US2773198A - Trigger circuit of the magnetic or dielectric type - Google Patents

Description

s. DU!NKER 2,773,198

TIC OR DIELECTRIC TYPE Dec. 4, 1956 TRIGGER GIRCUIT OF THE MASKS 2 Sheets-Sheet 1 Filed July 23, 1953 .t rili l m UX INVENTOR SlMON DUINKER AGENT Dec. 4, 1956 s. DUINKER 2,773,193

TRIGGER cmcurr OF THE MAGNETIC OR DIELECTRIC TYPE Filed July 23, 1955 2 Sheets-Sheet 2 INVtNTOR SIMON DU \NKER AGENT United States Patent TRIGGER CIRCUIT 1 F THE MAGNETIC 0R DIELECTRlC TYPE Simon Duinker, Eindhoven, Netherlands, assignor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application July 23, 1953, Serial No. 369,793 Claims priority, application Netherlands August 7, 1952 17 Claims. Cl. 307-28 The invention relates to trigger circuits of the magnetic or dielectric type which include a variable reactance comprising a medium which is operated in a non-linear part of its polarization characteristic curve and having supplied to it signal oscillations, preferably pulsatory oscillations, and also a supply oscillation the frequency of which is high as compared with the repetition frequency of the signal oscillations, and in which the efiective value of the oscillation across the reactance which is set up under the action of the supply oscillation can be increased to a comparatively high value by signal oscillations of definite polarity and be reduced to a comparatively low value by signal oscillations of opposite polarity.

in a known trigger circuit of the magnetic type in which the variable reactance is constituted by a coil the core of which is made of non-linear ferromagnetic material the output current is rectified and then fed back to the input circuit. if the feed-back is properly adjusted two discrete stable conditions separated by a region of unstable conditions are found in the relationship between output alternating current voltage and input direct current. Pulses of suitable value and direction in the input circuit cause the circuit arrangement to pass from one stable condition to the other and vice versa, a large eifective value of the output oscillation being set up in one stable condition, a small one in the other stable condition. Some important disadvantages attach to such circuit arrangements, since generally a Graetz arrangement is used to rectify the output current and this requires the use of four rectifier cells.

The ohmic resistance of the Graetz arrangement is connected in series with the supply generator and the coil operating as a variable reactance, resulting in an undue linearizing effect on the required non-linear properties of the circuit.

in addition, the output power is largely dissipated in the rectifier resistor which acts as the only load, so that little power is left for the control of any subsequent trigger circuit connected in cascade with the first one.

The invention obviates these disadvantages and is characterized in that the variable reactance is coupled to a second reactance of opposite polarity, the characteristic curve of which shows the effective value of the oscilla tion set up across each of the reactances as a function of the polarization comprising at least one unstable region, the said polarization being varied by the signal oscillations so as to exceed this region.

The invention will now be described with reference to the accompanying diagrammatic drawings, in which Fig. 1 shows a diagrammatic embodiment of a circuit according to the invention of the magnetic type;

Fig. 2 shows a series of curves associated with such a circuit;

Fig. 3 is a curve illustrating the operation of a device according to the invention;

Figs. 4, 5 and 6 show diagrammatically embodiments ice of circuits according to the invention of the magnetic yp Figs. 7 and 8 show diagrammatically embodiments of circuits according to the invention of the dielectric type;

Fig. 9 is a curve illustrating one aspect of the operation of a device according to the invention;

Fig. 10 shows a circuit according to the invention of the magnetic type in which feed-back is provided;

Fig. 11 is a curve illustrating the operation of the circuit shown in Fig. 10;

Fig. 12 is a curve as obtained completely in such an arrangement;

Fig. i3 is a curve illustrating one aspect of the operation of device according to the invention;

Fig. 14 shows a circuit according to the invention of the dielectric type in which feedback is provided;

Fig. 15 shows by way of example an embodiment of a push-pull circuit of the magnetic type in which feedback is provided; 7

Fig. 16 shows by way of example a similar circuit of the dielectric type, and

l7 is a characteristic curve as may be obtained in a specific use of circuits according to the invention.

ferring now to Fig. l, K designates a ferromagnetic core the polarization curve of which, that is to say the curve showing the relationship between the magnetic induction B and the magnetic field strength H, has a nonlinear variation. L and W are windings arranged on said core, C is a capacitor which may be linear, G is a supply generator and R a resistor which is assumed to include the losses of the circuit such as the resistance of the supply generator G and of the coil L.

if for example the effective value Veil of the peak value of the alternating current voltage across one of the elements L, C, R or W which is set up under the action of the supply voltage E having a frequency f is considered as a function of the polarization which is rendered effective for example by means of a direct current I which is passed by W, the relationship between these quantities is found to be as shown in the series of curves shown in Fig. 2, subject to some conditions with regard to E, C and f, and this will be set out more fully hereinafter.

