been designed and implemented in the 0.18 m CMOS technology, and it is designed to operate in the 5.44 GHz frequency band. The figure of merit for the proposed QVCO is Ϫ186.6 dBc/Hz. The QVCO shows phase noise of Ϫ115.62 dBc/Hz at 1 MHz offset from the oscillation frequency of 5.44 GHz while dissipating 2.4 mW for the whole QVCO from the supply voltage of 0.6 V. A low-voltage quadrature CMOS VCO based on voltage-voltage feedback topology, IEEE Microwave Wireless Compon Lett 16 (2006), 696 -698. 9. C.C. Boon, M.A. Do, K.S. Yeo, J.G. Ma, and R.Y. Zhao, Parasiticcompensated quadrature LC oscillator, IEE Proc Circ Dev Syst 151 (2004), 45-48. 10. A. Mazzanti, P. Uggetti, and F. Svelto, Analysis and design of injection-locked LC dividers for quadrature generation, IEEE J Solid State A symmetrical 6-GHz fully integrated cascode coupling CMOS LC quadrature VCO, IEEE Microwave Wireless Compon Lett 15 (2005), 670 -672. ABSTRACT: This article introduces a new architecture for a highefficiency linear transmitter using a pulse modulated envelope signal. The transmitter employs multilevel PWM to represent the baseband signal. By using multilevel PWM, the efficiency of the power amplifier can be improved compared with that using the conventional PWM. To demonstrate the validity of the proposed architecture, a transmitter using threelevel PWM is implemented and tested with the CDMA IS-95A signal. The measured PAE, including isolator and filter loss, is 37.6% at 21.6 dBm average output power and the linearity requirements are satisfied.
A new discrete‐amplitude pulse width modulation (DAPWM) scheme for a high‐efficiency linear power amplifier is proposed. A radio frequency (RF) input signal is divided into an envelope and a phase modulated carrier. The low‐frequency envelope is modulated so that it can be represented by a pulse whose area is proportional to its amplitude. The modulated pulse has at least two different pulse amplitude levels in order that the duty ratios of the pulse are kept large for small input. Then, an RF pulse train is generated by mixing the modulated envelope with the phase modulated carrier. The RF pulse train is amplified by a switching‐mode power amplifier, and the original RF input signal is restored by a band pass filter. Because duty ratios of the RF pulse train are kept large in spite of a small input envelope, the DAPWM technique can reduce loss from harmonic components. Furthermore, it reduces filtering efforts required to suppress harmonic components. Simulations show that the overall efficiency of the pulsed power amplifier with DAPWM is about 60.3% for a mobile WiMax signal. This is approximately a 73% increase compared to a pulsed power amplifier with PWM.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.