Compact RF Delay Lines for Wideband Phased-Array Resolution
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Solution Overview
Problem
Conventional RF delay lines face challenges in achieving fine resolution and wideband performance due to parasitic effects and loss, limiting their applicability in phased-array radar and beam steering applications.
Innovation Solution
A phased array system comprising a combination of active and passive delay elements, where active delay elements provide coarse phase shifts and a T-line based fine delay line, enabling lower area and power consumption, and multiple staggered phase shifter stages for process invariant wideband performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple switches are used to change capacitance and inductance values to improve resolution, then the resolution is improved, but the minimum size is limited due to parasitic effects and loss
Solution Approach 1:
The delay line is divided into multiple discrete unit elements, each contributing a small phase shift. By cascading many such units, the total delay resolution is improved without requiring individual components to be excessively small, thereby reducing parasitic effects in each element.
Solution Approach 2:
The patent transitions from discrete lumped-element switches to a distributed transmission line structure where delay is achieved through spatial distribution of phase shifts along the line, effectively moving from a discrete component approach to a continuous distributed approach that reduces parasitic limitations.
2Measurement precision
If transmission line with tunable elements is used, then the delay resolution can be achieved, but the dimension becomes comparable to the wavelength of the waveform
Solution Approach 1:
The patent changes the operating parameters by using lumped LC elements tuned to provide specific phase shifts at the operating frequency, rather than relying on physical transmission line lengths comparable to wavelength. This allows achieving the same electrical length with physically smaller components.
Solution Approach 2:
The patent replaces the mechanical/geometric approach of using physical transmission line lengths (mechanical dimension) with an electrical approach using tuned LC resonators that provide equivalent electrical delay through resonance effects, thereby reducing physical footprint.
3Area of moving object
If discrete transistors or integrated circuits are used, then the size is reduced, but the bandwidth performance becomes challenging
Solution Approach 1:
The patent employs dynamically tunable LC elements that can adjust their resonant frequency and phase shift characteristics. This dynamic capability allows the compact discrete circuit implementation to maintain wideband performance by adapting to different operating conditions and frequencies.
Solution Approach 2:
The patent uses composite structures combining discrete transistors with tuned LC circuits and transmission line sections. This hybrid composite approach integrates the size advantages of discrete circuits with the wideband characteristics of transmission line structures, achieving both compactness and wideband performance.
Data Source
Figure 1~1B
Figure 2
Figure 3A~3B
AI summary
A phased array system includes tunable delay elements having active delay element(s) and passive delay element(s). A second resolution by the passive delay element is smaller than a first resolution by the active delay element, and the resolution corresponds to delay applied to an input signal and has discrete steps for phase over which the delay element can be operated. For multiple sets of tunable delay elements, a calibration process sets, for one set of the delay elements, all but an n-th active delay element and the passive delay element to a first phase, and the n-th active delay element to a second phase. In a second set of the delay elements, all of the active delay elements are set to the first phase and the passive delay element is set to the second phase. A phase difference is detected and adjusted to meet a criterion between the two sets.