Electromagnetics and Antenna TY ETC 1UEXC601 Question Bank

A loop antenna is used in radio direction finding to determine the direction of a radio signal source by detecting the phase difference between the signals received by the loop's two arms.

The array factor for an N element linear array is $AF(\theta) = Nsin(\frac{N\pi d}{\lambda}sin(\theta))$. The principal maxima occur at $\theta = 0$, the nulls at $\theta = \pm \frac{m\pi}{N}$, and the secondary maxima at $\theta = \pm \frac{2m+1}{2N}\pi$.

The array factor for two isotropic sources with the same amplitude and opposite phase is $AF( heta) = 2 + 2cos(\theta)$. The Half Power Beamwidth (HPBW) is 180 degrees and the Backward Front-to-Back Ratio (BWFN) is 0 dB.

<p>A folded antenna is an antenna structure where the radiating element is folded to reduce size and increase bandwidth. It works by creating a longer electrical length in a smaller physical space. Advantages include wider bandwidth, reduced size, and improved impedance matching.</p> Signup and view all the answers

<p>Broadside array has its main lobe perpendicular to the array axis, while End fire array has its main lobe along the array axis. Broadside array has higher directivity but broader beamwidth compared to End fire array.</p> Signup and view all the answers

<p>The radiation resistance of a small dipole is approximately $73\Omega$. It represents the equivalent resistance that would dissipate the same amount of power radiated by the dipole into the far field.</p> Signup and view all the answers

<p>The radiation resistance of a half-wavelength dipole antenna is $73\Omega$. The actual length variation is due to end effects and the velocity factor of the material used in construction, leading to a slightly shorter physical length for resonance.</p> Signup and view all the answers