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Multiport VNAs Grapple with Complex Test Scenarios

This new line of multiport vector network analyzers makes it possible to perform a large number of simultaneous measurements.

As one would expect, Rohde & Schwarz came to IMS 2019 in full force, showcasing various test-and-measurement solutions for all to see. One solution that grabbed the spotlight was its new family of ZNBT multiport vector network analyzers (VNAs), which provides users with as many as 24 test ports (see figure).

The architecture of the ZNBT VNAs allows for various device-under-test (DUT) ports to be stimulated simultaneously, making it possible for users to test multiple DUT paths or multiple DUTs all at once. Furthermore, since the architecture is geared for parallel signal and data acquisition, the instruments can not only measure S-parameters, but also perform phase-synchronous measurements.


At IMS 2019, Rohde & Schwarz displayed this ZNBT40 multiport VNA, which covers a frequency range of 100 kHz to 40 GHz.

Rohde & Schwarz offers four versions of the ZNBT VNAs: the ZNBT8, ZNBT20, ZNBT26, and ZNBT40. The ZNBT8 model has a measurement frequency range of 9 kHz to 8.5 GHz, while the ZNBT20’s frequency range covers 100 kHz to 20 GHz. The ZNBT26 has a measurement frequency range extending from 100 kHz to 26.5 GHz. And the ZNBT40 offers the highest frequency performance—it covers a 100-kHz to 40-GHz range.

The ZNBT8 base unit comes with 4 ports, but it’s possible to upgrade to 8, 12, 16, 20, or 24 ports. The ZNBT20, ZNBT26, and ZNBT40 base units are each built with 8 ports, but customers have the option to upgrade to 12, 16, 20, or 24 ports. The ZNBT8 is built with type-N test port connectors, while 3.5-mm test port connectors are found on the ZNBT20. The ZNBT26 and ZNBT40 both come with 2.92-mm test port connectors.

When set to 201 measurement points with a 900-MHz center frequency and a 200-MHz span, the ZNBT8’s sweep time is less than 2.5 ms (1-MHz measurement bandwidth). Under the same conditions, the sweep time of the ZNBT20 is less than 3 ms. Both the ZNBT26 and ZNBT40 achieve sweep speeds of under 3.5 ms with the same settings applied.

Dynamic range is another key aspect of the ZNBT VNAs. Specifically, the ZNBT8 can achieve a typical dynamic range as high as 140 dB with a 10-Hz measurement bandwidth. In addition, Rohde & Schwarz offers an option to extend the dynamic range (145 dB typical) to help support high-blocking-filter measurements.

In terms of the power range of the test port outputs, the ZNBT8 has a specified range of −55 dBm to either +8, +10, or +13 dBm, depending on the frequency band. The company also offers an option to extend its power range down to −85 dBm. The same option exists for the other three models.

Rohde & Schwarz maintains that the ZNBT VNAs are easy to integrate into automated test systems, such as phased-array antenna measurement scenarios.

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