Baseband Phase Rotation for Transmit Diversity Signal Quality
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Solution Overview
Problem
Existing wireless communication systems face challenges in providing effective transmit diversity, particularly at the edge of a cell, due to multipath phenomena and limited phase rotation accuracy when performing phase rotation at radio frequency, which can degrade signal quality and increase power consumption.
Innovation Solution
Implementing phase rotation at baseband frequency for transmit diversity by using a signal selector within the diversity transmit signal path to rotate the phase of the primary transmit signal, allowing for precise control of phase differences between the primary and diversity transmit signals, thereby enhancing signal quality and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase rotation is performed at radio frequency, then transmit diversity can be implemented, but phase rotation accuracy degrades and power consumption increases
Solution Approach 1:
The patent introduces a baseband signal as an intermediary to perform phase rotation before RF transmission. Instead of rotating phase directly at RF frequency, the system rotates the baseband signal's phase and then modulates it to RF, achieving accurate phase control with lower power consumption since baseband operations require less energy than high-frequency RF operations.
Solution Approach 2:
The patent replaces the mechanical/electrical phase rotation mechanism at RF frequency with a digital/baseband phase rotation approach. By performing phase rotation in the baseband domain using digital signal processing rather than analog RF phase shifters, the system achieves higher precision and lower power consumption.
2Reliability
If phase rotation is performed at radio frequency, then transmit diversity can be implemented, but signal quality degrades due to multipath phenomena
Solution Approach 1:
The patent applies preliminary phase rotation to the baseband signal before RF modulation and transmission. By pre-rotating the phase of the baseband signal, the system prepares the signal to counteract expected multipath effects, ensuring that when the signal experiences multipath propagation, the diversity combining at the receiver can effectively recover the original signal with higher quality.
3Measurement precision
If phase rotation accuracy is increased at radio frequency, then transmit diversity performance improves, but device complexity increases
Solution Approach 1:
The patent uses baseband signal processing as an intermediary to achieve accurate phase rotation without complex RF hardware. Digital baseband processing requires simpler, more integrated circuits compared to high-precision RF phase shifters, reducing overall device complexity while maintaining or improving phase rotation accuracy.
Data Source
AI summary
An apparatus for implementing phase rotation at baseband frequency for transmit diversity may include a primary transmit signal path and a diversity transmit signal path. Both the primary transmit signal path and the diversity transmit signal path may receive a primary transmit signal. A signal selector within the diversity transmit signal path may perform phase rotation with respect to the primary transmit signal while the primary transmit signal is at a baseband frequency, thereby producing a diversity transmit signal.