RF Circuit Layout for LNA-Output Band-Stop Filtering
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Solution Overview
Problem
The existing radio frequency modules suffer from a decrease in signal-to-noise ratio and reception sensitivity due to band stop filters attenuating weak received signals in a specific frequency band, leading to signal distortion and reduced sensitivity.
Innovation Solution
A radio frequency circuit design that includes a first filter with a passband for a first band, a power amplifier, a second filter with a passband for a second band, a low-noise amplifier, and a band stop filter connected to the output end of the low-noise amplifier with a stopband for the first band, which reduces signal leakage and distortion by positioning the band stop filter on the output side of the low-noise amplifier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a band stop filter is disposed on the input side of the low-noise amplifier to remove noise components, then noise removal is improved, but the received signal is attenuated causing deterioration of reception sensitivity
Solution Approach 1:
The band stop filter is disposed on the output side of the low-noise amplifier to perform noise filtering after the signal has been amplified. This preliminary action of amplification before filtering ensures that the weak received signal is strengthened first, then noise is removed, avoiding the attenuation problem that would occur if filtering were performed before amplification.
Solution Approach 2:
Instead of the conventional approach of placing the band stop filter on the input side of the low-noise amplifier, the invention inverts the order by placing it on the output side. This inversion allows the low-noise amplifier to first amplify the weak received signal before the band stop filter removes noise components, thereby maintaining reception sensitivity while still achieving noise removal.
2Object-affected harmful factors
If a band stop filter is used to remove noise in a predetermined frequency band, then noise removal is improved, but the signal-to-noise ratio of the received signal decreases
Solution Approach 1:
The low-noise amplifier performs signal amplification before the band stop filter removes noise components. This preliminary amplification increases the signal level so that when the filter removes noise, the signal-to-noise ratio is maintained or improved rather than degraded.
Solution Approach 2:
The invention inverts the conventional order of operations by placing the low-noise amplifier before the band stop filter in the signal path. This inversion ensures that signal amplification occurs before noise filtering, preventing the degradation of signal-to-noise ratio that would occur if noise filtering were performed on the weak signal before amplification.
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
This configuration effectively reduces signal distortion and maintains high signal-to-noise ratio and reception sensitivity by minimizing signal leakage from transmission signals into reception paths, thereby enhancing the overall performance of the radio frequency circuit.
Implementation Method 1
a band stop filter connected to an output end of the low-noise amplifier, and having a stopband that includes at least a portion of the first band
Data Source
AI summary
A radio frequency circuit is configured to simultaneously transfer a signal in a first band and a signal in a second band different from the first band, and includes: a first filter having a passband that includes at least a portion of the first band; a first power amplifier connected to the first filter; a second filter having a passband that includes at least a portion of the second band; a first low-noise amplifier connected to the second filter; and a first band stop filter connected to an output end of the first low-noise amplifier, and having a stopband that includes at least a portion of the first band.