Technology for RF/microwave power dividers/ combiners has not changed much in recent years, although customer requirements have forced the manufacturers of these passive components to seek smaller package outlines while still handling respectable power levels. That classic tradeoff of size versus power- handling capabilities impacts most passive components and has guided the design of many recent high-frequency power combiners/dividers.
Microwave power dividers and combiners come in many forms, from simple 3-dB splitters that produce two equal-amplitude output signals to more elaborate dividing/combining networks that feed phased-array antennas and other complex applications. While some are optimized for use as dividers or combiners, many can be used as both. Power dividers are characterized by many of the specifications that apply to passive microwave components, including insertion loss, VSWR, and power-handling capability. Isolation between ports is also important as are the amount of amplitude and phase unbalance in divided channels.
For military applications, power dividers must not only provide broadband frequency coverage, but must also offer robust power-handling capabilities. Narda Microwave, an L-3 Communications company, recently unveiled its model 3306-2 two-way power divider for military applications. With a bandwidth of 6 to 18 GHz, the power divider can handle as much as 100 W CW input power while exhibiting low VSWR of 1.50:1. It measures just 1.25 x 1.5 x 1.2 in. without its Type N female connectors. The power divider exhibits insertion loss of less than 4.2 dB from 6 to 10 GHz and 4.5 dB from 10 to 18 GHz. The isolation between ports is at least 15 dB across the full bandwidth, with input and output VSWR of less than 1.80:1 at all ports. Amplitude and phase between ports are well controlled in this design, with specified amplitude unbalance of 0.5 dB or less and phase unbalance of 12 deg. or less.
Pulsar Microwave offers a power combiner, model PP2-18-450/22N, that can provide 500 W output power at its sum port. It operates from 2 to 200 MHz with only 0.6 dB insertion loss and maximum VSWR of 1.30:1. Isolation between ports is 20 dB while the amplitude and phase unbalance are 0.3 dB and 5 deg., respectively.
Anatech Microwave has developed a series of 32-way power dividers for wireless communications applications, including the model AM250PD1309, which handles inputs to 1 W from 1 to 500 MHz. It has maximum insertion loss of 3 dB and isolation of 18 dB, with maximum VSWR of 1.80:1. Maximum amplitude and phase unbalance are 0.8 dB and 15 deg., respectively.
For designers seeking variety, Mini- Circuits sells the model K1-QCN+ Designer's Kit with two units each of 10 different power divider/combiner models. The group of components covers 220 to 4500 MHz with 15-W input power rating when used as splitters. They offer insertion loss as low as 0.4 dB and isolation to 32 dB in ceramic packages measuring just 0.12 x 0.60 x 0.35 in. In contrast to power dividers/combiners, microwave couplers separate the level of input power into at least two different output levels, a main path and a coupled path. The coupled path may be as much as 20 dB or more less than that of the input level. As an example, Anaren recently added several couplers to its Xinger product line, with models XC0600-B- 03P, XC4300-E-03P, and XC4300-A- 20P providing frequency coverage of 225 to 1000 MHz, 2500 to 6000 MHz, and 2500 to 6000 MHz, respectively, with power-handling capabilities of 75, 100, and 100 W, respectively.