CN105024654A - Pseudo random signal electric method frequency-selecting amplification circuit - Google Patents

Abstract

The invention discloses a pseudo random signal electric method frequency-selecting amplification circuit. The pseudo random signal electric method frequency-selecting amplification circuit comprises a crystal oscillator (1), a programmable logic device (2), a resistor (3), a resistor (4), an operation amplifier (5), a resistor (6), a capacitor (7), a first single-pole double-throw analog switch (8) and a second single-pole double-throw analog switch (9). The programmable logic device (2) is provided with an in-phase output end (10) and an inverted-phase output end (11), and the signal-to-noise ratio can be increased as much as possible through frequency-selecting amplification. The signal detection precision and the exploration accuracy of a pseudo random signal electric method can be easily improved, signals can be measured in a measuring area farther from a transmitting source, and therefore the receiving and transmitting distance measured through the pseudo random signal electric method is increased, and the exploration range is expanded.

Description

Pseudo-random signal electrical method selective frequency amplifier circuit

Technical field

The present invention relates to the signal amplification technique field in exploration class detecting instrument, the pseudo-random signal electrical method selective frequency amplifier circuit especially in electrical method detecting instrument.

Background technology

In frequency domain electromagnetic methods Exploration Domain, need amplitude and the phase place of measuring set specific frequency signal, the signal of different frequency corresponds to the subsurface information of different depth of exploration, in order to obtain the subsurface information of different depth, needs to measure dozens of frequency.Under normal conditions, exploration device is measured with sweep method, and the square-wave signal of a frequency launched by transmitter at every turn, and the signal exciting underground medium to produce by this tranmitting frequency measured by receiver, until all frequency measurements are complete.Above-mentioned metering system field efficiency is lower, adds construction cost.Such as publication number of the prior art is that the Chinese invention patent application of CN1683941A and CN103969688A individually discloses a kind of pseudo-random three-frequency ground electroresponse method of measurement and pseudo-random signal Electrical Prospecting method, all improve observed efficiency by the pseudo-random signal of launching containing multiple useful signal frequency, once launch the measurement that can complete multiple frequency.

For pseudo-random signal electrical method, when total emission power is certain, owing to launching multifrequency pseudo-random signal, the transmitting power of each frequency will reduce, the intensity of receiver measuring-signal also decreases, and like this, has the amplifying circuit improving signal to noise ratio function and just seems particularly important.Therefore, signal amplification circuit is the important component part of pseudo-random signal electrical method detecting instrument.But, in the wild in exploration process, the signal that receiver is measured is very faint, but also the impact of multiple electromagnetic noise can be subject to, such as electrical noise, power frequency and harmonic noise thereof, radio communication noise etc., these electromagnetic noises have very wide spectrum distribution, and with the overlapping frequency ranges of measuring-signal, in order to Measurement accuracy signal, needing transmit frequency signal to carry out frequency-selecting amplification, namely when not amplifying noise, selectivity amplification being carried out to characteristic frequency.

Applicant, through retrieval, finds some related art, such as:

Publication number is that the Chinese invention patent application of CN1683941A discloses a kind of earth electric field pseudo-random three-frequency ground electroresponse measurement mechanism, by parameter identical at least two three, ripple signal extraction passage and Single Chip Microcomputer (SCM) system form described two pass earth electric field signals collecting receiver frequently, each signal extraction passage is by electric-field sensor, shared pathway, low channel, intermediate-frequency channel, hf channel, A/D change-over circuit and timing andlogic control circuit composition, the electric-field sensor output of three frequency ripple signal extraction passages is connected to the input of high-pass filtering circuit, the output of high-pass filtering circuit is connected to the input of preamplifier, the output of preamplifier is connected to the input of low-pass filter circuit, the input of middle rank amplifying circuit is connected to the output of low-pass filter circuit, the output of middle rank amplifying circuit is connected respectively to low-frequency band bandpass filter circuit by holding wire, midband bandpass filter circuit, the input of high-frequency band pass filter circuit, the output of low-frequency band bandpass filter circuit is connected to the input of low frequency amplifier, and the output of low frequency amplifier is connected to the input of low frequency detection and integrating circuit, and low frequency detection and integrating circuit output are connected to the input of integration type A/D change-over circuit, the output of midband bandpass filter circuit is connected to the input of intermediate frequency amplifier, the output of intermediate frequency amplifier is connected to the input of intermediate frequency detection and integrating circuit, intermediate frequency detection and integrating circuit output are connected to the input of integration type A/D change-over circuit, the output of high freguency bandpass filter circuit is connected to the input of high-frequency amplifier, the output of high-frequency amplifier is connected to the input of high frequency detection and integrating circuit, and the input of high frequency detection and integrating circuit is connected to the input of integration type A/D change-over circuit, the output of integration type A/D change-over circuit is connected to the input of Single Chip Microcomputer (SCM) system, and single-chip microcomputer system is connected to timing and control logic circuit by I/O interface line.First this invention utilizes shared pathway to process broadband signal, preamplifier and intermediate amplifier is used to amplify all frequencies, then respectively bandpass filtering and amplification are carried out to three frequencies with low channel, intermediate-frequency channel and hf channel, circuit structure is complicated, cost intensive, adds the power consumption of instrument, volume and destabilizing factor, and this device can only receive the signal of three frequencies, reduce the amount of information that exploration obtains, limit the scope of application of instrument.

Publication number is the method and apparatus that the Chinese invention patent application of CN103969688A discloses a kind of pseudo-random signal Electrical Prospecting, frequency response can be obtained at broad frequency range, pseudo-random signal receives and processing module carries out A/D conversion to the received signal, is converted into digital signal.Transmitting that this invention adopts is m sequence, it is more that m sequence comprises frequency content, the transmitting power of each frequency content is very low, measuring-signal is very faint, although the cross-correlation function recognition system that this invention utilizes has very strong antijamming capability, but, the precondition of cross-correlation function identification is that signal is converted to digital signal accurately by receiving system, if the pseudo-random signal received effectively is not amplified, receiving system may record less than useful signal, follow-up cross correlation process is by nonsensical, therefore, the method adopting wideband to amplify pseudo-random signal is unfavorable for the detection of small-signal, reduce the accuracy of exploration.

Publication number is the controllable signal receiver that the Chinese invention patent application of CN201705340U discloses a kind of energy loading pseudo random code, for the electrical signal detection in In Oil Field Exploration And Development process and reception, at least comprise the signals collecting and amplifying unit, filter unit and A/D converting unit that connect successively, wherein said signals collecting and amplifying unit are transferred to described filter unit after being amplified by the on-site signal collected and described A/D converting unit processes.The amplification mode adopted is that wideband amplifies, and while amplifying signal, be also exaggerated noise, therefore signal to noise ratio does not improve, and measurement data quality is not good.

Also there are the following problems for existing pseudo-random signal electrical instrument: the amplifier of use can not carry out frequency-selecting amplification for signal spectrum feature, or needs multiple passage to amplify specific frequency, and when using wideband to amplify, signal to noise ratio does not improve; When using multiple passage, system configuration is huge, and cost increases, and the frequency of amplification can be selected limited.

Summary of the invention

The object of the invention is to overcome the deficiencies in the prior art, a kind of pseudorandom multi-frequency signal selective frequency amplifier circuit is provided.

The object of the invention is to realize in the following manner:

A kind of pseudo-random signal electrical method selective frequency amplifier circuit is provided, it is characterized in that, crystal oscillator is connected with the input end of clock of programmable logic device, the in-phase output end of programmable logic device is connected to the control end of single pole double throw analog switch, the reversed-phase output of programmable logic device is connected to the control end of single pole double throw analog switch, input signal is connected to the inverting input of operational amplifier by resistor, the normal phase input end of operational amplifier is connected to reference to ground by resistor, the anti-phase ratio input of operational amplifier is connected to the moved end of single pole double throw analog switch, one of single pole double throw analog switch not moved end A be connected to an input of resistor, one of single pole double throw analog switch not moved end A be connected to an input of capacitor, one of single pole double throw analog switch not moved end A be connected to one of single pole double throw analog switch not moved end C, one of single pole double throw analog switch not moved end B be connected to another input of resistor, one of single pole double throw analog switch not moved end B be connected to another input of capacitor, one of single pole double throw analog switch not moved end B be connected to one of single pole double throw analog switch not moved end D, the moved end of single pole double throw analog switch is connected to the output formation of operational amplifier.

