JP2006029959A - Radar system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radar system capable of obtaining high angle measuring precision over a wide angle range, by simple constitution. <P>SOLUTION: In this radar system having a phase monopulse power supply system, a transmission pulse is split, respective frequencies thereof are differed to be transmitted toward different directions. Reception beams are separated based on a difference in the frequencies of the transmission beams after a Σbeam is formed in a reception period. Angle measuring processing corresponding to a squint measuring angle is executed to obtain a measuring angle value for a target, using respective signals of the separated reception beams. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a radar apparatus that measures a target position. In particular, the present invention relates to a monopulse angle measurement type radar apparatus.

  In this type of radar apparatus, either the phase monopulse angle measurement method (phase comparison monopulse method) or the squint angle measurement method (amplitude comparison monopulse method) is often used (see, for example, Non-Patent Document 1). Although the phase monopulse method is excellent in angle measurement accuracy, it is susceptible to multipath due to the wide angle width of the Δ (difference) beam, and has a weak point in angle measurement accuracy in a low elevation angle region. In contrast, the angle measurement accuracy of the squint angle measurement method is inferior to that of the phase monopulse method, but the angle measurement accuracy is superior to that of the phase monopulse in a multipath environment due to the narrow beam width of the Σ (sum) beam. Can be obtained.

Taking advantage of both of these features, for example, in elevation angle measurement, squint angle measurement is applied at low elevation angles, where multipath effects are significant, and phase monopulse angle measurement is applied at high elevation angles to increase elevation from low elevation angles. It is considered to obtain high angle measurement accuracy up to the elevation angle. However, in order to realize this, circuits such as a power feeding circuit and digital beam forming (DBF) are required for each of the phase monopulse system and the squint angle measuring system, and the scale of the apparatus tends to be large and the cost is also increased. . Therefore, at present, either the phase monopulse method or the squint angle measurement method is often used alone, and there is a dilemma that it is difficult to achieve both the angle measurement range and the accuracy.
Takashi Yoshida “Revised Radar Technology”, IEICE (1996), pp.260-264

As described above, in the existing monopulse radar device, either the phase monopulse method or the squint angle measurement method must be used independently for the angle measurement. There is a problem that it is difficult to obtain angle measurement accuracy.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a radar apparatus capable of obtaining a high angle measurement accuracy over a wide angle range with a simple configuration.

  In order to achieve the above object, according to one aspect of the present invention, a radar unit divides a radar pulse into a plurality of parts, forms transmitting characteristics in different directions from each other, and transmits each in a direction squinted with respect to a target, and forms a receiving beam. Receiving means for receiving a pulse echo from the target based on the radar pulse, separating means for separating the received beam based on the difference in characteristics, and based on mutual received signals of the separated received beam There is provided a radar apparatus comprising angle measuring means for measuring a target position by a squint angle measuring method.

  By taking such means, a squint beam is formed in the transmission beam. Since the characteristics of each squint beam are different, each reception beam can be separated on the reception side. Accordingly, angle measurement processing by squint angle measurement can be performed from the reception signal of each reception beam. In other words, the transmission beam transmits a squint beam that is strong against multipath, and performs phase monopulse angle measurement based on the received beam, so high angle measurement accuracy is achieved over a wide angle range from low elevation angle to high elevation angle. It is possible to get.

  ADVANTAGE OF THE INVENTION According to this invention, the radar apparatus which can obtain high angle measurement precision over a wide angle range can be provided with a simple configuration.

[First Embodiment]
FIG. 1 is a functional block diagram showing a first embodiment of a radar apparatus according to the present invention. This radar apparatus includes a phase monopulse power supply system, and basically performs angle measurement processing based on the phase monopulse system. In FIG. 1, the transmission signal generated by the transmitter 1 and amplified in power is transmitted from the antenna 3 via the circulator 2. At that time, the radar pulse is divided into a plurality of parts and transmitted in directions (squinted directions) in which the respective angles are shifted from each other at different transmission frequencies.

