Tunable Feedback LNA for Wideband Impedance Matching
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Solution Overview
Problem
Designing a low-noise amplifier (LNA) for wideband radio receiver circuits that achieves input impedance matching while maintaining high performance and frequency selectivity is challenging, especially when the phase of the output voltage changes abruptly around the resonance frequency, causing maximum gain and impedance matching to occur at different frequencies.
Innovation Solution
Incorporating a tunable tank circuit and a feedback network with a tunable capacitor connected between an internal node of the feedback circuit path and a reference voltage node, allowing for efficient tuning of the amplifier's gain and impedance matching across a wide frequency range using components with low Q value, which are easier and cheaper to manufacture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a tank circuit is used to provide frequency selectivity, then frequency selectivity is improved, but the phase of output voltage changes abruptly around resonance frequency causing maximum gain and impedance matching to occur at different frequencies
Solution Approach 1:
The patent applies feedback by connecting a feedback network between the output node and input node of the amplifier. The feedback network includes a feedback circuit path with a tunable capacitor connected between an internal node of the feedback circuit path and a reference voltage node. This feedback mechanism allows the system to adjust the phase relationship between input and output signals, enabling simultaneous optimization of both frequency selectivity and input impedance matching at the same frequency.
2Productivity
If wideband signal bandwidth is used for 4G and 5G communications, then communication capacity is improved, but achieving input impedance matching with enough frequency bandwidth becomes challenging
Solution Approach 1:
The patent employs dynamic tuning capabilities by incorporating a tunable capacitor in the feedback circuit path. This allows the amplifier to dynamically adjust its characteristics to maintain input impedance matching across wide frequency bands required for 4G and 5G communications. The tunable element enables the system to adapt to different operating conditions and frequency ranges.
3Power
If high gain is achieved in the amplifier, then signal amplification is improved, but input impedance matching performance deteriorates when phase changes abruptly around resonance frequency
Solution Approach 1:
The patent utilizes parameter changes by incorporating a tunable capacitor that can adjust the electrical characteristics of the feedback circuit. By changing the capacitance value, the system can optimize the phase relationship to simultaneously achieve high gain and good input impedance matching, resolving the conflict between these two performance parameters.
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 approach enables simultaneous tuning of maximum gain and input impedance matching to occur at the same frequency, achieving wideband input impedance matching with high performance and stability, even in high-bandwidth applications like 5G systems, using passive or active feedback circuits with tunable resistors and capacitors.
Implementation Method 1
The amplifier comprises a tunable tank circuit connected to an output node of the amplifier. Such a tank circuit can provide a desired degree of frequency selectivity.
Implementation Method 2
The amplifier comprises a feedback circuit path connected between the output node and the input node. Such a feedback network can facilitate in providing input impedance matching.
Data Source
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AI summary
An integrated circuit comprising an amplifier (30) for a receiver circuit (15) is disclosed. The amplifier has an input node (Vin) and an output node (Vout). It comprises a tunable tank circuit (100) connected to the output node (Vout), a feedback circuit path (200) connected between the output node (Vout) and the input node (Vin), and a tunable capacitor (210) connected between an internal node of the feedback circuit path (200) and a reference-voltage node. A communication apparatus is disclosed as well.