VCO Phase Shifter Layout for Wide Frequency Tuning
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Solution Overview
Problem
Voltage-controlled oscillators with a wide frequency variable range face challenges in increasing circuit area, complexity, and transmission loss when attempting to achieve a 0°≤Φ<360° variable range for phase shifters, leading to reduced oscillation frequency variability.
Innovation Solution
A voltage-controlled oscillator design incorporating first and second LC tanks, magnetically coupled secondary inductors, a negative resistance circuit generating opposite-phase AC voltages, and phase adjusters to limit the phase shift range of variable phase shifters to 0°≤Φ<180°, reducing the need for extensive circuit area and complexity while maintaining a wide variable range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the phase shifter variable range is extended to 0°≤Φ<360° to achieve wide frequency tuning, then the oscillation frequency variable range increases, but the circuit area and complexity increase significantly
Solution Approach 1:
The phase adjustment function is segmented into two independent parts: a fixed phase shifter providing 180° phase shift and a variable phase shifter providing 0°≤Φ<180° phase shift. This segmentation allows the variable phase shifter to operate within a limited range while the fixed phase shifter provides the additional 180° shift, achieving the equivalent effect of a 360° variable phase shifter without the associated complexity and area overhead.
Solution Approach 2:
The fixed phase shifter and variable phase shifter are combined in series to achieve the total phase shift. The fixed phase shifter using transmission lines with specific impedance and length provides a stable 180° phase shift, while the variable phase shifter provides the controllable 0°≤Φ<180° phase shift. This merging allows the system to achieve wide frequency tuning range without requiring a complex 360° variable phase shifter.
2Adaptability or versatility
If the phase shifter variable range is extended to 0°≤Φ<360° to achieve wide frequency tuning, then the oscillation frequency variable range increases, but the transmission loss increases
Solution Approach 1:
By segmenting the phase adjustment into a fixed phase shifter using transmission lines and a variable phase shifter, the transmission loss is minimized. The fixed phase shifter using transmission lines with characteristic impedance of 50Ω and length of λ/4 provides low-loss 180° phase shift, while the variable phase shifter operates within a limited range reducing its contribution to transmission loss.
3Adaptability or versatility
If a single large variable phase shifter with 0°≤Φ<360° range is used, then wide frequency tuning is achieved, but the circuit area increases
Solution Approach 1:
The phase adjustment function is divided into a fixed phase shifter using compact transmission lines and a variable phase shifter with limited range. This segmentation allows the use of space-efficient transmission line structures for the fixed 180° phase shift while the variable phase shifter only needs to cover 0°≤Φ<180°, significantly reducing the total circuit area compared to a single 360° variable phase shifter.
Solution Approach 2:
The fixed phase shifter uses transmission lines with specific impedance and length to provide phase shift in a different dimension (spatial arrangement) rather than using a large variable phase shifter structure. This dimensional approach allows compact implementation of the 180° phase shift function.
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 configuration allows for a wide variable range of oscillation frequencies while minimizing circuit area, complexity, and transmission loss, extending the oscillation frequency range from 48 GHz to 105 GHz.
Implementation Method 1
a negative resistance circuit that generates first and second AC voltages having opposite phases in first and second connection nodes to which the first and second LC tanks are connected
Implementation Method 2
a first secondary inductor that is magnetically coupled to a first primary inductor included in the first LC tank, a second secondary inductor that is magnetically coupled to a second primary inductor included in the second LC tank
Data Source
AI summary
A first phase adjuster adjusts the phase of any one of first and second AC voltages generated in a negative resistance circuit so that a shift amount Φ in a first variable phase shifter falls within a range of 0 degrees≤Φ<180 degrees, and outputs the phase-adjusted AC voltage to the first variable phase shifter, and a second phase adjuster adjusts the phase of the other one of the first and second AC voltages generated in the negative resistance circuit so that a shift amount Φ in a second variable phase shifter falls within a range of 0 degrees≤Φ<180 degrees, and outputs the phase-adjusted AC voltage to the second variable phase shifter.