ITPA20100011A1 - BANK OF FILTERS THROUGH ORDER BANDS HIGH FOR APPLICATIONS IN SO.D.A.R. - Google Patents

Description

DESCRIPTION

Field of application

The present invention is generally applicable to the electronic instrumentation sector and has particularly as its object a bank of passband filters applicable to systems for monitoring atmospheric parameters by means of sound waves (SO. DAR.).

The invention also relates to a SO.D.A.R. of atmospheric parameters by means of sound waves, incorporating the aforementioned filter bank.

State of the art

One of the most effective systems for remote detection, monitoring and evaluation of the temporal evolution of the phenomena of the lower atmosphere is the so-called SO.D.A.R. (Sonic Detection And Ranging).

This system is essentially made up of a network of electroacoustic transducers capable of sending sound signals into the atmosphere which are variously reflected by the zones of the boundary layer of the atmosphere with different physical and dynamic characteristics.

The signals that propagate in the atmosphere by means of suitable transmitting antennas encounter discontinuities of mechanical and thermal origin which are reflected, at least in part, in the opposite direction to that of transmission and are acquired by means of a system of receiving antennas.

In summary, the SO.D.A.R. it allows the study of atmospheric stability, convective movements (thermal feathers), turbulence allowing a continuous and real-time monitoring of the boundary layer or ABL (Atmospheric Boundary Layer).

The SO.D.A.R. it can be advantageously used in various technical sectors, such as:

- pollution control, in which the system does not directly provide information on the degree of atmospheric pollution but manages to provide information on thermal stratifications which are instead directly responsible for the diffusion of pollutants;

- airport security control, in which it is necessary to inform pilots in real time about the possible presence of dangerous dynamic situations in the atmosphere during the most critical landing and take-off phases;

- preventive study of sites and climatological analyzes at high altitude for the location of areas suitable for the installation of industrial plants.

In the case of the SO.D.A.R. so-called â € œtriaxialâ €, there are three independent antennas that send three distinct signals with three different frequencies into the atmosphere to improve the comprehensibility of the signals acquired by the SO.D.A.R.

However, it is possible that the various echoes of the signals overlap and therefore do not allow to obtain correct information.

Furthermore, the signals detected by the antennas are affected by environmental noise outside the band of interest, therefore they can distort the detection of atmospheric parameters.

The problem therefore arises of cleaning up the echo signals collected by the antennas and processed by an appropriate electronic device.

Presentation of the invention

The purpose of the present invention is to provide a monitoring system which has characteristics of high reliability and accuracy at a relatively low cost.

A particular purpose is that of realizing a filtering system that allows to clean the signals from the environmental noise outside the band of interest.

A particular purpose is to realize a filter bank that allows to use the SOD.A.R. in both terrestrial and marine environments.

These aims as well as others which will appear more clearly in the following are achieved by means of a bank of passband filters for a monitoring system of atmospheric phenomena (SO. D.A.R.), in accordance with claim 1, in which the system comprises three antennas suitable for to send into the atmosphere signals generated by respective electroacoustic transducers and to receive the signals variously reflected by the different zones of the boundary layer of the atmosphere. The filter bank is characterized by the fact that it includes a motherboard on which a clock circuit is installed for the generation of signals of suitable frequency and a plurality of band-pass filters to reduce the spurious harmonics present in the signal. clock, said filters being configured to operate with two series of different frequencies corresponding to two frequency bands in respective sectors of application.

Conveniently, the two different frequency series are intended for terrestrial and marine applications respectively and include a first series of low frequencies of 1600Hz, 1900Hz, 2300Hz respectively and a second series of high frequencies of 5000Hz, 6000Hz, 7000Hz respectively.

Filters comprise sub-cards that make up a band-pass filter for each signal input channel.

Advantageously, the clock circuit is configured to generate a single high stability clock signal, which is subjected to division by means of three binary counters to obtain three differentiated clock signals capable of guaranteeing the same stability as the unit signal.

