This patent-pending, high-gain, log-periodic antenna employs a bent element design for a reduction in size without a sacrifice in RF performance.
Antenna technology does not often benefit from dramatic new developments compared to, for example, semiconductor technology. But the designers at Amplifier Research (Souderton, PA) have managed to significantly advance wideband antenna technology for electromagnetic-compatibility (EMC) testing. The company's Radiant Arrow 26 (model AT5026) log-periodic antenna uses a unique folded-element design to shrink the size of the antenna without trimming its bandwidth. The Radiant Arrow 26 features a 26-MHz-to-5-GHz bandwidth.
The Radiant Arrow 26 (see figure), which can also be calibrated for EM emissions testing, is ideal for EMC testing. The compact antenna design can accomplish this without need of the typical bat-wing log-periodic approach that tends to corrupt the electric (E) field, especially in smaller test enclosures. The Radiant Arrow 26 uses the folded elements to keep antenna tips away from the walls of shielded enclosures, helping to reduce reflections. The shorter configuration is significant both mechanically and electrically, resulting in an antenna which is closer to the test object at low frequencies. This is accomplished by bending the elements forward as well as redesigning the standard log-periodic structure to have closer element spacing. Copper heat sinks at the antenna's tip help the new design handle high power levels.
The 50-Ω antenna can handle input power levels to 5000 W. Although minimum gain varies from −3 to 6 dBi at the very lowest frequencies (26 to 80 MHz), the minimum gain of 6 dBi is a relatively flat ±1.5 dB across the majority of the bandwidth, from 80 MHz to 5 GHz. The maximum VSWR is 3.0:1 from 80 MHz to 5 GHz. The Radiant Arrow measures 279.4 × 53.6 × 202.4 cm and weighs 22.5 kg.
For applications not requiring the low-frequency response, the company also offers the 80-MHz-to-5-GHz Radiant Arrow 80 (model AT5080). This smaller antenna also boasts 6 dBi gain with ±1.5 dB gain flatness. The Radiant Arrow 80 measures 132.1 × 20.32 × 97.8 cm and weighs 7.94 kg. Both antennas are supplied with a wall bracket that can also be mounted in two perpendicular planes using an optional tripod. Both are available with a variety of connector options, including type N, C, 7-16, and 1-5/8 EIA female connectors (the latter connector has an upper limit of 3 GHz). Amplifier Research, 160 School House Rd., Souderton, PA 18964-9990; (215) 723-8181, FAX: (215) 723-5688, e-mail: info@ampli fiers.com, Internet: www.amplifiers.com.
