Phase Synchronization in RF Transmitters Using Local Oscillators
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Solution Overview
Problem
Conventional electronic systems with multiple transmission paths face challenges in phase synchronization due to the use of separate local oscillators, leading to misalignment of signal phases, which can result in interference between antenna elements.
Innovation Solution
The system employs separate local oscillators for each transmission path, with a phase control input to adjust the phase of RF signals, and a processor to determine and synchronize the relative phase difference between these oscillators, using directional couplers to sample RF signals and generate phase components for alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If separate local oscillators are used for multiple transmission paths, then device complexity is reduced and routing is simplified, but phase synchronization between transmission paths deteriorates
Solution Approach 1:
A receive path is introduced as an intermediary to measure the phase difference between separate local oscillators. The receive path receives RF samples from transmission paths and generates baseband signals that reveal the relative phase information, enabling synchronization without requiring complex direct measurement circuits in the transmission paths.
Solution Approach 2:
The system implements feedback by using the measured phase difference information to adjust and synchronize the phases of separate local oscillators. The processor determines phase differences from baseband signals and uses this information to control the local oscillators, creating a closed-loop system that maintains phase alignment despite using separate oscillators.
2Manufacturing precision
If a single local oscillator is shared across multiple transmission paths, then phase synchronization is maintained, but device complexity increases and carrier leakage occurs
Solution Approach 1:
The receive path serves as a mediator that enables phase synchronization between independent local oscillators without requiring them to be physically coupled or routed through complex interconnections. By measuring phase differences through the receive path and using this information for control, the system achieves synchronization equivalent to shared oscillators but with independent, simpler routing.
3Object-generated harmful factors
If separate local oscillators are used in direct conversion transmitters, then carrier leakage is reduced, but phase synchronization between transmission paths deteriorates
Solution Approach 1:
The system uses feedback control where the receive path measures phase differences between separate local oscillators and this measurement is fed back to adjust the oscillator phases. This closed-loop approach maintains phase alignment accuracy while preserving the benefit of separate oscillators that reduces carrier leakage in direct conversion transmitters.
Solution Approach 2:
The receive path acts as an intermediary measurement system that enables phase synchronization without requiring direct physical coupling between local oscillators. This indirect measurement approach allows separate oscillators to be used (reducing carrier leakage) while still achieving phase alignment through the phase difference information obtained via the receive path.
Data Source
AI summary
Apparatus and methods are disclosed related to phase synchronization in transmitters. One such apparatus includes a wireless transmitter with two or more separate and unrelated local oscillators. The apparatus can provide RF signals to multiple antenna elements, which can be implemented in systems such as beamforming systems or multiple input multiple output (MIMO) systems. A phase difference between local oscillators is determined using outputs of receivers. The phase difference can be used to adjust a phase of signals associated with one or more of the local oscillators, such that the phase of each signal provided to the multiple antenna elements can be aligned.