FR2634068A1 - BROADBAND RECEIVING ANTENNA - Google Patents

Abstract

The invention relates to an antenna for receiving waves in the VHF to HF and even metric bands. The antenna comprises an aerial A of the inverted cone type, placed in height above the ground and coupled to the receivers R, R 'to be fed by as many channels made of passive elements as there are receivers; each channel has its filtering cell L1-C1, L2-C2, its impedance adaptation circuit T1, T2 for coupling to the receiver R, R 'and possibly a resistor R1, R2 serving in particular to adjust, to a optimum reception level, the signal supplied to the receiver. Application to broadband reception antennas.

Description

Broadband reception antenna.

  The present invention relates to a broadband antenna, intended for reception at wavelengths ranging from the myriametric range (corresponding to the VLF band of the

  Anglo-Saxon literature) to the decametric range (corresponding to

  laying on the HF band of the Anglo-Saxon literature) and even metric (corresponding to the VHF band of the Anglo-Saxon literature). There are receiving antennas operating from VHF to VHF. But these

  Antennas are active antennas, that is, they

  active, non-linear components, such as

  tors. These active antennas have various disadvantages - they require a power supply, - because of their relatively high effective height, they are very sensitive to jammers constituted, for example, by a neighboring transmitting antenna, - they have significant non-linearities of the fact

  active components used for the adaptation of

  Moreover, these active components generate a high noise, they are very sensitive to disturbances due to

  electromagnetic pulses of high amplitude.

  The object of the present invention is to avoid or, for the

  least, to reduce these disadvantages.

  This is achieved by the association of a special aerial

  designed to present a broad band of frequencies for

  sation, and studied flights to achieve optimal coupling

  between the aerial and the receivers to connect to this aerial.

  According to the present invention there is provided a broadband receiving antenna, characterized by the combination of an inverted cone type aerial, a conductive support for placing the cone top elevation above the ground and a circuit Passive adaptation with n channels (n: number

  positive integer respectively) relating to n frequency bands

  reception, each lane being coupled to the air and

  in series, a filter cell for isolating its reception frequency band and an impedance matching circuit. The present invention will be better understood and others

  characteristics will appear in the alde of the description

  FIG. 1 is a perspective view of an antenna according to the invention; FIG. 2 is a partial view in section of the antenna according to FIG. 1; - Figure 3, the electrical diagram of the antenna according to the

figure 1.

  In the different figures, the corresponding elements

  have been designated by the same benchmarks.

  Figure 1 shows an antenna according to the invention, the aerial, A, comprises an inverted cone, B, surmounted by a roof sheet, T; the cone rests on a foot P. The inverted cone, B, of the aerial is made by means of eight metal rods B1 to B8 regularly arranged along generatrices of the cone; the cone is at an angle of 33 degrees and the stems that constitute it have a length of 1.50 meters. The choice of an aerial of the inverted cone type is due to the fact that the "thick" structure of such an aerial ensures a broadband

Operating.

  The roof sheet, T, is formed of eight metal rods of one meter, arranged in a star and fixed by rivets on the upper ends of the rods B1 to B8. The presence of this roof sheet can greatly increase the capacity

internal air.

  The rigidity of the cone and the roof sheet is reinforced by a vertical metal rod, D, arranged along the axis, not shown, of the cone; this rod D is fixed, at its upper end, to the center of the star formed by the roof sheet, the fastening, at their lower end, the rods of the inverted cone B and the rod D will be specified using the figure 2. It should be noted that the rod D being entirely disposed to

  inside the cone, does not participate in radio activity.

  electric air. The foot P comprises a vertical metal cylinder P1, 1.20 meters high and 18 centimeters in diameter surmounted by a cover, P2, whose role is to ensure the mechanical connection between the cylinder and the air while the electrically insulating from each other; the constitution of the lid P2 will be specified with the help of Figure 2. The cylinder P1 is fixed to the ground via a metal base, P3, formed

  horizontal plate and four vertical brackets

  on the lower end of the cylinder P1. Use

  foot, such as the foot P. to raise the aerial by

  on the ground, was determined by the desire to increase the

  antenna, ie the ratio of the voltage available at the antenna feed point to the

  incident field in the vicinity of the antenna.

