DE2128082A1 - Automatically readjusting antenna system - Google Patents

Description

WESTERN ELECTRIC COMPANY Incorporated Osborne, TJL. 2

New York, N. Y. 10007, V. St. A.

Automatically readjusting antenna system

The invention relates to an automatically readjusting antenna system with an antenna arrangement including at least a first reference element and a second element, with a Diplexer assigned to each element for separating the transmitted and received waves, with a scanning device for generating a control signal in dependence on the phase difference between those of the first and second Element of the antenna arrangement received signal waves, with a circuit for combining the received, from the Elements of the antenna arrangement delivered signal waves and with a transmitter phase shifting device, which is dependent on controls from the control signal the phase of the wave emitted by the second element.

In known systems of this type, an automatic Adjustment achieved by a sequence of mixing and filtering operations with respect to a pilot signal that is one of the Phase characteristic indicating the direction of a remote transmitter. Certain changes to this

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Systems avoid the pilot signal and only evaluate the signal received in neighboring antenna elements Carrier off. However, the general restriction that applies to these modified systems is that the retransmitted frequency must be the same as the receiving frequency without additional frequency conversions. Other procedures will be phase shifters that can be changed mechanically or electrically used to get the correct phasing for a combination and retransmission. These phase shift circuits operate slowly, and the systems using them are generally not capable of full diplexing able, i.e. they cannot send and receive continuously and at the same time. In addition, the phase shifters cause considerable high-frequency attenuation, which is not readily apparent when the receiver is switched on can be eliminated by reinforcement. In addition, the phase shifters are specially trained for controlling and relatively complex control circuitry required.

The invention has set itself the task of eliminating these disadvantages of the known systems. To solve the task the invention is based on a system of the aforementioned

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Kind and is characterized in that the circuit a synchronized oscillator for combining the received signal waves supplied by the antenna elements whose phase is determined by one of the scanning device generated control signal is controlled so that the phase differences between the received, to be combined Signal waves will be a minimum.

Further developments of the invention are the subject of the subclaims.

According to the invention, a readjustment system is created in which no pilot signals and no phase shifters of the usual type are required and a simultaneous two-way operation with different transmission frequencies made possible. It was found that when coming from a distant source originating signals at two spaced antennas shifted relative to each other by 90 and mixed in a square detector, the output current is a sine function of their phase difference and indicates the direction from which the signals arrive at the antennas. This output current is then used to match the phase of the received signals for a combination

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to bring and around the same phase angle with opposite sign in the transmitted signals for the purpose of Introduce radiation towards the distant source. According to a preferred embodiment of the invention are synchronized oscillators (injection locked oscillators), which will be explained in more detail, to ' Generation of the receiving and transmitting-side phase shifts used. Since these oscillators have a phase shift

The result is an exercise corresponding to the same sine function that applies to the output current of the mixer natural adaptation.

So there is a synchronized oscillator in the coupling wfege switched between the antenna elements and the common output for the received signals, and in all coupling routes except one, which is regarded as a reference route. In a corresponding way, there are oscillators in each of the coupling paths except for the reference path between the common source for the transmitted signal and each Radiant element of the antenna arrangement is provided. Of the synchronized oscillator can be used directly as a special form of a changeable phase shifter or indirectly in the Be turned on way in which the local oscillator

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a signal of certain phase to one in the way
lying modulator supplies.

The following is a detailed explanation of the process using the drawings. Show it:

Pig. 1 the block diagram of a readjusting

Antenna system of a repeater station according to the invention;

Fig. 2 circuit details of the mixer detector

with quadratic characteristic and the synchronized oscillators, which are in block form shown in the system of Figure 1;

Figure 3 is a block diagram of a second embodiment

example of the invention;

FIG. 4 shows a diagram for the exemplary embodiment according to FIG.

required modification of the polarity connections according to FIG. 2.

It is known that when a high-frequency signal arrives at an antenna arrangement, the elements of the arrangement recorded parts of the wave look different in their phase by amounts that depend on the angle of incidence and

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depend on the position of the element in the arrangement. These wave components must be brought to a common phase position before they can be combined into a common output signal. To send a high-frequency wave of the same or almost the same frequency from the antenna arrangement in the direction of the The source for the incoming wave must correspond to the phase difference between the individual antenna elements radiated signal components the same size, but the opposite direction as the phase difference between the parts of the incoming wave picked up by the antenna elements.

