Low-frequency through-the-earth communication receiving circuit

Abstract

The invention provides a low-frequency through-the-earth communication receiving circuit. The low-frequency through-the-earth communication receiving circuit comprises a narrow-band switching capacitance filter circuit and a digital DDS clock generation circuit; the centre frequency of the narrow-band switching capacitance filter circuit is variable; and the digital DDS clock generation circuit provides a clock signal for the narrow-band switching capacitance filter circuit, wherein the 3dB bandwidth value of the narrow-band switching capacitance filter circuit is the first multiple of the centre frequency. Due to setting of the size of the first multiple between the 3dB bandwidth value and the centre frequency, a power-frequency harmonic interference signal in the low-frequency band of a working frequency can be removed by filtration; influence of the power-frequency harmonic interference signal in a high-frequency band can be reduced; the centre frequency of the receiving circuit is adjustable; the power-frequency harmonic interference signal can be removed by filtration; and furthermore, narrowband band pass filtering is adopted in a narrowband variable capacitance filter circuit, so that the Q value of the receiving circuit is high.

Description

technical field [0001] Embodiments of the present invention relate to the technical field of low-frequency filtering, and more specifically, relate to a receiving circuit for low-frequency through-the-earth communication. Background technique [0002] The ground-penetrating wireless communication system uses the earth as the transmission channel. Compared with other communication systems, because the electromagnetic waves of the ground-penetrating communication have to propagate in the soil and rock layers of the earth, the earth is a conductive or semi-conductive medium, which is known from the theory of electromagnetic wave transmission. , the expressions of electromagnetic wave attenuation constant β and skin depth γ in conductive medium are respectively with Where f is the frequency of the electromagnetic wave, μ is the magnetic permeability of the propagation medium, and σ is the conductivity of the propagation medium. It can be seen that the penetration depth of the...

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Problems solved by technology

[0004] When ordinary filtering technology is used for the receiving circuit in the existing ground-penetrating communication system, the noise of broadband filtering is large, and the filtering effect on power frequency harmonic interference is poor; the high Q value of narrowband filtering is difficult to achieve, and the center frequency is fixed, and the communication frequency point is affected limit problem

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