The present application claims priority from Japanese patent application JP2012-034373 filed on Feb. 20, 2012, the content of which is hereby incorporated by reference into this application.
1. Field of the Invention
The present invention relates to an antenna beam scan module in an antenna device that combines and distributes phases using a Rotman lens.
2. Description of the Related Art
A phased array antenna has been known as a technique of selectively transmitting and receiving electromagnetic waves in a specific direction by scanning a beam. The phased array antenna composed of plural antenna elements can scan a beam by actively changing an electromagnetic phase plane from each antenna element. As a method of realizing the same, a variable phase shifter is provided for each antenna element to be independently controlled so that a desired beam angle is formed. Further, a phased array antenna without variable phase shifters can be realized by connection to each antenna element through a Rotman lens that can combine and distribute electromagnetic waves.
Japanese Patent Application Laid-Open Publication No. 2003-152422 is a related art of the technical field. This document describes “adder circuits are provided to add outputs from two beam ports 20-m and 20-(m+1) of a Rotman lens. A directivity angle between those of beams corresponding to two beam ports can be obtained by addition. Accordingly, the directivity angles of discrete beams can be interpolated” (see Abstract).
Further, Japanese Patent Application Laid-Open Publication No. 2010-074781 describes “a variable amplifier is provided at each of beam ports (transmission ports) BP1 and BP2 of a Rotman lens that forms a transmission beam and each of beam ports (reception ports) BP1 and BP2 of a Rotman lens that forms a reception beam to adjust the gain, so that the directivity of the transmission beam or the reception beam is adjusted. Accordingly, the transmission beam or the reception beam that is directed to an arbitrary direction other than a specified direction corresponding to each beam port can be realized with a simple configuration without using high-frequency switches” (see Abstract).
Further, Japanese Patent Application Laid-Open Publication No. 2006-287501 describes “the invention includes a coupler that extracts a transmission signal supplied to an antenna element through an RF circuit, a DFT (Discrete Fourier Transform) that converts the extracted signal to a signal of a frequency domain, an IDFT (Inverse Discrete Fourier Transform) that converts a signal output from a multiplier into a signal of a time domain, a delay unit that adds a delay temporally combined to the signal extracted through the RF circuit to a signal output from the IDFT, a DFT that converts the signal with the delay added into a signal of a frequency domain, a level/phase detector that detects a magnitude difference and a phase difference by comparing output signals from plural DFTs, a level/phase controller that offsets the magnitude and phase of a transmission signal of each antenna element in accordance with the detected result, and a multiplier” (see Abstract).
In the conventional phased array antenna using a Rotman lens, electromagnetic waves are transmitted and received only by a communication device in a desired direction from narrow-angle antenna beams formed by plural antenna elements, so that the multipath from obstacles can be avoided as shown in Japanese Patent Application Laid-Open Publication No. 2003-152422. Further, in the case where a target communication device exists in the middle between peak angles of the beams generated by the Rotman lens, signals of adjacent input ports of the Rotman lens are processed using accumulators or multipliers, so that the antenna gain in a desired direction can be realized and the angles of the antenna beams can be made narrower. The phased array antenna using a Rotman lens can generate an intermediate beam by combining electric power, and thus the number of beams can be increased without increasing the number of input ports of the Rotman lens. However, generation of the intermediate beam using the accumulators or the like is a technique that can be adapted only to a receiver as shown in Japanese Patent Application Laid-Open Publication No. 2003-152422.
Meanwhile, the phased array antenna is configured using a Rotman lens in Japanese Patent Application Laid-Open Publication No. 2010-074781. The ratio of electric power for two input ports is adjusted by using variable amplifiers, so that beams can be formed at infinite step angles in an intermediate range of the beams obtained from the input ports.
