Direct Conversion Receiver Bimodal DC Offset Compensation
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Solution Overview
Problem
Direct conversion receiver architectures face challenges with dynamic DC offset due to self-mixing of coupled local oscillator signals, leading to bimodal DC offset that disrupts receiver sensitivity, as existing calibration methods are ineffective in real-time and consume significant power.
Innovation Solution
A phase detection and modification system that determines the relative phase of input signals to the mixer, allowing for phase adjustment and voltage compensation to generate a consistent DC signal, transforming dynamic offset into a static offset that can be easily managed, using a swapper and Gilbert cell mixers or alternative phase detection methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If real-time calibration is performed to compensate for bimodal DC offset, then receiver sensitivity is improved, but power consumption increases significantly
Solution Approach 1:
The patent applies preliminary action by performing DC offset calibration once during manufacturing or initial setup, storing the calibrated offset value in memory. This pre-calibration approach eliminates the need for continuous real-time calibration, thereby maintaining receiver sensitivity while significantly reducing power consumption during normal operation.
2Use of energy by moving object
If fixed calibrated DC offset is used, then power consumption is reduced, but the system fails to cope with bimodal DC offset
Solution Approach 1:
The patent applies dynamics by making the DC offset value adjustable and adaptable. The system includes a calibration mode that can update the stored offset value based on detected bimodal conditions, and a run mode that uses this dynamically updated value. This allows the system to adapt to bimodal offset scenarios while maintaining low power consumption during normal operation.
Solution Approach 2:
The patent implements feedback by monitoring the received signal for bimodal DC offset characteristics and using this information to update the calibration value. The system detects whether the current offset compensation is effective and adjusts the stored offset value accordingly, creating a closed-loop system that maintains effectiveness without continuous high power consumption.
3Reliability
If continuous real-time calibration is performed, then DC offset compensation is maintained, but calibration time and complexity increase
Solution Approach 1:
The patent performs DC offset calibration in advance during manufacturing or initial setup, storing the result in memory. This preliminary calibration action eliminates the need for time-consuming continuous calibration during operation, thereby maintaining reliable DC offset compensation while minimizing calibration time loss.
4Measurement precision
If receiver chain is switched on for calibration, then accurate offset measurement is achieved, but power consumption increases
Solution Approach 1:
The patent performs the power-intensive calibration operation with the full receiver chain once during manufacturing or initial setup, storing the measured offset value in memory. During normal operation, the system uses this pre-stored value without needing to switch on the complete receiver chain for calibration, thereby achieving accurate offset measurement initially while minimizing power consumption during subsequent operations.
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 compensates for bimodal DC offset, improving receiver sensitivity and reducing power consumption by transforming dynamic offset into a static offset that can be calibrated efficiently, allowing for consistent signal processing without the need for continuous real-time calibration.
Implementation Method 1
self-mixing of a coupled local oscillator (LO) signal to a low noise amplifier (LNA) input
Implementation Method 2
local oscillator energy that leaks back to the antenna via electromagnetic coupling
Data Source
AI summary
Apparatus for controlling the generation of a DC signal at the output of a mixer, so that the DC signal is predictable, enabling a static offset compensation voltage to offset the DC signal. The apparatus comprises a mixer configured to receive a first and a second input signal, the mixer being such as to generate a first DC signal at the output of the mixer when the first and second input signals have the same frequency and a first relative phase, a phase detector for determining the relative phase of the first and second signals, and a phase modifier configured to modify the phase of the second signal relative to the first signal in dependence on the determination of the relative phase between the first and second signals such that the resulting DC signal at the output of the mixer is the first DC signal.