JPH03234128A - Phased array antenna - Google Patents

Abstract

PURPOSE:To shorten a delay time of a feedback loop of a carrier phase correction component by making a part controlling a beam direction independent of a part correcting a phase of a carrier. CONSTITUTION:Conversion means 31-34 convert signals transmitted from antenna elements 11, 12 and processed at pre-stage circuits by using a carrier at a fixed frequency outputted from stationary local oscillation sections 30, 62. Then a signal from a beam direction control means 100 is corrected in a feedback loop in a carrier phase correction means 200. Thus, a beam direction control means 100 and the feedback loop in the carrier phase correction means 200 are provided independently to shorten the delay time in the loop by reference carrier regeneration and a complicated algorithm such as the interference wave elimination algorithm requiring much processing time is applied to the beam direction control means 100.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a phased array antenna that can be used for mobile communications mounted on a mobile body such as an automobile.

[Prior art] Figure 4 shows "Study on DBF antenna for mobile satellite communication with integrated beam forming section and demodulating section" by Nakajo, Iwasaki, and Yasuyo, 1989 IEICE Autumn National Conference, B. 20 is a block diagram of the phased array antenna shown in FIG. In FIG. 4, two antenna elements 1
The radio signals received at 1.21 are each passed through a mixer 13.
23, and the local oscillator 20 is sent to the mixer 13.23.
The signal is mixed with a local oscillation signal supplied from the IF signal and converted into an IF signal. Each 1F signal is then sent from the mixer 13.23 to the A/D converter 17.27 via a band pass filter 14.24 and an IF amplifier 15.25.

The A/D converters 17 and 27 A/D convert the supplied IF multiplied signals, and convert the A/D converted digital I
The F signal S1 is sent to mixers 31 and 32, and the digital I
The F signal S2 is sent to a mixer 33,34. mixer 31
．． 33 is a circuit that multiplies the digital IF signals Sl and S2 by a reference carrier signal Sc generated from a voltage controlled oscillator (C0) 114, which will be described later, and passes only a predetermined low frequency component of this multiplied signal. The signal is sent to a phase shifter 51.53 provided in the beam direction control unit 100 via a low-pass filter 41.43. Also, mixer 3
2.34 is a circuit that multiplies the digital IF signals S1 and S2, respectively, by a signal sent out from the phase shifter 36 after the reference carrier signal Sc is phase-shifted by 90 degrees in the phase shifter 36; The multiplied signal is sent to a phase shifter 52.54 provided in the beam direction control unit 100 via a low-pass filter 42.44 that allows only predetermined low-frequency components to pass.

The beam direction control unit 100 includes four phase shifters 51 to 54 that shift each supplied signal by a predetermined phase shift amount, and four phase shifters 51 to 54 that change the amplitude of the signals sent from the phase shifters 51 to 54.
variable gain amplifiers 61 to 64, and a phase shifter 51, based on the beam direction supplied to the input device 60, so that the beam direction is the beam direction of the receiving phased array antenna or the beam direction supplied to the input device 60. An arithmetic control circuit 50 that controls the calculation of the phase shift amount and amplitude adjustment amount in the amplifiers 61 to 54 and the amplifiers 61 to 64 is provided.

Each signal sent out from the amplifier 6L63 is sent to the adder 110.
The adder 110 adds the two supplied signals and sends the demodulated signal S3 to the outside and to the multiplier 112. Further, each signal sent out from the amplifiers 62 and 64 is supplied to an adder 111 and added, and then the added signal is sent out to a multiplier 112. Furthermore, the multiplier 112
After multiplying the two supplied signals, the multiplied signal is sent to the voltage controlled oscillator 114 via a low pass filter (LPF) 113 that allows only predetermined low frequency components to pass. The voltage controlled oscillator 114 has a free-running oscillation frequency that is approximately the same as the IF frequency, and generates a reference carrier signal Sc having a frequency corresponding to the supplied error signal, and uses this reference carrier signal Sc to control the beam direction. The signal is sent to mixers 31, 33 and phase shifter 36 as local oscillation signals for generating I and Q signals used for this purpose.

The circuits from the mixers 31 to 34 to the voltage controlled oscillator 114 constitute the reference carrier regeneration section 200 enclosed by a dashed line in FIG. The amplitude of the error signal sent out becomes zero, and the voltage controlled oscillator 11
The frequency and phase of the reference carrier signal Sc output from the adder 110 are adjusted such that only the demodulated signal is obtained from the composite signal S3 output from the adder 110.

