This article discusses the characteristics of ceramic resonators and measures to reduce noise in ceramic resonators. Ceramic resonators utilize the mechanical resonance properties of piezoelectric ceramics, typically lead zirconate titanate (PZT), with the vibration mode changing with the resonant frequency. As a mechanical oscillator, ceramic resonators are well-known alongside quartz crystals, while LC and CR oscillating circuits utilize electric resonance.

Characteristics of Ceramic Resonators:

1. Highly stable oscillation frequency

The frequency stability of ceramic resonators is between that of quartz crystals and LC or CR oscillating circuits.

The temperature coefficient of the oscillation frequency of quartz crystal oscillators is extremely high at 10/°C, while that of LC or CR oscillating circuits is around 10 to 10/°C. The temperature coefficient of ceramic resonators is 10/°C within the range of -20 to +80°C.

2. Small size and lightweight

Ceramic resonators have dimensions that are only half the size of commonly used quartz crystals.

3. Low cost and no adjustment required

With the use of ceramic resonators, customers can achieve mass production. Unlike CR and LC circuits, ceramic resonators utilize mechanical resonance instead of electric resonance, meaning that they are not significantly impacted by external circuit or power voltage fluctuations. This allows for the creation of highly stable oscillating circuits that do not require adjustment.

Measures to Reduce Noise in Ceramic Resonators:

1. Increase load capacitance

Increasing load capacitance enhances the effect of low-pass filtering, reducing microwave noise. However, this also slightly lowers the oscillation frequency. If the load capacitance is increased too much, oscillation will stop.

2. Increase damping resistor (Rd)

Increasing the damping resistor further increases the load capacitance, enhancing the effect of low-pass filtering, correcting the matching between ceramic resonators and integrated circuits, and suppressing ringing caused by reflections. Additionally, this method reduces current consumption and suppresses noise. If the damping resistor is increased too much, oscillation will stop.

3. Install ferrite beads between the load capacitance and ground

Installing ferrite beads can lower microwave gain and suppress noise. However, if the inductance or loss caused by ferrite beads is too high, oscillation may stop or abnormal oscillation may occur.

Even with the use of these three methods to suppress noise, it may still be ineffective as different integrated circuits and ceramic resonators can affect the effectiveness of noise suppression. In particular, for third harmonic ceramic resonators, the circuit constants produce little additional gain, so circuit constants must be comprehensively considered.

These are the characteristics of ceramic resonators and measures to reduce noise in ceramic resonators. I hope this information is helpful to you.