Band14 Suppression Circuit for AGPS Harmonic Interference
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Solution Overview
Problem
The interference between band14 signals and assisted GPS signals in smart terminal devices is not effectively eliminated by existing technologies, affecting the accuracy of positioning functions.
Innovation Solution
A band14 signal suppression circuit comprising a duplexer, an active low-pass filter, and a resonant filter is used to filter and suppress the second harmonic of the band14 signal, preventing interference with the assisted GPS signal. The resonant filter is an open line with specific dimensions and configuration, and an inductor is added to fine-tune the resonance, ensuring effective suppression without affecting the primary harmonic of the band14 signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a single filter is used to suppress band14 signal second harmonic, then the suppression level is insufficient, but adding multiple filters increases device complexity
Solution Approach 1:
The suppression circuit divides the filtering function into three separate components: a duplexer for initial frequency separation, an active low-pass filter for attenuating high-frequency components including the second harmonic, and a resonant filter specifically tuned to the band14 second harmonic frequency (1574 MHz) for targeted suppression. This segmentation allows each filter to perform its specialized function, achieving cumulative suppression of 83 dB while maintaining reasonable device complexity through modular design
Solution Approach 2:
Each filter in the suppression circuit is designed with specific local characteristics optimized for its function: the duplexer provides broad frequency separation, the active low-pass filter provides general high-frequency attenuation, and the resonant filter provides specialized narrowband suppression at 1574 MHz. This local quality approach ensures that each component contributes maximally to suppressing the band14 second harmonic interference while maintaining overall system performance
2Measurement precision
If the resonant filter is designed with precise dimensions for AGPS frequency, then filtering effectiveness is improved, but manufacturing precision requirements increase
Solution Approach 1:
The resonant filter's open line is designed with predetermined dimensions (length of 1/4 wavelength at 1574 MHz, width of 5 mils) that are calculated in advance to achieve the desired resonant frequency. By pre-calculating and pre-designing these dimensions, the patent ensures that the filter will provide effective suppression at the AGPS frequency while establishing clear manufacturing specifications that balance precision requirements with manufacturability
Solution Approach 2:
The resonant filter utilizes controlled impedance parameters (50 ohms characteristic impedance) and specific geometric parameters (line width, line spacing, number of turns) that are optimized to achieve the target resonant frequency. By carefully selecting and controlling these parameters, the patent achieves effective filtering at 1574 MHz while maintaining reasonable tolerances for mass production
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 suppression circuit significantly reduces the second harmonic of the band14 signal by 83 dB, eliminating interference with the assisted GPS signal and maintaining the normal functioning of the smart terminal device's positioning feature.
Implementation Method 1
The resonant filter is an open line, the open line has a length of λ/4, where λ=c/f, c is a speed of light, and f is a frequency of the assisted GPS signal
Implementation Method 2
an active low-pass filter, an output of the active low-pass filter is connected to a main antenna
Implementation Method 3
An input of the duplexer is connected to a transmitter through a power amplifier
Data Source
AI summary
Provided in the present application are a band14 signal suppression circuit and a smart terminal device being equipped with a duplexer, an active low-pass filter, and a resonant filter in a band14 transmission path, implementing filtering and suppression on the second harmonic in the band14 signal, and eliminating the interference of band14 signals on assisted global positioning system signals.