JP2851349B2 - Array antenna in-phase synthesizer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an adaptive array antenna, and more particularly to an array antenna in-phase synthesizer for automatically directing and tracking a beam in a radio wave arrival direction.

(Summary of the Invention) The present invention is an operation for performing an tracking operation by always synthesizing the outputs of the antenna elements in the same phase in an adaptive array antenna that performs automatic tracking by mobile radio or the like. After the output of each antenna element is once converted to an intermediate frequency by a frequency converter that is a reception front end having an independent local oscillator, the outputs are combined in phase in a phase locked loop, and the gain and band characteristics of the phase locked loop Or, by switching or changing the time constant, by keeping both the retracting range and the locking range in a wide range,
This makes it possible to use an independent local oscillator, thereby achieving the price reduction and stable operation of the synthesizer.

(Prior Art) Generally, in mobile communication and mobile reception of broadcasting in which the direction of arrival of radio waves changes indefinitely, it is necessary to always direct an antenna beam in the direction of arrival of radio waves. With omni-directional antennas, such beam steering is unnecessary.
However, an omnidirectional antenna has a low antenna gain, a large transmission power, and is susceptible to interference from other directions. For this purpose, the antenna beam is electronically controlled and tracked,
One of the methods for constantly directing a beam in the direction of arrival of a radio wave is an adaptive array antenna. This antenna has a faster tracking speed than mechanical control, and is effective when performing high-speed tracking for vehicles and the like.

(Problems to be Solved by the Invention) However, in this method, it is necessary to widen the directivity of the antenna element alone in order to widen the tracking range, and the gain of the element is reduced. Requires a large number of elements to be synthesized. When detecting the phase of the received signal and performing phase tracking so that in-phase synthesis is performed, the C / N of the received signal by the element itself becomes a low value, so the phase detection accuracy decreases, and especially wideband FM modulation is performed In the case of system or satellite radio wave reception, the C / N was low, making it difficult to achieve a high-performance configuration.

In addition, a phase shifter and a phase shifter control circuit for controlling the phase of each antenna element output to be in phase are required, and the phase shifter control circuit calculates the phase of each antenna element output from information on the radio wave arrival direction. When performing calculations and performing in-phase synthesis operations, it is necessary to use a common local oscillator for the frequency converters so that phase information is not lost by frequency conversion, and to distribute the local oscillation output to each frequency converter. There are also problems to be solved such that the restrictions on the configuration or arrangement of the pipe for laying the pipe or the coaxial line are complicated and the cost is increased.

Also, in a high frequency region such as a microwave band or a millimeter wave band, there is a problem that the insertion loss of the variable phase shifter is large and complicated and expensive when performing fine phase control.

The present invention effectively solves the problems of the prior art, simplifies the configuration, corrects the generated phase and frequency shifts, synthesizes in phase, stabilizes the tracking operation of the antenna beam, and expands the tracking range. It is an object of the present invention to provide an array antenna in-phase synthesizing device.

(Means for Solving the Problems) In order to achieve such an object, the present invention provides a plurality of local oscillators for converting each element output of a plurality of adaptive array antennas into an independent intermediate frequency. A receiving front end having a phase difference between the output of the other intermediate frequency and the gain, band characteristic, or time constant connected to the receiving front end. And a phase-locked loop for switching or changing the phase and combining them in phase.

Further, the phase locked loop is a variable frequency oscillator whose frequency is controlled by the phase discrimination output, a pulse generator driven by the variable frequency oscillator to generate sampling pulses having a phase difference of 90 degrees from each other, and the variable frequency oscillator A fixed frequency oscillator that oscillates a sine wave fixed frequency of substantially the same frequency, and the output of the fixed frequency oscillator is sampled and held by the sampling pulse.
A sample and hold circuit that generates a voltage corresponding to sin θ and cos θ with the phase of the variable frequency oscillator output relative to the fixed frequency oscillator output as θ as two voltages corresponding to the 90-degree phase difference, and the sin θ and cos θ voltage It is characterized by comprising an infinite phase shifter configured by a resolver circuit that drives and shifts the phase shift of the input intermediate frequency by θ.

