Polar Transmitter Time Alignment via Delay-Locked Loop
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Solution Overview
Problem
Precise alignment of phase and amplitude modulation signals in polar transmitters is challenging due to variations introduced by pulse-shaping filters, leading to spectral regrowth and error vector magnitude (EVM) degradation, especially in WCDMA systems which are more sensitive to timing errors.
Innovation Solution
A polar transmitter system incorporating a direct synthesis modulator and a signal alignment module with a triggering network that applies amplitude and frequency modulation control signals based on input signals, using latches and a delay-locked loop to establish a defined timing relationship between the signals, thereby adjusting signal time alignment within the transmitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If pulse-shaping filters are used to constrain the frequency spectrum of the signal, then the frequency spectrum is constrained, but timing alignment between phase and amplitude modulation signals deteriorates
Solution Approach 1:
The patent applies preliminary action by introducing a delay element in the amplitude modulation signal path to pre-compensate for the timing misalignment caused by pulse-shaping filters. This preliminary timing adjustment ensures that the phase and amplitude modulation signals are properly aligned before they are combined in the polar modulator, thereby maintaining signal integrity while using pulse-shaping filters for frequency constraint.
2Device complexity
If polar modulation is used to reduce circuitry and power consumption, then device complexity and power usage are reduced, but timing alignment difficulty increases
Solution Approach 1:
The patent implements feedback by using a delay-locked loop (DLL) mechanism that continuously monitors the timing relationship between phase and amplitude modulation signals and automatically adjusts the delay element to maintain optimal alignment. This feedback-based timing correction compensates for variations introduced by pulse-shaping filters and ensures precise signal alignment in the simplified polar modulation architecture.
Solution Approach 2:
The patent applies preliminary action by introducing a delay element in the amplitude modulation signal path to pre-compensate for the timing misalignment caused by pulse-shaping filters. This preliminary timing adjustment ensures that the phase and amplitude modulation signals are properly aligned before they are combined in the polar modulator, thereby maintaining signal integrity while using pulse-shaping filters for frequency constraint.
3Productivity
If WCDMA systems operate with standard timing settings, then system operation is maintained, but sensitivity to timing errors causes performance degradation
Solution Approach 1:
The patent implements feedback by using a delay-locked loop (DLL) mechanism that continuously monitors the timing relationship between phase and amplitude modulation signals and automatically adjusts the delay element to maintain optimal alignment. This feedback-based timing correction compensates for variations introduced by pulse-shaping filters and ensures precise signal alignment in the simplified polar modulation architecture.
Data Source
AI summary
An alignment apparatus for use with a polar transmitter system is disclosed herein. The alignment apparatus includes a signal alignment module configured to apply an amplitude modulation control signal and a frequency modulation control signal to the polar transmitter in accordance with a defined timing relationship. A time alignment network, operatively coupled between an output of the polar transmitter system and the signal alignment module, sets the defined timing relationship.