JPH0783208B2 - Beam forming method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a beam forming method in an array antenna formed on an arbitrary curved surface.

[Prior Art] Although the following description will be given for the reception array antenna, the control operation is the same as that for reception even when the antenna is used as a transmission antenna.

Conventionally, a planar array antenna is mainly used as an electronic scanning antenna, and by changing the phase of the received signal of each antenna element with a phase shifter inserted in the middle of the feeding line of each antenna element, It is scanning.
In order to obtain a directivity (beam) in a desired direction with such a planar array antenna, the beam is obtained in the desired direction based on an instruction from a separately provided phase shifter controller. Need to know the direction of arrival.

On the other hand, a phased lock loop array antenna is known as one that does not require the setting of the direction of arrival of a received signal, and a beam forming method in this antenna will be described with reference to FIG.

The received signal from each antenna element A1 to A3 is sent to each mixer M1 to M3.
After, through the synthesizer C1 is synthesized with each other, by the phase detector PD1 ~ PD3, the phase shift of each of those received signals is detected based on the reference signal from the reference signal generator R1, The voltage controlled oscillators V1 to V3 align the phases of the received signals of the antenna elements A1 to A3 by the mixers M1 to M3 so that the detected phase shifts disappear.

FIG. 4 shows a conformal array antenna using another beam forming method.

The antenna elements A1 to A9 are made up of groups of antenna elements that are appropriately divided into groups, and each group forms a subarray by selecting one element at a time from the switch circuits S1 to S3. Is input to the phase shifters P1 and P2 via the switch matrix SM1, where the phase adjustment is performed for the elements requiring phase adjustment, and the combiner C1
A beam is formed at.

An amplitude adjuster can also be used in this system, but it is omitted in FIG. 4 to simplify the circuit.

[Problems to be Solved by the Invention] However, the phased-lock loop antenna shown in FIG. 3 is generally intended for a planar array, and a conformal array such as a spherical or cylindrical array does not receive a signal depending on the direction of arrival of a received signal. Since there are elements, how to handle such elements became a problem.

On the other hand, the antenna shown in FIG. 4 is an antenna intended for a conformal array, but such a switching array has a drawback that it always involves crossover loss, unlike a phased array that continuously scans. , If the number of elements used at one time is increasing as in the case of scanning a beam by controlling a large number of elements that contribute to the beam forming direction, or if continuous beam scanning is attempted, the elements used for each beam will overlap. Therefore, even if the sub-array is formed in advance, there is a drawback that the distribution and synthesis circuit becomes complicated.

The present invention has been made to eliminate the above-mentioned problems, and by selecting an element that contributes to beam forming by using an incident signal at the time of reception, beam forming is possible without knowing the arrival direction of the received signal. It is an object of the present invention to provide a beam forming method capable of performing the above-mentioned operation and the amplitude adjustment and further reducing the number of complicated phase detection circuits as much as possible.

[Means for Solving the Problems] A beam forming method according to the first invention is a beam forming method for an array antenna in which a plurality of antenna elements are arranged on a transmitting / receiving surface having an arbitrary curved surface, and each antenna element has an envelope. A line detector is provided to select an antenna element in which a received signal induced in each antenna element has a constant amplitude level or more, and a desired beam is formed based on the received signal from the selected antenna element. .

A beam forming method according to a second invention is a beam forming method of an array antenna in which a plurality of antenna elements are arranged on a transmitting / receiving surface having an arbitrary curved surface, wherein each antenna element is provided with an envelope detector, and each antenna element is provided with an envelope detector. It is characterized in that an antenna element whose received signal induced in the element is equal to or higher than a predetermined amplitude level is selected, and amplitude adjustment is performed using the amplitude level of the received signal from the selected antenna element to form a desired beam.

[Operation] When the incoming signal is a CW (continuous wave) signal such as a pilot signal or when a constant envelope modulation method such as PSK or MSK is used as the modulation method, the reception method is targeted This is a method in which an antenna element that contributes to reception is selected by detecting the envelope level of the signal of, and the beam is formed by adjusting the amplitude and phase of the signal from the selected antenna element.

