PA Output Filter Detuning for Cross-Band Harmonic Isolation
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Solution Overview
Problem
Transmitter and power amplifier modules face challenges in achieving effective cross band isolation and forward isolation, as harmonic frequencies from the low band can crossover into the high band and input signals can reach the antenna port, leading to performance degradation.
Innovation Solution
The implementation of detuning filters and a matching network with a harmonic trap circuit that switches between modes to block harmonic frequencies, using inductors, capacitors, and a controlled switch to provide improved isolation by altering impedance based on operational frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional filter and matching network designs are used, then basic signal transmission is achieved, but cross band isolation and forward isolation are insufficient, allowing harmonic frequencies to reach the antenna port
Solution Approach 1:
The patent applies dynamics by making the filter and matching network tunable through switching between different capacitor configurations. The controlled switch enables dynamic reconfiguration of the filter circuit to adapt to different operating bands, transforming a static filter design into a dynamic one that can actively adjust its characteristics to block harmonic frequencies while maintaining signal transmission.
Solution Approach 2:
The patent changes electrical parameters by switching between different capacitor connections (series/parallel configurations) to alter the impedance characteristics of the filter and matching network. This parameter change allows the same circuit to provide different isolation levels for different frequency bands, improving cross band isolation without requiring completely separate filter circuits for each band.
2Object-affected harmful factors
If detuning filters and harmonic trap circuits are added to improve isolation, then cross band and forward isolation are enhanced, but device complexity increases
Solution Approach 1:
The patent achieves multi-functionality by designing the filter and matching network to simultaneously perform multiple functions: signal transmission, harmonic blocking, and impedance matching. The same circuit components (inductors, capacitors, and switch) serve dual purposes of maintaining signal integrity while providing isolation, eliminating the need for separate dedicated isolation circuits.
Solution Approach 2:
The patent merges the detuning filter and harmonic trap circuit functions into the existing filter and matching network structure. By integrating these isolation functions with the signal path components rather than adding separate parallel circuits, the patent reduces overall device complexity while achieving improved cross band and forward isolation.
3Productivity
If fixed impedance matching is used, then simple circuit design is maintained, but performance degrades when harmonic frequencies are present
Solution Approach 1:
The patent transforms the fixed impedance matching network into a dynamic one by incorporating switching capability between different capacitor configurations. This allows the matching network to adapt its impedance characteristics based on the operating band, maintaining optimal performance for both fundamental frequencies and providing additional isolation for harmonic frequencies without sacrificing circuit simplicity.
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 solution enhances cross band and forward isolation by effectively trapping harmonic frequencies, reducing their impact and improving the overall performance of transmitter and power amplifier modules.
Implementation Method 1
detuning the filter and matching network at the output of the PA... by detuning the filter and matching network at the output of the PA
Implementation Method 2
The circuit comprises a trap at the harmonic frequencies of the low band... using inductors, capacitors, and a controlled switch
Data Source
AI summary
In transmitter modules or power amplifier (PA) modules there is at least a possible path for a second and even a third harmonic of a low band to crossover unfiltered into the high band path and reach the antenna and hence cross band isolation is necessary. Forward isolation is necessary in order to limit the input crossing over the PAs into the antenna port. According to the methods and the circuits such cross band isolation and forward isolation is improved by detuning the filter and matching network at the output of the PA. The circuit comprises a trap at the harmonic frequencies of the low band thereby at least reducing the impacts of the cross band and forward isolation.