Self-Calibrated Harmonic Rejection Mixer for LO Phase Errors
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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 errors in signal transmission and emission mask violations.
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 and ensuring optimal signal transmission across varying operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a local oscillator is used to generate radio-frequency signals, then signal generation is enabled, but harmonic interference degrades signal quality
Solution Approach 1:
The patent converts the harmful harmonic interference into a useful calibration signal. The system intentionally generates harmonic tones through the mixer and uses these same harmonics as reference signals for calibration. By measuring the phase relationship between fundamental and harmonic components, the system identifies and corrects phase errors, thereby transforming the harmful harmonic distortion into a beneficial calibration mechanism that improves signal quality
Solution Approach 2:
The patent implements a feedback-based calibration mechanism where the system measures the actual phase relationship between LO signals and harmonic components, compares this against ideal values, and adjusts the phase shifters accordingly. The controller continuously monitors signal quality metrics and dynamically adjusts calibration parameters to maintain optimal performance, creating a closed-loop feedback system that actively compensates for harmonic interference
2Reliability
If multiple mixer circuits are used to reject harmonics, then harmonic rejection improves, but device complexity increases
Solution Approach 1:
The patent divides the mixer function into multiple parallel mixer circuits, each handling a specific phase relationship. By segmenting the mixing function across multiple circuits with different phase shifts, the system achieves harmonic rejection through constructive and destructive interference patterns. Each mixer circuit processes a portion of the signal spectrum, and their combined output achieves superior harmonic suppression compared to a single mixer
Solution Approach 2:
The patent employs dynamically adjustable phase shifters in each mixer circuit that can be reconfigured based on operating conditions. The phase shift values are not fixed but can be programmed and adjusted in real-time to optimize harmonic rejection for different frequency bands and operating modes. This dynamic adaptability allows the complex mixer array to be optimized for specific scenarios, managing complexity through programmable control
3Reliability
If phase calibration is performed to cancel harmonic interference, then signal integrity improves, but calibration time is required
Solution Approach 1:
The patent performs phase calibration in advance during manufacturing or initial setup, storing the calibrated phase shift values in memory. These pre-determined calibration parameters are then applied during normal operation without requiring real-time calibration. The system may perform quick refresh calibrations at key operational transitions, but the bulk of calibration work is done preliminarily, minimizing impact on operational time
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively mitigates harmonic interference, reducing error vector magnitude and spectral regrowth, thereby enhancing the quality and integrity of radio-frequency signals transmitted by electronic devices.
Implementation Method 1
The programmable delay line may generate a set of LO phases based on the LO waveforms
Implementation Method 2
The mixer array may generate radio-frequency signals on an output path based on input signals on the input path and the set of LO phases generated by the programmable delay line
Implementation Method 3
The adjustable load may amplify the radio-frequency signals for transmission by an antenna
Implementation Method 4
The mixer array may act as a phase detector and generate a direct current (DC) voltage on the output path based on the LO phases generated by the programmable delay line
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.