PIM Testing Certification: What You Need to Know

Passive Intermodulation (PIM) testing is no stranger to the wireless industry. In fact, it is a standard for radio site commissioning and certification. PIM’s history dates back to the beginning days of radio communication and has become a major performance issue for wireless carriers in recent years. Because of its longevity and subsequent effect, PIM testing is necessary and therefore certain PIM testing certification has been put in place.

What is PIM?

PIM occurs when two or more high power RF signals encounter non-linear electrical junctions or materials in an RF path. These non-linear junctions behave like a mixer causing new signals to be generated at mathematical combinations of the original RF inputs. When these PIM signals fall in the Rx band of the cell site the noise floor rises causing increased dropped calls, reduced data transmission rates and decreased system capacity. The impact of PIM on the network performance can be severe, especially for systems such as CDMA, UMTS or LTE.

Wireless broadband and 4G networks, utilities, government agencies and private users are converging to higher data rates with higher spectral bandwidth requirements, which makes to reducing PIM at radio sites even more necessary, according to pimtesting.com. PIM testing and certification of all new sites is required among wireless networks. Testing existing installations in an effort to increase call quality and reduce lost data is also required.

“Effective PIM testing requires knowledge, practical skills and appropriate tools. Because of this, companies such as Kaelus and OnPoint Testing now offer on-site training workshops to teach engineers, technicians and installation crews the skills needed to construct and maintain “low PIM” RF infrastructure.

To paint the picture of what’s required within pim testing certification, we’ll cite the Kaelus class an example. First of all, the One Day Course is moderately technical and does not require prerequisites although prior radio or installation experience is a plus. Students should plan on learning what PIM is, how it is tested and the difference between PIM testing and other antenna testing techniques. “This course is more than 50% hands-on with test equipment, site RF network simulations, and verifications associated with instrument operation.” [1] The following are types of skills needed to become PIM testing certified:

Introduction to PIM

• Product overview
• Term & definitions
• Standards defined
• What is PIM
• Why PIM is important
• Fixed Frequency Testing

Technology Overview

• dB – dBm – dBc
• Intermodulation overview
• Spurious Emissions
• Radiated – non-radiated sources
• Loads and antennas
• PIM Vs Line Sweep
• Methods & Procedures

How PIM is created

• Internal PIM sources
• External PIM Sources
• Finding the right frequencies

Summary and Review

• Core elements review
• Questions and answers