Feedback-Controlled I/O Signal Shaping for RF Magnetic Coupling
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Solution Overview
Problem
Digital I/O pins on System-on-Chip (SOC) devices with sensitive RF components experience degradation in sensitivity and noise figure performance due to magnetic coupling from digital outputs, which is influenced by I/O supply voltage, load capacitance, process variations, and propagation delay and rise/fall time of digital signals.
Innovation Solution
A system comprising an integrated circuit with programmable current rise-time and fall-time circuits, a feedback circuit, and a control circuit that adjusts the rise and fall times of digital output signals to reduce harmonic components at RF frequencies, thereby minimizing magnetic coupling to RF circuits while maintaining symmetric propagation delay and rise/fall time specifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If digital output signals are transmitted through I/O pads connected to capacitors, then data transmission function is achieved, but magnetic loops are generated that induce current in nearby circuits and degrade RF circuit performance
Solution Approach 1:
The patent applies preliminary action by pre-shaping the current waveform of the digital output signal before it reaches the I/O pad. The current shaping circuit modifies the current profile to reduce harmonic content at RF frequencies in advance, preventing the generation of strong magnetic loops that would couple to RF circuits. This proactive approach addresses the magnetic coupling issue before it affects RF performance.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting the current waveform parameters (amplitude, duration, shape) of the digital output signal. The current shaping circuit modifies these parameters to minimize harmonic content at RF frequencies while maintaining the essential data transmission function. This allows optimization of the current profile to reduce magnetic coupling without sacrificing productivity.
2Speed
If rise time and fall time of digital signals are reduced to improve transmission speed, then data transmission speed increases, but harmonic components at RF frequencies increase and magnetic coupling worsens
Solution Approach 1:
The patent applies parameter changes by independently optimizing the current waveform parameters (rise time, fall time, amplitude profile) through current shaping. This allows the system to maintain fast transmission speeds while modifying the current profile to reduce harmonic content at RF frequencies. The current shaping circuit adjusts these parameters to achieve both high speed and low magnetic coupling.
Solution Approach 2:
The patent employs dynamics by using dynamic current shaping that adapts the current waveform in real-time. The current shaping circuit can dynamically adjust the current profile based on the signal characteristics to minimize harmonics while maintaining fast edge rates. This dynamic approach allows optimization of both speed and magnetic coupling performance.
3Power
If I/O supply voltage is increased to improve signal strength, then signal transmission capability improves, but current spikes increase and magnetic loop effects are amplified
Solution Approach 1:
The patent applies parameter changes by modifying the current waveform parameters (amplitude, duration, shape) through current shaping. This allows the system to maintain strong signal transmission capability while reducing the peak current spikes that generate magnetic loops. The current shaping circuit optimizes these parameters to achieve both high power capability and reduced magnetic coupling.
Solution Approach 2:
The patent converts the potentially harmful effect of high current into a beneficial outcome by shaping the current waveform. The current shaping circuit transforms the current profile to reduce harmonic content and minimize magnetic loop effects, while still delivering the necessary power for strong signal transmission. This converts what would be a harmful high-current spike into a controlled, optimized current waveform.
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 effectively decreases harmonics in the output digital signal, reducing magnetic coupling to RF circuits and enhancing RF isolation without requiring bias current, thus maintaining compliance with propagation delay specifications across varying load capacitors, supply voltages, and temperature conditions.
Implementation Method 1
a feedback circuit that is configured to monitor a rise-time of the rising edge of the output digital signal and fall-time of the falling edge of the output digital signal
Implementation Method 2
programmable current rise-time and fall-time circuits, a feedback circuit, and a control circuit that adjusts the rise and fall times of digital output signals to reduce harmonic components at RF frequencies
Implementation Method 3
adjusts the rise and fall times of digital output signals to reduce harmonic components at RF frequencies, thereby minimizing magnetic coupling to RF circuits
Data Source
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AI summary
Various arrangements for decreasing harmonics of an output digital signal are presented. A programmable current rise-time circuit may be present that controls a rising edge of the output digital signal, wherein the output digital signal is output to an input/output (I/O) pad. A programmable current fall-time circuit may be present that controls a falling edge of the output digital signal. A feedback circuit may be present that monitors a rise-time of the rising edge of the output digital signal and fall-time of the falling edge of the output digital signal. A control circuit may be present that provides a first input to the programmable current rise-time circuit to adjust the rise-time of the rising edge of the output digital signal and a second input to the programmable current fall-time circuit to adjust the fall-time of the falling edge of the output digital signal.