In this blog post we explain, in simple terms, the concept of impedance matching and why it is important in the context of dielectric heating with radio frequency. In a later post, we’ll take a deeper, more technical look at this topic. But for now, enjoy a little journey to the sunny south of France.

It’s a beautiful late afternoon on a warm summer's day somewhere near Nice. In front of you are dozens of flower pots with your amazing collection of Mediterranean flowers. It has taken you years to grow them to this size. They look thirsty. So, you get the garden hose, turn on the water and give your precious plants a drink before pouring an apéro for yourself.

But actually, this little pleasure is a little more complicated than you thought. The pots are of many different sizes, from tiny to huge. Some you can reach, while others are hidden a couple of rows behind others. All you have is your garden hose with constant flow and constant pressure. The small pots fill quickly, spilling precious water. The large pots are taking a long time to fill. And those hard to reach ones, right at the back, well, you need more pressure to get to those.

At the end, only a few of your flower pots match nicely to your water hose. They are of the right size and the right distance, they fill up quickly and no water is wasted. But for the others, the process is inefficient, either too slow, too much pressure, not enough pressure, and so on.

The analogy isn’t perfect, but you get the point: Ideally each flower pot size and distance would have a different hose with carefully adjusted water flow and pressure. And, so it is within the world of dielectric, radio frequency heating.

Every customer we talk with has a different application and a different material to heat. Each one requires a specific applicator - the device that applies the RF energy to the material to be heated. In our analogy above, this corresponds to the flower pots. Lots of sizes, shapes and required power levels. Now we have to add a bit of complexity to complete the analogy: Where is the water coming from? Probably from a well with a pump, or from your mains water supply. No matter where it comes from, it will have a constant ratio of pressure to flow rate. In the RF world, this is the RF generator and the ratio of pressure (voltage) to flow rate (current) is called the impedance, and it is a fixed value. We call this the source impedance.

The concept of impedance can now also be transferred to the flower pots: You will find an ideal ratio of pressure to flow that depends on the size and the distance of the flower pot. One that fills the pot with the greatest efficiency without wasting water. To achieve this, load and source impedance should ideally be the same, but rarely ever are.

Therefore, almost all RF applications include a device called an Impedance Matching Network, or variations on that theme. In our case, this sits between our RF generator and the applicator, fine-tuning the RF from the generator to the applicator and into the load. Whilst what we build is large scale, high-power RF, this same "matching" technology is even your mobile phone. Here it ensures that the antenna properly matches the reception and transmission circuit inside the phone. Without it, the phone's battery wouldn’t last as long and the range would be miserable.

So, whilst there is a lot of focus on RF generators, one has to also consider the topic of impedance matching. SolidWatts are here to help. Not only do we offer a new generation of solid-state RF generators - specifically designed for industrial dielectric heating applications - but we also offer impedance matching solutions. By working with you we will ensure a matching network solution to ensure the lowest possible losses and the highest possible energy efficiency.

If you have questions about RF heating or the process of matching RF to your application, please contact us. We’d be happy to share our experience with you.