Frequency-Variable RF Front-End Circuit for Compact FDD/TDD Isolation

The patent implements a multi-functional front-end circuit that can handle both FDD and TDD systems, as well as multiple communication bands (e.g., 700MHz, 1.5GHz, 2.0GHz) using a shared antenna and shared filtering components. The frequency-selectable filter and switch circuit are designed to dynamically reconfigure the signal path based on the selected communication band and system type, allowing the same hardware to serve multiple functions without requiring separate dedicated components for each band or system.

The patent employs dynamic reconfiguration capabilities through switch circuits that can change connection states based on the selected communication band and system type (FDD or TDD). The frequency-selectable filter dynamically adjusts its filtering characteristics depending on the operating band. This dynamic adaptability allows the circuit to optimize its signal path for different operational modes, enabling compact integration while maintaining proper signal separation for both FDD and TDD systems across multiple bands.

The patent segments the signal processing path into distinct configurable sections: a switch circuit that can connect the antenna to different components, a frequency-selectable filter that provides frequency-based separation, and a band separation filter. For FDD systems, the frequency-selectable filter separates transmission and reception frequencies. For TDD systems, the switch circuit dynamically connects the antenna to either the transmission path or reception path based on the current operation mode. This segmentation allows independent optimization for each system type while maintaining overall integration.

The patent uses dynamic switching mechanisms to adapt the circuit configuration based on the selected system type. The switch circuit dynamically reconfigures the signal path: for FDD operation, it enables the frequency-selectable filter to separate simultaneous transmission and reception signals at different frequencies; for TDD operation, it switches the antenna connection between transmission and reception modes in time-division fashion. This dynamic adaptability resolves the contradiction by providing appropriate signal separation for each system type without requiring separate dedicated circuits.

The patent designs universal filtering components that can handle multiple communication bands. The frequency-selectable filter is configured to provide appropriate filtering for different bands (700MHz, 1.5GHz, 2.0GHz, etc.) through dynamic reconfiguration. The band separation filter is designed with frequency characteristics that can separate signals across multiple bands. This universal design approach allows the same hardware components to serve multiple bands without requiring a separate filtering chain for each band, thereby maintaining compact circuit size while supporting increased adaptability.

The patent merges multiple filtering functions into shared components. The frequency-selectable filter combines frequency selection and band filtering capabilities in a single reconfigurable component. The band separation filter is designed to handle separation for multiple bands simultaneously through its frequency characteristics. By merging these functions rather than implementing separate filters for each band, the circuit achieves multi-band support without proportional increase in size, resolving the contradiction between versatility and compactness.