Dual-PLL IQ Signal Source for Accurate 90° Phase Control
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Solution Overview
Problem
Conventional IQ signal sources using quadrature voltage-controlled oscillators (Q-VCOs) face accuracy issues due to mismatch variations in integrated circuit elements, leading to errors in the phase difference between in-phase and quadrature signals, which cannot be effectively compensated.
Innovation Solution
An IQ signal source comprising a quadrature voltage-controlled oscillator formed by two voltage-controlled oscillators, a first phase locked loop for frequency comparison, and a second phase locked loop to detect and converge the phase difference to 90 degrees, using a phase detector, comparator, and filter circuit to adjust the control voltages and improve phase accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a Q-VCO is constituted by an integrated circuit, then device integration is achieved, but mismatch variation occurs causing IQ phase difference error
Solution Approach 1:
The patent employs feedback control through two phase-locked loops (PLLs) that continuously monitor and adjust the phase difference between I and Q signals. The first PLL compares the frequency of the local oscillation signal with a reference signal, while the second PLL detects the phase difference and adjusts control voltages to maintain 90-degree phase difference, compensating for mismatch variations in integrated circuit elements.
Solution Approach 2:
The patent dynamically changes the control voltage parameters applied to the VCOs based on detected phase and frequency errors. By adjusting these voltage parameters through the PLL control circuits, the system compensates for manufacturing mismatches and maintains accurate quadrature phase relationship despite integrated circuit variations.
2Device complexity
If conventional Q-VCO is used without compensation, then device complexity is low, but IQ phase difference accuracy deteriorates
Solution Approach 1:
The patent introduces feedback control through two phase-locked loops (PLLs) that continuously monitor and adjust the phase difference between I and Q signals. The first PLL compares the frequency of the local oscillation signal with a reference signal, while the second PLL detects the phase difference and adjusts control voltages to maintain 90-degree phase difference, compensating for mismatch variations in integrated circuit elements.
Solution Approach 2:
The patent introduces intermediary control circuits (two PLLs) that mediate between the reference signal and the VCO outputs. These intermediary circuits process frequency and phase information, generating control voltages that adjust the VCOs to maintain accurate quadrature relationship, thus bridging the gap between simple VCO structure and high phase accuracy requirements.
3Speed
If frequency division system is used at tens of GHz, then local signal oscillation is achieved, but oscillator realization becomes difficult
Solution Approach 1:
The patent introduces intermediary control circuits (two PLLs) that mediate between the reference signal and the VCO outputs. These intermediary circuits process frequency and phase information, generating control voltages that adjust the VCOs to maintain accurate quadrature relationship, thus bridging the gap between simple VCO structure and high phase accuracy requirements.
Solution Approach 2:
The patent replaces traditional frequency division methods with voltage-controlled oscillators that are directly controlled by PLL circuits. This substitution of control mechanism enables stable high-frequency operation (tens of GHz) by using voltage control rather than mechanical or electronic frequency division, which becomes difficult to realize at such high frequencies.
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
The solution effectively compensates for mismatch variations, enhancing the accuracy of the IQ phase difference to within 0.5 degrees, thereby improving the overall phase difference accuracy in IQ signal sources.
Implementation Method 1
a first phase locked loop to compare a frequency of the in-phase signal or the quadrature signal with a frequency of a reference signal input from the outside of the IQ signal source and to output a voltage depending on a result of the comparison
Implementation Method 2
a second phase locked loop to detect a phase difference between the in-phase signal and the quadrature signal and to output a voltage depending on the phase difference
Implementation Method 3
outputting an in-phase signal and a quadrature signal by electrically coupling the first voltage controlled oscillator and the second voltage controlled oscillator with each other
Data Source
AI summary
An IQ signal source (100) includes: a Q-VCO (3) having a first VCO (1) and a second VCO (2), the IQ signal source (100) outputting an I signal and a Q signal by electrically coupling the first VCO (1) and the second VCO (2) with each other; a first PLL (10) for comparing a frequency of the I signal or the Q signal with a frequency of a reference signal input from the outside of the IQ signal source (100) and outputting a voltage depending on a result of the comparison; and a second PLL (9) for detecting an IQ phase difference and outputting a voltage depending on the IQ phase difference. The IQ phase difference converges to 90 degrees in dependence on the output voltage of the first PLL (10) and the output voltage of the second PLL (9).