PIN Diode Hybrid Attenuator for Flat Phase and Low Reflection
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Solution Overview
Problem
Conventional signal attenuators introduce detrimental phase shifts and signal reflections, degrading the performance of electronic devices like phased array radars due to varying reactive effects of control transistors or diodes.
Innovation Solution
A signal attenuator design using PIN diodes coupled to coupler ports, where a terminating PIN diode becomes increasingly well-matched and absorptive, while a series PIN diode becomes increasingly mismatched and reflective over a given attenuation range, minimizing phase shifts and reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional voltage or current controlled adjustable attenuators are used, then signal attenuation can be adjusted, but insertion phase varies with attenuation level due to varying reactive effects of control transistors or diodes
Solution Approach 1:
The attenuator is divided into multiple discrete attenuation steps using separate attenuator circuits (e.g., first attenuator circuit for 0-10dB, second for 10-20dB, etc.). Each circuit provides a fixed attenuation range, and by switching between circuits, the total attenuation is adjusted in discrete increments. This segmentation eliminates the continuous variation of reactive effects found in conventional adjustable attenuators, maintaining stable insertion phase across different attenuation levels.
Solution Approach 2:
The attenuator uses dynamic switching between different attenuator circuits based on the desired attenuation level. Control logic dynamically selects which attenuator circuit to activate, allowing the system to adapt to different signal requirements while maintaining optimal phase characteristics for each attenuation range. This dynamic configuration resolves the contradiction by providing adjustability without continuous phase variation.
2Adaptability or versatility
If conventional adjustable attenuators are used, then attenuation can be controlled, but signal reflections increase due to varying reactive effects
Solution Approach 1:
By dividing the attenuation function into multiple discrete circuits, each optimized for a specific attenuation range, the system avoids the reactive effects that cause reflections in continuously adjustable attenuators. Each segmented circuit maintains better impedance matching within its operating range, reducing signal reflections while still providing the required attenuation control capability.
3Adaptability or versatility
If PIN diodes are used in attenuator circuits, then attenuation can be controlled, but the terminating PIN diode must be well-matched and absorptive while the series PIN diode becomes mismatched and reflective
Solution Approach 1:
The attenuator uses multiple PIN diode-based attenuator circuits, each handling a specific attenuation segment. The terminating PIN diode in each circuit is designed to be well-matched and absorptive for its specific range, while the series PIN diode's reflective characteristics are managed by the circuit design. By segmenting the total attenuation range across multiple circuits, the system achieves wide attenuation capability while minimizing harmful reflections at any given attenuation level.
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 attenuator achieves a flat phase response and low return loss, ensuring optimal signal transmission and reducing reflections, suitable for applications like phased array antennas and mixer drivers.
Implementation Method 1
a signal attenuator design using PIN diodes coupled to coupler ports, where a terminating PIN diode becomes increasingly well-matched and absorptive, while a series PIN diode becomes increasingly mismatched and reflective over a given attenuation range
Data Source
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Figure 3A
AI summary
Methods and apparatus for an absorptive, phase invariant signal attenuator. In embodiments, PIN diodes (111, 114) can be coupled to a hybrid coupler (106). Incident power can be split by the coupler (106) to a terminating resistor (118), a terminating diode (114), and a series diode (111). The terminating diode (114) becomes increasingly well matched and absorptive over the attenuation range. The series diode (111) becomes increasingly mismatched and reflective over the attenuation range. The terminating resistor (118) increasingly absorbs incident power as the coupling value decreases due to increasing diode impedance over the attenuation range.