Receiver Amplifier Feedback Tuning for Wideband Impedance Matching
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Solution Overview
Problem
Designing radio receiver amplifiers that achieve wideband input impedance matching while maintaining high performance and frequency selectivity is challenging, especially in systems like 4G and 5G cellular communications, where the signal bandwidth is large and the phase of the output voltage changes abruptly around the resonance frequency, making it difficult to match impedance and gain at the same frequency.
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 input impedance matching and gain 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
1Adaptability or versatility
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 making input impedance matching difficult
Solution Approach 1:
The patent introduces a feedback network that samples the output voltage and feeds it back to the input node. This feedback mechanism compensates for the abrupt phase changes around the resonance frequency by adjusting the feedback signal's phase and amplitude, thereby maintaining stable input impedance matching despite the tank circuit's phase variations.
Solution Approach 2:
The patent employs tunable components (variable capacitor and variable inductor) within the feedback network that allow dynamic adjustment of circuit parameters. By changing these parameters, the feedback network can adapt to compensate for phase shifts and maintain optimal input impedance matching across different operating conditions and frequencies.
2Reliability
If tuning is added to align maximum gain and best input impedance matching frequencies, then performance is improved, but device complexity increases
Solution Approach 1:
The feedback network serves multiple functions simultaneously: it provides input impedance matching, compensates for phase shifts, and enables tuning to align gain and matching frequencies. By integrating these functions into a single network rather than separate circuits, the patent achieves the desired performance alignment without proportionally increasing overall device complexity.
Solution Approach 2:
The patent uses tunable components that allow dynamic adjustment of the feedback network's characteristics. This enables the circuit to adapt its behavior to align maximum gain and best input impedance matching frequencies, providing reliability through可调参数 while keeping the tuning mechanism relatively simple by using variable capacitors and inductors rather than complex mechanical or digital tuning systems.
3Manufacturing precision
If high Q value components are used to achieve good impedance matching, then matching performance is improved, but manufacturing cost and difficulty increase
Solution Approach 1:
The patent deliberately uses components with relatively low Q values (easier and cheaper to manufacture) instead of high Q value components. The feedback network compensates for the lower component quality, achieving acceptable impedance matching performance through the feedback mechanism rather than relying on high-Q components, thereby reducing manufacturing cost and difficulty.
Solution Approach 2:
The feedback network acts as an intermediary that mediates between the low-Q value components and the desired high-performance impedance matching. By introducing this intermediate feedback path, the system can achieve good matching performance without requiring expensive, difficult-to-manufacture high-Q components, as the feedback compensates for the component limitations.
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 frequency selectivity and stability over a wide bandwidth, even with passive feedback circuits, using relatively inexpensive and smaller components.
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
Implementation Method 3
a tunable capacitor between an internal node of the feedback circuit path and a reference voltage node, such as ground or signal ground
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.