Millimeter wave frequencies were traditionally dedicated to military applications with some commercial use for point-to-point microwave links. Sub-octave bandwidth waveguide was the preferred transmission line as millimeter wave-capable coax cable and connectors were not available.
All that has changed in the past decade with technology improvements in semiconductors, components, cables, and connectors. It is now possible to use millimeter wave frequencies for commercial/consumer electronics.
There are a number of market segments preparing for enhanced use of millimeter wave frequencies, including but not limited to 5G, automotive radar, 60 GHz Wi-Fi (WiGig or 802.11ad), point-to-point communication links, and security and defense.
5G. The demand for mobile data spectrum keeps growing with the increasing number of smart phone users, and the fact that users are finding new applications that require very high data rates.
Automotive radar. A cornerstone in the ability to achieve self-driving vehicles is the ability to detect and avoid obstacles. Millimeter wave radar technology is advancing rapidly to support the array of sensors needed. Automotive radar frequency bands are 24, 77, and 79 GHz.
60 GHz Wi-Fi (WiGig). Consumer Wi-Fi applications have expanded beyond what is available from 802.11ac devices. The designation 802.11ad is an extension of the IEEE’s popular 802.11 family of wireless local-area network (LAN) standards. The 58 to 64 GHz spectrum has long been available for unlicensed services, and was recently expanded up to 71 GHz (FCC Part 15).
Challenges of the Millimeter Wave Market
The advancement of millimeter wave technology is opening the door for numerous new applications, but higher-frequency transmission comes with its own challenges, like higher propagation loss and issues with measurement repeatability.
Propagation loss and connection repeatability are key challenges seen today.
Overcoming Millimeter Wave Challenges
Reducing the number of connections. Reducing the number of connections in a test system reduces the number of points of failure (measurement error) due to dust/dirt damaging the return loss of a connection. It also minimizes the chance for imperfections to cause test system impedance variation from 50 ohms. Each connection in the system (male to female connector pair) will add uncertainty. Millimeter wave connectors and cables must be handled carefully to ensure accurate measurements.
Measure as close to DUT as possible. In order to properly characterize and remove the impact of the cables, a network analyzer can be used to characterize each cable to know the net cable loss at each measurement frequency. This, however, can be complicated, time-consuming, and costly. The only way to simply and completely remove the impact of cables is to remove the cables altogether and take measurements directly at the DUT
Anritsu Is a Leader in Millimeter Wave Testing
Anritsu has been a pioneer in millimeter wave testing with development of the 40 GHz K connector in 1983, 70 GHz V connector in 1989, and 110 GHz W connector in 1997.
Anritsu is also a leader in millimeter wave vector network analysis with the MS4640B Series VectorStar and MS46522B-082 ShockLine network analyzers.
The MS2760A has an ultraportable form factor. It is about the size of a smartphone, which makes it small and light enough to be directly connected to many devices under test. It is even equipped with mounting holes to be attached to a bracket for direct connection to a semiconductor wafer probe. This eliminates the cable and all the uncertainty that comes with it, significantly improving system accuracy and repeatability.