GPS module - antenna circuit - Page 1
Forum section: electronics / rf-microwave

author: aurmer
author_rank: Regular Contributor
timestamp: November 16, 2016, 04:14:33 am
content: Consider thisGPS Disciplined TCXO module- and itsDatasheetIs it possible that all the needed antenna circuitry is within the IC? The spec sheet doesn't really specify.Can someone help me find a resource teaching how to construct the necessary antenna circuit for this module? What goes in this "black box" that I drew on my schematic?Would the "black box" be different for an active antenna than it would be for a passive one?Any leads on this subject are much appreciated. I have much to read and learn here.

author: edavid
author_rank: Super Contributor
timestamp: November 16, 2016, 04:34:52 am
content: You just connect a standard GPS antenna module. An active antenna is probably best.P.S. That module seems overpriced.

author: aurmer
author_rank: Regular Contributor
timestamp: November 16, 2016, 04:40:50 am
content: Quote from: edavid on November 16, 2016, 04:34:52 amThank you for this simple response, but unfortunately, as a novice, "standard GPS antenna module" doesn't really mean anything to me. I put "GPS antenna module" into mouser, and it just gave me "RF modules" and "GPS modules". Google gave me a bunch of "GPS modules with integrated antenna".Well, I understand what the words mean, but I don't know how to communicate what I want to Mouser. Would you mind giving me an example or part number?EDIT:I looked at your response again, and thought maybe I misunderstand. Are you saying that I should just connect the center SMA pin ofthis moduledirectly to pin 10 of my GD TCXO? Being new to all this, and I really find the data sheets to be vague (probably because they are assuming prior knowledge I don't have)...What about the "active" part of the antenna? doesn't it need more to it in order to function?

author: aurmer
author_rank: Regular Contributor
timestamp: November 16, 2016, 05:27:30 am
content: So the center SMA pin of the antenna connects directly to my "Antenna In" pin? Is this sure to provide whatever power the active antenna will need?I guess since I don't understand antennas all that well... I am expecting there to be a twisted pair in the length of the cord so that there is a return path for the power being sent to the active antenna.

author: edpalmer42
author_rank: Super Contributor
timestamp: November 16, 2016, 06:00:57 am
content: Believe it or not, there is an amplifier inside that small antenna. The antenna you linked to is unusual in that it accepts anything from 2V5 to 12V. Most don't go above 5V. Some older active systems used 12V, but today many have gone below 5V to 3V3.On the datasheet for the GPS module, the description for pin 10 says that it provides 5V for an active antenna. So yes, you connect the center pin of the antenna's SMA connector to pin 10. As blueskull said, some GPS modules require external circuitry for the antenna, but this Pletronics unit doesn't.So your 'Black Box' is nothing more than a piece of wire. Do NOT connect the 5V lead shown on your drawing to the antenna. That connection is handled inside the module. Of course, since that wire also carries the 1.574 GHz GPS signal, some care and attention is required to ensure that the signal isn't degraded.