Power dividers provide a critical signal-processing function in military electronic systems. They allow a single input signal to be subdivided into two or more output signals, so that detailed analysis can be performed, for example, on captured radar or intelligence signals. One of the better-known suppliers of broadband RF/microwave power dividers is Electromagnetic Technologies Industries (ETI) which supplies coaxial units with division ratios to 16 at frequencies through 65 GHz.
The firm's stripline power dividers (that can often be used as power combiners in reverse) feature input and output ports precisely matched to a characteristic system impedance of 50 Ohms. A close impedance match of both ports ensures high isolation between input and output ports as well as between adjacent output ports. Because of the division of power through a divider, coupling losses through the unit result in less power at the output compared to the input port. For example, the coupling of output levels for a two-way power divider is -3 dB compared to the input level, and -6 dB for a four-way power divider.
Ideally, the total power at the output of a power divider would equal the power at the input. Dissipative losses through the stripline circuitry and circuit-board materials, however, result in insertion loss. In addition to insertion loss and isolation, a power divider can be characterized by a number of parameters, including return loss or voltage standing wave ratio (VSWR), amplitude balance between output ports, phase balance between output ports, and average power-handling capability.
Examples of several wideband coaxial power dividers from ETI include the two-way model D-1050-2, the two-way model D-218-2, the four-way model D-640-4, the eight-way model D-1050-2, the eight-way model D-226-8, and the 16-way model D-1040-16 power divider. The model D-218-2 two-way power divider (Fig. 1) covers the essential electronic-warfare (EW) band of 2 to 18 GHz with SMA connectors and maximum insertion loss of 1.2 dB across the full frequency range. The model D-218-2 two-way power divider achieves minimum isolation between ports of 19 dB with maximum input and output VSWR of 1.40:1. The twoway power divider features excellent amplitude balance between its two output ports, within 0.4 dB for all input levels and across the full 16-GHz bandwidth, while also maintaining tight phase balance of 5 deg. for the two output signals, critical for systems such as phased-array radars that rely on well controlled phase characteristics.
For higher-frequency operation, the model D-1050-2 two-way power divider (Fig. 2) has a frequency range of 10 to 50 GHz with 2.4-mm coaxial connectors with maximum insertion loss of 2.2 dB across the full frequency range. It delivers 16-dB minimum isolation between ports with 1.70:1 maximum input and output VSWR. The amplitude balance is 0.6 dB while the phase balance is 6 deg. from 10 to 50 GHz.
For extended frequency coverage and an additional two output ports, the model D-640-4 four-way power divider (Fig. 3) operates from 6 to 40 GHz with maximum insertion loss of 2.7 dB across the full frequency range. It also delivers minimum isolation of 16 dB between all ports, and exhibits maximum input and output VSWR of 1.65:1 with well-behaved return-loss performance even over the broad frequency range. The wideband fourway power divider employs tightly balanced circuitry throughout for excellent amplitude and phase balance, with performance levels of 0.7 dB and 10 deg., respectively.
When a greater number of outputs are needed, the model D-226-8 eightway power divider operates from 2 to 26.5 GHz with SMA connectors (Fig. 4). It exhibits maximum insertion loss of 3.5 dB, with 17-dB minimum isolation and 1.55:1 maximum input/output VSWR. The amplitude balance is 1.0 dB while the phase balance is 9 deg.
For applications requiring a division of power from a single input to 16 output ports, the model D-1040-16 is a 16-way power divider for use from 10 to 40 GHz (Fig. 5). It has maximum insertion loss of 5.2 dB with minimum isolation of 13 dB. The maximum VSWR is 1.80:1 while the amplitude balance is 1.5 dB and phase balance is 14 deg. Electromagnetic Technologies Industries, Inc., 50 Intervale Rd., Boonton, NJ 07005; (973) 394-1719 FAX: (973) 394-1710, Internet: www.etiworld.com.