Ih Fig. 1 is a system of this type by means of an arrangement of non-directional receiving and transmitting antenna elements A, A to A, which are equally distant from one another, which are all fed by high-frequency waves 10 incident at an angle from a remote station 11. It it is known that when the elements are identical, they are fed uniformly and no interaction between them is the phase difference 3> between adjacent elements, the distance d between the elements and the follow-up angle 0 determined by the direction of propagation

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by the equation

d sin O (1)

are linked, where ^. the wavelength is.

Fig. 1 shows the circuits associated _{with elements A and A 1.} As indicated by the box 12, further elements A should have circuits which are identical to the circuit _{A 1 indicated.} For the sake of simplicity, the method of operation according to the invention will only be explained with reference to the signals that are received or transmitted by _{elements A and A 1.} However, the same functions apply separately between A _n and each of the other elements, e.g. A. Since it is assumed that the signal received or transmitted by element A is the signal with which the phase of the other signals is compared, it is referred to as "reference signal" and can be described by E sin Co t, where ^ is the angular frequency of the Carrier is. In addition, it is useful to designate the _{signal received by A 1} as a "directional signal", which indicates that it contains the phase term Cf indicating a direction, that is E sin (Cot + CP).

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The signal! can send messages in the form of frequency modulation include, but to simplify the following mathematical derivations, none of these modulations is representative Expression has been provided.

The elements A and A ₁ are connected to suitable diplexers, which can be, for example, circulators 13 or 14 and separate the received waves from those to be transmitted. The output signals at the second outputs of the circulators are each applied to a limiter amplifier 15 and 16, which ensure that the signal amplitudes remain relatively constant over time. D. The primary coupling path for receiving the directional signal then runs from the second or receiving connection of the circulator 14 via an amplifier 16 to a synchronized oscillator 20, which brings the directional signal to a common phase position with the reference signal on a bus 28, where it combined with the reference signal coming from the circulator 13 and from the amplifier 15 and output at the high-frequency output to a common device 22 for using the received signals. The primary coupling path for the transmission of the directional signal can be derived in a similar manner from the radio frequency input and the common source

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Track 23 for the broadcast signal. The signals to be emitted are therefore initially divided into components for each radiation element on the manifold 29 divided. One of these parts goes to the synchronized oscillator 21, is then there in shifted in phase with respect to the reference signal then fed to the third or transmit port of the circulator. The path for the reference signal representing, Part runs from the high-frequency input to the transmission connection of the circulator 13.

The control path includes a mixer detector 24 with a quadratic characteristic, which is connected so that it is a Sample both the reference signal and the directional one The signal. It is therefore a sample of the reference signal via a phase shifter 25 with a fixed phase shift led by 90, which converts it into the form E sin (cot - 90) or E cos 4A> t. These

phase-shifted sample of the reference signal, which is now close to _. to a 90 relationship to the directional signal E sin (^ jt + (P) possesses, is then directed along with a sample of the Signal fed to the Mis rather detector 24, which the two Combines samples, squares and delivers a rectified output current to the busses 26 and 26a.

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The structure of the mixer 24 and the equations applicable to its operation will be explained in greater detail later. For the moment, however, assume that the mixer provides a signal which is a given function of v ^ such that the current on busses 26 and 26a controls the synchronized oscillators 20 and 21 as a function of ψ. The phase-shifted reference signal supplied by the phase shifter 25 is also fed via the bus 27 to identical circuits connected to the other antenna elements A.

The structure of the synchronized oscillators 20 and 21 and the equations applicable to their operation will be explained later. It is assumed here, however, that both oscillators produce a phase change in the signal running via their main signal path which is proportional to the control current on the bus 26 or 26a. Since this current is a function of ff? the shift caused by oscillator 20 can be made -Cp , the phase shift required to remove the phase shift term in the directional signal so that it becomes equal to E sin cot and in phase on bus 28 with the reference signal and the

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input signals of the other circuits 12 can be combined. In a corresponding manner, the phase shift of the oscillator 21 can be made equal to - ^, namely the phase shift that is required to convert the signal from the high-frequency input into E sin (cot - ψ) , such that it is radiated from the element A ₁ is directed at station 11. The circuits 12 generate in a corresponding manner different phase shifts for the signals to be emitted by the antenna elements A, in each case as a function of the difference between the phase of the directional signal received by the respective antenna element and the phase of the reference signal received by the antenna element A.