According to Japanese Patent Application Laid-Open Publication No. 2003-152422 and Japanese Patent Application Laid-Open Publication No. 2010-074781, the directivity can be directed to the intermediate direction of the beams corresponding to the input ports by distributing and supplying electric power to adjacent input ports of the Rotman lens even in a transmitter. However, in order to overlap the beam peaks with each other to be directed to the intermediate direction of the beams, it is required for radio waves from the antenna to be in phase at the position in the intermediate direction. Accordingly, in the phased array antenna that generates the intermediate beam by spatial combination of beams irradiated from the Rotman lens antenna of the transmitter using electric power supplied from each input port, it is necessary to control the phases input to the input ports to monitor the state of the radio waves emitted from the antenna.
In order to control the beam using the phased array antenna, it is necessary to control the magnitudes and phases of transmission signals emitted from the antenna elements. However, the relative magnitude ratios and the phase differences of the transmission signals after being amplified by the variable amplifiers cannot be compared by the structure described in Japanese Patent Application Laid-Open Publication No. 2010-074781. Thus, it is uncertain whether or not transmission signals have been correctly transmitted by a beam controller. Manufacturing errors of variable amplifiers and temperature changes are stored as data in a map storage unit, and the beam controller can adjust using the data. However, the map data generated at the time of an inspection of the antenna module is not adapted for aging degradation of the variable amplifiers, and thus the map data needs to be updated. Further, the variable amplifiers in the antenna module have manufacturing errors. Thus, it is necessary for each antenna module to obtain the map data, and costs incurred for an inspection of manufacturing errors and temperature characteristics are disadvantageously increased.
The propagation characteristics as well as the phase characteristics of the variable amplifiers are changed depending on the amplification degree. In the case where adjacent variable amplifiers are controlled using different amplification degrees, the in-phase properties of each transmission signal input to the input ports of the Rotman lens are not maintained. Further, if reflective characteristics are changed due to changes in propagation characteristics of the variable amplifiers because distributors are arranged before the variable amplifiers, the distribution ratio of the distributors and the phase characteristics are changed. In the case where the number of input ports of the Rotman lens antenna is two, a shipping inspection is relatively simple. However, in the case where the number of input ports is three or larger, sufficient isolation is necessary in propagation characteristics between output ports of directional couplers and distributors so as not to have an impact from unused variable amplifiers on the distributors in the magnitude control. Accordingly, a phase offset system for transmission signals is essential in the scanning control of the intermediate beams that are generated by supplying transmission signals to plural input ports of the Rotman lens antenna.
Japanese Patent Application Laid-Open Publication No. 2006-287501 describes a beam control technique in which the magnitude and phase of a transmission signal of an array antenna composed of plural antenna elements are operated to control emittance patterns. The transmission characteristics of RF circuits connected to the antenna elements are affected by manufacturing errors and temporal temperature changes, and the RF circuits are independently fluctuated, thus affecting the beam control technique. As a method of adjusting the transmission characteristics of the RF circuits, transmission signals supplied to the antenna elements are extracted to be compared with those input to the RF circuits, so that the magnitude difference and phase difference are detected. In accordance with the detection result by a detector, the relative level difference and phase difference between signal systems of the antenna elements are obtained, an offset coefficient is calculated to offset the relative level difference and phase difference between signals of the antenna elements in a predetermined range, and transmission signals are offset by a multiplier in accordance with the offset coefficient. As a result, the magnitudes and phases of the transmission signals emitted from the antenna elements are offset by a multiplier of a propagation characteristic offset device, so that the propagation characteristics of the RF circuits are adjusted to be the same. In the configuration of Japanese Patent Application Laid-Open Publication No. 2006-287501 in which the offset coefficient is obtained to maintain the identity of the propagation characteristics between the signal systems of the RF circuits if the magnitudes and phases are controlled by the RF circuits (variable amplifiers) (for the Rotman lens antenna), the identity of the RF circuits is collapsed and consistency of the relative level difference and phase difference between the signal systems of the antenna elements cannot be maintained, resulting in generation of wrong offset signals. Accordingly, the propagation characteristic adjusting device cannot be adapted to generation of non-step intermediate beams for the Rotman lens antenna, and the beam scanning becomes difficult. Further, the magnitude and phase differences are not extracted by directly comparing the transmission signals in Japanese Patent Application Laid-Open Publication No. 2006-287501. In the case where the amplification degrees of the RF circuits are fluctuated on the temporal axis, if a time interval until the offset coefficient of the adjusting device is calculated becomes longer, errors caused by the fluctuations are overlapped with the offset coefficient. The amount of phase rotation of electromagnetic waves with a short wavelength such as millimeter waves is large per unit time, and thus errors caused by the fluctuations on the temporal axis are increased and offset data becomes insufficient in the extraction of the propagation characteristic phase difference of the RF circuits between the signal systems.
