The term “passive intermodulation” may sound harmless, but it spells trouble for users of wireless networks. Passive intermodulation, or PIM, creates unwanted interference and signal degradation, and can lead to reduced network coverage and increased costs.
Key Takeaways
- Passive intermodulation (PIM) is a major performance issue in modern multi-band wireless networks, especially in 4G, LTE, and 5G systems.
- RF connectors are one of the most common sources of PIM due to metal junctions, mechanical stress, corrosion, and improper installation.
- 2.2-5 low-PIM connectors are engineered with precision materials, tight tolerances, and secure threaded coupling to significantly reduce nonlinear effects.
- Using 2.2-5 low-PIM connectors can improve receiver sensitivity, reduce noise floor, and increase overall network capacity.
- These connectors are especially effective in DAS, small cells, base stations, and surge protection applications where PIM control is critical.
- Proper installation, torque control, cleanliness, and system-wide low-PIM component selection are essential to achieving long-term PIM performance.
What Is Passive Intermodulation (PIM)?
Passive intermodulation (PIM) occurs when two or more RF signals mix in a passive component — such as a connector, cable, antenna, or coupler due to nonlinearities. These nonlinearities are often caused by microscopic imperfections, ferrous metals, loose or corroded surfaces, or improper mechanical connections. The resulting intermodulation products can fall into receive bands, increasing the noise floor and degrading receiver sensitivity. In practical terms, PIM can lead to:
- Reduced system capacity
- Drop in signal quality
- Increased error rates and dropped calls
- Degraded uplink/downlink balance
- Higher operational costs
Because modern networks operate at higher power and span multiple bands, even small amounts of PIM can noticeably compromise performance.
However, over the past decade 2.2-5 low-PIM RF connectors have emerged as a popular solution to PIM distortion in some cases. With their small form factor, such connectors are particularly useful in tight spaces and where lightweight components are desirable.
In this blog post we discuss the main causes and effects of PIM distortion as well as the qualities, benefits, and applications of 2.2-5 low-PIM RF connectors. We also cover a closely related topic − the surge protection needs of wireless networks, and we conclude with information about a PolyPhaser product that meets these needs.
Causes and Negative Effects of PIM
PIM distortion is caused by the nonlinear behavior of materials and components within an RF system. When two or more signals of different frequencies and amplitudes meet within a component or material that exhibits nonlinear behavior, they can mix together and generate additional signals at frequencies that are not present in the original signals. These additional signals can fall within the frequency range of the desired signal or nearby bands, leading to unwanted interference and degradation of signal quality.
Following are some of the harmful effects of PIM distortion:
- Reduced signal quality: PIM can cause a reduction in signal quality, resulting in poor voice and data transmission. This can lead to dropped calls, slow data transfer rates, and poor network performance.
- Increased interference: PIM can create unwanted signals at frequencies that are close to the desired signal, causing interference and reducing the overall signal-to-noise ratio. This can lead to increased noise and reduced network capacity.
- Reduced coverage: PIM can cause a reduction in the effective coverage area of a wireless network. This can lead to dead spots and reduced network capacity.
- Increased cost: PIM can cause increased maintenance and operational costs, as additional equipment and personnel might be required to locate and resolve PIM-related issues.
2.2-5 Low-PIM Connectors
In the early 2010s, 2.2-5 low-PIM connectors were first developed as a smaller and more lightweight alternative to traditional RF connectors such as N and 7/16 connectors. The 2.2-5 connector is designed to minimize PIM distortion, which can degrade signal quality and cause interference with other signals. It is smaller and lighter than traditional connectors like N and 7/16 connectors, making it more suitable for installations in smaller spaces and where weight reduction is desired.
The “2.2-5” designation refers to the connector’s size. The 2.2 is the diameter of the outer conductor in millimeters. The 5 refers to the length of the male pin (or the depth of the female connector) in millimeters.
Since their development, 2.2-5 low-PIM connectors have been widely adopted in the telecommunications industry, particularly in the rollout of 4G and 5G networks. They have also been used in military and aerospace systems, medical devices, and industrial automation.
Benefits of 2.2-5 Low-PIM RF Connectors
There are several benefits of using 2.2-5 low-PIM RF connectors in wireless communication systems:
- Reduced PIM distortion: The design of 2.2-5 low-PIM connectors minimizes PIM distortion, ensuring high-quality, reliable signal transmission.
- Smaller and lighter: Compared to other RF connectors such as N, 7/16, and 4.3-10, 2.2-5 low-PIM connectors are smaller and lighter, making them more suitable for space-constrained and weight-sensitive applications.
- Higher frequency range: 2.2-5 low-PIM connectors are designed to handle a frequency range of up to 2.2 GHz, making them suitable for high-frequency wireless communication.
- Lower insertion loss: 2.2-5 low-PIM connectors typically have lower insertion loss than traditional connectors, which means they can transmit signals with less attenuation.
- Higher power handling capacity: 2.2-5 low-PIM connectors are capable of handling higher power levels than traditional connectors.
- Easy to install: 2.2-5 low-PIM connectors typically have a snap-on design that allows for quick and easy installation without the need for special tools or soldering.
