METHOD FOR PACKAGING A MICROWAVE TUBE MODULATOR

Abstract: A method for packaging components in the primary circuit of a microwave tube modulator (10) output transformer. Modules are assembled using parallel plates (12, 14, 16) upon and around which transistors and other necessary components are mounted. In addition to providing mechanical support for the components, the plates act as conductors for circuits common to respective elements of paralleled transistors, thereby minimizing electrical resistance and inductance in the primary circuit. The modules are designed to mount to the output transformer such that two of the parallel plates are mechanically connected to the respective two ends of the transformer primary, and a number of modules can be mounted around and to one transformer according to the amount of energy required.

Description: This invention relates to the packaging of modulators used to provide high-voltage pulses to microwave transmitter tube output transformers. A number of devices have been designed to provide pulses for use in microwave modulation applications. Some of these use field-effect transistors (FET's) connected in parallel to provide the necessary energy to drive a microwave tube modulator output transformer, but such configurations do not minimize electrical resistance and inductance in the primary circuits of the associated output transformers and require modifications to increment their energy-providing capacities. See, for example, U.S. Patent Numbers 3,374,406; 3,374,407; 3,426,255; 3,509,567; 3,525,861; 3,544,399; 3,562,672; 3,582,975; 3,828,324; 3,914,555; 3,967,217; 3,995,178; 4,010,450; 4,071,777; 4,095,251; 4,143,387; 4,221,044; 4,235,010; 4,247,903; 4,262,296; 4,304,042; 4,328,470; 4,409,594; 4,425,527; 4,662,058; 4,679,050; 4,679,299; 4,683,287; and 4,689,802. In accordance with this invention there is provided a method for packaging into an effective module power transistors in the primary winding circuit of a microwave tube modulator output transformer to minimize electrical resistance and inductance in the primary winding circuit, the method being characterised by connecting a first plate to a first end of the microwave tube modulator output transformer primary winding, said first plate being arranged for connection to a source of positive voltage; mounting a second plate in spaced apposition to said first plate, said second plate being arranged for connection to ground; mounting a third plate in progressively spaced apposition to said first plate and said second plate, and connecting said third plate to a second end of the output transformer primary winding; and mounting a plurality of output transformer primary winding circuit power transistors on said third plate at minimum practical distances from the second end of the output transformer primary winding and connecting a first terminal of each of said power transistors to said third plate and therefore effectively to the second end of the output transformer primary winding, said first plate providing a low-resistance path for current flow between the output transformer primary winding and the source of positive voltage and said third plate providing a low-resistance path for current flow between said first terminals of the power transistors and the output transformer primary winding, said first and said third plates also minimizing inductance in the output transformer primary winding circuit. Also in accordance with this invention there is provided a microwave tube modulator having an effective disposition of power transistors in the primary winding circuit of a microwave tube modulator output transformer to minimize electrical resistance and inductance in the primary winding circuit, characterised in that the modulator comprises: a first plate connected to a first end of the microwave tube modulator output transformer primary winding and being arranged for connection to a source of positive voltage; a second plate disposed in spaced apposition to said first plate and being arranged for connection to ground; a third plate disposed in progressively spaced apposition to said first plate and said second plate, said third plate being connected to a second end out the output transformer primary winding; and a plurality of output transformer primary winding circuit power transistors mounted on said third plate at minimum practical distances from the second end of the output transformer primary winding with a first terminal of each of said power transistors connected to said third plate and therefor effectively connected to the second end of the output transformer primary winding, said first plate providing a low-resistance path for current flow between the output transformer primary winding and the source of positive voltage and said third plate providing a low-resistance path for current flow between said first terminal of the power transistors and the output transformer primary winding, said first and said third plates also minimizing inductance in the output transformer primary winding circuit. In an embodiment to be described herein, the present invention provides a modulator comprising elements in a combination and configuration that simultaneously minimizes the electrical resistance and inductance in the primary circuit of its associated microwave tube modulator output transformer and facilitates the combining of modulator units to supply incrementally increased amounts of energy to the output transformer. The embodiment to be described herein provides a modulator which is capable of supplying high-voltage pulses having short rise and fall times to the primary windings of appropriately selected transformers connected to a large number of different microwave transmitter tubes such as magnetrons, pulse cavity oscillators, cross field amplifiers and travelling wave tubes. The preferred embodiment of the present invention contemplates a modulator having a plurality of plates used to mount components such as transistors and transformers such that the critical distances between the components are minimized, thereby contributing to the minimization of electrical resistance and inductance in associated circuitry. The preferred embodiment of modulator has a plurality of plates used to mount components such that the plates act as electrical conductors between common elements of the components to additionally contribute to the minimization of electrical resistance and inductance in associated circuitry. The preferred embodiment of modulator has a configuration enabling it to be combined with like modulators to provide incrementally greater amounts of energy. The preferred embodiment of modulator can, by combining an appropriate