In order to address the above-described problems, an object of the present invention is to provide an antenna beam scan module in which signals are maintained to be in phase at beam input ports of a Rotman lens antenna, and thus scanning at non-step antenna beam angles can be realized without increasing the number of input beams.
In order to address the above-described problems, for example, the configurations described in claims are employed.
Although the present application includes plural aspects to address the above-described problems, the following is one example. The present invention provides an antenna beam scan module including: a Rotman lens that has plural beam ports and plural antenna ports and distributes and combines electric power of signals input and output to the antenna ports; plural antenna elements that input and output radio waves to the antenna ports; variable amplifiers that modulate the magnitudes of the signals input to the beam ports; relative phase detectors that detect a relative phase difference between the signals input to the adjacent beam ports; phase shifters that offset the relative phase difference between the signals supplied to the adjacent beam ports on the basis of the relative phase difference detected by the relative phase detectors; and switches that select routes of the signals supplied to the beam ports through the variable amplifiers, wherein the phase shifters are arranged on alternate routes through which the signals are supplied to the plural beam ports.
Further, the following is another example. The present invention provides an antenna beam scan module including: a Rotman lens that has plural beam ports and plural antenna ports and distributes and combines electric power of signals input and output to the antenna ports; plural antenna elements that input and output radio waves to the antenna ports; variable amplifiers that modulate the magnitudes of the signals supplied from the beam ports; relative phase detectors that are arranged before and after the variable amplifiers to detect fluctuations in relative phase difference between the adjacent signals before and after the variable amplifiers; phase shifters that offset the fluctuations in relative phase difference between the adjacent signals caused by the magnitude control on the basis of the fluctuations in relative phase difference detected by the relative phase detectors; and switches that select routes of the signals supplied from the beam ports through the variable amplifiers, wherein the phase shifters are arranged on alternate routes through which the signals are supplied from the plural beam ports.
In the antenna beam scan module configured in such a manner, one beam input port or two adjacent beam input ports that transmit transmission signals are selected by the switches among those of the Rotman lens to control the magnitudes of the transmission signals. The phase shifters that are alternately arranged have a function to offset the relative phase difference between the transmission signals fluctuated by the magnitude control. The transmission signals with the magnitudes controlled and those after passing through the phase shifters are partially extracted using the distributors or couplers to be mixed by mixers. The transmission signals are input signals distributed by the switches. Thus, the frequency components are the same, but only the phases are different from each other.
Especially, when mixing the transmission signals using I/Q mixers, two DC signals corresponding to sin Ø and cos Ø are generated due to the relative phase difference Φ between the transmission signals. The magnitude ratio of these DC signals is arc tangent and the angle of the relative phase difference can be calculated. An average phase difference offset signal on the basis of the magnitude control by the variable amplifiers is preliminarily input to each phase shifter by the beam scan controller. The relative phase difference calculated by the mixer is added to the average phase difference offset signal to be input to each phase shifter for feedback so that the relative phase difference is in phase. Accordingly, the transmission signals of the input beam ports of the Rotman lens antenna can be maintained to be in phase. The average values of the amplification degrees and the phase differences fluctuated by the magnitude control of the variable amplifiers are recorded in the beam scan controller. Even if the amplification degrees are changed due to the manufacturing deviation and temperature changes of the variable amplifiers, the phase offset can be controlled by calculating the relative phase difference with the mixer. Thus, it is not necessary to record the transmission and temperature characteristics of the variable amplifiers as data, and the inspection processes can be simplified.