In the curve family shown in Fig. 2 the resistor R is taken as a parameter, R increasing with increasing ordinal number.

Let this resistor be small enough for curve 1 to represent the above mentioned relationship. Without adjustment polarization, that is to say at 1:0, Velf for example across the coil L is equal to-Vl after the supply voltage E is brought into the circuit. Gn introduction of the adjustment polarization, Veff initially increases continuously with increasing 1. On reaching point A of curve 1 Van leaps discontinuously from the value associated with A to V2 at point A along the broken line in the figure. On further increase of 1, Volt at least approximately retains this vaiue V2, falls off ultimately to the value associated with point B and then falls to value Vs at point B, as indicated in the figure by the broken line BB. Veff approximately conserves this value V3 with further increase of 1.

Van remains at this value on subsequent reduction of l, is ultimately increased to the value associated with point C and thence leaps along the broken line CC to the value V2 at point C, which value is maintained with decreasing I The curve is symmetrical with respect to the Veft axis. The broken lines indicate unstable con ditions the variation of which may be ascertained theoretically. The stable region in the proximity of the point 1:0, VefI VI is only re-accessible by switching off and subsequent switching on of the supply voltage E.

When the resistor R is reduced a curved is produced which has substantially the same variation as curve 1 but when R in increased, this variation is modified. Increasing R in a manner such that the curve 2 shown in Fig. 2 is obtained results in a discontinuous leap from a high voltage level to a low voltage level even at a smaller value of I. On further increase of R this un stable region disappears altogether at the lower value of I, as may be seen from the variation of curve 3 shown in Fig. 2. When R is further increased it ultimately has so strong a linearizing effect that discontinuities do not occur either at a low value or at a high value of I. The relationship between Veff and I in this event is indicated by curve 4 shown in Fig. 2.

If the VeI'f-I curves across one of the other elements, that is to say C, R or W are considered, these curves are found to exhibit a similar form, the numerical values of Veff, however, being different with each element.

As has been stated hereinbefore, not only the BH curve of the ferromagnetic core, but also the values of the capacity C, of the voltage E and the frequency f affect the value of Veff as a function of I, although the character of the curves is maintained within certain limits. However, the said quantities also affect these curves qualitatively. Thus, the instabilities are enabled to occur only if the product of the capacity C and the square of the frequency f satisfies the condition:

where Lmln designates the minimum value of the inductance of L, which occurs at a very high value of adjustment polarization, and Lmax the maximum value of the inductance of L, which occurs at a very low value of adjustment polarization.

The value of the supply voltage E is also influential. Reduction of E causes thecurve 1 to change to curves such as 2, 3 and 4.

If, in the case of the VetiI curve being formed in the shape of curve 1, the polarization is adjusted to 1:10, as shown in Fig. 3, the value of Veff is either V2 or Vs. Assuming this value to be V2, a current pulse applied to the winding W equal to or exceeding Ali and having the same polarity as Io will cause Veff to pass from the value V2 to V3.

Any subsequent similar pulse will not have the effect of changing the condition so that Veff will retain its value V3 at least approximately. However, if an impulse exceeding or equalling Alg and having a polarity opposite to Io follows, it will cause Veff to change from V3 to V2. Also in this case another similar pulse will not cause Veff to change from V2 to V3.

Thus, a train of pulses having alternately opposite polarity and the absolute value of. which is at least equal to Ali or A12 respectively (it being naturally possible for In to be such that AI1ZAI2) will cause Veff to pass from the value V2 to the value V3 and vice versa in the same rhythm, so long as the period of time between the successive pulses is sufficiently large to prevent any effect of the inertia attendant on the changes from one stable condition to the other. As will be shown below, this inertia may be used with advantage.

To obtain the above described effect use may be made of a characteristic curve as shown by curves 2 and 3, there being, in addition, in the case of curve 2 the choice between two unstable regions. So long as other considerations are not significant the region obtained with larger adjustment polarization is to be preferred, since in this event the saturation region of the B-H curve is operated upon, so that the hysteresis losses are kept small, which may be of great value at high repetition frequencies.

If two unstable regions are available, the pulses should not be large enough to cover both regions.

