Low-Noise Amplifier Using Elastic Wave Resonator Noise Filtering
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Solution Overview
Problem
Low-noise amplifiers face challenges in effectively suppressing noise in input signals due to the wide passband of LC resonant circuits, which amplifies noise along with weak reception signals, leading to poor signal-to-noise ratio.
Innovation Solution
Incorporating an elastic wave resonator with a narrower resonant frequency band, connected to a field effect transistor and matching lines, to suppress noise in the low-noise amplifier, with variable-capacitance devices tuning the resonant frequencies and anti-resonant frequencies to control signal passage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If an LC resonant circuit is used in the low-noise amplifier, then the stability of the amplifier is improved, but the noise suppression capability deteriorates due to the wide passband
Solution Approach 1:
The patent changes the resonant circuit parameters by replacing the LC resonant circuit with an elastic wave resonator, which has fundamentally different resonant characteristics. The elastic wave resonator provides a narrow passband with high Q-value, contrasting with the wide passband of LC resonant circuits, thereby achieving effective noise suppression while maintaining amplifier stability
Solution Approach 2:
The patent substitutes the electromagnetic LC resonant circuit system with an elastic wave resonator system that utilizes mechanical vibrations. This substitution enables narrowband filtering through mechanical resonance, effectively suppressing noise while maintaining the required amplifier stability
2Power
If the gain of the low-noise amplifier is set to a large value to amplify weak reception signals, then the signal amplification capability is improved, but the noise amplification worsens
Solution Approach 1:
The patent applies preliminary noise suppression by placing the elastic wave resonator in the signal path before the amplification stage. The resonator pre-filters the input signal, attenuating noise components before they enter the high-gain amplifier, thereby preventing noise amplification while preserving signal amplification capability
Solution Approach 2:
The elastic wave resonator serves as an intermediary element between the antenna input and the amplifier stage. It acts as a selective filter that mediates the signal path, allowing desired reception signals to pass while blocking noise frequencies, thus enabling high gain operation without proportional noise amplification
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 elastic wave resonator effectively narrows the passband, reducing noise amplification and improving the signal-to-noise ratio by attenuating voltage noise and intermodulation distortion, while being integrated with CMOS circuits for compact and cost-effective RFICs.
Implementation Method 1
the branch circuit is connected to an elastic wave resonator
Implementation Method 2
An elastic wave resonator can have a support substrate 315, a high-acoustic-velocity film 314, a low-acoustic-velocity film 313, a piezoelectric film 312, and an interdigital transducer (IDT) electrode 311
Implementation Method 3
a piezoelectric film 312 stacked on the low-acoustic-velocity film 313
Data Source
AI summary
Provided is a low-noise amplifier that can effectively suppress noise included in an input signal. A low-noise amplifier according to an embodiment of the present invention amplifies a reception signal in a predetermined frequency band from an antenna. The low-noise amplifier includes an input terminal, an output terminal, a field effect transistor, and a branch circuit. The branch circuit is branched from a circuit connecting the input terminal or the output terminal to the field effect transistor. The branch circuit is connected to the elastic wave resonator.