RU2625631C1 - Small-size quickly retunable antenna - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: antenna contains the coaxial conductor section parts 8 and 9, separated by the reference section 10, the radiator 12 is connected to the end face central core 11 of the part 8, as a result the end face 11 cross-section is the antenna input. The part 9 is located near the conducting surface 13 at the distance of less than the quarter of the smallest wavelength range, the end face 14 of the part 9 external surface is closed on the conductive surface 13, as a result of which the outer surface of the part 9 in conjunction with the conductive surface 13 forms the shorted stub 15. The outer surface of the reference section 10 is the non-grounded terminal of the shorted stub 15, the closest to it local area 16 of the conductive surface 13 is the grounded terminal of the shorted stub 15. The gap 17 between the terminals 10 and 16 is the input of the shorted stub 15, as a result, the cross-section of the part 9 end face 14 is the antenna path input. The part 8 is made in the form of the vertical spiral, and the shorted stub 15 contains the contacts 18, providing the possibility to close it at the specified length. The vertical conductor 19 with contacts 20 along its length is connected to the non-grounded terminal 10 of the stub 15, providing the possibility to close the conductor 19 to different turns of the part 8 spiral.

EFFECT: reduction of the clearance limitations and increase of the operating frequency range overlapping coefficient by the radio transmitter capacity credit criterion, going to the antenna, reduction of the requirements for placing the antenna at the facility sites.

2 cl, 10 dwg

Description

The invention relates to the field of radio communication antennas and can be used to create, mainly, small-sized, vertically polarized, quickly tunable in a wide frequency band antennas for various purposes, mainly for mobile and stationary means of sea and ground-based operation, preferably in NE, KB and VHF bands.

As such antennas, mainly used are pin-type antennas in the form of a conductive pin, the input terminal of which is located either directly above the conductive surface or above the conductive column. In addition, there are a number of other versions of these antennas. These antennas, to a certain extent, are identical in directionality of the radiated field (they have an almost circular radiation pattern in the horizontal plane and one- or two-petal diagrams in the vertical plane). Due to the weak directivity of these antennas and insignificant losses in the radiating elements for the criterion of their operability, in the overwhelming majority of cases, the fraction of the nominal transmitter power that goes into the antenna is selected. An important, but difficult to overcome problem of developing such antennas is the resolution of contradictions between minimizing their dimensions and expanding the working frequency band according to the specified criterion. The principle of operation of such antennas is described in a number of sources, for example, in [1, 2, 3, 4].

As analogues to the proposed invention include the following inventions:

- Inductive-capacitive antenna [5]. The antenna contains two main elements, one of which is made in the form of a flat inductor, and the other is in the form of a conductive surface on a dielectric pipe, which performs the function of a capacitor plate.

- Small-sized capacitive antenna with a matching inductor [6]. In this antenna, unlike the previous one, the connection points of the conductive cylinders are changed and a tuned coil is introduced.

- The antenna [7] contains a capacitive element in the form of two coaxially arranged conductive cylinders and an inductor.

The disadvantage of these analogues is the complexity and unreliability of the design, especially in conditions of vibration, wind, ice and temperature loads.

The closest analogue (prototype) of the claimed invention is an antenna with adjustable current distribution [1].

The prototype consists of a vertical part and a rectilinear horizontal part of a segment of a coaxial conductor, divided by a conditional section, while an emitter is connected to the central core of the end of the vertical part, as a result of which the cross section of the end of the vertical part is an antenna input, while the horizontal part is located near the horizontal conductive underlying surface on less than a quarter of the smallest wavelength of the working range, and the outer surface of the end of the horizontal part is closed to the horizon a conductive underlying surface, as a result of which the horizontal part together with the underlying surface forms a short-circuited loop (hereinafter referred to as the loop), while the external surface of the conditional section is an ungrounded loop terminal, and the nearest local area of the underlying surface is a grounded loop terminal, as a result of which the gap between these terminals is the loop input, and the cross section of the end of the horizontal part is the input of the antenna path.

