Beamformers - General Information

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Merrimac’ s experience in designing and producing precision passive networks in stripline, microstrip and lumped element technology is virtually unique. No other company combines the experience in the required design disciplines to produce units covering frequencies from 100 kHz to 40 GHz while exhibiting bandwidth ratios as high as 100:1.

In the lower frequencies, from 100 kHz to about 2 GHz, the preferred technology is lumped element. However, if significant power levels are involved, as in an over-the-horizon radar, air-line (suspended stripline) is usually the choice. Many such components were designed by Merrimac twenty or more years ago for lower frequency early warning radars.

To counter offensive missiles, aerospace systems were developed to identify the missile’s precise trajectory and to afford earlier target acquisition. These defensive measures required accurate wideband beamformers operating from 500 MHz to 2 GHz or more. Using radar guidance, they had to be particularly rugged to survive wide variations in temperature as well as severe acceleration and vibration. Merrimac designed such a unit in the mid-1980’s using a combination of lumped element and microstrip technologies. Well over 1000 of these Hi-Rel beamformers were built by Merrimac over the life of the program. Not a single failure has been reported. Figure 6 shows one of the units.

Figure 6: Airborne Warning System Beamformer

Beamformers do not always operate at the frequency of the radar. Occasionally they can operate at an intermediate frequency (I.F.). Where size is critical as in a missile, for example, beamformers may operate in the 50 to 100 MHz region and usually use lumped element designs. Figure 7 shows an example of such a unit built by Merrimac in very large quantities for a missile program.

Figure 7: Missile Guidance Beamformer

Beamformers are also combined with other subsystems as shown in Figures 8 and 9. This subsystem is designed to maintain four input channels in a specific phase and amplitude relationship while the reference is switched in quadrature.

Figure 8: Beamformer Subsystem Schematic

Military electronic intercept and related RF intelligence gathering systems use beamformers to precisely locate signal sources. They must be very broadbanded in order to detect all emissions in the range of interest. Usually systems are broken into discrete frequency bands to preserve accuracy.

When used in various electronic intelligence roles (e.g., ELINT, SIGINT and COMINT) analysis of the signal is often essential to success. Thus, very low distortion in the signal path is essential to success. An eight-input, sixteen-output beamformer meeting these criteria is shown in Figure 10.

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