Process For The Automatic Tracking Of The Directional Beam Of A Phased Array Antenna

Abstract

A device for automatic tracking of the directional beam of a phased array antenna which includes a plurality of modules arranged in rows and columns. A part of the output voltages of the modules are coupled together to develop signals which are indicative of either the even numbered or odd numbered rows and columns of modules. The output signals are coupled to phase discriminators which develop positive or negative voltages in dependence on the sign of the angle of incidence of the arriving signal. The control voltage is then used in a closed regulating circuit to control delay lines associated with each of the modules.

Description

The field of art to which this invention pertains is tracking antennas and in particular to devices for the automatic tracking of the directional beam of a phased array antenna.

It is an important feature of the present invention to provide an improved device for the tracking of the directional beam of a phased array antenna.

It is a principal object of the present invention to provide an array of modules arranged in rows and columns for the purpose of tracking a directional beam.

It is another object of the present invention to provide an array of modules as described above having signal outputs representative of even numbered and odd numbered rows and columns and having such outputs coupled to phase discriminators to develop control voltages in response to the phase difference between the odd numbered and even numbered rows or columns.

It is an additional object of the present invention to provide an array as described above wherein the output of the phase discriminators develop control voltages which are used to control delay lines associated with each of the respective modules.

The single sheet of drawings of the present application shows an array of modules arranged in rows and columns according to the present invention. The modules have been divided into an upper array and a lower array which in actual practice constitute a single set of modules.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention relates to a device for automatically tracking the directional beam of a phased array antenna which includes a plurality of modules arranged in a plane in rows and columns. The signal outputs are coupled together in the circuit of a receiving antenna.

Directional antennas with accessory devices for automatically tracking a directional beam of a moving radiation source are known. Many of the known devices are also useable with phased array antennas in which case a computer functions as an extensive intermediate member operating usually on a digital basis. The computer delivers the necessary commands for the signal delays which differ in each case for the individual elements. In many uses, for example, in radio communication between satelites and airplanes or ships or in the case of on-board apparatus for radar techniques, however, both the expense and the weight would become too great. Because of the expense and other technological reasons, mechanically rotatable tracking antennas are not useable. Therefore, there exists the need to develop a simple phased array antenna having an automatic directional beam tracking system that can be operated without the use of computers.

According to the invention this is achieved in a simple manner. A part of the output voltages of the modules, decoupled from the useful signal supplied to the receiver, are coupled together in such a way that the signals are indicative of either the even numbered modules or the odd numbered modules in the respective rows and columns. Thus there are two outputs for the rows and two outputs for the columns. These outputs are supplied to the inputs of two phase discriminators.

From each of the phase discriminators there is delivered a positive or negative direct voltage in dependence on the sign of the angle of incidence of the arriving signal. The direct voltage is used as a control voltage for the delay lines of the associated modules so that a closed regulating circuit results which is in equilibrium when the output signals of all the individual modules are in phase. Depending on the spatial position of a received wave front the output signals are added vectorially. Through the displacement of the groups in each case by the module spacing in the direction of the columns as well as also in the direction of the rows, however, the phase of the sum signal supplied in each case to a phase discriminator is dependent on the angles of inclination in the direction of the rows and the direction of the columns between the array plane and the wave front plane. A prerequisite for the faultless functioning of the phased array antenna is, in this connection, the reciprocal decoupling of all the emitter elements.

Referring to the drawing, there is used a surface antenna with 6 .times. 6 elements in which the columns and rows are arranged perpendicular to one another in X and Y directions. Each module of the phased array antenna has a delay line L in the radio frequency or intermediate frequency plane. In the latter case, the intermediate frequency is formed by conversion with a common converter generator within each in-phase feed. The transit time of the delay members L is varied with a direct voltage substantially proportionally to this.

The modules, in the interest of clarity, are represented twice, namely in an upper and in a lower array configuration. The upper array receives symbollically the controllable delay lines L, and the lower the other module components M with, in each case, two signal outputs. These two signal outputs are coupled together at an output A at which the antenna signal for the receiver is taken.

In the actual installation the constituents which are represented above and below in the drawing are components of one and the same module. In the lower part of the drawing, the outputs which are coupled together in the X direction are designated with X. The outputs coupled together in the Y direction are designated Y. In both directions the corresponding outputs of the even numbered rows and columns (X.sub.n2 , X.sub.n4 , X.sub.n6 , and Y.sub.n2 , Y.sub.n4, Y.sub.n6 respectively) and odd numbered rows and columns (X.sub.n1 , X.sub.n3 , X.sub.n5 , and Y.sub.n1 , Y.sub.n3 , Y.sub.n5 respectively) are grouped together. The signals of the two X groups are supplied to a phase discriminator P1 of the X direction and those of the two Y groups to a similar discriminator P2 of the Y direction. The inputs to the phase discriminators P1 and P2 are decoupled by the decoupling resistors E from the output A. The direct voltages delivered from the discriminators P1 and P2 are amplified in two amplifiers V1 for the X direction and V2 for the Y direction and coupled to two switches S on the control inputs of the delay lines L.

The control voltages delivered from the amplifiers V1 and V2 are divided in a voltage divider consisting of like resistors R. For both directions in each case a tap couples a row of control inputs. The voltage delivered in each case for the X direction and Y direction to a module is added and supplied in common to the respective delay lines L as control voltages.