The present invention has following beneficial effect:

(1) selective frequency amplifier circuit in pseudo-random signal electrical instrument provided by the invention, under the prerequisite of not amplifying noise, (useful frequency here refers to the frequency content that in the pseudo-random signal waveform that transmitter is launched, energy is larger to amplify the signal of useful frequency, by using the apparent resistivity information of different useful frequency acquisition different depths, remove these useful frequencies, the signal of other frequencies is all considered as noise), therefore, amplify can improve signal to noise ratio as far as possible by frequency-selecting.By measuring in the wild in the contrast experiment of identical input signal, using the signal to noise ratio of selective frequency amplifier circuit of the present invention for 26dB, and using the signal to noise ratio of the wideband amplifying circuit in similar exploration kind equipment to be only-198dB.

(2) signal to noise ratio improve after contribute to improve pseudo-random signal electrical method input precision and exploration accuracy, survey region measurement signal that can be farther in range transmission source, in being the increase in the transmitting-receiving distance of pseudo-random signal electrical survey, extend the scope of exploration.Other use the receiver of pseudo-random signal all can use this amplifying circuit to improve signal to noise ratio.

Accompanying drawing explanation

Accompanying drawing 1 is selective frequency amplifier circuit theory diagram in pseudo-random signal electrical instrument.

Accompanying drawing 2 is 2 ⁿsequence three is pseudo-random signal oscillogram frequently.

Accompanying drawing 3 is uses 2 ⁿthe transfer curve figure of selective frequency amplifier circuit during sequence three frequency pseudo-random signal.

Reference numeral implication in Fig. 1 is as follows: 1---crystal oscillator, 2---programmable logic device, 3---resistor, 4---resistor, 5---operational amplifier, 6---resistor, 7---capacitor, 8---single pole double throw analog switch, 9---single pole double throw analog switch, 10---the in-phase output end of programmable logic device 2,11---the reversed-phase output of programmable logic device 2.

Embodiment

Below in conjunction with accompanying drawing, circuit of the present invention and specific embodiment are described in further detail:

Accompanying drawing 1 is selective frequency amplifier circuit theory diagram in pseudo-random signal electrical instrument, and input signal s (t) is first connected to the inverting input of operational amplifier 5 by resistor 3, the electric current being input to the inverting input of operational amplifier 5 is expressed as:

$i\left(t\right)=\frac{s\left(t\right)}{R_i}$

R in above formula _ifor the resistance value of resistor in selective frequency amplifier circuit 3.

The in-phase input end of operational amplifier 5 is connected to reference to ground by resistor 4, and resistor 4, for the impedance of two inputs of Operational Character, eliminates input offset voltage.According to " empty short " characteristic of operational amplifier, the anti-phase input terminal voltage of operational amplifier 5 is also 0.The inverting input of operational amplifier 5 is connected to the moved end of single pole double throw analog switch 8, and the model of operational amplifier can select OP07 etc.

Crystal oscillator 1 selects output frequency to be the quartz clock of 20MHz.Crystal oscillator 1 provides the operation clock of frequency stabilization for programmable logic device 2, and programmable logic device 2 selects EPM240.Programmable logic device inside produces pseudo-random signal sequences, is periodic signal and meets Dirichlet condition due to pseudo-random signal sequences, and therefore pseudo-random signal p (t) uses exponential type Fourier expansion to be:

$\left\{\begin{array}{c}p\left(t\right)=\underset{n=-\mathrm{\∞}}{\overset{\mathrm{\∞}}{\Σ}}P\left({\mathrm{n\ω}}_0\right)\exp \left({\mathrm{jn\ω}}_{0}t\right)\\ P\left({\mathrm{n\ω}}_0\right)=\frac{1}{T}{\∫}_{t_0}^{t_0+T}p\left(t\right)\exp (-{\mathrm{jn\ω}}_{0}t)dt\end{array}\right.$

