Differential Electrical Balance Duplexer With Four-Coil TX/RX Isolation

The EBD is divided into four independent coils (first coil for TX, second coil for RX, third coil for ANT, fourth coil for BAL) that can be independently designed and optimized. Each coil is coupled to a different port and can be tuned separately, allowing independent optimization of TX and RX paths while maintaining isolation. This segmentation enables better control over insertion loss and isolation performance compared to conventional single-ended designs.

The patent employs asymmetric coil configurations where the first and second coils have different numbers of turns, different areas, or different geometries optimized for their respective functions. The first coil (TX) and second coil (RX) can have asymmetric designs that optimize their individual performance characteristics, while the third and fourth coils provide asymmetric coupling paths that enhance isolation. This asymmetry allows tailored optimization for transmit and receive functions.

The patent utilizes multi-layer PCB construction where coils are distributed across different layers (first coil in first layer, second coil in second layer, third and fourth coils in third or fourth layers). This three-dimensional spatial arrangement provides inherent DC isolation between ports while maintaining electromagnetic coupling where needed. The vertical separation in layers eliminates direct DC paths between TX, RX, ANT, and BAL ports, achieving superior DC isolation without complex manufacturing processes.

The patent introduces balanced differential signaling as an intermediary mechanism between the four coils. By using differential pairs for each port and ensuring symmetric coupling paths, the design achieves DC isolation while maintaining signal integrity. The balanced structure acts as an intermediary that blocks DC paths while allowing AC signal transmission, improving DC isolation without significantly increasing manufacturing complexity.

The patent pre-configures the four-coil structure with optimized coupling characteristics that inherently maintain isolation across a wide impedance range. The symmetric differential design and carefully designed coil geometries create a robust isolation mechanism that does not require dynamic adjustment. The balance network can be statically tuned during manufacturing to provide adequate isolation without complex real-time control, performing the isolation function in advance rather than requiring continuous adaptation.

The differential four-coil structure provides self-balancing characteristics where the symmetric design automatically maintains isolation without external control. The inherent symmetry of the differential paths ensures that common-mode signals are rejected and differential signals are transmitted with minimal interference. This self-service mechanism maintains TX/RX isolation through the fundamental symmetry of the structure rather than requiring active impedance tracking or complex control systems.

The patent designs the four coils with universal coupling characteristics where each coil can be independently tuned but follows a standardized design template. The coils use common geometric patterns and coupling mechanisms that can be manufactured using standard PCB processes. This universality allows design flexibility for different frequency ranges and impedance values while maintaining manufacturability through standardized construction methods and reduced precision requirements.

The patent enables design flexibility by allowing independent adjustment of coil parameters such as number of turns, area, geometry, and layer position for each of the four coils. These parameter changes can be made to optimize performance for different applications without changing the fundamental four-coil architecture. The ability to vary parameters like turn ratios and coupling distances provides adaptability while maintaining reasonable manufacturing precision requirements through standard PCB fabrication tolerances.