Diplexer RF Filter Paths for Piezoelectric Spur and Loss Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Piezoelectric filters produce undesirable spurious responses and inherent bulk losses, leading to significant amplitude fluctuations and increased insertion losses within passbands, which degrade signal quality.
Innovation Solution
A radio frequency circuit design incorporating two filter paths, one with a piezoelectric filter between two filters of the same type (low pass or high pass) and another path with filters of the opposite type, where spurious modes are filtered out by these filters, allowing unaffected RF signals to bypass through the other path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a piezoelectric filter is used to provide precise rejection capabilities and high selectivity, then the notch sharpness and frequency isolation are improved, but spurious responses and bulk losses increase causing amplitude fluctuations and insertion losses in passbands
Solution Approach 1:
The filter system is divided into multiple independent filter paths (first filter path with piezoelectric filter and second filter path with alternative filters). Each path handles specific frequency components, allowing the piezoelectric filter to provide sharp notch rejection while alternative paths compensate for spurious responses and maintain passband signal quality.
Solution Approach 2:
Alternative filters are introduced as intermediary components that process signals bypassing the piezoelectric filter when spurious responses occur. These alternative filters act as mediators to eliminate unwanted spurious modes while preserving the desired sharp notch characteristics provided by the piezoelectric filter.
2Measurement precision
If a piezoelectric filter is used to achieve high selectivity, then frequency isolation is improved, but insertion losses increase due to bulk losses
Solution Approach 1:
The signal path is segmented into multiple filter paths, allowing traffic to be routed through the piezoelectric filter for frequencies requiring sharp rejection while routing other frequencies through alternative filters with lower insertion losses, thereby maintaining high frequency isolation without excessive energy loss.
Solution Approach 2:
The system dynamically changes operational parameters by selecting different filter paths based on frequency content. The alternative filters provide a parameter alternative with different loss characteristics, allowing optimization of insertion loss while maintaining the frequency isolation benefits of the piezoelectric filter when needed.
3Measurement precision
If a piezoelectric filter is used to provide precise rejection, then notch attenuation is improved, but spurious responses cause amplitude fluctuations in passbands
Solution Approach 1:
Spurious responses generated by the piezoelectric filter are extracted and removed through alternative filter paths. The alternative filters are specifically designed to eliminate these unwanted spurious modes while preserving the main signal, effectively separating the harmful spurious responses from the desired filtered signal.
Solution Approach 2:
The spurious responses, which are harmful by nature, are converted into a design consideration that drives the creation of alternative filter paths. These alternative paths use the spurious response frequencies as their filtering target, transforming the harmful effect into a useful rejection feature while maintaining the benefits of the piezoelectric filter's sharp notch.
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 effectively filters out spurious modes while maintaining minimal signal loss, ensuring high selectivity and low insertion losses, thereby enhancing signal quality and performance.
Implementation Method 1
Utilizing the piezoelectric effect, piezoelectric filters can precisely manipulate piezoelectric waves to achieve high selectivity and low insertion losses
Implementation Method 2
They can produce undesirable spurious responses and inherent bulk losses, particularly around the resonant frequencies
Data Source
AI summary
Radio frequency (RF) circuits and method of operating the same are disclosed. In some embodiments, the RF circuit includes an input terminal and an output terminal. A first filter path is connected between the input terminal and the output terminal the first filter path including an piezoelectric filter, a first filter and a second filter, wherein the piezoelectric filter is connected between the first filter and the second filter. The second filter path is connected between the input terminal and the output filter, wherein the second filter path includes a third filter and a fourth filter, wherein both the third filter and the fourth filter are of a second type of filter. The first type of filter is one of either a low pass a high pass type filter. The second type of filter is of another one of the low pass the high pass type filter.