Planar Differential Inductor for VCO Common Mode Stability
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Solution Overview
Problem
In mobile RF transceivers, achieving precise control over differential and common mode inductance in voltage controlled oscillators (VCOs) is challenging due to the impact of external parasitics on common mode inductance, which affects phase noise performance and data throughput.
Innovation Solution
A planar differential inductor design that includes a ground plane, routing lines, a bypass capacitor array, an exterior inductor structure, and an interior inductor structure, where the exterior inductor structure is coupled between the routing lines and a power supply, and the interior inductor is within the ground plane, coupled between the routing lines and differential ports, effectively isolating the common mode inductance from external parasitics by providing a strong on-chip AC ground.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If external routing and packaging are used for common mode ground, then device functionality is achieved, but parasitic effects significantly degrade common mode inductance performance
Solution Approach 1:
The common mode ground connection is extracted from the external routing and packaging domain and brought into the chip interior, where it can be controlled without exposure to external parasitics
Solution Approach 2:
The common mode ground path is implemented in a different spatial dimension (within the chip substrate rather than external traces), eliminating the harmful coupling with external parasitic elements
Data Source
AI summary
A planar differential inductor reduces an effect of parasitics on common mode inductance of a voltage controlled oscillator (VCO)-based inductor to properly ground a common mode alternating current (AC) ground. In one instance, the planar differential inductor includes a ground plane, routing lines, distributed capacitors, an exterior inductor structure, and an interior inductor structure. The planar differential inductor may be coupled to a capacitor as part of an LC tank that operates as a resonator within a VCO. The bypass capacitor array is coupled between the ground plane and the routing lines. The exterior inductor structure is coupled between the routing lines and a power supply. The interior inductor is within the ground plane and coupled between the routing lines and differential ports.