[Problems to be Solved by the Invention] In the phased array antenna configured as described above, the beam direction control section 100 is connected to the reference carrier regeneration section 20.
The configuration is included in 0.

Therefore, since the delay of the beam direction control section is included in the reference carrier regeneration section 200, there is a problem that the response characteristic of the feedback loop becomes slow.

Regarding the allowable delay time in the feedback loop, see “The 1n
fluence oftime delay on 5
echo-order phase-1ocked
1oopacquisition range,
International, Telee+.

Conf., London, p. 432 (1
963) is 2πΔf·τ=π/2. Here, Δf is the difference between the frequency of the input signal and the free-running frequency of the voltage controlled oscillator, and τ is the delay time. Now, assuming that the frequency for mobile satellite communication is 1.54 GHz, and the local fluctuation of satellite repeaters, etc. is ±lXl0"", Δf-
It becomes ±1.54XIO3. Substituting this, τ≦±15
The time is 4 μsec. In other words, the limit of the delay time that can match the phases of the carrier wave frequency of the radio signal and the reproduced carrier wave frequency is 154 μsec. Now, assuming that the sample rate is 16 kbps and the machine cycle of the digital signal processing processor (DSP) is 5 Q n5ec, the beam forming processing time for the 16 element array is as follows: If one line is formed, it will take 15m5ec, which is a problem in that it exceeds the allowable delay time.

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and provide a phased array antenna with a short loop delay time in a reference carrier regenerating section.

As a similar problem regarding such delays, in the field of data transmission other than the field of antennas, phase-locked loops (P
There is a problem in that the delay of the transversal equalizer is included in L L). However, this problem is solved by constructing a circuit as shown in FIG. Figure 5 shows that detection is performed using a constant frequency carrier wave sent from a local oscillator.
Conventional PL that performs so-called quasi-synchronous detection and performs phase correction for signals whose phase changes after baseband equalization.
It shows L. In FIG. 5, the input signal is supplied to a mixer 331, where it is mixed with a local oscillation signal supplied from a fixed local oscillator 330, converted into a baseband signal, and then converted into a baseband signal. The signal is sent to a tapped delay line 350 provided in the complex transversal equalizer 300 via a low-pass filter 341 that only allows the signal to pass. Complex transversal equalizer 30
0 includes phase shifters 351, 352, and 353 that phase shift the supplied signal by a predetermined phase amount for each tap, and a variable gain amplifier 361 that adjusts the supplied signal by a predetermined amplitude amount.
362, 363, and an adder 310 that adds the signals sent from the phase shifters 351, 352, 353 and the variable gain amplifiers 361, 362, 363.

Phase shifters 351, 352, 353 and variable gain amplifier 36
Each signal sent from 1,362,363 is sent to adder 3
10, added, and then sent to phase shifter 311. The phase shifter 311 is a loop filter 314 which will be described later.
The output signal of the adder 310 is multiplied by the carrier phase correction signal generated by the subtracter 310, and the multiplied signal is sent to the complex determiner 312, the divider 313, and the subtracter 315. Complex determiner 3
12, the position of the data signal is determined, and a divider 313 divides the signals before and after the determination. The error signal generated by divider 313 is sent to loop filter 314. In the feedback loop from the phase shifter 311 to the loop filter 314, the amplitude of the error signal sent from the divider 313 is zero, and the phase of the signal output from the loop filter 314 is determined by the complex determiner 312 so that the correct data is detected. Work as you get.

On the other hand, the subtracter 315 subtracts the signal before complex determination and the signal after determination to generate an error signal. The error signal produced by subtractor 315 is sent to phase shifter 317.

The output signal of the complex conjugator 316 is supplied to the phase shifter 317, and the phase shifter 317 converts the carrier phase correction signal sent from the loop filter 314 into the complex conjugator 316, and performs phase correction on only the signal needle that has the complex conjugate. This phase-corrected signal is output to the arithmetic controller 318. The arithmetic controller 318 includes phase shifters 351, 352, 353 and variable gain amplifiers 361, 3 in the complex transversal equalizer 300.
62 and 363, a control signal is sent out.

The above-mentioned circuit configuration includes a phase shifter 311 and a complex determiner 312.
, the divider 313, and the loop filter 114, and there is a degree of freedom in which the complex transversal equalizer 300 and the PLL can be operated almost independently.

Generally, in the field of communication array antennas, it is necessary to perform beam forming and then demodulate in order to increase the S/N ratio of a received signal. However, in the method of converting the radio signals received by each antenna element into signals having a predetermined phase difference from each other, a reference carrier wave whose frequency and phase exactly match the received carrier wave is required to perform accurate beam formation. It is.

