DE2141832A1 - Device for generating high frequency pulses of short duration - Google Patents

Description

377 -

SPERRY RAND CORPORATION New York / USA

Device for generating high frequency pulses with

short duration

The invention relates to a device for generating high frequency or microwave sinuaso oscillation signals with a duration on the order of one nanosecond and in particular on a device to generate such pulsed signals with abrupt Rise and fall characteristics with essentially no energy emission before or after the impulses »

Various known attempts are described in the literature ben, systems for the generation of very short pulses of high frequency or to develop microwave signals. In general, one method has involved the synthetic generation of such pulse-shaped signals by exciting a pulse-shaping end Network with an abrupt jump function voltage Various networks were used to convert the incident jump wave into a Reohteo pulse.

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When using increasing carrier frequencies, especially in the C-band and above, the output pulse waveform deteriorates such known systems are very strong. This deterioration leads to increased testicular spreading higher Order of the network connections and increasing losses and thus corresponding scatter in the network transmission lines. Am another obstacle to being successful Continuing this technique is the general inversely proportional relationship between the output signal level the microwave generator and the increasing frequency .

Systems have also been devised for generating pulsed outputs that do not require carrier phase synchronization with respect to the pulse waveform. For example, a holder in series with a continuous wave oscillator can be opened and closed very quickly in a simple manner in order to generate the desired pulse-shaped signal with a short duration. However, the shunt capacitances of available switches are finite and severely limit the on-off ratio of the output pulses. In addition, like abrupt rise and fall tents are desired for Impulssohwlngungsform and switches that my in general W at an acceptable cost open are available and do not close at the same speed and therefore result in undesirable unbalanced Ausgangslmpulse.

A device according to the invention for generating high-frequency, time-limited pulses with short duration and with abrupt rise and fall characteristics comprises a first high-frequency transmission arrangement with a predetermined characteristic impedance Z _Q and input and output arrangements, a high-frequency oscillation oscillator arrangement for supplying a sequence of high-frequency sine

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Oscillation cycles to the input arrangements »a Sohaltvorriohtung having a secondary capacitance C. for gate control of the oscillating door arrangement, adapted utility means connected to the output arrangement and an idle branch transmission line arrangement which starts with the first transmission line arrangement at a distance dg is connected from the input arrangement, the distance d ^ is set so that sioh essentially results in a resonance between the input arrangement and the shunt capacitance C _{- of} the switch.

The distance dL can be adjusted so that the reactance the first transmission line arrangement essentially is equal to the reactance of the switching device in resonance. Alternatively, the distance d_ can be set so that the

Ta

Control point impedance of the from the first transmission line processing arrangement and the branch transmission line arrangement existing network is essentially equal to the reactance of the switching device at resonance 1st. The invention thus results in a device for generating pulse-modulated, high-frequency carrier signals with a pulse duration in the On the order of a nanosecond and with sharply delimited rectangular QUU curves. It preferably becomes an excitement the electromagnetic wave propagation in the TEN testicle used in the network that has a time-limited response characteristic depending on an injected pulse or a step-modulated high-frequency input oscillation having.

The invention is illustrated below with reference to in the drawing Ausftthrungsbelpiele illustrated still further explained.

Zn the drawing show s

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1 shows a schematic circuit diagram of a first embodiment according to the invention,

Pig. 2 is an explanatory diagram for facilitating understanding of the apparatus of FIG. I,

Figures 3> 4 and 5 are graphical representations of the by various Settings of the circuit according to FIG. 1 generated Auegange waveforms,

6 and 7 are equivalent circuits used to explain the Operating mode of the circuit according to Fig. 1 can be used »

Flg. 8, similar to FIG. 1, a schematic circuit diagram another embodiment according to the invention,

Flg. 9 is a partially schematic plan view of a practical embodiment of the invention;

Fig. 10 is a partially sectioned plan view of another embodiment according to the invention.

The invention is in the form of a radio frequency transmission line switching circuit for generating pulse modulated in the order of magnitude represented by a nanosecond. The generator used a pulse-shaping network with a time-limited Impulse Aasp ^ oheharakterietlk, which is modulated by a source for jump high-frequency energy is controlled. Passive, the network © lg @ zie properties can help achieve a sharp Fall of the impulses to produce a sharply rectangular one

be used.

Besß Zua "F" i understand the invention was initially the network nfeefe FIG. I considered. A loss-free two-wire transmission line 3, 3a with a wave resistance or a characteristic impedance Z _Q extends over a distance D between the impedance reference levels 4 and 5 -Transmission line 7, 7a conductively attached, which extends over a distance L from the line

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device 3, 3a extends and which is open at its outer end ends 8 »8a. The Stioh transmission line 7 » 7a has a wave impedance Z_ and forms a pulse shape end

Network 10 together with the main transmission line 3, 3a. Various types of non-dispersive, low-loss transmission lines can be used for lines 3 * 3a and 7, 7a, including transmission lines that transmit progressive high-frequency or microwave signals in non-dispersive testes, such as in the TEM mode . The normalized wave resistance or the characteristic impedance Z _{0 of} the transmission line 3 »3a can be 1 ohm, while that of the line 7, 7a must have half the characteristic impedance of the line 3 or ^ 0.5 ohm.

The network 10 can at its input terminals in the plane with the help of a pulse or a repeated sequence of pulses are excited by a pulse generator 11 of known type with one through the resistor 12 of R ohms indicated internal resistance can be supplied to the input. χ A pulse supplied by the generator 11 passes through the pulse shaping network 10 to a resistance or Absohlußlast 15 continued, a radiating antenna or a be another matched useful device with the resistor R ^ can, which can also have a standardized value of 1 ohm.

Bs has been shown that when the network 10 is controlled by such a pulse signal the output response a (t) of the network 10 along the load resistance 15 with a value of 1 ohm from two pulses 20 and 21 with the same sign and area exists as shown in FIG. Of the Impulse 20 escapes after the time D / o seconds after the tent, at which the input impulse reaches level 4, where the Symbol ο the speed of energy propagation along the transmission line 3, 3a designated. The impulses 20 and 21

./. Ji - A normalized value of 1 ohm can be selected,

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are separated by a tent interval of T-2L / c seconds. Such properties of the network IO are in the literature "A New Mlorowave Phase Equalizer Network" by O.P. Roes * I.B.E.B. Transactions on Mlorowave Theory and Techniques, Pages 647 to 650 November 1967.

Under the above impulse excitation conditions it can be said that the network 10 has a time-limited impulse response characteristic where the value of a (t) for all times t> D + T »D + | = zero 1st. The importance of such Type of time-limited response character is derived from the Investigation of the output of the pulse-forming network 10 for a step-modulated excitation with a nominal carrier frequency f, which is centered at f_, can be seen, where f

1 "5 * 5 ( 2K 1 \

Can take on values such as f _Q » - $$>% $ * 2T ' '

where k is an integer. As shown in FIGS. 3, 4 and 5, the output of the network 10 is equal to zero for t> T seconds, regardless of the initial phase of the sinusoidal input pulses.

3 shows, for example, the case for a signal with a nominal centering _{frequency f o} -l / 2T, an output pulse with the duration T being formed. The tentative period following the end of the interval T represents a forbidden area "in which the binge oscillation cannot contribute any energy to an output signal." of f _Q, however, is now 9 / 2T. The same forbidden Bereloh is shown with dashed lines through solenoid shapes. Fig. 5 is similar, but with f _Q -3 / 2T and an initial phase that is not equal to zero and therefore represents a more general case Here, too, the period T following the brew of the time represents a forbidden period and there is no output signal.

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If the value of k in the set (2k-l) 2T is not an integer, the aprung-modulated response of the network 10 for t> T is no longer zero and the output signal is no longer an impulse. On the other hand, for any integer value of k, an I-pulse output waveform of the desired HtSl curve shape appears along the end or the last 15 If k is an integer significantly greater than I , there are many high-frequency cycles within the HU2kui * ve Irapulsauangangesignals. The greater the value of k, the smaller the distance between the permissible output frequencies ai, for example, for a given pulse duration T ^ SL / s seconds and k »1, there is a number of discrete frequencies for which the equation f _Q T» i2k- l) / 2 in weewitllehen; can be done *.

The above explanation of the B8ti »i @ tef © iis @ ä © © © tmpulmt forming network 10 was © somewhat to ü®w If you look at it, it was stated that certain practical® considerations were v © ma © tili8siiife & @ a" ¥ or all things became «especially for Wv®qy.®nzm © 'mwialh of the X-Bandee the N @ bens © hluS-ifepaaifcIt of within the generator 11

and controls the end of the pulses.

out ter-secondary sole capacity

exploited "

der HebeasofeluS-iCapasitlfe © in © s !! © äMlatiöas ^ QliaiL ^ Qg'ßj 22 may. to Figures 6 B®sug _e s h © © © e ISJ werdijQ "Sa Figo β * is tes pulsf © @ nä rm <i N®tssw @ 1 Fk with © © iaesa
11 a with the switch open
des dene ^ atoys and di «M®fe @ ae © & lmlkap © connected * where di @ 8® ^ © paaifelt dur © fe ®ln®m w © rd« a kami ₀ Di © a (t) won ünm network 10, which appears along the · & ng @ pa®tsa L & Bt 15, is zero, independent of the values wm

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is "the duroh the Stloh-Übertragungeleltung 7 7a at f" causes and that due to the effective Kurzschlußeohaltung f · The Oruse and carrier phase of the output pulses depends jedooh In critical catfish of the voltage V ₈ in enggesohwungenem state along the NebensohluBkondensators 22 to the tent from * at which the switch 22 is closed sail.

The above-mentioned relationships can be made with reference to Flg. 7 can be mowed easier to understand. When the switch 22 is closed, the effective resistance r _{ß of} the switch Ψ suddenly drops to zero, so that the voltage across the capacitor 23 must drop to zero (the voltage between points A and B falls to zero). This is equivalent to the abrupt insertion of an generator source 24 with the same potential V ¹ and opposite sign in series with the voltage V.

As mentioned above, the output appearing length of the load 15 in the steady state is independent of the value of V _e zero. So the answer is reason

the voltage E _M in series with the voltage V_ zero. Another-

g ^B

on the other hand, after t "D / c" the output response depends directly on the fact that V ₈ '"V _8. Thus, in order to maximize the pulse _{output voltage, the value of V 8} must be maximized, because it actually determines the amplitude of the output signal a (t ) certainly.

A maximum value of V_ can be achieved by using a series resonance effect, for example if the control _{point impedance} Z dp (Pig 7) of the pulse-forming network is inductive in the balanced state and the following relationship is fulfilled _{at the frequency ff Q}

² dp - ^X L - ^x s

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In Oleiohung (1), Z _{dp ale is defined as the sine control point impedance in} the steady state, as it is measured at the input terminal of the pulse-shaping network 10 at any frequency f. The quantity X ₀ is the capacitive reactance of the switch 22 in its normally open mode of operation at the frequency ff _Q , and X _L is the inductive reactance which appears at the input terminal of the pulse-forming network 10 when f «f. The quantity Z. is purely inductive and only at f «fj \ X _L. It can be seen that the desired relationship between the respective line and switch reactances Xj ₁ and X ₈ and the factor Z ^ -duroh suitable selection of the values of the distance d (Figo 1) between the reference plane 4 and the plane 6 is achieved, mn which the branch branch line 7, 7a forms the connection with the line j5, 5a. This results in a resonance between the network input and the shunt capacitance C _{3 of} the switch 22, because the connection of the branch line 7, 7a represents an effective short circuit connection.

Under the above circumstances, the value is the drive point impedance Zg 'in the steady state for the network 1Oi

^z dp * ^JZ o ^tan ^

β - 2 if f _o / c.

The required maximize © nd © - * W @ rt ä from equations 1 and 2 as follows

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1st:

d ~ i tan " ¹ Q (3)

m μ

Here the factor Q is the usual quality factor of the resonance circuit. Under the above conditions, the voltage V _{8 is} given by:

V ₈ - -j QE _g (4)

When looking at Flg. 1 and 2 can be seen “that the Peak output power during the duration of the output pulse * see along the load 15 equal:

V ₈

is.

In general, the signal ^a ( ^fc ) spit _ze ^{senr e closely resembles the} pulse waveform as shown in Fig.5.

It can be seen from the analysis of FIGS. 1 to 7 that the Invention carried out in any of several ways can be. For example, the unsynchronized Jump-modulated Snusechwingungs-Oenerator 11 according to Flg. 1 any expedient, relatively stable high-frequency oscillator be »and this can be connected in series Include control or gate control bracket 22 which either a single-pole mercury-wetted mechanical circuit breaker or a voltage-controlled semiconductor switch of the usual type Kind of can be.

Flg. 8 söigt schematic ti sail dia form of a two turn-Obe ^ tragungsleitungssystem and is "provided below in connection with the practical Auefütirangsbelsplel nmli FIG. 9 s ^ lSutert" of in 'the form © la @ o koaxial® "übertragungsleitimgssystems represents. Flg. 8 is the same in many ways © ijisia T @ il

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According to Fig * 1 and corresponding parts are therefore denoted by the same reference numbers duroh. For example, the two-wire transmission line 3 # 3a extends between the impedance reference planes 4 and 5 *, from which a two-wire no-load transmission line 7, 7a branches off with a length L «whose connection point with the line 3 * 3a in the reference plane 6 with at a distance d from the plane 4, as defined above. The value d is again set essentially to the value d _m which results from equation (3). The pulse-shaping network 10a according to FIG. 8 now includes a second no-load two-wire · branch transmission line 17, 17a also with a length L, the connection of which with the line 3, 3a is also arranged in the reference plane 6, in accordance with the connection of the branch line 7-7a and at a distance ^ _n from the reference plane 4. For a practical application, the lines. 3, 3a and the branch lines 7 * 7a and 17, 17a all have a characteristic impedance of 50 ohms. It can be seen that, given a suitable value of the factor d _ffi , the network 10a works essentially in the same way as the arrangement according to FIG. 1, as it is connected to the pulse generator 11 and the load 15 according to FIG.

The practical embodiment shown in Fig. 9 of the er » The invention has an internally pulse-modulated generator 111 which is similar to the generator 11 according to FIG. 1 and at a reference plane 104 with a coaxial transmission network 110a, whose output pulse oscillation a (t) is connected to a reference plane 105 with an adapted load 115 connected is. For reasons of expediency, they indicate the parts of the network 10a according to FIG. 8 corresponding parts of the network HOa have the same reference numerals, but increased by a factor of 100 on.

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Zn Flg. 9 Let the network 110a off in an expedient manner easily available coaxial transmission line components formed to create a cruciform arrangement. This arrangement comprises a main coaxial transmission line 103, 103a, their center conductor 103 is connected to a generator 111 and an end load 115. The opposite leads of the generator 111 and the load 115 are grounded, as is the outer conductor 103a of the line 103, 103a. The network 110a is with radially or oppositely branching coaxial lines 107 * 107a and 117 «117a are formed. The latter are on the connection 125 lying in the plane 106 is shown in section to the intersection connection at point 125 of the Inner conductor 107 and 117 with the inner conductor 103 of the main transmission line 103, 103a. The coaxial outer conductors 107a and 117a are like this with the outer conductor 103a connected as shown by the dashed lines and are also at ground potential. Farther is the distance between planes 104 and 106, which are the reference planes 4 and 6 correspond essentially to the value defined above.

