Near and Far Field Antenna Measurement

To obtain optimal performance in an over the air RF system, the antennas must be chosen to meet specific requirements. Performance parameters such as size, wind-loading, environmental ruggedness, transmission pattern,bandwidth, and power handling capability should be considered. Especially important in an RF system design is the“link budget”. This parameter determines the end-to-end RF loss and is affected by transmitter output power, feedline loss, transmit antenna gain, path loss through the air, receiver antenna gain, feedline loss once again and receiver noise-figure among other factors. A failure to meet the link budget in an RF system design will result in noisy performance and loss of coverage. In this application note, methods of measuring the transmission (or reception)pattern which determines antenna gain with a VNA will be examined.