(Operation) Such an in-phase synthesizing device may become unstable when the frequency shift is large and the C / N of the input signal is poor, but the output of each antenna element is always synthesized in the same phase. By adjusting the tracking operation, the output of each antenna element is once converted to an intermediate frequency by a frequency converter having an independent local oscillator, and then the respective outputs are made in phase by adaptively controlling the phase lock loop itself. Combining, switching or changing the gain, band characteristic or time constant of the phase locked loop, holding both the pull-in range and the lock range over a wide range, enabling the use of an independent local oscillator, stabilizing its operation, An infinite phase shifter that performs phase lock is implemented by a simple circuit configuration using a resolver circuit.
High-speed, high-precision operation can be achieved.

(Example) Next, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an array antenna in-phase synthesizer according to the present invention. Array antenna in-phase synthesizer
100 is mainly a plurality of antenna elements, two antenna elements 1 and 2 in this embodiment, and frequency converters 3 and 4 as reception front ends.
And a phase locked loop 12. The phase locked loop 12 includes an infinite phase shifter 5, a bandpass filter 6,
, A phase detector 8, a variable reduction filter 9, an out-of-lock detector 10 and a combiner 11. Among them, the frequency converters 3 and 4 include independent local oscillators for frequency-converting the outputs of the antenna elements 1 and 2, respectively. The infinite phase shifter 5 changes the output phase of the frequency converter 3 to match the output phase of the frequency converter 4. Bandpass filters 6 and 7 are
A necessary signal component is extracted from the outputs of the infinite phase shifter 5 and the frequency converter 4. The phase detector 8 includes bandpass filters 6 and 7
And outputs a signal corresponding to the phase difference.

The variable low-pass filter 9 extracts a low-frequency component of the output of the phase detector 8 and changes the gain and the band characteristic. An out-of-lock detector 10 detects a ripple voltage generated at the time of out-of-lock in the phase lock loop 12, and controls the gain and band characteristics of the variable low-pass filter 9. Synthesizer 11
Is combined with the output of the frequency converter 4 and the output of the infinite phase shifter 5 which has the same phase as this output, and outputs the result.

With such a configuration, when the outputs of the antenna elements 1 and 2 are converted to the first intermediate frequency by the independent frequency converters 3 and 4, respectively, the local oscillation frequencies of the frequency converters 3 and 4 are not the same. , Their phases and frequencies are different. The infinite phase shifter 5 automatically adjusts this frequency to the same frequency and the same phase again. This automatic adjustment is performed by a field-back circuit that drives the infinite phase shifter 5 so that the phase difference between the two outputs is detected and the phases become the same. Since the stationary phase difference correction is the same as changing the frequency, the frequency can also be corrected by the infinite phase shifter 5.

While this filled back circuit is operating normally,
The output of the phase detector 8 drives the infinite phase shifter 5 with almost zero and a slight DC error voltage. Therefore, if the cut-off frequency of the variable low-pass filter 9 is lowered and the loop gain is set high, the effect of noise due to C / N reduction can be eliminated, and by performing stable operation, the lock range can be widened. Become. However, if the lock is released for some reason, re-acquisition may become difficult because the loop is set to a high gain and a narrow band. Therefore, the band characteristic of the variable low-pass filter 9 is expanded so that the frequency shift caused by the frequency converters 3 and 4 can be corrected.

However, if the band is widened, the operation becomes unstable due to noise. Therefore, the variable low-pass filter 9 is controlled so as to optimize the loop gain. As a result, the capture range is widened and re-capture is easy. Once captured and locked, the variable low-pass filter 9 can be controlled again to form a narrow-band high-gain loop and stabilize the phase-locked loop 12. When the phase lock loop 12 is unlocked, a ripple voltage corresponding to the frequency difference is generated in the output of the variable low-pass filter 9, and this ripple voltage is detected and used as a loop control voltage.

Next, FIG. 2 shows a schematic configuration diagram of another embodiment of the present invention. The array antenna in-phase synthesizing device 200 mainly includes a plurality of, in this embodiment, two antenna elements 1 and 2, frequency converters 3 and 4 serving as reception front ends, and a phase lock loop 25. This phase locked loop 25
Are the mixers 13 and 14, the voltage variable local oscillator 15, the fixed local oscillator 16, the bandpass filters 17 and 18, the phase detector 19, the narrowband lowpass filter 20, the wideband lowpass filter 21, the changeover switch 2.
2. It comprises a ripple detector 23 and a synthesizer 24. Among them, the frequency converters 3 and 4 convert the outputs of the antenna elements 1 and 2 into independent first intermediate frequencies. In addition, the mixers 13 and 14, the voltage-variable local wave oscillator 15 and the local oscillator 1
6 converts the first intermediate frequency of the frequency converters 3 and 4 into a second intermediate frequency.

