Photonics-Assisted Instantaneous Frequency Measurement
In the field of electronic warfare (EW), it is of critical importance to analyze an intercepted radio frequency (RF) signal from a hostile radar or communication system. The EW environment is totally different from that of commercial wireless communications, where the carrier frequency, modulation format, and bandwidth of the signal are known. But in an EW environment, the information about the signal is not known, and also the signal is usually specifically designed to avoid being detected by an RF signal receiver. Typically, the frequency of a radar or communication signal can be varied in a range from several hundreds of megahertz to several hundreds of gigahertz, but an RF signal receiver has to be operated in a very narrow frequency band to minimize the noise and interference. An instantaneous frequency measurement (IFM) module is thus required to instantaneously identify the carrier frequency of a unknown RF signal before passing it into a specialized receiver for processing [1–3]. IFM is also of great importance in an EW system to jam an enemy receiver. Typically, a signal emitted by an enemy transmitter would vary in frequency in a predetermined manner. In order to effectively jam such a signal, the frequency of the signal from the enemy transmitter must be accurately and quickly determined. ...