In above formula, t represents the time, and t0 represents integration initial time, and T represents the cycle of pseudo-random signal, and n is from negative infinite to just infinite integer, P (n ω ₀) represent pseudo-random signal p (t) frequency spectrum, ω ₀represent the frequency resolution of carrying out spectrum analysis, the frequency resolution of spectrum analysis can have sample rate to obtain divided by sampling number.The pseudo-random signal produced is divided into homophase and anti-phase two-way to export.Homophase pseudo-random signal p (t) sequence is directly connected to the control end of single pole double throw analog switch 8, another road becomes anti-phase pseudo-random signal sequences through inverter, anti-phase pseudo-random signal is connected to the control end of single pole double throw analog switch 9, single pole double throw analog switch selectable ADG1436.Resistor 6 and capacitor 7 form RC parallel network, the not moved end A of single pole double throw analog switch 8 is connected to one end of RC parallel network, one end of RC parallel network is also connected with the not moved end C of single pole double throw analog switch 9, the not moved end B of single pole double throw analog switch 8 is connected to the other end of RC parallel network, the other end of RC parallel network is also connected with the not moved end D of single pole double throw analog switch 9, and the moved end of single pole double throw analog switch 9 is connected with the output of operational amplifier 5.

In this pseudo-random signal electrical instrument, selective frequency amplifier circuit operationally, and the in-phase output end of programmable logic device 2 is contrary with the level of reversed-phase output, and when namely in-phase output end output is ' 1 ', reversed-phase output exports as ' 0 ', and vice versa.When in-phase output end exports as ' 1 ', and reversed-phase output export for ' 0 ' time, A is connected in the moved end of single pole double throw analog switch 8, and D is connected in the moved end of single pole double throw analog switch 9, and the electric current flowed into from input signal through resistor 3 like this flows through RC parallel network from top to down; When in-phase output end exports as ' 0 ', and reversed-phase output export for ' 1 ' time, B is connected in the moved end of single pole double throw analog switch 8, and C is connected in the moved end of single pole double throw analog switch 9, and the electric current flowed into from input signal through resistor 3 like this flows through RC parallel network from below to up.Therefore, input current is changed direction according to pseudo-random signal sequences under the control of two single pole double throw analog switches, to the alternately charging of RC parallel network, be equivalent to be multiplied by pseudo-random signal to input current, then equivalent current x (t) flowing through RC parallel network is expressed as:

$x\left(t\right)=\frac{s\left(t\right)}{R_i}\×p\left(t\right)$

In above formula, s (t) represents input signal, R _ifor the resistance value of resistor in selective frequency amplifier circuit 3.

Input signal s (t) be multiplied after, carry out Fourier transform expression, utilize the frequency shift property of Fourier transform, obtain

F[s(t)exp(jω ₀t)]＝S(ω-ω ₀)

In above formula, F represents Fourier's operator, S (ω-ω ₀) represent that the frequency spectrum S (ω) of input signal s (t) carries out frequency displacement ω ₀.

The frequency spectrum X (ω) flowing through equivalent current x (t) of RC parallel network can be expressed as:

$X\left(\mathrm{\ω}\right)=\frac{1}{R_i}\underset{n=-\mathrm{\∞}}{\overset{\mathrm{\∞}}{\Σ}}P\left({\mathrm{n\ω}}_0\right)S(\mathrm{\ω}-{\mathrm{n\ω}}_0)$

According to the character of Fourier transform, be signal s (t) of real number for voltage, the real part of its frequency spectrum S (ω) is even signal, and imaginary part is strange signal, and the frequency spectrum designation flowing through the equivalent current of RC parallel network is:

$X\left(\mathrm{\ω}\right)=\frac{2}{R_i}\underset{n=1}{\overset{\mathrm{\∞}}{\Σ}}P\left({\mathrm{n\ω}}_0\right)S(\mathrm{\ω}-{\mathrm{n\ω}}_0)$