The band filters 17 and 18 extract necessary signals from the second intermediate frequency. The phase detector 19 compares the phases of the output signals of the bandpass filters 17 and 18 and outputs a signal corresponding to the phase difference. The narrow-band low-pass filter 20 and the wide-band low-pass filter 21 extract low-pass components of the output of the phase detector 19. The changeover switch 22 switches the outputs of the two filters 20 and 21. The ripple detector 23 detects a ripple voltage generated when the phase lock loop 25 is out of lock from the output of the broadband low-pass filter 21 and controls the changeover switch 22. The combiner 24 combines the two second intermediate frequency signals and outputs the combined signal.

With such a configuration, since the frequency converters 3 and 4 have independent local oscillators, the output frequencies thereof are different and not the same, but the voltage and the phase are the same at the second intermediate frequency so that the voltages and the phases are the same. This is controlled by the variable local oscillator 15.

To this end, a phase lock loop 25 including a phase detector 19, low-pass filters 20, 21, a voltage-variable local oscillator 15, a mixer 13, and the like is formed, but even when the C / N of the input signal is low, In order to stabilize the operation of the phase lock loop 25, when locked, the filter is switched to the narrowband filter 20, and when unlocked, the filter is switched to the wideband filter 21, so that both the lock range and the capture range are maximized. Are used to set the constants of the narrow-band and wide-band filters 20, 21, respectively.

FIG. 3 is a block diagram of the infinite phase shifter shown in FIG. The infinite phase shifter 5 is of a resolver type for shifting the phase of the intermediate frequency input I, and is mainly composed of a distributor 26, double balance mixers 27 and 28, a hybrid circuit 29, a variable frequency square wave oscillator (variable frequency oscillator) ) 30, a Schmitt trigger circuit 31, a 90-degree phase shift circuit 32, a sine wave fixed frequency oscillator (sine wave oscillator) 33, and sample and hold circuits 34 and 35. Of these, distributor 26
Distributes the intermediate frequency input I to two intermediate frequencies, and the double balance mixers 27 and 28 balance modulate the two outputs divided by the distributor 26, respectively. The hybrid circuit 29 combines the outputs e ₁ and e ₂ of the double balance mixers 27 and 28 with a phase difference of 90 degrees to produce an intermediate frequency output e ₀ .

Further, the variable frequency oscillator 30 changes the frequency by the control input voltage E output from the phase discrimination circuit and outputs a rectangular wave. The Schmitt trigger circuit 31 outputs a sampling pulse according to the rectangular wave output of the variable frequency oscillator 30. The 90-degree phase shift circuit 32 converts this sampling pulse
This is a pulse generator that shifts the phase by 90 degrees. The sample and hold circuits 34 and 35 sample and hold the output of the sine wave oscillator 33 that oscillates at substantially the same frequency as the variable frequency oscillator 30 with the sampling and hold circuits 34 and 35, and use the held voltage to perform double balance mixers 27 and 28. Is performed.

The operation of the infinite phase shifter 5 configured as described above will be described. Output voltage of sinusoidal oscillator 33 with angular frequency Ω is sinΩ
t, the control input voltage is E, and the oscillation angular frequency of the variable frequency oscillator 30 is Ω-kE. Where k is a constant and Ω−kE
Is usually a value close to Ω. If the oscillation angular frequency Ω-kE is multiplied by time t to obtain a phase, which can be Ωt−kEt, the variable frequency oscillator 30 transmits at the same frequency Ω as the sine wave oscillator 33, and the phase is delayed by kEt. Can be considered to be.

Therefore, when sampling the sine wave output with the sampling pulse generated by the Schmitt trigger circuit 31, the phase delay
The output of the sample and hold circuit 35 can be held at a value of sin (kEt) corresponding to kEt. When the sample is delayed by π / 4 with respect to the angular frequency Ω in the 90-degree phase shift circuit 32, the output of the sample and hold circuit 34 is held at cos (kEt).

