Digital Attenuator Phase Matching Circuitry
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Solution Overview
Problem
Conventional digital attenuators experience high Voltage Standing Wave Ratio (VSWR) and attenuation accuracy degradation at higher frequencies due to cascading bits, leading to increased noise and phase differences between on and off states.
Innovation Solution
A digital attenuator circuit with equalized effective phase lengths in the reference loss and attenuation paths, implemented using switching elements and matching circuitry, along with interstage inductance elements as high impedance transmission lines to minimize reflections and maintain constant phase across states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple 1-bit digital attenuators are cascaded to produce multi-bit digital attenuator, then the attenuation range is improved, but the reference insertion loss increases resulting in higher VSWR
Solution Approach 1:
The patent introduces an intermediary matching network between cascaded attenuator stages. This matching network acts as a mediator that transforms the high impedance presented by cascaded stages to a lower impedance, thereby reducing VSWR while preserving the extended attenuation range achieved through cascading.
Solution Approach 2:
The patent transforms the impedance parameters of the cascaded attenuator stages by introducing matching elements that change the electrical characteristics of the connection points. This parameter transformation reduces the VSWR without compromising the attenuation range provided by the cascaded structure.
2Adaptability or versatility
If multiple bits are cascaded in the digital attenuator, then the attenuation range is improved, but the attenuation accuracy deteriorates when multiple bits are switched on at the same time
Solution Approach 1:
The matching network serves as an intermediary that isolates the switching operations of individual bits from each other. By providing impedance transformation and isolation, it prevents the interactive effects that cause accuracy deterioration when multiple bits are switched simultaneously, while maintaining the full attenuation range.
3Speed
If conventional digital attenuators are used at higher frequencies, then the basic attenuation function is maintained, but significant phase difference occurs between on and off states
Solution Approach 1:
The matching network acts as a phase-stabilizing intermediary at higher frequencies. It compensates for frequency-dependent phase variations that occur in conventional attenuators, maintaining consistent phase relationships between on and off states across the operating frequency range.
Solution Approach 2:
The patent creates equipotential conditions for phase stability by designing the matching network to maintain equal electrical path lengths and impedance characteristics. This ensures that phase differences between on and off states remain minimal even at higher operating frequencies.
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 solution provides improved VSWR and phase accuracy at higher frequencies, reducing noise and maintaining consistent attenuation performance across different states, thereby enhancing system performance.
Implementation Method 1
An effective phase length of the reference loss path and an effective phase length of the attenuation path may be equalized to provide a constant phase when the digital attenuator circuit is switched between states
Implementation Method 2
The multi-stage digital attenuator includes a plurality of interstage inductance elements implemented as high impedance transmission lines to match the output of a previous stage and the input of a next stage
Implementation Method 3
interstage inductance elements implemented as high impedance transmission lines to match the output of a previous stage and the input of a next stage
Implementation Method 4
The attenuation path comprises switching elements and attenuating circuitry to attenuate the input signal when the digital attenuator circuit is switched from a reference loss state to an attenuation state
Data Source
AI summary
Various embodiments are directed to providing constant phase digital attenuation. In one embodiment, a digital attenuator circuit (100) comprises an input node (102) to receive an input signal to be attenuated, an output node (104) to output an attenuated signal, a reference loss path (106) between the input node (102) and the output node (104), and an attenuation path (108) between the input node (102) and the output node (104). The reference loss path (106) comprises switching elements and matching circuitry to improve Voltage Standing Wave Ratio (VSWR), and the attenuation path (108) comprises switching elements and attenuating circuitry to attenuate the input signal when the digital attenuator circuit (100) is switched from a reference loss state to an attenuation state. An effective phase length of the reference loss path (106) and an effective phase length of the attenuation path (108) may be equalized to provide a constant phase when the digital attenuator circuit (100) is switched between states.