Conveniently, the motherboard has a plurality of I / O input and output coupling circuits with respective slots for secondary cards and the filters are constituted by filtering cards configured to filter respective signals corresponding to different operating frequencies, the cards being insertable in said slots in order to simplify their replacement in case of malfunction or update,

In a second aspect of the invention there is provided a system for monitoring atmospheric phenomena (SO.D.A.R.) of the triaxial type, in accordance with claim 10, which includes three antennas designed to send signals generated by respective electroacoustic transducers and receive the variously reflected signals from the different zones of the boundary layer of the atmosphere, characterized by the fact of comprising a filter bank consisting of a motherboard on which a clock circuit is installed for the generation of three signal bands of suitable frequency and a plurality of band-pass filters for the abatement of the spurious harmonics present in the clock signal, said filters being configured to operate with two series of different frequencies corresponding to two optimal frequency bands in respective sectors of application, said clock circuit being adapted to generate a high stability unitary clock signal, called signal ale being subjected to division by means of binary counters to create differentiated clock signals able to guarantee the same stability of the unit signal, in order to avoid the overlapping of the various reflected signals and to clean up the signals detected by the environmental noise outside the band of interest.

The dependent claims describe construction details of the filter bank according to the invention.

Brief description of the Figures

FIG. 1 represents an electrical diagram of a first embodiment of the filter bank according to the invention with a central frequency of 1600 Hz;

FIG. 2 represents an electrical diagram of a first embodiment of the filter bank according to the invention with a central frequency of 1900 Hz;

FIG. 3 represents an electrical diagram of a first embodiment of the filter bank according to the invention with a central frequency of 2300 Hz;

FIG. 4 represents an electrical diagram of a first embodiment of the filter bank according to the invention with a central frequency of 5000 Hz;

FIG. 5 represents an electrical diagram of a first embodiment of the filter bank according to the invention with a central frequency of 6000 Hz;

FIG. 6 represents an electrical diagram of a first embodiment of the filter bank according to the invention with a central frequency of 7000 Hz;

FIG. 7 represents an electrical diagram of a part of the clock circuit according to the invention;

FIG. 8 represents an electrical diagram of a part of the low-pass filter circuit.

Description of preferred embodiments

With reference to the aforementioned figures, a bank of filters according to the invention can be applied to a SO.D.A.R. of triaxial type and known per se.

A SO.D.A.R. triaxial essentially comprises three independent antennas, not shown in the drawings, which send distinct signals into the atmosphere with respective frequencies or different frequency bands to improve the comprehensibility of the signals acquired by the SO.D.A.R system.

One of the antennas is oriented with a vertical axis and is used to detect minor frequency variations due to vertical wind, while the other two are inclined with respect to the vertical to detect greater frequency variations due to horizontal components.

The analysis of the reflected signals by means of suitable electronic means allows to collect data that are used to estimate the speed of the air masses, providing measurements of the wind and atmospheric turbulence, and indirectly information on the thermal field.

To improve the understanding of the data acquired by the SO.D.A.R. and to distinguish them from each other on the basis of the different operating frequencies, it is necessary to clean the received signals from the ambient noise and treat them with suitable filtering circuits with very selective response curves and with an almost unitary band attenuation.

To adapt the frequencies of the signals to particular sectors of application, the filters operate with two sets of different frequencies.

In particular, two sets of suitable frequencies Ft, Fm have been identified, respectively for terrestrial and marine application, more precisely:

Ft: low frequencies, which include 1600Hz, 1900Hz, 2300Hz; Fm: high frequencies, which include 5000Hz, 6000Hz, 7000Hz.

Since the frequencies inside the two groups are very close, it is necessary to use band-pass filters with very selective response curves, centered on each of the frequencies used and with almost unitary band attenuation.

