Mobile Terminal Frequency Compensation for Doppler and Oscillator Error
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Solution Overview
Problem
High-bandwidth satellite communication systems face challenges in compensating for both oscillator errors and Doppler shifts in mobile terminals, which are additive and asymmetric, complicating frequency correction and increasing error rates due to the use of less stable, lower-cost oscillators.
Innovation Solution
A method and system for mobile terminals that involve an acquisition mode to determine and compensate for oscillator errors and Doppler shifts separately, using feedback from the communication system to iteratively adjust frequency corrections in a tracking mode, allowing the use of less expensive and smaller oscillators while maintaining communication quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If very accurate, stable oscillators are used in mobile terminals, then oscillator frequency drift errors are removed, but cost, size, and power consumption increase
Solution Approach 1:
The patent segments the frequency error into two distinct components: oscillator error and Doppler shift error. By separating these errors and applying different correction procedures to each, the system can use a lower-cost oscillator while maintaining overall frequency accuracy through software-based compensation algorithms that address each error source independently
Solution Approach 2:
The patent changes the approach from hardware-based frequency stability (relying on expensive oscillators) to a software-based parameter correction approach. By measuring and compensating for oscillator drift through feedback loops and calibration procedures, the system achieves frequency stability through parameter adjustment rather than hardware quality alone
2Ease of manufacture
If conventional oscillators are used without separate compensation, then cost is reduced, but frequency correction accuracy deteriorates due to additive oscillator errors and Doppler shift
Solution Approach 1:
The patent implements feedback mechanisms where the mobile terminal measures its own frequency errors and receives feedback from the base station about received signal frequency accuracy. This feedback is used to iteratively adjust and refine the separate oscillator and Doppler compensation parameters, maintaining high frequency correction accuracy even with conventional oscillators
Solution Approach 2:
The patent introduces an intermediary correction algorithm that acts as a mediator between the raw oscillator output and the final transmitted signal. This software intermediary separately calculates and applies corrections for oscillator drift and Doppler shift, enabling accurate frequency correction without requiring high-quality hardware oscillators
3Measurement precision
If asymmetric error compensation is applied to both oscillator errors and Doppler shift, then frequency correction accuracy is improved, but device complexity increases
Solution Approach 1:
The patent segments the complex compensation problem into two manageable sub-problems: oscillator error correction and Doppler shift correction. Each segment has its own dedicated algorithm and parameter set, making the overall complex task more tractable and implementable in software without requiring excessive computational resources
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
Enables accurate frequency correction and reduced error rates in high-bandwidth satellite communications by effectively compensating for both oscillator errors and Doppler shifts, even with less stable oscillators, thereby improving communication quality and reducing costs.
Implementation Method 1
A mobile terminal includes an oscillator, a receiver circuit configured to downconvert signals received from a communication system using a frequency signal from the oscillator, and a transmit circuit configured to upconvert a baseband signal to a transmission frequency using the frequency signal from the oscillator
Implementation Method 2
a receiver circuit configured to downconvert signals received from a communication system using a frequency signal from the oscillator
Implementation Method 3
a transmit circuit configured to upconvert a baseband signal to a transmission frequency using the frequency signal from the oscillator
Implementation Method 4
Mobile terminals in high-bandwidth communication systems experience additional frequency errors due to the Doppler shift caused by movements of the mobile terminal with respect to the communication system
Data Source
AI summary
Systems and methods are described herein for multi-mode compensation of frequency errors within signals transmitted and received by a mobile terminal. The frequency error can be due to Doppler shift and oscillator error, which introduce opposite frequency shifts. In an acquisition mode, the mobile terminal initially compensates for the oscillator error while transmitting a signal to a communication system that contains the Doppler shift. Upon receiving a message from the communication system indicating the Doppler shift contained in the transmit signal, the mobile terminal can then switch to a tracking mode that can compensate for both Doppler shift and oscillator error.