FET Resistive Mixer Isolation Using a Spiral Band-Stop Filter
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
FET resistive frequency mixers face challenges in achieving high RF-LO and IF-LO isolation, requiring complex RF matching circuits, which complicates the design and implementation of small and lightweight frequency mixers, especially in integrated circuit forms like MMICs.
Innovation Solution
Incorporating a small-sized band-stop filter between the drain of the FET and the RF/IF matching circuits to block or reflect local oscillation signals, enhancing isolation without adding internal or external complex circuits, and forming the band-stop filter in a spiral shape using a spurline for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a complex RF matching circuit is used to improve RF-LO isolation, then the isolation performance is improved, but the device size and complexity increase
Solution Approach 1:
The RF matching circuit is segmented into multiple functional sections: an input matching section, an isolation enhancement section containing the band-stop filter, and an output matching section. This segmentation allows each section to perform its specific function independently, improving RF-LO isolation without requiring a completely complex circuit redesign.
Solution Approach 2:
A band-stop filter is introduced as an intermediary element between the FET drain and the RF matching circuit. This intermediary component specifically targets and blocks the LO frequency signal, providing enhanced isolation without requiring the entire RF matching circuit to be overly complex. The band-stop filter acts as a mediator that selectively removes the harmful LO signal component.
2Reliability
If a larger RF matching circuit is used to improve RF-LO isolation, then the isolation performance is improved, but the device size increases
Solution Approach 1:
Instead of uniformly increasing the size of the entire RF matching circuit, the invention applies local quality enhancement by inserting a band-stop filter at the specific location where LO signal blocking is most effective. This localized approach improves isolation performance without proportionally increasing the overall device area, as only a specific portion of the circuit is enhanced.
Solution Approach 2:
The band-stop filter is implemented using a spiral-shaped spurline structure, which utilizes the planar dimension efficiently. By transforming a linear transmission line into a spiral configuration, the filter achieves the required electrical length and filtering performance within a compact area, effectively using dimensional transformation to reduce the footprint of the isolation enhancement circuit.
3Reliability
If a complex RF matching circuit is used to improve IF-LO isolation, then the isolation performance is improved, but the device complexity and size increase
Solution Approach 1:
The RF matching circuit is segmented into multiple functional sections: an input matching section, an isolation enhancement section containing the band-stop filter, and an output matching section. This segmentation allows each section to perform its specific function independently, improving RF-LO isolation without requiring a completely complex circuit redesign.
Solution Approach 2:
A band-stop filter is introduced as an intermediary element between the FET drain and the RF matching circuit. This intermediary component specifically targets and blocks the LO frequency signal, providing enhanced isolation without requiring the entire RF matching circuit to be overly complex. The band-stop filter acts as a mediator that selectively removes the harmful LO signal component.
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 solution significantly improves RF-LO and IF-LO isolation, allowing for more compact and efficient frequency mixing devices applicable to both hybrid and monolithic microwave integrated circuits, as demonstrated by simulation results showing enhanced isolation performance.
Implementation Method 1
a series resonance circuit providing a path from the drain of the FET to ground for the local oscillation signal
Implementation Method 2
a band-stop filter having a first terminal connected to the drain of the FET and a second terminal connected to the RF matching circuit or the IF matching circuit to reduce the local oscillation signal transferred to the second terminal of the band-stop filter
Data Source
AI summary
Provided is a FET resistive frequency mixing device having improved RF-LO and IF-LO isolations. The frequency mixing device includes: a field effect transistor (FET), a local oscillation matching circuit connected to a gate of the FET to transfer a local oscillation signal to the gate of the FET, a gate biasing circuit connected to the gate of the FET, a radio frequency (RF) matching circuit having a first terminal connected to a drain side of the FET and a second terminal serving as a RF terminal to receive or output a RF signal, an intermediate frequency (IF) matching circuit having a first terminal connected to the drain side of the FET and a second terminal serving as an IF terminal to receive or output an IF signal, and a series resonance circuit providing a path from the drain of the FET to ground for the local oscillation signal.