JP2770064B2 - Two-signal interference separation direction measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for measuring the direction of a radio wave by a phase interference method,
In particular, the present invention relates to a method of measuring the direction of each wave separately when two waves having similar frequencies are interfering.

[Conventional technology]

The azimuth measurement of the phase interference method usually uses one antenna A
, The two antennas B and C are connected to antenna A, respectively.
The arrangement is made such that the span lines between B and the antennas A and C are perpendicular to each other, and the arrival direction of the radio wave is obtained from the phase difference between the antennas A and B and the phase difference between the antennas A and C.

[Problems to be solved by the invention]

Generally, the phase interference method has a large span in order to increase the phase difference between antennas. The above-mentioned antenna orthogonal arrangement has many problems in the antenna holding mechanism when the span is large because other antenna arrangements are not symmetrical with respect to the antenna serving as the axis.

On the antenna holding mechanism, when three antennas are arranged in a regular triangle, all the antennas are symmetric with respect to the center, which is the best. Determining the azimuth by such antenna arrangement requires a complicated calculation formula for determining the phase difference between two adjacent antennas, but can be obtained in the same manner as a conventional orthogonally arranged antenna. All of the above are phase measurements of a single wave. However, when two waves interfere with each other, the method of separating and measuring the directions of the two waves from the composite wave is as follows.
unknown.

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel method for measuring an antenna group having a regular triangular arrangement, which is advantageous in terms of antenna construction, by separating the directions of two interference waves.

[Means for solving the problem]

It is assumed that the frequencies of the two waves are close to each other as a premise of solving the above problem. This premise is that radio interference is a problem when frequencies are close to each other, and that the IF frequency band of the receiver is narrowed. However, in this method, as will be described later, there is a slight difference between the frequencies of the two waves, and the fact that there is a periodic variation in the parameter to be measured due to this frequency difference is used to help determine the direction.

The azimuth measuring method of the present invention includes a method of obtaining all of the phase differences between adjacent antennas of a regular triangular antenna group and obtaining a maximum phase difference from a periodic variation of each phase difference. Ratio relationship between azimuth angles φ ₁ and φ ₂ to be measured and amplitudes E ₁ and E ₂ (E ₁ −E ₂ ) of the two waves with respect to the maximum phase difference
Solving a system of equations with // (E ₁ + E ₂ ) as the unknown variable,
_1, is made of a method of obtaining the phi _2.

In the above case, all of the phase differences between the adjacent antennas are obtained, and the calculation required for determining the azimuth also targets these three phase differences. As another method, a method in which the phase difference between adjacent antennas is obtained in two ways to reduce the calculation load in measurement will be described below.

In this alternative method, a phase difference between adjacent antennas of an antenna group arranged in a regular triangular arrangement is obtained only for two adjacent antennas, and a maximum phase difference is obtained from a temporal variation of the angular phase difference. (E ₁ −E ₂ )
For the method of calculating − (E ₁ + E ₂ ) (= P) and the two maximum phase differences obtained by the above method, P is a known constant, and the azimuths φ ₁ and φ ₂ to be measured for two waves are unknown variables. And solving two simultaneous equations to obtain φ ₁ and φ ₂ .

[Action]

The principle of the procedure of the present invention will be described. The derivation of the formula is all done in the examples, and if necessary for explanation,
Specify the formula of the embodiment.

Generally speaking, the measurable physical quantity is the antenna A
Phase difference Da between B, phase difference Db between antennas A and C, and phase difference Dc between antennas B and C. On the other hand, the unknowns are azimuth, frequency, amplitude, and phase at point 0 which is the center of the antenna group for each of the two waves, that is, eight. Of these, the phase at point 0 is subtracted because the phase at point 0 is, for example, the phase difference of the same wave with respect to antenna AB when considering one wave in Da. Since each wave has the above-described relationship, Da can be calculated assuming that there is no phase difference between the 0 points of the two waves.

Next, in calculating Da, Db, and Dc, the frequencies of two waves ω ₁ and ω ₂
Are close to each other, so that the phase of the composite wave of each antenna, for example, θ which is fixed and does not fluctuate with time in the equations (5) and (6) is calculated assuming that R is constant. Where Δω ₀
Is periodically omitted as a temporal variation term Δω ₀ t, and is not omitted. The amplitudes E ₁ and E ₂ are P = (E ₁ −E ₂ ) / (E ₁ +
It can be seen that E ₂ ) comes in as one unknown. By the above calculations, the unknowns are two directions, two frequencies (ω ₁ , ω ₂ ), and one amplitude relation number P. Where ω ₁ ,
As interference frequency for omega ₂ is within an error range as the same frequency, in the following a known frequency.

