Reflection-Based RF Phase Shifter with Tweak Bits
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Solution Overview
Problem
Existing RF phase shifters face challenges in achieving digitally controlled multiple equidistant phase shifts with uniformly increasing capacitance values, which are affected by loading and the ON/OFF states of reactive elements, leading to non-uniform phase shift increments.
Innovation Solution
The use of multiple FET-based switchable reactive elements in a thermometric fashion with a hybrid coupler, allowing for controlled phase shifts through sequential additive/subtractive operations, and the incorporation of tweak bits for fine-tuning and compensating for manufacturing variations, enables the generation of multiple equidistant phase shifts and extended range phase shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple reactive elements are used to achieve digitally controlled phase shifts, then the phase shift range is improved, but the uniformity of phase shift increments deteriorates due to loading effects and ON/OFF states of reactive elements
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the capacitance values of reactive elements based on their ON/OFF states and loading conditions. The controller modifies the capacitance parameters to compensate for non-uniformity, ensuring equidistant phase shifts across the full phase shift range while maintaining adaptability.
2Extent of automation
If reactive elements are switched ON or OFF to control phase shift, then the digital control capability is improved, but the phase error increases due to non-uniform capacitance changes
Solution Approach 1:
The patent implements feedback by having the controller monitor the actual phase shifts produced by switching reactive elements and adjusting the capacitance values accordingly. This closed-loop approach compensates for non-uniform capacitance changes, reducing phase error while preserving digital control capability.
Solution Approach 2:
The patent applies dynamics by making the capacitance values of reactive elements dynamically adjustable rather than fixed. The controller continuously adapts the capacitance parameters based on the switching states and loading conditions, enabling precise phase control that minimizes phase error across all digital control states.
3Device complexity
If standard reflective terminating circuits are used, then the circuit simplicity is improved, but the performance consistency across process variations deteriorates
Solution Approach 1:
The patent applies dynamics by transforming static reflective terminating circuits into dynamically adjustable circuits. The reactive elements can change their capacitance values in response to process variations, maintaining performance consistency without significantly increasing circuit complexity.
Solution Approach 2:
The patent uses parameter changes to compensate for process variations by adjusting the capacitance values of reactive elements. This allows the circuit to maintain consistent performance across different manufacturing processes while retaining the simplicity of the basic reflective terminating circuit structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces root-mean-square (RMS) phase error, optimizes frequency band performance, compensates for process variations, and provides a broader range of phase shifts, enhancing the overall system performance of RF phase shifters.
Implementation Method 1
It is a type of directional coupler where the input power is equally divided between two output ports by electromagnetic coupling
Implementation Method 2
The reflective terminating circuits connected to the Direct Port and the Coupled Port provide reflections of an input signal presented at the Input Port which cancel on the Input Port and sum to a phase-shifted version of the input signal on the Isolated Port
Data Source
AI summary
Programmable multi-reflective phase shifters which provide reduced root-mean-square phase error, can be optimized for a desired frequency band, can compensate for process variations arising during manufacture, and can help offset system level performance shortfalls. Embodiments include a hybrid coupler (e.g., a Lange hybrid coupler) in combination with a multi-reflective reactance-based terminating circuit with a number of different configurations that permit various modes of operation, including a thermometric mode, a phase overlap mode with interstitial phase shift states, an extended range phase shift mode, and a “tweak bit” mode. A number of programmable or selectable RF phase shifters can be series or parallel connected to provide a desired gamut of phase shift.