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these amplifiers, this work achieves similar results using a standard low cost BiCMOS 0.35-mm technology. CONCLUSIONA multiband LNA with wideband input impedance matching and switched LC output loads is presented. With this topology a narrowband response for the individual bands is achieved such that the out-of-band noise can be suppressed and the output saturation due to the undesirable blockers can be prevented. As the tuning mechanism is placed at the output of the LNA rather than at the input terminal, its noise contribution to the total NF is minimized. To demonstrate the use of the circuit, a dual-band LNA has been fabricated in a 0.35-mm technology and experimentally verified. The circuit switches two loads centered at 1.8 and 2.4 GHz. The amplifier exhibits a wideband input impedance matching, being the S 11 less that 210 dB over from 900 MHz to 3 GHz. This result holds for any combination of switching loads. The power gain varies between 12.5 dB at 1.8 GHz and 11.5 dB at 2.4 GHz with a NF of 3.8 and 4.1 dB, respectively. ACKNOWLEDGMENTS

In this paper, a microstrip diplexer composed of two similar resonators is designed. The proposed resonator is consisting of four microstrip cells, which are connected to a coupled lines structure. In order to select a suitable geometric structure, first, all cells are assumed as undefined structures where there is a lack of basic information about their geometry and dimensions. Then, an equivalent LC circuit of the coupled lines is introduced and analyzed to estimate the general structure of the resonator respect to a requested resonance frequency. The proposed diplexer is designed to operate at 2.36 and 4 GHz for wireless applications. The insertion losses (S21 and S31) are decreased significantly at the resonance frequencies, so that they are 0.2 and 0.4 dB at 2.36 and 4 GHz, respectively. The designed diplexer is fabricated and measured and the measurement results are in a good agreement with the simulations.

In this work, a lowpass-bandpass diplexer is proposed based on a novel microstrip structure. This diplexer includes two lowpass and bandpass filters integrated by a simple transmission line. The lowpass channel has a cutoff frequency at 1.88 GHz, which makes it suitable for GSM applications. The resonance frequency of the bandpass channel is 3.56 GHz for IEEE 802.16 WiMAX applications. In comparison with the previously reported lowpass-bandpass diplexers, the proposed design has the lowest insertion and return losses at both channels while it occupies the most compact implementation area of 0.03 λg 2. The designed diplexer can suppress the harmonics up to 4.45F C with a maximum harmonic level of −20 dB, where F C is the cutoff frequency of the lowpass channel. The lowpass channel has a very sharp roll-off of ξ = 220, while the bandpass channel has a high selectivity with a high fractional bandwidth of 23.8%. To verify the design method and simulation results, the designed diplexer is fabricated and measured. The simulated and measured results are in a good agreement.