Next, Da, Db, and Dc vary periodically because of Δω ₀ t. When Damax, Dbmax, and Dcmax are obtained from these fluctuation values, the relationship represented by Expression (13) is obtained in which the unknowns enter the imprint. In this equation, for example, Sa max is P, φ ₁ , φ as shown in equation (12).
₂ , (φ ₁ + d) are included as unknowns. After all Da max, D
For the three determined values of b max and Dc max, two directions φ ₁ ,
The variables of φ ₂ and one amplitude relation number P correspond to each other, and can be solved as a ternary simultaneous equation.

The above is the first method, and the second method is 1
When two synthesized waves are observed, amplitude modulation is performed by E ₁ and E _2, so that P is determined and set to a known number, whereby, for example, φ ₁ and φ ₂ are obtained from the two determined amounts of Da max and Db max.
Can be requested.

〔Example〕

The present invention is directed to a case where two interference waves are close in frequency but slightly different from each other, but a case where the two waves have the same frequency, amplitude and phase will be described. FIG. 1 shows a regular triangular antenna and the arrival directions of two waves.

In FIG. ₁ , if it is assumed that radio waves f ₁ and f _{2 of} sin ωt having the same frequency and amplitude and having the same phase at the point 0 arrive at the same time, f ₁ and f ₂ induced by the antenna A Ea (f ₁ ) = sin (ωt + Rcosφ ₁ ) Ea (f ₂ ) = sin {ωt + Rcos (φ ₁ + d)} here Where Le is the side length of the triangle and λ is the wavelength.

Here, Le = λ / 2.

Voltage of the antenna A is, Ea (f ₁₎ and Ea (f ₂₎ from a synthetic Ea = sin (ωt + Rcos φ 1) + sin {ωt + Rcos (φ 1 + d)} = K A sin (ωt + L) where, K _A = represented as 2cos {Rsin d / 2 · sin (φ 1 + d / 2)} L = Rcos d / 2 · cos (φ 1 + d / 2).

Then the voltage of the composite wave at the antenna B is, Eb = sin {ωt-Rcos (π / 3-φ 1)} + sin {ωt-Rcos (π / 3-φ 1 -d)} = K B sin (ωt + M) Here, K _B = 2 cos ｛Rsin d / 2 · sin (π / 3−φ ₁ −d / 2)｝ M = −Rcos d / 2 · cos (π / 3−φ ₁ −d / 2) voltage of the composite wave of C is Ec = sin {ωt-Rcos ( π / 3 + φ 1)} + sin {ωt-Rcos (π / 3 + φ 1 + d)} = K C sin (ωt + N), Kc = 2cos {Rsin d / 2 · sin (π / 3 + φ ₁ + d / 2)｝ N = −Rcos d / 2 · cos (π / 3 + φ ₁ + d / 2)

Therefore, assuming that the phase difference between the synthesized waves between the antennas A and B and between the antennas A and C is Da and Db, Da = LM = π · cos d / 2 · cos (φ ₁ + d / 2−π / 6) Db = L−N = π · cos d / 2 · cos (φ ₁ + d / 2 + π / 6) Since the phase differences Da and Db can be obtained, solving this equation gives φ as the direction of the two waves.
₁ and φ ₁ + d can be obtained.

Now, two waves f _1, f ₂ subjects in the present invention varies the amplitude E _1, E _2. The frequencies ω ₁ and ω ₂ are different, but the difference is small.

Synthesis voltage at one _{antenna, E = E 1 sin (ω} 1 t + θ 1) + E 2 sin (ω 2 t + θ 2) = K A sin (ω 0 t + L) and comprising (1).