Since this reference carrier wave can only be obtained from the demodulated signal, it has not been easy to construct the circuit configuration as described above.

[Means for Solving the Problems] The phased array antenna of the present invention includes a conversion means for converting each radio signal received by a plurality of antenna elements into signals having a predetermined phase difference from each other, and and beam direction control means for changing the phases of the signals sent out by the conversion means so as to be obtained by the antenna, adding the changed signals and sending out as a composite signal, the phased array antenna having a phased array antenna having a predetermined phase difference between each other. a fixed local oscillation section that oscillates a signal with a fixed frequency and sends the signal to the conversion means; and a carrier phase correction means that corrects the phase of the signal sent from the beam direction control means. shall be.

[Operation 1] With the above configuration, the conversion means uses two local oscillation signals having a phase difference of, for example, 90 degrees from each other based on the fixed frequency signal sent out by the fixed local oscillation unit, converting each radio signal having a modulated user data signal received by each antenna element into first and second signals each having a lower frequency than said radio signal and having a phase difference of, for example, 90 degrees from each other; . The beam direction control means changes the phase of each of the first and second signals outputted from the conversion means so as to obtain a desired beam direction, and adds these signals. The carrier phase correction means corrects the phase of the reference carrier wave based on the signal sent from the beam direction control means to control the phase of the demodulated signal sent out from the antenna device.

In this phased array, the signal sent out from the conversion means is a signal sent out and processed by each antenna element using a fixed frequency carrier wave output from a fixed local oscillation section. The signal sent out from the beam direction control means described above is corrected in a feedback loop by the carrier phase correction means. As described above, since the feedback loops of the beam direction control means and the carrier wave phase correction means are independent, they work to shorten the loop delay time in reference carrier wave regeneration.

Furthermore, since the beam direction control means is independent of the carrier phase correction section, there is an advantage that a complex algorithm that requires processing time, such as an interference wave removal algorithm, can be applied to the beam direction control means.

[Embodiment] FIG. 1 is a block diagram of an embodiment of the phased array antenna of the present invention. In FIG. 1, the same parts as in FIG. 4 are designated by the same reference numerals.

The reception phased array antenna of this embodiment includes a beam direction control section 100 that controls the beam direction using the ■ signal and Q signal generated from the received signal, and the ■ signal and Q signal obtained from the beam direction control section 100. a carrier wave phase correction unit 200 which multiplies the carrier wave phase correction signal and reproduces a carrier wave phase correction signal based on the multiplied signal, and multiplies the carrier wave phase correction signal and the output signal from the beam direction control unit 100 to form a phased lock loop. It is characterized by being configured independently. Note that the radio signal received by this receiving phased array antenna is modulated with a data signal on the transmitting side.

In FIG. 1, radio signals received by two antenna elements 11.21 are sent to mixers 13.23, where they are mixed with a local oscillation signal supplied from a local oscillator 20. The signal is then converted into an IF signal. Then, each IF multiplied signal from the mixer 13.23 is passed through the bandpass filter 14.24 and the IF amplifier 15.25 to the A/D
It is sent to converter 17.27.

The A/D converters 17 and 27 A/D convert the supplied IF multiplied signals, send the A/D converted digital IF signals S1 to mixers 3], 32, and convert them into digital IFs.
The signal S2 is sent to a mixer 33.34. Mixer 31.
33 is a circuit that multiplies the digital IF signals Sl and S2 by a carrier signal generated by the fixed local oscillator 30, and low-pass filters 41 and 43 pass only predetermined low-frequency components of the multiplied signals. The signal is sent to the phase shifters 51 and 53 provided in the beam direction control section 100 via. The mixers 32 and 34 are circuits that multiply the digital IF signals Sl and S2 by a signal sent out from the phase shifter 36, which is phase-shifted by 90 degrees from the carrier signal, and the multiplied signals are The signal is sent to a phase shifter 52.54 provided in the beam direction control unit 100 via a low-pass filter 42.44 that allows only predetermined low-frequency components to pass.

The beam direction control unit 100 includes four phase shifters 51 to 54 that shift each supplied signal by a predetermined phase shift amount, and four phase shifters 51 to 54 that change the amplitude of the signals sent out by the phase shifters 51 to 54. variable gain amplifiers 61 to 64, and phase shifters 51 to 64 so that the beam direction supplied to the input device 60 is the beam direction of the receiving phased array antenna or the beam direction supplied to the input device 60. 54 and the amplifiers 61 to 64.

