Variable Analog Delay Line Impedance Control
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Solution Overview
Problem
Existing technologies for electronically variable analog delay lines face challenges such as varying characteristic impedance with delay, signal non-linearity, high insertion loss, and noise generation, which limit their effectiveness in achieving the desired delay range and signal quality, especially at higher frequencies.
Innovation Solution
A lumped-element transmission line with multiple segments using coupled transmission lines, capacitors, and PIN diode switches that adjust inductance and capacitance to maintain constant characteristic impedance while varying delay, allowing for both short-delay and long-delay modes without significant impedance changes, thus minimizing signal distortion and loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fixed inductors and varactors are used to implement electronically adjustable analog delay line, then delay is electronically variable, but characteristic impedance varies along with delay requiring limited delay ratio
Solution Approach 1:
The patent changes the operating parameters by using switched inductor configurations that alter the delay time while maintaining constant characteristic impedance. The inductors are switched between series and parallel configurations, which changes the total inductance value and thus the delay, while the impedance remains constant due to the specific switching topology employed.
Solution Approach 2:
The patent implements dynamic switching of inductor configurations using control signals. The switches dynamically reconfigure the inductor network to provide different delay values (short-delay mode and long-delay mode) while maintaining constant impedance, enabling real-time adjustment without impedance variation.
2Adaptability or versatility
If varactors are used for delay adjustment, then delay is electronically variable, but signal non-linearity occurs due to response to signal voltage
Solution Approach 1:
The patent replaces varactors with ideal switches (modeled as short-circuit when on) that provide abrupt, non-linear switching behavior. This eliminates the signal voltage-dependent capacitance effect of varactors, as the switches either fully conduct or fully block, providing linear signal transmission during the conducting state and eliminating the non-linearity inherent in varactor-based tuning.
3Device complexity
If MEMs switches are used to switch segment lengths, then characteristic impedance remains constant, but significant insertion loss occurs due to contact resistance
Solution Approach 1:
The patent replaces mechanical MEMs switches with electronic switches (transistors or diodes) that have negligible on-resistance compared to MEMs contact resistance. This substitution maintains the constant impedance benefit while dramatically reducing insertion loss, as electronic switches can achieve resistance values orders of magnitude lower than mechanical contacts.
4Ease of manufacture
If switched active delay elements are used, then standard IC process compatibility is achieved, but signal-to-noise ratio degrades due to noise generation
Solution Approach 1:
The patent extracts the active amplification function from the delay element itself and replaces it with passive switched inductor structures. By removing the active stages that generate noise, the design achieves IC compatibility through passive components while eliminating the primary noise source, resulting in superior signal-to-noise ratio compared to switched active delay elements.
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 provides a flexible and efficient delay control with minimal insertion loss and signal non-linearity, enabling a wider delay range with improved signal quality and reduced noise, suitable for high-frequency applications.
Implementation Method 1
A lumped-element transmission line with multiple segments using coupled transmission lines, capacitors, and PIN diode switches that adjust inductance and capacitance to maintain constant characteristic impedance while varying delay
Implementation Method 2
A lumped-element transmission line with multiple segments using coupled transmission lines, capacitors, and PIN diode switches
Data Source
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AI summary
An electronically variable analog delay line (100) including at least one segment (200, 300) with an electronically variable inductance. The at least one segment (200, 300) includes a signal path (16) , a ground return path (22), and a plurality of switches (18, 20, 34) configured to vary the inductance of the segment, thereby providing a first delay in a short-delay functioning mode and a second delay in a respectively long-delay functioning mode. In the long-dealy functioning mode, a capacitor (28, 32, 36) is connected to the signal path (16) to compensate for the imepdance change.