The resistance of resistor 6 is R _f, the electric capacity of capacitor 7 is C, then the impedance of parallel network can be expressed as:

$Z\left(\mathrm{\ω}\right)=\frac{R_f}{(1+{\mathrm{j\ωR}}_{f}C)}$

The frequency spectrum U (ω) that the impedance that the electric current flowing through RC parallel network is multiplied by parallel network obtains the output voltage of operational amplifier 5 is:

$\begin{array}{c}U\left(\mathrm{\ω}\right)=-\frac{R_f}{(1+{\mathrm{j\ωR}}_{f}C)}\frac{2}{R_i}\underset{n=1}{\overset{\mathrm{\∞}}{\Σ}}P\left({\mathrm{n\ω}}_0\right)S(\mathrm{\ω}-{\mathrm{n\ω}}_0)\\ =-S\left(\mathrm{\ω}\right)\frac{2R_f}{R_i(1+{\mathrm{j\ωR}}_{f}C)}*\underset{n=1}{\overset{\mathrm{\∞}}{\Σ}}P\left({\mathrm{n\ω}}_0\right)\mathrm{\δ}(\mathrm{\ω}-2{\mathrm{n\ω}}_0)\end{array}$

In above formula, " * " represents convolution algorithm, and the output of operational amplifier 5 is the output of amplifying circuit, and the transmission characteristic function finally obtaining pseudo-random signal selective frequency amplifier circuit is:

$\begin{array}{c}H\left(\mathrm{\ω}\right)=\frac{U\left(\mathrm{\ω}\right)}{S\left(\mathrm{\ω}\right)}=-\frac{2R_f}{R_i(1+{\mathrm{j\ωR}}_{f}C)}*\underset{n=1}{\overset{\mathrm{\∞}}{\Σ}}P\left({\mathrm{n\ω}}_0\right)\mathrm{\δ}(\mathrm{\ω}-2{\mathrm{n\ω}}_0)\\ =-\frac{2R_f}{R_i}\underset{n=1}{\overset{\mathrm{\∞}}{\Σ}}P\left({\mathrm{n\ω}}_0\right)\frac{1}{\[1+j(\mathrm{\ω}-{\mathrm{n\ω}}_0)R_{f}C\]}\end{array}$

δ represents impulse function, and the amplitude-frequency transmission characteristic function of pseudo-random signal selective frequency amplifier circuit is:

$\left|H\left(\mathrm{\ω}\right)\right|=\frac{2R_f}{R_i}\underset{n=1}{\overset{\mathrm{\∞}}{\Σ}}P\left({\mathrm{n\ω}}_0\right)\frac{1}{\[1+j(\mathrm{\ω}-{\mathrm{n\ω}}_0)R_{f}C\]}$

Visible, when frequency input signal is n ω ₀time, can obtain, when frequency input signal is away from the frequency n ω of pseudo-random signal ₀time, the amplitude-frequency response of selective frequency amplifier circuit is:

$\left|H\left(\mathrm{\ω}\right)\right|=\frac{2R_f}{R_i}\underset{n=1}{\overset{\mathrm{\∞}}{\Σ}}P\left({\mathrm{n\ω}}_0\right)\frac{1}{\sqrt{1+{\[(\mathrm{\ω}-{\mathrm{n\ω}}_0)R_{f}C\]}^2}}$

When the frequency of input signal is away from n ω ₀time, circuit output amplitude is with ω-n ω ₀increase and reduce.It can also be seen that from above formula, R _fc is larger, and the frequency band of frequency selective amplifier is narrower, increases R _for C can make amplification bandwidth diminish, the at utmost impact of noise decrease.

In sum, selective frequency amplifier circuit carries out frequency-selecting amplification according to the spectrum distribution of pseudo-random signal to input signal, and therefore, selective frequency amplifier circuit is applicable to the amplification of set specific frequency signal in pseudo-random signal electrical method very much.By field contrast experiment, use the signal to noise ratio of selective frequency amplifier circuit of the present invention for 26dB, and use the signal to noise ratio of the wideband amplifying circuit in similar exploration kind equipment to be only-198dB.