number of modulator units and using appropriate output transformers, be matched to a large number of microwave transmitter tubes. The preferred embodiment of modulator is relatively small and relatively easy to produce and maintain. The preferred embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings, in which like reference characters indicate corresponding parts in all the figures and in which: FIG. 1 is a perspective view of four microwave tube modulator units connected to a microwave tube output transformer and embodying features of the invention; FIG. 2 is a perspective view showing the opposite side of one of the units of FIG. 1. FIG. 3 is a side view, partly broken away, taken along the line 3-3 of FIG. 2; and FIG 4 is a rear view of one of the plates of the modulator. Essentially, the microwave tube modulator is assembled on and between three main plates and two smaller plates. The plates serve as mounts for the components and also as low-resistance electrical conductors between common elements thereof. The plates and components are arranged to minimize the distances between the components in the primary circuit of an associated output transformer, thereby minimizing electrical resistance and inductance, and also to facilitate the combining of a number of modulator units to provide incrementally increased energy to drive one output transformer. With reference to FIG. 1, shown is a perspective view of four microwave tube modulator units, generally indicated by reference characters 10. Each modulator unit 10 has a first plate 12, a second plate 14 in spaced apposition thereto, and a third plate 16 in progressively spaced apposition to the first plate 12 and the second plate 14. The plates 12, 14, and 16 are electrically isolated from each other. FIG. 2 is a perspective view from the opposite direction of one of the modulator units 10, and FIG. 3 is a side view taken along the line 3-3 of FIG. 2. An associated output transformer 18 is shown in FIG. 3. The first plate 12 is secured to the first end 20 of the primary of the transformer 18 with screws 22, and the third plate 16 is secured to the second end 24 of the primary of the transformer 18 with screws 26. The second plate 14 is secured to the third plate 16 by posts 28 but is electrically isolated from the second plate 14 and the second end 24 of the transformer primary. Connected to and extending between the first plate 12 and the second plate 14 are a number of primary current storage capacitors 30. The first and second plates 12 and 14 serve as mounts for the capacitors 30 and also as low-resistance electrical conductors therefor, the first plate 12 being connected to a source of positive voltage and the second plate 14 being connected to ground. Mounted on the third plate 16 are a plurality of power transistors 32, which may be field-effect-transistors (FET's). The transistors 32 are connected in parallel, and the drain terminal of each is connected to the third plate 16. The transistors 32 are connected in a common gate configuration to minimize the effects of drain-to-gate capacitance and thereby increase the transistor switching speed. The plate 16 serves both as a mount for the transistors 32 and as a low-resistance electrical conductor between the drain terminals of the transistors 32 and the second end 24 of the primary of the output transformer 18. As can be seen in FIG. 2, the transistors 32 are arranged in close mutual proximity to minimize the distances between connections to their respective terminals. Mounted to the second plate 14 are a plurality of driver transistors 42, which may be field-effect-transistors. The driver transistors 42 are connected in parallel, and the source terminal of each is connected through fuse resistors (not shown) to the second plate 14. The plate 14 serves both as a mount for the transistors 42 and as a low-resistance electrical conductor between the source terminal fuse resistors and ground. The drain terminals of the driver transistors 42 are connected to a first end of the primary winding of a coupling transformer 38 mounted centrally to the second plate 14. The second end of the primary winding of the coupling transformer 38 is connected to a source of positive voltage. The gate terminals of the driver transistors 42 are connected through resistors to a first end of a feedback winding of the coupling transformer 38, and the second end of the feedback winding is connected to ground. The driver transistors 42 and associated resistors form a driver circuit that amplifies incoming signals before they are introduced to the primary circuit of the output transformer 18 through the coupling transformer 38. FIG. 4 is a view of the surface of the third plate 16 that faces the second plate 14 . As shown in FIG's. 3 and 4, a fourth plate 34 is mounted proximate the third plate 16 but is electrically isolated and separated therefrom by an insulator 36. The fourth plate 34 is connected through fuse resistors (shown only representatively in FIG. 3 ) to the source terminal of each transistor 32 and serves as a low-resistance conductor between the source fuse resistors and one end of the output winding of a transformer 38 coupling a driver amplifier to the primary circuit of the modulator 10. A fifth plate 40 is mounted proximate the third plate 16 but is also electrically isolated and separated therefrom by insulator 36. The fifth plate 40 is connected through parasitic-oscillation-limiting resistors (shown only representatively in FIG. 3 ) to the gate terminal of each transistor 32 and serves as a low-resistance conductor between the gate resistors and ground. In the embodiment of the invention shown in FIG's. 1 and 3, up to four modulator units 10 may be secured to one output transformer 18 to provide four incremental levels of electrical energy. The first plate 12 of each modulator 10 may be secured to the first end 20 of the primary of the transformer 18, using screws 22, and the third plate 16 of each modulator 10 may be secured to the second end 24 of the primary of the transformer 18, using screws 26. Such a configuration brings the components in the primary circuit of the transformer 18 into close proximity with each other and with the contacting ends 20 and 24 of the primary of the output transformer 18, thus keeping the current paths short and the attending resistance and inductance at a minimum. To reduce the possibility of injury from electric shock in applications where there is a likelihood that personnel may have to work in the proximity of an exposed modulator assembly, the plates may be arranged so that the innermost plate is the one connected to a voltage source and the outermost plate is grounded.

