RF Phase Shifter Cell With Integrated Isolation and Low Insertion Loss
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Solution Overview
Problem
Conventional RF phase shifter circuits face challenges in achieving high isolation without introducing insertion loss and maintaining good return loss, especially for systems requiring high-resolution phase shifting and calibration.
Innovation Solution
The integration of a high-isolation function within the phase shifter circuit using independent switch control signals and a switchable shunt termination resistor, allowing for a distinct high-isolation state without adding insertion loss, and reducing die area by breaking the complementary nature of control signals and enabling synergistic interaction with attenuator circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional isolation switches are used in phase shifter circuits, then isolation between ports is improved, but insertion loss increases
Solution Approach 1:
The patent combines the isolation switch and phase shifter into a single integrated unit cell. The isolation function is achieved by controlling the state of the phase shifter components (switches and reactive elements) rather than using a separate isolation switch, thereby eliminating the need for additional isolation components that would introduce insertion loss.
Solution Approach 2:
The phase shifter unit cell performs multiple functions: phase shifting and isolation. By making the unit cell universal, it can operate in different modes (phase shift mode and isolation mode) depending on the control signals applied, eliminating the need for separate dedicated isolation switches.
2Measurement precision
If multiple phase shifter unit cells are serially connected to achieve high-resolution phase shifting, then phase shift precision is improved, but die area increases
Solution Approach 1:
The patent merges multiple functions (phase shifting and isolation) into a single unit cell, making each unit cell more versatile. This allows achieving the same overall functionality with fewer unit cells, thereby reducing the total die area while maintaining phase shift precision.
Solution Approach 2:
By making each unit cell universal (capable of both phase shifting and isolation), the patent reduces the total number of unit cells needed in the system. Fewer unit cells mean reduced die area while maintaining the required phase shift resolution through alternative configurations.
3Object-affected harmful factors
If conventional phase shifter circuits are used, then phase shifting function is provided, but return loss deteriorates when isolation is enhanced
Solution Approach 1:
The patent combines isolation and phase shifting functions in a way that the same components serve dual purposes. The integrated design allows the circuit to achieve isolation without compromising return loss by coordinating the state of all components within the unit cell.
Solution Approach 2:
The patent uses dynamic control of the unit cell components through control signals to achieve different operational states (phase shift modes and isolation mode). This dynamic adjustment allows the circuit to optimize both isolation and return loss performance by transitioning between different configurations.
Data Source
AI summary
A phase shifter unit cell or a connected set of such cells that can be well isolated from external circuitry and which do not introduce insertion loss into an RF signal path, exhibit good return loss, and further provides additional advantages when combined with bracketing attenuator circuits. More particularly, embodiments integrate a high-isolation function within a phase shifter circuit by breaking the complimentary nature of the control signals to a phase shifter cell to provide greater control of switch states internal to the phase shifter cell and thus enable a distinct high-isolation state, and by including a switchable shunt termination resistor for use in the high-isolation state. Some embodiments are serially coupled to attenuator circuits to enable synergistic interaction that reduces overall die size and/or increases isolation. One such embodiment positions a high-isolation phase shifter cell in accordance with the present invention between bracketing programmable attenuators.