  The echo signal from the target is input to the receiver 4 via the antenna 3 and the circulator 2 and subjected to frequency conversion. Here, the Σ-system received beams are N types of digital signals Σn corresponding to the frequencies of the transmission pulses. One of the Σ signals is used as a reference signal used for phase monopulse angle measurement, and a subscript b is added to this to obtain Σb. The received signals ΔAZ and ΔEL are subjected to frequency conversion of only fb by the receiver 4 to obtain digital signals ΔAZ and ΔEL. These signals are subjected to pulse compression processing by the pulse compression processing unit 51 of the signal processing unit 5 to obtain reception data compressed in the distance direction. The target of the pulse-compressed signal is detected by the target detector 52, and the angle measurement process 53 is performed on the detected target. Control of each unit is performed by the radar control unit 54 in an integrated manner.

  FIG. 2 is a schematic diagram showing an example of a transmission beam in the radar apparatus of FIG. As shown in the figure, in the present embodiment, the transmission pulse is divided into N, and different frequencies fn (n = 1 to N) are assigned to the divided pulses to transmit in different directions. In FIG. 2, a typical method is shown in two directions, and therefore N = 2. On the other hand, the reception beam is formed at a position corresponding to one Σ beam as shown in FIG.

  FIG. 4 is a diagram showing a transmission / reception timing chart in the radar apparatus of FIG. Thus, in this embodiment, radar pulses having different transmission frequencies are transmitted during the transmission period. FIG. 4 shows a state of switching to two frequencies f1 and f2. In the reception period, the reception beams commonly received in the same period are separated into a plurality based on the difference in transmission frequency. Next, processing in the present embodiment will be described using mathematical expressions.

The signal processing unit 5 performs angle measurement processing using a digital signal obtained from the received signal. If the phase monopulse angle measurement method is used, an error voltage ε in each of the AZ plane and the EL plane can be obtained by the following formula (1). If the squint angle measurement method is used, the error voltage ε in each of the AZ plane and the EL plane can be obtained by the following equation (2).

  For example, assuming that n = 3 and b = 1, the error voltage on the AZ plane can be calculated using Σ1 and Σ2 with Σ1 as a reference. Further, the error voltage on the EL surface can be calculated using Σ1 and Σ3 formed in a direction different from Σ2. In order to obtain the angle measurement value θ from the error voltage ε, an angle measurement curve shown in FIG. 5 is prepared from an antenna pattern acquired in advance, and the relationship between the error voltage ε and the angle θ is tabulated. Based on this table, the angle measurement value θ can be calculated from the error voltage ε.

  As described above, in the present embodiment, the transmission pulse is divided in the radar apparatus having the phase monopulse power feeding system, and transmitted in different directions with different frequencies. After the Σ beam is formed in the reception period, the reception beam is separated based on the difference in frequency of the transmission beam. Then, angle measurement processing corresponding to squint angle measurement is performed using each signal of the separated reception beams to obtain a target angle measurement value. Since it did in this way, only a phase monopulse system may be sufficient as a feed circuit, Therefore A structure can be simplified. Further, since the beam can be separated on the receiving side, it is possible to apply the processing corresponding to the squint angle measurement which is hardly affected by the multipath even in the phase monopulse method. Therefore, it is possible to prevent the angle measurement accuracy from being lowered. For these reasons, it is possible to provide a radar apparatus that can obtain high angle measurement accuracy in a wide range of angular widths, such as from a low elevation angle to a high elevation angle, with a relatively small circuit scale and low cost. Accordingly, it is possible to provide a radar apparatus that can obtain a high angle measurement accuracy over a wide angle range with a simple configuration.

