Circulators/Isolators Serve UMTS Applications

Oct. 1, 2003
These compact circulators and isolators are designed for high isolation, low insertion loss, and generous power-handling capabilities for UMTS base-station designs.

Circulators and isolators are essential components in many communications systems, since they can be used to direct RF/microwave signals between ports as well as provide high isolation. These inherently narrow-band components are designed for specific applications, such as the new line of drop-in and surface-mount circulators and isolators in the NE3101 and NE1101 lines from Temex for use in Universal Mobile Telecommunications System (UMTS) applications from 2080 to 2200 MHz. The components feature low intermodulation distortion (IMD) and generous power-handling capabilities.

The high data rates (2 MB/s) expected of UMTS translates into demanding specifications for communications system components such as circulators and isolators. For example, typical UMTS third-order IMD requirements are on the order of −80 to −90 dBc when measured with two test tones at about 28 W (+44.5 dBm) each.

The new drop-in circulators and isolators from Temex consist of a stripline center conductor sandwiched between two ferrite disks. The disks are placed between ground planes and magnetically biased by permanent magnets. Using electromagnetic (EM) simulation and analysis computer-aided-engineering (CAE) software, the structure is optimized for the best balance of isolation, loss, and IMD performance in the UMTS band from 2080 to 2200 MHz.

The EM simulations are backed by precision measurements using dual test sources to generate a two-tone test signal for IMD evaluations. The performance of each device under test (DUT) is checked with a spectrum analyzer to gauge the amplitude differences between the CW test tone and the IMD tone. The company's test system achieves a spurious-free dynamic range of better than −120 dBc with two test tones of +44.5 dBm (28 W) each and a through-path calibration standard in place of the DUT, and IMD products below −90 dBc have been measured with the system.

The new circulator/isolator lines feature five models operating at frequencies from 2080 to 2200 MHz (see table). These include circulator models NE3101-100 and NE3101-200 for use from 2080 to 2200 MHz, isolator model NE1101-300 for use from 2110 to 2170 MHz, attenuator model NE1101-200 for use from 2080 to 2200 MHz, and load model NE1101-100 for use from 2080 to 2200 MHz. All derive from the basic ferrite circulator architecture, with all but the model NE1101-300 capable of handling as much as 200 W CW forward power and at least 100 W CW reverse power. The other unit, drop-in isolator model NE1101-300, is designed for low-power applications where the reverse power does not exceed 1 W.

The models NE3101-100 and NE3101-200 circulators offer better than 21 dB isolation and less than 0.3 dB insertion loss from 2080 to 2200 MHz, each with VSWR of 1.20:1. They are rated for 100 W CW power in the forward and reverse directions. The drop-in model NE3101-100 exhibits −70 dBc IMD performance while the surface-mount model NE3101-200 circulator achieves outstanding IMD performance of better than −85 dBc.

The NE1101-300 low-power isolator handles 10 W of forward power and 1 W of reverse power, with better than 23 dB isolation and less than 0.3 dB insertion loss from 2110 to 2170 MHz. It has VSWR of 1.15:1 with IMD performance of better than −70 dBc.

The low-IMD model NE1101-100 drop-in isolator is essentially a circulator terminated with a 50-Ω load. It handles 200 W forward power and 100 W reverse power, with at least 21 dB isolation (attenuation) and less than 0.3 dB insertion loss from 2080 to 2200 MHz. It achieves better than −85 dBc IMD performance with VSWR of 1.20:1 in a drop-in package. Similarly, the NE1101-200 is also a drop-in isolator, but with the terminated port connected to a 20- or 30-dB attenuator for reverse power detection. The NE1101-200 drops IMD levels below −85 dBc while handling 200 W forward power and 100 W reverse power. Like the NE1101-100, it achieves better than 21 dB isolation with less than 0.3 dB insertion loss and 1.20:1 VSWR from 2080 to 2200 MHz.

The NE3101-100 circulator and the NE1101-300 isolator are each supplied in a 19.05 × 19.05-mm drop-in package while the NE3101-200 circulator is provided in a circular package with 19.05-mm diameter. The NE1101-100 and NE1101-200 isolators are housed in packages measuring 19.05 × 25.4 mm. Temex Electronics, Inc., 17235 N. 75th Ave., Suite G-100, Glendale, AZ 85308; (623) 780-1995, FAX: (623) 780-2431, e-mail: [email protected], Internet:

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