JPS6080780A - Antenna device for measuring azimuth - Google Patents

Abstract

PURPOSE:To measure azimuth with good accuracy and sensitivity by disposing plural antennas at an equal interval on a circumference and taking out of one transformer while changing over successively and cyclically two antennas as a set. CONSTITUTION:A pair of antennas 1, 2 at a space S is provided and a transformer 301 is connected thereto. The voltage corresponding to the phase difference between the two antennas is taken out to the secondary side output and the sum (phase sum) output of the two antennas is taken out of the mid-point on the primary side. When the antennas 1, 2 are rotated along the circumference, the phase difference output determined by the space S between the antenna is obtd. in proportion to the cos of the angle theta between the centers of the two antennas and the incoming direction of radio waves. The phase of the sum output is changed by about 90 deg. and is synthesized with the differential output in the same phase (or in the opposite phase) to determine a sense. In actuality, the antennas are arranged on the circumference and each pair of the antennas are cyclically and successively changed over by an antenna selector 401, by which the outputs of the difference and the sum are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an antenna device used in a radio direction finding device (hereinafter abbreviated as direction finding) that measures the arrival direction of radio waves, that is, the radio direction.

In a conventional directional search using an Atcock antenna, it was impossible to increase the antenna diameter to more than one wavelength even if the antenna element was a multiplex element. On the other hand, with Doppler square probes and Uhlen-Weber square probes, the antenna aperture can be set to any diameter of one wavelength or more, which improves measurement accuracy by widening the aperture surface.

It has the characteristics of improving errors caused by polarization plane fluctuations, stabilizing i<+1+ constant azimuth fluctuations, and reducing the effects of nearby disturbing objects.

The large-diameter antenna device of the present invention, which has a pair of two antennas, can obtain the same characteristics as the above-mentioned wide aperture area, and by using this antenna device, it can be used for Doppler direction finding and Uhlen-Weber direction finding. It is possible to obtain a high-performance direction finder with a simple structure by using the ready-made technology of the conventional goniometer direction finder without requiring a complicated structure such as the above.

Figure 1 shows this principle. A pair of antennas 1 and 2 with a spacing S is provided, a transformer 3 is connected to the output of the antenna, and the secondary output is connected to the phase difference between the two antennas. A voltage corresponding to the sum (phase sum) of the two antennas is output from the midpoint of the primary side of the transformer.

Assuming that radio waves arrive from the direction shown in Figure 1, and antennas 1 and 2 are rotated along the circumference of the aperture, the difference output terminal of the transformer 301 has two antennas. A phase difference output as shown in Fig. 2 is obtained, which is proportional to the angle θ between the center of It will be done.

This is the same directivity characteristic as when an antenna with a spacing S is rotated around the center of this aperture, and is independent of the size of the aperture of the rotated antenna.

Figure 3 shows the well-known Atcock antenna finger πS concurrency sl++ (>・弼θ) using the ratio S/λ of the antenna spacing S and the wavelength λ as a parameter.
It is clear that the phase difference output when two antennas with a spacing S are rotated by KG on the circumference will have the same directivity characteristics as shown in FIG. 3.

The phase of this output voltage is determined by the relationship between the direction of the arriving radio wave and the rotation direction of the antenna, and the phase differs by 180° depending on whether the two directions are the same or the opposite direction.
This is similar to the fact that the phase of the output of an atconch antenna differs by 1800 degrees depending on the direction of arrival.

Doppler direction searching uses the azimuth component itself, which determines whether the frequency change or phase change is positive or negative depending on the direction of arrival, and therefore does not require sense determination. However, in the present invention, the azimuth component is extracted as a voltage, so no separate sense determination is required. It becomes necessary. In this case, since the diameter of the antenna is more than one wavelength,
For example, even if a sense antenna is provided at the center of the aperture and used, the sense becomes uncertain and cannot be used. Therefore, if the sum output for sensing is extracted at the same time as the azimuth component from the two rotating antennas, the azimuth component and the sense component at the rotational position of the antennas can be obtained, and the sense uncertainty can be resolved.

Since the sum output of two antennas is nothing but the vector sum of their respective antenna outputs, the sum output always has a phase difference of 900 degrees from the difference output as shown in Figure 4, so the phase of this sum output is The figure shows the phase sum characteristic cos (T-cosθ) of two anti-πS with i5[:l:S/λ as a parameter, and S/λ is compared with Fig. 3. This is an indication. As shown in the figure, when KS is small compared to λ, the sum characteristic is almost circular, or
As S approaches 05λ, it becomes elliptical, and S = 0
．． When the angle is 5λ, a figure-8 characteristic occurs in which the output is zero in the 0 degree and 180 degree directions. When S becomes 0.5λ or more, S becomes exactly 0.
Since there is a direction of 5λ, the output becomes zero at this point. Since this direction occurs in each quadrant, it becomes a four-lobed output characteristic in which the output becomes zero in a specific direction determined by S/λ (S =
(See characteristics of 0.75λ and 1λ). However, as mentioned above, the phase of the sum characteristic does not change, just like the phase of a single vertical antenna, regardless of these characteristics and regardless of the direction of arrival, so this can be used to make sense decisions. .