Where ω ₀ = 1/2 · (ω ₁ + ω ₂ ) (2) L = (θ ₁ + θ ₂ ) / 2 + tan ⁻¹ {Ptan [Δω ₀ t + (θ ₁ −θ ₂ ) /]}
(3) where P is an unknown and is given as a ratio function (E ₁ −E ₂ ) / (E ₁ + E ₂ ) of the amplitudes E ₁ and E ₂ of the _two radio waves. Δω ₀ = 1/2 · (ω ₁ −ω ₂ ) (4)

From the equation (3), the phase L of the composite wave of the antenna A is L = (θ _1A + θ _2A ) / 2 + tan ⁻¹ {Ptan [Δω ₀ t + (θ _1A −θ _2A / 2)}} (5) Similarly, The phase M of the composite wave is M = (θ _1B + θ _2B ) / 2 + tan ⁻¹ {Ptan [Δω ₀ t + (θ _1B −θ _2B ) / 2]}
(6) where θ _1A = Rcos φ ₁ θ _2A = Rcos (φ ₁ + d) θ _1B = −Rcos (π / 3−φ ₁ ) θ _2B = −Rcos (π / 3−φ ₁ −d) θ _1C = −Rcos (π / 3 + φ ₁ ) θ _2C = −Rcos (π / 3 + φ ₁ + d)

R at θ _1A and θ _2A is Ω ₁ ≒ ω
_Since this frequency is treated as known, R is considered to be constant. Further, the two waves f ₁ and f ₂ are calculated on the assumption that the phases are the same at the center 0 point of the regular triangle. For this,
This is explained on page 15 later. Equations (5) and (6) show Δω
_{Contains 0} .

Δω ₀ should be set to 0 if ω ₁ ≒ ω _2. However, even if this term is small, it can be ignored as Δω ₀ t because it gives a periodic fluctuation. On the other hand, θ _1A and θ _2A are time-independent constants from the approximation of ω ₁ ≒ ω ₂ described above.

Next, assuming that the phase difference between the antennas AB is Da, tan Da = tan (LM) = (tanL-tanM) / (1 + tanL · tanM) (7) If this is arranged, Da = 1/2 · (Θ _1A + θ _2A −θ _1B −θ _2B ) + Sa (8) Sa is a correction term because the amplitude cannot be ignored.
Sa is given by the following equation.

Sa = tan ^-1 ｛2Psin θ _L / [(1-P ² ) cas θ _M + (1 + P ² ) cos θ _L ]｝ (9) where θ _L = 2R cos π / 6 · sin d / 2 · sin ( φ ₁ + d / 2−π / 6) (10) θ _M = 2Δω ₀ t + 2Rsin π / 6 · sin d / 2 · cos (φ ₁ + d / 2−π / 6) (11) Sa is the equation (11) periodically varying because they contain [Delta] [omega ₀ t within the theta _M indicated by, but as can be seen from equation (9) theta _{M =} [pi
It becomes the maximum when.

Sa max = tan ^-1 {2Psin θ _L / [(P ² -1) + (P ² +1) cos θ _L )} (12) Phase difference Db between antennas A and C, phase difference between antennas B and C Dc also has a similar form of equation (8). However
Θ _{L in} Sb and Sc is Sb: 2Rcos π / 6 · sin d / 2 · sin (φ ₁ + d / 2−π / 6) Sc: 2Rsin π / 3 · sin d / 2 · sin ( φ ₁ + d / 2).

Therefore, Da max of the phase difference Da between the antennas A and B
And Db max between antennas A and C, and antennas B and C
Dc max in between can be expressed as:

Da max = 1/2 (θ _1A + θ _2A- θ _1B- θ _2B ) + Sa max Db max = 1/2 (θ _1A + θ _2A- θ _1C- θ _2C ) + Sb max Dc max = 1/2 (θ _1B + θ _2B− θ _1C −θ _2C ) + Sc max (13) Looking at Da max in equation (13), each term of θ is related to the direction of two waves, is a function of φ ₁ , d, and Sa max is P, φ ₁ , d is a function of d. From this, Da max, Db max, Dc max are eventually P, φ
_{This is a} ternary system of ₁ and d variables, and the solution should be found. So determined Da max, Db max, the Dc max from the data, put the appropriate value (initial value) P, was calculated by iterative method, phi _1, obtains a d, arrival direction phi ₁ of two waves and phi ₂ = Φ
₁ + d can be obtained. Note that θ _1A , θ _2A, etc. in the equations (5) and (6) are obtained assuming that two waves have the same phase at the zero point of the origin of a regular triangle. The actual two waves do not have the same phase, but as shown in equation (13), θ _1A and θ _1B
Is always (θ _1A −θ _1B ), and θ _2A and θ _2B are (θ _2A −θ _2B ), as the phase at the above-mentioned zero point is canceled out in the calculation.
The phase difference at the zero point of the wave does not affect the azimuth measurement. Therefore,
The calculation may be performed assuming that the phases of the two waves at the zero point from the beginning are the same.

