Omnidirectional cylindrical dipole antenna for underground earth-probing radars

Abstract

The invention belongs to an omnidirectional cylindrical dipole antenna for underground earth-probing radars, which comprises tubular monopole antenna cylinders, conical antenna heads, loading resistors, corresponding compression springs, inter-section fixing sleeves, supporting tubes, nut sleeves, connecting and fixing sleeves and coaxial cables, the loading resistors and the corresponding compression springs are respectively arranged in the holes of each two end surfaces between the antenna heads and the antenna sections and between the antenna sections, and monopole antennas are formed by the nut sleeves. Since the invention arranges the loading resistors between the antenna heads and the antenna sections and between the antenna sections to change the distribution of the current of the surface of the antenna, not only is the performance of the antenna improved, but also the production technique is simplified, the antenna can be matched with a borehole radar to operate under the conditions of center frequency equal to about 100M and bandwidth greater than or equal to 120M, the obtained waveform is neat, the main-to-side lobe ratio is distinct, tailing is tiny, and the waveform is stable; and consequently, the antenna is characterized in that: the comprehensive performance is high, the structure is simple, the diameter is small, the production cost is low, and the antenna can be matched with the borehole radar under the conditions of low frequency band and high bandwidth, and can effectively increase the performance, detection range and efficiency of the borehole radar.

Description

technical field [0001] The invention belongs to a dipole antenna used in conjunction with a detection radar, in particular to a broadband low-frequency omnidirectional cylindrical dipole antenna used in geological drilling wells in conjunction with a geological detection radar and loaded with resistance; the antenna can be used through Geological drilling wells work deep underground, and are used in conjunction with geological detection radar for geological environment investigation and resource exploration. Background technique [0002] Ground-penetrating radar is an efficient shallow geophysical detection technology. It transmits high-frequency pulsed electromagnetic waves, uses the difference in the electrical parameters of the underground medium, and analyzes and infers the structure and material of the underground medium according to the characteristics of the amplitude and phase of the echo. feature. The geophysical methods generally adopted by geological radar are ca...

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Problems solved by technology

The working frequency of the antenna is between 700M and 2500M, the working frequency is high and the bandwidth is only 50-60M, and the circuit is connected to the four branches correspondingly, so that the feed source and each branch can be better matched, which is helpful for the antenna Bandwidth expansion; however, the fourth branch adopts a helical structure, which increases the length of the antenna and also brings a part of the inductance effect. In addition, although the increase in the number of branches can increase the bandwidth to a certain extent, but at the same time The fluctuation (range) of S11 (antenna feed point voltage reflection coefficient) within its bandwidth is also very large, that is, the radiated energy at each frequency has a large difference, which will cause distortion of the time-domain waveform of antenna radiation, and cannot be used with pulse radar ; In addition, the antenna is an active antenna with a complex structure, and it is difficult to be used in conjunction with borehole radar

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