Polar Transmitter Delay Calibration Using IQ I-Signal Minimization
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Solution Overview
Problem
In polar transmitters, a delay mismatch between the envelope path and the phase path leads to increased adjacent channel power (ACP), which is challenging to address effectively using existing calibration methods.
Innovation Solution
A method using a periodic test signal, such as a triangular or sawtooth waveform, is applied to both the envelope and phase paths to calibrate the propagation delay, with the delay block adjusted until the peak-to-peak value of the I-signal is minimized at the IQ demodulator, ensuring accurate delay matching without sending spurious signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a delay block is added to the phase component path to compensate for the longer propagation delay in the envelope path, then the propagation delay matching between the two paths is improved, but the device complexity increases
Solution Approach 1:
The delay block's delay value is made adjustable rather than fixed, allowing dynamic tuning to achieve optimal propagation delay matching between the envelope path and phase component path. This resolves the contradiction by enabling precise delay compensation while maintaining design flexibility.
Solution Approach 2:
The invention changes the delay parameter of the delay block to achieve propagation delay matching. By adjusting the delay value as a variable parameter, the system can compensate for path differences without requiring complex structural modifications.
2Measurement precision
If adjacent channel power measurement is used to find the right delay compensation value, then the measurement precision is improved, but the time required for calibration increases due to iterative adjustments
Solution Approach 1:
The invention uses adjacent channel power measurement as feedback to guide the adjustment of the delay block. The measured ACP values provide feedback information that indicates whether the current delay setting is optimal, enabling systematic calibration.
Solution Approach 2:
The invention performs preliminary calibration actions by systematically adjusting the delay block based on ACP measurements before actual operation. This preliminary delay compensation ensures optimal performance is achieved beforehand, reducing the need for iterative adjustments during operation.
3Object-affected harmful factors
If the transmitter RF power amplifier is disabled during calibration, then harmful spurious signals are eliminated, but the ability to perform real-time delay calibration during normal operation is lost
Solution Approach 1:
The invention separates the calibration function from the normal transmission function by implementing calibration during power amplifier disablement and potentially during dedicated calibration periods. This segmentation allows spurious signal elimination during calibration while maintaining normal operation capabilities separately.
Data Source
AI summary
A test signal comprising a periodic waveform, such as a triangular waveform and sawtooth waveform, is used for propagation delay matching in a transceiver front-end. The test signal is separately fed to the envelope path and the RF path. At the power amplifier stage, a phase modulator is used to obtain the envelope signal and the phase modulated RF signal for demodulation by an IQ demodulator. At the output end of the IQ demodulator, the I-signal is measured while the delay block is adjusted in order to vary the propagation delay. When the propagation delay matching is correct, the peak-to-peak value of the I-signal is a minimum. Preferably, during calibration using the test signal, the transmitter RF power amplifier is disabled so that no spurious signals will be sent. The transmitter can be an EDGE polar transmitter, a non-EDGE transmitter or a EER polar transmitter.