Transformer-Coupled VCO and Divider for Low Phase Noise
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Solution Overview
Problem
Existing voltage-controlled oscillator (VCO) circuits in wireless communications systems face challenges in reducing power consumption and minimizing phase noise, particularly in GSM and CDMA systems, where the frequency divider contributes significantly to phase noise, and separating VCO and mixer circuits consume substantial power.
Innovation Solution
The integration of a voltage-controlled oscillator (VCO) with a mixer or frequency divider, utilizing a transformer-based design where transistors are DC biased with shared bias currents, and inductances are magnetically coupled to reduce power consumption and phase noise, with variable capacitance coupling the gates of transistors to minimize voltage headroom and isolate LC tank elements from the mixer or frequency divider.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a frequency divider circuit is used to divide down the VCO output frequency, then the LO output frequency can be adjusted, but the frequency divider contributes significant phase noise to the LO output
Solution Approach 1:
The patent merges the VCO and frequency divider into a single integrated circuit block, sharing common bias currents and circuit elements. This integration reduces the overall phase noise by eliminating isolation requirements and allowing optimized internal signal paths, while maintaining frequency division functionality.
Solution Approach 2:
The integrated circuit serves multiple functions: generating the VCO output signal, dividing the frequency, and providing the LO output. By combining these functions in one block with shared bias currents and circuit elements, the design achieves frequency adjustment capability while minimizing phase noise contributions.
2Reliability
If a VCO buffer is provided between the VCO output and the frequency divider or mixer, then the VCO output is isolated from subsequent loads, but the VCO buffer consumes significant power
Solution Approach 1:
The patent eliminates the separate VCO buffer by integrating the frequency divider directly with the VCO circuit. The frequency divider is designed to interface directly with the VCO output without requiring isolation buffering, thereby reducing power consumption while maintaining proper signal coupling.
Solution Approach 2:
The patent removes the VCO buffer component from the signal path by redesigning the frequency divider to directly interface with the VCO output. This extraction of the buffer element eliminates its power consumption while the integrated design maintains necessary signal isolation through direct coupling.
3Ease of manufacture
If the VCO and mixer are provided as separate circuit blocks, then the functions are clearly defined, but the power consumption is significant
Solution Approach 1:
The patent merges the VCO and mixer into a single integrated circuit block that shares common bias currents and circuit elements. This integration maintains clear functional definition through internal signal paths while significantly reducing power consumption by eliminating redundant components and optimizing current reuse.
4Object-generated harmful factors
If the phase noise of the frequency divider is reduced by conventional methods, then the far-offset phase noise improves, but a great deal of power is consumed
Solution Approach 1:
By integrating the frequency divider with the VCO and sharing bias currents, the patent reduces far-offset phase noise through optimized internal signal paths and reduced isolation requirements. The shared circuit elements allow for lower power consumption while maintaining phase noise performance through careful current reuse and minimized noise coupling.
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 reduces power consumption by current reuse and minimizes both near-offset and far-offset phase noise, achieving efficient power management and improved phase noise performance without increasing the supply voltage or die area.
Implementation Method 1
at least one gate inductance coupling the gate of the first transistor to the gate of the second transistor
Implementation Method 2
a first drain inductance magnetically coupled to a gate inductance, the first drain inductance coupled to the drain of the first transistor; a second drain inductance magnetically coupled to a gate inductance, the second drain inductance coupled to the drain of the second transistor
Data Source
AI summary
Techniques for providing voltage-controlled oscillator circuits having improved phase noise performance and lower power consumption. In an exemplary embodiment, a voltage controlled oscillator (VCO) is coupled to a mixer or a frequency divider such as a divide-by-two circuit. The VCO includes a transistor pair with magnetically cross-coupled inductors, and variable capacitance coupled to the gates of the transistor pair. In an exemplary embodiment, a frequency divider is configured to divide the frequency of the differential current flowing through the transistor pair to generate the LO output. In an alternative exemplary embodiment, a mixer is configured to mix the differential current flowing through the transistor pair with another signal. The VCO and mixer or frequency divider share common bias currents, thereby reducing power consumption. Various exemplary apparatuses and methods utilizing these techniques are disclosed.