The present invention can provide an antenna beam scan module in which signals can be maintained to be in phase at beam input ports of a Rotman lens antenna, and scanning at non-step antenna beam angles can be realized without increasing the number of input beams.
Modes for carrying out the present invention will be described in detail on the basis of the drawings. It should be noted that constitutional elements having the same functions are given the same terms and reference numerals in the all drawings for explaining the modes for carrying out the invention, and the explanations thereof will not be repeated.
First Embodiment
In the embodiment, an example of an antenna beam scan module using a Rotman lens will be described.
When electric power is supplied to one of plural beam ports, a beam is output in a predetermined direction corresponding to the beam port using the Rotman lens antenna. Further, when electric power is supplied to two adjacent beam ports, beams are output in directions corresponding to the beam ports, and a beam propagated in the intermediate direction of the beams is formed by spatial combination. If there is a phase difference between two beams, the beams interfere with each other to negate each signal. Thus, the electric power of the combined beam in the intermediate direction corresponds to (1+COS (phase difference)). Accordingly, in order to realize spatial combination in which electric power can be maximized by overlapping two beams with each other, the phases of the two beams need to be in phase.
When electric power is supplied to two adjacent beam ports of the Rotman lens antenna, the beam directions are shifted depending on the electric power ratio of two transmission signals as described in Japanese Patent Application Laid-Open Publication No. 2010-074781. However, as the transmission characteristics of the variable amplifiers 4, passing phases are fluctuated relative to gain control voltage (Vg) as shown in
Using distributors or couplers between the beam ports 24 of the Rotman lens antenna 2 and the variable amplifiers 4, transmission signals are partially extracted to be input to the relative phase detectors 6. The relative phase detectors 6 calculate a phase difference between a transmission signal generated through one of the phase shifters and those generated in adjacent routes. If transmission signals whose components are the same and whose magnitudes and phases are different are input to a phase detector configured using a mixer, for example, an I/Q mixer, two DC signals are generated due to the phase difference. These signals correspond to sin (phase difference) and cos (phase difference).
Y1=A·α1·sin(wt−θ1)
Y2=A·α2·sin(wt−θ2)
If the transmission signals Y1 and Y2 are mixed (multiplied) in the I/Q mixer, the following result can be obtained.
The calculation of the ratio of the DC components results in sin(θ1−θ2)/cos θ(θ1−θ2)=tan(θ1−θ2) and the relative phase difference can be calculated. The relative phase amounts obtained by the relative phase detectors 6 are fed back to the beam scan controller 7 to be added to the phase offset values by accumulators 14, and the phase offset values of the phase shifters 5 are amended. Accordingly, the feedback control is performed so that the phases of the adjacent transmission signals are in phase.
The phase difference between the adjacent transmission signals is offset by feedback control at the relative phase detectors 6 in the embodiment. Thus, the phase control can be realized only by preparing the variable amplifier gain (Vg)-passing phase (Phase) conversion table, and an inspection of temperature characteristics relative to in-phase signals can be simplified.
If switches are used in distribution of electric power to be sorted into the beam ports of the Rotman lens antenna, it is possible to realize output ports that are high in reflectivity coefficient relative to line characteristic impedance when the switches are not connected, and transmission signals can be propagated to desired terminals without attenuation of the transmission signals in reverse proportion to the number of distributions.