Best Applications for 2.2-5 Low-PIM RF Connectors
Low-PIM 2.2-5 RF connectors are ideal for a variety of applications that require high-quality, reliable signal transmission, particularly in space-constrained and weight-sensitive environments. These applications include:
- Wireless communication systems: 2.2-5 low-PIM connectors are widely used in wireless communication systems, particularly in 4G and 5G networks, where they help to ensure high-quality, reliable signal transmission.
- Distributed antenna systems (DAS): DAS, where multiple antennas provide wireless coverage in large buildings and other areas, are utilized to enhance wireless coverage and capacity indoors and outdoors. Low-PIM 2.2-5 connectors are often employed in DAS installations to help minimize signal loss and ensure optimal performance.
- Small cell systems: Small cell systems are used to provide localized coverage in areas where traditional cell towers are impractical or insufficient. Low-PIM 2.2-5 connectors are well-suited for small cell systems because of their small size and weight.
- Military and aerospace applications: Low-PIM 2.2-5 connectors are employed in military and aerospace applications where reliability and durability are critical, and where space is limited and lighter weight is desirable.
- Medical devices: 2.2-5 low-PIM connectors are used in medical devices such as MRI machines and other imaging equipment, where signal quality and reliability are essential.
- Industrial automation: 2.2-5 low-PIM connectors are utilized in industrial automation systems such as robotics, where small size and weight are important for space-constrained environments.
- Test and measurement: 2.2-5 low-PIM connectors are used in test and measurement applications, such as network analyzers and spectrum analyzers. These connectors provide high accuracy and low PIM, which is essential for precise measurements in wireless systems.
Power Surge Disruptions
Like all systems of electronic connectivity, wireless networks are susceptible to damage from power surges caused by lightning strikes and other sources of power transients. The disruption, which can be extremely costly, can come in three forms. Physical damage to electronic equipment can occur when lightning strikes an antenna. Another disruption is induced voltage, when a voltage surge enters the wireless network and short circuits the network equipment. Third, power surges can generate EMI/RFI.This electromagnetic interference (EMI) and radio frequency interference (RFI) cause communication problems such as poor signal quality, reduced transmission range, and errors in data transmission.
SPDs to the Rescue
To prevent lightning strikes and power surges from damaging wireless networks, it is important to install surge protection devices (SPDs) such as lightning arrestors and surge protectors at the antenna and power/data connection points. SPDs typically work by providing a low-impedance path to ground for the surge current, effectively shunting the excess energy away from the equipment.
PolyPhaser’s 2.2-5 Low-PIM SPD
PolyPhaser’s wide selection of RF surge protectors includes an SPD with 2.2-5 low-PIM RF connectors that can be used in the applications listed above. Our Model QWP-22M22F-ER is an extended-range RF protector that will protect your equipment from electromagnetic pulse (EMP) or power surges that are commonly caused by lightning or other strong electrical changes.
Features:
- Extended range broadband performance from 555 MHz to 4.5 GHz
- Protection up to a Max. power of 300 watts
- Quarter-wave stub technology (see below)
- DC block topology
- Repetitive-strike protection
- System-level low PIM rating of 160 dBc
- Male input, female output
Applications Include:
- CBRS networks
- Cellular networks
- Distributed antenna systems (DAS)
- Emergency response systems
- Public safety systems
Quarter-Wave Stubs Are Fast and Tough
PolyPhaser’s Model QWP-22M22F-ER incorporates quarter-wave stub technology, which stops surges faster than other types of surge protectors, requires no maintenance and can withstand repeated surges without being damaged.
A quarter-wave stub SPD is a type of coaxial cable that is cut to a specific length, typically one-quarter of the wavelength of the frequency being used. The quarter-wave stub works by reflecting any surge voltage that is present back towards the source, preventing it from reaching the equipment. When the surge voltage reaches the quarter-wave stub, it encounters an impedance mismatch that causes the voltage to reflect back down the cable towards the source.
PolyPhaser’s 2.2-5 low-PIM quarter-wave stub surge protector and the rest of our extended-range surge protectors, as well as our entire line of RF SPDs, are in-stock and available for same-day shipping. For more information, contact us at +1 208 635 6400.
FAQs (Frequently Asked Questions)
Q1: What is passive intermodulation (PIM)?
A: Passive intermodulation is unwanted signal distortion created when multiple RF signals mix in passive components such as connectors, cables, or antennas. The resulting interference can fall into receive bands and degrade system performance.
Q2: Why are connectors a major source of PIM?
A: Connectors contain metal-to-metal contact points where nonlinearities can occur due to surface roughness, oxidation, corrosion, loose connections, or mixed metals, making them common contributors to PIM.
Q3: What makes 2.2-5 connectors low-PIM?
A: 2.2-5 low-PIM connectors are manufactured using high-quality materials, smooth contact surfaces, tight mechanical tolerances, and stable threaded coupling to minimize nonlinear junctions that generate PIM.
Q4: Where are 2.2-5 low-PIM connectors commonly used?
A: They are widely used in wireless base stations, DAS systems, small cells, antennas, RF jumpers, and low-PIM surge protection devices.
