Digital Microwave system

These are also known as digital radio system,PCM radio system or digital line-of-sight microwave systems.A basic digital microwave system is shown in fig.Digital source block may have many PCM converted digitized voice channels,digital computer or other data channels.The transmitting block modulates the radio frequency carrier digitally by bit streams from digital source.After amplification,the modulated signal is radiated by a suitable antenna. Duplexer is employed to have the same antenna while transmitting or receiving.The receiver block demodulates the modulated signal and gives the digital message to the digital sink block which  in turn gives the original message.
For a digital microwave system two factors are important
(i)Source bit rate and
(ii)Digital signal code.
Transmission rate for low capacity microwave systems<=1Mb/sec.Transmission rate for high capacity microwave system >= 300 <=Mb/sec.
TDM-PCM channel banks are main sources of digital radio systems.Hence digital radio systems are also known as PCM radio systems.
The block diagram of a hypothetical one-way  PCM-radio path.According to CCIR definitions,hypothetical digital radio path contains 9 radio terminals connected by 9 higher order digital multiplex equipment  data rate of the system is 64 kb/sec at each end of the system and the system length is 2500 km. Digital input stream from the transmit section of TDM equipment is applied to the modulator of the   radio transmitter.