Passive Vector-Interpolating Phase Shifter for Fine CMOS Beam Steering
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Solution Overview
Problem
Phased array antennas face challenges in achieving fine resolution phase shifting and stability over temperature variations and process variations, while also requiring low power consumption and small form factor, especially in satellite communications and airborne applications.
Innovation Solution
A high-resolution phase shifter is designed using low insertion loss phase-inverting variable attenuators, which are configured to provide fine phase-shifting resolution and stability over a wide temperature range, incorporating a differential quadrature hybrid splitter, phase-inverting variable attenuators, and a differential power combiner, fabricated on a single CMOS die, with control voltages and bias circuits to maintain performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive phase shifters (reflective-type or cascade of attenuators) are used, then phase shifting function is achieved, but gain variations over frequency and temperature increase, and stability deteriorates
Solution Approach 1:
The patent employs a reflective-type phase shifter configuration where reflective loads are used to achieve phase shifting through inversion principles. The hybrid quadrature with reflective loads creates phase shifts by reflecting signals back through the network, utilizing the inversion property of the reflection path to achieve the desired phase control while maintaining stability over temperature and frequency variations.
2Measurement precision
If cascade of attenuators is used for phase shifting, then phase resolution can be achieved, but insertion loss and device size increase as resolution increases
Solution Approach 1:
The patent uses a reflective-type phase shifter that achieves phase shifting through signal reflection and inversion rather than through cascaded attenuation. This approach provides fine phase resolution without the cumulative insertion loss that would result from multiple attenuator stages, as the reflective configuration reuses the same signal path multiple times with different phase contributions.
3Reliability
If large number of radiating elements and phase shifters are used to achieve sufficient EIRP and Gain, then communication performance is improved, but power consumption increases
Solution Approach 1:
The patent employs passive phase shifters that do not require external power supply for their operation. The reflective-type phase shifters and hybrid quadrature networks operate using the incoming signal energy itself, without requiring additional active components that would consume power. This self-service approach allows the phased array to achieve the required EIRP and Gain performance through passive signal manipulation rather than active amplification at each element.
Data Source
AI summary
A radiation pattern of a phased array antenna, comprising a plurality of antenna elements, may be dynamically modified using phase shifters to apply variable phase shifts between antenna elements. In a phased array antenna designed for airborne applications, the phase shifters may be required to enable a fine phase-shifting resolution and to operate over a wide temperature range. The phase shifters may also be required to perform while exhibiting small process variations, small form factor, low power consumption, and low loss. One possible solution to this is a passive vector-interpolating phase shifter configured to exhibit such characteristics.