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| 40 account for all the frequency stages, as combinations of the nonlinearity of the amplifiers and RF ADCs often result in harmonics and spur generation that can appear in the signal conversion spectrum. One way to avoid this is to select the sample rates and an intermediate frequency (IF) so that any spurs and harmonics appear out-of-band and can readily be filtered with either analog filters or digital tuners or filters. Direct Digital Synthesis DDS is the generation of signals, often with sub-hertz accuracy, using digital time-varying signals that are then converted to analog signals using an RF DAC. DDS can be very simple, effectively producing simple sine waves, square waves, or sawtooth waves at a wide range of frequencies. It can also be more complex, generating any signal type within the dynamic range and resolution capability of the RF DAC. DDS allows for the generation of RF signals that exhibit excellent phase noise, low spurious content, and, depending on the design complexity, the ability to rapidly change frequency and waveforms for frequency-agile applications. It can also be used as a phase- locked loop (PLL) reference for a wide tunability range, as a local oscillator (LO) for mixing, for some modulation techniques, or to generate RF signals directly. DDS differs from the way traditional arbitrary waveform generators (AWGs), PLLS, and frequency synthesizers generate signals. AWGs generate signals by outputting each sample of a stored waveform. Some waveform manipulation can occur using this stored method, but it is limited in frequency precision by the stored waveform and user-defined waveform functions, as AWGs only have so much memory for each sample point, and the sampling clock can only recreate a finite set of frequencies. DDS can be implemented in a variety of ways, including using a numerically controlled oscillator (NCO), a combination of phase accumulator and phase-to-amplitude converter, or asynchronous memory access. In a complex multi-channel or multi- antenna element solution, several DDS systems can be synchronized to enable advanced amplitude, phase, and waveform control. DDS offers the following advantages: • Sub-hertz frequency accuracy and tuning • Sub-degree phase accuracy and tuning • Fast frequency-hopping speed with phase-continuous frequency hops • Elimination of overshoot/under- shoot during frequency hops • No settling-time anomalies like an- alog hardware varieties • Fast and continuous phase tuning • Component aging, temperature drift, and other anomalies can readily be handled by digital con- trol architecture • Digital control and software programmability allow for remote control, optimization, and automa- tion via programmability or artifi- cial intelligence (AI) and machine learning (ML) High-Speed FAKRA-Mini (HFM) Interconnect System mouser.com/molex-hfm-interconnect-system

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