The input impedance of each variable amplifier 4 is fluctuated due to magnitude control. If transmission signals input from the high-frequency signal terminal 9 are distributed using the distributors determined in accordance with the impedance ratios, the impedance ratios are changed due to matching fluctuation caused by the magnitude control of the variable amplifiers. Thus, it becomes difficult to control the magnitudes and phases of the transmission signals. Accordingly, using the switches 3 for distribution of electric power of the transmission signals, the number of variable amplifiers 4 that are functionally connected to the high-frequency signal terminal 9 is limited to up to 2 to suppress the fluctuation of the impedance, so that the phases can be sufficiently offset by the relative phase detectors 6.
Second Embodiment
In the embodiment, an example of an antenna beam scan module that performs not only the relative phase difference offset, but also the magnitude offset will be described.
A circuit configuration of the relative magnitude and phase detector 60 is shown in
In the configuration of the second embodiment, the results of the calculation by the relative magnitude and phase detectors 60 are fed back to the beam scan control unit 10 of the beam scan controller 7 as two pieces of error information of phase information and magnitude information. Using the two pieces of error information, the control amounts of the variable amplifiers 4 and the phase shifters 5 can be calculated again. Using the error signal of the phase information, the phase offset value of each phase shifter 5 is amended through the phase control 12. In addition, using the error signal of the magnitude information, the gain of each variable amplifier 4 is amended through the PA gain control 11. Accordingly, the two error signals are obtained by the configuration of the second embodiment to control the magnitude and phase, so that more-accurate beam angle scanning by the transmission beams generated from two beam ports can be realized.
Third Embodiment
In the embodiment, an example of an antenna beam scan module that performs the phase offset of beam ports of a Rotman lens antenna will be described.
Fourth Embodiment
In the embodiment, an example of an antenna beam scan module in which a variable attenuator is used for a constitutional element connected to beam ports of a Rotman lens antenna.
Fifth Embodiment
In the embodiment, a second example of an antenna beam scan module in which variable amplifiers are used for beam ports of a Rotman lens antenna will be described.
Sixth Embodiment
In the embodiment, an example of an antenna beam scan module for receiver using a Rotman lens will be described.
In the antenna beam scan module for receiver 1, the phase information Ø1 and Ø2 of reception signals output to the beam ports 24 of the Rotman lens antenna 2 are not always the same. Thus, fluctuations {(Ø1-Ø2)-(Ø1′-Ø2′)} of the relative phase differences are observed before and after the routes passing through the variable amplifiers 4 and the phase shifters 5, or the transmission paths 8, and are fed back to the phase shifters 5 so that the phase differences Ø1-Ø2 and Ø1′-Ø2′ before and after the routes become the same. In the phase difference offset between the beam ports of the Rotman lens antenna 2, the phase difference is reflected on an error signal in a phase table 15 of the beam scan controller 7 to generate an offset signal. According to the embodiment, fluctuations in the relative phase difference between adjacent signals caused by the magnitude control of the variable amplifiers can be offset. Accordingly, it is possible to realize an antenna beam scan module for receiver enabling scanning at non-step antenna beam angles by using the configuration of the embodiment shown in
Seventh Embodiment
In the embodiment, an example of a communication apparatus using an antenna beam scan module will be described. The embodiment of the communication apparatus using the antenna beam scan module is shown in
Number | Date | Country | Kind |
---|---|---|---|
2012-034373 | Feb 2012 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
4042931 | Gustafsson | Aug 1977 | A |
20100073260 | Fujita | Mar 2010 | A1 |
20120257653 | Nagaishi | Oct 2012 | A1 |
Number | Date | Country |
---|---|---|
2003-152422 | May 2003 | JP |
2006-287501 | Oct 2006 | JP |
2010-074781 | Apr 2010 | JP |
Entry |
---|
English Translation of JP 2003-152422 A. |
English Translation of JP 2006-287501 A. |
English Translation of JP2010-074781 A. |
Number | Date | Country | |
---|---|---|---|
20130214974 A1 | Aug 2013 | US |