Capacitive Variable Gain Circuit With Transient Compensation

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Solution Overview

Problem

Radar systems face interference issues due to nearby vehicle signals, leading to receiver overload and a need for rapid gain adjustments that cause undesirable transient settling effects, which are not effectively addressed by existing technologies.

Innovation Solution

A variable gain arrangement using capacitive feedback with transient compensation capacitors to adjust gain quickly while minimizing transient settling effects by dynamically reconfiguring capacitor interconnections and injecting corrective charge to maintain signal integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If gain is adjusted rapidly to handle interference bursts, then interference robustness is improved, but transient settling effects worsen

Engineering Contradiction:

Improveinterference robustnessVSAvoidsignal integrity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The transient compensation capacitor is pre-charged to the output voltage level before gain switching occurs. When gain adjustment is needed, the pre-charged capacitor is connected to compensate for the transient voltage change, eliminating settling effects and allowing immediate accurate signal processing.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The transient compensation capacitor acts as an intermediary element between the feedback capacitor and the output node. It mediates the transient voltage changes by providing or absorbing charge as needed, isolating the output from the abrupt gain changes and maintaining signal integrity during rapid gain adjustments.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If receiver gain is reduced during interference bursts, then interference robustness is improved, but signal-to-noise ratio deteriorates

Engineering Contradiction:

Improveinterference robustnessVSAvoidsignal-to-noise ratio

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The system dynamically adjusts gain on a per-burst basis rather than maintaining a fixed gain setting. The gain switching apparatus enables rapid transition between different gain states, allowing the receiver to adapt to varying interference conditions while the transient compensation ensures accurate signal processing at each gain level.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system employs periodic gain adjustment synchronized with the interference burst pattern. Gain is reduced during interference bursts and restored during normal operation, creating a periodic gain modulation pattern that maintains signal-to-noise ratio during non-interference periods while providing protection during interference events.

Inventive Principle:

Principle #19Periodic action

3Productivity

If settling time is eliminated for rapid gain switching, then productivity is improved, but transient settling effects worsen

Engineering Contradiction:

Improvegain switching speedVSAvoidsignal accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The transient compensation capacitor is connected to the output node and provides feedback compensation for transient voltage changes. By sensing the output voltage and using the pre-charged capacitor to counteract transient effects, the system maintains signal accuracy during rapid gain switching without requiring settling time.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system changes the capacitance parameter dynamically by switching between different capacitor configurations. The transient compensation capacitor changes its effective capacitance value based on the gain switching state, providing optimal compensation for each gain level and enabling rapid transitions without transient effects.

Inventive Principle:

Principle #35Parameter changes

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

Enables rapid interference robustness in radar systems by reducing receiver gain during interference bursts, maintaining signal-to-noise ratio without significant power increase, and eliminating the need for settling time.

Implementation Method 1

the current injection capacitor is configured to, upon a change in the gain of the output signal, be coupled to the feedback capacitor such that charge is injected onto the feedback capacitor wherein the charge injection provides for the transient settling effect compensation

Methodology Applied

Scientific EffectCharge injection: Capacitance

Data Source

PatentUS20250293653A1Variable gain arrangement

Publication Date: 2025.09.18 NXP BV

AI summary

A variable gain arrangement of a receiver path configured to receive an input signal and apply a gain to the input signal to provide an output signal, comprising: an input capacitor arrangement comprising a first input capacitor; a feedback capacitor arranged in series with the input capacitor arrangement, wherein the gain is based on a ratio of the first input capacitor and the feedback capacitor; and a gain switching apparatus configured to provide for adjustment of the gain applied to the input signal by changing the ratio; an amplifier in series with the input capacitor arrangement, the amplifier arranged in parallel with the feedback capacitor, the amplifier configured to provide the output signal; and a transient compensation capacitor arrangement comprising a first transient compensation capacitor, wherein, upon a change in the gain, the at least one transient compensation capacitor is configured to be coupled to or decoupled from the feedback capacitor such that transient settling effects caused by the gain change are compensated.