Figure 6 shows this sense synthesis characteristic, using the characteristics of Figures 3 and 5 as they are, ignoring the 90 degree phase conversion loss of the sum output, and 1:1 (achieved). If S is 0.5λ or more, a complex sense waveform will result, but a satisfactory sense waveform can be obtained even when S = 0.75λ, which is close to the limit of the antenna spacing according to the present invention. I understand that.

The above is the principle of the antenna device for direction measurement according to the present invention, but in reality, instead of rotating a pair of antennas, the antennas are arranged on the circumference, and the antenna switcher 401 provided at the center is used to connect the antennas to one pair. The antennas are sequentially switched in a circular manner to obtain the difference and sum outputs.

Figure 7 shows an example in which n antennas are arranged at equal intervals on the circumference (hereinafter referred to as equal interval arrangement), and the antenna element spacing S
is determined by the highest measurement frequency, and the aperture of the antenna is determined by the number of antenna elements n. Now, suppose S is 0
．． 72 and the highest measured frequency is 30cm, then n-1
With two lines, D is approximately 27m, and with n=18 lines, D is approximately 40λ. Dipole antennas are used in the VHF and UHF bands, but at 500MHz, D is approximately 1 with n-12 antennas.
．． 5 m, with n=18 lines, D is approximately 2.4 m. On the other hand, in the case of Doppler square search, S is within 0.5λ at most 04λ
It can be seen that the diameter of the antenna can be larger than that of a Doppler antenna when the number of elements is the same. The antennas are switched by a switching element provided in the antenna switching device 401, and antennas 1, 2, 2, and 3 are switched by a switching pulse.
, 3 and 4, etc., two antennas are switched at the same time, and one output converter outputs the υ difference and the sum. Figure 8 shows an example of the signal waveform of the difference output obtained by this switching, and after amplifying this output,
If detected and shaped by a filter, a waveform like the dotted line in the figure can be obtained. The sum output also becomes a step-like wave as shown in FIG. 9, but it is similarly shaped by a filter. Since these waveforms are similar to the output waveforms in the goniometer rotation method, the direction of arrival can be displayed as a propeller image or sense image by modulating the CRT circular sweep signal synchronized with the switching cycle, and the direction can be measured. Digital display of the exact direction of arrival can also be carried out by known means.

As described above, according to the present invention, it is possible to obtain one signal without using complicated techniques such as canceling the frequency modulation component of the measurement radio wave or detecting the azimuth component using two receivers as in Doppler direction finding.
The device can be configured using several receivers. In addition, there is no need to increase the switching frequency of the antenna as in Doppler square search (for example, in the case of a method that extracts frequency deviation due to the Doppler effect), and 500-1000 rotations/rotation degree is sufficient as in the conventional case. , there are few restrictions due to measurement bandwidth and azimuth changes within the band, and measurement is easy.

Since many antenna elements are arranged at equal intervals,
In some cases, such as in the case of broadband, re-radiation from the antenna may affect orientation measurements during use. This is the same in the case of Doppler direction finding, but for this reason, it is necessary to reduce the influence of unused antennas by ungrounding or opening the base of the antenna depending on the measurement frequency, and by inserting impedance. .

On the other hand, the method of symmetrically arranging m sets of two antennas (hereinafter referred to as the symmetrical arrangement method) arranges the antennas in pairs symmetrically around the circumference, as shown in Figure 10. ,
The number of antennas in a set may be at least four, but it is usually eight or an integral multiple of eight.

In the case of this symmetrical arrangement, the spacing S between the antennas in the set is the same as in the case of equally spaced arrangement, but the diameter of the antennas can be arbitrarily selected. For example, when there are 8 sets of antennas,
Even if the highest measurement frequency is 30MH2, the antenna diameter is 100.
? Even when n, K is still 500 MI (z), the antenna diameter can be set to about 20 m. Therefore, the characteristics of a large diameter antenna can be further demonstrated, and the influence of other antennas not in use can be reduced.

FIG. 10 shows a case where eight sets of antennas are used, and two sets of antennas, such as antennas 1 and 2, 3 and 4, and 5 and 6, are switched in sequence at the same time. Although the obtained hourglass shape has a step-like shape as in FIG. 9, it can be processed and measured in the same manner as in the case of equally spaced antennas, including the sense output.

