Self-Calibrated Harmonic Rejection Mixer for LO Phase Accuracy
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Solution Overview
Problem
Existing wireless transmitter circuitry in electronic devices faces challenges in maintaining signal quality due to harmonic interference from local oscillator harmonics, leading to EVM degradation and emission mask violations, especially at centimeter/millimeter wave frequencies where phase accuracy is difficult to maintain over varying conditions.
Innovation Solution
The implementation of a harmonic rejection mixer with a programmable delay line, mixer array, and adjustable load, which operates in both transmit and calibration modes to generate calibrated local oscillator phases, canceling out harmonic interference by identifying and adjusting phase codes to optimize performance across changing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a local oscillator is used to generate radio-frequency signals, then wireless transmission is enabled, but harmonic interference degrades signal quality and causes EVM degradation
Solution Approach 1:
The patent converts the harmful harmonic interference into a useful calibration signal. By intentionally generating known harmonic components and using them as reference signals for calibration, the system transforms the problematic harmonics into a beneficial resource for maintaining phase accuracy and canceling interference during normal operation.
Solution Approach 2:
The system dynamically adjusts phase parameters through calibration. The programmable delay line modifies phase codes based on measured conditions, changing the phase parameters of the local oscillator signals to optimize performance and cancel harmonic interference under varying operating conditions.
2Measurement precision
If phase accuracy is maintained for harmonic rejection, then signal quality improves, but maintaining phase accuracy becomes difficult under varying operating conditions
Solution Approach 1:
The patent implements a feedback-based calibration system that measures phase accuracy under current operating conditions and adjusts the programmable delay line accordingly. This closed-loop approach continuously maintains phase accuracy despite variations in temperature, frequency, and other environmental factors.
Solution Approach 2:
The system performs preliminary calibration actions to establish accurate phase relationships before normal transmission begins. By pre-calibrating the phase codes under specific operating conditions, the system prepares the harmonic rejection mixer to operate optimally when transmission starts.
3Reliability
If calibration is performed to cancel harmonic interference, then EVM degradation is reduced, but additional circuitry and complexity are required
Solution Approach 1:
The patent designs the harmonic rejection mixer to serve multiple functions: normal signal mixing during transmission and self-calibration mode for phase adjustment. The same mixer circuits and delay line structure are used for both operations, reducing the need for separate dedicated calibration hardware and minimizing overall circuit complexity.
Data Source
AI summary
An electronic device may include a harmonic rejection mixer with a delay line, mixer array, and load. The delay line may generate LO phases. Each mixer in the array may have a first input that receives an LO phase and a second input coupled to an input switch and the first input of the next mixer circuit through an inter-mixer switch. The load may include a set of switches. In a transmit mode, the input switches and set of switches may be closed while the inter-mixer switches are open. In a self-calibration mode, the input switches and set of switches may be open while the inter-mixer switches are closed. A controller may sweep through phase codes for the programmable delay line while storing a digital output from the load. The controller may calibrate the phase code based on the digital output.