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ExamsGATETechnical

The electric field in a rectangular waveguide of inner dimensions \(a\times b\) is given by \[ \mathbf{E}=\left(\frac{\omega\mu}{h^2}\right)\left(\frac{\pi}{a}\right)H_0\sin\left(\frac{2\pi x}{a}\right)\sin(\omega t-\beta z)\,\hat{y} \] where \(H_0\) is a constant, and \(a\) and \(b\) are the dimensions along the x-axis and the y-axis, respectively. The mode of propagation in the waveguide is

  1. TE20
  2. TM11
  3. TM20
  4. TE10

Correct answer: TE20

Solution

In rectangular waveguides, TM modes have a longitudinal electric field, while TE modes have no longitudinal electric field. The dependence \(\sin(2\pi x/a)\) corresponds to \(m=2\) and there is no variation in \(y\), so \(n=0\). Therefore the mode is TE\(_{20}\).

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