JPS6130443B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in an antenna device capable of removing interfering radio waves by changing the null direction of the directivity. In recent years, antenna devices that can remove interference waves such as TV ghosts have been developed to have zero or very low reception sensitivity to radio waves from one specific direction, that is, to have a directional null, and to remove this null. Antenna devices have been proposed that can arbitrarily change the direction in accordance with the arrival direction of interfering radio waves.
An example of the directivity pattern of such an antenna device is shown in FIG. In the figure, the depressed part of the pattern is called a directional null, and the antenna's directional pattern is designed so that the direction in which this null is formed (θ = 20° direction in the figure) matches the arrival direction of the jamming wave. Interfering radio waves can be removed by changing the As such a conventional antenna device, there is one shown in FIG. The configuration of this antenna device is such that the same antennas A1 and A2 having the same electrical characteristics are arranged on the left and right sides with a distance S apart, and both signals are combined by an anti-phase synthesizer 3 via feed lines l ₁ and l ₂ respectively. It is. For the receiving antenna, a combined output is obtained from the terminal 4, and for the transmitting antenna, power is supplied to the terminal 4. In the antenna device having such a configuration, the condition for forming a directional null angle in the θ direction is given by l ₂ −l ₁ =S·sin θ (1). l ₁ and l ₂ are the electrical lengths of the feed lines in FIG. 1, and S is the antenna spacing. In addition, the antenna device of the type shown in Fig. 1 is given the condition of formula (1),
A feature is that the directional null angle formed in the θ direction is maintained over a wide band. In order to realize an antenna based on this principle as an industrially useful antenna, we conducted various studies and found that there were various problems. The above-mentioned anti-phase synthesizer 3 is actually difficult to manufacture, and an in-phase synthesizer is easier to manufacture. Therefore, a practical means is to combine an in-phase synthesizer and a phase inversion circuit to provide the function of an anti-phase synthesizer. However, at that time antennas A1 and A2
It was found that the following problems occur when using a phase difference feeding antenna. The antenna shown in FIG. 2 is an antenna called a phase difference feeding antenna, and its configuration is such that feed lines with electrical lengths F ₁ and F ₂ are connected via balun 6 and balun 7, and F ₂ −F ₁ = d... . . . (2), one of them is phase-inverted in the circuit 5 and synthesized by the in-phase synthesizer 10. d is the distance between elements 8 and 9. The directivity of this phase difference feeding antenna is unidirectional in the forward direction.
When such antennas having exactly the same characteristics are used as A1 and A2 in FIG. 1, the configuration shown in FIG. 3 is obtained. That is, if the in-phase synthesizer 11 and the phase inverter circuit 12 constitute the anti-phase synthesizer 3, and the feed lines l ₁ and l ₂ are adjusted according to the relationship shown in equation (1), it is possible to obtain a wide band in any θ direction. Thus, an antenna device that can form a directional null can be obtained. However, it is necessary to use coaxial lines for the feed lines l ₁ and l ₂ in order to avoid overlapping external radio waves, and for this purpose, both the combiner 11 and the phase inversion circuit 12 are of an unbalanced type that can be connected to the coaxial line. There is a need. Figure 4 shows a specific example of this that we considered during the research process. However, in FIG. 3, the amplitudes of the received output signals are equal at the feeding points 21 and 22 of each antenna A1 and A2, but the phase inversion circuit 12, specifically the one in FIG. When passing through such a circuit, the amplitudes of the left and right received output signals become unbalanced due to insertion loss, and both terminals 23 and 2 of the in-phase synthesizer 11
4 is input. This causes deterioration of characteristics such that the depth of the directional null becomes shallow. To remedy this, we considered inserting an attenuator with a loss equal to the loss caused by circuit 12 on the opposite side of circuit 12 to balance both amplitudes, but in that case, the circuit configuration would be complicated, and A reduction in operating gain occurs due to losses. Furthermore, the increase in the number of parts also leads to a decrease in the reliability of the antenna device. The loss of the phase inversion circuit 12 generally has frequency characteristics,
