Determining Antenna Separation Requirements for Co-Located Transmitters
Minimum antenna separation depends on transmitter power, receiver blocking thresholds, intermodulation mixing products, and regulatory simultaneous exposure ratios.
Defected Ground Structure
Meaning
Microstrip transmission lines can be modified by etching specific geometries into the metallic ground plane to alter the transmission characteristics. The defected ground structure is this patterned disturbance, which acts as a filter to reject unwanted frequencies. This structure creates bandstop behavior by disrupting the return current path on the reference plane.
Circuit Resonance
Altering the return path increases the effective inductance and capacitance of the transmission line without requiring additional discrete components. When designing a compact transceiver, a defected ground structure allows the engineer to implement low-pass or bandstop filters directly on the circuit board, saving valuable real estate. The frequency response is determined solely by the shape and dimensions of the etched pattern.
Physical Implementation
Etching the ground plane changes how currents flow and can cause radiation leakage. This leakage might interfere with nearby sensitive receiver circuitry or fail electromagnetic compatibility tests if not managed. Designers must place these ground defects away from noisy digital traces and secure the circuit within a shielded enclosure.
Integration Consequence
Layout verification tools must model the non-continuous ground plane carefully to predict performance. A miscalculated defect size shifts the resonance frequency, rendering the filter ineffective. Correct layout ensures proper suppression.