Through the use of the voltage divider and the fact that the relationship between control voltage and group transit time of the delay lines L, equal among themselves, is very nearly linear, it is achieved that there is obtained a radiation diagram with approximately optimal concentration independently of the two control voltages. The magnitude of the X and Y control voltage determines only the direction of the beam bundle in respect to the array plane.

A signal incident perpendicularly upon the array plane delivers a signal voltage in the same phase on all the module outputs. The two phase discriminators P1 and P2 deliver no voltages, and the regulating circuit is in equilibrium. Now if the wave front changes its direction, then the voltages of the modules in each case no longer add linearly, but vectorially. Between the sum voltages of the two lines conducted to a discriminator P1 or P2 there exists then through the group displacement, depending on the angular deviation of the wave front in the X and Y directions, a phase difference which brings about a corresponding control voltage on the phase discriminator outputs. With correct connection of the amplifiers V1 and V2 there is yielded a variation of the transit time in the delay lines L in such a way that again the voltages of all the outputs are added very nearly linearly. The directional beam is thus tracked. The loop amplification of the regulating circuit is chosen, for the achievement of a stable behavior, of such a magnitude that for maximum deflection of the directional beam, for example 60.degree. in X and Y directions, output voltages of the phase discriminators P1 and P2 are developed by phase differences of a few degrees, for example 3.degree..

If at first no signal comes in, the switches S connect the two control lines with a generator SG. The generator SG delivers alternating voltages of differing frequencies. If in the course of a searching phase a signal of sufficient intensity appears on the output, the switches S are thrown with sufficient rapidity by a switching arrangement B so as to initiate the tracking process.

With decreasing band width of the feed channels to the discriminators, the sensitivity of the tracking to noise and similar interferences becomes less. The band width of the feed channels is expediently adapted to the spectral quality of the received signal.

Phased array antennas can be used for transmitting as well as receiving. The modules then each have a transmitting and a receiving branch, which, in the case of equal transmitting and receiving frequency are connected in alternation or in the case of differing transmitting and receiving frequencies, are connected over frequency branching networks to the radiator element. In this context, various types of switching of the controllable delay lines are possible.

Separate transmitting and receiving antennas can be used each with a set of delay lines either in the RF or the ZF plane. There the control voltages for the delay lines of the receiver array antenna are likewise fed to the corresponding delay lines of the transmitter array antenna. With like transmitting and receiving frequency and alternating operation of transmitter and receiver, however, the control voltage valve yielded in the receiption has to be stored for the purpose of latter transmitting in the receiving direction. If a common phased array antenna is used for the receiving and transmitting, then, for example, in the ZF parts of the transmitter, there can be accommodated a set of delay lines or also a common set of delay lines in the microwave plane.

There are also arrangements with a converter system which contains a common intermediate frequency part for both transmitting and receiving and which also contains a common delay line. In all these cases it is possible according to this invention, with use of like transmitting and receiving frequencies, to transmit with corresponding tracked directional antennas, if the tracking control voltages of the various directions present are stored until transmission and are placed during transmission on the voltage divider. In the executed example, the storage take place in a storer C, from which the stored control voltages for the specific direction are colled off according to a transmitting command given from a control input D over the switch S.

Claims

1. Apparatus for automatically tracking the directional beam of a phased array antenna comprising: a plurality of receiving modules, said modules being arranged in rows and columns, a delay line associated with each module, phase discriminator means for developing a control voltage in response to the phase of a received signal, means for using said control voltage to vary the delay of the delay lines associated with each module, the outputs of each of said modules in respective rows and columns being coupled together, the outputs of odd numbered rows and columns being coupled to respective inputs of the phase discriminator means, outputs of even numbered rows and columns being coupled to other respective inputs of said phase discriminator means whereby two inputs are provided for the columns of the array, said phase discriminator means including first and second phase discriminators for developing positive and negative direct voltage outputs in dependence on the sign of the angle of incidence of the received signal, first and second voltage dividers, said phase discriminators having outputs which are coupled to said first and second respective voltage dividers, said first voltage divider having a series of taps each of which is connected to a respective common input of the delay line of a given row, said second voltage divider having a series of taps each of which is connected to a respective common input of the delay lines

2. Apparatus for automatically tracking the directional beam of a phased array antenna in accordance with claim 1 wherein the respective delay

3. Apparatus for automatically tracking the directional beam of a phased array antenna in accordance with claim 1 wherein during the transit from reception to transmission storage means are provided to store the control voltage for the delay line for use during a subsequent transmitting

4. Apparatus for automatically tracking the directional beam of a phased array antenna in accordance with claim 1 wherein an AC voltage generator is employed and switching means are provided to couple said voltage generator to the delay lines in the absence of a receiving signal, and wherein means are provided to switch out the voltage generator and switch in the regulating means when a signal exceeding a threshold level is

5. Apparatus for automatically tracking the directional beam of a phased array antenna in accordance with claim 1 wherein the rows and columns are

6. Apparatus for automatically tracking the directional beam of a phased array antenna in accordance with claim 5 wherein the spacing between the modules is in the order of one-half wavelength of the signal to be received.