Tester Locates PIM At Cell Site

Jan. 19, 2011
This transportable test unit works with a handheld spectrum or signal analyzer to quickly locate passive intermodulation sources in and around a cellular base station in the PCS and AWS frequency bands.

Intermodulation distortion (imd) can wreak havoc on digital cellular communications systems, resulting in increased errors and degraded bit-error-rate (BER) performance. This unwanted mixing of multiple signal tones is usually associated with active components, but can just as easily originate from passive components, in the form of passive intermodulation (PIM). Finding PIM is not a simple task, but Anritsu has made the job of in-field "PIM trackers" a bit easier with the introduction of the model MW8219A PIM Master. The transportable instrument generates high-power test tones in the 1900- and 2100-MHZ Personal Communications Services (PCs) and Advanced Wireless Services (AWS) cellular bands and is designed to work with one of Anritsu's site master, spectrum master, Cell master, or Bts master portable signal analyzers to read the amplitude of and determine the distance to third-, fifth-, and seventh- order intermodulation products.

The MW8219A PIM Master is packed into an easily transportable case (see figure) and works with different Anritsu handheld signal analyzers and specialized software to analyze the third-, fifth-, and seventh-order intermodulation products in a user-selectable receive band. The test source and analyzer are used to implement a patent-pending measurement technique called a distance-to- PIM (DTP) measurement, a PIMseeking version of the company's distance-to-fault (DTF) capability first included in Anritsu's sitemaster handheld analyzer in 1997.

The DTP capability shows the distance and magnitude of PIM sources that lie both within the cellular system and in the surrounding environment, such as from a nearby rusty structure or a closely located second cellular site. It not only saves a technician's time during on-site troubleshooting, but DTP test results can be used as part of a historical database of a cell site's performance by storing and later recalling measurement results for comparison, revealing whether the performance of the system or its components is deteriorating over time.

The PIM master provides different levels of two-tone test power for flexibility: 2 x 20 W (+43 dBm), 2 x 30 W (+45 dBm), and 2 x 40 W (+46 dBm). The test signals are provided by a type n female connector. Because problems due to PIM can be intermittent when tested with two 20-W tones, the PIM master offers the two higher-power test tone levels that may force otherwise intermittent problems to become more apparent, including problems caused by moisture and corrosion of connectors and rust on antennas.

A PIM master test system, with appropriate site master, spectrum master, Cell master, or Bts master, transmits two-tone signals at PCs frequencies from 1930 to 1990 MHZ and aWs frequencies from 2110 to 2155 MHZ and receives signals for analysis at aWs frequencies from 1710 to 1755 MHZ and PCs frequencies from 1859 to 1910 MHZ. Measurements can be performed with two fixed tones or as swept measurements, with results stored within the analyzer. The PIM master provides a 10-MHZ reference signal at a BNC connector. The MW8219A PIM master is 12 x 17 x 20 in. (300 x 425 x 500 mm) and weighs 63 lbs. (28.6 kg). JB

Anritsu Co., 490 Jarvis Dr., Morgan Hill, CA 95037-2809; (408) 778-2000, FAX: (408) 776- 1744, www.us.anritsu.com.

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