The sensitivity of direction measurement using the antenna device according to the present invention is
Basically, it is almost the same as the Atcock antenna with the spacing S, but compared to the Atcock antenna using a goniometer, there is no goniometer loss (usually accompanied by a loss of about 6 to 10 dB), and the antenna switching circuit is Loss (usually 1-2
dB), it is possible to perform direction measurements not only with high accuracy but also with high sensitivity.

The present invention improves the improvement rate of errors caused by the influence of disturbing objects by symmetrically arranging antennas with directional characteristics on a wide aperture surface, and when the directional characteristics have symmetry, the vertical component at the antenna position is extracted. Although the antenna device is characterized by having unidirectional directivity, the present invention is not limited to the above-mentioned two embodiments, and various modifications can be made without departing from the gist of the present invention. can be carried out. For example, in FIG. 7, in the low measurement frequency band, antenna elements 1 and 3, 3 and 5, 5 and 7
...or 1 and 3, 2 and 4, 3 and 5, etc. Switch two antennas with skipped spacing as a set, double the antenna spacing to improve sensitivity, and use antennas 1 and 3. It is also possible to return to the combination of antennas 1 and 2 at frequencies where the spacing is approximately 0.7λ.

[Brief explanation of the drawing]

The drawings show examples, FIG. 1 is an explanatory diagram showing the principle of the invention, and FIG. 2 shows the phase difference output N obtained by this principle.
1 Figure 3 shows the characteristics of the phase difference output of the two antennas, that is, the directivity of the Atcock antenna. Figure 4 is a vector diagram showing the phase difference and sum of the two antennas. Figure 5 shows the phase difference output characteristics of the two antennas. The phase sum characteristic diagram of the same two antennas, Figure 6 is similar to Figures 3 and 5.
The composition (sense) characteristics of the difference between the figures and the sum output are shown by each S/λ, and Fig. 7 is a schematic diagram of the configuration of the equally spaced arrangement method, which is one of the embodiments of the present invention. Evenly spaced arrangement of figures −
FIG. 9 is a diagram showing the difference output obtained by switching the antenna, and FIG. 9 is a diagram showing the sum output of the same antenna. Figure 10 is a schematic diagram of the symmetrical arrangement of another embodiment. 1-16. n...Antenna, 301...Transformer, 401
・・Antenna switcher, 50 antenna elements, 601・・
antenna connection cable. Purification of the patent applicant's drawing (no change in content) Cow 1 time/172 Mouth rotation angle e Tree 3 Figure O 7 Mouth 180° Season 8k O9 Figure S = 0.25 entered Figure 10 800 Procedural amendment (voluntary ) Director General of the Japan Patent Office, July 25, 1982 1. Indication of the case η Temple Gansho 58-/88S3B 2. Name of the invention Antenna device for measuring direction□ 3. Relationship with the person making the amendment Patent applicant: 141 2-10-45 Kamiosaki, Honbunagawa-ku, Tokyo Specification/Drawings 56 Contents of amendments Reprint of the specification/drawings (no change in content) 6, List of attached documents (1) Specification for amendment 1 copy (2) 1 drawing for correction Procedure Correction 1 (voluntary) Showa 5? Director General of the Japan Patent Office, January 29, 2013 1. Indication of the case Patent application 1973-/g/353B 2. Name of the invention Antenna device for direction measurement 3. Relationship with the amended person case Patent applicant address: 141 Tokyo Parts 2-10-45 Kami-Osaki 2-10-45 details 1 5 Contents of the amendment As shown in the attached sheet 6 List of attached documents (1) Amendment to the content of the amendment Contents

Claims (1)

[Scope of Claims] ■ A group of antennas in which a plurality of antennas are arranged at equal intervals on the circumference, and two adjacent antennas or two antennas with skipped intervals are sequentially switched in a circular manner as a set. Connected to the primary side of one transformer, the output of the phase difference voltage between the two antennas is taken out from the secondary side of this transformer, and the direction is measured, and the sum output is calculated from the midpoint of the transformer. An antenna device for azimuth measurement, characterized in that a sense determination is made based on an output extracted from the azimuth. 2. The antenna device for measuring direction according to claim 1, which measures direction over a wide range of frequencies, in which the two adjacent antennas are set as a set in a certain frequency band, and in other frequencies. In the belt, 2 with skipped intervals
An antenna device for azimuth measurement, characterized in that the switching is performed using a set of book antennas. 3 A plurality of sets of two antennas arranged at intervals are arranged symmetrically on the circumference, and each set is connected to the primary side of the transformer while being sequentially switched in a circular manner. Direction measurement is performed using an output obtained by extracting a phase difference voltage between the two antennas from the next side, and sense determination is performed using an output obtained by extracting a sum output from the midpoint of the transformer. antenna device.