DE1616258C - Missile Doppler radar device with a mixture of the echo signals received obliquely downwards from the front and from the rear - Google Patents

Description

1 2

The present invention relates to a ground - ie essentially perpendicular to the Doppler radar device for missiles, consisting of the direction of the radar beam - to determine, and to generate a pulsed microwave carrier which, by using non-coherent signals, the transmitter, one with the carrier of the transmitter fed to a stable local oscillator transmitting antenna, which can draw a beam obliquely 5, the Doppler shift is derived from ■ downwards forwards and another downwards diagonally that a beat signal through the Fre- ■■ -. ; radiates backwards, a receiving antenna frequency difference between the forward and reverse; Order is generated for the downward beam obtained from the two beams. The forward beam has echo signals and a receiver that has a higher Doppler frequency of the echo signals received by the receiving antenna compared to the emitted beam, while the beam emitted backwards by mixing a demodulated signal downwards compared to the outgoing beam - j is generated, the frequency of which corresponds to the Doppler shift sent signal, a decreased Doppler shift j of the echo signals. having. ■ -. \

It is already known in radar devices (for example, due to the training according to the invention "■;

from German interpretation 1180 061; The time of the radar device is thus the output signal frequency j

font "L'Onde Electrique", No. 462, September greater than the reference frequency if the vehicle j

1965, p. 1055, as well as the magazine "Electronics" from moving in one direction, and smaller than that

June 1, 1957, pp. 150 to 152), not only the size ^ reference frequency, if the direction of movement

a speed, but also the sign is opposite. Through a suitable antenna- j

to determine this speed. With pulsating construction and suitable signal handling;

In the coherent radar systems, this takes place in this way and can therefore also be used in a radar device;

that the Doppler shift signal of the type mentioned above has the sign of the speed

Pulse signal can be separated and derived with one of a stable duration. The details of the approach;

Local oscillator derived signal is superimposed. antenna construction are not critical as long as;

Usually, the 25 long in this case separate signals from the stable local oscillator of each radiation \

derived signal additionally offset in frequency, pair are derived, whereby the two signals \

wherein the signal used for this purpose is designed to have a frequency to one another in such a way as if they were from j

has, do is greater than the largest expected two receiving systems would have been derived, j

Doppler shift. The Doppler shift is that along a line over an equivalent Ab- j

then determined in relation to this displacement _{signal: 30 stood yon} * _{ge are slightly displaced} . _Each

The 4 & &, which are above the offset frequency

Frequencies then namely correspond to a positive one of these signals is then measured to one of them Doppler shift - d. H. movement in the pair of quadrature chip-forward directions - to generate "" while below the voices, with the information of the Settlement frequency frequencies with a negative 35 speed sign from the direction of rotation tive Doppler shift - d. H. movement of the two phase signals is included. The two in the reverse direction - correspond. Signals can then be shifted in terms of frequency

According to the invention, the sign will be determined and with the aid of a sine-cosine frequency achieved in another way, namely by treating the tracking circuit in a conventional manner Receiving antenna arrangement is designed so that 40 are to both the speed sign they derive the two echo signals twice to one another as well as the speed variable, added, the second time in such a way that the following is intended to illustrate the invention with reference to second signal compared to the first signal one explained and described in more detail by exemplary embodiments

π . " ,,., Cj. it. With reference to the drawing

_ ■ has a different phase shift than the · * r- · *

2 ^ö 45 men. It shows

first time, so that the Doppler modulations of Fig. 1 is a schematic block diagram of a

a mutual phase shift corresponding to the state of the art Janus system,

... η _e . 1 η j r- «··. · F i g. 2 a perspective schematic representation

sehension von .. show that the recipient has two, ^b ■ .. ^ 1. r 1 λ ► ι

^& 4 '. a linear double strand antenna arrangement

Has detectors, which by demodulating the 50 voltage,

Generate sum signals double oscillations that F i g. 3 is a schematic block diagram of a

are in phase equation to one another, and that in the context of the present invention,

in a manner known per se for the two Doppler receivers,

oscillations each one from a local oscillator: i- Fig. 4 is a schematic representation of a pre-

,. ,. , π ,,, ■. 55 participated, within the scope of the present invention

gate directly or _ phase shifted ha. ι

2 '. usable antenna arrangement,

Frequency converter and a Fi g connected to this. 5 is a schematic block diagram of a

Sublraktionsstiife for obtaining a starting material used in the context of the present invention

signals are provided, the frequency of which depends on the frequency proximity circuit and the baren

Sign of the phase difference between the 60 F i g. 6 a schematic representation of another

Doppler variations and thus the sign rc η used in the context of the present invention.

the aircraft speed by one of these areas modified antenna arrangement.

speed proportional amount greater or I'ig-1 is shown in a schematic block diagram

is less than a nc / ugsf'rcquciiz. of a typical non-coliidal Janus system

In the case of such a radar system, Jaiuis type, 65 of known type. For the sake of simplicity, only

which is represented by sending a radar beam each into a single channel. According to Fig. 1 radiates

the forward and backward directions in which one antenna arrangement 10 emits a microwave beam

Able is a speed in relation to the H in relation to the direction of flight forward and

a similar beam 12 backwards. It is assumed that the antenna assembly 10 consists of a rectangular linear waveguide, it being understood, however, that other antenna shapes can also be used. . r If a waveguide is provided with a number of radiators, which are arranged at regular intervals along the longitudinal axis on one of the outer surfaces of the waveguide and if this waveguide is connected at one of its ends to a microwave generator, then it radiates the energy in the direction away from the feed end, with half the opening angle γ of this beam compared to the longitudinal. axis is given by the following equation:

In-phase and antiphase antenna arrangements can be combined so that the same one result in a single antenna arrangement that emits two beams, one beam having in-phase properties and the other has antiphase properties. When this is done, it occurs within each group a mutual cancellation of the signals of those radiators which phase positions of

± 2 '"F τ ^{c" au} f ^we i ^sen · Accordingly, such a two-beam antenna array, for example, consist of a series of shunt slot radiators, whose mutual distance is equal to 2 S and shift their phase positions as follows:

^{cozy =}

Νλ

(1)

0, π, 0, π etc.

(6)

where λ is the wavelength in free space, X _{g is} the wavelength within the waveguide, S is the distance between the individual radiators and N is an integer, including zero, which corresponds to the ordinal number of the main lobe generated. Such antenna arrangements are referred to as "in-phase arrangements". Given suitable values of γ, λ and l _g , a distance S can be used at which no second main lobe is generated, with this distance 5 having a phase difference of

π
2

(2)

occurs between individual radiators. Thus, the phase positions on the individual radiators are different from that End of meal as follows:

0, - , π, - -, 0 etc.
2 2

(3)

In the following, an antenna arrangement is to be considered in which the phase position of each successive radiator is shifted by 180 °. To achieve this, the emitters are in the form of slots arranged within the broad side of a rectangular waveguide are, these slots are offset on one side with respect to the longitudinal axis of the waveguide. Through Moving every second slot to the other side of the longitudinal axis changes the phase position by 180 ". As a result, with such an antenna arrangement, the phase positions are more consecutive Emitter as follows:

0 ,, η, - ', 0 etc.
2 2

(4)

The radiation generated by this is given by the following equation:

COS J '

λ _ λ λ, IS

(5)

where; ■ now half the opening angle of a ray represents in the direction of the feeding end of the arrangement. An antenna arrangement determined by equation (5) is generally called an "anti-phase arrangement" designated.

It appears plausible that the above-mentioned in FIG. 1 indicated antenna arrangement 10 is more precisely in FIG. 2 shown. As can be seen in this figure, the arrow 31 represents the normal component of the beam 11, which corresponds to the in-phase beam emitted by the waveguide 33, as soon as the waveguide 33 is at its left end by a suitable microwave generator is fed, as indicated by arrow 40. In the same way, the arrow 32 represents the normal component of the beam 12, which corresponds to the anti-phase beam, which is simultaneously from the Waveguide 33 is emitted. As has already been mentioned, the individual Strähler des Waveguide 33 formed by shunt slots within the broad side of the waveguide. It should, however it should be understood that similar results can also be obtained using other known forms of spotlights - such as B. Dipoles, horns, corner slots or the like. - Are used.

It should now again be on FIG. 1, a pulse generator 14 is shown which feeds an amplitude modulator 16 via a driver 15. Depending on the amplitude modulator 16, a magnetron 17 outputs a microwave carrier frequency signal of, for example from 8.8 GHz, which is pulsed according to the frequency of the pulse generator 14. The frequency of the pulse generator 14 is, for example, of the order of 50 kHz. The microwave pulse signal of the magnetron 17 is transmitted to the antenna arrangement 10 via a transceiver switch 18 directed. . · '

The signal reflected back from the earth will. received in the antenna arrangement 10 and fed to a mixer 19 via the transceiver switch 18. As is known, the Doppler effect results in a frequency interleaving, so that the signal deflected by the forward beam 11 has a frequency of 8.8 GHz! 17, while the echo signal of the rear beam 12 has a frequency of 8.8 CiHz I 1 · ,,. having. By means of a local oscillator 20 "oscillating at 8.77 CiHz, output signals of 30 MHz 4 Vf or 30 MHz I-)""are generated by the mixer 19. These signals are then fed to an intermediate frequency amplifier 22 via a gate 21 controlled by the driver 15 The output of the intermediate frequency amplifier 22 is connected to a coherent detector 23 in which the forward and reverse signals cause oscillation, and the envelope of this swelling is then extracted using this signal

has a center frequency of v _t -v _a , which thus contains the Doppler information. After further amplification in a Doppler frequency amplifier 24, this signal is thus fed to a frequency follower 25 which generates a continuous output signal which is proportional to the magnitude of the speed above the ground. The output signal of the frequency follower 25 can thus be fed to a suitable speed display device 26. Due to the fact that the Doppler information is formed by superimposing two echo signals from a forward and backward beam, the result is that the spectral frequency distribution of the input signal corresponding to a certain speed of the frequency follower 25 is independent of whether the speed vector is opposite to the ground in the forward or backward direction. For this reason, "the previously known non-coherent Janus ao doppler devices are not able to provide information about the sign of the speed of travel.

In the context of the present invention, a modification of the known one shown in FIGS. 1 and 2 is thus made Janus systems illustrated are proposed, reference being made to FIGS. 3 to 6.

In Fig. 3 are omitted to simplify the illustration of the transmitter part and the intermediate frequency stages, because these parts remain unchanged and thus outside the scope of the present Invention lie. .-'...>

According to FIG. 3, the antenna assembly denoted by reference numeral 10 is made by a pair replaced by identical, linear, rectangular waveguides, which, for example, according to FIG. 4 side by side can be arranged.

With the help of suitable, not shown microwave switching elements or circuits it is achieved that the waveguide 37 shown in Fig. 1 and 12 emits while both waveguides 37 and 38 are able to correspond to the two beams 11 and 12 receive a reflected echo signal.

The two waveguides 37, 38 are offset from one another at a distance δ along their longitudinal axes, so that during reception the phase of the standing wave in one waveguide 38 compared to the phase of the standing waves in the other waveguide 37 -

is offset. The in F i g. 1 shown antenna arrangement 10 has thus been doubled, the the two waveguides 37, 38 are offset from one another. For this reason, the antenna arrangement produces According to FIG. 4, two voltages that are exactly the same are, but have a phase shift of 90 ° to each other.

The voltage terms at the output of the waveguide 37 can be expressed mathematically as follows will:

e _x = A sin [(ω + v,) t + Φ] + ßsin [(ω + .v _a ) t +

where Vf denotes the Doppler frequency shift with respect to the echo signal of beam 11 and v _a denotes the frequency shift of the echo signal in connection with beam 12. Equation (8) represents the sum of the forward and backward echo signals within the waveguide 37. Based on the trigonometric equation

sin (α + β) = sinacos /? + cosasin / ϊ (9)
can e _{t be represented} as follows:

e _x = [A sin (ωί) cos (v, t + Φ) + A cos (cot) sin {v, t + Φ)]

+ [B sin (ω f) cos (v _a t + β) + B cos (ω t) sin (v _a t + &)] .

(10)

In the system under investigation, the angles of the forward and backward beams are the same. It can thus be assumed that A = B. Equation (10) is therefore reduced to:

e _x = A sin ω / [cos (v, t + Φ) + cos (v _a t · + &)]

+ A cos ω ί [sin (ν, / + Φ) + sin (v _a t + Θ)].

Using the trigonometric identities

sin α + sin β = 2 sin | (<% + ß) ^cos i («"" ß)

and ■ ..... ■ ·

cos α + cos /? = 2 cos J (α + β) cos | (α - β) equation (11) can be converted as follows:

(H)

(12)
(13)

£ j = 2Ά J sin wt cos j

cos
2 / V

. + cosw /
Excluding the expression

·· ■ 04)

cos

7 8

and using the trigonometric identity for the sine of the sum of two angles man:

In a straight flight it can be assumed that the mathematical statement is made that a carrier __ _v arises with an angular frequency whose envelope

is. As a result, equation (15) is reduced to: io

end is amplitude modulated with the frequency. Due to the fact that the waveguide compared to the waveguide37 by a distance -? - ;;

■ * _o , I , Φ-Θ. j,. Φ + β 'e, = 2 A cos vt H sin ω t +

■ "_ :. ^: · / ig \ is offset, the stress expression can be replaced by the \

15 signals generated by the former are expressed as follows

By this equation (16) we will essentially get:

(?., = A sin

η + Φ + ^π

+ B sin \ (ω + V ₁ ) t + θ

(17)

Extending the trigonometric identity (9) and assuming that A = B , we get:
cos I

e ₂ = A sin ω t

φ -j- ^π \ _ | _ _COS [ y _u t + β - -

A] \ 4

+ A cos ω t

Φ + - "1 + sin I v _a t + θ -
/ \ 4

(18)

This expression can be expressed through the use of the trigonometric identities (12) and (13) as follows being transformed:

Φ- β

2.2 / V 2 '2 "*" 4

ο a I · I / '7 + »V, Φ + β e, = 2 AI sin ω / | cos | / +

\ IV, - V ₁₁

cos - ■ -

j \ 2

, J (v _t + Va ,. Φ + θ \. (V, -v _a -Φ-Θ, π '
+ cos ω π sin - / H sin - - - ° r + - -f ■ -

[\ 2 2 J \ 2 ■ 1. A ₁

(19)

By the expression

cos

_Φ _ + _ Θ π

is extracted, equation (19) is written as follows: e, - 2y4cos

V ₁ -V ₁₁ Φ - θ. π 1 Γ. (ν, + ν. _? ί { H sinw / cos {- ■ ''

2 2 4 I 2

_a , Φ + θ

As can be easily shown, this equation (20) reduces to: e „= 2Acosh- ^V U + ^Φ ~ ^β + ⁿ ) smLt

t-t-

"Φ + ö

If we now make v, - - v _a = ν , equation (21) is written as follows:

ey = 2A cos (vt - \ + ^:

(20)

(2i); (22);

It can be seen without difficulty that the sliding voltages e _v e _{2 of} the two waveguides 37, 38 of the

chung (22) is very similar to equation (16), with the antenna arrangement 10 'at the same time as the detectors

. , i ■ _D. u- u ^π j xn a 34, 35 supplied. On condition that"

however, a phase shift of _{4 of} the modulo _{each DeteI} f _tor34> 35, for example, a conventional

lation-enveloping, according to the cosine out- squaring device contains, can

pressure occurs. 65 output signal of the detector 34 in the following

With reference to Fig. 3, the output form will be expressed:

, ot - \ - ί ''"M-''
2

(23)

623/130

what by substitution with the following trigono- and metric identities

1 + cos 2 ix

cos ² α =

(24)

sin ² «" =

1 - cos 2 α

(25)

can be written as follows:

e'i = AA * {1 + lcos [iy, - v _a ) t + Φ - Θ]} { J + | cos [(2ω / + ν, + v _a ) t + Φ +1

(26)

The last expression in equation (26) has the The left expression inside the parentheses represents

twice the carrier frequency and is represented by the one direct current component, while the co-detector 34 filtered out. The following therefore remains: 15 sine expression on the right-hand side is the demodulated

Contains Doppler information.

ei = AA ² {1 + 1 cos [(v, - v _a ) t + Φ - Θ] } - \ . T _{n in the} same way, the output signal of the

(27) detector 35 can be expressed as follows:

Equation (28) leads again using the trigonometric identities (24) and (25) to the following expression:

cos

{v, -v _a ) t + Φ- Θ + -

il

| cos [(2w / + »'f + i' _e ) / + Φ + Θ]}.

(29)

By removing the second expression on the right with the help of a suitable filter, the result is:

t cos Uv ₁ - v _a ) t + Φ - Θ + -

(30)

wherein the cosine expression in turn is the extracted modulation envelope or the Doppler information contains. By transforming the cosine expression according to equation (30) one obtains:

e ₂ ' = AA * {i - 1 sin [(v, - v _a ) i + Φ - Θ]} · \.

(31)

In equations (27) and (31), the direct current component can be filtered out and the Envelopes can be written in the simplified form:

ei = cos (v, -v _a ) t, (32)

<? ₂ '= sin (v, -v ") t. (33)

The last two expressions indicate that there is a quadrature phase relationship between the respective detector outputs occurs.

In summary, a modified antenna assembly 10 'is used to generate a pair of microwave Doppler frequency signals which are ^{n out of} phase. This

Signals are then measured simultaneously, but separately, at a pair of voltages to generate a frequency content of

and have a phase shift of W from one another.

If now the movement is in the forward direction

45 4 /

(28)

occurs, the phase rotation direction determined by the two voltages is related to the as expression

Ov - "") »

it is assumed that this direction of rotation is in the positive direction. However, if the movement is reversed, the character of the expression changes

while that of the expression

35 not changed. As a result, the phase rotation direction of the two voltages changes, so that they now rotate in the negative direction. It can thus be determined that the information of the sign of the velocity is determined within the voltages determined by the equations (32) and (33). However, it is necessary to further treat these quadrature signals in order for this information to be in a usable form. This can be done in the following way: With reference again to FIG. 3, the outputs of the two detectors 34, 35 are fed to corresponding frequency converters 40, 41.

Each of these frequency converters 40, 41 is provided with a reference signal with a predetermined frequency offset fed, which from a common point - d. H. for example a local oscillator 42— is delivered. This local oscillator 42 may include a conventional crystal controlled oscillator, for example. the the exact frequency of this offset reference signal is not critical; however, it should preferably be substantial be greater than the highest double frequency shift to be processed in the system. Because only the reference signal fed to the frequency converter 40 is routed via a 90 ° phase shifter, , the reference signal at the input of the frequency converter 40 can be expressed by the following expression will:

cos ρ t,

(34)

while the reference signal at the input of the frequency

Γ 11 12

j converter 41 by the following expression against the output of the subtraction stage 44 the following

ben is: tension expression:

j ^{Sin Q} '' ^{(35) e} ö = cos [ot - (v, - v _u ) t] . (44)

where i> the reference frequency in radians per second 5 This means that when the helicopter is flying backwards, it can be expressed as follows Frequency e _{5 is} equal to the difference between the reference frequency e = cosotcos (v -v) t (36) compared to a frequency which is twice the size ^{: J} u \ ι a / ' ". _lo J ₆ J. Doppler shift of the two beams while the output signal of the frequency converter speaks. ...., ..: ·. 41 is given by the following equation: It is now evident that the output signal ■. _. · ",.;" / - "\ t mV der Subtraction stage 44 enough information

contains to both the speed size as

By using trigonometric identifiers, you can also determine their sign. Due to the _:

one obtains: fact that the double contained in this signal

, _f "· r ι ι \ / i ι r _t t \ a \ lerfrequency expression (v, -r.) a relatively broad spec-

e _s = I {cos [ρ t + {v, - v _a ) t] + cos [ρ t- (v, - v _a ) t]} range _{of frequencies on the slope of} a single line

(38) sequence, it turns out, however, that these data

^and 20 have to be evaluated further. As a result

e ₄ = 1 {- cos [ρ t + {v, - v _a ) t] becomes the output of the receiver - i.e. the sub-

+ coslpt - (v - v) t] \ (39) traktionsstufe44 - together with one in the

'Local oscillator 42 derived offset

If the two output voltages of the reference signal according to FIG. 3 are fed to a frequency tracking frequency converter 40, 41 to a subtraction stage 44 35 circuit 45. _r > w. as shown in FIG.

'■ __ _e _g (an) learning frequency signal to be determined, short-term frequency ^{5 3 4>} . . Smooth out jumps and generate a square wave as a usable avoidance by substituting equations (38), 30 output signal, which in (39) leads to the following expression: digital form corresponds to the speed. \, _Cos ^ _ r _t _i_ _(v _ _v \ α (i \\ The frequency tracking circuit 45 consists essen- ⁵ v \ ia \ sentlichen of a frequency discriminator in WEL

Assuming that the Doppler system chem generates an error signal in which the input frequency of a variable local oscillator is built, for example inside a helicopter, which flies in the forward direction along the demodulating bottom line obtained from the receiver, is dem Forward beam 11 ent- Doppler spectrum signal is compared. The speaking Doppler shift V _{1 is} thus positive and the comparison is made by ¹ that the Doppler spectrum associated with the backward-directed beam 12 with the frequency of the local oscillator speaking Doppler shift v _{a is} negative. The '40 tors is mixed, whereby the generated error signal Expression (v, -v _a ) is therefore positive and the same as that used to control the local oscillator until the magnitude \ v _f + v _a \. The frequency that generates a frequency at the output of the same which corresponds to the voltage occurring in the mean frequency subtraction stage 44 is the sequence of the spectrum. The error signal with - as expressed by equation (41) is then zero and the local oscillator remains at the is - equal to the sum of the offset reference voltage 45 controlled value. As soon as the center frequency changes, plus a frequency term that changes the double ■ -, an error signal arises that is proportional to the Doppler signal caused by the beams and the frequency difference, which corresponds to the displacement. ■ 'oscillator to the new center frequency of the Doppler

It is now assumed that the movement of the spectrum is driven. The local oscillator of the helicopter is reversed, in that it flies backwards after 50 speaks, therefore the center frequency of the Doppler spectrum. In this case v is negative and v _a trums. V 1 · ^ "
positive. For this reason, the term in the context of the present invention upstream (-v _u v) negative, although the amount | iv + j> _a | frequency tracking circuit 45 that is also used is the same; thus is: of the so-called sine-cosine type is schema-

55 table shown in FIG. Since this frequency lag

[(- _Vl ) - (+ v _a ) J - [-ν, - v "JI V ₁ + v _a . . Circuit is known (U.S. Patent 3 121 202)

(42) and since their details are not part of the present

Since the invention is, it is sufficient to give a short fuhk-

., \., / χ / -. to give a practical treatise on the same,

sin (- α) = —sin “and cos (- α) = cos (α) ■ ^. _c -. ·. ·. ", ...

^v ' ....... 60 The receiver output voltage _{e 5 reaches subsr}

is, the sign of the sine expression changes to a narrow one, not shown, all frequencies except

Equation (33), so that the latter is written as follows: a near band around the offset reference frequency

..'... '.' filtering bandpass filter on a conductor 50 to

e (= - sin (> 7 - v _a ) J, (43) two balanced mixers 51, 52.

65 controlled local oscillator 55 feeds the two

however, while equation (32) remains unchanged mixers 51, 52 with a signal whose frequency is in

remains. Therefore, if equation (43) is in the equation of the frequency of the on the input line

(37) and (39) is substituted, one obtains 50 flowing signals. However, before the signal of the

Local oscillator 55 arrives in'den mixer 51 is the same out of FIG. 5 via a 90 ° phase shifter 56. As a result, the output signals are of the two mixers 51, 52 out of phase with one another by 90 °. The output signals of the mixer 51, 52, which contain both the sum and difference components of the frequencies of the local oscillator 55 and des; Contain input spectrum, two low-pass filters 57 are then fed, all of the background noise frequencies remove and only let the difference frequencies pass. The output signals of this Low-pass filters 57 are then fed to a discriminator 58 in which they are multiplied with one another where a direct current error signal is generated proportional to the frequency difference. "

Due to the fact that the signals generated in each channel are 90 ° out of phase with one another the discriminator 58 can generate a signal - indicative of the direction and polarity of the error voltage .is equivalent to. It is now assumed, for example, that the frequencies in a channel pass through the expression

sin (« _v - o) _Lo ) t

and the frequencies of the other channel by the expression

cos (ω _χ - a> i ₀ ) /

are defined, where <» _{x is} the center frequency of the input spectrum and V) _{1 0 is} the ^ frequency of the local oscillator 55. If now w _x «=; co _{L 0} , the sine function changes its polarity as soon as ω _χ changes slightly above or below w _Lo , while the gosine function does not. Accordingly, this discriminator 58 generates a positive DC voltage error signal when the frequency of the local oscillator 55 is higher than the mean input frequency, while a negative DC voltage error signal is generated when the frequency of the local oscillator 55 is lower than the mean input frequency. The error signal is then fed to an integrator 59, the output of which is used to control the frequency of the local oscillator 55, the latter having an increasing voltage characteristic as the input voltage increases. Since the integrator 59, at the input of which the above-mentioned error signal is applied, has the tendency to change its output signal in the positive direction or in the negative direction when the input is negative, a negative error signal at the discriminator 58, for example, causes the frequency of the Local oscillator 55 is corrected by increasing its frequency until the error signal goes to zero and the frequency of the local oscillator 55 corresponds exactly to the center frequency of the input spectrum of the tracking position 45.

Accordingly, the output of the local oscillator 55 contains a square wave, the precisely controlled frequency of which is equal to ρ + ν , where ρ is the offset reference frequency and r is the center frequency of the Doppler input spectrum (17 - v ") . In this context it should be noted that the expression ο + r is proportional to the forward speed and the expression ρ - ν is proportional to the reverse speed. The voltage of the local oscillator 55 is accordingly fed to a subtraction stage 60. Another entrance the-. The reference voltage is also fed to the scr subtraction stage 60. This subtraction stage 60, which essentially consists of a single flip-flop circuit, is set by the signal of the local oscillator 55 and reset by the reference frequency, as shown. This subtraction stage 60 thus operates in such a way that the difference between the two frequencies is formed taking into account the sign. As soon as the two flip-flop outputs according to FIG. 5 are coupled to the corresponding input signals within two AND circles, there is a subtraction output signal from F ₁ -F. On one side and from F ₀ -F on the other _1st Assuming that F _{1 is} the reference frequency and F _{2 is} the frequency of the local oscillator 55, F ₁ -F. , Corresponds to a negative, that is, backward speed, while F ₂ -F ₁ corresponds to a positive speed in the forward direction, where these expressions are in pulsating form. The information is thus available in a usable form and can be displayed directly or used within an electronic calculating machine for navigation purposes. ^:

As is shown schematically in FIG. 6, instead of a linear waveguide arrangement, receiving antennas can consist of a pair of reflective parabolic antennas 62, 63 which are connected to a cable 64 connecting them, the taps of which are spaced apart by ^π , expressed in

Wavelengths, are arranged. Instead of parabolic antennas, however, microwave lens antennas can also be used be used.'

Claims (5)

Patent claims: 1. Doppler radar device for missiles, consisting of a transmitter generating a pulsed microwave carrier, one with the carrier of the transmitter-fed transmitting antenna, which has a beam obliquely downwards forwards and a another radiates obliquely downwards to the rear, a receiving antenna arrangement for the from the echo signals received from the two beams and a receiver received from the by the receiving antenna received echo signals generated by mixing with each other a demodulated signal, the frequency of the Doppler shift corresponds to the echo signals, characterized in that the receiving antenna arrangement (10 ') is designed so that it adds the two echo signals to each other twice, • and the second time in such a way that the second Signal by - ⁷ I- compared to the first signal has a different phase shift than the first time, so that the Doppler modulations of the both sum signals have a mutual phase shift of "■ that the receiver has two detectors (34, 35) which, by demodulating the sum signals, generate Doppler oscillations that are in phase quadrature stand to each other, and that in a manner known per se for each of the two Doppler oscillations from a local oscillator (42) directly or frequency converters (40, 41) fed out of phase ^{by 7} I and a i bib Zöö closed subtraction stage (44) are provided for obtaining an output signal whose Frequency depending on the sign of the phase difference between the Doppler oscillations and thus the sign of the missile speed by one of this speed proportional Amount is greater or less than a ■ reference frequency. 2. Apparatus according to claim 1, characterized in that in a known manner a Subtraction circuit (60) with two inputs to which a signal with the frequency of the output signal or a signal with the reference frequency is applied, and provided with two output lines is of which, depending on whether the output signal frequency is greater or less than that Reference frequency, which one or the other supplies a signal, the frequency of which is equal to the difference between the output signal frequency and the reference frequency. 3. Apparatus according to claim 2, characterized in that the one input of the subtraction circuit (60) is a square wave, which is generated with the help of a frequency tracking circuit fed by the output signal (45) is generated. ■■ - '"' ■■ '.. 4. Device according to one of the preceding claims, characterized in that the receiving antenna arrangement (10 ') consists of two linear ones slotted waveguides (37, 38), which for Generation of the phase-shifted sum signals offset from one another in the longitudinal direction are. 5. Apparatus according to claim 4, characterized in that one of the waveguides (37, 38) to- • is the same as the transmitting antenna. 1 sheet of drawings 209 623/130