Mixer IIP2 Temperature Compensation Using Replica Bias Tracking
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Solution Overview
Problem
Mixer performance in transceivers is affected by temperature variations due to mismatched switching threshold voltages of transistors, leading to second-order nonlinearity and a decline in performance across temperatures, which existing calibration methods fail to adequately address.
Innovation Solution
A replica mixer circuit generates a reference voltage that tracks the common mode and threshold voltage of transistors, coupled with a temperature compensation circuit to adjust bias and threshold voltages, using PTAT and NTAT current sources to compensate for temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a calibration circuit is used to compensate for mismatched transistors, then second-order nonlinearity is reduced at a specific temperature, but performance deteriorates across temperature variations
Solution Approach 1:
The patent implements dynamic temperature compensation by introducing temperature-dependent biasing circuits that automatically adjust compensation values based on operating temperature. The system transitions from static calibration to dynamic adaptation, where compensation parameters are modulated according to temperature sensors or PTAT (Proportional To Absolute Temperature) circuits, ensuring optimal performance across varying thermal conditions.
Solution Approach 2:
The patent changes the operational parameters of the calibration circuit by introducing temperature-compensated bias voltages and currents. By modifying bias conditions based on temperature, the system maintains transistor matching accuracy across temperature ranges. This involves adjusting gate-source voltages, drain currents, or other critical parameters dynamically to counteract temperature-induced drift.
2Measurement precision
If standard calibration methods are applied, then second-order intercept point is improved at calibration temperature, but IIP2 variation increases across temperature range
Solution Approach 1:
The patent implements feedback mechanisms where temperature sensors monitor operating conditions and feed this information back to the calibration circuit. This feedback loop enables real-time adjustment of compensation parameters, allowing the system to maintain optimal IIP2 performance dynamically. The feedback ensures that as temperature changes, the calibration parameters are automatically retuned to compensate for drift.
Solution Approach 2:
The patent applies preliminary temperature compensation by pre-characterizing transistor mismatch behavior across temperature ranges during manufacturing. Based on this pre-characterization, the system pre-configures compensation parameters or lookup tables that anticipate temperature-induced variations. This preliminary action allows the calibration circuit to proactively adjust for expected drift before it significantly degrades performance.
Data Source
AI summary
The present disclosure relates to compensating for temperature variation of a mixer. Embodiments herein may include performing a single-point Fast Fourier Transform (FFT) (or complex downconversion with DC average) for a number of samples to obtain a transform for each of the number of samples, phase aligning a set of phases associated with each transform, and averaging each transform to generate an analog-to-digital converter (ADC) power value. Further, the disclosed embodiments may include generating a compensation value based on the analog-to-digital converter power value and applying the compensation value to the calibration circuit of the mixer to compensate for a second-order intermodulation product.