This paper presents microstrip transmission lines for designing a microstrip open loop resonator bandpass filter and a novel dual band transmitter. Microstrip open loop resonator bandpass filter with the dumbbell DGS under feed lines enhances the harmonic suppressed at the center frequency of 2.44 GHz. An asymmetric dumbbell DGS-integrated microstrip line is applied to the dual band transmitter which performs as a frequency doubler at 6.8 GHz or a power amplifier at 2.4 GHz. For the proposed bandpass filter,it has a wide stopband characteristic with attenuation -25 dB up to 8 GHz and has an -1.25 dB insertion loss by using two dumbbell DGS. Measurements of the dual band transmitter show that in frequency double mode,fundamen tal suppression and maximum output are -41 dBc and 7.8 dBm. And in amplifier mode,second harmonic suppression,P1 dB and gain achieve -52.6 dBc,13.7 dBm and 16.5 dB, respectively.
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