Microwave and Radio Based System

Microwave:

                Microwave are radio wave with wavelength ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz.

                Microwaves are widely used for point-to-point communications because their small wavelength allows conveniently-sized antennas to direct them in narrow beams, which can be pointed directly at the receiving antenna. This allows nearby microwave equipment to use the same frequencies without interfering with each other, as lower frequency radio waves do. Another advantage is that the high frequency of microwaves gives the microwave band a very large information-carrying capacity; the microwave band has a bandwidth 30 times that of all the rest of the radio spectrum below it. A disadvantage is that microwaves are limited to line of sight propagation; they cannot pass around hills or mountains as lower frequency radio waves can.

Properties of a Microwave:

• Suitable over line-of-sight transmission links without obstacles
• Provides large useful bandwidth when compared to lower frequencies (HF, VHF, UHF)
• Affected by the refractive index (temperature, pressure and humidity) of the atmosphere, rain, snow and hail, sand storms, clouds, mist and fog, strongly depending on the frequency.

Comparison of frequency bands and distances:

                There are even differences between one type of microwave and another. The differences are due primarily to their respective operating frequencies. Some frequencies are good for distances of 30 or 40 miles and others can barely get you across an office park. Some can only support a couple of T1s or a single video channel and others go to 10 to 45 Mb.

Table that show’s comparison of frequency bands and distances

Other Application of Microwave:

               

                A laptop computer with a credit card−sized PRISM radio chip set can now convert incoming microwave messages into binary code for computer processing and then convert them back into microwaves for transmission.

Similarly, microwave transmission is used in LANs, on corporate or college campuses, in airports, and elsewhere. Whether it is collecting data, relaying conversations, or beaming messages from space, microwave makes the wireless revolution possible.

                Laptop computers can now send and receive microwave radio transmissions.

Microwave Radio Relay:

                Microwave radio relay is a technology for transmitting digital and analog signals, such as long-distance telephone calls, television programs, and computer data, between two locations on a line-of-sight radio path. In microwave radio relay, radio waves are transmitted between the two locations with directional antenna, forming a fixed radio connection between the two points. Long daisy-chained series of such links form transcontinental telephone and/or television communication systems.