Mixer Temperature Compensation for Stable Second-Order Intercept
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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, which is not adequately compensated by existing calibration methods.
Innovation Solution
A replica mixer circuit and temperature compensation circuit are used to generate a reference voltage that tracks the common mode and threshold voltage of transistors, adjusting bias and threshold voltages to compensate for temperature changes, and a temperature coefficient is applied to the calibration circuit to further mitigate these variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibration circuit is used to compensate for transistor mismatch, then second-order nonlinearity is reduced at a specific temperature, but performance degrades rapidly across temperature variations
Solution Approach 1:
The patent applies dynamics by making the compensation value adjustable based on temperature. The system dynamically selects different compensation values from a lookup table or applies temperature-dependent scaling factors to the calibration circuit, allowing the compensation to adapt to temperature changes rather than being fixed. This resolves the contradiction by enabling the system to maintain high measurement precision across varying temperature conditions.
Solution Approach 2:
The patent changes the parameter of the compensation value based on temperature. Specifically, it either looks up temperature-appropriate compensation values from a pre-stored table or calculates scaled compensation values using temperature-dependent factors. This parameter change allows the calibration circuit to maintain effective compensation across temperature variations, preventing performance degradation.
2Manufacturing precision
If fixed compensation value is applied to calibration circuit, then transistor threshold voltage mismatch is compensated at calibration temperature, but temperature variations cause performance decline
Solution Approach 1:
The system dynamically adjusts the compensation value based on real-time temperature measurements. A temperature sensor monitors the mixer temperature, and the controller selects or calculates the appropriate compensation value from a lookup table or using scaling factors. This dynamic adjustment maintains transistor threshold voltage matching across temperature variations.
Solution Approach 2:
The patent performs preliminary action by pre-calculating and storing compensation values for various temperatures in a lookup table during the manufacturing or calibration phase. When the system operates, it simply retrieves the pre-computed compensation value corresponding to the current temperature, avoiding the need for real-time complex calculations while maintaining precision.
3Reliability
If temperature compensation is implemented using lookup table or scaling factors, then second-order intercept point stability is improved across temperatures, but device complexity increases
Solution Approach 1:
The patent reduces complexity by performing preliminary calculations during manufacturing or initial calibration, storing the results in a compact lookup table. During operation, the system only needs to read the temperature, select the corresponding compensation value from the table, and apply it to the calibration circuit. This approach maintains high reliability while avoiding complex real-time calculations.
Solution Approach 2:
The system creates a simplified model of temperature-dependent compensation behavior by copying pre-calculated compensation values into a lookup table. Instead of implementing complex real-time temperature modeling and calculation hardware, the system uses this copied data structure to achieve the same effect with minimal computational overhead and reduced device complexity.
Data Source
AI summary
The present disclosure relates to compensating for temperature variation of a mixer. Embodiments herein may include the mixer, a calibration circuit coupled to the mixer, a replica mixer circuit coupled to the calibration circuit, and a temperature compensation circuit coupled to the calibration circuit. The replica mixer circuit may generate or be used to generate a reference voltage that varies with a common mode voltage and/or a threshold voltage of a replica mixer. The reference voltage may be applied to a resistor ladder of the calibration circuit to adjust a bias voltage and compensate for temperature variations. Further, the temperature compensation circuit may generate a temperature coefficient that may be applied to a current going through the calibration circuit to facilitate compensating for temperature variation.