The Marconi Company Limited

Roger E Gerard

Boleslaw M Sosin

A high power amplifier arrangement utilizes a configuration which is similar to that of a distributed amplifier in which the capacitances of a plurality of individual amplifying devices form part of a delay line which couples together the amplifying device, so as to sum the output power. The invention enables amplifying devices, such as vacuum tubes or field effect transistors which have significant electrode capacitances, to be used to amplify wide band high frequency signals. Each amplifying device is provided with an associated output impedance having a value which is matched to that of the output delay line on to which it fits. The output delay line consists of a number of stages separated by power combiners connected to different respective amplifying devices. This configuration can be more efficient than a conventional distributed amplifier, and its use is more acceptable in conjunction with loads, such as antennas whose actual input impedance can differ somewhat from a nominal design value.

High power amplifier arrangements

The present invention provides a modified distributed amplifier which is capable of accepting two or more independent inputs and amplifying them without giving rise to a large number of significant intermodulation products. This modified distributed amplifier effectively comprises two or more unmodified distributed amplifiers (as V.sub.11 to V.sub.18 and V.sub.21 to V.sub.28) joined so as to have a common output line (10) but individual, independent, input lines (111 and 211). The join is preferably 'back-to-back' (in a parallel sense) so that the individual distributed amplifiers are in some sort of interleaved arrangement.

Multisignal amplification

A feedforward amplifier is designed to exhibit particularly linear transfer characteristics in which distortion signals introduced by the amplifier itself are monitored and the phase and amplitude characteristics of respective adaptive equalizers are modified to reduce any distortions at these points. A reference signal is injected directly into a main amplifying element so that it appears at the output terminal as though it were an amplified induced distortion. The characteristics of the amplifier are adaptively modified to eliminate the reference signal from the output signal.

Feedforward amplifiers

A feedforward amplifier compensates for distortions introduced by a main amplifying device by comparing the amplified signal with the original unamplified signal and producing a correction signal, which is related to the difference. The correction signal is combined with the main amplified signal at a combiner. The combiner takes the form of a tetrode or pentode valve which acts as a current source and which is designed so as to constitute part of an output transmission line having a predetermined characteristic impedance. By this means the combiner does not adversely affect the main amplified signal and the capacitance inevitably associated with a tetrode or pentode valve is utilized as part of the reactance of the transmission line and does not adversely affect the frequency response of the amplifier.

Amplifiers

For many applications it is desirable that electronic amplifiers have good linearity (a typical such application is in the field of high frequency radio transmission). Various arrangements and designs have been employed to ensure that the desired linearity is attained, but some types of amplifier have proven rather difficult in this respect: such a type is the distributed amplifier, where the correction of amplification errors has proven particularly difficult because of the relatively large time delay (and thus signal phase difference) 'across' the amplifier. The present invention seeks to provide a distributed amplifier system allowing the easier correction of amplifier errors. Specifically, the invention provides an electronic amplification system incorporating a distributed amplifier, which system comprises comparison means (12,13) for comparing the shape of the input control signal with the shape of the final output signal, and for providing a difference signal indicative of any amplifier-induced distortion, correction signal generating means (V.sub.9) for forming in dependance upon the difference signal a correction signal, and combiner means (14) for combining the correction signal with the final output signal so as substantially to cancel the amplifier-induced distortion.

Electronic amplification systems

A frequency generator provides a number of selectable predetermined spot frequencies to a high degree of accuracy in an economical manner. The output from a phase lock loop having a variable frequency divider is divided by a further variable frequency divider. The two dividers are controlled by pairs of divisor values held in a store.

Phase locked loop frequency generator having stored selectable dividing

In a message signal scrambling apparatus, the signal is divided into elements, each of one time slot duration, and the elements are re-arranged in order so as to produce a signal scrambled in time. Each element is entered and stored in a charge coupled device, from which is extracted as required to form part of a re-arranged order of elements.

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Chelmsford, United Kingdom

Roger E Gerard