DPLL DCO Compensation for AM-Induced Phase Distortion
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Solution Overview
Problem
Power efficiency issues in transceiver architectures for portable handheld devices, particularly due to parasitic coupling and distortions introduced by amplitude modulation in polar modulation schemes, leading to data loss and reduced bandwidth.
Innovation Solution
A compensation filter and unit are used to mitigate phase distortions caused by amplitude modulation, generating a correction signal to account for frequency deviations and pre-distort the phase modulation signal, independent of digital phase locked loop filter characteristics, thereby reducing parasitic frequency modulation and improving power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If polar modulation concept is used to improve power efficiency, then power efficiency is improved, but AM path introduces distortions into PM path resulting in data loss and reduced bandwidth
Solution Approach 1:
The patent implements a feedback mechanism where the amplitude modulation signal is monitored and used to generate a compensation signal that counteracts the AM-to-FM distortions. The distortion measurement unit measures the actual distortions introduced by the AM path, and this measurement feeds back to the correction signal generator which adjusts the PM signal in real-time to compensate for the distortions, thereby maintaining data integrity while preserving power efficiency
Solution Approach 2:
The patent introduces an intermediary compensation signal that mediates between the AM path and PM path. The correction signal generator creates an intermediate compensation signal based on the AM signal characteristics, which is then combined with the PM signal to cancel out the distortions. This intermediary approach allows the system to maintain the benefits of polar modulation while eliminating its harmful effects
2Reliability
If vector modulator architecture is used with complete linear signal path, then signal quality is maintained, but power efficiency deteriorates
Solution Approach 1:
The patent extracts and separates the distortion compensation function from the main modulation path. By taking out the AM-to-FM distortion as a measurable and compensatable effect, the system can use a non-linear polar modulation architecture (which is more power-efficient) while still achieving the signal quality of linear architectures through the extracted and compensated distortion component
Solution Approach 2:
The patent changes the operational parameters of the modulation system by allowing the PM signal to operate in a non-linear regime that improves power efficiency, while simultaneously adjusting the compensation signal parameters to counteract the resulting distortions. This parameter change approach enables the system to operate in a more efficient regime while maintaining signal quality through dynamic parameter adjustment
3Object-affected harmful factors
If transceiver and power amplifier are separated on mobile PCB, then parasitic coupling is avoided, but device complexity increases
Solution Approach 1:
The patent converts the harmful parasitic coupling effects into a measurable and compensatable distortion characteristic. Instead of physically separating components to avoid coupling, the system allows the coupling to occur and then uses the distortion measurement unit to quantify it, transforming the harmful effect into useful information that drives the compensation mechanism, thereby simplifying the physical layout while maintaining signal integrity
Data Source
AI summary
One embodiment of the present invention relates to a communication system having a digital to analog converter, a first input, a summation component, a compensation filter, and a compensation unit. The converter is configured to receive a first signal. The first input is configured to receive a phase modulation signal. The compensation filter generates a filtered frequency deviation signal to mitigate frequency distortions, such as those from a digital controlled oscillator. The compensation unit includes one or more inputs and is configured to generate a correction signal according to the filtered frequency deviation signal and the first signal. The correction signal at least partially accounts for estimated distortions of the phase modulation signal from the amplitude modulation path and mitigates frequency induced distortions. The summation component is configured to receive the phase modulation signal and the correction signal and to generate a corrected phase modulation signal as a result.