Embodiment

Below with use in pseudo-random signal electrical method 2 ⁿpseudo-random sequence signal is illustrated.When carrying out pseudo-random signal electrical prospecting, transmitter uses the long lead of two-terminal-grounding to launch 2 ⁿthree frequency pseudo random sequences, long lead is generally 1 ~ 3 km.The electromagnetic wave that the pseudo-random signal of launching produces is to underground propagation, and the objective body of excitation underground produces induced signal, and electromagnetic induction signal measured by receiver.Pseudo-random three-frequency ground electroresponse method of measurement is disclosed by patent CN1683941A, does not repeat them here.The current waveform of following mathematic(al) representation can be adopted as measuring-signal:

$I=\left\{\begin{array}{c}A,-T/2<T<-T/8\\ -A,-T/8<T<0\\ A,0<T<T/8\\ -A,T/8<T<T/2\end{array}\right.$

Described in above formula 2 ⁿthree frequency pseudo random sequence waveforms as shown in Figure 2, comprise three basic frequency f in its frequency spectrum ₀, 2f ₀, 4f ₀, f ₀be 2 ⁿthe fundamental frequency of three frequently pseudo random sequences, amplitude corresponding to three is respectively 0.9003A, 0.6366A, 0.6366A, 2 ⁿalso 3f is comprised in the frequency spectrum of three frequency pseudo random sequences ₀, 5f ₀, 6f ₀, 7f ₀, 9f ₀but, because these frequency energy are less relative to three basic frequencies, in pseudo-random signal electrical prospecting, do not regard useful frequency as.Therefore, 2 ⁿthree frequency pseudo random sequence frequency spectrums can approximate representation be:

P(nω ₀)≈0.9003δ(f ₀)+0.6366δ(2f ₀)+0.6366δ(4f ₀)

Receiver sends into receiving test circuit after receiving induced signal by electric field or magnetic field sensor, first needs the selective frequency amplifier circuit shown in Fig. 1 to amplify.The resistance R of resistor 3 is set _i=100 Ω, the electric current flowing into operational amplifier 5 after resistor 3 is:

$i\left(t\right)=\frac{s\left(t\right)}{100}$

Programmable logic device 2 exports a road homophase, the anti-phase two-way 2 altogether in a road ⁿthree frequency pseudo random sequences control single pole double throw analog switch 8 and single pole double throw analog switch 9 respectively, the sequence wherein controlling single pole double throw analog switch 9 is the inversion signal controlling single pole double throw analog switch 8 sequence, simultaneously, according to the characteristic of operational amplifier " empty disconnected ", all flow through RC parallel network from resistor 3 inflow current.Equivalent current x (t) then flowing through RC parallel network is expressed as:

$x\left(t\right)=\frac{s\left(t\right)}{R_i}\&times;p\left(t\right)$

The current spectrum then flowing through RC parallel network is:

$X\left(\mathrm{\&omega;}\right)=\frac{2}{R_i}\&lsqb;0.9003S(\mathrm{\&omega;}-f_0)+0.6366S(\mathrm{\&omega;}-2f_0)+0.6366S(\mathrm{\&omega;}-4f_0)\&rsqb;$

The resistance of resistor 6 is R _f, the electric capacity of capacitor 7 is C, R _fduring=100k Ω, C=100 μ F, then the impedance of parallel network can be expressed as:

$Z\left(\mathrm{\&omega;}\right)=\frac{100000}{(1+j10\mathrm{\&omega;})}$

The electric current flowing through RC parallel network is multiplied by the resistance of RC parallel network, and the frequency spectrum U (ω) obtaining the output voltage of operational amplifier 5 is:

$U\left(\mathrm{\&omega;}\right)=-S\left(\mathrm{\&omega;}\right)\frac{2000}{(1+j10\mathrm{\&omega;})}*\&lsqb;0.9003\mathrm{\&delta;}\left(f_0\right)+0.6366\mathrm{\&delta;}\left(2f_0\right)+0.6366\mathrm{\&delta;}\left(4f_0\right)\&rsqb;$