The output signal of the trigger circuit shown in Fig. 1, that is an alternating current voltage having a large or small amplitude according to whether the circuit is in miu one stable condition or in the other, may in principle be taken not only from any of the elements L, W, C and R but also from windings which magnetically are connected in parallel with L or W, that is to say, from wind ings supported from the core in a manner such that their turns embrace the same flux as the turns of L or W. Since the non-linearity of the circuit decreases with increase of R, resulting in less favourable characteristic curves such as curves 3 and 4 shown in Fig. 2, R will generally be kept to a minimum. In this case the output signal taken from R becomes comparatively small so that instead of being taken from R this signal is preferably taken from L or C. In addition, it is found both experimentally and theoretically, that when the output voltage is taken from the windings'L and W, or from tap on these windings or from windings connected magnetically in parallel therewith, the ratio is materially higher and hence is more favourable for many purposes than when the output voltage is taken from the capacitor C or from a resistor included in the circuit. In addition, with tap on L and W or with windings connected magnetically in parallel with L and W, proper proportioning of the number of turns permits stepping up or down the output voltage.

The output voltage of the circuit may be detected by means of an amplitude detector and, if required, subsequently'ditferentiated and so forth, according to the use to which it is to be put.

Hitherto adjustment polarization has been referred to,

' that is to say, a constant premagnetization of the ferroconstant adjustment polarization.

magnetic core which is effected with the aid of the direct current In which passes through the signal winding W. Naturally, as an alternative said premagnetization may be produced by means of a direct current passing through a winding connected magnetically in parallel with W or by means of a permanent magnet.

In addition, signal pulses have been continually referred to. It will be understood that any oscillation which is positive in relation to In and the amplitude of which exceeds All for a period of time is capable, when superposed on Io, of bringing about a change from V2 to V3 and that any oscillation which is negative in relation to lo and the amplitude of which exceeds Ala for a period of time is capable, when superposed on Io, of bringing about a change from V3 to V2. Pulses, which term is to be understood to mean oscillations having steep flanks, have the advantage that curvatures in the Veff-I0 curve, for example adjacent the points B and C of the curve 1 shown in Fig. 2, are traversed more rapidly, and hence that the transitions in the output voltage from V2 to V3 and vice versa are faster.

In addition, it should be noted that somewhat similar instabilities are produced in a circuit of the kind shown in Fig. l as a function of the supply voltage E at a This form of iustabilities has a limitation in that, if they are required to be used for a trigger effect, the supplyvoltage must be modulated by the signal oscillations to which the circuit is required to respond.

In a circuit arrangement as shown in Fig. 1 the supply oscillation produces fluxes in the ferromagnetic core which not only feed the required voltages into the coil L but also feed undesired voltages into the winding W and any windings connected magnetically in parallel there- I with. These voltages become unduly high in the case of high internal impedance of the direct current supply and the signal supply, and in the case of low internal impedance may produce in the said windings appreciable short-circuit currents which have an undue retarding effeet on the required sudden changes. The said shortcircuit currents may be balanced out by connecting chokes in series with the windings, but in this case the signal oscillations, particularly at a high repetition frequency thereof, are appreciably attenuated and also slightly retarded, while at the same time excessive voltages are apt to be set up.

These high voltages or powerful currents may be largely balanced out by preventing at least components at the frequency f and odd multiples thereof from being set up at the input end of the circuit arrangement. This may be ensured in a number of ways known per se with magnetic modulators, for example by the use of two push-pull connected devices in accordance with the invention one set of windings of which is connected in series and the other set in series opposition, as shown in Fig. 4, or by using a three-legged core having supply windings wound on its outer legs so as to produce an annular magnetic field for these legs (see Fig. 5), the centre leg having produced in it only fluxes the frequencies of which are even multiples of the supply frequency.

Instead of a supply generator having an impedance comprising a preferably minimum ohmic component being connected in series with a non-linear inductance and a capacity it may be connected in parallel with a nonlinear inductance and a capacity, as shown in Fig. 6, which results in a curve family similar to the one produced by the series connection except that now linearization is increased as the parallel impedance is decreased. Hence in this event use will preferably be made of a supply generator having a very high internal impedance.

imilar considerations apply to the circuit arrangements shown in Figs. 4 and 5. It should be noted that an impedance connected in series with the parallel combination of L and C, as shown by broken lines in Fig. 6, results in an additional degree of liberty with which for example Ali-{-AI2, that is the minimum pulse height allowing the change from one stable condition to the other, can be controlled. As an alternative this may be done by increasing or decreasing the capacitor C within the fixed limits but, in the case of a large value of C this requires comparatively large adjustment polarizations and this is not the case with control by means of Z.

