JPH0549071B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improving the all-round scanning performance of a holographic radar.

[Conventional technology]

Figure 3 is from the international academic journal “Eascon-78”
ABRAHAM E.RUVIN and LEONARD Weinberg (IEEE, EASCON-78)
WEINBERG)'s paper ``Digital multi-beam forming technology for radar (DIGITAL
MALTIDPLE BEAMFORMING
1 is a diagram showing the configuration of a conventional holographic radar shown in ``TECHNIQUES FOR RADDAR''. In the figure, 1 is an element antenna, 2 is an antenna array consisting of N element antennas, 3 is an RF amplifier connected to each element antenna 1 and amplifies the high frequency signal received by the element antenna 1, and 4 is an RF amplifier that amplifies the high frequency signal received by the element antenna 1. a mixer for converting into an intermediate frequency signal, 5
is an IF amplifier that amplifies the intermediate frequency signal output from mixer 4, 6 is a phase detector that converts the IF amplifier output into a baseband complex video signal while preserving the phase of the intermediate frequency signal, and 7 is a phase detector. I (in phase) channel and Q of device 6
(quadrature) A low pass filter (LPF) connected to each output of the channel, 8 an A/D converter connected to the LDF 7 and converting the complex video signal converted to baseband into A/D, 9 a beam shape an output level adjuster that performs weighting to adjust the sidelobe level of the
This is a receiver composed of ~9. A digital multi-beam former 11 forms a number of multi-beams corresponding to the number of element antennas by performing digital calculations on the output of the receiver 10 connected to each element antenna 1.

Next, the operation will be explained.

The high frequency signal received by the N element antennas 1 is amplified by the RF amplifier 3, converted to an intermediate frequency signal by the mixer 4, and amplified again by the IF amplifier 5. This intermediate frequency signal is phase detected by a phase detector 6 and converted into a complex video signal consisting of an I channel and a Q channel. After the complex video signal is band-limited by LPF 7, it is sent to A/D converter 8.
The signal is converted into a digital complex video signal by the output level adjuster 9 for weighting to reduce side lobes during beam forming, and then input to the digital multi-beam forming means 11. At this time, as shown in Fig. 4, the direction in which the N element antennas are lined up is the X axis, the angle between the arrival direction of the high frequency signal, that is, the radio wave, and the X axis is the arrival angle α of the radio wave, and the If the distance between the antennas 1 is d and the wavelength is λ, the phase difference between signals received by adjacent element antennas is 2π(d cos α1)/λ. Therefore, in the digital multi-beam former 11, the following ( 1) Formula Br= _N/2-1 〓 〓 ^k=-N/2 exp(j2πk d cos α/λ)・exp(−j(2π
/N)kr)…(1) r=-N/,-N/2+1,…,0,…,N/
By calculating 2-1, αr=cos ^-1 (rλ/Nd)
N beams with maximum gain (r=-N/
2,...,0,...,N/2-1) can be formed simultaneously. However, in Equation (1), Wk is a weighting coefficient for sidelobe suppression, and is given by the output level adjuster 9 in the receiver 10 connected to each antenna element.

At this time, the beam width δr of the r-th beam is given by the following equation (2) δr=wλ/Ndsinαr (2), and the interval Δαr between the r-th and r-1th beams is the beam width δr of the r-th beam. (3) Formula Δαr=αr−αr−1=λ/Ndsinαr……(3) is given. w in equation (2) is a constant determined by the weighting coefficient Wk, and is generally set to about 0.88 to 1.3. In the digital multi-beam forming means 11, Equation (1) is expressed as DFT (Discrete Foueier
Transform). For this reason,
In holographic radar, FFT (Fast
Fourier Transform) algorithm is used.

[Problem that the invention seeks to solve]

Conventional holographic radars are configured as described above, so the observation range is limited to the beam width of one element antenna (approximately 120 degrees), and in order to achieve full-circle scanning, one unit is required. It is necessary to rotate the radar mechanically or to divide the observation range between 3 or 4 radars, and when rotating one radar mechanically, the beam scans to match the target at a short distance. If the speed is set, the required number of pulse hits for a target at a long distance will be insufficient, making it impossible to detect the target; conversely, if the beam scanning speed is set to match a target at a long distance, the data rate for a target at a short distance will decrease. There are problems such as a decrease in the overall scanning time and a longer full-circle scanning time.
When the observation range was divided between multiple radars, there were problems such as the overall cost of the equipment.

The present invention has been made to solve the above-mentioned problems, and its object is to provide a holographic radar that is inexpensive and capable of scanning the entire circumference in a short time.

