Antenna Combiner

Posted on Feb 5, 2014

The Antenna Combiner (A3021) is an active combiner for four 50- © coaxial antenna connections. The output is a combination of the four inputs with net gain of roughly +11 dB. The A3021 is intended for use with four Loop Antennas ( A3015B ), each of which is placed in a separate faraday enclosure and receiving signals from subcutaneous transmitters

Antenna Combiner
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. The A3021 needs no terminators on its unused inputs. The circuit is unconditionally stable and isolates itself from local interference so effectively that it needs no shielding around the circuit board. We supply +5V power to the A3021 through a shielded LWDAQ Cable. Current consumption is 140 mA. We connect the other end of the cable to a LWDAQ Driver. The only purpose of the LWDAQ Cable is to provide +5V power. No communication occurs between the A3021 and the LWDAQ Driver. The A3021B is designed for use with the Data Receiver ( A3018 ). The A3018 is a LWDAQ Device, and so its presence assures us of a LWDAQ Driver into which we can plug the A3021. The A3021 amplifies its four inputs, combines them, and passes the sum through an attenuator on its way to the output connector. The input ports are P1 through P4 on the schematic, and PORT1 through PORT4 on the circuit board. The output port is S on the schematic and SUM on the circuit board. Figure: The Bottom Side of the A3021B Circuit. We see the four port amplifiers and the curving coplanar wave-guides that carry the amplified antenna signals to the combiner. The amplifiers provide gain to offset the loss introduced by the combiner. The combiner performs better when connected to a 50- © signal source, and the amplifiers always provide such a source, regardless of whether or not their own inputs are well-terminated. Furthermore, by amplifying the antenna signal before it...

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