Each signal sent out from the amplifiers 61 and 63 is sent to the adder 11.
0 and then the summed signal is sent to phase shifter 115. Further, each signal sent from the amplifiers 62 and 64 is supplied to an adder 111 and added, and then the added signal is sent to a phase shifter 116. The phase shifters 115 and 116 each multiply the above addition signal by a carrier phase correction signal Sc supplied from a loop filter 117, which will be described later, and send the multiplied signals to the multiplier 1, respectively.
Send on 12th. Note that by performing the above multiplication, the phases of the signals sent from the adders 110 and 111 are shifted. Multiplier 112 multiplies the two supplied signals,
The multiplied signal is sent to loop filter 117.

The carrier phase correction unit 20 includes the phase shifters 115 and 116, the multiplier 112, and the loop filter 117.
It constitutes 0. The phased pack loop in this carrier phase correction section 200 is configured so that the amplitude of the error signal sent from the multiplier 112 becomes zero and a demodulated signal is obtained from the composite signal S3 sent from the phase shifter 115.
The phase of the carrier phase correction signal sent from loop filter 117 is controlled.

Whether the quasi-synchronous detection method, which uses a fixed local oscillator to handle signals whose frequency and phase do not exactly match the received carrier frequency, can be applied to the beam forming method of a phased array antenna depends on its frequency characteristics, that is, the frequency deviation. All you need to do is investigate the beam forming accuracy when

FIG. 2 shows the calculation of the amount of gain reduction when there is a frequency deviation when a planar 16-element array is scanned from the front in a 60 degree direction. Here, in order to simplify the problem, calculations are made assuming that the element spacing is 0.5 wavelength and that the elements are non-directional. Usually, the frequency fluctuation of a satellite system is ±1xio-5 ~
It is about 10-8, that is, 0.001 to 0.0001%, and from the graph of the gain reduction amount in FIG. 2, it can be seen that there is no problem.

Further, among the circuits of this embodiment, the operation of the digital circuits after the A/D converter 17, 27 can be performed using software of a digital signal processor (DSP). The beam direction control section 100 is a part that requires signal processing time, and if the beam direction control section 100 is included in the fused backlube of the carrier phase correction section, a large delay will occur, making it difficult to reproduce the reference carrier wave. However, the beam direction control section 100 and the carrier phase correction section 200
By making these independent, there is an advantage that the possibility of real-time processing in the DSP increases.

Other Embodiments In the above embodiment, two antenna elements 11.21
However, the present invention is not limited to this, and as shown in FIG. 3, the present invention can be applied to a receiving phased array antenna using three or more antenna elements. Further, in the above embodiment, an example is described in which the carrier phase correction section 200 uses a Costas loop when demodulating a PSK signal, but the present invention is not limited to this, and the present invention can also be applied to a QAM signal. I can do it.

[Effects of the Invention] According to the present invention, as described in detail below, in the double array antenna, the part that controls the beam direction and the part that corrects the carrier wave phase are made independent, so that the carrier wave phase can be adjusted. It is possible to shorten the delay time of the foot loop in the correction part. Also, the beam direction control section has the advantage of being able to perform complex processing with a large delay time.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the phased array antenna of the present invention, FIG. 2 is a graph showing the beam forming accuracy of the phased array antenna shown in FIG. 4 and 5 are block diagrams showing the configuration of a conventional phased array antenna. 11.21... Antenna element, O... Fixed local oscillator, 31 to 34... Mixer,
1 to 54・Phase shifter, OO... Beam direction control unit, 112... Multiplier, 15
．． 116-Phase shifter, OO...Carrier phase correction unit.

Claims (2)

[Claims] (1) converting means for converting each radio signal received by a plurality of antenna elements into signals having a predetermined phase difference from each other;
A phased array antenna comprising: beam direction control means for changing the phases of the signals sent by the converting means so that a desired beam direction is obtained by the array antenna, adding the changed signals and sending out as a composite signal, a fixed local oscillation unit that oscillates fixed frequency signals having a predetermined phase difference from each other and sends the signals to the conversion means; a carrier phase correction unit that corrects the phase of the signal sent from the beam direction control means; A phased array antenna characterized by being equipped with. (2) The carrier wave phase correction means includes a phase shift means for shifting the phase of the signal sent out from the beam direction control means using a local oscillation signal, and a phase shift means for sending out a demodulated signal to the outside of the device. a multiplication means for multiplying the respective output signals; and a carrier wave phase correction signal having the same phase as the phase of the signal supplied from the beam direction control means based on the signal sent by the multiplication means; 2. The phased array antenna according to claim 1, further comprising a correction means for sending a correction signal as a local oscillation signal to said phase shifting means.