Receiver Amplifier Feedback Tuning for Wideband Impedance Matching
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Solution Overview
Problem
Designing radio receiver amplifiers, such as low-noise amplifiers (LNAs), to achieve wideband 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 mismatch between maximum gain and input impedance matching.
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 input 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 mismatch between maximum gain and input impedance matching
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 feedback impedance that provides feedback signal to the input node. This feedback mechanism compensates for the phase changes around resonance frequency, enabling simultaneous optimization of frequency selectivity and input impedance matching.
Solution Approach 2:
The patent uses parameter changes by incorporating a tunable capacitor in the feedback circuit path that can be adjusted to change the feedback impedance. By tuning the capacitance value, the system can optimize the balance between frequency selectivity and input impedance matching for different operating conditions, resolving the contradiction between these two parameters.
2Adaptability or versatility
If wideband input impedance matching is achieved, then adaptability is improved, but manufacturing complexity increases due to requirement for high Q value components
Solution Approach 1:
The patent employs low Q value capacitors in the feedback circuit path instead of requiring high Q value components. These low Q value capacitors are easier and cheaper to manufacture while still achieving the desired wideband input impedance matching when used in conjunction with the feedback mechanism. The feedback network compensates for the lower Q value, maintaining performance while reducing manufacturing complexity.
3Power
If maximum gain is optimized, then power is improved, but input impedance matching deteriorates at different frequencies
Solution Approach 1:
The patent applies dynamics by making the feedback impedance tunable through the variable capacitor in the feedback circuit path. This allows the system to dynamically adjust the feedback amount and phase to simultaneously optimize both gain and input impedance matching for different operating frequencies, resolving the frequency-dependent mismatch problem.
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 effective wideband input impedance matching and high performance with cost-effective and compact components, particularly beneficial for high-bandwidth applications like 5G systems.
Implementation Method 1
a tunable tank circuit, such as an LC circuit, connected to an output node of the amplifier. Such a tank circuit can provide a desired degree of frequency selectivity
Implementation Method 2
a feedback network between the output node and an input node
Data Source
AI summary
An amplifier for a receiver circuit is disclosed. The amplifier has an input node (Vin) and an output node (Vout). It comprises a tunable tank circuit connected to the output node (Vout), a feedback circuit path connected between the output node (Vout) and the input node (Vin), and a tunable capacitor connected between an internal node of the feedback circuit path and a reference-voltage node. A receiver circuit and a communication apparatus is disclosed as well.