Even a series circuit as shown in Figs. 1, 4 and 5 may otherwise have an additional degree of liberty introduced in it in that an impedance is connected in parallel with the suply generator G.

Hitherto we have restricted our discussion to the case in which the medium which is operated in a non-linear part of its polarization characteristic curve is ferromagnetic. However, it is also possible for the medium to be of dielectric nature.

In Fig. 7, M designates a dielectric material the polarization characteristic curve of which, that is the curve showing the relationship between the dielectric displacement D and the electric field strength F, is non-linear, C designates a capacitor containing this material, L an inductance which may be linear, G a supply generator and R a resistor which is considered to include the resistance of the supply generator G, the coil L, and so forth.

If for example the effective value Veft of the alternating current voltage set up across one of the elements L, C or R under the action of the supply voltage E at a frequency f is considered as a function of the polarization which is set up by means of a direct current voltage V applied across C, a relationship is found to exist between Veff and V which is similar to the relationship between Vetf and I in the circuit arrangement shown in.

Fig. 1.

Here again quantities such as L, E and f act upon the value of Verr as a function of V, and also qualitatively upon the variation of the curves. In this case it is pos sible for instabilities to be produced, only if the condition is satisfied, where Cmin represents the minimum value '6 of the capacity of C set up at a very low value of adjustment polarization and Cmax the maximum value of the capacity of C resulting at a very high value of adjustment polarization.

Thus, a proper choice of the adjustment alternating current voltage V0 enables the effective value of the alternating current voltage across the said elements to be changed, in a similar manner as described above for the magnetic circuits, by means of voltage pulses of suitable value and direction, to assume a high or a low value. Here again taking the output voltage from L or a winding coupled magnetically thereto is more advantageous for the ratio It V3 than when the output alternating current voltage is taken from one of the elements C and R.

The undesired voltage phenomena which, with the magnetic type, occur in the case of a simple core, also occur with the dielectric type, if this comprises a single capacitor. This may be obviated in a manner known per se similar to that used in the case of the magnetic type. Fig. 8 shows an embodiment of such a push-pull dielectric trigger circuit, G designating a supply generator, V0 a direct current voltage source, T a signal oscillation voltage source, C and C2 similar non-linear capacitors, Li and L2 similar inductance coils and S1, S2 and S3 blocking transformers. The supply generator oscillations are connected to the non-linear elements in push-pull, and the signal oscillation is connected to these elements in co-phase.

he required output voltages may be taken across the pairs of terminals a-b, cd and e-g, the Voltages across the pairs of terminals a--b and cd comprising only components the frequencies of which are odd multiples of the supply frequency and the voltages across the pair of terminals e-g comprising only components the frequencies of which are even multiples of the supply frequency.

Trigger circuits of the magnetic or dielectric type as hereinbefore described are capable of replacing other known trigger circuits in many cases.

in some uses the pulse train to which the trigger is required to respond is such that all the pulses are of the same polarity.

It is possible for the trigger circuit arrangement according to the invention to be adapted to this last-named kind of pulse trains by converting such a pulse train in a manner known per se into a pulse train which in its action is equivalent to a pulse train the pulses of which are alternately positive and negative, the conversion being effected by extending the input circuit to become an aperiodically damped resonant circuit the resonant frequency of which should materially exceed the impulse repetition frequency. Such a circuit converts each impulse into an oscillation which at the end of a period is damped and hence consists of two closely adjacent pulses of opposite polarity. in Fig. 9 such pairs of pulses, viz. l-Z and 34 are shown superposed on the adjusting polarization 10 or V0.

Supposing the trigger circuit to be in the condition A, impulse 1 does not act upon Verr, but impulse 2 causes Veff to pass the condition B. Impulse 3 causes a change of Vaff from the condition B to the condition A. However, due to the inertia of the circuit, impulse 4, which closely follows impulse 3, is now not capable of interfering with this change. On the other hand, the inertia of the circuit should not be such as to prevent impulse 3 from effecting a change after the action of impulse 2. Hence, the inertia of the circuit arrangement is thus efficiently used.

It has been stated hereinbefore that the value of AI1+AI2, which value is a measure of the minimumsignal amplitude required to cause a change from one stable condition to the other, may be adjusted by means of an impedance included in the circuit connecting the supply generator to the said reactances, as is shown for example in Fig. 6.

