RF Front-End Impedance Matching With Switchable Signal Attenuation
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Solution Overview
Problem
Current RF front-end low-noise amplifiers (LNAs) face challenges in achieving high linearity and ultra-low noise figure with varying frequency bands, requiring complex circuit designs and additional components, which increase chip size and power consumption, while existing attenuation methods either increase noise figure or fail to improve linearity across different frequency bands.
Innovation Solution
A circuitry and method utilizing switchable capacitive and resistive elements to dynamically match impedance and attenuate signals, converting high ohmic impedances to low ohmic impedances, allowing for efficient impedance matching and signal attenuation in a 50 Ohm environment, thereby enhancing linearity and noise figure performance across multiple frequency bands without increasing chip size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pre-attenuator is placed before the matching inductor to reduce gain and improve linearity, then linearity performance is improved, but noise figure increases due to additional loss before the LNA circuit
Solution Approach 1:
The patent introduces an impedance transformation network as an intermediary component between the pre-attenuator and the LNA. This network transforms the high output impedance of the matching inductor to a low input impedance for the pre-attenuator, enabling the pre-attenuator to operate effectively without being positioned directly in the 50 Ohm environment, thus reducing its negative impact on noise figure while maintaining linearity improvement
Solution Approach 2:
The patent changes the impedance parameter of the signal path by introducing the impedance transformation network. It transforms the impedance from high (matching inductor output) to low (pre-attenuator input), creating optimal operating conditions for the pre-attenuator and reducing signal loss, thereby improving the noise figure while maintaining linearity performance
2Reliability
If a pre-attenuator is placed after the matching inductor to reduce gain and improve linearity, then linearity performance is improved, but additional external pins are required increasing chip size
Solution Approach 1:
The patent merges the impedance transformation function with the existing matching inductor circuitry. The impedance transformation network is integrated into the signal path between the matching inductor and the LNA, combining multiple functions (impedance transformation and signal routing) into a unified structure, thereby achieving linearity improvement without requiring additional external pins or increasing chip size
Solution Approach 2:
The impedance transformation network serves multiple functions simultaneously: it transforms impedance, routes the signal from the matching inductor to the pre-attenuator, and maintains compatibility with the existing LNA input requirements. This multi-functionality eliminates the need for separate dedicated components and external pins, reducing chip size while improving linearity
3Adaptability or versatility
If multiple frequency bands are supported with different matching elements, then frequency versatility is improved, but device complexity increases
Solution Approach 1:
The patent introduces dynamically switchable impedance transformation networks that can be reconfigured for different frequency bands. The switchable elements (such as MOS transistors or PIN diodes) allow the circuit to adapt its impedance characteristics dynamically, enabling a single LNA core to support multiple frequency bands without requiring separate dedicated matching circuits for each band, thus reducing overall device complexity
Data Source
Figure 1~2
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Figure 3b
AI summary
Embodiments according to the disclosure comprise a circuitry for a radio frequency front end, RFFE, the circuitry comprising a signal input to be coupled to an inductive matching element (360) of the RFFE, the inductive matching element having a high ohmic output impedance for a radio frequency, rf, signal, a signal output to be coupled to an input of an amplifier (370) of the RFFE, the input of the amplifier having a high ohmic input impedance for the rf signal, a reference output to be coupled to a reference potential, a first switchable element (340), being a capacitive element coupled between the signal input and the signal output when the circuitry is in a first operating mode and a second switchable element (350), being a resistive element coupled between the signal output and the reference output when the circuitry is in the first operating mode