Fig. 2. General geometry of microstrip antenna without feed. The radiation characteristic of the CMSA is depicted as shown in Fig. 3. On the other hand, power spectra generated in full-wave rectification are shown in Fig. 4. The DC spectrum and even-numbered spectra of the dominant frequency (2.45 GHz) are generated as shown in Fig. 4. Therefore, it can be expected that there exists almost no higher harmonic reradiation from the CMSA. WIDE FREQUENCY BAND CHARACTERISTICS OF THE CMSA First, the CMSA matching to a 50 ohm feeder line atf0 = 2.45 GHz was printed on copper clad laminate whose dielectric constant Er is about 2.6. Return loss versus frequency is shown by a dotted line of Fig. 5 where frequency range is from 2 GHz to 12.4 GHz which means that data until 5 f0 (12.25 GHz) can be obtained. The figure shows that the CMSA has resonance frequencies in vicinity to 2f„ (4.9 GHz) and 3/0 (7.35 GHz). On the other hand, return loss for the dipole with ground plane is fairly low over the experimental frequency as shown in Fig. 5. The received power by the CMSA and dipole is shown in Fig. 6. The dipole receives the highest power over the entire frequency examined except in vicinity to 3/. The reason why this exception occurs can be explained using Fig. 7 where surface currents of three modes (TM110, TM010 and TM120) are depicted. The resonance frequencies of TM110, TM010 and TM120 are f0, 2.08 f0 and 2.9/0> respectively. Two modes (especially TM120) can be easily excited at 2.08 f0 2.9/0, respectively. In order to suppress TM010 and TM120 modes, slits are cut on the CMSA as
RkJQdWJsaXNoZXIy MTU5NjU0Mg==