Fig. 10 shows a circuit in which the value Ah-I-AIz is controlled in a different manner, in that the oscillation set up across one of the reactances or across an impedance coupled to the said reactances is rectified and then supplied to the variable reactance or in other words feed-back is provided. This circuit, which is substantially equal to the circuit arrangement shown in Fig. l and like elements of which are designated correspondingly, comprises a winding T which is closed through a rectifier cell RF and a resistor RT. The voltage fed into T produces a pulsatory direct current in this cii= cuit which may be smoothed, if required, the direct current component It of which in the stable condition is equal either to aV2 or to V3, and the direction of which is determined by RF, at being controllable by means of RT. According to the direction of the flux produced by this direct current the action of In is counteracted or assisted. It is found that, if the direction of the direct flux set set up by the circuit T, RF, RT is equal to the direction of the flux set up by In, the value AI1+AI2 decreases but that in this event the transitions caused by Ali and M2 are retarded relatively to the initial transition speed and that, if the direction of the direct flux set up by the circuit T, RF, RT is opposite to the direction of the flux set up by Io, the value AI1+AI2 increases, but that in this event the transitions caused by All and AI2 are accelerated relatively to the initial transition speed. This may be appreciated from consideration of Fig. 11. In this figure the curve of Fig. 3 is again shown, In being the adjusting polarization and A11 and A12 the minimum impulse amplitude required if no feed-back is used. Assume now that the feed-back current counteracts the adjusting polarization and this adjusting polarization is made I00. If the circuit arrangement is in the condition in which the effective value V eff is equal to V3, the direct current It=ltl produced in the circuit T, RF, RT is comparatively small. In this event the resultant adjusting polarization is I1. To effect a transition from V3 to V2 the minimum impulse amplitude required is I1IS1=AI2 and this may substantially exceed A12. However, this transition will also occur more rapidly than if no feed-back is provided, since during the transition from V3 to V2 Veff continuously increases, and hence also It from In to Ith, a value of It to which corresponds that condition in which Veff=V2. The change in It, acts as it were in support of the transition started by the impulse.

In the condition in which Veff=V2 the resultant adjusting polarization I2 is equal to IIth. Transition to the condition in which Veff=V3 now requires an impulse I82 'I2=AI1' AIL As this transition It. is decreased by Veff and thus also acts in support of the transition started by the impulse and this in turn results in the transition from one stable condition to the other being accelerated relatively to the transition without negative feed-back.

In addition, when this negative feedback is provided the ratio is found to increase. This is due to the fact that at 1:10 in one condition Veft' has not yet quite reached the value V2 due to the curvature in the unstable region, and likewise in the other condition the value V3 is not yet quite reached. If comparatively V3 is much smaller than V2 the said ratio may be materially increased under the influence of a comparatively low decrease in V3.

By plotting A11 and A12 from I00 in the correct direc- 8 tion and at the correct level, the level being determined by the points ott a new curve is found showing Veff as a function of the current passed by the winding W, if negative feed-back is provided. Fig. 12 shows this curve including the part which initially was symmetrical in relation to the Vet! axis. In this left hand part the negative feed-back has changed to positive feed-back. As may be seen from the figure, in the case of positive feed-back the sum of the minimum impulse amplitudes AI1+AI2 required for the transitions is materially smaller at an adjusting polarization I00 than without providing positive feedback. In a manner similar to that used in the case of negative feed-back it may be proved that in the case is decreased. The figure shows in addition a part designated 1.

If a high degree of negative feed-back is provided, the curve shown in Fig. 12 assumes the shape shown in Fig. 13. In this figure Vetf is again shown as a function of the current passed by the winding W. Adjusting I to the value In indicated in the figure ensures three stable conditions. Assume the circuit arrangement to be in the condition in which Veff: V2, that is to say at point I. If the impulse designated 1 in the figure is superposed on Io, Veff leaps from A to a point B and moves to a point C by way of the branch of the characteristic curve associated with point B. This transition is assisted by the feed-back and consequently accelerated. A subsequent impulse of opposite direction designated 2 in the figure causes Veff to pass from C to D by way of the characteristic curve; thence a discontinuous transition is effected to point E. This transition is retarded, since the negative feed-back current which increases with Van counteracts the impulse 2; hence the final condition is characterized by the point F and not by the point I which would be reached through G and H, unless the impulse 2 is made sufliciently high and wide for the impulse to remain active after the transition has occurred even in spite of the retardation. The point I, the starting point in this discussion is not reached until after the application of a third pulse designated 3 in the figure. In this case the transition from G to H is accelerated. An impulse 4 initiates a new cycle.

