Programmable RF Attenuator With Continuous and Stepwise 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 analog voltage variable attenuators (VVAs) struggle with determining economic attenuation ranges, requiring either small or large attenuation ranges for effective control.
Innovation Solution
A programmable voltage variable attenuator (VVA) with a dual-mode interface that digitally programs a multiple-bit DAC for analog output control or applies external analog voltage, incorporating variable resistance shunt and series elements controlled by FETs or diodes, allowing for multiple analog attenuation ranges 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 device. The DSA provides coarse discrete attenuation steps while the VVA provides continuous fine-tuning capability, merging both approaches to eliminate abrupt transitions while maintaining discrete control functionality.
Solution Approach 2:
The patent introduces dynamic control by adding a voltage variable attenuator section that can continuously adjust attenuation levels between the discrete steps provided by the DSA. This dynamic adjustment eliminates the abrupt signal level changes inherent in pure digital step attenuators.
2Ease of operation
If voltage variable attenuators (VVAs) are used to provide continuous attenuation range, then fine control is achieved, but determining economic attenuation range becomes challenging
Solution Approach 1:
The patent segments the total attenuation range into two parts: a coarse adjustment section handled by the DSA with discrete steps, and a fine adjustment section handled by the VVA with continuous control. This segmentation makes the overall attenuation range management more manageable and economically viable.
Solution Approach 2:
The hybrid attenuator structure provides multiple functions within a single device: discrete step control from the DSA, continuous fine-tuning from the VVA, and the ability to configure different attenuation ranges by selecting which VVA sections are active. This multi-functionality addresses the complexity of determining appropriate attenuation ranges.
3Adaptability or versatility
If multiple VVA sections are used to provide wide attenuation range, then control flexibility increases, but device complexity increases
Solution Approach 1:
The patent employs dynamic switching mechanisms that allow the same physical VVA sections to serve different attenuation range configurations based on operational requirements. The system can dynamically activate or deactivate specific VVA sections to provide 0-4dB, 0-8dB, or 0-12dB ranges, reducing the need for multiple dedicated hardware sections.
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
Enables continuous, fine adjustments in attenuation levels, improving signal control and reducing errors by providing a wide range of attenuation options while maintaining system compatibility and efficiency.
Implementation Method 1
The FET is operated over its linear region to provide a variable degree of conduction from source to drain in response to a control voltage applied to its gate, thereby regulating the amount of total resistance presented by the FET-resistor combination.
Implementation Method 2
In particular embodiments disclosed below, the shunt element is series connected (i.e., R+FET) while the series element is parallel connected (i.e., R∥FET).
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.