Mixer Feedthrough Calibration Using On-Chip LO Leakage Detection
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Solution Overview
Problem
Local oscillator feedthrough (LOFT) adversely impacts wireless signal processing by leaking into communication chains, limiting system throughput and increasing error vector magnitude, especially in mmW massive phase-array systems, and existing solutions rely on expensive external RF equipment for calibration.
Innovation Solution
Incorporating a mixer circuit with tuning circuitry that applies a calibration signal to counteract LOFT by detecting power levels using onboard power detectors and controller circuitry, allowing for reduction of LOFT without external testing equipment, using current sources or voltage adjustments to minimize leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external RF equipment is used for calibration, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The mixer circuit performs self-calibration by using its own local oscillator signal and internal power detector to generate and apply calibration signals, eliminating the need for external RF equipment. The circuit autonomously adjusts its parameters to compensate for LOFT without external intervention.
Solution Approach 2:
An on-chip power detector serves as an intermediary element that bridges the mixer output and the control logic, enabling the system to measure power levels and adjust calibration parameters internally. This intermediary component allows precise measurement without external equipment.
2Device complexity
If LOFT is not calibrated, then device complexity is reduced, but signal quality and reliability deteriorate
Solution Approach 1:
The calibration circuit performs preliminary adjustment of mixer parameters before normal signal processing begins. By pre-compensating for LOFT effects through tuning circuitry adjustment, the system ensures reliable signal processing without adding complexity to the main signal path.
Solution Approach 2:
The calibration process involves changing electrical parameters (voltage, current, or frequency) of mixer components through tuning circuitry to optimize performance and reduce LOFT. These parameter adjustments are made automatically based on detected power levels without mechanical or structural modifications.
3Object-affected harmful factors
If calibration signals are applied continuously, then LOFT reduction is improved, but energy consumption increases
Solution Approach 1:
The calibration signal is applied periodically or at specific intervals rather than continuously. The power detector monitors LOFT levels and triggers calibration adjustments only when necessary, reducing energy consumption while maintaining effective LOFT suppression during critical operation periods.
Solution Approach 2:
The system uses feedback from the power detector to determine when calibration is needed. The detected power level feeds back to the controller, which adjusts the tuning circuitry only when LOFT exceeds acceptable thresholds, optimizing the balance between LOFT reduction and energy consumption.
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 approach effectively reduces LOFT without external equipment, enhancing wireless performance characteristics like EVM and ERP, and is applicable across various frequency bands, including mmW frequencies, thereby improving the efficiency of wireless communication systems.
Implementation Method 1
A power detector is coupled to a point along the communication chain to detect a power level and provide the power level to controller circuitry
Data Source
AI summary
An apparatus is disclosed for oscillator feedthrough calibration, such as a component arrangement that can be calibrated to account for signal leakage from an oscillator coupled to a mixer circuit. In example aspects, the apparatus includes a mixer circuit having a first stage, a second stage, and tuning circuitry. The first stage includes at least one transistor coupled between a mixer input and a mixer output. The second stage includes one or more transistors coupled between the at least one transistor of the first stage and the mixer output. The one or more transistors are also coupled between a local oscillator signal input and the mixer output. The tuning circuitry includes at least one current source coupled to the at least one transistor of the first stage.