Digital-Analog Phase Shifter for Continuous RF Control
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Solution Overview
Problem
Existing phase shifters, both digital and analog, face limitations in providing continuous phase shifts over the full 360° range with minimal insertion loss and power requirements, as digital shifters have discrete resolution and thermal issues, while analog shifters are limited by breakdown voltage and signal loss.
Innovation Solution
A digital-analog phase shifter combines a digital shifter for coarse phase shifts with an analog shifter using varactors to provide continuous phase shifts from 0° to 360°, minimizing signal loss by varying the phase within predetermined ranges and utilizing overlapping phase shift ranges to optimize signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If digital shifters are used to provide discrete phase shifts, then the phase shifting capability is improved, but the resolution is limited and thermal interference problems occur due to current control requirements
Solution Approach 1:
The phase shifter is divided into multiple bits, where each bit controls a separate pin diode switch that selects between different discrete phase shift states. This segmentation allows the system to achieve multiple discrete phase levels (e.g., 4 states for 2-bit, 8 states for 3-bit) while maintaining digital control capability
Solution Approach 2:
Pin diodes are introduced as intermediary switching elements between the control signal and the phase shift implementation. These pin diodes act as controlled resistors that can be switched between high and low resistance states to select different phase shift paths without requiring direct current control through the entire phase shifter chain
2Measurement precision
If more bits are added to digital shifters to increase resolution, then the number of discrete phase states increases, but insertion loss increases with the number of bits and frequency
Solution Approach 1:
The patent uses a 3-bit digital shifter providing 8 discrete states, which may be more resolution than strictly necessary for some applications. This partial over-provisioning of resolution allows the system to achieve fine phase control while the low-loss transmission line design compensates for the increased complexity
3Measurement precision
If analog shifters using varactors are used to provide continuous phase shifts, then continuous phase adjustment is improved, but the phase range is limited by breakdown voltage
Solution Approach 1:
The patent changes the control parameter from voltage-dependent capacitance (varactor) to physical path length selection (digital). By using transmission lines with different electrical lengths and pin diode switches to select between them, the system achieves both continuous effective phase control and full 360-degree range without breakdown voltage limitations
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 enables continuous and precise phase shifting over the full 360° range with reduced signal loss and minimal power consumption, addressing the limitations of both digital and analog shifters by leveraging the strengths of digital coarse shifts and analog continuous variations.
Implementation Method 1
Varactors operate in a reverse biased condition providing a junction capacitance that varies based on applied voltage
Implementation Method 2
Each of the four transmission lines can have a different characteristic impedance and/or different electrical length
Data Source
AI summary
A phase shifter having both digital and analog shifting components is disclosed. The digital-analog phase shifter includes an input/output port configured, in part, for receiving an input radio frequency (RF) signal from an external source and outputting a phase shifted RF signal. A digital shifter performs coarse phase shifts of the input RF signal, while an analog shifter variably shift the phase of the input RF signal relative to the coarse phase shift. This produces a phase shifted RF signal having a total phase range that is output is continuously variable from 0° to 360°.