Cartesian Loop RF Transmitter Power Control With Feedback Attenuation
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Solution Overview
Problem
Cartesian feedback loop circuits in RF transmitters require high dynamic range output power, leading to increased circuit complexity and power consumption due to the need for variable gain up-mixers and down-mixers, which complicates power control and efficiency.
Innovation Solution
The implementation of a Cartesian loop circuit with a controller that adjusts the gains of the up-mixer and down-mixer based on power levels, using a feedback attenuator to control power at high powers and a reference signal amplifier at low powers, eliminating the need for additional amplifiers in the feedback path and reducing complexity and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If variable gain up-mixers and down-mixers are used to provide high dynamic range output power in Cartesian feedback loops, then power control capability is improved, but circuit complexity and power consumption increase
Solution Approach 1:
The patent divides the power control function into two separate segments: a feedback attenuator in the feedback path for high power control, and a reference signal amplifier in the forward path for low power control. This segmentation eliminates the need for variable gain mixers and reduces circuit complexity while maintaining full power control capability across the dynamic range.
Solution Approach 2:
The patent introduces intermediate components (feedback attenuator and reference signal amplifier) that mediate the power control function. These intermediaries handle the dynamic range requirement without requiring the main mixers to have variable gain, thereby simplifying the core mixing circuitry while still achieving the desired power control adaptability.
2Adaptability or versatility
If variable gain up-mixers and down-mixers are used to provide high dynamic range output power in Cartesian feedback loops, then power control capability is improved, but power consumption increases
Solution Approach 1:
The patent segments the power control function to use simpler, more energy-efficient components. The feedback attenuator (using passive attenuation) and reference signal amplifier (using fixed gain) consume significantly less power than variable gain mixers would require, while still providing the necessary power control adaptability across the full dynamic range.
Solution Approach 2:
The patent replaces expensive, high-power variable gain mixer components with cheaper, lower-power alternatives (attenuator and fixed gain amplifier). These simpler components achieve the same functional outcome with reduced power consumption, effectively trading component sophistication for energy efficiency.
3Power
If additional amplifiers are added to the feedback path to maintain high dynamic range, then output power range is improved, but device complexity increases
Solution Approach 1:
The patent extracts the dynamic range management function from the amplifier chain and places it in the feedback path as a dedicated attenuator. This extraction allows the main forward path amplifiers to operate at fixed, optimal gain settings, reducing their complexity while the feedback attenuator handles the dynamic range adjustment separately.
Solution Approach 2:
The feedback attenuator serves as an intermediary that manages the dynamic range requirement. By placing this attenuator in the feedback path, the patent allows the forward path amplifiers to be simpler fixed-gain devices, while the attenuator mediates the overall output power range requirement without adding complexity to the main signal path.
Data Source
AI summary
A Cartesian loop circuit includes a reference signal amplifier, a forward path coupled to the reference signal amplifier, a feedback path coupled to the forward path, and a controller. The forward path includes an up-mixer to up mix a forward path signal to a radio frequency signal. The feedback path includes a down-mixer to down mix a feedback signal to a frequency of a baseband reference signal inputted to the forward path. The feedback path provides the down-mixed feedback signal to the forward path. The controller is to perform power control at a low power by controlling a gain of the reference signal amplifier and is to perform power control at a high power by controlling a gain of the down-mixer. At the high power, the controller may perform power control by further controlling the gain of the up-mixer.