Radar fundamentals

By Armando Mateo

Radar principles

Gemany is the pioneer in radar application

Radar patent in 1904 by Christian Hulsmayer of Germany

History of development

Slant ranges

klystron amplifier

Klystron amplifiers are high power microwave vacuum tubes. Klystrons are velocity-modulated tubes that are used in some radar equipments as amplifiers. Klystrons make use of the transit-time effect by varying the velocity of an electron beam. A klystron uses one or more special cavities, which modulate the electric field around the axis the tube.

Two-cavity klystron amplifier

Functional and schematic diagram of a two-cavity klystron.

Principles of Two-cavity klystron amplifier

The function of the CATCHER GRIDS is to absorb energy from the electron beam. The catcher grids are placed along the beam at a point where the bunches are fully formed. The location is determined by the transit time of the bunches at the natural resonant frequency of the cavities (the resonant frequency of the catcher cavity is the same as the buncher cavity). The location is chosen because maximum energy transfer to the output (catcher) cavity occurs when the electrostatic field is of the correct polarity to slow down the electron bunches.

The two-cavity klystron in may be used either as an oscillator or an amplifier. The configuration shown in the figure is correct for oscillator operation. The feedback path provides energy of the proper delay and phase relationship to sustain oscillations. A signal applied at the buncher grids will be amplified if the feedback path is removed.

Reflex klystron

The Reflex Klystron

The reflex klystron contains a REFLECTOR PLATE, referred to as the REPELLER, instead of the output cavity used in other types of klystrons.

The electron beam is modulated as it was in the other types of klystrons by passing it through an oscillating resonant cavity, but here the similarity ends.

The feedback required to maintain oscillations within the cavity is obtained by reversing the beam and sending it back through the cavity. The electrons in the beam are velocity-modulated before the beam passes through the cavity the second time and will give up the energy required to maintain oscillations. The electron beam is turned around by a negatively charged electrode that repels the beam.

This negative element is the repeller mentioned earlier. This type of klystron oscillator is called a reflex klystron because of the reflex action of the electron beam.

Functional diagram of a reflex klystron.

Bunching action of a reflex klystron.

Electron bunching diagram.

Magnetron

Aegis Weapon System

WAR ROOM OF THE AEGIS WEAPON SYSTEM

USS STERRET(CG-31)

Mk 13 missile launcher

MK 26 Guided Missile Launching System

RIM-2 Terrier

TARTAR fire control AN/SPG-51 radars

AN/SPG-55

AN/SPS-48

AN/SPS-49