[Embodiment] FIG. 1 shows an embodiment of a conformal array antenna to which the beam forming method of the present invention is applied. A1 ~
A5 is an antenna element, and AM1 to AM5 are envelope detectors that perform envelope detection to detect the amplitude value in the received signals from the antenna elements A1 to A5, respectively. The antenna elements A1 to A5 are arranged on an arbitrary curved surface such as a spherical surface so as to form one antenna array. AC1 is an amplitude comparison circuit that compares the envelope level obtained from the detection signals from the envelope detectors AM1 to AM5 with a predetermined set level.
AS1 is an amplitude control / switching circuit, which is provided on the line from each antenna element A1 to A5 when the received signal level from each antenna element A1 to A5 is below the set level based on the comparison result of the amplitude comparison circuit AC1. Mixers M1 to M5
On the other hand, when the received signal level exceeds the set level, the mixers M1 to M5 are turned on and the amplitude value of the received signal is controlled as described later.
PD1 to PD3 are the antenna elements A1 via mixers M1 to M3.
~ A3 is a phase detector for detecting the phase of the received signal. PC1 is a phase comparison circuit that compares the phases between the antenna elements from the phases detected by the phase detection units PD1 to PD3, and PCC1 is a phase control circuit, and the phase comparison circuit PC1
Based on the comparison result of (1), phase control is performed by mixers (M6 to M8) provided on each line so that the received signals from the antenna elements (A1 to A3) have no phase difference. C1 is a combiner that combines the reception signals from the antenna elements A1 to A3 that have the same phase.

Next, the function of the conformal array antenna having the above configuration will be described.

Now, it is assumed that a radio wave arrives from a direction deviating from the directivity of the antenna elements A4 and A5, though the radio waves almost match the antenna directing directions of the antenna elements A1 to A3. The received signals obtained by these antenna elements A1 to A5 are the envelope detectors AM1 to A1.
The envelope level detected by M5 is the amplitude comparison circuit AC
At 1, it is compared with the preset level. At this time, the received signals from the antenna elements A4 and A5 that do not reach the set level are blocked by the mixers M4 and M5 by the switching of the amplitude control / switching circuit AS1, but the received signals from the antenna elements A1 to A3. Exceeds the set level, the mixers M1 to M3 are turned on by the switching of the amplitude control / switching circuit AS1, and the mixers M1 to M3 are guided to the phase adjusting unit in the subsequent stage. The envelope detectors AM1 to AM5 are basically for dividing into elements that contribute to beam forming and elements that do not, but at the same time, the mutual envelope level among the elements that contribute to beam forming is Since it is possible to know the degree of contribution of each antenna element to the signal arrival direction, the amplitude control so as to have the maximum directional gain or the low sidelobe characteristic based on this information.・ Switching circuit AS
The amplitude control of 1 controls the amplitude of each received signal to an optimum value.

Here, in principle, the envelope detectors AM1 to AM5 are required for the number of antenna elements, but this envelope detector simply rectifies the received signal by rectifying it with a rectifier and does not require a local signal. This has the advantage that it can be configured relatively easily, and the number of envelope detectors can be reduced if transmission speed is not a problem. In that case, the envelope level of each element antenna can be changed by switching. I can know.

Now, in the phase adjustment unit, the respective phases of the reception signals that have passed through the mixers M1 to M3 are detected by the phase detection units PD1 to PD3, and in the phase comparison circuit PC1, the phases between the reception signals are compared, and the phase control circuit PCC1 The phases are adjusted by mixers M6 to M8 so that they have the same phase. The principle of this phase adjustment unit is the same as the principle of the beam forming method using the phased lock array shown in FIG.

The signals thus adjusted in amplitude and phase are finally combined by the combiner C1 to obtain the desired gain.

By the way, the meaning of the phase adjustment in the conformal array means the correction of the phase difference between the antenna elements depending on the direction of arrival of the received signal and the phase correction for the adjustment of the polarization plane of each antenna element. Although the phases of the antenna elements are adjusted to be in phase, it is also possible to arbitrarily change the phase aiming at the low side lobe characteristic.

As described above, in this embodiment, the number of phase detection circuits that require carrier wave and clock recovery can be reduced by selecting the necessary element antennas based on the amplitude information before performing phase detection, and the circuit can be simplified. Turn into.

Although the present invention can be realized regardless of whether it is an analog circuit or a digital circuit, it is preferable to use a digital signal processing technique in terms of suppressing variations among the antenna element systems as much as possible and handling control signal switching easily. Seems to be desirable. A method of using digital synchronization information can be considered for the selection of the antenna element by using the digital information. For example, an example of the antenna element selection method using the frame synchronization information is shown in FIG.

