Digital Variable Gain Mixer for Transmitter Power Control
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Solution Overview
Problem
Transceivers face challenges in reducing leakage currents from phase-lock loop (PLL) paths, which can introduce offset noise and violate output-offset suppression requirements, especially in linear transmitter architectures during switching between GMSK and 8-PSK modulation schemes.
Innovation Solution
A digital variable gain mixer is designed with multiple slices and a current density controller to adjust power output levels, using different control schemes for low and high ranges, and incorporating a commutating mixer to manage current density and slice enabling for efficient operation and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single control scheme is used for the entire power output range, then the design is simpler, but power consumption efficiency is reduced
Solution Approach 1:
The power output range is divided into two segments: low power range (first portion) and high power range (second portion). Each segment uses a different control scheme optimized for its specific power level, allowing the system to achieve better power efficiency without requiring a single complex control scheme to handle all power levels effectively.
2Power
If current density is increased to improve power output, then power output level increases, but unwanted coupling of LO signals increases
Solution Approach 1:
The mixer slice enabling is dynamically adjusted based on the desired power output level. At lower power levels, fewer mixer slices are enabled, reducing current density and minimizing LO signal coupling. As power output requirements increase, additional mixer slices are progressively enabled to increase power output while maintaining controlled current density levels.
3Power
If all mixer slices are enabled to maximize power output, then power output range is sufficient, but power consumption increases
Solution Approach 1:
Instead of enabling all mixer slices continuously, the system enables only the necessary number of mixer slices required to achieve the desired power output level. This partial action approach ensures sufficient power output range while minimizing power consumption by keeping unnecessary mixer slices disabled.
4Reliability
If mixer gain is controlled to reduce LO signal coupling, then output-offset suppression improves, but power output control flexibility is reduced
Solution Approach 1:
The system adds a new dimension to power output control by combining two independent control mechanisms: mixer gain control (affecting LO signal coupling and output-offset suppression) and mixer slice enabling control (affecting power output level). This multi-dimensional control approach allows simultaneous optimization of output-offset suppression and power output control flexibility.
Data Source
AI summary
A method includes controlling a mixer gain to provide a range of selected power output levels from the mixer using a first control scheme for a low portion of the range and using a second control scheme for a high portion of the range. Using the selected mixer gain, incoming baseband signals may be upconverted in the mixer to a transmission frequency and output from the mixer at the selected power output level.