Multiphase Local Oscillator Feedback for Precise IQ Phase Control
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Solution Overview
Problem
Conventional local oscillators face challenges in generating accurate IQ signals with phase accuracy of less than 0.5% due to element variation in semiconductor integrated circuit devices, which affects phase noise and spurious characteristics, especially at high frequencies like millimeter waves.
Innovation Solution
A local oscillator design incorporating a frequency generator with a ring-shaped configuration of 2N voltage-controlled oscillators, a phase detector, and a comparator to control the phase difference between sinusoidal signals, ensuring higher phase accuracy by using a phase locked loop and negative feedback mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a multiphase voltage-controlled oscillator is manufactured using a semiconductor integrated circuit device, then the local oscillator can be implemented with compact size and integration, but the phase accuracy deteriorates due to element variation in the chip
Solution Approach 1:
The patent applies feedback control by using a phase detector to monitor the phase difference between signals from different voltage-controlled oscillators and adjusting their control voltages accordingly. The phase detector outputs a voltage proportional to the phase difference, which is fed back to the control voltage inputs of the VCOs to minimize the phase error and maintain accurate IQ signal generation despite manufacturing variations.
Solution Approach 2:
The patent changes the control voltage parameters of the voltage-controlled oscillators dynamically to compensate for phase inaccuracies. By adjusting the control voltages applied to individual VCOs based on their actual phase output, the system compensates for manufacturing variations and maintains the desired 90-degree phase difference between I and Q signals.
2Reliability
If the local source oscillates at twice or four times the desired frequency to avoid signal frequency interference, then phase noise and spurious characteristics improve, but the device complexity increases
Solution Approach 1:
The patent segments the oscillation function across multiple voltage-controlled oscillators operating at the desired frequency, rather than using a single oscillator at a multiplied frequency. Each VCO generates signals at the target frequency with controlled phase relationships, eliminating the need for frequency multiplication circuits and reducing overall device complexity while maintaining reliable phase noise characteristics.
Data Source
AI summary
A local oscillator of the present invention includes: a frequency generator for outputting first and second sinusoidal signals having the same frequency but mutually different phases; a phase detector for outputting either a positive or a negative voltage depending on whether a phase difference between the first and second sinusoidal signals output from the frequency generator is greater than a reference phase difference; and a comparator for outputting a comparison result between a voltage output from the phase detector and a reference voltage, or a comparison result between the voltage output from the phase detector and a voltage obtained by inverting the polarity of the voltage, in which the frequency generator controls the phase of the first sinusoidal signal so that the phase difference approaches the reference phase difference by using the comparison result output from the comparator, enabling generating IQ signals having higher phase accuracy than conventional local oscillators.