Extension of the input circuit of the trigger circuit arrangement to become an aperiodic resonant circuit the resonant frequency of which materially exceeds the impulse repetition frequency, permits of causing these trigger circuits comprising three stable conditions to respond to a train of impulses all of which are of the same polarity.

If negative feed-back is used to accelerate the transitions, thus permitting the use of higher impulse repetition frequencies, the resultant higher value of Aha-A12, by which the minimum impulse amplitude required is determined, may be decreased by means of an impedance included in the circuit connecting the supply generator to the two reactances, such as the .impedance Z shown in broken lines in Fig. 10. Conversely, when positive feedback is provided, so that Alr-j-Aiz is decreased, the use of an impedance permits of increasing this value.

Such feed-backs may also be provided in dielectric circuit arrangements, since the Veff-V characteristic curve is similar. In Fig. 14- M designates a dielectric material the polarization characteristic curve of which, that is the characteristic curve showing the relationship between the dielectric displacement D and the electric field strength F, has a nonlinear variation, C a capacitor comprising this material, G a supply generator which for example is caused tobccome operative through a separating transformer S which is included in the circuit comprising C, S2 a second separating transformer the inductance of the primary winding of which together with the inductance of the winding of S1 included in the circuit consttiutes the reactance of the opposite polarity and one of the secondary windings of which together with a rectifier RF, a capacitor C1 and a resistor R constitutes the negative feedback circuit, V is a unidirectional voltage source, and T is an impulse voltage source. The required output voltages which are still alternating current voltages may be taken from a further secondary winding of S2. The capacitor C1 through which the negative feed-back voltage is introduced into the circuit also acts as a smoothing capacitor and is preferably arranged to have a large value. The detected voltages may be taken from across R.

Obviously it is also possible to provide feed-back in push-pull trigger circuits as described with reference to Figs. 4, 5 and 8. Fig. shows by way of example such a magnetic trigger circuit and Fig. 16 a dielectric one. In these circuits the even harmonic oscillations are utilized for the feed-back. it will be understood that the odd harmonics may also be used for this purpose, but this is not advisable, since in some cases the push-pull may be upset.

Trigger circuits in accordance with the invention may be used advantageously as impulse renovators and amplifiers for pulsatory signals, the impulse shape, which in most cases has been materially affected during the transmission from transmitter to receiver, which usually shows itself as a decrease in steepness of the pulse flanks, being thus recovered.

To appreciate this a circuit arrangement as shown in Fig. 1 should be considered. In addition, it is assumed that the half-value duration of the transmitted impulses is equal to the duration of the initially emitted impulses and that the decrease in steepness of leading and trailing edges is identical which is usually likely to be approxi mately the case in practice. Assuming the height of the pulses reaching the amplifier to be h it will be obvious with the aid of Fig. 17 that, if the pulses are superimposed on an adjusting polarization I1 in a manner such that Ii+ /2h=Io, the duration 11 of the initial impulse the shape of which is shown in the figure by a broken line persists in the voltage which at the output i available as a modulated pulse. In this case Ali is assumed to be equal to Al, (Fig. 3), since, if actually on, is equal to (1 as has been assumed, the period of time t1t1 and t2tz are also identical, where ii is the instant at which the original impulse started and t2 the instant at which it ended, ti being the instant at which the impulse reaching the amplifier causes transition from V2 to V and t2 the instant at which this impulse causes transition from V3 to V2. If All is not equal to A12, a slightly different choice of the adjusting polarization leads to the same result.

Detection of the output signal of a trigger circuit used in this manner thus produces a signal which is amplified and restored in shape but which is retarded relatively to the initial signal by a period of time ti'-tr.

if It varies in the course of time provision may be made for the relation Ii+ /2h1=o to be satisfied by causing I to be decreased by the sameamount by which /211 is increased.

What is claimed is:

l. A trigger circuit comprising a non-linear variable first reactance, a second reactance of opposite polarity coupled to said first reactance, a source of local oscillations, means connected to supply said local oscillations to said reactances, said first reactance being polarizable in stable and unstable regions, means connected to polarize said first reactance into an unstable region wherein the oscillation in said reactances may assume any one of a plurality of difierent magnitudes, a source of signal oscillations having a frequency which is low as compared with the frequency of said local oscillations, and means connecting said signal oscillations to said first reactance, said signal oscillations having a magnitude sufficiently great to shift said polarization momentarily into a stable region of said first reactance whereby the oscillation in said reactances is shifted from one to another of said different magnitudes.

