Lmt Radioprofessionnelle

Yan Haentjens

Maurice Marchand

In a microwave preamplifier of a Doppler radar system used for Earth observation, three pre-matched and self-biassed field effect microwave transistors are provided. By supplying these transistors by means of a voltage regulator, whose output voltage varies under the action of a control circuit, the gain of this pre-amplifier may be varied without modifying the standing wave ratio, thereby obtaining modulation of the microwave signal amplified by the amplifier. Thus, additional modulation may be obtained, speech modulation for example, on the transmission signal of an Earth observation Doppler radar system.

Field effect transistor microwave amplifier

In a microwave power transmitter for Doppler radars for terrestrial surveillance, use is made of four stages in series comprising first and second preamplifiers, and first and second power amplifiers. These stages are supplied by a group of separate voltage regulators. These regulators are controlled by a control circuit which makes it possible to cut off the stabilized voltage between instants of transmission, that is to say between microwave pulses of a radar signal. A feedback device makes it possible to stabilize the output level by causing variation of the gain of the first preamplifier by means of its supply voltage.

Microwave power transmitter for doppler radar

A mixer comprising two microstrip plates, each having an earth plane, a dielectric layer and an etched layer. One of the etched layers carries the mixer ring and input guides. The outer etched layer carries the output guide and the tuning members. The plate are joined by their earth planes and the mixer diodes are placed in the holes connecting the two etched faces.

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Boulogne Billancourt, France

Yan Haentjens