Third-Harmonic 60 GHz Frequency Generator Without 60 GHz Divider
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Solution Overview
Problem
Current 60 GHz frequency generators face challenges in achieving low phase noise, wide tuning range, and high power efficiency due to poor Q-factor, limited locking range, and high power consumption, which are critical for high data-rate wireless communications.
Innovation Solution
A phase-locked loop frequency generator employing an implicit divide by three divider and third harmonic boosting technique, which generates both fundamental and third harmonic frequencies, allowing for improved system efficiency and phase noise reduction by rejecting the fundamental harmonic and amplifying the third harmonic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional 60 GHz oscillator is used, then the frequency generation is achieved, but the phase noise is poor and power consumption is high
Solution Approach 1:
The patent replaces the conventional mechanical/electronic frequency division approach with a third-harmonic extraction technique. Instead of using a traditional divider circuit operating at 60 GHz, the invention extracts the third harmonic of a 20 GHz oscillation to generate the 60 GHz signal, thereby avoiding the need for high-frequency division and reducing power consumption while improving phase noise performance.
Solution Approach 2:
The patent changes the operating parameters by oscillating at one-third of the desired output frequency (20 GHz instead of 60 GHz) and then extracting the third harmonic. This parameter transformation allows the use of lower-frequency components with better Q-factor and lower power consumption to achieve the 60 GHz output with superior phase noise characteristics.
2Speed
If the oscillation frequency is increased to 60 GHz, then the carrier frequency is achieved, but the Q-factor decreases and tuning range is limited
Solution Approach 1:
The patent segments the frequency generation process into two stages: first generating a 20 GHz oscillation with high Q-factor, then extracting the third harmonic to obtain 60 GHz. This segmentation allows the resonant tank to operate at the lower frequency where it can achieve better Q-factor, while still producing the required 60 GHz carrier through harmonic extraction.
Solution Approach 2:
The patent introduces a third-harmonic extraction mechanism as an intermediary between the 20 GHz oscillation and the 60 GHz output. This intermediary process allows the system to benefit from the high Q-factor of the 20 GHz resonant tank while achieving the desired 60 GHz carrier frequency, effectively bridging the gap between low-frequency stability and high-frequency performance.
3Ease of operation
If a frequency divider is used at 60 GHz, then the phase detection is enabled, but the device complexity increases and power consumption rises
Solution Approach 1:
The patent replaces the conventional 60 GHz frequency divider with a third-harmonic extraction approach. By oscillating at 20 GHz and extracting the third harmonic, the system eliminates the need for complex high-frequency division circuits, thereby reducing device complexity and power consumption while maintaining phase detection capability through the implicit frequency relationship.
4Area of stationary object
If the resonant tank components are reduced in size, then the circuit area is minimized, but the sensitivity to parasitics increases
Solution Approach 1:
The patent segments the frequency multiplication function from the oscillation generation, allowing the resonant tank to be optimized for 20 GHz operation with larger, less parasitic-sensitive components. The third-harmonic extraction process then provides the frequency multiplication without requiring the resonant tank to be miniaturized for 60 GHz operation, thus reducing parasitic sensitivity while maintaining compact overall design.
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 provides a phase noise of -100dBc/Hz at 1 MHz offset and a 25% tuning range, with reduced power consumption and improved harmonic rejection, addressing the limitations of prior art 60 GHz frequency generators.
Implementation Method 1
a transformer based LC tank circuit operative to generate a feedforward signal containing both a fundamental frequency component and a third harmonic component
Implementation Method 2
the oscillator operative to generate a feedback signal containing substantially only the fundamental frequency component
Data Source
Figure 1~3
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Figure 7~9
AI summary
A novel and useful 60 GHz frequency generator based on a third harmonic extraction technique which improves system level efficiency and performance. The frequency generator employs a third harmonic boosting technique to increase the third harmonic at the output of the oscillator. The oscillator generates both ~20 GHz fundamental and a significant amount of the third harmonic at ~60 GHz and avoids the need for a frequency divider operating at 60 GHz. The undesired fundamental harmonic at ~20 GHz is rejected by the good fundamental HRR inherent in the oscillator buffer stage while the ~60 GHz component is amplified to the output. The fundamental harmonic is further suppressed by an active cancellation by properly combining the two outputs. The oscillator fabricated in 40nm CMOS exhibits a phase noise of -100 dBc/Hz at 1 MHz offset from a 60 GHz carrier and have a tuning range of 25%.