Inductive Output Tube
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The Inductive Output Tube ( IOT ) is an electron tube for amplifying high-frequency signals in the UHF and L frequency bands . In the IOT, the intensity of a cathode ray is modulated via a grid , as in the tetrode . The modulated electron beam gains energy through a static high-voltage field between the grid and a tubular acceleration electrode ( anode ), is magnetically focused and then passes a cavity resonator , in which its density modulation is converted into high-frequency power like a klystron . Then he meets a collector ( collector ).
As with the klystron, the high-frequency power is extracted from the cavity resonator by electromagnetic coupling with a waveguide (coaxial or waveguide). The tubular anode also prevents the high frequency from being fed back into the grid anode space.
The IOT is also called a klystrode because it can be viewed as a combination of a klystron and a triode. Efficiencies of up to 75% were measured.
As with disc triodes, the upper limit frequency is determined by the distance between the grid and the cathode; it is only about 0.1 mm to ensure that the electrons have passed the grid before the modulation voltage changes polarity. The maximum operating frequency is therefore now 1500 MHz .
IOTs are mainly used in powerful terrestrial television transmitters, but increasingly also in particle accelerators in high-energy physics . There they have largely displaced the klystron in the power range up to around 100 kW . The advantages over the klystron are the 10–20% higher efficiency , the comparatively small dimensions and, associated with this, the approx. 30% lower price. A particular disadvantage is the low gain of only approx. 22-25 dB . (Klystrons typically achieve gains of> 40 dB.) In the area of even higher powers and frequencies, the klystron is currently unrivaled.