This also has secondary difficulties, such as the need for the attenuator to be compensated to have similar frequency characteristics. The present invention solves the various practical technical problems as described above in the antenna device shown in FIG. The purpose is to provide equipment. The present invention utilizes two types of phase difference feeding antennas, an in-phase type combiner, and a phase shifting feed line, each of which has the same directivity amplitude characteristic and inverts only the phase characteristic of the unidirectional phase difference feeding antenna. By adjusting the length of the phase-shifting feeder line on one side of the combination, the above-mentioned problems found in our investigation were improved, and an industrially useful antenna device was realized. Hereinafter, the present invention will be explained based on examples. First, as shown in FIG. 5, consider a phase difference feeding antenna in which the element spacing is d and the amplitude of the current on each element is equal and equal to _I0 . Now, taking the current phase of the #1 element among the two elements as a reference, the current phase of the #2 element is relatively delayed by 2πl/λ by the phase shift feeder line, and the phase is further delayed by π. Consider the case where Although we used θ ₁ = 180°, the directivity of the first phase-difference feeding antenna with a null angle in the θ ₁ direction is generally determined by the following formula, with element directivity as f(θ) and referring to Figure 5. It can be expressed by Therefore, l is the electrical length of the phase shift feeder line, and l
=d・cosθ Select ₁ . Also, λ is the wavelength,
k is a propagation constant. Equation (3) is simplified and can be expressed as the following equation. Equation (4) represents the directivity of the phase difference feeding antenna.
The antenna having this directivity will be referred to as the first phase difference feeding antenna. Next, as a second phase difference feeding antenna, if we consider a phase difference feeding antenna whose directional amplitude characteristics are equal to Equation (4) and only the phase characteristics are reversed, mathematically, Equation
The directivity can be expressed by adding or subtracting π to the phase term in (4). That is, it may be expressed by the following equation. If we realize two types of phase-difference feeding antennas in which the formula representing this second directivity and the formula representing the first directivity described above apply, and use them, we can achieve phase inversion in unbalanced coaxial transmission. No circuit is required, and synthesis can be performed using an easy-to-manufacture in-phase synthesizer, which improves various characteristic defects such as the unbalance of the received output signal and the deterioration of the null depth mentioned above, and further improves the configuration. It will be understood that reliability can be improved by simplifying the process. FIG. 6 shows a specific configuration of the present invention. Equation (4) shows that the first phase difference feeding antenna A1 having directivity is in phase with the #1 element 30, the #2 element 31, the baluns 32 and 33, the coaxial cables 34 and 35, and the phase inversion connection part 36. It is composed of a synthesizer 37. The first phase difference feeding antenna A1 having the directivity of formula (4) is as shown in FIG.
A phase inversion connection part 3 is connected to the #2 element 31 and the feed point part.
6 is constructed, but the front direction of the directivity is the #1 element 30 side. That is, the first phase difference feeding antenna A1 is arranged such that the element 30 faces a predetermined direction (desired direction of arrival of radio waves). The electrical lengths of coaxial cables 34 and 35 are l ₃₄ and l _35, respectively.
When expressed as follows, l in equation (4) is designed as follows: l=l ₃₅ −l ₃₄ =−d·cosθ ₁ (6). The feeding end of the first phase difference feeding antenna A1 is the common terminal 38 of the in-phase combiner 37, and constitutes an unbalanced coaxial feeding terminal. On the other hand, the second phase difference feeding antenna A ₂ includes the #1' element 40, the #2' element 41, the balun 42, and the balun 42.
3, coaxial cables 44 and 45, a phase inversion connection section 46, and an in-phase type combiner 47. The reason for this configuration is that the directivity that the second phase difference feeding antenna A2 should have is given by equation (5), so this equation (5) is decomposed into two terms and given to each element. This is the result of expanding equation (5) so that the power current can be found. That is, When expanded using the numerical formula of becomes. From formula (8)

