3 Most Common Bandpass Filter Types

Did you know that the Radio Frequency (RF) filter market is set to surpass $45 billion USD by the end of 2035? With the explosion of microelectronics, especially in the defense and aerospace industries, various bandpass filter types (and others!) are growing in need around the world.

Source: Global RF Filter Market Share, Research Nester

This growing market opportunity isn't just indicative of technological progression, but also underscores the paramount role RF filters play in today's global ecosystem.

But what applications are they actually used around the world? Bandpass filters, as we know, are used in a variety of applications to selectively pass frequencies within a certain range while rejecting frequencies outside that range. 

In this article, we cover the three most common bandpass filter types, and how they are used in modern industries. Let’s jump in.

So, what are the most common bandpass filter types?

1. LC (Inductor-Capacitor) Bandpass Filters

This is perhaps the most common type of bandpass filter, especially in lower frequency applications. They consist of a network of inductors (L) and capacitors (C) and their operation is based on the resonance characteristics of LC circuits. 

Depending on the arrangement of these components, different types of filters such as Butterworth, Chebyshev, and Elliptic can be designed. Each of them has unique characteristics in terms of passband flatness, roll-off steepness, and ripple level.

What are their real-world applications?

In military and defense, these RF filters are often used in radio communication systems and electronic warfare equipment. LC filters are ideal for low-to-mid-frequency applications where size and cost are more crucial than extreme performance.

In broadband communications, LC filters can be used in cable modems, set-top boxes, and infrastructure equipment to separate signal channels. They filter out unwanted electronic signals and reduce interference.

2. Surface Acoustic Wave (SAW) Bandpass Filters

SAW filters are used in RF and microwave applications where a high performance level is required. They operate by transforming an electrical signal into an acoustic wave and then turn it back into an electrical signal. 

What are their real-world applications?

Given their ability to handle high frequencies with good performance, SAW filters are commonly used in wireless communication systems. This is due to their ability to handle high frequency ranges, typically from around 10 MHz up to several GHz.

In the military, these might be used in secure radio communications, radar systems, or electronic countermeasure devices. 

Regarding space technology, SAW filters can be used in satellite communication systems. Their high frequency capability and tolerance to harsh conditions makes this suitable for the environment of space. 

For commercial or broadband communications, SAW filters are prevalent in mobile communications devices, for example, smartphones. They filter and separate the numerous frequency bands used in 4G, 5G, and beyond.

3. Cavity Bandpass Filters

These are high-Q filters used in microwave applications. They are composed of a series of resonant cavities, each of which allows a specific frequency to pass. They are known for their high selectivity and power handling capabilities, but are generally larger and more expensive than other types of RF filters. 

What are their real-world applications?

Due to their high selectivity and power handling capabilities, cavity filters are often used in high-stakes, high-frequency applications. This can include radar and satellite communication systems.

In the military, this might mean air traffic control radars, naval communication systems, or missile guidance systems. 

For the space industry, these filters can be used in spacecraft communication systems. They can reliably handle the high frequencies typically used in these applications.

In broadband communications, they can be used in base station infrastructure for mobile networks, particularly where high power handling is required.

Bonus Bandpass Filter Types:

It's also worth mentioning microstrip filters and ceramic bandpass filters. These two bandpass filter types are also often used in various RF and microwave applications. These filters offer a good compromise between performance, size, and cost.

Ready to Select Which Filter You Need?

Overall, your choice of a specific bandpass filter type depends on the unique requirements of the application. These might include:

• The necessary frequency ranges
• Signal power levels
• Size and weight constraints
• Environmental conditions
• Cost considerations
• The timeliness of when you need this microwave component

If you can’t find an off the shelf filter and need a custom bandpass filter for your needs, contact our engineering team. Once you send over your project’s prerequisites, we can provide a cost and timeline estimation.

Download this PDF table to easily fill in your project requirements!

We can’t wait to help your project be a success! We specialize in filters that provide superior performance. There is a list of reasons why our RF engineers have been trusted for 25+ years supporting mission-critical systems:

• Low-cost production
• U.S. based facilities
• Classified test capabilities
• Responsive manufacturing
• First-class RF engineering

Connect with Q Microwave's experienced team for efficient bandpass filter prototyping. You will benefit from 8-12 weeks lead times for prototypes utilizing our in-house standard packaging.