This paper presents a transmitter architecture based on a pulse-modulated polar transmitter using multiphase pulsewidth modulation. The modulation to the radio-frequency input signal, instead of conventional drain modulation, significantly reduces the circuit complexity, while the multiphase modulation technique reduces the out-of-band emissions. An 836.5-MHz four-phase prototype transmitter using four class-C power amplifiers in parallel was constructed. Using the transmitter, single-phase, two-phase, and four-phase pulsewidth modulated signals were tested to verify the benefits of using the proposed multiphase architecture. Using a CDMA2000 1X signal, 46.8% efficiency at a 29-dBm output power level was measured while passing the spectral-mask requirements without using any kind of digital predistortion or calibration.

This paper presents an architecture for implementing a wide dynamic range pulse-modulated polar transmitter and its system-level requirements. For validation of the proposed architecture, a simulation platform is constructed using a CDMA2000 1X signal. The system level simulation results show that the architecture can achieve over 80-dB dynamic range easily and accurately while passing the spectral requirements of the CDMA2000 standard. Using the simulation results, design specifications of various blocks required for implementing the proposed architecture are derived and reported. Compared to a conventional linear transmitter architecture that uses two high-resolution digital-to-analog converters (DACs), the proposed architecture requires only two low-resolution DACs and an all-digital pulse width modulation block. The eased DAC requirements would significantly reduce the cost and space for implementing a radio-frequency transmitter.

This article presents a balanced pulse-modulated polar transmitter that is capable of withstanding load mismatch and out-ofband reflection. The balanced architecture directs the reflected power to the isolated port of the 90 -hybrid coupler. Using a rectifier, the reflected power can be recycled and used for assisting the supply of the polar transmitter. A prototype system was implemented and measurement was performed for validation.

A dual-phase pulse-modulated polar transmitter (PMPT) for wide power control range (PCR) applications is presented. For the validation of the proposed architecture, a radio-frequency (RF) PMPT chip is implemented with a standard 0.18 μm 1P6M mixed-signal CMOS process. The measurement results show that by using the proposed technique, wide PCR transmitters can be implemented accurately with low hardware requirements. An RF variable-gain amplifier with just 21 dB of dynamic range is sufficient to pass the 80 dB PCR of the CDMA2000 standard. Compared with a conventional transmitter utilising linear power amplifiers, the proposed architecture has the potential of achieving much higher efficiency while being able to achieve chip-level integration with eased circuit design specification.

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