An equivalent electrical circuit of the prototype is shown in FIG. 1. In this drawing, the vertical part of the coaxial conductor (CP) 1 is represented by conductor 1 (hereinafter referred to as conductor 1), the lower end of which is closed to the horizontal conductive surface 2 through reactance 3 equal to the resistance X of the loop input, and the upper end of conductor 1 is connected to terminal 4 of the antenna input 5, to the other terminal 6 of which is connected the lower end of the vertical conductor 7 (hereinafter - conductor 7), which is a prototype emitter.

Considering that the prototype antenna is slightly directional and that there are no absorbing elements in it, the criterion for setting up such an antenna in the transmission mode may be the fraction η _{a of the} nominal transmitter power going to antenna input 5 (Fig. 1).

Using the equivalent electrical circuit (Fig. 1), we show that for fixed sizes of conductors 1 and 7, the working strip of the prototype and, therefore, the coefficient of overlap of the frequency range have significant limitations.

.Suppose that η _a ≥0.45. Denote the standing wave coefficient (SWR) at the antenna input 5 as K _a . In accordance with the known expression [2]

.

Based on this expression, this criterion will be fulfilled at any frequency ƒ for K _a (ƒ) ≤MK (ƒ) = 6.74, where MK (ƒ) is the maximum allowable value of SWR at a frequency.

As an example, suppose that in the equivalent circuitry of the prototype, the length of conductor 7 is 2 m with a diameter of 30 mm, and the length of conductor 1 is 1 m with a diameter of 60 mm. We define the minimum frequency (maximum wavelength) at which the adopted tuning criteria is achieved.

Using the MMANA computer simulation program [8], we determine that when the resistance X changes from minus to plus infinity, the lower frequency limit of tuning such an antenna according to this criterion will correspond to the value X = X ₀ = 403.5 Ohms and will be mƒ ₀ = 8 , 4 MHz (wavelength λ ₀ = 12.908 m); and the train corresponding to the value of X ₀ will have a length S = 23.24 m.

However, real loops have some losses, as a result of which the lower frequency limit will change somewhat. So, for example, when using a loop of the indicated length with a wave resistance of w = 200 Ohms and with the same losses as in the cable RK-50-7-22, we will get [2] close to real dependences K _a (ƒ), given on FIG. 2 and 3 (solid line). The same drawings show their maximum permissible values MK (ƒ) (dotted line) that satisfy the selected criterion η _a .

From these graphs it can be seen that with an almost zero signal bandwidth, the minimum frequency (Fig. 2) m (ƒ) = 9.6 MHz (maximum wavelength Mλ = 31.25 m). The maximum frequency (Fig. 3) is Mƒ = 59.159 MHz (the minimum wavelength is mλ = 5.071 m). However, this band [mƒ; Mƒ] is not continuous, because inside it there are only ten very narrow working sections, where K _a (ƒ) is below the maximum permissible limit MK (ƒ):

- 14.087 MHz with a band of 175 kHz;

- 19.866 MHz with a band of 471 kHz;

- 25.61 MHz with a band of 966 kHz;

- 29.087 MHz with a band of 92 kHz;

- 31.179 MHz with a band of 1745 kHz;

- 36.672 MHz with a band of 2289 kHz;

- 42.595 MHz with a band of 990 kHz;

- 47.611 MHz with a band of 1277 kHz;

- 53.322 MHz with a band of 770 kHz;

- 54.694 MHz with a band of 109 kHz.

.The total total band of these working areas is the maximum possible working band of the prototype Δƒp = 8.6 MHz. Therefore, the maximum possible overlap coefficient of the frequency range is

.

Summarizing the result, it should be noted that the adopted ratio of the sizes of conductors 1 and 7 (Fig. 1) is optimal, because gives the smallest dimensions and the largest coefficient of overlap of the frequency range of the prototype relative to the minimum frequency mƒ ₀ regardless of the specific values of the tuning criterion.

