Radar type underground searching apparatus

A radar type underground searching apparatus comprising:

• a pulse generating unit for periodically generating pulses having a fixed peak value;
• a transmitting antenna for transmitting the pulses generated by said pulse generating unit from the ground surface into the ground;
• a receiving antenna for catching reflected pulses caused by objects buried in said ground;
• a housing for screening electromagnetic radiation and having one side open, said transmitting antenna and said receiving antenna being disposed in said housing;
• a radio-frequency amplifier for amplifying a reflected wave corresponding to each of said pulses with an amplification which increases each time pulses are transmitted;
• a sampler for obtaining a low-frequency signal formed by the extension of said reflected wave in time base by sampling the output of said radio-frequency amplifier at a series of sampling times, each being succeedingly delayed by a fixed period from the transmitting timing of each pulse wave;
• and
• a waveform display unit for displaying the wave-form of a low-frequency signal appearing at the output of said sampler;
• said transmitting antenna and said receiving antenna including:
• a pair of antenna elements each made of a plate shaped like an isosceles triangle bent to form an obtuse angle between a vertex portion and a trapezium portion and having a fold line between said vertex portion and said trapezium portion generally running parallel with the trapezium base of said isosceles triangle and nearly symmetrically abutted to each other at each said vertex portion, each said vertex portion having a height arranged approximately equal to the height of said housing, and each said trapezium portion lying in the same plane in general as the open side of said housing;
• a first load resistor and a second load resistor each connected at one of their ends to respective ends of the trapezium base of one antenna element of said pair of antenna elements;
• a third load resistor and a fourth load resistor each connected at one of their ends connected to respective ends of the trapezium base of the other antenna element of said pair of antenna elements;
• a first conductor and a second conductor each connected at one of their ends to respective other ends of said first resistor and said second resistor;
• a third conductor and a fourth conductor each connected at one of their ends to respective other ends of said third resistor and said fourth resistor;
• a fifth load resistor connected between said first conductor and said third conductor;
• and
• a sixth load resistor connected between said second conductor and said fourth conductor;
• whereby the presence of said objects is detected by the presence of peaks in said low-frequency signal caused by the reflection from said objects and the depth of said objects is detected by the time of the appearance of said peaks.