HW#3_594I

# HW#3_594I - ECE594I, Prof. Brown, Fall Quarter 2009 HW#3:...

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ECE594I, Prof. Brown, Fall Quarter 2009 1 HW#3: Antennas for the THz Region 1. Feedhorns: Metallic feedhorns have long been popular as antennas at mm-wave and THz frequencies. The simplest designs transform a single mode waveguide to free space through a length of linear taper, as shown in Fig. 1. The waveguide end of the feedhorn is called the throat , while the free-space end is called the mouth . If the waveguide is rectangular, the feedhorn is usually pyramidal in form. If the waveguide is circular, the feedhorn is usually conical in form. The standard types of both pyramidal and conical feedhorns have a smooth taper, and the far-field radiation pattern has sidelobes. If azimuthally-symmetric grooves are cut in the taper section of the horn, it is possible to excite a higher order spatial mode in the horn in just the right way that the sidelobes are cancelled in the far field. In this case, the far field pattern can be represented by a monotonic function of polar angle θ , often by the following Gaussian function: F ( θ ) = exp (-a θ 2 ), θ in units of radians. Calculate the following for a = 10: (a) The FWHM beamwidth β (b) The pattern solid angle B (c) The antenna directivity D (d) S max at a range of 10 cm if the total radiated power is 1 mW.

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## This note was uploaded on 12/02/2009 for the course ECE 000 taught by Professor O during the Spring '09 term at UCSB.

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HW#3_594I - ECE594I, Prof. Brown, Fall Quarter 2009 HW#3:...

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