Since the total height of this prototype H = 3 m, the loop length S = 23.24 m, and the maximum wavelength Mλ = 31.25 m, then Mλ / H = 10.42, a Mλ / S = 1/345, t .e. (due to electrodynamic similarity [9]), the prototype height H will be greater than Mλ / 10.42, and the loop length S will be greater than Mλ / 1.345, while the coefficient of overlap of the operating range ξ will be less than Mξ = 0.896.

It must be added that on a number of objects it is impossible to apply the prototype loop design due to the lack of a conductive surface in the form of a horizontal plane.

Thus, the disadvantages of the prototype are: large dimensions, a small coefficient of overlap of the operating range and the presence of application restrictions.

The objective of the invention is the improvement of the antenna device.

Technical Results:

- reduction of size restrictions and increase in the coefficient of overlap of the operating frequency range according to the criterion "the share of the rated power of the radio transmitter leaving the antenna", partial elimination of application restrictions;

- reduced requirements for the placement of the antenna at the installation sites.

To achieve the first claimed technical result in an antenna of small-sized fast reconfigurable (Fig. 4), containing parts 8 and 9 of a segment of a coaxial conductor, divided by a conditional section 10, a radiator 12 is connected to the central core of the end face 11 of part 8, as a result of which the end section 11 is an antenna input . Part 9 is located near the conductive surface 13 at a distance of less than a quarter of the smallest wavelength of the operating range, the end 14 of the outer surface of part 9 is closed to the conductive surface 13, as a result of which the outer surface of the part 9 together with the conductive surface 13 forms a short-circuit loop 15. In this case, the outer surface section 10 is an ungrounded first terminal of a short-circuited loop 15, the closest local area 16 of a conductive surface 13 to it is a grounded second terminal of a short-circuit utogo loop 15. The gap 17 between the terminals 10 and 16 is input to the shorted loop 15, as a result of end section 14 of portion 9 is input antenna path. Unlike the prototype, part 8 is made in the form of a vertical spiral, and the short-circuited loop 15 contains contacts 18, which make it possible to short circuit along a given length, while a vertical conductor 19 is connected to the non-grounded terminal 10 of loop 15 with contacts 20 along its length, which provide the possibility of short-circuiting the conductor 19 to various turns of the spiral of part 8, while the conductive surface 13 has an arbitrary shape determined by the installation object of the antenna.

To achieve the second claimed technical result, an option of a small-sized fast reconfigurable antenna (Fig. 5) contains parts 8 and 9 of a segment of a coaxial conductor divided by a conditional section 10, so that a radiator 12 is connected to the central core of the end face 11 of part 8, as a result of which the end section 11 is an antenna the entrance. Moreover, part 9 is located in isolation from the conductive surface 13, and its outer surface is a direct wire of a short-circuited loop 15, while the cross-section of the end 14 of part 9 is the input of the antenna path, and the outer surface of a conventional section 10 is an ungrounded terminal of a short-circuited loop 15. In contrast to the prototype to the outer surface of the end face 14 is connected one end of the conductor 21 located at a distance of less than a quarter of the wavelength from part 9, so that the second end of the conductor 21, located opposite the conditional cheniya 10 forms a grounded terminal 22, closed at the nearest local region 16 of the conductive surface 13, whereby the gap 17 between the terminals 10 and 22 is input to the shorted loop 15, which comprises terminals 18 that provide an opportunity loop circuit 15 by a predetermined length. The cross section of the end 14 of part 9 is the input of the antenna path, while part 8 is made in the form of a vertical spiral, and a vertical conductor 19 with contacts 20 along its length is connected to the ungrounded terminal 10 of the short-circuited loop 15, making it possible to short-circuit the conductor 19 to various turns of the spiral of part 8 , and the conductive surface 13 has an arbitrary shape determined by the installation object of the antenna.