In Fig. 2, the circuit details for typical embodiments are sbeispiele the mixer detector 24 with square Characteristic curve and the synchronized oscillators 20 and 21 are shown. The detector 24 is a symmetrical one

Mixer and contains a pair of diodes d ₁ and d_ with quadrant Δ

table characteristic. These diodes can be Shottky diodes or any other purpose-built rectifier diodes. The diodes ά _Λ and d are pushed-pull through the over-

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carrier 41, to which the signal E sin (cot + <p) is applied, and in parallel by the transformer 42, to which the signal E cos tfot is applied. The resistors 43 and 44 with a sum resistance R form the respective diode load, and capacitors 45 and 46 represent high-frequency shunts.

The resistors 43 and 44 are each much smaller than that Diode resistors, so that the current in each resistor is essentially equal to the diode current assigned to it is. Since the characteristic curve of the diodes is square, these diode currents are in turn proportional to those applied to the diodes Stresses e and e. The resulting output

CIi CIu

output voltage e is the difference between the voltage components of the individual diodes and can be expressed

β = R <4 - 4) (2,

It also applies

e "= E cos " © t + E sin (cAat + if) dl I

and (3)

e, _o = E cosiOt - E sin (ait + ¹ P). dz '

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Inserting equations (3) into equation (2) results in:

e = K. R (sin γ + sin (2 good + f) ) (4)

where K _{1 is} a constant that contains all signal amplitude factors. If modulation terms representing messages had been included in equations (3), these terms would cancel each other out. The second term in equation (4) is a high frequency signal 2 cot that is canceled by capacitors 45 and 46. It then remains

e = K ₁ R sin f . (5)

The voltage e now has to be converted into a current. Numerous ways of doing this are known to those skilled in the art. In a preferred embodiment of the invention a single operational amplifier or a DC amplifier stage is used that has a high input resistance and has a low output resistance. Furthermore, suitably separate amplifiers 47 and 48 become separate Supply of the synchronized oscillators 20 and provided. The output voltage e of each amplifier (namely the voltage on the bus 26 or 26a in

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Pig. 1) can then be expressed as

e ₀ = K ₁ K ₂ sin <p (6)

where K is the amplification factor of the amplifier

al

holding constant is.

Let us now consider the structure of the identical synchronized oscillators 20 and 21. Any free running oscillator can be used that is electrically can be controlled and can be synchronized by a further signal whose frequency is different from the frequency of the free-running oscillator, but is within a so-called locking range. Corresponding A preferred embodiment of the invention can be considered for the oscillator 21, which is illustrative a so-called IMPATT (Impact Avalanche and Transit Time) diode .51 can be used, 'which are in a Article "The IMPATT Diode - A Solid State Microwave Generator" 45 Bell Labs Record 144, May 1967 is described.

The capacitor 53 and the choke coil 54 provide the required Decoupling between the bias sources and the high frequency circuit. The input signal for the synchronization is at the 1st connection 56 of a circulator

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55, which sends the signal to the high frequency circuit of the diode. coupled. This is indicated schematically by the coil 52, shown in broken lines, coupled to the diode, and by the second connection 57 of the circulator 55. The output power is taken _{x from} the third connection 58 of the circulator 55.

If the IMPATT diode 51 ^{is biased to the correct operating point by the A 7} voltage source 50 (in series with the voltage e from the amplifier 48), the relationship applies

between a change in the natural resonance frequency Cy is the change Δ I in the bias current, where K is a constant diode parameter.

If the oscillator is synchronized by a signal E sin OOt supplied via input 56, then at output 58 there is a signal with the same frequency ίο as the supplied synchronization signal, but with a phase shift \ o which is directly dependent on Acu according to the relationship

^{SÜ1 <} f 0 ⁼ ^ 7j £ ~ ^Q

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where Q is the quality of the external circuit of the oscillator and G is the ratio of the output power to the supplied power Power of the oscillator is. A change in the bias current flowing through the diode 51 thus causes a phase shift of the output signal with reference to the supplied synchronization signal.

Note, however, that the bias current has a fixed proportion due to the source 50 and has a variable portion due to e. The fixed current component is proportional the voltage of the source 50 and is adjusted so that the natural resonance frequency - 3 of the free-running Oscillator in the absence of the changeable current component, i.e., when e is zero, it is equal to that of the supplied synchronizing signal. The changeable share of electricity results according to equation (6)

^e 0 ^K l ^K 2 ^Sin Ψ

^ΔΙ . "ΪΓ ■ ⁽⁹⁾

d d

where R is the equivalent DC resistance of the diode bias circuit is. Substituting equations (7) and (9) into equation (8), one obtains

K ₁ KK

sintP _n = ( ■ Q Vcf) sin *. (10)

^{0 R} d '