Next, as a second method to the first method, a method in which only two phase differences between adjacent antennas need to be considered will be described. Looking at the time course of the combined voltage of one antenna, an amplitude-modulated wave is observed, and P = (E ₁ −E ₂ ) / (E ₁ + E ₂ ) is obtained from the ratio between the maximum value and the minimum value. be able to. Therefore, if this value is a known constant, (1
Equation 3) is reduced to a system of binary equations. Therefore, for example, from only the two equations of Da max and Db max, φ ₁ , φ ₂ , (φ ₁ +
d) can be obtained by calculation.

A measurement system for implementing the method of the present invention can be configured, for example, as shown in FIG. With this configuration, it is most important that the receivers 3A, 3B, and 3C that determine the phases of the antenna group 1 arranged in a regular triangular arrangement have the same phase. Therefore, one receiver is used as a master and the other two receivers are used as slaves. In addition to adjusting the phase of the local oscillation frequency of each receiver, the converted IF (intermediate frequency) of the master receiver 3A is taken out, and phase calibration is performed. The required signal generator 4 performs inverse conversion using the local oscillation output to generate a received signal, and supplies the received signal to three receivers for calibration. Further, a phase shift from the antenna group 1 to the receivers 3A, 3B, 3C is corrected by the cable phase matching device 2. IF output of receiver 3A ~ 3C
The digital signal is converted by the A / D converter 5 and stored in the computer 6 as data, and all operations are performed. The obtained azimuth angles φ ₁ and φ ₂ are displayed by the CRT 7, and each data can be displayed if necessary.

〔The invention's effect〕

As described above, according to the method of the present invention, when measuring the direction of a radio wave by using a group of antennas arranged in a regular triangle, two interference waves are separated to give respective directions.
The two waves, for which interference is a problem, are very difficult to separate because the frequencies are very close. However, in this method, utilizing the fact that the phase difference between adjacent antennas periodically fluctuates due to the small frequency difference between the two waves, the maximum value is obtained from the data, and the maximum value is set as a function value. The equation is the azimuth angle of each wave and the amplitude relationship ratio of each wave (E ₁ −
By using the fact that a ternary simultaneous equation is established using E ₂ ) / (E ₁ + E ₂ ) as variables, it is possible to obtain the direction of two waves. Further, if (E ₁ −E ₂ ) / (E ₁ + E ₂ ) is experimentally obtained, the reduced relation of the binary simultaneous equations can be used.

[Brief description of the drawings]

FIG. 1 shows the relationship between the antenna group and the azimuth of two interference waves according to the present invention, and FIG. 2 is a block diagram showing an example of a measurement system when the present invention is implemented. DESCRIPTION OF SYMBOLS 1 ... Antenna group, 2 ... Cable phase matching device, 3 ... 3A-3C ... Receiver, 4 ... Signal generator for phase calibration, 5 ... IF A / D converter, 6 ... Computer 7 ... CRT.

Claims (2)

(57) [Claims] 1. A method for separating and measuring the incident azimuths of two waves having frequencies close to each other at the same time when two waves having frequencies close to the antenna group arranged in a regular triangle are arranged. And a method for obtaining each maximum phase difference from the periodic variation of each phase difference, and an azimuth φ to be measured for two waves with respect to the phase difference between three adjacent antennas obtained by the above method. _1, phi ₂ and amplitude E _1, E ₂
Solving the ternary simultaneous equations with the relationship (E ₁ −E ₂ ) / (E ₁ + E ₂ ) as unknowns to obtain φ ₁ , φ ₂ , Signal interference separation direction measurement method. 2. A method for separating and measuring the incident azimuths of two waves having frequencies close to each other at the same time when two waves having frequencies close to each other are incident on a regular triangular antenna group. Is obtained only for two adjacent antennas, and the maximum phase difference is obtained from the periodic variation of each phase difference, and (E ₁ -E ₂ ) /
A method for obtaining (E ₁ + E ₂ ) = P, and for the two maximum phase differences obtained by the above method, P is a known constant, and azimuths φ ₁ and φ ₂ to be measured for two waves are unknown variables. A method for determining φ ₁ and φ ₂ by solving a system of simultaneous equations, and a phase interference type two-signal interference separation azimuth measuring method, comprising: