Fast frequency hopping and frequency agility are important capabilities for satellite direct-to-device (D2D) communications. Satellites serving multiple geographic regions can need to support different frequency channels or bands. Frequency agility enables satellites to switch frequency bands or channels based on spectrum availability, regulatory restrictions, and interference conditions.

The direct RF-sampling architecture of the AFE8030 is an excellent choice to address these requirements, because frequency conversion in AFE8030 is performed digitally using NCOs, enabling rapid frequency reconfiguration without relying on analog local-oscillator retuning.

In AFE8030, each transmitter/receiver paths support up to two DUC/DDC chains, with two independently configurable NCOs per digital mixer. The device can switch between the two NCOs while maintaining phase-continuous operation, with switching controlled through either SPI commands or dedicated GPIO signals.

NCO-based frequency hopping can achieve settling times on the order of a few hundred nanoseconds. The total hopping time includes the latency associated with the SPI command or GPIO trigger, as well as the digital signal-chain transition required to flush out invalid samples.

As shown in Figure 5-4, the AFE8030 demonstrates a transmitter frequency-hopping time of approximately 215ns when switching between two NCO frequencies using a GPIO trigger.

Figure 5-5 demonstrates the phase continuity with the fast frequency hopping, where RX channel B is the reference channel with NCO frequency set as NCO1, the NCO frequency of RX channel A switches from NCO1 to NCO2 and then back to NCO1. The initial phases of both RX channels are aligned, as shown, the RX channel A NCO phase remains aligned with RX channel B following the frequency hopping from NCO1 to NCO2 and back to NCO1.

In addition to the fast frequency hopping feature, in AFE8030, the frequency and phase of each NCO can be programmed independently, which can also be utilized to compensate the frequency offset due to Doppler shifts, or provide the digital phase control of the digital beams.

By combining fast frequency switching, independent NCO configuration, and digitally controlled frequency and phase adjustment, the AFE8030 enables frequency-agile radio architecture capable of adapting to the dynamic operating conditions of satellite D2D/IoT networks.