Receiver Gain Compensation for Audible Artifact Reduction
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Solution Overview
Problem
Radio receivers face challenges with audible artifacts due to rapid gain changes in analog gain blocks, which are difficult to control without increasing complexity, die size, and power consumption, especially when combined with digital circuitry in AM and FM receivers.
Innovation Solution
A gain compensation mechanism is introduced to inject a compensation signal into the signal path, allowing a gain change to propagate slowly and reduce or eliminate audible artifacts by using a combination of analog and digital circuitry, including a digital signal processor for AGC control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If analog gain blocks are controlled with instantaneous gain changes, then the response speed is improved, but audible artifacts are generated
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing compensation values in a lookup table before gain changes occur. When a gain change is needed, the corresponding compensation value is immediately retrieved and applied to the digital signal path, preventing audible artifacts before they can manifest. This resolves the contradiction by enabling fast response through pre-computed values rather than real-time calculation.
Solution Approach 2:
The patent introduces a compensation signal as an intermediary element that mediates between the analog gain block control and the digital signal path. This compensation signal, derived from the difference between old and new gain values, acts as a mediator to cancel out the instantaneous gain change effects in the digital domain, thereby eliminating audible artifacts while maintaining fast analog gain switching.
2Object-generated harmful factors
If numerous small steps are used to control analog gain blocks slowly, then audible artifacts are reduced, but device complexity and die size increase
Solution Approach 1:
The patent replaces the mechanical approach of using multiple discrete gain steps with a digital signal processing solution. Instead of physically implementing numerous small gain steps in analog circuitry, the invention uses digital compensation signals to mathematically cancel out gain changes, thereby reducing audible artifacts without increasing analog circuit complexity or die size.
Solution Approach 2:
The patent changes the parameter domain from analog gain step control to digital compensation signal injection. By transforming the control mechanism from adjusting analog gain values in small increments to injecting digitally generated compensation signals, the system achieves artifact reduction with minimal increase in complexity, as the compensation values are computed and stored in digital form.
3Object-generated harmful factors
If numerous small steps are used to control analog gain blocks slowly, then audible artifacts are reduced, but power consumption increases
Solution Approach 1:
The patent replaces the energy-intensive analog approach of using multiple small gain steps with a low-power digital compensation mechanism. The digital lookup table stores pre-computed compensation values that require minimal power to retrieve and apply, eliminating the need for continuous analog adjustments and associated power consumption while still reducing audible artifacts.
Data Source
AI summary
In one embodiment, the present invention includes a method for injecting a gain compensation value into a signal path of a receiver for a predetermined time when a change to a control value for an amplifier of the receiver occurs. This gain compensation value may be used to at least substantially remove a gain change caused by the change to the control value, improving audio performance by reducing or removing audible artifacts caused by the gain change.