Claims: A method for packaging into an effective module power transistors (32) in the primary winding circuit of a microwave tube modulator output transformer (18) to minimize electrical resistance and inductance in the primary winding circuit, the method being characterised by connecting a first plate (12) to a first end (20) of the microwave tube modulator output transformer primary winding, said first plate (12) being arranged for connection to a source of positive voltage; mounting a second plate (14) in spaced apposition to said first plate (12), said second plate (14) being arranged for connection to ground; mounting a third plate (16) in progressively spaced apposition to said first plate (12) and said second plate (14), and connecting said third plate (16) to a second end (24) of the output transformer primary winding; and mounting a plurality of output transformer primary winding circuit power transistors (32) on said third plate (16) at minimum practical distances from the second end (24) of the output transformer primary winding and connecting a first terminal of each of said power transistors (32) to said third plate (16) and therefore effectively to the second end (24) of the output transformer primary winding, said first plate (12) providing a low-resistance path for current flow between the output transformer primary winding and the source of positive voltage and said third plate (16) providing a low-resistance path for current flow between said first terminals of the power transistors (32) and the output transformer primary winding, said first and said third plates (12 and 16 respectively) also minimizing inductance in the output transformer primary winding circuit. A method according to claim 1, characterised by the step of connecting said power transistors (32) in parallel. A method according to claim 1 or 2, characterised by the step of mounting to said second plate (14) a coupling transformer (38) having a primary, a feedback and a secondary winding, said primary winding having a first end and a second end, said feedback winding having a common end for connection to ground, and an output end, and said secondary winding having a common end for connection to ground, and an output end. A method according to claim 3, characterised in that the second end of the primary winding of said coupling transformer (38) is arranged for connection to the source of positive voltage. A method according to claim 3 or 4, characterised in that said coupling transformer (38) is mounted central to said second plate (14) and between said second plate (14) and said third plate (16). A method according to any preceding claim, characterised by the step of mounting a fourth plate (34) in spaced apposition to and electrically isolated from said third plate (16), and connecting said fourth plate (34) through respective fuse resistors to a second terminal of each of each said power transistors (32). A method according to claim 6, characterised by the step of connecting said fourth plate (34) to the output end of the secondary winding of said coupling transformer (38). A method according the claim 6 or 7, characterised by the step of mounting a fifth plate (40) in spaced apposition to said third plate (16) and electrically isolated from said third plate (16) and said fourth plate (34), and connecting said fifth plate (40) through respective parasitic limiting resistors to the third terminals of said power transistors (32). A method according to claim 8, characterised in that said fifth plate (40) is arranged for connection to ground. A method according to any preceding claim, characterised by the step of connecting a plurality of capacitors (30) between said first plate (12) and said second plate (14) such that the connections provide both electrical continuity and mechanical support for said capacitors (30). A method according to any preceding claim, characterised by the step of mounting a plurality of driver transistors (42) to said second plate (14). A method according to claim 11, characterised in that said driver transistors (42) are connected in parallel. A method according to claim 11 or 12, characterised in that said driver transistors (42) are field-effect transistors. A method according to claim 13, characterised by the step of connecting said driver transistors (42) in a common source configuration, the source terminal of each of said driver transistors (42) being connected through a respective fuse resistor to said second plate (14) and therefore in use effectively connected to ground. A method according to claim 13 or 14, characterised by the step of connecting the drain terminals of said field effect driver transistors (42) to the first end of the primary winding of said coupling transformer (38). A method according to any of claims 13 to 15, characterised by the step of connecting the output end of the feedback winding of said coupling transformer (38) through respective resistors to the gate terminals of said field effect driver transistors (42), said gate terminals being connected to other respective resistors which are arranged for connection to an input signal source. A method according to any preceding claim, characterised in that said power transistors (32) are field-effect transistors, and in that said first terminals are the drain terminals of said field-effect transistors. A method according to claim 17, characterised by the step of connecting said field effect transistors (32) in a common gate configuration to minimize the effects of drain-to-gate capacitance and thereby increase the switching speed of said transistors, the drain terminal of each of said power transistors being connected to said third plate (16) and therefore effectively connected to the second end (24) of the output transformer primary winding. A method according to any preceding claim, characterised by the step of connecting a plurality of modules (10) to a single microwave tube modulator output transformer (18) to increase the electrical energy available for the operation thereof. A microwave tube modulator (10) having an effective disposition of power transistors (32) in the primary winding circuit