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.
S21 Scattering Parameter
Meaning
Two-port network analysis utilizes transfer coefficients to measure how much power is transmitted from one port to another in a radio frequency circuit. The s21 scattering parameter represents the forward transmission coefficient, which indicates the gain or loss of the network. This parameter is measured with a vector network analyzer to assess the behavior of cables, filters, or amplifiers.
Signal Transmission
Active devices like amplifiers show a positive value in decibels for this parameter, representing signal gain. When evaluating a passive component such as a coaxial cable or a microstrip filter, the s21 scattering parameter is negative, representing the insertion loss of the device. High loss across the passband indicates poor design or manufacturing defects.
Module Characterization
Transceiver integration requires optimizing the matching network between the radio module and the antenna by evaluating transmission and reflection parameters. Adjusting the components to maximize the s21 scattering parameter ensures that the maximum amount of signal power reaches the antenna rather than being reflected back into the transmitter. This optimization is critical for maximizing range and battery life.
Acceptance Criterion
Production lines test the transmission coefficient of assembled cables to verify quality. If the measured parameter falls below the limit, the cable is rejected. This process ensures reliability.