TELECOM PASSIVE INTERMODULATION (PIM) TESTING
PIM is a growing issue for cellular network operators. PIM issues may occur as existing equipment ages, when co-locating new carriers, or when installing new equipment. PIM is a particular issue when overlaying (diplexing) new carriers into old antenna runs. PIM can create interference that will reduce a cell’s receive sensitivity or even block calls. This interference can affect both the cell that creates it, as well as other nearby receivers. PIM is created by high transmitter power so on-site PIM testing needs to be done at or above the original transmitter power levels to make sure that the test reveals any PIM issues. PIM is a serious issue for cellular operators wanting to maximize their network’s reliability, data rate, capacity, and return on investment. It is worth noting that PIM testing does not replace impedance-based line sweeps, rather, it complements line sweeping, which is now more important than ever. High-speed digital data communications make PIM testing critical. As cell usage and throughput grows, the peak power produced by the new digital modulations increases dramatically, contributing heavily to PIM problems. On-site experiments have shown significant decreases in download speeds linked to slight increases in PIM. Drive tests have revealed an approximate 18% drop in download speed when residual PIM level was increased from –125 dBm to –105 dBm. The latter figure is hardly considered poor.
The PIM test is a measure of system linearity while a Return Loss measurement is concerned with impedance changes. It is important to remember that they are two independent tests, consisting of mostly unrelated parameters that are testing opposite performance conditions within a cellular system. It is possible to have a PIM test pass while Return Loss fails, or PIM fail while Return Loss passes. Essentially, PIM testing will not find high Insertion Loss and Return Loss will not find high PIM. Line sweeps and PIM testing are both important.
Some cable faults show up best with a PIM test. For example, if an antenna feed line has a connector with metal chips floating around inside, it is highly likely that it will fail a PIM test while the line sweep passes. The antenna run most certainly possesses nearly ideal impedance characteristics, but the presence of metal flakes bouncing around will cause the PIM test to fail. It is also an indication that the connector was not fitted correctly.
Another possible cause of PIM test failures is braided RF cables. These cables will test perfectly in a Return Loss or VSWR test, but generally possess only average PIM performance. The braided outer conductor can act like hundreds of loose connections that behave poorly when tested for PIM, particularly as they age. For permanent installations, braided cables are not recommended. Low PIM precision test cables are available commercially and they perform well, although they are very expensive. Some cable faults show up best in a Return Loss or VSWR test. A good example is a dented or pinched main feeder cable, which will have an impedance mismatch at the point of the damage, but may still be linear. Return loss testing will quickly spot this sort of damage, although PIM testing cannot. With the rollout of spread-spectrum modulation techniques, such as W-CDMA, and OFDM technologies like LTE and WiMAX, it has become essential to test both PIM and impedance parameters both correctly and accurately.
PIM lowers the reliability, capacity and data rate of cellular systems. It does this by limiting the receive sensitivity. In the past, RF engineers could select channel frequencies that would not produce PIM in the desired receive bands. However, as cellular usage grows, the licensed spectrum has become crowded. Engineers must often select less desirable RF carrier frequencies and accept potential PIM issues. Compounding this problem, existing antenna systems and infrastructure are aging, making any PIM that does occur stronger.
When PIM products fall within the receive band of a cell site radio, they make the receiver less sensitive to weak signals that limits receive coverage. This increases the bit-error-rate (BER)and creates more dropped calls. If the connection is for data, interference from PIM creates more error protection bits and resends, which causes a lower overall data rate. In some cases, PIM can even cause receiver blocking, shutting down the sector. Signs of PIM problems include receive-noise-floor-diversity-imbalance and high noise floors. Other signs include shorter average call duration, higher dropped call rates, lower data rates, and lower call volume.
Unrepaired PIM problems can cause the base transceiver station (BTS) to assume a certain Rx noise level exists during calibration periods, causing gross Tx power and Rx gain figures to be utilized. These figures carry over into heavy traffic periods and then the BTS exhibits poor statistical performance. Any increase in the noise floor at the receiver input causes a decrease in the dynamic range of that receiver. If the Rx sensitivity is –107 dBm, but the real noise floor is –97 dBm, the call or connection will need to be terminated or handed off to another site/sector 10 dB earlier than the system would normally be designed to do. If 1 dB in Rx level was equal to 0.5 miles, this connection would hand off 5 miles early, in terms of distance. Sectors that do not always have a lot of margin between sites will end up with dead zones where the call will be lost. A PIM test and rectification of faults will restore the original performance that is required.
