Adaptive I/Q Re-Modulation for Asynchronous Signal Conversion
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Solution Overview
Problem
Conventional microwave communication systems face signal-to-noise ratio (SNR) degradation due to the lack of synchronization between the receiver-side and transmitter-side I/Q demodulators, leading to constellation spin and errors in wireless communications.
Innovation Solution
A signal receiving system comprising an I/Q demodulator, an I/Q signal adjustor, and an I/Q modulator that adaptively adjusts the in-phase (I) and quadrature (Q) signals to compensate for synchronization errors, using a feedback loop to continuously correct for errors and improve SNR without requiring synchronization between the receiver and transmitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional heterodyne systems use double downconversion to translate microwave signals to intermediate frequency, then signal translation is achieved, but signal-to-noise ratio degradation occurs due to lack of synchronization between receiver and transmitter oscillators
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors the received signal quality and adjusts the local oscillator frequency to track and compensate for transmitter frequency variations. This closed-loop feedback approach maintains synchronization without requiring complex external synchronization infrastructure, thereby improving SNR while avoiding excessive system complexity
Solution Approach 2:
The receiver system performs self-synchronization by using its own received signal to generate the reference frequency for demodulation. The system extracts timing and frequency information from the incoming signal itself, eliminating the need for external synchronization sources and reducing system complexity while maintaining reliable signal-to-noise ratio
2Device complexity
If the receiver uses a local oscillator asynchronous to the transmitter oscillator, then device complexity is reduced, but constellation spin and demodulation errors occur
Solution Approach 1:
The patent employs dynamic frequency adjustment where the local oscillator frequency is continuously adapted to match the transmitter frequency. This dynamic tracking approach allows the system to operate without fixed synchronization while maintaining demodulation accuracy, effectively resolving the contradiction between device complexity and measurement precision
Solution Approach 2:
The system changes the local oscillator frequency parameter in real-time to track transmitter frequency variations. By dynamically adjusting this critical parameter based on received signal characteristics, the system maintains accurate demodulation without requiring complex synchronization hardware
Data Source
AI summary
Various embodiments provide for systems and methods for signal conversion of one modulated signal to another modulated signal using demodulation and then re-modulation. According to some embodiments, a signal receiving system may comprise an I/Q demodulator that demodulates a first modulated signal to an in-phase (“I”) signal and a quadrature (“Q”) signal, an I/Q signal adjustor that adaptively adjusts the Q signal to increase the signal-to-noise ratio (SNR) of a transitory signal that is based on a second modulated signal, and an I/Q modulator that modulates the I signal and the adjusted Q signal to the second modulated signal. To increase the SNR, the Q signal may be adjusted based on a calculated error determined for the transitory signal during demodulation by a demodulator downstream from the I/Q modulator.