E.g. ESP 32 has an internal clock of 240MHz, but can transmit at 2.4GHz (following 802.11 standard). How is this accomplished? Does it really generates a wave at 2.4GHz frequency? Is it not limited by the internal clock? I know it's digital modulation and I'm still learning about RF so any recomended literature would also be appreciated.

  • \$\begingroup\$ 240MHz isn't the internal clock so much as the clock the processor is fed and runs at \$\endgroup\$ – DKNguyen Dec 26 '19 at 14:32
  • \$\begingroup\$ Thanks! I didn't knew that. \$\endgroup\$ – bestgholaever Dec 26 '19 at 14:36
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    \$\begingroup\$ Yes, most systems have multiple internal clocks. \$\endgroup\$ – pjc50 Dec 26 '19 at 14:41

Modulation is not typically done at the carrier frequency, but rather at a lower frequency and upconverted. In the era of digital modulation, it's not even uncommon for the key processing to be done in the context if IQ signals centered on a frequency if 0 Hz.

Upconversion does require a local oscillator, but this is a sine wave rather than square, and only drives a small part of the radio circuitry, not the chip in general. Typically today that would be synthesized in relation to a convenient frequency crystal.

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  • \$\begingroup\$ Thanks! This helps me a lot. Have a nice one. \$\endgroup\$ – bestgholaever Dec 26 '19 at 14:37

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