Many different components in, and near, an antenna system can cause PIM. The common assumption in the industry is that antenna assemblies need to be tested. Clearly, PIM can be an issue with cellular antenna systems and some testing is necessary. As a guideline, PIM issues most often show up at initial installation, after aging or when adding new carriers to older antenna systems. PIM testing is the only sure way to understand how an antenna system responds to multiple high-powered RF signals. PIM testing has been a very common test performed by almost all major equipment manufacturers over the past 10+ years. It has not been common until just recently to test onsite, and this is driven by advancements in cellular communications technology. Original Equipment Manufacturers (OEMs) such as Nokia and Alcatel-Lucent, for example, have utilized PIM testing for years, at 2 x 46 dBm, as a quality tool. All companies supplying products that are installed within a base station must comply with strict performance figures relating to PIM performance.
Lack of linearity can limit the receive sensitivity of a cellular system. This limits the reliability, data rate, capacity, coverage, and return on investment of the system. The PIM test is an excellent indicator of linearity and construction quality. PIM comes from two or more strong RF signals mixing in a nonlinear device. These nonlinear devices, or junctions, occur in improperly tightened, damaged, or corroded connectors or in damaged antennas. Rusty components, such as mounts and bolts, are also suspect when hunting for sources of PIM. Many common frequency combinations can produce PIM in a cells receive band. Signals in the cell’s receive band will raise the receive noise floor, increase the bit error rate, and shrink the reception area for cellular communications. Avoiding PIM starts with frequency assignments that put potential PIM products outside of receive bands. However, increasing capacity, new services, and aging infrastructure are all working against this strategy, making PIM testing more important every day. It is apparent that most onsite PIM issues that affect service are derived from the sidebands of internally generated interference, not the calculated frequencies themselves. Proper care and maintenance of connectors is essential to keeping PIM low. Inspection and cleaning is a central part of good performance. Proper torque is also important, as this keeps the center connector from damage. PIM testing is becoming more critical as cellular systems age and the carrier count is increased. A test that was not as important when cellular systems were lightly loaded is becoming a critical part of modern cellular maintenance. A cell site constructed with PIM in mind will cost less to maintain over time. This same site will show cleaner performance than similar sites that were not PIM tested.
Available PIM Machines in Stock
Analyzer Model Frequency Option
Kaelus-IQA-0901C EGSM 900Mhz
Kaelus-IQA-2101C UMTS 2100Mhz
Anritsu-MW82119A-0900 EGSM 900Mhz
Anritsu-MW82119A-0180 DCS 1800 MHz
Anritsu-MW82119A-0210 UMTS 2100Mhz
A. Kaelus-IQA-0901C PIM Analyzer .
The iQA-0901C from Kaelus is a PIM Analyzer with TX Frequeny 925 to 960 MHz, RX Frequency 880 to 915 MHz, Transmitter Freq. Accuracy ± 5ppm (max), aging ± 1ppm (max) after first year, Transmitter Power Accuracy ± 0.5dB (max), PIM Sensitivity <-125dBm/-168dBc @ 2x 43dBm carriers.
- Part Number : iQA-0901C
- Manufacturer : Kaelus
- Description : iQA Portable PIM Analyzer
- Type : Portable
- TX Frequeny : 925 to 960 MHz
- RX Frequency : 880 to 915 MHz
- Transmitter Freq. Accuracy : ± 5ppm (max), aging ± 1ppm (max) after first year
- Transmitter Power Accuracy : ± 0.5dB (max)
- PIM Sensitivity : <-125dBm/-168dBc @ 2x 43dBm carriers
- Residual PIM : < -115dBm/-158dBc max (<-125dBm/-168dBc typ) (x2 @ 20W)
- Measurement Method : Reverse (reflected) PIM, 3rd, 5th, 7th, 9th and 11th order
- Measurements : PIM over Frequency
- Mechanical Shock : 40G shock rating
- AC Power : 115-230V, 50/60Hz AC
- Operating Temperature : -10°C to +40°C
- Power Consumption : 650 Watts
- Receiver Measurement Range : -50dBm to -128dBm
- Receiver Noise Floor : < -128dBm
- Dimension : 500 x 457 x 305mm
- Display : 8.4in (213mm) touch screen display
- Weight : 22.7 kg.