The filter bank is essentially constituted by a motherboard, of a known type, not shown in the figures, on which input and output I / O coupling circuits with respective slots for secondary cards are installed.

This solution implies a series of practical advantages: greater mechanical strength, easier diagnostics, simplification of the layout of the single printed circuit board (PCB).

Furthermore, this solution allows to keep the clock generation and power supply section separate from the rest of the circuit.

The clock generation section, the IN / OUT couplings and the voltage reducers for the external power supply are installed on the circuit motherboard.

Integrated circuits produced by Linear Technology®, for example, can be used to make these filter cards.

These integrated circuits can be used for audio band filters and work with a technology called "switched capacitance" which allows, through the use of discrete components and a suitably generated external clock, the creation of filters even of the 12th order. (or similar) with cut-off frequencies and in-band gain that can be easily selected during the design stage.

The motherboard and the cards of the various filters were made with the PCB design technique, taking into account the ground plane method which serves to minimize interference from external electromagnetic fields thanks to the intrinsic shielding of the plate itself.

Figures 1 to 6 show embodiments of the filtering circuits intended to be installed on the motherboard.

The filter circuit 1 illustrated in FIG. 1 uses a 12th order Butterworth type filter and has a center frequency of 1600 Hz with a bandwidth of 130 Flz. Circuit 1 receives a 100 khlz clock S1 signal and has the lowest bandwidth. This is why it is used for the antenna of the SO.D.A.R. vertically oriented.

The filter circuit 2 illustrated in FIG. 2 includes a 14th order elliptical filter and is configured to have a center frequency of 1900 Flz, with a bandwidth of 316 Flz. Circuit 1 uses an input clock signal S2 of 100 kFlz, has a bandwidth greater than the previous one and for this reason it is used for one of the antennas with a certain inclination with respect to the vertical.

The filter circuit 3 illustrated in FIG. 3 is also a 14th order elliptical filter with central frequency equal to 2,300 kFlz with a bandwidth of 382 Hz. Circuit 3 receives a 200 kHz clock signal S3 in input and for this it is used for one of the antennas with a certain inclination with respect to the vertical.

The filtering circuit 4 illustrated in FIG. 4 is a 10th order elliptical filter and has a center frequency of 5 kHz with a bandwidth of 824 Hz. Circuit 4 receives a 500 kHz clock signal S4 in input.

The filter circuit 5 illustrated in FIG. 5 is a 10th order Butterworth filter and has a center frequency of 6 KHz with a bandwidth of 437 Hz. Circuit 5 receives a 500 kHz S5 clock signal in input.

The filtering circuit 6 illustrated in FIG. 6 is an 8th order elliptical filter and has a central frequency of 7 KHz with a passband width of 1153 Hz. Circuit 6 receives a 500 kHz clock signal S5 at its input.

FIG. 7 illustrates a diagram of the clock circuit, globally indicated Cc, intended to be inserted into the motherboard. The and output circuit supplies three clock signals at three different frequencies. The clock has a decisive influence on the frequency stability of the filters, and has been created using a particularly stable configuration consisting of a hybrid U4 quartz module with 2MHz input and a series of binary counters Ui, U2, U3 which provide the necessary frequencies for the correct piloting of the single filter cards.

The outputs of the clock circuit CC are realized by the different frequency division of the same single signal through the binary counters Ui, U2, U3 in order to obtain the same stability of the input signal for all three generated signals. The frequencies of the clock signals obtained are respectively 100, 200 and 500 KHz.

In FIG. 8 shows the electrical diagram of the clock with the various components used and an electrical diagram of the "feedtrough" circuit.

In all the embodiments of the filters, the external filtering cards or modules are easily replaceable on the motherboard, so as to make possible any possible update of one or more filtering cards, for example in the input frequency or in the passband of operation.

The electronic device described according to the present invention is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept expressed in the attached claims.

All the details may be replaced by other technically equivalent elements and the materials may also be different according to the requirements, without departing from the scope of the invention.

