Acoustic Wave Filter Layout for DC Blocking and RF Impedance Matching
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Solution Overview
Problem
Existing radio frequency front end circuits face impedance mismatching due to the inclusion of a DC blocking capacitor, leading to transmission loss and deterioration of the noise figure of low-noise amplifiers.
Innovation Solution
An acoustic wave filter design incorporating a first serial arm resonant device with the highest resonant frequency, connected closest to the input/output terminal, and a first inductor between the ground and a path connecting serial arm resonant devices, ensuring DC blocking and impedance matching in the pass band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a DC blocking capacitor is disposed in series to the input terminal of the low-noise amplifier, then DC bias current leakage is prevented, but impedance mismatching occurs in the radio frequency band leading to transmission loss and noise figure deterioration
Solution Approach 1:
The patent extracts and removes the DC blocking capacitor from the signal path by utilizing the DC blocking capability of the first serial arm resonant device instead. This eliminates the need for a separate capacitor component that would cause impedance mismatching, thereby preventing transmission loss while maintaining reliable DC bias current blocking.
Solution Approach 2:
The first serial arm resonant device is designed to serve multiple functions: it provides DC blocking capability while simultaneously maintaining proper impedance matching in the radio frequency pass band. This multi-functional approach replaces the need for separate DC blocking capacitor and impedance matching network, eliminating transmission loss.
2Reliability
If an inductor is connected between ground and the path connecting low-noise amplifier and bandpass filter for impedance matching, then impedance matching is achieved, but a DC blocking capacitor must be added in series which increases device complexity and causes transmission loss
Solution Approach 1:
The patent merges the DC blocking function and the impedance matching function into a single component - the first serial arm resonant device. This device simultaneously provides DC blocking capability and maintains proper impedance matching in the pass band, eliminating the need for separate capacitor and inductor components, thereby reducing device complexity and transmission loss.
Solution Approach 2:
The first serial arm resonant device is designed to perform multiple functions: DC blocking and impedance matching in the radio frequency band. This multi-functional design eliminates the need for additional components that would increase device complexity and cause transmission loss.
3Reliability
If a DC blocking capacitor is disposed in series to the input terminal, then DC bias current leakage is prevented, but the noise figure of the low-noise amplifier is deteriorated
Solution Approach 1:
The patent extracts and removes the DC blocking capacitor from the signal path by utilizing the DC blocking capability of the first serial arm resonant device instead. This eliminates the source of noise figure deterioration while maintaining reliable DC bias current blocking.
Solution Approach 2:
The first serial arm resonant device acts as an intermediary component that provides DC blocking capability without introducing the impedance mismatching and noise figure deterioration associated with conventional capacitors. It mediates between the DC bias current blocking requirement and the noise figure performance requirement.
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
The design ensures effective DC blocking and impedance matching, reducing transmission loss and maintaining a low noise figure in the radio frequency module.
Implementation Method 1
the first serial arm resonant device has a highest resonant frequency among the plurality of serial arm resonant devices
Implementation Method 2
Each of the plurality of acoustic wave resonators includes an interdigital electrode and a piezoelectric substrate
Data Source
AI summary
An acoustic wave filter includes: a plurality of serial arm resonant devices including serial arm resonators disposed on a serial arm path connecting input/output terminals; one or more parallel arm resonant devices including a parallel arm resonator connected between the serial arm path and the ground; an inductor connected between the ground and a first path connecting the serial arm resonators. The serial arm resonator is connected closest to the input/output terminal among the plurality of serial arm resonant devices, the one or more parallel arm resonant devices, and the inductor, and the serial arm resonator has the highest resonant frequency among the plurality of serial arm resonant devices.