Transceiver Calibration via Substrate Coupling
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Solution Overview
Problem
In WiGig transceivers operating at 60 GHz, parasitic capacitance causes undesirable coupling between RF transmit and receive chains, leading to amplitude variations and phase differences between I/Q signals, which is challenging to maintain over a range of frequencies, often requiring additional circuitry that increases die area, power dissipation, and complexity.
Innovation Solution
The use of a Substrate-Reactive-Coupled (SRC) network within the die to estimate and calibrate I/Q signal imbalances, LO leakage, and LPF cutoff frequencies, leveraging digital block components like processors and memory for estimation and compensation, eliminating the need for additional circuitry and reducing switching noise influence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additional circuitry is used to maintain I/Q signal balance and minimize parasitic coupling effects, then signal quality is improved, but die area and device complexity increase
Solution Approach 1:
The transceiver uses its own existing RF chains to perform calibration. The receive chain measures LO leakage and I/Q imbalance by receiving signals from the transmit chain through substrate coupling. This self-service approach eliminates the need for separate calibration circuitry while maintaining signal quality.
Solution Approach 2:
The RF chains serve dual purposes: normal RF transmission/reception operations and calibration measurements. The same hardware components (mixers, amplifiers, ADCs/DACs) are used for both communication and calibration, reducing overall device complexity.
2Measurement precision
If additional calibration circuitry is added, then measurement precision is improved, but power dissipation increases
Solution Approach 1:
The calibration process uses the existing RF chains already powered for normal operation. No additional powered calibration components are introduced, so power dissipation remains at the level of normal RF operation while achieving precise calibration measurements.
3Device complexity
If substrate coupling is used for calibration, then device complexity is reduced, but harmful coupling effects increase
Solution Approach 1:
The patent converts the harmful substrate coupling effect into a beneficial calibration mechanism. The same substrate coupling that causes unwanted signal interference is used to transfer calibration signals from the transmit chain to the receive chain, enabling precise measurements of LO leakage and I/Q imbalance.
Solution Approach 2:
The system performs calibration measurements before normal RF operation begins. By characterizing the substrate coupling effects and compensating for them during calibration, the system prepares correction data that is applied during normal operation to maintain signal quality.
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 allows for reduced amplitude variations and maintained 90° phase separation between I/Q signals, minimizing LO leakage and optimizing LPF bandwidths, thereby achieving smaller die size, lower power dissipation, and faster performance without increasing chip cost or battery drain.
Implementation Method 1
parasitic capacitance can transfer these high frequency signals into other circuit components of the system design causing undesirable effects, particularly through substrate coupling
Implementation Method 2
signals are coupled between the RF transmit and RF receive chains via the substrate reactances, substrate impedances and surface metal reactances
Data Source
AI summary
Transceiver calibration is a critical issue for proper transceiver operation. The transceiver comprises at least one RF transmit chain and one RF receive chain. A closed loop path is formed from the digital block, the RF transmit chain, the substrate coupling, the RF receive chain back to the digital block and is used to estimate and calibrate the transceiver parameters over the operating range of frequencies. The substrate coupling eliminates the need for the additional circuitry saving area, power, and performance. In place of the additional circuitry, the digital block which performs baseband operations can be reconfigured into a software or/and hardware mode to calibrate the transceiver. The digital block comprises a processor and memory and is coupled to the front end of the RF transmit chain and the tail end of the RF receive chain.