When the intermediate frequency input signal I is represented by sinωt,
When the signal I is divided into two and multiplied by cos (kEt) by the mixer 27, the output is sinωt · cos (kEt). When multiplied by sin (kEt) by the other mixer 28, sinωt · sin
(KEt). Since the output of the mixer 28 receives a 90-degree phase delay in the hybrid circuit 29, cosωt · sin
(KEt). As a result, the output e ₀ synthesized by the hybrid circuit 29 is expressed by the following equation (1).

e ₀ = sinωt · cos (kEt) + cosωt · sin (kEt) = sin (ωt + kEt) (1) As shown in the above equation (1), for the input sinωt, the output e is sin (ωt + kEt). The phase is advanced by kEt,
An arbitrary phase shift can be performed by changing the control voltage E.

As described above, the in-phase synthesizing devices 100 and 200 of the present invention stabilize the phase of each antenna element output by performing adaptive phase-locked loops 12 and 25, thereby stabilizing the phase. Even if the loop is unlocked, it can be immediately captured by changing the circuit constant. For this reason, the tracking operation of the antenna beam is stabilized, and the tracking range can be expanded.

Further, by expanding the phase lock range, it becomes possible to use independent local oscillators for the frequency converters 3 and 4 for converting the antenna output to the first intermediate frequency. This is because even if the first intermediate frequency has some deviation, the frequency and phase can be made the same in the next phase locked loops 12 and 25.

(Effect of the Invention) As described above, the array antenna in-phase synthesizing apparatus of the present invention converts the output of each antenna element to an intermediate frequency by a frequency converter having an independent local oscillator, and then converts the phase locked loop itself. By performing adaptive control,
Each output is always combined in phase, and the gain, band characteristic or time constant of the phase locked loop is switched or changed, and the pull-in range and the lock range are both held in a wide range, so that an independent local oscillator can be used. The operation is stabilized, and an infinite phase shifter for performing phase lock has a simple circuit configuration employing a resolver circuit, thereby achieving effects such as enabling a high-speed and high-accuracy tracking operation of an antenna beam.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of an array antenna in-phase synthesis apparatus of the present invention, FIG. 2 is a block diagram of another embodiment of an array antenna in-phase synthesis apparatus of the present invention, and FIG. 3 is FIG. It is a block diagram of an infinite phase shifter. 1,2 ... antenna element 3,4 ... frequency converter, 5 ... infinite phase shifter 6,7 ... band filter, 8 ... phase detector 9 ... variable low-pass filter 10 ... out-of-lock detection 11 Synthesizer 12 Phase locked loop 13 and 14 Mixer 15 Variable voltage local oscillator 16 Fixed local oscillator 17, 18 Band filter 19 Phase detector 20 Narrow Band low-pass filter 21 Wide-band low-pass filter 22 Changeover switch 23 Ripple detector 24 Synthesizer 25 Phase lock loop 26 Distributor 27, 28 Mixer 29 Hybrid Circuit 30 Variable frequency oscillator 31 Schmitt trigger circuit 32 90-degree phase shift circuit 33 Fixed frequency oscillator 34,35 Sample-hold circuit 100,200 Array array in-phase synthesizer

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01Q 3/42 H01Q 3/26

Claims (2)

(57) [Claims] 1. A receiving front end having a plurality of local oscillators for converting respective element outputs of a plurality of adaptive array antennas into independent intermediate frequencies, and an intermediate frequency output connected to the receiving front end. A phase lock group for detecting the phase of the output of the other intermediate frequency based on any of the above, switching or varying the gain, band characteristic or time constant between locked and unlocked states and synthesizing them in phase. An array antenna in-phase synthesizer, comprising: 2. A phase locked loop according to claim 1, wherein said phase locked loop comprises a variable frequency oscillator whose frequency is controlled by a phase discrimination output, and a sampling device driven by said variable frequency oscillator and having a phase difference of 90 degrees from each other. A pulse generator for generating a pulse, a fixed frequency oscillator for oscillating a fixed frequency of a sine wave having substantially the same frequency as the variable frequency oscillator, and sampling and holding the output of the fixed frequency oscillator with the sampling pulse to obtain a 90-degree phase difference. Where the phase of the variable frequency oscillator output with respect to the fixed frequency oscillator output is θ as two voltages corresponding to
And a sample and hold circuit that generates a voltage corresponding to cos θ, and is driven by the sin θ and cos θ voltages,
An array antenna in-phase synthesizer comprising an infinite phase shifter comprising a resolver circuit for shifting the phase of an input intermediate frequency by θ.