Since the coefficient of [formula] is in the front, the current of element 40 of #1' is I ₀ e ^-i 〓,

Because the coefficient of [formula] is backward The current of #2′ element 41 is

[Formula]. Therefore, if the second phase difference feeding antenna A2 is manufactured so that such a current can be realized, the expected antenna device of the present invention can be constructed.
Similarly to the first phase difference feeding antenna A1, the second phase difference feeding antenna A2 is arranged with the element 40 facing the same direction as the element 30, and in a direction perpendicular to this direction (in this embodiment, the horizontal direction ) is arranged at a predetermined stack interval from the first phase difference feeding antenna A1. Since the phase of the current is considered based on #1 element 30, the electrical length of coaxial cables 44 and 45 is
Represented by l ₄₄ and l ₄₅ , it is designed so that l ₄₄ = l ₃₄ and l ₄₅ = l ₃₅ , and the phase inversion connection 4 is connected to the feeding point of the #1' element 40.
6, it is possible to realize a phase difference feeding antenna having the second directivity expressed by equation (5). In this way, the first phase difference feeding antenna A1 and the second phase difference feeding antenna A2 are realized, and the coaxial cables 50 are connected to their coaxial feeding terminals 38 and 48, respectively.
and 51 are connected. Furthermore, a line-type phase shifter 50' is connected in series with the coaxial cable 50, if necessary. The other ends of the coaxial cables 50 (phase shifters 50') and 51 are terminals 53 of the in-phase generator 52,
54 respectively, and the composite output signal is connected to terminal 5.
5. Here, the electrical length of the coaxial cable 51 is expressed as _l51 , and the coaxial cable 5
0 and the line-type phase shifter 50' is expressed as _l50 . By adjusting the line-type phase shifter 50', the electrical length _l50 can be changed. As a result, a directional null can be formed in a wide band in any θ direction as expressed by θ=sin ⁻¹ (l ₅₀ −l ₅₁ /S) (9). As can be seen from the embodiments described above, the antenna device according to the present invention has an extremely simple system configuration, and it goes without saying that it greatly contributes to improved reliability. Moreover, coaxial cable as a component,
The consistent use of in-phase synthesizers is extremely rational for use in environments with strong electromagnetic interference. That is, this antenna device has the function of aligning the null angle of the directivity with the direction in which the interfering waves arrive and eliminating the interfering waves. In addition, conventional antenna devices have had characteristics deterioration such as the depth of the generated null becoming shallow, and circuit complexity to compensate for the deterioration, but the present invention eliminates these drawbacks. As a result of repeated research and development through various types of prototype experiments regarding the specific implementation method of the antenna device of the present invention, an industrially useful antenna device as described above was obtained with a relatively simple configuration. It is very effective as a general antenna for eliminating TV ghosts, which are increasing in number. In the above embodiment, a case was explained in which a two-element phase difference feeding antenna was used, but the phase difference feeding antenna is not limited to two elements, and generally up to N elements can be used. It can be designed so that the amplitude of the directivity radiated into space is equal and the phase is opposite. The effects of the present invention can also be obtained by using such a multi-element first phase difference feeding antenna and second phase difference feeding antenna in place of the two-element phase difference feeding antenna. Also,
In the above embodiment, a case has been described in which the first and second phase difference feeding antennas are stacked horizontally, but the effects of the present invention can also be obtained even if they are stacked vertically. In short, the positional relationship between the first and second phase difference feeding antennas is such that they face the same direction and are spaced apart from each other by a predetermined distance in a direction orthogonal to this direction. Furthermore, the stack interval S is (0.7 to 0.8) for the wavelength λ _u of the upper limit frequency of the used band.
Choosing around λ _u results in an antenna with a small sidelobe level, which is preferable in terms of characteristics.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the principle of an antenna device in which a directional null is formed over a wide band, Fig. 2 is an explanatory diagram of a phase difference feeding antenna, Fig. 3 is a diagram configured according to the principle and which we have considered, and Fig. 4 is a circuit diagram showing a specific example of the synthesizer shown in FIG. It is a figure which shows an example of a sex pattern. A1...first phase difference feeding antenna, A2...second
phase difference feeding antenna, 30, 31, 40, 41
...Antenna element, 32, 33, 42, 43... Balun, 34, 35, 44, 45... Coaxial cable, 3
6, 46... Phase inversion connection section, 37, 47... In-phase type combiner, 50, 51... Coaxial cable (power feed line)
50'...Line type phase shifter, 52...In-phase type combiner.

Claims (1)

[Claims] 1 A first phase difference feeding antenna disposed facing in a predetermined direction; a second phase difference feeding antenna, which is arranged at a stack interval of
First and second feed lines each having one end connected to the feed ends of the first and second phase difference feed antennas, and signals guided through the first and second feed lines to each other. a line type phase shifter connected between the other end of the first feed line and the in-phase type combiner so as to make the electrical length of the first feed line variable; An antenna device comprising: