DE3102110A1 - PHASE CONTROLLED GROUP ANTENNA - Google Patents

Description

Licentia FnLont-Verwaltungs-GmbH NE2-UL / We / sa Theodor-Stern-Kai 1. UL O0 / 9O

D-6OOO Frankfurt 70

Phased array antenna

. The present invention relates · to a phased array antenna of the kind specified in the preamble of claim 1. Such antennas are used in particular as a radar antennas for air surveillance pre-O ¹⁾ partially incorrect application.

It is known that the direction of the antenna lobe of array antennas by changing the phase of the antenna elements can be changed without inertia. In the case of a planar or linear array, the values of the phases of the currents in the individual antenna elements according to the following well-known formula:

^X n

- 5 - WL 80/90

In this formula, φ is the size of the phase to be set for the η-th radiator element, sin V is the sine of the angle of the radiation direction Y ¹ against the normal on the antenna surface, χ is the coordinate of the antenna element in the direction parallel to the planes through the normal and away
wavelength

male and radiation direction is formed and λ is the

For radar antennas for airspace surveillance, e.s is dariibor In addition, it is common to use the phase control not only to swivel the beam, but also to widen the antenna lobe (beam spoiling). A second value φ is added to the control phase φ, which causes that the wave field excited by the antenna elements no longer has a flat phase front, but a curved phase front. Has been particularly suitable z. B. a course of this lobe broadening phase φ proportional.dem cosine of the distance from the antenna center proven.

B ^x n

<Ρ _Ώ ^ ^{cos π} - (2).

D is the diameter of the group antenna in the x-direction and χ is measured from the center of the antenna surface. The implementation of these widened antenna lobes often leads to unsatisfactory results in practice. because the diagrams broadened by the curvature of the phase front are sensitive to incorrect deviations the amplitude of the antenna elements. The curvature of the phase front causes that of the Antenna area radiated power no longer preferred is only emitted in a roughness direction, but

- 6 - UL 80/90

that each antenna element preferably in the direction of the perpendicular to the phase front at the respective location of the element radiates, so that the course of the amplitude of the main lobe of the antenna diagram is approximated - a subscription picture of the amplitude course over the antenna surface. so Line systems for feeding the antenna elements often have tolerance-related or even systematic errors on, especially the serial feeds preferred because of their compactness, especially for broadband use. This has. As a result, the antenna lobes achieved are deformed, which in turn increases in radar applications incorrect direction determinations leads.

A restriction of the tolerances would lead to a considerable. borrowed effort in the development and production of such ^ cj feeds lead. A subsequent correction of the amplitude values could only be bought through additional performance losses and is difficult to implement.

The object of the present invention is to provide a phased array antenna that can be used without major to-OQ additional effort reduces the disruptive effects of the tolerance-related Amplitude errors on the diagram eliminated without having to accept additional performance losses.

The solution according to the invention is achieved with an antenna of the type described in the preamble of claim 1 the characterizing features of claim 1 given.

Claim 2 describes a particularly advantageous embodiment of the inventive concept. The claims 3 and 4 give favorable developments of the invention.

BATH ORIGINAL

- 7 - UL 80/90

What is essential to the invention is therefore the compensation of the effect of the incorrect amplitudes by means of

. position of the control phases according to the measured amplitude distribution. Since the phase-controlled group antenna has the necessary phase shifters anyway, only one additional function of the computer (Beam Stearing Unit) used to control the phase shifters is necessary for the antenna according to the invention.

The following is a particularly advantageous embodiment of the inventive concept with reference to the figures described in detail.

The basis of the following derivation of a relationship between the measured amplitude curve and the setting values for the phase setting is the application of geometrical optics to the synthesis of antenna diagrams by designing the phase curve ₍ as is common, for example, for calculating reflector antennas and eg . in S. Silver: Microwave Antenna Theory and Design, Mc, Graw Hill 19 * 19, pp. Ί · 97 ff. is described.

The aim of this synthesis is, for a given distribution of the RF power over the antenna cross-section P (x) to find the phase course that causes this power according to a desired distribution function Pp (i) is emitted in the far field, i.e. i.e. that in the considered sectional planes an antenna diagram with the desired course depending on the direction angle "V * is achieved »V / e.gen the reciprocity, in principle, all explanations also apply analogously to the receiving antenna.

BATH ORIGINAL

- 8 - UL 80/90

Since, as already explained, with this method of diagram synthesis Each zone of the antenna mainly radiates in a certain direction in space, can be derived from the law of conservation of energy The following assignment of the cross-section coordinates χ to the angle "V ^" can be found

Ψ (χ)

Ϊ - "υ

J ~ 2

AU7 ^α Έ "IF (β) d θ

(3)

Let D be the diameter of the antenna and y · the direction at

which should start the desired radiation. The distribution of the power over the antenna cross-section can be determined by measuring on the mounted group antenna. Either you measure it at the inputs of the pathogen - in In this case, the integral is to be replaced by the sum of the output of the pathogen - or directly in front of the pathogen on a near-field measuring station.

