Programmable VVA and DSA Attenuation for Smooth RF Level Control
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Solution Overview
Problem
Conventional digital step attenuators (DSAs) face challenges in RF environments due to abrupt signal level changes, which can introduce errors, especially in complex modulation systems like QAM, and voltage variable attenuators (VVAs) struggle with determining economic attenuation ranges, requiring either small or large attenuation ranges for optimal performance.
Innovation Solution
A programmable voltage variable attenuator (VVA) with a dual-mode interface that digitally programs a multiple bit digital-to-analog converter (DAC) to control attenuation levels, allowing for selection among multiple analog, continuous attenuation ranges, and includes variable resistance elements controlled by a field effect transistor (FET) or diode, enabling fine, step-less adjustments and compatibility with different impedance systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If digital step attenuators (DSAs) are used to provide selectable attenuation levels, then discrete attenuation control is achieved, but abrupt signal level changes occur causing errors in complex modulation systems
Solution Approach 1:
The patent combines a digital step attenuator (DSA) and a voltage variable attenuator (VVA) into a single hybrid attenuator system. The DSA provides coarse discrete attenuation steps while the VVA provides continuous fine adjustment, merging both approaches to eliminate abrupt transitions and improve signal accuracy in complex modulation systems.
Solution Approach 2:
The total attenuation range is segmented into two parts: coarse discrete steps provided by the DSA and fine continuous adjustment provided by the VVA. This segmentation allows the system to achieve both precise discrete control and smooth transitions, resolving the contradiction between ease of operation and signal accuracy.
2Measurement precision
If voltage variable attenuators (VVAs) are designed with small attenuation ranges, then calibration accuracy improves, but control range is limited
Solution Approach 1:
The attenuation function is segmented between the DSA and VVA components. The VVA maintains a small optimized range for high calibration accuracy, while the DSA provides additional discrete steps to extend the total attenuation range, thus achieving both precision and versatility.
Solution Approach 2:
The DSA acts as an intermediary that extends the effective range of the VVA. By providing discrete attenuation steps before the signal enters the VVA, the system achieves a wide total attenuation range while the VVA itself maintains its optimal small range for high accuracy calibration.
3Adaptability or versatility
If voltage variable attenuators (VVAs) are designed with large attenuation ranges, then control versatility improves, but calibration accuracy decreases
Solution Approach 1:
The total attenuation range is segmented into coarse discrete steps (DSA) and fine continuous adjustment (VVA). This allows the VVA to maintain a limited optimized range for high calibration accuracy while the combined system provides large overall attenuation range for control versatility.
4Ease of operation
If hybrid attenuator system is implemented, then continuous fine adjustment is achieved, but device complexity increases
Solution Approach 1:
The patent merges a DSA and VVA into a single hybrid attenuator device with unified control logic. The controller automatically manages both components, providing continuous fine adjustment capability while consolidating the system architecture to minimize the increase in device complexity.
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
The programmable VVA provides a wide range of attenuation levels, reducing errors from abrupt signal changes and allowing for precise control in dynamic environments, while maintaining linearity and power handling capabilities, thus enhancing the performance of RF systems.
Implementation Method 1
variable resistance elements controlled by a field effect transistor (FET) or diode, enabling fine, step-less adjustments
Data Source
AI summary
A programmable voltage variable attenuator (VVA) that enables selection among multiple analog, continuous attenuation ranges. Some embodiments include a dual-mode interface to enable digitally programming a DAC and provide the analog output to control the attenuation level of the VVA, or alternatively apply an externally provided analog voltage to directly control the VVA attenuation level. A VVA may be used in conjunction with a digital step attenuator (DSA). Some embodiments include circuitry for changing the VVA reference impedance. The attenuator architecture of the VVA includes one or more variable resistance shunt elements and/or series elements which may be a resistor and FET circuit controlled by a provided variable analog voltage. The multiple resistance element architecture may be implemented with stacked FET devices. Embodiments for the VVA may be based, for example, on T-type, Bridged-T type, Pi-type, L-pad type, reflection type, or balanced coupler type attenuators.