Generally, "support for active antenna" means that the receiver can supply DC power (typically 3.3V or 5.0V, current-limited to about 30 mA) up the antenna cable. With a highly-integrated module like this, that support is generally done on the PCB that it's mounted on, rather than inside the module itself.
While this module may work perfectly well with passive antennas (especially if the connection is short), active antennas will pretty much always give you a slightly better noise figure.
there are several things to keep in mind, when combining data from different systems.
Combining different Satellite Navigation systems
Typically it is possible to combine gps+glonass or any other navigation system. That is called GNSS (Global Navigation Satellite System). For a single GPS case you need 4 Satellites for the components [X,Y,Z, dt (the estimated receiver clock error)]. For each new systems you have to add one bias term, describing the difference between the transmitted time scales (since every system has it's own specific time scale) for each system relative to one time scale, which is kept as reference. This bias term is an additional unknown in the estimation equation to receive/determine the position solution. Consequently you need at least 3 Satellites for system 1 and 2 satellites for System 2 (for example...any other combinations are also possible). The additional bias term will describe the relative difference from one time scale to the other, (Petrowski, page 95f, 2014).
Example: 3 GPS satellites and 2 Glonass satellites will give a direct solution without redundance (and no control). The system will be [X,Y,Z, dt(GPS), bias(GLONASS_to_GPS)]. The more satellites the more redundance is possible - and you can control your estimation process weather by RAIM, Kalman filter, least squares (sequentially) or any other processor technique.
Further details for combining different systems
Be sure to get the correct and no corrupt data from the antenna and the receiver ensemble. Since you ask if a GPS Module would be able to use GLONASS - I suggest it isn't possible, since GLONASS uses a complete different access method than GPS. GLONASS Satellites are identified by their specific frequency (Frequency Division Multiple Access - FDM) and GPS Satellites are identified by different codes (Code Division Multiple Access - CDMA). The current new GLONASS-K Satellite generation will support CDMA Signals, but the current GLONASS constellation works completely with FDMA (current GLONASS constellation)
Additionally the antenna inside the mobile device must be able to see the GLONASS-Signals to give them to the baseband processor where the GNSS signals will be aquired. Both GPS and GLONASS use different bandwiths (see signal structure in Petrowski 2014, page 39) - so you better keep in mind to use a GNSS-capable module for processing not only GPS but GLONASS, COMPASS, Galileo (and any other derivative) Data. With a GNSS receiver unit you will be able to do this, but I'm not sure if you will be able to do this with a pure GPS module.
For further reading (below others):
- Petrowski, Ivan G. (2014): GPS, GLONASS, Galileo and Beidou for Mobile Devices, iP-Solutions, Cambridge University Press, Tokyo
- Hofmann-Wellenhof, Bernd, Lichtenegger, Herbert, Wasle, Elmar (2008): GNSS - Global Navigation Satellite Systems, Springer, Berlin
Best Answer
The system defined frequencies for GPS and GLONASS are the center frequencies. The data and signals aretransmitted with different bandwiths. Since the GPS and GLONASS frequencies are close together, you can desing the antenna to cover both frequencies. It is possible that a single GPS antenna can 'see' GLONASS frequencies and push them forward as observations to the receiver-unit (processor). BUT (!) Although the antenna seems to 'see' the GLONASS satellites, the problem is that the data has to be prepared in a appropriate way! This is carried out by the LNA (low noise amplifier) of the antenna.
Why?
This has to do with the bandwith of the antennas LNA and how sharp the edges of the filter inside the antenna front end are designed. As long as the LNA is not optimized for GLONASS reception, you will never be sure to use the correct data for your receiver.
Solution
Check the quality of the incomming data (signal strength, how stable is the code or carrier solution) and the repeatability of a single GLONASS solution compared to a GPS-only solution. But the best way will be to use an antenna with multi-constellation support (GPS+GLONASS+derivatives) - also named as Global Navigation Satellite Systems (GNSS). Therefore you need to collect some information of the antennas LNA.
further reading: