Time Alignment Analog Notch for Digital Power Amplifier Interference
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Solution Overview
Problem
The increased number of communications protocols and frequency bands in electronic devices leads to interference issues, such as noise shaping in sigma-delta modulated data causing interference in the Industrial, Scientific, and Medical (ISM) band, which existing solutions like comb filters address but at the cost of reducing transmission resolution.
Innovation Solution
A system and method for creating a time alignment analog notch using a digital power amplifier with a selection circuit and matching network, which adjusts the clock pulse delay to optimize frequency response and reduce interference without significantly increasing hardware complexity or cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If comb filters are added to eliminate noise shaping interference, then interference in the ISM band is reduced, but transmission resolution is decreased
Solution Approach 1:
The patent extracts and removes the harmful noise shaping components from the sigma-delta modulated signal by configuring specific transistors to cancel out the noise shaping frequencies. This is achieved by taking out the problematic frequency components through selective transistor switching rather than using a comb filter that would remove useful signal components along with the noise.
Solution Approach 2:
The patent changes the operational parameters of transistors within the power amplifier by selectively turning specific transistors on and off based on control signals. This parameter change allows the system to dynamically adjust the amplifier's characteristics to cancel noise shaping interference while maintaining signal integrity and resolution.
2Object-affected harmful factors
If more fingers are added to the comb filter to improve interference reduction, then interference elimination is enhanced, but resolution loss increases
Solution Approach 1:
Instead of adding more filter fingers that would progressively remove more signal components, the patent extracts only the specific harmful noise shaping components through selective transistor switching. This approach eliminates interference without the progressive resolution loss that would result from adding more comb filter fingers.
Solution Approach 2:
The patent converts the harmful noise shaping effect into a beneficial cancellation mechanism by using the same sigma-delta modulation principle to generate control signals that switch transistors in a way that actively cancels the noise shaping interference. The noise shaping process itself is harnessed to create the cancellation effect rather than simply filtering it out.
Data Source
AI summary
System and method for creating a time alignment analog notch. An embodiment includes a digital power amplifier coupled to an enable signal line and to a digital control bits bus, and a matching network coupled to the digital power amplifier. The matching network to provide impedance matching and the digital power amplifier to produce a current based on a value on the digital control bits bus. The digital power amplifier comprises a selection circuit and a plurality of transistors. The transistors, controlled by outputs of the selection circuit, provide a current based on the value on the digital control bits bus. The adjustment of a delay between a signal on the enable signal line and the values on the digital control bits bus creates an analog notch at about Fs/2, where Fs is a sampling frequency of a sigma-delta modulator used to modulate data provided to the digital power amplifier.