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It is easy to choose all of the constants within the brackets in equation (10) so that the expression in brackets equals one. Then we have sin * f _n ⁼ sin IP. This means that the current derived from the mixer detector 24 and following a sine function supplies precisely that function which causes the synchronized oscillator 58 to introduce the phase shift required in accordance with the explanation of FIG. The sign of the phase shift introduced depends on the particular type of diode used. Usually, for example with IMPATT diodes, the phase shift has u? _{n has} the same sign as Δ I _3, which means that the natural resonance frequency increases with the bias current. The connections indicated by the polarity designations for the amplifiers 47 and 48 are therefore correct for obtaining a negative value Q>, ie, a phase delay. A reversal of these connections would lead to a positive value U>, which is required for an exemplary embodiment to be described later. The oscillator 20 is identical to the oscillator 21 and shifts the supplied synchronization signal in a corresponding manner by C ^ _n equal to &. Since the current following a sine function is not unique for angles greater than + 90, the number of elements of the antenna arrangement and the distance d between

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can be chosen according to equation (1), that «f> has the value for the required caster angle 0 Does not have to exceed + 90.

From the above explanation of the invention it can be seen that significant advantages are achieved over known systems will. So there are no special properties, for example a reference pilot signal, for the remote one Station 11 requires incoming signal. The invention also enables simultaneous two-way operation. Though the use of the same frequency for transmitting and receiving has been described to simplify matters, but it should be clear that the synchronized oscillators 20 and 21 do not operate on the same frequency have to. With the correct scale setting of the oscillators and the amplifiers 47 and 48, according to the In practice, transmission and reception operations can be carried out at different frequencies.

The system of Fig. 1, however, has certain limitations resulting from the fact that the The synchronizing signal used in oscillators 20 and 21 is the message signal itself. Equation (8) and its factor

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G show that the amplitude of the synchronizing signal for a given phase shift must be constant. Therefore, the limiter amplifiers 15 and 16 are used, whereby a Amplitude modulation of the carrier is excluded. There In addition, the synchronized oscillators 20 and 21 are inserted directly into the primary receiving and transmitting paths to some extent the permissible modulation index of a frequency or phase modulated carrier.

These limitations are in the embodiment shown in FIG switched off. Essentially, the improvement results from the fact that the synchronized oscillators are separated from the primary signal paths by modulators and that their synchronization signals are independent of stable ones Oscillators are derived. This allows considerable adaptability for the choice of both reception and reception also causes the transmission frequency and also created the possibility that the output and input frequency without use a second frequency converter stage can be.

For the sake of simplicity, components in Fig. 3, which correspond to those in FIG. 2, the same reference numerals have been used.

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The main difference can be found in the coupling paths for the Detect directed signal, in which a receiving modulator 30 is now in the receiving path from element A. and a transmitting modulator 31 are inserted in the transmission path to this element. These modulators are both of a type that usually used as an up and down wiper in high frequency Facilities is used. The one corresponding to the local oscillator that is usually used However, the signal is derived from the output of the synchronized oscillators 32 and 33, respectively. As stated, everyone knows Oscillator 32 and 33 have an output frequency that differs from the reception and transmission frequencies by the desired Intermediate frequency is different. The transmission and reception frequency can be selected independently of each other. However, this independent option as well as the frequency conversion to an intermediate frequency represent additional features and do not necessarily represent limitations of the system. If the transmission and reception frequencies differ significantly from each other, so scaled or separate antenna arrangements are required, as in an essay "Self-Steering Array Repeaters" by C. C. Cutler et al The Bell System Technical Journal, September 1963, page 2013.

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The synchronizing signals for the synchronized oscillators 32 and 33 are provided by local receiving and transmitting oscillators 34 and 34a with fixed amplitudes and stable frequencies which are equal to the desired output frequency of the respective synchronized oscillator. The natural resonant frequency of each synchronized oscillator 32 and 33 is controlled by the voltage on buses 26 and 26a as discussed above (a function of the phase difference cp of the signals received _{from elements A n} and A _1).

The reference signal coupling paths contain the receive modulator 35 and the transmit modulator 36 on the paths to the element A, in order, if necessary, to carry out a frequency conversion to or from the intermediate frequency, but without introduce some relative phase change. The modulators 35 and 36 are signal through a local oscillator fed, which is derived from the same sources 34 and 34a, but for the sake of simplicity as separate sources are shown.

