This application note describes the NCO-based frequency hopping capability of the RF-sampling AFE7422 and AFE7444 (AFE74xx). The AFE7422 and AFE7444 are quad-channel, wideband, RF-sampling analog front ends (AFE) based on 14-bit, 9-GSPS DACs, and 14-bit, 3-GSPS ADCs. With operation at an RF of up to 6 GHz, these devices enable direct RF sampling into the C-band frequency range without the need for additional frequency conversions stages. The AFE74xx improvement in density and flexibility enables high-channel-count, multimission systems, and makes these devices a very attractive option for wideband, frequency-hopping applications.
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Frequency hopping describes a method in which communication systems rapidly change the operating frequency for a specific application. Applications such as radar, electronic warfare (EW), and communications use frequency hopping in order to avoid interference, avoid detection, or find signals that are attempting to remain undetected. The faster these systems can change frequencies, or frequency hop, the more agile these systems become, thus increasing the chance to avoid interference and detection. In a traditional frequency hopping system, where an analog mixer and PLL or VCO is used as a local oscillator, changing frequencies can take quite a long time. As RF sampling has become more prevalent, frequency hopping is moving toward a NCO-based hopping technique.