Hey there! As a supplier of CMOS oscillators, I've been getting a lot of questions lately about how to suppress spurious signals in a phase-locked loop (PLL) with a CMOS oscillator. So, I thought I'd write this blog to share some tips and tricks that I've picked up over the years.
First off, let's talk about what spurious signals are. Spurious signals are unwanted frequencies that can show up in a PLL output. These signals can cause all sorts of problems, like interference with other signals, reduced performance, and even system failure in some cases. So, it's important to get rid of them as much as possible.
One of the most common causes of spurious signals in a PLL with a CMOS oscillator is noise. Noise can come from a variety of sources, including the power supply, the oscillator itself, and external interference. To reduce noise, you can start by using a good quality power supply. Make sure it's well-regulated and has low ripple. You can also use decoupling capacitors to filter out any high-frequency noise.
Another way to reduce noise is to use a low-phase-noise oscillator. At our company, we offer a Low Phase Noise VCO Oscillator 9 X 7 that's designed to have very low phase noise. This can help to reduce the amount of spurious signals in the PLL output.
In addition to noise, another cause of spurious signals can be the loop filter in the PLL. The loop filter is responsible for filtering out unwanted frequencies and controlling the loop dynamics. If the loop filter isn't designed properly, it can introduce spurious signals. To avoid this, you need to make sure the loop filter is designed to have the right bandwidth and phase margin.
One way to design a good loop filter is to use a simulation tool. There are several simulation tools available that can help you design a loop filter that's optimized for your specific application. You can also consult with an expert in PLL design to get some advice on the best loop filter design for your needs.
Another thing you can do to suppress spurious signals is to use a frequency synthesizer. A frequency synthesizer can generate a stable output frequency by using a reference frequency and a phase-locked loop. By using a frequency synthesizer, you can reduce the amount of spurious signals in the output.
At our company, we offer a Programmable Oscillator 5032 that's a type of frequency synthesizer. It's programmable, which means you can set the output frequency to your desired value. This can be very useful in applications where you need to change the output frequency frequently.
Finally, you can also use shielding to reduce the amount of external interference. Shielding can help to block out any electromagnetic interference (EMI) that could be causing spurious signals. You can use a metal enclosure or a shielded cable to provide shielding.
In conclusion, suppressing spurious signals in a PLL with a CMOS oscillator can be a bit of a challenge, but it's definitely doable. By following the tips and tricks I've shared in this blog, you can reduce the amount of spurious signals in your PLL output and improve the performance of your system.
If you're interested in learning more about our CMOS oscillators or have any questions about suppressing spurious signals, feel free to reach out to us. We'd be happy to help you find the right solution for your needs. Whether you need a TXO SMD Oscillator 2016, a Programmable Oscillator 5032, or a Low Phase Noise VCO Oscillator 9 X 7, we've got you covered. Let's start a conversation about your requirements and see how we can work together.
References
- "Phase-Locked Loops: Design, Simulation, and Applications" by Roland E. Best
- "CMOS Circuit Design, Layout, and Simulation" by R. Jacob Baker