Differential Pi Attenuator With Phase-Invariant RF Attenuation
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Solution Overview
Problem
Ensuring that radio-frequency signals in electronic devices with wireless communications circuitry are provided at satisfactory voltage levels and consistent phases is challenging, particularly in preventing undesirable jammer signals from interfering with the signal of interest.
Innovation Solution
The implementation of programmable resistive pi attenuators with cross-coupled capacitors in differential signal paths of phased antenna arrays, which adjust attenuation levels and minimize phase variation across different settings, providing spatial filtering to prevent interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If signal attenuators are adjusted to different attenuation levels, then signal voltage levels are controlled, but phase variation increases
Solution Approach 1:
The patent changes the electrical parameters (capacitance values) of the capacitors in the pi attenuator network to specific values that compensate for the phase shifts introduced by the resistors. By carefully selecting capacitor values, the circuit maintains phase consistency across different attenuation settings while still providing voltage level control.
Solution Approach 2:
The capacitors serve as intermediary elements that mediate between the resistors (which provide attenuation) and the signal path. These capacitors introduce compensating phase effects that counterbalance the phase shifts caused by the resistors, thereby maintaining overall phase consistency in the signal.
2Power
If resistive pi attenuators are used to attenuate radio-frequency signals, then signal voltage is reduced, but jammer signals interfere with the signal of interest
Solution Approach 1:
The patent applies different attenuation levels to different spatial directions by integrating the pi attenuators into a phased antenna array system. Each antenna element can have its signal attenuated differently, allowing the system to create directional beam patterns that enhance the signal of interest while suppressing jammer signals from specific directions.
Solution Approach 2:
The attenuators are made programmable and adjustable, allowing dynamic control of attenuation levels. This enables real-time adaptation of the antenna array's radiation pattern to track and enhance desired signals while dynamically suppressing interfering jammer signals as they move or change in strength.
3Reliability
If programmable attenuators are implemented in phased antenna arrays, then spatial filtering is improved, but device complexity increases
Solution Approach 1:
The patent divides the antenna array into multiple independent antenna elements, each with its own pi attenuator network. This segmentation allows each element to be controlled independently for spatial filtering purposes. The modular nature of repeating the same pi attenuator circuit at each element keeps individual component complexity low while achieving sophisticated overall performance.
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 solution ensures that radio-frequency signals are attenuated with minimal phase variation, effectively preventing interference from unwanted jammer signals and maintaining consistent signal quality across various attenuation levels.
Implementation Method 1
The capacitors may have capacitances equal to a parasitic capacitance of switching circuitry in one or more of the resistors of the signal attenuator. The capacitors may serve to cancel out undesirable feed-forward current paths in the resistor(s).
Data Source
AI summary
An electronic device may have wireless circuitry that includes a differential signal path having first and second signal lines. A pi attenuator may be disposed on the differential signal path. The pi attenuator may include a first series resistor on the first signal line, a second series resistor on the second signal line, and parallel resistors coupled between the first and second signal lines on opposing sides of the series resistors. A first capacitor may couple an input terminal of the first series resistor to an output terminal of the second series resistor and a second capacitor may couple an output terminal of the first series resistor to an input terminal of the second series resistor. The capacitors may serve to minimize phase variation as a function of attenuation level in attenuated signals output by the pi attenuator.