ESP8266EX——Knowledge Sharing on Clock and RF

乐乐熊

ESP8266EX——Knowledge Sharing on Clock and RF [Copy link]

High-frequency clock
Based on an external crystal, the internal crystal oscillator of ESP8266EX can generate the RF clock. This clock can be used to drive the TX and RX mixers. The crystal frequency is between 24 MHz and 52 MHz.
Although the internal calibration function of the crystal oscillator allows a range of crystals to meet the clock generation conditions, the quality of the crystal is still an important factor affecting the appropriate phase noise and Wi-Fi sensitivity. Please refer to the following table to measure the frequency offset.

External clock reference requirements
The frequency of the external clock is between 24 MHz and 52 MHz. In order to achieve good RF performance, the clock must meet the requirements shown in the following table



RFESP8266EX
RF mainly includes the following modules.
2.4 GHz receiver2.4
GHz transmitterHigh
-speed clock generator and crystal oscillatorBias
and regulatorPower
management moduleChannel

frequencyAccording
to the IEEE802.11b/g/n standard, the RF transceiver supports the following channels.


2.4 GHz Receiver
The 2.4 GHz receiver downconverts the RF signal to quadrature baseband signals and converts the latter to digital signals using two high-resolution, high-speed ADCs. To adapt to different signal channels, the ESP8266EX integrates RF filters, automatic gain control (AGC), DC offset compensation circuits, and baseband filters.
2.4 GHz Transmitter The
2.4 GHz transmitter upconverts the quadrature baseband signals to 2.4 GHz and uses a high-power complementary metal oxide semiconductor (CMOS) power amplifier to drive the antenna. The use of digital calibration further improves the linearity of the power amplifier, achieving an average transmit power of +19.5dBm in 802.11b transmissions and +18dBm in 802.11n (MSC0) transmissions, which is extremely powerful.
To offset the imperfections of the radio receiver, the ESP8266EX also adds the following calibration measures.
Carrier leakage elimination
I/Q phase matching
Baseband nonlinearity suppression
These built-in calibration measures reduce the time and equipment required for production test.
Clock Generator
The clock generator generates 2.4 GHz quadrature baseband clock signals for the receiver and transmitter. All components are integrated on the chip, including: inductors, varactors, loop filters, linear regulators and dividers. The
clock generator contains built-in calibration circuits and self-test circuits. The quadrature clock phase and phase noise are optimized on the chip through a patented calibration algorithm to ensure the best performance of the receiver and transmitter.

rgbgirl

Thanks for sharing, I am learning this information.