Many microwave applications, such as repeaters, and electronic warfare equipment, require increased spectral resolution. This means these devices only need to look at a narrow slice of a given band. Filters that are optimized for the whole band, such us our planar microstrip devices, are too broadband for these applications. Likewise, traditional high Q filters, such as waveguide devices, are often too large to consider using in these types of applications.
Instead of trying to make a broadband microwave filter or bulky waveguide device do the job, a narrow band, low-loss cavity filter can offer users the ability to more accurately look at just the required part of the spectrum of interest.
Developing the Perfect Cavity Filter for Your Application
Alongside our thin film microstrip approach to making microwave filters, Knowles Precision Devices also has the expertise to create custom ceramic cavity filters from 6GHz to 67GHz. Based on their decades of experience, our RF engineers and material scientists can work directly with clients to fabricate a design for their application, or they can create a design based on predetermined specifications.
In general, our ceramic cavity resonator technology can be employed in conjunction with the stable, high Q ceramics we develop to create a highly selective, small, low-loss cavity filter. Using a multi-port implementation, we can deliver a robust filter with wide reject band performance without spurious modes. The small, shielded nature of the ceramic filter implementation makes it an ideal choice for integration in low noise receiver front ends with an antenna and pre-amplifier.
Figure 1. A basic depiction of a cavity filter designed by Knowles Precision Devices
Some of the key features of the ceramic cavity filters we typically design include the following:
- Small size – 0.8 x 0.2 x 0.03 inches for a 10 GHz filer
- LO/Multiplier chains/RF pre-select/image filtering
- Low loss in passband: 2-4 dB typical
- Devices scalable from C to Ku band
- Bandwidth 1 to 5 percent
- Narrow footprints are great for switch filter banks
- Surface mount or wire bond capable
- No external shielding required
When developing your next microwave application, if you require a filter that will allow you to focus on a narrow slice of the spectrum and you need high reliability and precision, Knowles Precision Devices engineers can work with you to co-develop the perfect custom cavity filter.