Multi-Band Communication Module Harmonic Termination for Isolation
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Solution Overview
Problem
Communication modules supporting multiple frequency bands face challenges in maintaining isolation characteristics between input terminals, particularly when these terminals are close to each other, leading to deteriorated isolation due to harmonic leakage.
Innovation Solution
Incorporating a harmonic termination circuit with an inductor-capacitor series resonance circuit and a resistance element, where the second harmonic of the second frequency band is selectively short-circuited to ground, and the distance between the input terminal for the first frequency band and the ground position is longer than the distance between the input terminals, reducing harmonic leakage and improving isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If input terminals for transmission signals of different frequency bands are formed close to each other to reduce module size, then the size of the communication module is reduced, but the isolation characteristics between the input terminals deteriorate
Solution Approach 1:
A harmonic termination circuit is introduced as an intermediary component between the second input terminal and ground. This circuit selectively terminates harmonics (particularly the second harmonic) of the second frequency band, preventing them from interfering with the first input terminal. The circuit includes a series resonance circuit connected between the second input terminal and ground, with the resonance frequency set to terminate specific harmonic frequencies, thereby improving isolation characteristics without increasing the distance between input terminals.
2Reliability
If the distance between the first input terminal and the ground position of the harmonic termination circuit is increased, then the isolation characteristics are improved, but the module size increases
Solution Approach 1:
The harmonic termination circuit utilizes parameter changes in impedance frequency characteristics to achieve harmonic termination. By designing a series resonance circuit with specific inductance and capacitance values, the circuit presents a low impedance path to ground at harmonic frequencies (particularly the second harmonic) while maintaining high impedance at the fundamental frequency. This allows effective harmonic termination with compact dimensions, improving isolation without significantly increasing module size.
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 enhances signal attenuation and reduces noise interference between frequency bands, thereby improving the isolation characteristics between input terminals, even in compact module designs.
Implementation Method 1
The harmonic termination circuit has a series resonance circuit connected between an input terminal for a second signal of a second frequency band and ground
Data Source
AI summary
A communication module includes a first input terminal to which a first signal of a first frequency band is input, a second input terminal to which a second signal of a second frequency band is input, an amplifier that outputs an amplified signal which is obtained by amplifying the first signal, a diplexer that receives the amplified signal and/or the second signal and that outputs an output signal of the first and/or second frequency band, and a harmonic termination circuit that short-circuits a harmonic of the second signal. The harmonic termination circuit has an end connected between the second input terminal and the diplexer, and another end grounded at a ground position. A distance in plan view between the first input terminal and the ground position of the harmonic termination circuit is longer than a distance in plan view between the first input terminal and the second input terminal.