Programmable VVA Range Switching for Smooth RF Attenuation
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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, and analog voltage variable attenuators (VVAs) struggle with determining economic attenuation ranges, especially for small ranges that require precise calibration and signal alignment.
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 shunt and series 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 states can be achieved, but abrupt signal level changes occur causing errors in RF systems
Solution Approach 1:
The patent transitions from static discrete attenuation steps in DSAs to a dynamic continuous attenuation mechanism using voltage-controlled resistive devices. The control voltage can be varied continuously to provide smooth attenuation changes without abrupt steps, eliminating signal distortion while maintaining selectable attenuation capability.
Solution Approach 2:
The invention changes the control parameter from discrete digital steps to continuous analog voltage. By using a voltage-controlled resistive device where resistance varies continuously with control voltage, the system achieves continuous attenuation adjustment rather than discrete steps, thereby eliminating abrupt signal level changes.
2Reliability
If voltage variable attenuators (VVAs) are used to provide continuous attenuation range, then abrupt signal changes are eliminated, but determining economic attenuation ranges becomes difficult
Solution Approach 1:
The patent segments the attenuation range into multiple selectable continuous ranges (e.g., 0-15 dB, 0-30 dB, 0-45 dB) using switchable attenuator cells with different attenuation characteristics. This allows the system to provide continuous variation within each segment while offering discrete range selection, making the device adaptable to different application requirements without overwhelming complexity.
Solution Approach 2:
The invention creates a multi-functional VVA that can operate in multiple continuous attenuation ranges within a single device. By integrating switchable attenuator cells that can be configured for different attenuation ranges, the device serves multiple functions (different range selections) while maintaining the benefit of continuous attenuation control, eliminating the need for multiple separate devices.
3Measurement precision
If small attenuation ranges are used in VVAs, then calibration accuracy improves, but control flexibility is reduced
Solution Approach 1:
The patent implements a dynamic range selection capability where the attenuator can switch between different continuous attenuation ranges (e.g., narrow 0-15 dB for high precision applications, wide 0-45 dB for high dynamic range applications). This dynamic adaptability allows the system to optimize between calibration accuracy and control flexibility based on real-time application requirements.
Solution Approach 2:
The invention enables change of the attenuation range parameter through switching between different attenuator cell configurations. The system can adjust the maximum attenuation value parameter (from 15 dB to 30 dB to 45 dB ranges) while maintaining continuous control within each range, allowing optimization of calibration accuracy versus control flexibility based on application needs.
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, while maintaining linearity and compatibility with various impedance systems, thus enhancing the accuracy and flexibility of RF signal processing.
Implementation Method 1
variable resistance shunt and series elements controlled by a field effect transistor (FET) or diode, enabling fine, step-less adjustments
Implementation Method 2
digitally program a multiple bit digital-to-analog converter (DAC) and provide the analog output of the DAC to control the attenuation level of the VVA
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.