The heart of the RASCAL facility is the compact range, which allows researchers to perform timely, low-cost, precision measurements for evaluation and validation, while accommodating complex configurations that cannot otherwise be studied analytically. Antenna aperture measurements typically mandate a large physical distance—the far-field condition. To simulate a uniform plane wave in a limited amount of space, RASCAL is equipped with a precision-manufactured, parabolic rolled-edge reflector (see Figure 1) that collimates the impinging spherical wave from an offset feed, resulting in a uniform plane wave with a 3 × 4 ft quiet zone.

Figure 2. BANTAM range

In addition to RASCAL’s compact range, the facility houses a broadband antenna near-field test and measurement (BANTAM) range, which enables timely, low-cost, near-field test and evaluation of active array technology. Active array evaluation is extremely useful for diagnostic analysis, where far-field data does not reveal the location of a defective element. Simulacrum displays from acquired data allow field distribution imaging of a measured aperture, near-field amplitude distribution data, and mathematically transformed far-field information. Researchers can use the BANTAM range to test large and fragile structures without adding stresses and associated deflections. In addition, BANTAM allows researchers to measure transmit array patterns, which are impossible to measure in a standard compact range.

Researchers built BANTAM inside a rigid aluminum enclosure lined with an 8 in. pyramid and wedge-shaped absorber (see Figure 2) to reduce measurement noise and eliminate unwanted reflections from the array being tested. The absorber also provides a 1-18 GHz frequency range. Currently, BANTAM has planar near-field scan capability, and engineers will add cylindrical near-field scan capability in the near future.

RASCAL provides a unique capability for timely and efficient antenna measurement and evaluation. The compact and near-field ranges feature rapid prototyping capability, modeling and simulation evaluation, and quick setup and teardown of test equipment, all of which results in significantly reduced test and evaluation time and expense.

Mr. Joshua Radcliffe, of the Air Force Research Laboratory’s Sensors Directorate, wrote this article. For more information, contact TECH CONNECT at (800) 203-6451 or place a request at http://www.afrl.af.mil/techconn/index.htm. Reference document SN-H-05-01.