Precision Attenuators for Wireless Production Applications

A series of electronically switched step attenuators that cover all of the frequencies used in wireless communications services

Precision Attenuators for Wireless Production Applications

Trilithic Inc.
Indianapolis, IN

With "faster, cheaper" as their mantra, wireless telephone manufacturers are leaving no area of production untouched as they search for ways to improve throughput. Not surprisingly, production is an area frequently scrutinized since even modest reductions in test time and increases in automatic test equipment (ATE) system uptime can yield significant benefits when multiplied over the thousands of telephones manufactured each day.

The PA-2.5 series 127 dB solid-state programmable attenuators have been designed to fit neatly into this scenario, combining the longevity and high accuracy of solid-state switching with high speed and broad dynamic range. The attenuators are currently the only electronically switched step attenuators that cover all of the frequencies used in wireless communications services (from 400 MHz to 2.5 GHz), including the industrial, scientific and medical band frequencies at 2.4 GHz.

The PA-2.5 attenuators are designed to optimize the most important characteristics in their likely applications, principally production ATE in which multimode, multifrequency telephones are tested, as well as test instrumentation and large computer-controlled attenuator banks. In a typical wireless production test application where several dozen telephones are tested simultaneously, the attenuators are used to change the signal level presented to each radio to determine at what signal strength handoff occurs as well as to test other receiver characteristics. Relative measurement accuracy is ensured at any frequency, an essential requirement in automated production test environments. Solid-state switching with a speed of 2 ms or less enhances the attenuators' performance in a production environment and provides an operating lifetime reaching billions of mean actuations before failure (MABF), far greater than that of typical mechanical alternatives with MABFs of only 1 to 100 million.

A typical attenuator model in the PA-2.5 series has a 127 dB attenuation range in 1 dB steps and a frequency range of 400 to 2500 MHz. Attenuation accuracy is 0.25 dB at 8 dB attenuation, 0.35 dB at 16 dB attenuation and 0.5 dB at 64 dB attenuation, as shown in Figure 1 . Insertion loss is less than 7.5 dB at 2500 MHz and switching speed is less than 2 ms. SWR is 1.4 or less (-16 dB return loss) to 1500 MHz and 1.5 or less (-14 dB return loss) to 2500 MHz, as shown in Figure 2 .

The attenuator handles an input power of +10 dBm and operates from a DC supply of up to +5 V DC at 200 mA. DC and control connections are 10-pin TTL with seven-line programming (TTL low for a zero attenuation setting and TTL high for a pad setting). Standard package dimensions are 4.80" x 2.00" x 1.25" with SMA RF connectors. The cost of the 127 dB model is $595 (1-9). Delivery is two to three weeks.