The rectangular microstrip patch antenna (RMPA) and square microstrip
patch antenna (SMPA), designed to resonate at about 10 GHz, are excite
d by a electromagnetically coupled microstrip line. The effect of vari
ation in the offset and inset of the feed line on resonating frequency
(f(r)), VSWR, and impedance bandwidth (BW) are experimentally studied
using alumina substrate. It is seen that SMPA gives the highest BW of
4.98% for diagonal feed. The lowest BW obtained is for side-fed SMPA
(0.012%), with maximum variation in BW of 1:278. The best trade-off to
get such a variable BW easily, with only feed point adjustment using
electromagnetic coupling for these patches, is to use a long-side-fed
RMPA which gives sufficiently good BW variation of 1:98 and the lowest
possible mismatch error, while adjusting the relative position of the
feeder microstrip line. All the bandwidths mentioned above are only o
btained when, simultaneously, VSWR < 2. Such an RMPA may also give mul
tifrequency operation. (C) 1993 John Wiley & Sons, Inc.