of a microwave tube modulator output transformer (18) to minimize electrical resistance and inductance in the primary winding circuit, characterised in that the modulator (10) comprises: a first plate (12) connected to a first end (20) of the microwave tube modulator output transformer primary winding and being arranged for connection to a source of positive voltage; a second plate (14) disposed in spaced apposition to said first plate (12) and being arranged for connection to ground; a third plate (16) disposed in progressively spaced apposition to said first plate (12) and said second plate (14), said third plate (16) being connected to a second end (24) of the output transformer primary winding; and a plurality of output transformer primary winding circuit power transistors (32) mounted on said third plate (16) at minimum practical distances from the second end (24) of the output transformer primary winding with a first terminal of each of said power transistors (32) connected to said third plate (16) and therefor effectively connected to the second end (24) of the output transformer primary winding, said first plate (12) providing a low-resistance path for current flow between the output transformer primary winding and the source of positive voltage and said third plate (16) providing a low-resistance path for current flow between said first terminals of the power transistors (32) and the output transformer primary winding, said first and said third plates (12 and 16) also minimizing inductance in the output transformer primary winding circuit. A modulator according to claim 20, characterised in that said power transistors (32) are connected in parallel. A modulator according to claim 20 or 21, characterised in that a coupling transformer (38) is mounted to said second plate (14), said coupling transformer (38) having a primary, a feedback and a secondary winding, said primary winding having a first end and a second end, said feedback winding having a common end and an output end, the common end being arranged for connection to ground, said secondary winding having a common end and an output end, the common end being arranged for connection to ground. A modulator according to claim 22, characterised in that said coupling transformer (38) is mounted central to said second plate (14) and between said second plate (32) and said third plate (16). A modulator according to claim 22 or 23, characterised in that the second end of the primary winding of said coupling transformer (38) is arranged for connection to the source of positive voltage. A modulator according to any of claims 20 to 24, characterised in that a fourth plate (34) is disposed in spaced apposition to and electrically isolated from said third plate (16), said fourth plate (34) being connected through respective fuse resistors to the second terminal of each of said power transistors (32). A modulator according to claim 25, characterised in that said fourth plate (34) is connected to the output end of the secondary winding of said coupling transformer (38). A modulator according to claim 25 or 26, characterised in that a fifth plate (40) is disposed in spaced apposition to said third plate (16) and electrically isolated from said third plate (16) and said fourth plate (34), said fifth plate (40) being connected through respective parasitic limiting resistors to the third terminals of said power transistors (32). A modulator according to claim 27, characterised in that said fifth plate (40) is arranged for connection to ground. A modulator according to any of claims 20 to 28, characterised in that a plurality of capacitors (30) are connected between said first plate (12) and said second plate (14) such that the connections provide both electrical continuity and mechanical support for said capacitors (30). A modulator according to any of claims 20 to 29, characterised in that a plurality of driver transistors (42) are mounted to said second plate (14). A modulator according to claim 30, characterised in that said driver transistors (42) are connected in parallel. A modulator according to claim 30 or 31, characterised in that said driver transistors (42) are field-effect transistors. A modulator according to claim 32, characterised in that said driver transistors (42) are connected in a common source configuration, the source terminal of each of said driver transistors (42) being connected through a respective fuse resistor to said second plate (14) and therefore in use effectively connected to ground. A modulator according to claim 32 or 33, characterised in that the drain terminals of said driver field effect transistors (42) are connected to the first end of the primary winding of said coupling transformer (38). A modulator according to any of claim 30 to 34, characterised in that the output end of the feedback winding of said coupling transformer (38) is connected through respective resistors to the gate terminals of said driver transistors (42), said gate terminals being connected to other respective resistors which are arranged for connection to an input signal source. A modulator according to any of claims 20 to 35, characterised in that said power transistors (32) are field-effect transistors, and in that said first terminals are the drain terminals of said field-effect transistors. A modulator according to claim 36, characterised in that said power transistors (32) are connected in a common gate configuration to minimize the effects of drain-to-gate capacitance and thereby increase the switching speed of said transistors, the drain terminal of each of said power transistors (32) being connected to said third plate (16) and therefore effectively connected to the second end (24) of the output transformer primary winding. A modulator according to any of claims 20 to 37, characterised in that a plurality of modules (10) are connected to a single microwave tube modulator output transformer (18) to increase the electrical energy available for the operation thereof.

Inventors: EHRENHALT, DAN, GILES, GEORGE RODNEY
Applicants: SIERRA TECHNOLOGIES INC.
Application year: 1988
Main classification: H01L25
IPC codes: H01L25, H01L23