Millimeter-wave frequencies offer a "new frontier" for communications. Realizing the overcrowding taking place at RF and microwave frequencies, the United States Federal Communications Commission (FCC) and other regulatory agencies have looked to higher frequencies as a way to add bandwidth and services. All that is missing is low-cost millimeter-wave components to assemble affordable communications infrastructure and user devices to take advantage of the "wide-open" bandwidth.
Millimeter-wave frequencies are so named for the wavelengths of the signals, ranging from about 10 to 1 mm and covering frequencies from about 30 to 300 GHz. They have traditionally seen use in military radar and missile seeker and guidance systems. But in 2003, the United States FCC, seeking to open millimeter-wave frequencies to commercial communications use, adopted a Report and Order establishing service rules or non-Federal development of certain portions of the millimeter-wave spectrum, notably 71 to 76 GHz, 81 to 86 GHz, 91 to 94 GHz, and 94.1 to 95.0 GHz. Frequency bands were made available in 1.25-GHz blocks on a non-exclusive basis. Coordination of the spectrum use would be performed by the National Telecommunications and Information Administration (NTIA).
As a followup, the Wireless Communications Association International (WCA) filed a Petition for the FCC to reconsider certain aspects of the Report and Order but only for the 70- and 80-GHz bands. Among these considerations, all new 70- and 80-GHz users would have to verify in advance that their systems would not cause harmful interference to any existing link and meet a series of requirements related to antenna and power specifications.
Given the tremendous crowding of bandwidth taking place at lower frequencies (consider the number of communications and heating applications in the 2.4-GHz band alone), the bandwidth represented by millimeter-wave links is attractive for secure data links, video links, backhaul connections between cellular communications stations, and more. One of the companies taking note of the available bandwidth was GigaBeam (www.gigabeam.com), driven by the shared vision of Lou Slaughter (CEO and chairman) and long-time microwave-industry visionary Doug Lockie (CTO and president). The company's WiFiber Wireless Fiber product lines employ millimeter-wave transceivers capable of providing high-speed (to 10 Gb/s) and reliable communications links at distances to 1 mile for secure campus-to-campus and building-to-building wireless connections.
Endwave (www.endwave.com) produces compact E-band transceivers at frequencies from 71 through 86 GHz with receiver noise figures to3 dB and transmit output power to 2 W. The company's designs are available with options for waveguide and coaxial connections as well as with hermetic packaging.
The GigaLink Series of millimeter-wave transceivers from Proxim Wireless (www.proxim.com) operate at unlicensed frequencies from 57 to 64 GHz and in the licensed band from 71 to 76 GHz. Designed as a high-speed alternative to fiber-optic links, the E-band transceivers feature an integrated parabolic antenna with 44-dBi gain, Gigabit Ethernet data rate of 1.25 Gb/s, and extended range in excess of 8 km. Similarly, the WiFiber Wireless Fiber solution from GigaBeam Corp. (www.gigabeam.com) is a millimeter-wave alternative to fiber using the FCC-approved 71- to 76-GHz, 81- to 86-GHz, and 92- to 95-GHz bands.
Of course, establishing short-range millimeter-wave links that can be competitive with fiber optics and other technologies requires cost-effective components, a long-time stumbling block for widespread use of millimeter-wave technology. Bringing the technology to "the masses" requires a combination of intelligent design and skillful machining processes. Millitech (www.millitech.com), for example, carries those capabilities in two different divisions to provide both standard and custom components from 18 to 300 GHz. The firm produces a variety of building-block components, which can be used for subsystems or complete systems, including antennas, oscillators, amplifiers, control components and various passive waveguide components. Balanced mixers can be specified from 18 to 100 GHz while subharmonic mixers are available from 50 to 200 GHz. Cassegrain reflector antennas range from 18 to 220 GHz, while standard feed horns are available from 18 to 220 GHz. Gunn oscillators can be ordered with electrical or mechanical tuning from 26.5 to 100 GHz, while LNAs provide high gain from 18 to 110 GHz.
Spacek Labs (www.spaceklabs.com) provides most of the building-block components needed to assemble a millimeter-wave system, including the new model AW-8X, an eight-times multiplier for generating W-band signals. The multiplier accepts input signals from 9.35 to 13.75 GHz at levels from +5 to +10 dBm and provides output signals from 75 to 110 GHz at typically +3 dBm output power. Spurious levels are typically controlled to 20 dBc.
Merrimac Industries (www.merrimacind.com) has applied its innovative Multi-Mix multilayer circuit technology to the fabrication of high-performance filters and other components for millimeter-wave applications. For example, the firm's model FBMM-42.0G Multi-Mix bandpass filter offers a 3-GHz passband centered at 42 GHz with typical passband insertion loss of 3.5 dB. The typical input/output return loss is 15 dB, while minimum rejection is 60 dB at 38.5 GHz and 30 dB at 46 GHz. In spite of measuring just 0.620 3 0.296 3 0.020 in. and weighing just 0.2 g, the filter handles power levels to typically 1 W.
Channel Microwave (www.channelmicrowave.com) developed the model WR28 three-way power divider for use from 34 to 36 GHz. Designed to handle 10 W average power and 500-W peak power in military systems, it exhibits better than 60 dB reverse isolation. To minimize lost energy due to heating effects, insertion loss is help to typically 1 dB.
Farran Technology Ltd. (www.farran.com) offers the PLO Series of phase-locked Gunn oscillators for generating signals from 60 to 325 GHz. The sources operate with an external 100-MHz reference for stability and provide as much as 50 mW output power from 60 to 90 GHz and 2 mW output power from 250 to 325 GHz.
Insight Product Co. (www.insight-product.com) offers a broad line of millimeter-wave and submillimeter-wave components, including amplifiers with as much as 30 W output power at frequencies through 140 GHz, monolithic balanced mixers for applications through 178 GHz, and solid-state and tube-based signal sources through 370 GHz. The firm's recently developed line of Terahertz frequency synthesizers includes frequency coverage from 120 to 180 GHz with more than 30 mW output power and options for frequency modulation (FM) and amplitude modulation (AM).