Integrated LNA Filter Stages for Interference Blocking Control
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Solution Overview
Problem
Current amplifiers, particularly low noise amplifiers (LNAs), face challenges in effectively handling large interfering signals which can degrade receiver performance by causing intermodulation distortion and 'blocking', and existing solutions either attenuate desired signals or complicate mixer design with high linearity requirements.
Innovation Solution
An LNA with integrated filter stages, including gain, filter, and buffer stages, utilizing inductor-capacitor resonator tanks and shunt capacitors to provide selective signal amplification and attenuation of interfering signals, thereby improving noise performance and handling large interfering signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional amplifier designs are used, then the amplifier can provide signal amplification, but it cannot effectively handle large interfering signals causing intermodulation distortion and blocking
Solution Approach 1:
The amplifier is divided into multiple stages: a first amplification stage, a filtering stage, and a second amplification stage. This segmentation allows the filtering stage to remove interfering signals between amplification stages, preventing intermodulation distortion and blocking while maintaining signal amplification capability.
Solution Approach 2:
The filtering stage performs preliminary action by attenuating interfering signals before they reach the second amplification stage. This prevents the interfering signals from causing intermodulation distortion and blocking in subsequent stages, addressing the harmful effects before they manifest.
2Object-generated harmful factors
If filtering is added to attenuate interfering signals, then interfering signal attenuation is improved, but the device complexity increases
Solution Approach 1:
The filtering function is merged into the amplifier structure by integrating a filtering stage between two amplification stages. This combination achieves interfering signal attenuation without requiring a completely separate filtering system, thereby limiting the increase in 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
The LNA with integrated filter effectively attenuates interfering signals, enhancing receiver performance by maintaining desired signal integrity and reducing the impact of intermodulation distortion, while simplifying design complexities associated with high linearity requirements.
Implementation Method 1
Each filter stage may include an inductor and a capacitor, which may be coupled in parallel to form a resonator tank. This tank may pass a desired signal and attenuate the interfering signals.
Implementation Method 2
Each filter stage may further include a shunt capacitor coupled to one end (or each end) of the inductor to form a low impedance path at high frequencies.
Data Source
AI summary
An amplifier with integrated filter (e.g., an LNA) is described. In one design, the amplifier may include a gain stage, a filter stage, and a buffer stage. The gain stage may provide signal amplification for an input signal. The filter stage may provide filtering for the input signal. The buffer stage may buffer a filtered signal from the filter stage. The amplifier may further include a second filter stage and a second buffer stage. The second filter stage may provide additional filtering for the input signal. The second buffer stage may buffer a second filtered signal from the second filter stage. All of the stages may be stacked and coupled between a supply voltage and circuit ground. The filter stage(s) may implement an elliptical lowpass filter. Each filter stage may include an inductor and a capacitor coupled in parallel and forming a resonator tank to attenuate interfering signals.