Meaning
Unwanted electromagnetic signals generate at whole-number multiples of a transmitter’s primary operating frequency, causing potential interference to other radio services. Devices emitting spurious harmonics risk failing regulatory compliance tests and must be shielded or filtered to meet international standards. These emissions are caused by the non-linear behavior of high-frequency power amplifiers during operation.
Signal Emission
Non-linear circuits generate these out-of-band signals whenever the power amplifier runs close to its limit. If left unmanaged, the signals travel to the antenna and radiate into the surrounding space. This radiation interferes with other wireless services.
Filter Performance
Low-pass or bandpass filters placed between the amplifier output and the antenna must be used to block these unwanted signals. The filter’s design must offer high attenuation at the harmonic frequencies while causing minimal loss at the operating frequency. This filtering is crucial to maintain clean transmissions.
Compliance Violation
National telecommunication agencies set strict limits on the strength of unwanted emissions to protect public safety and communication networks. When a device exceeds these limits, it cannot be sold or operated in those regions. Checking for these emissions during early development stages prevents expensive board redesigns and avoids delays in the product certification process.