I ¹ J If · it is not a linear antenna group ·, but a two-dimensional array, the average power of a row of elements is to be taken across the planes of the considered radiation direction.

The desired power distribution in the far field depends on the application. A sector diagram is often required :

^P 0 for -φ <θ £ -r ^v ο ο

0 for I θ j ■? r (k).

BATH ORIGINAL

- 9 - UL 80/90

Dies.es ideal wish diagram leads, however, because of the Diffraction effects for realizations with an oscillating diagram. It is therefore advisable to choose one of these similar ones instead of the ideal sector function (4) has no sharp cracks. If the antenna use does not require any other power distribution in the far field, is to choose a different V / Un diagram accordingly (for example Cosecans in the square).

If both functions P. and P are given, a radiation direction l "(x) can be assigned to each coordinate value χ on the antenna aperture by numerical integration of (3). The sought phases φ = φ (χ) result from the fact that the direction of emission is perpendicular to the phase front, ie when counting the angle T from the normal to the x-direction, the derivative of the phase according to the coordinates χ is equal to the tangent of the angle ν

The numerical integration of (5)

.. p

,? _2π 9.

φ = φ (χ) = const, '\ γ- tgV (x) dx ' ^{Π η} °

(6)

° 2

directly supplies the setting value for the control phase of the element at the place χ.

These phase values are stored as constants in the computer used to control the phase shifter.

- 10 - UL 80/90

As long as the radar system is operated in several frequencies and the radiation amplitudes of the elements are above change the frequency significantly, -are the phase values for to determine and save each frequency separately.

PIG. 1 shows an example of a linear group of dipoles (1-6) with the coordinates χ -x, -, which are excited by a transmitter T via a feed line S. The 'phases Cp ₁ -Cp / - can be controlled by electronic phase shifters

can be set. In front of the dipoles there is a use, 10 division of the HF power P. (x), the z. B. with a test receiver R can be measured.

FIG. 2A shows the optical beam path and curves of the same phase in front of the group antenna according to FIG. 1. Through the ■ phase one lo llung goes from the antenna aperture. A has a curved wavefront. The radiated power runs parallel to the optical rays S, which are perpendicular to the curves of the same phase P, in the spatial direction f \ The angular position of the rays Y (x) must be such that the power density per angular unit corresponds to the required course P_ (y ) is equivalent to. An example of one

such a desired power distribution in the far field, a ¹ Sc sector diagram, is shown in FIG. 2B.

The FIG. 3A shows (in Cartesian representation) one Cross section through a diagram of a serially fed

2 ^ group antenna without the inventive correction of the Amplitude error due to the setting of the control phases. The asymmetrical diagram distortions are clearly recognizable, which can lead to considerable angle measurement errors when operating the antenna. FIG. 3B shows in contrast the diagram corrected using the inventive concept on the same antenna.

BATH ORIGINAL

Claims (3)

Licentxa Patent-Verwaltungs-GmbH j> iE2- ^r ' ^r , I Theodor-Stern-Kai' 1 UL Bo ^ O " D-6000 Frankfurt 70 Claims V 1 .J Phase-controlled group antenna with a '■.: Aii 1 individual radiator elements or rows of Sti λ ο el. ·, · Th each with a controllable phase shifter, the i: l ·; "·?. *.:. Distribution network with a common feed line, the target assignment of the relative amplification of the individual radiator elements is determined by the location of the individual radiator element within the radiator group and by the desired antenna diagram, characterized in that in a read-only memory for the individual setting of the Controllable phase shifter setting values are stored, which are dimensioned according to the deviation of the measured course of the actual relative amplitudes of the individual radiator elements from the target occupancy so that the setting of the phase shifter by a control device to these setting values causes a compensation of the diagram distortions caused by the amplitude deviations . BATH ORIGINAL - 2 - UL 80/90 2. Phase-controlled group antenna according to claim 1, characterized in that the setting value φ for Control of the phases of the η-th radiator element with the measured amplitude occupancy P (x) in the antenna aperture depending on the coordinates χ running parallel to the diagram section under consideration and the Qa Desired diagram form Pp (I /) as a function of the angle the direction of emission i? i via the relationship B C _ο π η. % ⁼ ^ const. ⁺ \ I- tan ^ fx) dx. defined with / '(x) so that Ρρ (θ) d θ is linked, where χ is the coordinate of the η-th antenna- ^ n ^- elements, D is the diameter of the antenna aperture and -tf ^{1 is} the angle at which the radiation is to begin and the phase shift φ is arbitrary, but the same for all radiator elements. 3. Phase-controlled group antenna according to claim 1 or 2, characterized in that the controllable phase shifter at the same time are still connected to the control device for electronic pivoting of the diagram. - 3 - UL 80/90 k »Phas'engesteuerte array antenna according to one of claims 1 to 3" characterized in that for the operating mode with a plurality of transmission frequencies to each Sendefre.quenz a separate set setting values is stored.