| The earth does not easily propagate high frequency signals. Low frequency, through the earth, signals would provide better penetration of the earth surface. Extremely low frequency communications has been a challenge for many years because of the underlying limitations such as significant background noise, and large antenna size. This thesis investigates the design of a compact quadrature sampling detector for extremely low frequency through the earth communication. It is hoped that a receiver such as that designed herein could receive signals at frequencies much much less than 10 kHz through the earth. Furthermore, this thesis compares the method of quadrature reception at these extremely low frequencies using simulation and hardware implementation with higher frequencies. This thesis also discusses the design of quadrature sampling detector and performance measurement of the quadrature detector at these extremely low frequencies. The results of the quadrature detection hardware testing show that it is indeed possible to use a quadrature detector at such low frequencies. |
