________________
Chapter 01
Introduction to Research
3.0 GHz frequency radio waves can penetrate up to 30 meter while 1.4 GHz frequency can penetrate better that 30 meters and if we choose further lower frequency like 500 MHz we may expect the penetration depth to be 50 meters. The schematics of fundamental concept of GPR functioning is presented in Figure 14. On the other hand, in case of dry snow, it is transparent up to 9 to 10 GHz. This suggests that for completely dry snow the frequencies below 9 GHz can look at the bottom of Snow, which means we can probe at the rock or soil below dry snow. However, if snow is wet then it will look at some point in the ice sheet layer and cannot reach to the bottom. Thus during summer period it would be better to probe the Ashtapad Temple ruins if buried to such an extent of 30-50 meters. Figure 14 shows the block diagram of the GPR prototype with its major components. It has a microprocessor-based electronic section and a microwave section. The electronic section controls the GPR's operation to perform data acquisition and processing, and to display the measured results. The heart of the GPR is the microwave section that dictates the system's performance as well as its size. It consists of a receiver, a transmitter, and receiving and transmitting antennas. The pulse generator of the transmitter generates a mono-cycle pulse of 0.33 nanosecond pulse width. The pulse is amplified by the power amplifier and is radiated by the transmitting antenna. The reflected signals from the surface and subsurface will go through the receiving antenna and sampling head to produce a low-frequency signal. This low-frequency signal, containing information of the subsurface conditions, is then amplified by the Intermediate Frequency (IF) amplifier.
Transmitter
Receiver
Display
Display
Pulse Generator
-
Amplifier
Sampling Head
Amplifier
Processor
4
4
} asem
Antenna
Layer
wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW
Fig. 14: Block diagram of fundamental concept of the Ground Penetrating Radar
37
- New Techniques to discover Ashtapad