In above formula, " * " represents convolution algorithm, and the output of operational amplifier 5 is the output of amplifying circuit, and the transmission characteristic function finally obtaining pseudo-random signal selective frequency amplifier circuit is:

$H\left(\mathrm{\&omega;}\right)=-\frac{2000}{(1+j10\mathrm{\&omega;})}*\&lsqb;0.9003\mathrm{\&delta;}\left(f_0\right)+0.6366\mathrm{\&delta;}\left(2f_0\right)+0.6366\mathrm{\&delta;}\left(4f_0\right)\&rsqb;$

F ₀during for 100Hz, 2 ⁿthe transfer curve figure of sequence three frequency pseudo-random signal selective frequency amplifier circuit as shown in Figure 3.As can be seen from the figure, frequency selective amplifier can amplify three basic frequency 100Hz, 200Hz and 400Hz, multiplication factor is respectively 900.3 times, 636.6 times and 636.6 times, other frequencies that can amplify comprise 300Hz, 500Hz, 600Hz, 700Hz, 900Hz, corresponding multiplication factor is respectively 300,180,212,129,100, although launch at transmitter 2 ⁿthree frequently pseudo random sequences comprise these spectrum components, but due to energy on the low side compared with three dominant frequency spectrums, do not use.And the gain of other frequencies is about 0.3.Therefore, by 2 ⁿselective frequency amplifier circuit of the present invention is used in three frequency pseudo-random signal electrical method detecting instruments, three useful basic frequency 100Hz, 200Hz and 400Hz multiplication factor are greater than 600 times, and comprise in transmitter emission signal frequency, and in exploration, do not have 300Hz, 500Hz, 600Hz, 700Hz, 900Hz multiplication factor used to be greater than 100, and be 0.3 in other frequency gain comprising noise, namely decay to original about 1/3rd.

The present embodiment is by the description of a concrete example use and calculating, advantageously indicate pseudo-random signal selective frequency amplifier circuit of the present invention and be exaggerated useful frequency in pseudo-random signal electrical prospecting, the noise of other frequencies that decayed, by measuring in the contrast experiment of identical input signal, use the signal to noise ratio of selective frequency amplifier circuit of the present invention for 26dB in the wild; And using the signal to noise ratio of the wideband amplifying circuit in similar exploration kind equipment to be only-198dB, signal to noise ratio is greatly improved.Signal to noise ratio contribute to improve after improving pseudo-random signal electrical method input precision and exploration accuracy, survey region measurement signal that can be farther in range transmission source, in being the increase in the transmitting-receiving distance of pseudo-random signal electrical survey, extends the scope of exploration.

Claims (2)

1. a pseudo-random signal electrical method selective frequency amplifier circuit, it is characterized in that, comprise crystal oscillator (1), programmable logic device (2), resistor (3), resistor (4), operational amplifier (5), resistor (6), capacitor (7), the first single pole double throw analog switch (8), the second single pole double throw analog switch (9), programmable logic device (2) has in-phase output end (10) and reversed-phase output (11).

2. pseudo-random signal electrical method selective frequency amplifier circuit according to claim 1, it is characterized in that, crystal oscillator (1) is connected with the input end of clock of programmable logic device (2), the in-phase output end (10) of programmable logic device (2) is connected to the control end of the first single pole double throw analog switch (8), the reversed-phase output (11) of programmable logic device (2) is connected to the control end of the second single pole double throw analog switch (9), input signal is connected to the inverting input of operational amplifier (5) by resistor (3), the normal phase input end of operational amplifier (5) is connected to reference to ground by resistor (4), the anti-phase ratio input of operational amplifier (5) is connected to the moved end of the first single pole double throw analog switch (8), one of first single pole double throw analog switch (8) not moved end A be connected respectively to an input of resistor (6), an input of capacitor (7) and one of the second single pole double throw analog switch (9) not moved end C, first single pole double throw analog switch (8) another not moved end B be connected respectively to another input of resistor (6), another input of capacitor (7) and another the not moved end D being connected to the second single pole double throw analog switch (9), the moved end of the second single pole double throw analog switch (9) is connected to the output formation of operational amplifier (5).