Local Oscillator Duty Cycle Feedback for RF Linearity
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Solution Overview
Problem
RF receivers face challenges in tolerating interfering signals, leading to bit error rate degradation and signal-to-noise ratio degradation due to second-order and third-order distortion effects, which affect noise figure and linearity, particularly in adjusting the duty cycle of local oscillator signals.
Innovation Solution
A local oscillator module with a feedback circuit that adjusts the duty cycle of the local oscillator signal by comparing a voltage signal representing the current duty cycle with a desired voltage signal, using a processor to minimize the difference and adjust the pulse width, thereby optimizing noise figure and linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the duty cycle of the local oscillator signal is adjusted to improve linearity and noise figure, then the receiver's ability to tolerate interfering signals improves, but the device complexity increases due to the need for feedback circuits and voltage control mechanisms
Solution Approach 1:
The patent implements a feedback circuit that monitors the duty cycle of the local oscillator signal and adjusts the control voltage accordingly. The feedback circuit compares the actual duty cycle with a target duty cycle and generates an error signal that drives the voltage control mechanism, enabling automatic optimization of linearity and noise figure without manual intervention
Solution Approach 2:
The patent changes the duty cycle parameter of the local oscillator signal dynamically by applying a control voltage that adjusts the pulse width. This parameter change allows the receiver to optimize its performance in terms of linearity and noise figure by operating at different duty cycle points depending on the interference conditions
2Manufacturing precision
If traditional IP2 calibration is performed by adjusting mixer bias voltage using external test equipment, then manufacturing precision improves, but the ease of manufacture deteriorates due to the requirement for specialized external equipment
Solution Approach 1:
The patent enables the receiver to perform its own IP2 calibration without requiring external test equipment. The feedback circuit automatically monitors and adjusts the local oscillator duty cycle based on internal measurements, allowing the device to self-calibrate during manufacturing or operation, thereby simplifying the manufacturing process while maintaining calibration precision
Solution Approach 2:
The patent extracts the calibration function from the external test equipment and integrates it into the receiver itself. By incorporating the feedback circuit and duty cycle control mechanisms within the receiver, the system eliminates the dependency on external calibration equipment, making the calibration process self-contained
3Use of energy by moving object
If the local oscillator duty cycle is optimized for best noise figure performance, then the use of energy improves, but the adaptability deteriorates because the receiver cannot easily adjust to different interference conditions
Solution Approach 1:
The patent makes the local oscillator duty cycle dynamic rather than fixed. The feedback circuit continuously monitors the operating conditions and adjusts the duty cycle in real-time, allowing the receiver to adapt to different interference conditions while maintaining optimal noise figure performance. This dynamic adjustment capability enables the system to respond to changing environmental conditions
Data Source
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AI summary
A local oscillator (LO) module comprises a local oscillator and a feedback circuit. The local oscillator, biased at a supply voltage, generates a local oscillator signal having a duty cycle. The feedback circuit makes an absolute adjustment of the duty cycle of the local oscillator signal in response to a difference between a first voltage signal, representing a voltage level of the local oscillator signal, and a second voltage signal, representing a voltage level of a portion of the supply voltage corresponding to a desired duty cycle for the local oscillator signal.