Mitel GPS Orion-S/-HD Receiver - Manual (Page 21)

Document Title: 17
User’s Manual for the GPS Orion-S/-HD Receiver
Document No. Issue 1.0
GTN-MAN-0110 June 22, 2003
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DLR/GSOCNo part of this document shall be reproduced in any form or disclosed to third parties without prior authorization.
3.2.6 External LNA Power Supply
The antenna line of the Orion GPS receiver provides a +5V DC power level to feed a low
noise amplifier with a maximum current consumption of about 50 mA. In some cases this
specification may not be appropriate and an external power supply be required. Possible
applications include e.g. the use of multiple parallel antennas or the use of miniature anten-
nas with 3.3V LNA. In this case a “bias-T” is employed to block the DC supply of the receiver
(via a built-in capacitor) and to insert the external supply voltage (via an R/F isolating induc-
tivity) to the subsequent antenna line. An added advantage of the external DC power supply
is the possibility to apply a current limitation and thus protect the receiver front-end against
short cuts in the antenna system.
Fig. 3.1 Schematic view of external LNA power supply us ing a bias -T
A block diagram showing the connection of receiver, bias-T, external supply and pre-
amplifier is given in Fig. 3.1. Bias-Ts suitable for GPS frequencies are available from various
manufacturers including M/A COM, Pasternak, etc.