Microwave Generator

Your question makes no sense.

It is impossible to answer.

Signal generators...

http://en.wikipedia.org/wiki/Signal_generator

You ask a very broad question, the following defines "microwaves" as below 1 metre to 1mm wavelength, or 300 MHz to 300 GHz ....

http://en.wikipedia.org/wiki/Microwave

Also, the word "telecommunications" is very broad, since it means "communication at a distance".

Telecommunications used to mean telephone communications (audio speech channels of 300 - 3400 Hz) - and microwave was many speech channels. Approximately, a 600 speech channel analog system could carry one analog PAL/NTSC television channel.

Nowadays, most communication is digital.

However, any high capacity system has problems of frequency stability, linearity or timing error which make direct use of a microwave oscillator, even at 300 MHz, a problem. Usually, the master oscillator is a quartz crystal-transistor unit which is fed through frequency doubler/tripler/amplifier chains to get the final frequency.

Frequency modulation [or FSK - frequency shift keying (digital stepping between 2 frequencies] is common, because the considerable erratic amplitude fading possible due to rain etc on direct radio paths has little effect.

Since frequency modulation of a stable oscillator is limited, it was usual to phase modulate the amplified oscillator signal, then limit the amplitude of that to a constant value - leaving only frequency modulation. This frequency modulated signal was then amplified before feeding into doublers/tripler chains to get the final frequency.

The "travelling wave tube" has seen much use since it can give very wide band linear amplification [say 2:1 bandwidth] and can give very high powers at microwaves. Useful for satellite repeaters, where each communication path must use a different frequency.

Microwave repeater use for "fixed line" telephone connection began to decline in the 1980s with the advent of optical fibre systems. However, modern mobile-phone systems use microwaves, 2 GHz, 3 GHz etc, both to connect base-station to phone and to interconnect stations. So the base stations could be considered "repeaters".

Various types of transistor are used in these systems for microwave amplification etc.

thanks...

Partial list of devices that can be used to generate and/or amplify RF/Microwave frequencies:

Magnetron tube, Klystron tube, TWT , Gunn diode, Tunnel diode, IMPATT diode, TRAPATT diode, MESFET, HEMT, ...

Some wiki links for reference:

http://en.wikipedia.org/wiki/Cavity_magnetron
http://en.wikipedia.org/wiki/Klystron
http://en.wikipedia.org/wiki/Travelling_wave_tube
http://en.wikipedia.org/wiki/Gunn_diode
http://en.wikipedia.org/wiki/Tunnel_diode
http://en.wikipedia.org/wiki/IMPATT_diode
http://en.wikipedia.org/wiki/Avalanche_transistor#The_controlled_avalanche_transit-time_triode_.28CATT.29
http://en.wikipedia.org/wiki/MESFET
http://en.wikipedia.org/wiki/High_electron_mobility_transistor