| dc.description.abstract | In broadcasting, the coverage and interference requirements of antennas are designated
in terms of Effective Radiated Power (ERP), tower location and height,
and antenna patterns. When antennas are tailored to satisfy the requirements,
transmitter powers, cable losses, and phase adjustments for antenna elements
must be taken into account in addition to the parasitic effect of the supporting
and nearby towers on characteristics of antenna.
Digital video and audio broadcasting requires antennas to be at least 95 % effi-
cient, wideband, low weight and high gain with enhanced radiation performance.
For this reason many wire and planar antennas have been designed to meet the
requirement of Digital Video Broadcasting-Terrestrial (DVB-T) and TerrestrialDigital
Audio Broadcasting (T-DAB).
We used a tool NEC (Numerical Electromagnetic Code) to model antenna on
top of a tower structure. Simulation results for parasitic effect of the tower on
characteristics of antenna such as impedance, return loss, gain, front-to-back ratio
and radiation patterns are reported. In addition, the effect of nearby tower on
antenna characteristics is studied. We designed a broadband antenna in the UHF
(470 - 860 MHz) band that works for both digital and analog TV with return loss
≥10 dB, fractional bandwidth of 85% and gain at center frequency 12.5 dB. The
ERP is calculated by mounting the antenna at each face of the tower to give a
satisfactory coverage to a region around the antenna.
Moreover, the design of a transmitter antenna for DVB-T and T-DAB is presented
with Stacked Suspended Plate Antenna (SSPA) structure. Considering
the similar products in the world, antennas have been designed in (174-254)MHz
for DVB-T and (174-230)MHz for T-DAB with horizontal polarization and return
loss ≥ 10 dB. The antenna gives an average gain of 8.5 dB and cross polarization
isolation is 31 dB. Contrary to conventional dipole structures, we have employed
SSPA structure with two plates for wideband matching and design flexibility.
Radiating primary plate has been excited by novel wideband modified inverted
L-type probe in a capacitively coupled manner. Vertical plate between primary
plate and ground plane also provides wideband matching and adjustment of halfpower
beam width properly. Parasitic secondary plate has been used for further
matching and tuning. Together with the parametric study of designed antenna,
simulation and measurement results for the input impedance, S11, gain and radiation
patterns are presented. | en_US |
