Switchable Low Pass Filter for Carrier Aggregation
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Solution Overview
Problem
Low pass filters used in mobile communication terminals for carrier aggregation experience unnecessary insertion loss when not implementing uplink/downlink carrier aggregation, which degrades communication quality due to intermodulation distortion.
Innovation Solution
A low pass filter design that includes switch elements and capacitance elements, allowing for adjustable cut-off frequencies based on the presence of intermodulation distortion signals, with switch elements connecting capacitance elements in parallel to attenuate distortion signals and reducing insertion loss when such signals are not present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a low pass filter is mounted to attenuate intermodulation distortion signals in carrier aggregation operations, then intermodulation distortion is reduced, but unnecessary insertion loss occurs in the transmission path when carrier aggregation is not implemented
Solution Approach 1:
The low pass filter is designed with a switchable capacitor that can be dynamically connected or disconnected based on carrier aggregation operation status. When carrier aggregation is active, the capacitor is connected to provide low pass filtering for intermodulation distortion attenuation. When carrier aggregation is inactive, the capacitor is disconnected to maintain a higher cut-off frequency and minimize insertion loss for normal RF signal transmission.
Solution Approach 2:
The cut-off frequency of the low pass filter is made variable through the switchable capacitor configuration. By changing the capacitance value in the filter circuit based on operational conditions, the cut-off frequency is adjusted to be lower during carrier aggregation operations (to attenuate intermodulation distortion) and higher during normal operations (to reduce insertion loss).
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 effectively reduces insertion loss in the low pass filter by adjusting cut-off frequencies in response to carrier aggregation operations, thereby improving communication quality by minimizing interference from intermodulation distortion.
Implementation Method 1
a first capacitance element whose one end is connected to a signal line for the low pass filter and whose other end is connected to ground of the low pass filter; and a second capacitance element whose one end is connected to the signal line and whose other end is connected to the ground via the first switch element
Data Source
AI summary
When a plurality of RF signals having different frequer bands are output at the same time by carrier aggregation, a switch element allows parallel connection between two capacitance elements such that a low pass filter has a first cut-off frequency that is lower than the frequency of an intermodulation distortion signal generated by the carrier aggregation. When an RF signal of a frequency band is output, the switch element releases parallel connection between the two capacitance elements such that the low pass filter has a second cut-off frequency that is higher than the first cut-off frequency.