Common-Gate LNA With Resonant Band-Stop Filtering
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Solution Overview
Problem
Wideband RF receiver design faces challenges with increasing adjacent channel interference due to broad spectrum allocation, leading to unreliable signal reception and increased requirements for external RF filters.
Innovation Solution
Integration of a resonant cavity filter circuit within a low-noise amplifier circuit using MOS transistors in a common gate or cascode configuration, which acts as a band-stop filter to attenuate interfering signals, reducing the need for external filters and improving receiver robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an external RF filter is added at the front end of a receiver, then out-of-band interfering signals are suppressed, but device complexity and cost increase
Solution Approach 1:
The patent integrates the band-stop filter function directly into the low-noise amplifier circuit by coupling a resonant cavity filter to the gate of the MOS transistor. This merging of filtering and amplification functions into a single integrated circuit eliminates the need for separate external RF filters, thereby reducing device complexity and cost while maintaining signal reception reliability
Solution Approach 2:
The low-noise amplifier circuit is designed to perform multiple functions: signal amplification and band-stop filtering. By making the LNA circuit multi-functional, the patent eliminates the need for separate dedicated filter components, reducing overall receiver complexity while maintaining the ability to suppress out-of-band interfering signals
2Adaptability or versatility
If the receive band becomes wider, then more spectrum is utilized, but adjacent channel interference increases
Solution Approach 1:
The patent applies local quality by implementing a band-stop filter with specific resonant frequencies targeted at particular interference bands while maintaining broadband amplification characteristics. The resonant cavity filter is tuned to specific frequencies (e.g., GSM transmitter frequencies) to provide localized filtering action at interference frequencies without affecting the broader receive band, thus allowing wide spectrum utilization while suppressing specific adjacent channel interference
3Reliability
If a resonant cavity filter is integrated into the LNA circuit, then interfering signals are attenuated, but circuit complexity increases
Solution Approach 1:
The resonant cavity filter is coupled to the gate of the MOS transistor in the common-gate amplifier configuration, merging the filtering function with the amplification circuit. This integration approach achieves interference rejection within the amplifier circuit itself without requiring separate filter stages, thereby limiting the increase in overall circuit complexity while maintaining reliable interference attenuation
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 low-noise amplifier circuit effectively rejects interfering signals, achieving over 20 dB extra rejection in specific frequency bands, reducing external filter requirements and enhancing receiver stability and cost-effectiveness.
Implementation Method 1
a resonant cavity filter circuit coupled to the gate of the MOS transistor
Data Source
AI summary
A low-noise amplifier circuit includes a MOS transistor in a common gate amplifier configuration. A single-ended input is at a source of the MOS transistor. A resonant cavity filter circuit is coupled to a gate of the MOS transistor.