A1 to A5 are element antennas, and DM1 to DM5 are demodulators that demodulate the digital signals received by the antenna elements A1 to A5 into a predetermined signal form. FS1 to FS5 are frame synchronization circuits that detect the frame synchronization signal and maintain the frame synchronization.By periodically inserting this frame synchronization signal into the transmission signal in digital wireless communication, various digital signals can be received on the receiving side. It is designed to achieve proper synchronization (word synchronization of PCM signals, etc.). The FSC1 is a determination circuit, and the frame synchronization circuits FS1 to FS5 compare the frame synchronization signal with the internal synchronization signal, and if the patterns match for a certain number of bits or more, it is determined that synchronization is achieved. SC1 is a switching circuit, which selects the received signal from the synchronized antenna element according to the judgment of the judgment circuit FSC1 and synthesizes it.
Send to C1.

In this embodiment, the determination circuit FSC1 determines whether or not synchronization is maintained using each frame synchronization signal from the frame synchronization circuits FS1 to FS5, and a method of selecting an antenna element in synchronization is used. is there.

In addition to this, as a method of using such synchronization information, in a communication system using an error correction code, a method of using synchronization information in an error correction system (for example, word synchronization information in a block code) is also considered. To be

[Advantages of the Invention] In a conformal array such as a spherical array or a cylindrical array, complicated amplitude / phase control is required to perform beam scanning, and a phased array that controls all element antennas that contribute to beam formation. Is difficult to achieve. Therefore, a switching array is usually used.
However, according to the present invention, by using the amplitude information of the received signal, it is possible to automatically select the antenna elements that contribute to beam forming and at the same time to know the degree of contribution of each antenna element. Adjustment can be simplified, and complicated amplitude-phase control in a conformal array can be simplified.

Especially in a moving body such as a car, an aircraft, or a satellite, the antenna installation space is limited, so an antenna that fits the shape of the moving body is required, and an antenna that can function as a phased array antenna regardless of the mounting location Development is desired. By using this beam forming method for such an array antenna of a moving body,
It is possible to automatically select the element antenna to be used according to the beam direction regardless of the array shape and perform amplitude and phase control, and it is possible to realize a mobile communication antenna with good characteristics.

[Brief description of drawings]

FIG. 1 is a control circuit diagram showing an embodiment of a conformal array antenna to which the beam forming method of the present invention is applied, and FIG. 2 uses synchronization information using digital signal processing technology in the beam forming method of the present invention. FIG. 3 is a control circuit diagram showing an example of the conformal array antenna, FIG. 3 is a control circuit diagram for beam forming in the conventional phase-locked loop array antenna, and FIG. 4 is control for beam forming in the conformal array antenna. It is a circuit diagram. A1 to A5 …… antenna element, AM1 to AM5 …… envelope detector,
AC1 …… Amplitude comparison circuit, AS1 …… Amplitude control / switching circuit, M1 to M8 …… Mixer, PD1 to PD3 …… Phase detector,
PC1 …… Phase comparison circuit, PCC1 …… Phase control circuit, C1 ……
Synthesizer, DM1 to DM5 ... Demodulator, FS1 to FS5 ... X2 frame synchronization circuit, FSC1 ... Judgment circuit, SC1 ... Switching circuit.

Front Page Continuation (72) Inventor Kanshiro Kashiki, Shiraka-cho, Soraku-gun, Kyoto Prefecture 5 Sanpani, Osamu Osamu, Kyoto, Japan At RT Optical Hikari Radio Communications Research Laboratories, Inc. (72) Koji Yasukawa, Seika, Soraku-gun, Kyoto Machidaiji, Inui-ya, Mi-tani, 5 Address, ATR, Inc., Optical Radio Communications Laboratory (56) References JP-A-63-217702 (JP, A)

Claims (2)

[Claims] 1. A beam forming method for an array antenna in which a plurality of antenna elements are arranged on a transmitting / receiving surface having an arbitrary curved surface, wherein an envelope detector is provided for each antenna element, and reception induced by each antenna element is performed. A beam forming method, which comprises selecting an antenna element having a signal having a predetermined amplitude level or more and forming a desired beam based on a received signal from the selected antenna element. 2. A beam forming method for an array antenna in which a plurality of antenna elements are arranged on a transmitting / receiving surface having an arbitrary curved surface, wherein each antenna element is provided with an envelope detector to induce reception in each antenna element. A beam forming method, comprising: selecting an antenna element having a signal having a predetermined amplitude level or more, and performing amplitude adjustment using the amplitude level of a received signal from the selected antenna element to form a desired beam.