For DEM data of South Karnataka Coastal Area, you may refer to the following link of ASTER 30 meter Global Digital Elevation Model (GDEM) database of JSpaceSystems (Japan):
Rajesha, thanks for adding the location information. Like Jibran mentioned, all sources of freely available DEM such as SRTM, ASTER DEM, GMTED2010 etc. can be accessed via USGS, Earthexplorer link. However, if you want to have alternative sources of DEM, then you could look at the following sources:
For Cartosat DEM you can follow this link http://bhuvan.nrsc.gov.in/data/download/index.php
You can also derive DEMs from aerial photographs and satellites with stereo pair capabilities like with SPOT, IKONOS, WorldView, etc. based on the principles of Photogrammetry. LIDAR derived DEMs are also another alternative. If you have a detailed topographic map of the area where the contours are available, interpolation can be employed to derive a DEM.
Also check out the TerraSAR-X & TanDEM-X based WorldDEM....
http://www.geo-airbusds.com/worlddem/
Having said that, I am curious to know what is the aim of your research? Why are you looking for DEM other than the one provided by USGS link? Although there are a number of sources to obtain a DEM, depending on the purpose of your work, freely available sources such as SRTM and ASTER DEM might be just sufficient. But if you can be more specific, may be the RG community can help you better.