High-Frequency Module Impedance Mismatch for Reception Sensitivity
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Solution Overview
Problem
Existing high-frequency modules suffer from degradation of reception sensitivity due to amplified disturbing signals and gain reduction in circuits downstream of the low noise amplifier, leading to intermodulation distortion and harmonics, which degrades the overall reception sensitivity.
Innovation Solution
A high-frequency module configuration that includes a first filter with a specific pass band and attenuation band, a low noise amplifier, and an impedance matching circuit between the filter and the amplifier, which creates a gain mismatch to attenuate signal components in the attenuation band, thereby suppressing the degradation of reception sensitivity and noise figure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a phase shifter is disposed between a reception filter and a low noise amplifier to shift impedance and reduce disturbing signals, then the disturbing signals are reduced, but the amplified disturbing signals still cause distortion and gain reduction in downstream circuits, degrading reception sensitivity
Solution Approach 1:
The patent changes the impedance parameters of the low noise amplifier by disposing an impedance adjustment circuit between the reception filter and the low noise amplifier. This circuit adjusts the input impedance of the low noise amplifier to create a mismatch with the attenuation band impedance of the reception filter, thereby enhancing the attenuation effect on disturbing signals and preventing them from being amplified to cause distortion in downstream circuits.
2Object-affected harmful factors
If additional matching circuits are added downstream of the first filter and downstream of the low noise amplifier to attenuate signal components in the attenuation band, then the attenuation is improved, but the device complexity and noise figure degradation increase
Solution Approach 1:
The patent extracts the impedance adjustment function from separate matching circuits and integrates it into a single impedance adjustment circuit disposed between the reception filter and the low noise amplifier. This eliminates the need for additional matching circuits downstream, reducing device complexity while maintaining the attenuation effect on signal components in the attenuation band.
3Object-affected harmful factors
If additional matching circuits are added downstream of the first filter and downstream of the low noise amplifier to attenuate signal components in the attenuation band, then the attenuation is improved, but the noise figure of the high-frequency module degrades
Solution Approach 1:
The patent extracts the impedance adjustment function from separate matching circuits and integrates it into a single impedance adjustment circuit disposed between the reception filter and the low noise amplifier. This eliminates the need for additional matching circuits downstream, reducing device complexity while maintaining the attenuation effect on signal components in the attenuation band.
Data Source
AI summary
A high-frequency module (20) includes a reception-side filter (21) that uses a first frequency band as a pass band and a second frequency band as an attenuation band, an LNA (23), and a matching circuit (22) disposed between the reception-side filter (21) and the LNA (23). In a Smith chart, the matching circuit (22) makes an interval between impedance in the second frequency band of the reception-side filter (21) and a second gain circle center point indicating impedance at which gain in the second frequency band of the LNA (23) is maximized greater than an interval between impedance in the first frequency band of the reception-side filter (21) and a first gain circle center point indicating impedance at which gain in the first frequency band of the LNA (23) is maximized.