Maintaining strong frequency stability in electronic RF circuits by eliminating phase noise is important in many high-end communication applications. This is especially true for precise targeting in radar systems and spectral purity in other communication systems.

Let's take a deep dive into exactly what phase noise and jitter mean. This will help give you a better idea as to why reducing a system's phase noise is significant.

## What Is Phase Noise?

**Be sure not to confuse phase noise with Jitter. Jitter**is a method of describing the stability of an oscillator in the Time Domain. It combines all the noise sources together and shows their effect with respect to time.

In the simplest terms, phase noise describes the stability of an oscillator in the Frequency Domain, while jitter describes stability in the Time Domain.

## A Simple 5-Step Path to Understanding Phase Noise

### Step 1: Spectral Density

**Step 2:** When plotting each spectral density point at varied frequency intervals of your choosing (In this case every 1Hz), you're left with a graph that looks like this:

### Step 2: Signal Power Density

You are now looking at what is known as the **Signal Power Density **of the noise.

Now focus only on the upper sideband of the graph from fstart to fstop, this is called the "Single Side Band".

### Step 3: Noise Power Density

We can now refer to the plotted part of the single side band as noise (Anything above the nominal oscillator frequency (Fosc) and not harmonically related can be considered phase noise). The technical term for this part of our graph is **Noise Power Density** (Step 3). We measure noise power density in dBW (LOG(Watts)) at this point because of the large range which we are looking.

### Step 4: SSB Noise Density

**SSB (Single Side Band) Noise Density**.

### Step 5: Phase Noise

**phase noise**.

*SSB Noise Density = Phase Noise*## What Causes Phase Noise?

- High vibrations
- Micro vibrations
- g forces and acceleration sensitivity

**Random Noise Sources:**

*Related: Causes and solutions for phase noise in high-end radar and communication systems.*

## What's Next? Learn How to Achieve Low Phase Noise...

*critical*to achieving high-performance. Therefore, it's important to understand an in-depth look at phase noise. Instantly download our free visual guide to the impact of phase noise on various applications.