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https://wiki.analog.com/university/courses/electronics/electronics-lab-28 

https://www.electronics-tutorials.ws/oscillator/crystal.html

https://www.researchgate.net/publication/276200630/figure/fig1/AS:393490560241665@1470826868590/D-flip-flop-using-pass-transistors.png

https://wiki.analog.com/university/courses/alm1k/alm-lab-29

 

Block diagram of the Frequency Synthesizer

Oscillators used in RF transceivers are usually embedded in a synthesizer environment to precisely define their output frequency. The oscillator used is not as stable as desired and might show drift caused by environmental factors. Making use of a PLL-like structure to lock the oscillator to a more stable Xtal at 2MHz, we can decrease the drift significantly and correct the phase of the output signal. 

 

Overview of the Frequency Synthesizer design:

 

The Synthesizer exists of three parts:

  • Crystal Oscillator (2MHz)
  • Frequency Divider (/2)
  • Phase comparator

The Oscillator and Mixer are not part of the scope here.

 

Crystal Oscillator

Pierce Xtal oscillator, a lot of trial and error in choosing the right components for the correct frequency. The NOT gate is needed for the 180* phase difference to satisfy the Barkhausen criteria and keep the oscillator running. a single CD4007 IC is needed to construct the NOT gate.

 

Frequency Divider

A D-flipflop with Q_bar connected to CLK. The circuit uses 4 NAND gates and 1 NOT gate, making use of 4 CD4007 ICs in total

 

Phase Comparator

The phase comparator is an XOR gate, comparing the input signals in a XOR fasion. The XOR gate needs 4 NAND gates to operate, thus 4 ICs are needed

 

Gates

The gates are constructed using the CD4007 IC, below is a depiction of a NAND gate constructed from 2 transistor totempoles/NMOS-PMOS pairs

 

a NOT gate is constructed using a single totempole

 

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