Silicon Shielding Structure for Wider-Band RF Amplifier Grounding
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Solution Overview
Problem
Conventional high-power RF transistor devices face limitations in instantaneous signal bandwidth due to low frequency resonance caused by interactions between bias feeds and baseband decoupling circuit components, leading to restricted RF bandwidth amplifiers with limited applications.
Innovation Solution
The implementation of a current path structure that circumscribes low-Q material, eliminating power losses by positioning the reverse current path structure between the envelope capacitance and the forward current path, and using low temperature co-fired ceramic structures with RF shielding to enhance performance and reduce eddy currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If baseband decoupling circuit components are used to provide RF ground down to envelope frequencies, then RF grounding performance is improved, but low frequency resonance occurs due to interaction with bias feeds, limiting instantaneous signal bandwidth
Solution Approach 1:
The patent extracts the problematic low-Q material (dielectric material with high loss tangent) from the signal path by positioning the reverse current path structure between the envelope capacitance and forward current path. This removes the source of low frequency resonance while maintaining RF grounding performance through the shielded configuration.
Solution Approach 2:
The patent introduces a reverse current path structure as an intermediary element that carries return current through a dedicated path rather than through the low-Q dielectric material. This mediator prevents the harmful interaction between bias feeds and baseband decoupling circuit while maintaining circuit functionality.
2Ease of manufacture
If low-Q dielectric material is used for baseband decoupling circuit, then manufacturing ease is improved, but power losses occur due to eddy currents, reducing RF efficiency
Solution Approach 1:
The patent removes low-Q dielectric material from between the forward and reverse current paths by implementing a reverse current path structure that bypasses this lossy region. This extraction eliminates eddy current losses while maintaining the ease of manufacturing the baseband decoupling circuit.
Solution Approach 2:
The patent segments the current paths into separate forward and reverse paths, with the reverse current path positioned to avoid the low-Q dielectric material. This segmentation isolates the high-frequency RF current paths from the lossy material while allowing the baseband decoupling circuit to remain integrated.
3Productivity
If wider RF bandwidth is achieved by reducing low frequency resonance, then instantaneous signal bandwidth is improved, but device complexity increases due to additional shielding structures
Solution Approach 1:
The patent combines multiple functions into the reverse current path structure: it provides RF shielding, carries return current, and defines the boundary for baseband decoupling circuit operation. This merging achieves wider instantaneous signal bandwidth while minimizing additional device complexity by using a multi-functional structure.
Solution Approach 2:
The reverse current path structure serves multiple purposes: it acts as an RF shield, provides a dedicated return current path, and enables baseband decoupling circuit functionality. This universal structure achieves bandwidth expansion without proportionally increasing device complexity.
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
This configuration enables wider RF bandwidth amplifiers with increased low frequency resonance, supporting transmission of signals with ISBW of 200 MHz or above and LFR of 600 MHz or greater, while minimizing power losses and enhancing RF shielding efficiency.
Implementation Method 1
eliminating power losses by positioning the reverse current path structure between the envelope capacitance and the forward current path, and using low temperature co-fired ceramic structures with RF shielding to enhance performance and reduce eddy currents
Implementation Method 2
using low temperature co-fired ceramic structures with RF shielding to enhance performance and reduce eddy currents
Data Source
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AI summary
An RF amplifier device includes a semiconductor die and an integrated passive device (IPD) on a ground flange. The IPD includes a semiconductor substrate and a metal-insulator-metal (MIM) capacitor coupled to the semiconductor substrate. The MIM capacitor includes a first electrode, a second electrode, and a dielectric between the first electrode and the second electrode. A first RF capacitor is over the semiconductor substrate and a second RF capacitor is over the semiconductor substrate. A metal layer is patterned to form a portion of an elevated metal shielding structure, a first plate of the first RF capacitor and a first plate of the second RF capacitor. The elevated metal shielding structure is over the MIM capacitor. The IPD is electrically coupled to the semiconductor die.