost increase due to hardware specifications and recalibration requirements
Solution Approach 1:
The patent segments the calibration process into two distinct parts: relative path-to-path difference calibration (performed once preliminarily) and absolute calibration drift correction (performed as needed). This segmentation reduces the complexity of frequent complete calibrations by maintaining a stable relative reference framework, thereby reducing hardware specifications and operational complexity while maintaining signal integrity.
Data Source
AI summary
Beamforming channels of a satellite are calibrated using a low power, spread spectrum calibration signal. The power of the calibration signal is below the noise level of a user signal in an active channel, allowing channels to be calibrated while active. When calibrating the transmit side circuitry, a two-stage calibration can be used, first calibrating the output hybrid matrix, then calibrating the whole of the transmit side. To improve performance, the dwell time spend calibrating a channel can be based on the power of the user signal in the channel. A transmit probe can be used to inject a calibration signal into the receive antennae and a receive probe can be used to extract the calibration signal from the transmit antennae. To reduce frequency of calibrations, the calibrations can be based on path-to-path differences. These techniques are also applied to multiport amplifiers (MPAs).