  FIG. 2 is a partial view, in a vertical section plane passing through the stem D, of the foot P and the bottom of the aerial

  A of the antenna according to Figure 1. For facilities of representation

  a cut, indicated by two lines broken in center lines, has reduced the length of the foot on the drawing by eliminating the central part which is identical to the top of the

  lower part and at the bottom of the upper part of the foot.

  Figure 2 shows the metal plate of the base P3 which is welded to the lower end of the cylinder P1 and which rests on the ground. A fastening assembly, not shown, is associated with the base, it is made of threaded rods which vertically cross the plate of the base P3, bolts referred to the threaded rods and bearing on the plate, and blocks of

  concrete cast in the soil and in which the

  lower mits of the threaded rods.

  FIG. 2 also shows the constitution of the upper part of the foot P, with the cover P2 traversed by the rods of the aerial A and by a spark gap Y, with a printed circuit G whose electrical diagram is shown in FIG. with links between the aerial, the printed circuit, the cylinder Pi and two coaxial output plugs of the antenna, S1-S2, S3-S4, which pass through the wall of the lower part of the cylinder PI. The lid P2 comprises a horizontal metal plate J which covers an insulating plate K placed on a flange secured to the upper end of the cylinder Pi; the fixing of the plate K on the flange on the one hand and the plate J on the plate K on the other hand is provided by means of screws not shown. The spark gap Y, whose housing is insulating, is closed by a cap accessible above the plate J; the spark gap Y is in electrical contact, by one of its terminals, with the plate J and, by the other of its terminals, with the cylinder PI to which it is connected by means of a metal support welded on the inner wall of the cylinder PI. The printed circuit G, which is arranged in the cylinder P1 in the immediate vicinity of the cover, is an adaptation circuit intended to allow the coupling between the aerial A and receivers to be connected to the sockets S1-S2 and S3-S4; the adaptation circuit carried by the printed circuit is in electrical contact on the one hand at a point N with the tip of the cone of the air through a connection H which is none other than the extension of the rod D below the lid P2 and secondly, over the entire periphery M of the printed circuit, witho the inner wall of the metal cylinder P1; two cables Q1, Q2 provide the

  connections between the printed circuit G and the sockets SI-S2, S3-S4.

  It should be noted that the rods such as BI, B5 and D pass through the metal plate J through holes whose walls they are scdées so as to give good rigidity to the air and ensure a strictly identical potential at the ends

lower of all stems.

  FIG. 3 is an electrical diagram of the antenna according to

  FIGS. 1 and 2 with, in addition, two resistors R and R 'connected

  respectively on sockets S1-S2 and S3-S4; these two resistors are receivers intended to be connected to the antenna. FIG. 3 represents the aerial A of FIGS. 1 and 2 with its terminals N and M respectively corresponding to the point

hot and to the ground of the antenna.

  Between the M and N terminals is connected the spark gap Y, which has a parasitic capacitance of 5 pF. This spark gap is designed to short circuit, and thus preserve the

  components downstream of it, when it detects an "aggression

  This detection occurs when the voltage at the terminals of the eclator exceeds the threshold voltage of the spark gap, the ionization of the gas contained in the spark gap tube is then produced. an electric arc between the terminals of the spark gap and this arc which forms

  short circuit persists for the duration of the disturbance.

  Between the terminals M and N are also connected two paths which lead respectively to the resistors R and R '

appearing receivers.

  The first lane, which will be called the high lane, is designed

  to arrive at a receiver working in the 2-30 MHz band.

  It comprises, in series from terminal N to terminal M, a resistor R1 of 330 ohms, a capacitor Cl of 220 pF and an inductance Ll of 100 microhenrys; an impedance matching transformer, T1, of 4 / ia primary sound, a terminal of which is grounded, connected in parallel to the inductance L1 and its secondary, of which one terminal is grounded, connected to the resistance R; a capacitor C 'drawn in broken lines represents the parasitic capacitance, of the order of

  pF, which exists at the transformer primary Ti.

  The second channel, which will be called the low channel, is designed to lead to a receiver working in the -100 kHz band. It comprises, in series from terminal N to terminal M, a resistance R2 of 10 kilo-ohms and an inductance L2 of 0.7 henry. A capacitor C2 of 100 pF is connected in parallel with the inductance L2 as well as the primary of an impedance matching transformer, T2, with a ratio of 25/1; the secondary of the transformer T2 of which one of the two output terminals is grounded, is connected to the resistor R2. In the arrangement according to Figure 3 the resistors R1 and R2 have several functions - adjust the level of the signal supplied to the receiver connected to the channel, so that this receiver operates at the signal level

  optimum, that is to say with a level sufficient to allow

  be listening but not more, so as not to have too much noise,

  - to protect the flight against residual voltage

  site not stopped by the spark gap when, for example, an aggression

by lightning.

  It should be noted that the resistors R1i and R2 are in fact

  two sets of resistances, the values of which

  their totals are those indicated above, and that mobile short-circuits make it possible to short-circuit all or part of the resistors R1 and R2 so as to optimize the

  reception according to the site where the antenna is located.

  The filter cell formed by the capacitor C1 and the inductance L1 is intended to isolate the high channel of the low channel by providing high-pass filtering, while the filter cell L2-C2 isolates the low channel of the high channel.

  forming a plug circuit substantially centered on 20 kHz.

  It should be noted that in the assembly according to FIG.

  their respective values for L1, L2 and C2 respectively take into account the parasitic inductances at the primary terminals of the transformers T1 and T2 and the parasitic capacitance at the terminals

of the primary transformer T2.

  The antenna just described has an omnidirectional azimuth radiation pattern for vertical polarization of the electric field and a single lobe pattern, with a zero on the vertical axis, for vertical polarization of the electric field. With regard to the effective height of the antenna, that is to say the ratio V / E between the voltages supplied at the terminals of the receivers and the module of the incident field in the vicinity of the antenna, the following results have were obtained: - effective height in the band 20 to 100 kHz -40 to -35 dB.m effective height in band 2 at 30 MHz -13 to -8 dBm these values, which are compatible with the original noise levels galactic, atmospheric and industrial received by the air, provide a good reception sensitivity while minimizing the influence of any existing jammers at

neighborhood of the air.

  In addition it should be noted that the antenna, which has just been described, can be used with a receiver working in the lower part of the metric band subject to an adaptation of the high channel to such use; it should also be noted that this antenna has good protection against aggression

  electromagnetic field and, because of the passive nature of its

  until the spark gap Y is triggered, presents a

  high linearity of operation.

  The present invention is not limited to the example of

  written, this is how the number of channels can be reduced to 1 or be greater than 2; each channel is determined according to the receiver for which it is intended and the isolation to achieve compared to other channels. Similarly, the antenna may not include a spark gap or use in its tracks, the pitch cells and different impedance matching circuits

  of those described using Figure 3.

Claims (4)

  A wideband reception antenna, characterized by the combination of an aerial (A) of the inverted cone type (B), a conductive support (P) for placing the vertex (N) of the cone in elevation with respect to the ground (S) and a passive matching circuit having n volts (n positive integer) relating respectively to n receiving frequency bands, each   track being coupled to the overhead line and comprising, in series, a   filtering unit (C1-LI, C2-L2) for isolating its reception frequency band and an impedance matching circuit (T1, T2).   Antenna according to claim 1, characterized in that   at least one of the n channels has in series an attenuated element nuateur (R1, R2).   Antenna according to one of the preceding claims,   characterized in that it comprises a spark gap (Y) coupled to   aerial to provide protection against lightning.   Antenna according to one of the preceding claims,   characterized in that the aerial (A) comprises a roof (T) constituting   killed by a plane element disposed at the base of the inverted cone (B) of the aerial to increase the effective height and capacity equivalent of the aerial.