At Knowles Precision Devices, we support a wide variety of industries and applications with unique needs; the product catalog is constantly evolving to accommodate. We are often asked which frequencies we support. While our microwave products excel at higher frequencies, the catalog spans a wide range.

The US MIL-STD-461 specification manages electromagnetic interference emissions by setting limits on the levels that can be emitted from electrical equipment. This specification also sets regulation to control equipment susceptibility to external noise sources and establishes guidelines for properly measuring the relevant equipment features.

EMI filtering plays an important role in reducing noise that could interfere with other devices; in medical or defense applications, for example, false alarms due to external interference could be detrimental. Here, we will continue our EMI filtering exploration with application and installation considerations. For earlier reading, review EMI filtering basics and filter performance.

To comply with international legislation such as the EU Directive on EMC or the FCC, EMI filtering is an essential element of equipment design. Here, we will continue to explore EMI filtering through insertion loss and filtering performance.

The insertion loss performance shows signal attenuation at any given frequency. As a metric, the insertion loss performance is most useful as a guide in the filter selection process; the actual performance in service can vary depending on circuit characteristics.

In the race to implement mainstream 5G wireless communication, the world is waiting to see if this next-generation network will achieve a hundredfold increase in user data rates. This transformative technology not only boosts performance for the latest cell phones, but also for fixed wireless access (FWA) networks and Internet of Things (IoT) smart devices. In order to reach 10 Gbps peak data rates, the increase in channel capacity must come from somewhere. A key innovation at the heart of 5G is utilizing new frequencies greater than 20 GHz in the millimeter wave (mmWave) spectrum, which offers the most dramatic increase in available bandwidth.

With the ever-increasing use of electronic equipment comes a greater likelihood of interference from all the other equipment out there. In the same vein, we’re seeing more circuits, with lower power levels, that are easily disturbed; so, there’s a need to protect equipment from EMI (electromagnetic interference). In automotive or medical applications, for example, there can be no false alarms due to external interference. The level of uncertainty has pushed EMI compliance testing to the component level.

To meet international legislation such as the EU Directive on EMC or the FCC, EMI filtering is an essential element of equipment design. Introducing screening measures to case or cables, for example, may suffice in many instances, but you might need to introduce low-pass filtering for additional protection as well. Here, we will begin to explore EMI filtering and the terminology used in designing effective protection.

In mission-critical applications, additional screening and testing is required to ensure that only the most robust parts make it to the finished product. Preventative measures, like high quality standards, lessen the possibility of failure in the field and minimize the likelihood of astronomical downstream costs.

Supply noise creates challenges in RF systems where it can mix with RF signals, impacting signal-to-noise ratios and potentially causing spurious output. Thus, high-frequency monolithic microwave integrated circuit (MMIC) amplifiers with broadband gain need to be protected from RF noise on the supply lines. Avoiding these issues with supply line noise requires RF designers to use a bypass capacitor that provides an efficient path to ground for RF energy on the supply line before it enters a gain stage (Figure 1).

Imaging systems account for a significant portion of the medical devices and electronics industry. There is an expanding range of imaging modalities, and one of the most common is magnetic resonance imaging (MRI). MRI equipment uses a strong magnetic field and computer-generated radio waves to create cross sectional images of the body; these images enable health care professionals to investigate and diagnose without the need for an invasive procedure.

One of the questions we get asked regularly is:

‘why not just integrate a filter in the board stack?’

Our answer to this comes in two parts: First there are manufacturing tolerances to consider, and second there is size.