2. A trigger circuit, as set forth in claim 1, wherein said first reactance comprises magnetic material.

3. A trigger circuit, as set forth in claim 1, wherein said first reactance comprises dielectric material.

4. A trigger circuit, as set forth in claim 1, further including an impedance connecting said local oscillation source to said reactances, means for adjusting the value of said impedance to cause adjustment of the minimum signal oscillation amplitude at which said shifting of the oscillation occurs.

5. A trigger circuit comprising a non-linear variable first reactance, a second reactance of opposite polarity coupled to said first reactance, a source of local oscillations, means connected to supply said local oscillations to said reactances, said first reactance being polarizable in stable and unstable regions, polarization means connected to polarize said first reactance into an unstable region wherein the oscillation in said reactances may assume any one of a plurality of different magnitudes, a source of pulsatory signal oscillations having a pulse repetition rate which is low as compared with the frequency of said local oscillations, means connecting said signal oscillations to said first reactance, said signal oscillations having a magnitude sufficiently great to shift said polarization momentarily into a stable region of said first reactance whereby the oscillation in said reactance is shifted from one to another of said different magnitudes, rectifying means connected to rectify the oscillations across one of said reactances and produce rectified oscillations therefrom, and means connected to supply said rectified oscillations to said first reactance.

6. A trigger circuit as claimed in claim 5, including means connected to adjust the magnitude of said rectified oscillations to a valu whereby said circuit is capable of respectively assuming three different stable regions at different values of polarization produced by said polarization means.

7. A trigger circuit as claimed in claim 5, in which said first reactance comprises two sections connected in push-pull with respect to said local oscillations and connected in co-phase with respect to said signal oscillations.

8. A trigger circuit comprising a variable reactance having a medium which is operable in a non-linear part of its polarization characteristic curve, means connected to polarize said medium in said non-linear part, said reactance being constituted by an inductor having a ferromagnetic core, a source of pulsatory oscillations, a coil magnetically coupled to said ferromagnetic core and connected to said source for supplying pulsatory oscillations to said reactance, a source of local oscillation, said local oscillation having a frequency which is high as compared with the rate of said pulsatory oscillations, a capacitor and a load resistor, said source, said capacitor and said resistor being serially connected across said reactance.

9. A trigger circuit comprising a variable reactance having a medium which is operable in a non-linear part of its polarization characteristic curve, said reactance being constituted by an inductor including a first coil having a first ferromagnetic core and a second coil having a second ferromagnetic core, said coils being connected in series opposition, a third coil magnetically coupled to said first coil, a fourth coil magnetically coupled to said second coil, said third and fourth coils being connected in series aiding a source of pulsatory oscillations connected across said third and fourth coils for supplying pulsatory oscillations to said reactance, a source of local oscillation, said local oscillation having a frequency which is high as compared with the rate of said pulsatory oscillations, a capacitor and a load resistor, said local oscillation source, said capacitor and said resistor being serially connected across said first and second coils.

10. A trigger circuit comprising a variable reactance having a medium which is operable in a non-linear part of its polarization characteristic curve, said reactance being constituted by an inductor including a first coil, 21 second coil serially connected to said first coil and a three-legged ferromagnetic core having two outer legs and a central leg, said first coil being wound around one of said outer legs and said second coil being wound around the other of said two outer legs, a third coil wound around said central leg, a source of pulsatory oscillations connected to said third coil for supplying pulsatory oscillations to said reactance, a source of local oscillation, said local oscillation having a frequency which is high as compared with the rate of said pulsatory oscillations, a capacitor and a load resistor, said local oscillation source, said capacitor and said resistor being serially connected across said first and second coils.

11. A trigger circuit comprising a variable reactance having a medium which is operable in a non-linear part of its polarization characteristic curve, said reactance being constituted by an inductor having a ferromagnetic core, a coil magnetically coupled to said ferromagnetic core, a source of pulsatory oscillations connected to said coil for supplying pulsatory oscillations to said reactance, a capacitor connected across said inductor, a source of local oscillation, said local oscillation having a frequency which is high as compared with the rate of said pulsatory oscillations, and an impedance connected in series with said local oscillation source, said impedance and said local oscillation source being connected across said capacitor.

12. A trigger circuit comprising a variable reactance having a medium which is operable in a non-linear part of its polarization characteristic curve, said reactance being constituted by a capacitor containing a dielectric material, means for supplying pulsatory oscillations to said reactance, a source of local oscillations, said local oscillations having a frequency which is high as compared with the rate of said pulsatory oscillations, an inductance and a load resistor, said source, said inductance and said resistor being serially connected across said reactance.