[Means for solving problems]

In the holographic radar according to the present invention, only the antenna array has three or four sides, and the connection between the receiver corresponding to one side and each antenna array is changed by a switch, and the switching timing of this switch is set as required. A switch control means that independently performs beam forming for each range bin by digital calculation based on the number of pulse hits, the pulse hit number, and the range bin number, and controls the connection between the antenna surface and the receiver in accordance with the required number of pulse hits for each range bin. It has been established.

[Effect]

The holographic radar in this invention is
The switch control means controls the switching timing of the switch based on the required number of pulse hits, pulse hit number and range bin number.
Since the connection between the plane antenna array and the receivers corresponding to one plane is changed over by the above switch, high-speed all-round scanning can be achieved at the optimum frame rate for each range bin.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 12 is a switch that changes the connection between the four antenna arrays 2 and the receivers 10 corresponding to one antenna array surface, and 13 is a switch that controls the switching timing of the switch 12 based on the transmission pulse number and range bin number. This is a switch control means. Note that each part numbered 1 to 11 is the same part or means as in a conventional holographic radar.

Next, the operation will be explained. The operations of the receiver 10 and the digital multi-beam former 11 are the same as those of a conventional holographic radar, so they will be omitted, and the operations of the switch 12 and switch control means 13 newly added in this embodiment will be explained in detail. explain.

Now, the holographic radar has four sides (D ₀ , D ₁ ,
_{D 2} , D ₃ ), and as shown in FIG _.
Assume that each direction is shared. At this time,
Transmitting antenna gain is Gt, receiving antenna gain after multi-beam forming is Gr, transmitting wavelength is λ, transmitting peak power is Pt, target radar cross section is σ, required signal-to-noise power ratio is SNR, Boltzmann constant is K , where T is the absolute temperature, B is the receiver bandwidth, NF is the receiver noise figure, L is the system loss, ΔR is the range resolution, and k is the range bin number, the number of coherent integrals required in the kth range bin, i.e. The number of pulse hits Nk is given by equation (4).

Nk={(4π) ³ KTB(NF)L(SNR)(ΔR) ⁴ /Pt Gt Gr
λ ² σ}・k ⁴ …(4) In equation (4), the parameters in { } are:
Since both are constants specific to each radar system, the required number of pulse hits Nk is proportional to the fourth power of the range bin number k.

The switch control means 13 uses radar system specific parameters K, T, B, NF, L, SNR,
Using Δ4R, Pt, Gt, Gr, λ, and σ, the required number of pulse hits Nk for each range bin is calculated by equation (4).
seek. Then, for each transmission pulse, the quotient lk lk = [m/Nk] (5) is calculated by dividing the current transmission pulse signal m by the required number of pulse hits Nk for the range bin number k. In equation (5), [ ] represents a Gaussian symbol. Furthermore, find the remainder Jk when lk is divided by the number of antenna array surfaces, 4, and if Jk = 0, switch 1
2 to D ₀ of antenna array 2 and receiver 1.
0, and if Jk=1, connect _D1 , if Jk=2, connect _D2 , and if Jk=3, connect _D3 to the receiver 10. By performing the above operation for all range bin numbers k of all transmission pulse signals m, a receiver corresponding to one antenna array can obtain
Full-circle scanning can be achieved faster than conventional devices that rotate the radar mechanically.

In addition, in this embodiment, for all range bins, a sufficient data rate can be ensured for the range bins at a short distance as if the antenna were rotating at high speed, and at the same time, for the range bin at a long distance, the antenna rotates at a slow speed. The switching timing of the switch is controlled based on the required number of pulse hits so that a sufficient number of pulse hits can be obtained as if the number of pulses were the same. You can optimize your time.

〔Effect of the invention〕

As described above, according to the present invention, full-circle scanning can be realized by using only three or four antenna arrays and switching between each antenna array and a receiver corresponding to one surface using a switch. Therefore, the device can be manufactured at a low cost, and it is possible to scan the entire circumference at high speed.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a holographic radar according to an embodiment of the present invention, FIG. 2 is a diagram showing a four-sided antenna array, FIG. 3 is a diagram showing the configuration of a conventional holographic radar, and FIG. The figure is a diagram for explaining the operating principle of the holographic radar. 1...Element antenna, 2...Antenna array,
10...Receiver, 11...Digital multi-beam forming means, 12...Switch, 13...Switch control means. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. An antenna array on a plurality of surfaces each consisting of two or more element antennas of the same number, one element antenna constituting the antenna array on one surface, and another surface corresponding to this one element antenna. the same number of switches as the number of element antennas, each of which selects one of the element antennas constituting the antenna array; the same number of receivers as the element antennas connected to the antenna; a switch control means for controlling the switching timing of the switch based on the required number of pulse hits for each range bin number, the pulse hit number and the range bin number; A holographic radar comprising: digital multi-beam forming means for forming multi-beams using digital complex video signals output from a receiver.