- Cooling : Forced Air
- Features : Rugged and reliable designed with tower climbers in mind - Fully configurable frequencies, powers and IM products - iPad Mini included for remote control of device - Simple to operate touch screen interface - Extensive reporting capabilities - Spectrum
- Humidity : 5% to 95% RH non-condensing
B. Kaelus-IQA-2101C PIM Analyzer .
The Kaelus IQA-2101C PIM Analyzer operates at a transmission and receiving band frequency range of approximately 2000-2100MHz and possesses RTF-2000A capability. The IQA Passive Intermodulation (PIM) analyzer is a feature-rich, high power PIM test solution which fulfills the IEC 62037standard for passive intermodulation, its innovative design increasing safety and efficiency. This field-proven analyzer enables network operators to improve site performance by finding and eliminating sources of passive intermodulation at the cell site. The design includes an integrated panel PC with intuitive touch screen interface for performing tests and generating site reports. The Kaelus IQA-2101C PIM Analyzer performs immediate and accurate Distance-to-PIM tests, informing you of the distance and magnitude of all PM sources simultaneously, both within the antenna system and beyond the antenna itself. With the growing amount of systems which utilize duplex transmissions paired with collocated transmitters and receivers, the Kaelus IQA-2101C PIM Test Set is an essential tool to discover distortions to RF transmissions.
- Rugged, reliable construction suitable for field use
- Integrated polycarbonate transit case
- Range to Fault (RTF) enabled
- Fully configurable frequencies, powers and IM products
- Simple to operate touch screen interface
- Spectrum monitor, frequency sweep and time trace modes
- TX RANGE: 2110-2170 MHz
- RX RANGE (PIM): 1920-2080 MHz
- Measurement method: Reverse (reflected) PIM, 3rd, 5th, 7th and 9th order
- Residual PIM: < -115dBm/-158dBc max (<-125dBm/-168dBc typ.)
- User interface ports: 2x USB, x1 LAN 1x RF output (7-16 DIN female)
- Display: 8.4in (213mm) touch screen display
- Frequency increment: 50 kHz
- Frequency accuracy: ± 5ppm (max), aging ± 1ppm (max) after first year
- Power per tone (adjustable): 2x 2 to 20W (+33 to +43dBm)
- Power accuracy (per tone): ± 0.5dB (max)
- Measurement noise floor: < -128dBm
- Measurement range: -50dBm to -128dBm
- Mains power: 115-230V, 50/60Hz AC
- Power consumption: 650W
- Dimensions: 19 x 18 x 12in (500 x 457 x 305mm)
- Weight: < 50lbs (22.7kg)
- Cooling: Forced air
- Operating temperature range: -10°C to +40°C
- Storage temperature range: -20°C to +60°C
- Ingress protection (IP): IP20 (with lid open) IP21 (with lid closed)
- Relative humidity: 5% to 95% RH non-condensing
- Mechanical shock: 40G shock rating
C. Anritsu-MW82119A .
Anritsu MW82119A is the first battery-operated high power Passive Intermodulation (PIM) testing solution for the major wireless standards in use around the world. PIM is a form of interference generated by passive components that are normally thought of as linear such as connectors, cable assemblies, filters and antennas. However, when subject to high RF power levels found in cellular systems, these devices can generate spurious signals that increase the receiver noise floor and reduce site performance.
Option 0900 = E-GSM Tx1: 925 MHz to 937.5 MHz, Tx2: 951.5 MHz to 960 MHz, Rx: 880 MHz to 915 MHz
Option 0180 = DCS Tx1: 1805 MHz to 1837 MHz, Tx2: 1857.5 MHz to 1880 MHz, Rx: 1710 MHz to 1785 MHz
Option 0210 = UMTS 2100 Tx1: 2110 MHz to 2112.5 MHz, Tx2: 2130 MHz to 2170 MHz RxLower: 1920 MHz to 1980 MHz, RxUpper: 2050 MHz to 2090 MHz
- Small Size: 350 mm x 314 mm x 152 mm (13.8 in x 12.4 in x 6.0 in)
- Lightweight: 9.0 kg to 12.2 kg (20 lb. to 27 lb.) depending on frequency band
- Battery Operated: 12V Li-Ion battery
- 25 dBm (0.3 Watt) to 46 dBm (40 Watt) output power
Trignotek Systems Private Limited is passionate about helping you acquire the right equipment when you need it. Our rental solutions are the perfect way to use equipment flexibly without the high cost of ownership and equipment maintenance. You benefit from a huge inventory, immediately available and delivered next day. We are the main source to supply PIM Testers and perform PIM Testing services. We are well equipped with various cutting edge PIM testing and analysing machines which are listed below to cope up with any kind of requirement from our customers. Our PIM Testing engineers are well trained and experienced to deliver the PIM projects in the most efficient manner.