[Second Embodiment]
FIG. 6 is a functional block diagram showing a second embodiment of the radar apparatus according to the present invention. In FIG. 6, parts common to FIG. 1 are given the same reference numerals, and only different parts will be described here. In FIG. 2, a transmitter 1 transmits a radar pulse subjected to pulse compression modulation. In the present embodiment, the center frequencies of the transmission pulses divided into a plurality are made the same, and the chirp directions thereof are made different. Here, it is changed in two directions of up-chirp and down-chirp. In addition, the separation unit 51a of the pulse compression processing unit 51 separates the reception beam into a plurality of beams based on the difference in modulation direction.

  FIG. 7 is a diagram showing a transmission / reception timing chart in the radar apparatus of FIG. In the present embodiment, radar pulses having different modulation directions are transmitted during the transmission period. FIG. 7 shows a state of switching to two modulation directions of up-chirp and down-chirp. In the reception period, based on the difference in the chirp direction, the reception beams commonly received in the same period are separated into a plurality.

The pulse compression process can be performed by the following equation (3), for example.

  In the formula (3), the chirping process is not limited to two types of UP and DOWN, and generally N types can be applied. For the Σ system, N types of weights corresponding to N types of transmission modulation chirps are prepared as pulse compression weights, and N types of pulse compression signals Σn (xc is set to Σ) are obtained using these weights. be able to. Using this Σn, the error voltage εs can be calculated by performing the calculation of the equation (2), and the squint angle measurement value can be obtained using the angle measurement curve.

  As described above, in the second embodiment, the transmission pulse is divided in the phase monopulse radar device, and the modulation method (for example, the direction of chirp modulation) of each transmission pulse is changed and transmitted in the squinted direction. After the Σ beam is formed in the reception period, the reception beam is separated based on the difference in the modulation method of the transmission beam. Then, angle measurement values are obtained by performing squint angle measurement using the received signals of the separated beams. As described above, the beam can be separated on the receiving side also by changing the modulation method of the transmission beam. Therefore, processing equivalent to squint angle measurement can be realized, and, similarly to the first embodiment, it is possible to provide a radar apparatus capable of obtaining high angle measurement accuracy over a wide angle range with a simple configuration. Become.

  In addition, this invention is not limited to the said embodiment as it is. For example, although pulse compression has been described as a modulation method in the above-described embodiment, in other words, other modulation methods can be used as long as the received beam can be separated in the reception process. Further, the present invention can be embodied by modifying the constituent elements without departing from the spirit of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The functional block diagram which shows 1st Embodiment of the radar apparatus concerning this invention. FIG. 2 is a schematic diagram illustrating an example of a transmission beam in the radar apparatus of FIG. 1. FIG. 2 is a schematic diagram illustrating an example of a reception beam in the radar apparatus of FIG. 1. The figure which shows the timing chart of transmission / reception in the radar apparatus of FIG. The figure which shows the angle measurement curve used for angle measurement processing. The functional block diagram which shows 2nd Embodiment of the radar apparatus concerning this invention. The figure which shows the timing chart of transmission / reception in the radar apparatus of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Transmitter, 2 ... Circulator, 3 ... Antenna, 4 ... Receiver, 5 ... Signal processing part, 51 ... Pulse compression processing part, 51a ... Separation part, 52 ... Target detector, 53 ... Angle measurement process, 54 ... Radar control unit

Claims (4)

A transmission unit that divides the radar pulse into a plurality of parts and transmits the signals in directions squinted with respect to each target with different characteristics;
Receiving means for forming a receiving beam and receiving a pulse echo from the target based on the radar pulse;
Separating means for separating the received beam based on the difference in characteristics;
A radar device comprising angle measuring means for measuring a target position by a squint angle measurement method based on mutual reception signals of the separated reception beams. The transmission means, the frequency of the radar pulse divided into a plurality of different from each other,
The radar apparatus according to claim 1, wherein the separation unit separates the reception beam based on the frequency difference. The transmission means makes the modulation characteristics of the plurality of divided radar pulses different from each other,
The radar apparatus according to claim 1, wherein the separation unit separates the reception beam based on the difference in the modulation characteristics. The radar apparatus according to claim 3, wherein the transmission unit transmits linear chirp pulses having different chirp directions.

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