Fig. 10 shows a modification HOb of the network HOa 9, which has additional features to be sought in certain applications. The structure is electric dee naoh Fig. 9 equivalent, but with the radially extending Coaxial lines 107 «107a and 117 * 117a, which the Fora of flexible coaxial cables bent into a generally circular loop. The respective open ends 123 and 123a of the lines 107 «107a and 117 »117a are directly connected to one another in a leading relationship, as in a level 126 according to Flg. 10. It is understandable that this part of the loop is above the plane of the drawing near Fig. 10.

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The mode of operation of the embodiments according to FIGS. 9 and 10 is the same, because all signals in turn cover the same range in both exemplary embodiments. The signals returning from the conductors along the same paths to junction 123 of FIG. 1 "on which they left it initially" return to those in FIG. 10 along the opposite branch transmission line. In the device according to FIGS. 9 and 10, all transmission line elements can expediently be standardized commercial 50 ohm components. An additional advantage of the arrangement shown in FIG. 10 is that the output pulse duration depends on the lung of a single continuous cable loop. Furthermore, no energy can occur around a non-perfect open circuit 123 οά @ τ 123a and signals flowing against one another must run along the same path.

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Claims (6)

2H1832 claims x 1.) Device for generating high-frequency, time-limited pulses with short duration and abrupt rise and fall characteristics; characterized by a first high-frequency transmission line arrangement (3, 3a) with a predetermined characteristic impedance (Z ^ and input and output arrangements, a Hoohfrequenz-Slnussohwingungs-Oszilla door arrangement (Ll) for supplying a sequence of high-frequency sinusoidal oscillation cycles to the input arrangements, one in the non-sliding State of a switching device (22) having a shunt capacitance (C) for gate control of the oscillator arrangement (11), adapted utility means connected to the output arrangements and an idle intermediate transmission line arrangement (7 * 7a) which is connected to the first transmission line arrangement ( 3, 3a) at a distance (d _R) ) starting from the input arrangement, the distance (d_) being set so that there is essentially a resonance between the input arrangements and the shunt capacitance (C ₈ ) of the switch (22) results. 2. Device according to claim 1, characterized in that the distance (d) is set in such a way that the reactance of the first transferring solution arrangement ($ _B 3 &) h®i resonance essentially the reactance of the switching device (22 ) 1st. 209809/1214 " ¹⁵ " 2U1832 3. Device according to Claim 1, characterized in that the distance (d_) is set in this way is that the drive point impedance of the network (10) from the first transmission line arrangement (3 # 3 «t) and the branch transmission line arrangement (T * 7a) at resonance essentially equal to the reactance the switching device (22). 4. Device according to one of the preceding claims, characterized in that the greetings (d _m ) essentially by the equation ^d ra * JS ^tan " ¹ ^ ¹ j is determined, where β « 21C f ₀ / c and where f is the operating frequency of the oscillator arrangement (11) and ο the wave propagation speed in the first transmission line arrangement (3, 3a). 5 * Device according to one of the preceding Anspiü @ h @, characterized in that the open or idle branch transmission line arrangement (7,? Aj, which is connected to the first transmission line arrangement O >> 3a), two coaxial transmission lines ( 107, 107a; 117, 117a) which extend radially in opposite directions from the first transmission line (3 * 3a) and are open at the ends remote from the first transmission line arrangement. 6. Apparatus according to claim 5, characterized in that the two coaxial lines (107, 107a; 117, 117a) are shaped into a loop, and that their open ends are connected to one another in a direct conductive relationship. 209809 / 12U 2U1832 Device according to one of the preceding claims, characterized in that the characteristic impedance (Z ₈ ) of the branch transmission line (7 * 7a) is half as great as that of the first transmission line O, 3a) 209809/1214 L e r s e i t e