1. Microwave semiconductor devices
Microwave Tubes
Microwave tubes
1 MW
1 KW 1W
1mW
Higher power
Limited life time
High vacuum
High potential
Average power
Microwave semiconductor devices
Lower weight
Smaller size
Longer life time
Frequency (GHz)

2. Two possible methods of achieving high output power in microwave system
High power tube oscillator
Low power semiconductor oscillator
High power tube amplifier

3. Important Parameters Peak power • Average power Efficiency • Gain
Bandwidth • Frequency
Harmonic and spurious power • Intermodulation products
Manufacturability at low cost
Relative complexity of operation
Relative operating voltage
Relative spurious level
Gain (dB)
 (%)
Relative BW (%)
Type 1
Low 2
6-15
20-50
1-10
Gridded tube
High
40-60
30-70
1-5
Klystron 3
30-50
20-40
30-120
Helix tube
5-40
Coupled cavity tube

4. Average power Peak power Frequency (GHz) Frequency (GHz)
10 MW
1 MW
100 KW
10 KW
1 KW
100 W
Frequency (GHz)
Average power
Klystron
Coupled cavity TWT
Helix TWT
Gridded tube
1000 MW
100 MW
10 MW
1 MW
100 KW
10 K W
Frequency (GHz)
Peak power
Coupled cavity TWT
Klystron
Gridded tube
Helix TWT

5. Klystron Microwave input Microwave output Electron beam Beam collector
Electron Gun
Intermediate cavity

6. TWT

7. Major applications for TWTs include:
Amplifiers:
Space applications
Radar
Electron Counter Measure
Missile
Driver for other high power RF amplifiers

8. Missile TWTs for Active Seekers
Features that influence the design include:
Minimal size and weight;
Narrow-to-moderate bandwidths;.
Off-to-fully-operational turn-on times of one second or less;
High efficiency;
High reliability after long inactive storage periods.
Normally, these TWTs are of the periodic-permanent-magnet (PPM) focused helix variety. They normally utilize unique cathode-heater designs to provide the very fast warm-up required. They typically have multiple stage depressed collectors with conduction cooling.