Introduction
The importance of radio direction and range, or radar, in military
applications has gained a quite attention recently . It is used for the
detection of enemy ships and aircraft, the control of night fighters of
raiding squadrons, and for precise bombing at night or through overcast
and it is operated mostly in the microwave region.
For high frequency waves generation and the transmission, the
dimensions of the component used are comparable with the wavelength,
this is the basic principle lies behind the characterization of microwave
region and the form of the microwave circuits used. The duplexer is the
important part of microwave radar. It is necessary to keep in mind the
parameters that explains the performance of a radar system, to have idea
about the problems involved in the development and design of duplexers
and duplexing components.
A radar is operated by the detecting the energy reflected from a distant
target. A radar transmitter sends a short pulse of energy , and the pulse
scatters after striking a reflecting object. The scattered wave, which is
reduced in amplitude still in the form of a short pulse, is picked up by
the radar receiver. The range of the target object is obtained by
determining the length of time between the transmission of the high
power pulse and the reception of the weak reflected pulse and the
direction of the target is obtained thus by measuring the direction in
which the radar antenna is pointed when a signal of maximum intensity
is being received.
The electromagnetic spectrum range of S-band portion of the
microwave band ranges from 2.0 to 4.0 GHz., i.e. crossing the boundary
between UHF and SHF at 3.0 GHz. The wavelength of S-band is around
10 cm. The S band radar is shared by maritime industry with other
entities permitted by the Federal Communications Commission (FCC) in
