Pierce Oscillator based on BFQ19S (435.65Mhz)

tags: RF circuit module design RF microwave Pierce Resonantless resonator

Key devices: transistor BFQ19S (Infineon), and resonator without a chance (Huayuan).

Debugging process:

1) The initial circuit is as follows:

Under this circuit parameters, the circuit does not vibrate! !

2) In this circuit, since the rimless resonator is used as a high Q value inductor, it cannot be adjusted. Therefore, reducing the capacitance value of C11 and C12 is 2.2pF to increase the feedback coefficient, which is conducive to vibration start. However, after changing to a capacitor, it still did not start.

3) Change the R63 resistance value to 120Ω, and the circuit finally vibrates. The oscillation frequency is 435.65Mhz, which will be lower than the nominal frequency of SRF435A 435.72Mhz, making SRF435A inductive.

4) Connect to the spectrum meter to observe its frequency stability and phase noise. When observing, you can find its frequency stability ratio (Design of co-emission oscillator based on BFQ19S (Clasp Capacitor Three-Point)) Be good, and the phase noise is better than it.

5) During the debugging process, adjusting the resistor R63 to 0Ω can make its output power larger, but after the output power is large, its frequency stability may deteriorate a lot due to the influence of heating, and the frequency jumps more.

Summary: Using high-Q-value components to design an oscillator is more practical than using inductor design. In order to better stability of the oscillation frequency, it is recommended to use a lower power design to reduce the impact of thermal effects.

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