AT-2205(46)

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Attenuators: AT-2205(46) Application Field and Working Principle

Attenuators are devices that reduce the magnitude of a signal, usually by certain amount of decibels while preserving its waveform. Attenuation is the primary usage of attenuators; however, they can also be used to provide impedance matching, providing isolation, buffering, offsetting signals, and for gain adjustment.

AT-2205(46)

The AT-2205(46) is a 50 dB directional pad attenuator and is a passive two-port electromagnetic device. This attenuator is typically used in two-way radio communications systems, cellular mobile radio systems, and military telecommunications systems. Like all directional pad attenuators, it has a forward direction, and a reverse direction. The forward direction is used for receiving and transmitting signals, whereas the reverse direction is used for isolating the transmitter from the antenna.

Application Fields

The primary application field of the AT-2205(46) attenuator is for two-way communication systems, particularly ones that are in the high frequency (HF) and ultra high frequency (UHF) bands. These communication systems require non-linear attenuation because of the fading nature of signals in these frequency bands, and the AT-2205 is an ideal choice for such applications. The attenuator can also be used in systems that require medium-level attenuation with short term power handling capabilities, such as in boundary layer systems, cables and radio fixed links.

Working Principle

The AT-2205(46) directional pad attenuator is constructed of two termination stages. The first stage is a passive termination stage, which consists of two equal resistors in series connected to the two port transformer. The second stage is a varactor stage, which consists of two diodes connected in parallel. The varactor stage is responsible for the non-linearity of the attenuation. The two stages are connected together via a transformer that allows for high impedance isolation between the two stages.

When a signal is applied to the antenna connector, the two resistors in the passive termination stage divide the signal into two equal parts, sending one part to the antenna and one part to the reverse port. The reverse port is connected to a varactor consisting of two diodes that control the amount of voltage in the reverse port relative to the voltage in the antenna connector. This allows for the non-linear attenuation of the signal.

When the signal level at the antenna connector is higher than the reverse port, the diode circuit will absorb some of the energy and attenuate the incoming signal. As the signal level decreases at the antenna port, so too does the voltage at the reverse port. As the signal level drops, so does the amount of power that is attenuated, resulting in a non-linear attenuation curve.

Conclusion

The AT-2205(46) directional pad attenuator is a 50 dB attenuator used in two-way communication systems. The device is primarily used in HF and UHF systems, as well as in boundary layer systems, cable systems, and radio fixed links. The working principle of the attenuator is based on two stages of termination, a passive one and a varactor one, that create a non-linear attenuation curve when the signal level increases or decreases at the antenna connector.

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