GB2163918A - Radar modulator - Google Patents

Abstract

A radar transmitter comprises a main output tube 4 which is driven by a driver tube 7. The output tube 4 is powered by pulses supplied via a transformer 3 from a number of pulse generating modules 2A to 2E. The driver tube 7 is powered from a lesser number, in this case 1, of identical modules 2F. In the event of a breakdown of the module 2F which is essential for the operation of the system a switch S1 is operated so as to redirect the output of one of the modules 2A to 2E to the transformer feeding the driver tube 7. <IMAGE>

Description

SPECIFICATION Apparatus for transmitting pulses of electromagentic radiation This invention relates to apparatus for transmitting pulses of electromagnetic radiation. It is particularly though not exclusively applicable to a radartransmitter.

Pulsed microwave transmitters which are required to be coherent, i.e., to maintain a precise phase relationship between the transmitted frequency of successive pulses, use high power amplifiers to amplify a low level signal generated by a frequency synthesiserto a higher power level required to be delivered to an aerial. A type of device commonly chosen for this task is known as a "Linear Beam Tube". Travelling wave tubes and klystrons are two examples of such devices.

When a Linear Beam Tube is energised from a suitable power source it is capable of amplifying a signal fed into its input port. The degree of amplification, however, is not without limit and as a result it is quite normal to use two such tubes in series to provide adequate amplification. Each tube requires its own pulse generator to provide its source of pulse power. There are two significant problems in using two or more such tubes in parallel. Firstly the power level of the lower power tube, although well below that of the output tube, is still sufficient to call for a pulse generator of a similar complexity of design to the output tube pulse generator.Should the lower power tube (sometimes referred to as driver tube) modulatorfail then the radar system will be rendered totally inoperative, even though the main output tube modulator may still operate satisfactorily. Secondly, the techniques used for the driver modulator and the output modulator are usually quite different. Thus spares holding and manufacturing processes are further complicated leading to increased cost of equipment and subsequent increase in running costs to the end user.

This invention provides apparatus for transmitting pulses of electromagnetic radiation comprising a radio frequency device, a plurality of first pulse generating circuits arranged to feed pulses to the radio frequency device and a further pulse generating circuit, similar to the first circuits, connected to provide pulses to an auxiliary component, the operation of which is essential for operation of the radio frequency device.

By employing the invention it is possible to design a system which enables interchange of modular pulse generating circuits from one function to another. This is useful because the breakdown of say the one and only pulse generator providing power for an ancillary component such as a driver tube may result in complete failure of the system. If the faulty pulse generator is replaced by one borrowed from a number of similar pulse generators supplying power to the main output tube; continued operation is possible, though at reduced power. A further advantage is that only a single type of spare module need be kept and stored.

One way in which the invention may be performed will now be described by way of example with reference to the accompanying block diagram of a radar transmitter constructed in accordance with the invention.

Referring to the drawing a control unit 1, provided by a computer, receives control signals at inputs 1A, 1 B and 1 C defining characteristics of pulses to be transmitted. Such characteristics may include for example the pulse repitition frequency and the pulse duration.

In response to the input signals on lines 1A, 1 B and 1 C the control unit 1 passes timing signals on line 1D to each of a number of similar modules 2A to 2H of which modules 2A to 2F are identical.

These modules are designed so that they can readily be plugged in and out of their supporting structure. Each module is designed to generate a high current pulse at its output terminals in respnse to the timing signals from the control unit 1.

Modules 2A to 2E pass their output pulses to respective primaries of a transformer 3 thus generating a high voltage pulse at a secondary of the transformer. This high voltage pulse is applied to a main output tube 4 from which an RF output at 4A is passed to an antenna (not shown).

The output pulses from module 2F are passed to the primary of a second transformer 5. This generates, at its secondary 6, a high voltage pulse which is applied to a driver tube 7. The driver tube 7 receives a radio frequency input at 7A which it amplifies, passing the amplified signal on line 7B to the output tube 4. The module 2F is identical to the modules 2A to 2E but the driver tube 7 in fact requires less power than a single module is capable of delivering. For this reason a resistor R is applied across the primary of the transformer 5. A diode D prevents the resistor from loading the transformer 7 during a reset pulse whose generation is described below. In the event of a breakdown of the module 2F a switch SI operates thereby transferring the function of module 2E from that of supplying power to the output tube 4 to a function of powering the driver tube 7.

The module 2G receives timing signals from line 1 E. These are different from the signals on line 1 D and occur at times so that the pulses produced at 2G are in-between the pulses produced by the other modules. A module 2G is also of modified design so as to produce a longer pulse of lower voltage. In an alternative construction the module 2G could be identical to the others and receive its control signal from line 1 D.

In that case however some further circuitry would need to be included to delay and expand the signals from line 1D before being applied to the module 2G; and to reduce the output voltage of the module 2G.

The module 2H is a spare which is identical to the module 2G and can be brought into service by a switch S2 to replace the module 2G if the latter is faulty.

Each of the modules produces an output labelled "status" which indicates whether it is operating correctly. This signal is passed to the control unit 1 and in the event of one of the modules not function ing correctly the control unit outputs a "control" signal which is applied to the input labelled "con trol" of the faulty module this switches it off. If the faulty module is the module 2F i.e., a module whose operation is essential for continued functioning of the system, the control unit 1 produces a control signal which operates a switch, the switch S1 in this particular embodiment. The switch S1 serves to transfer the function of module 2E to that of powerin#g the drivertube that has previously been described. If the faulty module is the module 2G the control unit outputs a similar control signal which operates the switch S2 thereby bringing the spare or standby module 2H into operation.

Claims (6)

1. Apparatusfortransmitting pulses of electromagnetic radiation comprising a radio-frequency device and a plurality of first pulse generating circuits arranged to feed pulses to the radiofrequency device and a further pulse generating circuit similar to the first circuits, connected to provide pulses to an ancilliarycomponentthe opera tion of which is essential for functioning of the radio-frequency device.

2. Apparatus according to claim 1 including means for detecting a malfunction of the said first circuit and in response to such a detection switching either a spare pulse generating circuit or one of the first mentioned circuits into a conditon where it provides pulses to the ancilliary component.

3. Apparatus according to claim 1 or 2 in which the said radio-frequency device is an output tube and the ancilliary component is a driver tube arranged to drive the outputtube.

4. Apparatus according to claim 1 in which the first mentioned pulse generating circuits are arranged to feed pulses to the radio-frequency device via a transformer and in which the ancilliary component is a reset winding on the transformer.

5. Apparatus according to any preceding claim in which the pulse generating circuits are all identical.

6. Apparatus according to claim and substantially as described with reference to the accompanying drawings.