13. A trig er circuit comprising a pair of variable reactances each having a medium which is operable in a non-Ir car part of its polarization characteristic curve, each of said reactances being constituted by a capacitor containing a dielectric material, a first transformer having a primary winding and a secondary winding having a tap thereon, a second transformer having a primary winding having a tap thereon and a secondary winding, one end of the secondary winding of said first transformer being connected to one end of the primary winding of said second transformer through one of said reactances, the other end of the secondary winding of said first transformer being connected to the other end of the primary winding of said second transformer through th other of said pair of reactances, a direct current source, a signal oscillation source, a third transformer 1 ing a primary winding and a secondary winding, said sources and the primary winding of said third transformer being serially connected between said taps, and a source of local oscillation connected across the primary winding of said first transformer, said local oscillation having a frequency which is high as compared with the frequency of said signal oscillation, whereby the secondary winding of said second transformer has an output voltage comprising only components the frequencies of which ar odd multiples of the frequency of the local oscillation and the secondary winding of said third transformer has an output voltage comprising only components the frequencies of which are even multiples of the frequency of the local oscillations.

14. A trigger circuit comprising a variable reactance having a medium which is operable in a non-linear part of its polarization characteristic curve, said reactance being constituted by an inductor having a ferromagnetic core, a first coil magnetically coupled to said ferromagetic core, a source of pulsatory oscillations connected to said first coil for supplying pulsatory oscillations to said reactance, a second coil magnetically coupled to said ferromagnetic core, a rectifier and a variable resistor connected in series across said second coil, an impedance connected across said inductor, a source of local oscillation, said local oscillation having a frequency which is high as compared with the rate of the pulsatory oscillations, a capacitor and a load resistor, said local oscillation source, said capacitor and said load resistor being serially connected across said inductor.

15. A trigger circuit comprising a variable reactance having a medium which is operable in a non-linear part of its polarization characteristic curve, said reactance being constituted by a capacitor containing a dielectric material, a first transformer having a primary winding and a secondary winding, a second transformer having a first winding, a second winding and a third winding for providing an output voltage, a coupling capacitor, a signal oscillation source, a direct current source, said variable reactance, said coupling capacitor, said first winding and said sources being serially connected across the secondary winding of said first transformer, a source of local oscillation connected across the primary winding of said first transformer, said local oscillation having a frequency which is high as compared with the frequency of said signal oscillations, a resistor connected across said coupling capacitor, and a rectifier connected in series with said second winding across said resistor.

16. A trigger circuit comprising a variable reactance having a medium which is operable in a non-linear part of its polarization characteristic curve, said reactance being constituted by an inductor including a first coil, a second coil serially connected to said first coil and a three-legged ferro-magnetic core having two outer legs and a central leg, said first coil being wound around one of said outer legs and said second coil being wound around the other of said two outer legs, a third coil wound around said central leg, a source of pulsatory oscillations connected to said third coil for supplying pulsatory oscillations to said reactance, a source of local oscillation, said local oscillation having a frequency which is high as compared with the rate of said pulsatory oscillations, a capacitor, a first resistor, said local oscillation source, said capacitor and said resistor being serially connected across said reactance, a fourth coil wound around the central limb of said core, a rectifier and a second resistor serially connected to said rectifier across said fourth coil.

17. A trigger circuit comprising a pair of variable reactances each having a medium which is operable in a non-linear part of its polarization characteristic curve, each of said reactances being constituted by a capacitor containing a dielectric material, a first transformer having a primary winding and a secondary winding having a tap thereon, a second transformer having a primary winding having a tap thereon and a secondary winding, one end of the secondary winding of said first transformer being connected to one end of the primary winding of said second transformer through one of said reactances, the other end of the secondary winding of said first transformer being connected to the other end of the primary winding of said second transformer through the other of said pair of reactances, a direct current source, a pulsatory oscillation source, a coupling capacitor, a third transformer having a first Winding, a second winding and a third winding, said sources, said coupling capacitor and said first winding being serially connected between said taps, a source of local oscillation connected across the primary winding of said first transformer, said local oscillation having a frequency which is high as compared with the frequency of said pulsatory oscillations, a resistor connected across said coupling capacitor, and a rectifier connected serially with the second winding of said third transformer across said resistor, whereby the secondary Winding of said second trans- 14 former has an output voltage comprising only components the frequencies of which are odd multiples of the frequency of the local oscillation and the third winding of said third transformer has an output voltage comprising only components the frequencies of which are even multiples of the frequency of the local oscillation.

References Cited in the file of this patent UNITED STATES PATENTS 2,653,254 Spitzer et al. Sept. 22, 1953

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