The Marconi Company Limited

Bae Systems Electronics Limited

Robert B Molyneux-Berry

A wave-form generator drives a number of microwave generating devices each operating at different frequency bands. The output of each microwave generator is connected to its own transmission channel of limited bandwidth which contains all the non-linear components necessary for transmission such as an amplifier, T/R switch, rotary joint and beam switch. These individual channels are finally combined onto a common wideband channel which contains only substantially linear components such as a single waveguide and the antenna itself. Because of the isolation between channels there is little or no opportunity for the generation of harmonics or intermodulation distortions which would otherwise occur in a transmitter capable of operating over a very wide bandwidth.

Wide bandwidth radar

An inductor included as part of a pulse width modulation amplifier is formed by four coils 9A, 9B, 9C and 9D arranged alongside each other and connected in parallel. The coils are supported against electromotive forces tending to pull them together by insulating strips 10. The coils are enclosed within an electromagnetic shield formed by a cabinet 1. Because of the arrangement of the coils the magnetic field generated by them is confined to a region in the close vicinity of the coils, so that the losses which would otherwise occur as a result of the proximity of the shield or other cabinet are reduced to a minimum. Thus the efficiency of the inductor formed by the combined coils is greater than would be the efficiency of a single coil within the same cabinet, this latter arrangement being conventional.

Inductor

Because inverter circuits utilize switches which can be adversely affected by signal transients or excessive voltages, it is usual to provide a protective circuit consisting of a capacitor and a resistor. At high frequencies and high powers the energy dissipated in the resistor can be excessive. The present invention provides an additional switch, which is arranged to discharge the capacitor in a lossless manner and to return the energy stored by the capacitor to the power supply by making the discharge path part of a resonant circuit, loss can be reduced to negligible levels.

Inverter circuit for minimizing switching power losses

In an arrangement in which a power source is required to supply energy to a load requiring at times more energy than can consistently be drawn from the source: the invention provides

Power supply arrangements

A pulse width modulation circuit which uses a tube, such as a tetrode tube as the switching element, is arranged to minimise excessive power dissipation in the screen electrode circuit of the tube. The screen electrode is driven from a constant current source to prevent excessive current being diverted from the cathode to the screen electrode which would otherwise occur when the impedance of the anode circuit rises to a high value.

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Danbury, United Kingdom

Robert B Molyneux-Berry