Digital Step Attenuator Bypass Circuit for RF Phase Coherence
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Digital step attenuators (DSAs) in RF communications systems, particularly in 5G massive MIMO systems, introduce undesirable phase shifts in attenuated signals, which is challenging due to the large number of signal paths and affects the system's performance.
Innovation Solution
A digital step attenuator design incorporating a bypass switching circuit with series-connected bypass transistors and a bypass shunt transistor, along with a shunt switching circuit, is used to minimize phase shift by matching parasitic capacitance between bypass and attenuation modes, allowing for digital control of attenuation levels and maintaining phase coherence across a wide frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a digital step attenuator is used to attenuate RF signals, then attenuation levels can be digitally controlled, but phase shift is introduced on the attenuated signals
Solution Approach 1:
The bypass switching circuit is segmented into multiple transistors (first bypass transistor, second bypass transistor, and bypass shunt transistor) that can be independently controlled. This segmentation allows the circuit to operate in different modes (bypass mode and attenuation mode) by selectively activating specific transistor combinations, thereby enabling digital control of attenuation while managing phase shift effects.
Solution Approach 2:
The circuit changes its electrical parameters by switching between different transistor states. In bypass mode, the bypass transistors are activated to provide a low-impedance path that minimizes phase shift. In attenuation mode, the attenuator circuit is activated to provide signal attenuation. This parameter switching allows the system to achieve both digital attenuation control and phase shift management.
2Object-affected harmful factors
If bypass switching circuit is added to reduce phase shift, then phase coherence is improved, but device complexity increases
Solution Approach 1:
The bypass switching circuit is merged with the existing attenuator circuit to form an integrated digital step attenuator. The bypass transistors are positioned in parallel with the attenuator elements, allowing the same physical structure to serve dual functions: signal attenuation when bypass transistors are off, and phase-coherent signal passing when bypass transistors are on. This merging reduces the need for separate phase compensation circuits.
Solution Approach 2:
The bypass switching circuit serves multiple functions: it provides a low-impedance bypass path to minimize phase shift, enables digital control of attenuation levels, and maintains phase coherence across different attenuation settings. By making the circuit multi-functional, the patent reduces overall system complexity while achieving phase shift reduction.
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 effectively reduces phase shift variability across frequencies, ensuring strong phase coherence and accurate attenuation in RF systems, enhancing the performance of 5G massive MIMO systems by minimizing phase errors.
Implementation Method 1
The bypass shunt transistor is configured such that a parasitic capacitance of the bypass shunt transistor is matched between a bypass mode and an attenuation mode
Data Source
AI summary
Embodiments of a digital step attenuator are disclosed. In an embodiment, a digital step attenuator includes a radio frequency (RF) input, an RF output, an attenuation circuit connected between the RF input and the RF output, a shunt switching circuit connected to the attenuator circuit, and a bypass switching circuit connected between the RF input and the RF output. The bypass switching circuit includes a first bypass transistor, and a second bypass transistor, wherein the first bypass transistor and the second bypass transistor are series connected to each other between the RF input and the RF output, and a bypass shunt transistor connected between the first bypass transistor and the second bypass transistor.