Over the
2.4 to 2.5 GHz Industrial, Scientific, Medical (ISM) band, the
maximum reflection coefficient is -15.7 dB, which corresponds
to a voltage standing wave ratio of 1.39:1. Far-field gain
radiation patterns (E-plane and H-plane cuts) were measured
in an anechoic chamber and the results at 2.4 GHz are
shown in Figure 4. The measured peak gain is 7.2 dBi and
the half-power beamwidth is 72 degrees. Referring to the
laptop radar in Figure 1, the center-to-center spacing of two
vertically polarized coffee cans is typically about 20 cm,
and the measured transmit/receive mutual coupling (S21) at
2.4 GHz is -39 dB. Thus for this simple design with two
circular waveguide antennas for transmit and receive, students
are made aware of a number of important topics in antenna
design including waveguides, probes, polarization, reflection
coefficient, gain, radiation patterns, transmit power density,
receive power, antenna arrays, and mutual coupling.