To clarify the principle of operation of the proposed device, we first consider the properties of the input resistance Z _{Σ of the} prototype (using its equivalent electrical circuit (Fig. 1) with the previously indicated dimensions of the conductor (pin) 7 (2 m) and conductor 1 (1 m). Resistance Z _Σ ( between terminals 4 and 6) is the sum of the resistances of pin 7 and conductor 1. As an example, Fig. 6 shows the dependences of the real (R _k ; R _h ) and imaginary (X _k ; X _h ) parts, respectively, of the column resistances and pin from frequency at zero loop length (S = 0; X = 0) Thin lines correspond to the real part, and thick lines to the imaginary. Solid lines correspond to the parameters of the pin and dashed lines correspond to the parameters of the column. Calculations were performed using the MMANA program. Since the program used does not allow finding the column resistance, the resistance of the entire antenna was determined first, then (using the same program) the resistance of the pin was determined, and the resistance of the column was calculated as the difference of these resistances. From the graphs of FIG. Figure 6 shows that in the low frequency region the sum of the active components of both resistances is negligible, and the absolute value of the sum of the reactive components is extremely large, which does not allow us to achieve sufficient matching of the antenna with the accepted wave impedance standards w (50 and 75 Ohms) of coaxial RF cables.

In the proposed device, the conductor 1 (Fig. 1) is made in the form of a spiral decelerating structure 8 (Fig. 4 and 5) with a deceleration factor N. As a result, the frequencies corresponding to the resistances R _k ; X _k will be N times smaller, and the frequencies corresponding to the pin resistances R _h ; X _h will not change, as shown in the graphs of FIG. 7.

So, with N = 6 (Fig. 7) we get:

R _k (ƒ = 4,5) = R _k (ƒ = 27) = 51.7 Ohm - the value of the real part of the column resistance;

X _k (ƒ = 4,5) = X _k (ƒ = 27) = 150 Ohm - the value of the imaginary part of the column resistance;

R _h (ƒ = 4.5) = R _h (ƒ = 27) = 0.46 Ohm - the value of the real part of the resistance of the pin;

X _h (ƒ = 4,5) = X _h (ƒ = 27) = - 1290 Ohm - the value of the imaginary part of the resistance of the pin.

Based on these results, the total antenna resistance at a frequency of ƒ = 4.5 MHz will be: R _Σ = 52.2 Ohms, X _Σ = -1140 Ohms, which, however, due to the too large absolute value of the imaginary part of the obtained resistance is not will achieve an acceptable agreement with the resistance w = 50 Ohms. Compensation of the imaginary part by introducing the reactive element into the pin or into the antenna path leads, as is known, to breaking the integrity of the path, which complicates maintainability, negatively affects the reliability, cost and design of the product. The introduction of the loop 15 (Fig. 4 and 5) will allow you to compensate for the indicated reactivity by changing its electrical length due to the closure of a specific contact 18. However, a change in the electric length of the loop will also change obtained by introducing a slowdown structure with a deceleration factor N = 6 active resistance R _k = 51.7 Ohms. Therefore, in order to obtain a combination of active and reactive components that satisfy the selected criterion (η _a ≥0.45), it is enough to select, by closing the mentioned contacts, the combination of the electric length of the loop and the connection of a certain turn of the slowing structure with a vertical conductor 19. that the retardation structure will change the active resistance not only due to the deceleration coefficient, but also due to the radiation intrinsic resistance, which significantly complicates the already sufficient layer reliable calculations of such antennas.

In view of the aforementioned, in order to (with all the mentioned factors) show the possibility of obtaining the indicated combination, experimental studies were carried out on a variant of the proposed antenna (Fig. 5) on the model (Fig. 8) of the same overall height (3 m) as a given example of a prototype.