Even if the electronic device has been described with particular reference to the attached figure, the reference numbers and / or codes used in the detailed description of an embodiment and in the claims can be used to improve the intelligence of the invention and cannot constitute any limitation to the scope of protection claimed.

Claims (10)

R I V E N D I C A Z I O N I 1. A passband filter bank applicable to an electroacoustic monitoring system of atmospheric parameters (SO. D.A.R.), in which the system includes three antennas designed to send signals generated by respective electroacoustic transducers into the atmosphere and to receive signals in various ways reflected by the different zones of the boundary layer of the atmosphere, the filter bank being characterized by the fact that it comprises a motherboard on which a clock circuit is installed for the generation of signals of suitable frequency and a plurality of band-pass filters ( 1, 2, 3, 4, 5, 6) for the abatement of the spurious harmonics present in the signals acquired by the system, said filters (1, 2, 3, 4, 5, 6) being configured to operate with two series of differentiated frequencies (Ft, Fm) corresponding to two frequency bands in respective sectors of application. 2. Filter bank according to claim 1, in which said two series of different frequencies (Ft, Fm) are respectively intended for terrestrial and marine applications. 3. Filter bank according to claim 1, wherein said two series of frequencies (Ft, Fm) comprise a first series of low frequencies (Ft) respectively of 1600Hz, 1900Hz, 2300Hz and a second series of high frequencies (Fm) respectively of 5000Hz, 6000Hz, 7000Hz. 4. Filter bank according to claim 1, wherein said filters comprise secondary cards (1, 2, 3, 4, 5, 6) which constitute a band-pass filter for each signal input channel. 5. A filter bank according to claim 1, wherein said clock circuit (Cc) is configured to generate a single high stability clock signal, said single signal being divided by three binary counters (Ui, U2, U3 ) to obtain three differentiated clock signals able to guarantee the same stability of the unit signal. 6. A filter bank according to claim 1, wherein said motherboard has a plurality of I / O input and output coupling circuits with respective slots for secondary cards. 7. Filter bank according to claim 4, wherein said secondary filtering cards (1, 2, 3, 4, 5, 6) are configured to filter respective signals corresponding to different operating frequencies, and can be inserted in said slots in in order to simplify their replacement in case of malfunction or update, 8. Filter bank according to claim 4, wherein said filter cards (1, 2, 3, 4, 5, 6) constitute band-pass filters with selective response curves, centered on each of the frequencies used and with attenuation in substantially unitary band. 9. Filter bank according to claim 4, wherein said filter cards (1, 2, 3, 4, 5, 6) are configured to clean the signals from ambient noise outside the respective operating band and to separate the operating frequencies of the three system antennas in order to avoid the overlapping of the echo relative to the emitted signals. 10. Electroacoustic monitoring system of atmospheric parameters (SO.D.A.R.) of the triaxial type, comprising three transceiver antennas suitable for sending signals generated by respective electroacoustic transducers into the atmosphere and receiving the signals reflected from the different zones of the boundary layer of the atmosphere, characterized by comprising a filter bank consisting of a motherboard on which a clock circuit (Cc) is installed for the generation of three signal bands of suitable frequency and a plurality of band-pass filters (1, 2, 3 , 4, 5, 6) for the abatement of the spurious harmonics present in the signals acquired by the antennas, said filters (1, 2, 3, 4, 5, 6) being configured to operate with two sets of different frequencies (Ft, Fm) corresponding to two optimal frequency bands in respective sectors of application, said clock circuit being realized by means of a single circuit (Cc) able to generate a unitary clock signal with high stability, and being coupled to binary counters (Ui, l) 2, U3) to carry out a division of said unitary signal into differentiated clock signals to ensure the same stability for all the differentiated signals thus generated in order to avoid overlapping of the various reflected signals and in order to clean up the signals detected by the environmental noise outside the band of interest.