JPS58146870A - Direction detecting device - Google Patents

Abstract

PURPOSE:To detect in which direction a receiving point exists from a transmitting point, by receiving linear FM signals having each different center frequency, which are radiated from 2 transmitting points, and detecting the difference frequency. CONSTITUTION:In case when a receiver 1 is on faces 7, 8 for vertically dividing a line for connecting an antenna 5 and 6, into 2 equal parts, a difference frequency signal 18 being an output of a mixer 13 becomes DF2, and when the receiver 1 is in the upper part than the faces 7, 8, the signal 18 becomes DF1 and is larger than DF2, and on the contrary, when it is in the lower part, the signal 18 becomes smaller than DF2. Accordingly, the signal 18 has information in the direction seen from the antennas 5, 6, as frequency information.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a direction detection device that utilizes a propagation path difference from two reference points that radiate waves such as radio waves.

Conventionally, a hyperbolic navigation device is well known as this type of direction detection device. A hyperbolic navigation device calculates the position on a plane as a locus of points whose distances from two fixed points are constant, i.e., the intersection of a hyperbola with two fixed points as its focal point and another set of hyperbolas created in the same way. This is what we seek. Hyperbolic navigation devices are originally used to indicate their position to ships and aircraft, and their positioning performance is tailored to suit their intended use. Therefore, since the distance difference is also measured by direct time measurement or phase difference measurement,
It is not easy to obtain measurement accuracy of several scales using these methods. In addition, the present invention, which requires such accuracy due to the purpose of use, converts the direction of existence seen from the two transmitting points of the receiving point into a frequency, thereby reducing drift in the amplification degree and delay time of the receiver, etc. It is an object of the present invention to provide a direction detection device that eliminates drawbacks that affect detection accuracy and that allows processing to be performed with high accuracy in the frequency domain using analog filters, digital filters, and the like.

That is, the present invention provides a direction detection device in which two transmitting points that emit linear FM signals with different center frequencies are used as reference points, in which the two emitted linear FM signals are received by a receiving antenna; Direction information is obtained as frequency information by converting a signal into intermediate frequency signals having two predetermined center frequencies and determining the difference frequency between the two signals.

Next, embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, transmission signals 3, 4 generated by a transmitter 2
is radiated from antenna 5.6. Transmission signals radiated from antennas 5 and 6 are received by a receiving device located at point 1. FIG. 2 shows the receiving device. Antenna 1 in Figure 2
The received signal received at 9 is divided into two by a branch circuit 9 and input to a receiver 10.11. Receiver 10.11 receives signal 14
．． 15 as a local oscillator input, intermediate frequency signals 16 and 17 are generated. The intermediate frequency signals 16, 17 are input to the mixer 13, and the difference frequency signal 18 is taken out.

FIG. 3 shows a transmission signal 4 (FIG. 1) with a center frequency Fm and a transmission signal 3 (FIG. 1) with a center frequency F.

The signal received by the antenna 19 (Fig. 2) has radio wave propagation times t and t2 compared to Fl and F2 in Fig. 3.
This is shown in FIG. 4. Furthermore, the intermediate frequency signal 16.17 in FIG. 2 is combined as IFl, IF in FIG. It is shown in Figure 6.

In FIG. 1, if the receiver 1 is on the plane 7.8 that vertically bisects the line connecting the antennas 5 and 6, then the mixer 13
The difference frequency signal 18 (Fig. 2) of the output of (Fig. 2) is DF
, (Fig. 6), and as shown in Fig. 1, the receiver 1
is above plane 7.8, the difference frequency signal 18 becomes DFX (FIG. 6), which is greater than DF2. When the receiver l is below the plane 7.8, the difference frequency signal 1B is DF.

The difference frequency signal 18 is therefore smaller than the receiver 1
It can be seen that the information on the direction seen from the antennas 5 and 6 of is included as frequency information.

Note that, as shown in FIG. 1, the bandwidth of the linear FM signals radiated from the antennas 5 and 6 is fm.

In Fig. 1, the distance between the receiver 1 and the antennas 5 and 6 is e1# el * the distance between the receiver 1 and the point 7 is r, the line segments 1 and 7 are the plane 7, Angle θ with 8, line segment 7,5
If the length of 7 and 6 is a, and the speed of light is C, then the frequency DF1 of the difference frequency signal 18 is as follows.

When a is sufficiently large compared to r, 4 鵞 - stone = 2 as Todoro n θ
(3), and furthermore, in equation (3), θ is the sufficient ratio J! , (When!, - stone = 2aθ.As can be seen from equations (1) to (4), the present invention is also effective when measuring angles.

As explained above, this invention is a direction detection device using linear FM signals, which receives linear FM signals having different center frequencies emitted from two transmission points, and detects the difference frequency between the received signals. This has the effect of being able to detect the direction in which the receiving point is from the transmitting point.

[Brief explanation of the drawing]

1 and 2 are block diagrams of one embodiment of the present invention,
3 to 6 are diagrams for explaining the present invention in detail. 1... Receiving device, 2... Linear FM signal transmitter, 3.4... Transmission linear FM reconnaissance, 5.
6... Antenna, 7... Antenna 5,
A bisecting point of the line connecting 6, 8... A straight line on a plane that includes point 7 and is perpendicular to line segments 5 and 6, 9... Branch circuit, 10.11. ...Receiver, 12...
・Local oscillator, 13...Mixer, 14, 15・
...Local oscillation signal, 16.17...Intermediate frequency signal, 18...Difference frequency signal, 19...
receiving antenna.

Claims (1)

[Claims] In a direction detection device using two transmission points that emit linear FM signals with different center frequencies as reference points, the device includes means for receiving the two linear FM signals, and means for receiving each of the received linear FM signals (No. 1. A direction detection device comprising: means for converting a frequency into an intermediate frequency signal; and means for taking a frequency difference between the intermediate frequency signals.