The model was located on a flat conductive roof 13 (underlying surface) of the first floor of the antenna stand in a radio-transparent setting. The spiral retardation structure 8 had a height of 1 m and consisted of 46 turns of a spiral mounted on a foam-plastic column 23 of square section with a rib length of 13 cm. A copper foil tape mounted on a dielectric support 24 was used as a vertical conductor 19. Loop length 15 was 6.6 times smaller than that of the prototype, and was 3.5 m. Instead of many contacts 18 of the loop 15 and contacts 20 of the vertical conductor 19, two special clamps were used, one of which alternately closed the turns of the decelerating structure 8 on ovodnik 19, and the other closed the cross section of the loop 15 at various distances, after 30 cm, along its length. A segment of a coaxial conductor (feeder path of the antenna), consisting of a decelerating structure 8 and a straight wire 9 of a loop 15, was a coaxial cable RK-50-7-22 with a total length of 34.5 m (spiral coils - 31 m, a straight wire 9 -3.5 m). To the end 14 of the straight wire 9 was connected a coaxial socket SR-50-163PV for connecting measuring instruments. The return wire 21 of the loop 15 consisted of a cable braid RK-50-7-22. A vertical radiator 12 with a length of 2 m and a diameter of 10 mm was connected to the central core of the end face 11 of the coaxial conductor, which forms a slowing structure 8, in the form of a conductor suspended on a die line from the ceiling of the stand. Straight 9 and return 21 wires of the loop 15 were located one above the other at a distance of 1 cm, and the return wire 21 was located at a distance of 4 cm from the underlying surface 13, while one end of the return wire 21 was closed to the outer surface of the end face 14 of the straight wire 9, and the other end 22 is located on the local region 16 of the surface 13 closest to it. The loop 15 itself was installed above the surface 13 using dielectric supports. Therefore, the resistance X (Fig. 1) corresponded to the resistance at the input 17 of the loop 15 (Fig. 8).

During the study, measurements were made of the dependence of the SWR on the frequency (K _νx (ƒ)) at the input of the antenna path (end 14 in Fig. 8) in the range from 3 to 90 MHz for all possible combinations of contact closures 18 and 20 (Fig. 8). Then, according to the dependences K _νx (ƒ) and the previously measured dependences of the attenuation B (ƒ) dB of the antenna feeder path, consisting of a decelerating structure 8 and a straight wire 9 of loop 15, the following dependences were determined:

- зависимость модуля коэффициента отражения на входе тракта (на торце 14 фиг. 8);

- the dependence of the modulus of the reflection coefficient at the input of the path (at the end 14 of Fig. 8);

η _AFU (ƒ) = 1-g _νx (ƒ) ² - dependence of the share of the rated power of the transmitter allocated at the input of the path (at the end 14 of Fig. 8);

- зависимость модуля коэффициента отражения на входе антенны (на торце 14 фиг. 8);

- the dependence of the module of the reflection coefficient at the input of the antenna (at the end 14 of Fig. 8);

- зависимость доли номинальной мощности передатчика, выделяемой на входе антенны (на торце 14 фиг. 8);

- the dependence of the share of the rated power of the transmitter allocated at the input of the antenna (at the end 14 of Fig. 8);

η _PID (ƒ) = η _AFU (ƒ) ^_ η _A (ƒ) is the dependence of the share of the rated transmitter power released in the feeder path.

An analysis of the results showed that to ensure the selected criterion, it is sufficient to use 31 contacts 20 to close the turns of the spiral and 9 contacts 18 to close the loop.

In FIG. 9 (in the range of 4-45 MHz) and FIG. 10 (in the range of 45-90 MHz) the following graphical dependences of the results are obtained for the optimal combinations of contacts 18 and 20 in comparison with the selected criterion η _a (dashed line):

- доля номинальной мощности передатчика, выделяемая на входе фидерного тракта предложенной антенны;

- the share of the rated transmitter power allocated at the input of the feeder path of the proposed antenna;

η _A (ƒ) is the fraction of the rated power of the transmitter allocated at the input of the proposed antenna;

- доля номинальной мощности передатчика, выделяемая в фидерном тракте предложенной антенны.

- the share of the rated power of the transmitter allocated in the feeder path of the proposed antenna.

From the graphs of FIG. Figure 9 shows that the allocated shares of the rated power of the transmitter with the configured layout in the range up to 45 MHz are:

- at the input of the antenna - from 49 to 55%;

- at the entrance of the tract - from 67 to 90%;

- in the feeder - from 15 to 40%.

From the graphs of FIG. 10 it follows that in the high-frequency region, more than 45 MHz, the allocated shares of the nominal power with the tuned layout (in the presence of significant emissions due to radio interference that occurred in some parts of the frequency range) average:

- at the input of the antenna - 45%

- at the entrance of the tract - 90%;

- in the feeder - 45%.

In addition, the minimum tuning frequency (not shown in the graphs) was 3.4 times less than that of the prototype, and amounted to about 2.8 MHz. At the same time, when evaluating the minimum prototype tuning frequency, losses in the feeder path were not taken into account, and when they are taken into account, the minimum prototype tuning frequency will increase.

Since the minimum frequency of the prototype of the same height with a loop of optimal length (23 m) is 3.4 times higher than the minimum tuning frequency of the proposed cable with a length of 3.5 m, due to the electrodynamic similarity, the dimensions of the proposed device will be much smaller. And to create a prototype with a minimum frequency that satisfies the selected criterion, it is necessary to increase its height and length of the loop by 3 times.

будет больше в 234 раза.Since the minimum tuning frequency of the proposed antenna is mƒ _A = 2.8 MHz, and the continuous tuning band (graphs of Figs. 9 and 10) extended to a frequency of Mƒ _A = 55.3 MHz, i.e. was Δƒ _A = 52.5 MHz, then the overlap coefficient of the frequency range of the proposed antenna

will be 234 times more.

In addition, the alternative construction of loops will eliminate a number of restrictions on the ability to install and use the antenna at various sites.

Thus, the goal is achieved due to the fact that, in comparison with the prototype, the use of the proposed will reduce the size, increase the coefficient of overlap of the working range and remove a number of restrictions on the possibility of installation on objects.

Bibliography

1. Belousov S.P. Medium-wave antennas with adjustable current distribution // Moscow: Communication, 1974, p. 22, fig. 2.9; from. 26, fig. 2.13; from. 33, fig. 31 and 32.

2. Lavrov A.S., Reznikov G.B. Antenna-feeder devices // M .: Sov. Radio, 1974, p. 129.

3. Vershkov M.V. Ship antennas ”// L: Shipbuilding, 1978, § 2.8.

4. Nadenenko S.I. Antennas // Moscow: State. Ed. literature on communications and radio, 1959, §7.4.

5. RF patent No. 2383974.

6. RF patent No. 2470424.

7. US Patent No. 6956535.

8. Goncharenko I.V. Antennas KB and VHF // Moscow: RadioSoft, 2004, 128 p.

9. Fradin A.Z., Ryzhkov E.V. Measurement of the parameters of antenna-feeder devices // Moscow: Communication, 1972, p. 273.

Claims (2)

1. An antenna containing a segment of a coaxial conductor (KP), divided by a conditional section into first and second parts, while an emitter is connected to the central core of the end face of the first part of the KP, and the end section of the end of the first part is the antenna input, the second part of the KP is located above the conductive surface, and the outer surface of the second part of the KP forms a straight wire of a short-circuited loop, the outer surface of the conditional section is the first terminal of the loop, the closest local area of the conductive surface to it forms the second terminal loop, the gap between the first and second terminals is the loop input, the end section of the second part of the KP is the input of the antenna path, characterized in that the return cable loop is made of a conductor, one end of which is closed to the outer braid of the end of the second part of the KP, and the other end is closed to the second loop terminal, while the first part of the KP is made in the form of a spiral, and the short-circuited loop contains contacts, providing the possibility of its closure along a given length, a vertical conductor with contacts is connected to the first terminal of the loop of its length, providing the possibility of the conductor circuit on the different turns of the spiral, the conductive surface has an arbitrary shape. 2. The antenna according to claim 1, characterized in that the return wire of the short-circuited loop is a conductive surface.

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