There are several antennas for GPR antennas that you may use, and they mainly depend on the operating frequency which is determined by the GPR application, e.g. for anti-tank mines you need to operate in th efrequency range 400-800MHz, for anti-personnel 1GHz - 6GHz.
You may use several types of UWB antennas, such as the dielectric rod antenna, TEM horn antenna, conical spiral, etc.
There is several papers about this subject by Dr. Chi Chih Chen, you will find several of them on the internet.
you son't use simply a gaussian pulse, you use a differentiated gaussian pulse, in order to remove the DC.
The main advantages of gaussian pulse, are that it contains a broad frequency spectrum without nulls, and it can easily be generated using pulse generators.
hope this will help,
Best regards,
Adel