Ultra-wide band (UWB) and multi-band systems have recently received a great deal of attention as a next-generation wireless communication system for high data rate and multi-application devices. In this dissertation, we investigate the performance limitations of the wideband amplifier for high power dissipation, nonlinearity, and noise figure. We propose four amplifiers to improve the disadvantages of the wideband amplifier.
We present a design of a low power CMOS UWB low noise amplifier (LNA) using a noise canceling technique. The proposed UWB LNA employs a current-reused structure to decrease the total power consumption instead of using a cascade stage. This structure spends the same DC current for operating two transistors simultaneously. The stagger-tuning technique, which was reported to achieve gain flatness in the required frequency, was adopted to have low and high resonance frequency points over the entire bandwidth from 3.1 to 10.6 GHz. The resonance points were set in 3 GHz and 10 GHz to provide enough gain flatness and return loss. In addition, the noise canceling technique was used to cancel the dominant noise source, which is generated by the first transistor. However, the wide band gain response topology has nonlinearity and noise problems. To solve the problems of wideband amplifier, we propose three switchable amplifiers.
We first propose the design of a 2.5/3.5-GHz dual-band low-power and low-noise CMOS amplifier, which uses the capacitor cross-coupling technique and current-reuse method with four switches. The proposed LNA uses a single RF block and a broadband input stage, which is a key aspect for the easy reconfiguration of a dual-band LNA. Switching at the inter-stage and output allows for the selection of a different standard. The dual-band LNA attenuates the undesired interference of a broadband gain response circuit, which allows the linearity of the amplifier to be improved. The capacitor cross-coupled gm-boosting method improves the NF and reduces the current consumption. The proposed LNA employs a current-reused structure to decrease the total power consumption. The inter-stage and output switched resonators switch the LNA between the 2.5-GHz and 3.5-GHz bands. The proposed dual-band LNA optimizes power consumption by the securing gain, noise figure, and linearity.
To increase frequency band coverage, we use modified switching method in second switchable amplifier. Second system is a 3-5 GHz UWB low power and low noise amplifier which uses a novel dual input matching network for wideband matching. We use a current-reuse gm-boosted common-gate topology and shunt-shunt feedback common-source output buffer to improve gain and noise figure with low power dissipation. The proposed dual input matching gm-boosted common-gate LNA has efficient bandwidth to cover UWB band. It requires less inductors or amplification stages to increase bandwidth as compared with the conventional UWB common-gate LNAs. The broadband input stage can be switched to three frequency bands with capacitive switches. The capacitive switch replaces a large inductor to resonate at lower frequency band. The band-selective LNA shows linearity improvement by attenuating the undesired interference of a wideband gain circuit and using fewer inductors.
Third system is a three stage 3-5 GHz band-selective UWB LNA. A capacitor cross-coupled gm-boosting broadband input stage is adopted for an input matching and high gain, and also improves the NF and reduces the current consumption. The noise performance of the LNA is improved significantly by a noise cancelation stage. A band-selective stage using a tunable active inductor controls input and output matching simultaneously using one output stage tuning circuit. The key aspect of the proposed active inductor is a reduction of interference, noise, and complexity problems of conventional wide input-tunable output and input tuning architectures. We use a variable capacitor to further improve noise performance, quality factor, and inductance of the active inductor and to provide a wide frequency tuning range.