Multiband RF Transmitter Filtering for Isolation Without Insertion Loss
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Solution Overview
Problem
Conventional multiband radio frequency transceivers in FDD communications face challenges in effectively removing receiving band noise while maintaining required transmission insertion loss and isolation characteristics, as existing duplexer solutions are limited in improving isolation without compromising transmission insertion loss.
Innovation Solution
A multiband radio frequency transmitter with a receiving band-rejection filter and impedance compensating circuits that vary the rejection band and impedance to remove receiving band noise, using inductor and capacitor circuits with control signals to adjust resonance and impedance matching, thereby compensating for impedance mismatches and improving noise rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a duplexer is used to offset transmitting and receiving bands, then isolation between bands is improved, but transmission insertion loss becomes worse
Solution Approach 1:
The invention divides the noise filtering function into two separate components: a duplexer for band offset and isolation, and a receiving band-rejection filter for noise removal. This segmentation allows each component to optimize its specific function without compromising the other, thereby maintaining transmission insertion loss while improving isolation and noise rejection
Solution Approach 2:
The receiving band-rejection filter acts as an intermediary component between the duplexer and the receiver. It mediates the signal path by selectively removing receiving band noise while allowing transmitting band signals to pass through with minimal loss, thus resolving the contradiction between isolation and transmission efficiency
2Object-generated harmful factors
If receiving band noise is removed using conventional filters (RC low pass, LC low pass, LC trap), then supply noise is blocked, but receiving band noise is not efficiently removed
Solution Approach 1:
The receiving band-rejection filter is designed with variable filtering parameters that can be dynamically adjusted based on the receiving band frequency. By changing the filtering parameters (such as resonant frequency and Q-factor) to match the specific receiving band, the filter efficiently removes receiving band noise while maintaining supply noise blocking capabilities
3Object-affected harmful factors
If duplexer isolation is improved to required level, then receiving band noise is removed, but transmission insertion loss becomes worse
Solution Approach 1:
The invention segments the noise removal function from the isolation function. The duplexer handles isolation between bands, while the receiving band-rejection filter specifically targets receiving band noise. This segmentation allows receiving band noise to be removed without requiring excessive isolation from the duplexer, thereby maintaining transmission 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 efficiently reduces receiving band noise with minimal power loss, enhances reception sensitivity, and improves duplexer isolation and harmonic performance by dynamically adjusting the rejection band and impedance, maintaining optimal transmission efficiency.
Implementation Method 1
The receiving band-rejection filter may include an inductor circuit and a capacitor circuit. The inductor circuit may be inserted into a signal wiring between the transmitting circuit and the power amplifying circuit. The capacitor circuit may be connected in parallel to the inductor circuit to perform a parallel resonance with inductance of the inductor circuit
Implementation Method 2
The impedance compensating circuit is configured to compensate for impedance mismatch due to the variation of the rejection band of the receiving band-rejection filter
Data Source
AI summary
A multiband radio frequency transmitter of a transceiver in which a receiving band is varied, includes a transmitting circuit, a receiving band-rejection filter, a power amplifying circuit, and an impedance compensating circuit. The transmitting circuit is configured to generate a transmission signal. The receiving band-rejection filter is configured to vary a rejection band in response to a variation of the receiving band, and reject the receiving band from the transmission signal provided from the transmitting circuit. The power amplifying circuit is configured to amplify the transmission signal that passes through the receiving band-rejection filter. The impedance compensating circuit is configured to compensate for impedance mismatch due to the variation of the rejection band of the receiving band-rejection filter.