If the signal designations used in connection with FIGS. 1 and 2 are used, the signal E is sin cot from the element

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OO

A received and fed to the modulator 35. The signal E sin (out +. * F) is received by the element A ₁ and sent to the modulator 30. The local oscillator 34 has a frequency <UU, where ei OU- Dj is the intermediate frequency ijj . The output signal of the synchronized oscillator 32 is E sin (W_.t + cf>), and after mixing in the modulator

Jti ■ ü

30 with E sin (Ccvt + Φ) the difference signal given to the collecting line 28 is equal to EK sin (( (jy- 6O _R ) t ^{+ t} f * - 4PÜ

where K is the converter constant. If ψ is made equal to νσ, then the output signal of the modulator 30 is the signal EK ₀ sin0O -n't · The same conversion without a phase change

ο JLJb

takes place in modulator 35 with delivery of E sin <A? _TT , t instead,

JLb

so that the output signals of the modulators 30 and 35 are coherent on the bus 28 are combined with the output signals of the corresponding circuits in box 38.

The transmission path must have a phase shift for the directional signal are introduced whose sign corresponds to the sign of the phase shift introduced into the receive path is opposite. Referring to Fig. 4, this reversal can be done in a number of ways, including interchangeability the polarity connection of the voltage e done with the operational amplifier 48a, the synchronized

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Transmit oscillator 33 controls so that the signal from amplifier 48a is equal to -e, that is, the inverse of e from amplifier 47 and amplifier 48 in FIG. _T Tpt received and shared on bus 29. The local transmit oscillator 34a has a frequency (KJtf - tjj), where

1 IJf

is the desired transmission frequency. The modulator 36

thus sets the frequency of the reference signal emitted by element A into the transmission frequency E sinoy? _T t without a phase change. The output signal of the synchronized oscillator 33 has the form E sin ((ct> _T - UXp) t - γ), and after mixing in modulator 31 with the signal E sintA> _TF t, the sum product EK sin emitted _{by element A 1 is (} Öbrpfc - ^ P), like that for sending out into the

oil/

same direction is necessary from which the signal was received. . ■

Separate synchronized oscillators 32 and 33 have been used to simplify the explanation. allow greater freedom in the choice of frequency. It should be noted, however, that the receiving modulator 30 and the transmission modulator 31 can be fed by the same synchronized oscillator, provided

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that the desired transmission and reception frequency are not significantly different from one another and that the modulator is modified in a known manner so that it changes the phase of the carrier signal with respect to the oscillator signal im Inverted compared to the phase positions in the modulator 30.

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Claims (1)

PATENT CLAIMS lj Automatic readjusting antenna system with an antenna assembly including at least a first reference element and a second element, with each Element associated diplexer for separating the transmitted and received waves, with a scanning device for generating a control signal in dependence on the phase difference between those of the first and second Element of the antenna arrangement received signal waves, with a circuit for combining the received, from the elements of the antenna arrangement supplied signal waves and with a transmitter phase shifter which controls the phase of the wave emitted by the second element as a function of the control signal, characterized in that the circuit for combining the received, supplied by the antenna elements Signal waves has a synchronized oscillator (20, 32), the phase of which is determined by one of the scanning device (24, 25) generated control signal (26) is controlled so that the phase differences between the received, too combining signal waves become a minimum. 10985 1/1220 2. Antenna system according to claim 1, characterized in that the scanning device has a 90 phase shifter (25) which shifts the phase of a reference signal from the first reference element (A), and a mixer (24) contains a quadratic characteristic, which generates a control signal (26, 26a) which is derived from the phase difference between depends on the signals received by the first and second antenna element (A A). 3. Antenna system according to claim 1 or 2, characterized in that the transmission phase shifting device one synchronized oscillator (21, 33), the phase of which is generated by a from the scanning device (24, 25) Control signal (26) is controlled so that the signal transmitted by the antenna arrangement in the same direction is radiated from which the received signal wave arrives. 4. Antenna system according to claim 1, 2 or 3, characterized in that the transmitter phase shifting device a transmission modulator (31) which is connected between the synchronized oscillator (33) and the diplexer (14) and converts the frequency band of the signals (29) to be transmitted. 109851/1220 δ. Antenna system according to claim 1, 2, 3 or 4, characterized in that the circuit has a reception modulator (30) for combining the received, supplied by the antenna elements signal waves, which is connected to the output of the _v-locked oscillator (32) and the frequency band received, converts the to be combined signal waves. 6. Antenna system according to one of the preceding Claims, characterized in that the synchronized oscillator (20, 21) (32, 33) has an IMPATT diode (51). 109851/1220 Blank page