Distributed CMOS Bidirectional Amplifiers

RF photonics technology such as Radio-over-fiber (RoF) is a way to distribute RF signals to base stations and Cable TV networks [3–5]. In RoF direct modulation transmission systems, the input current of a semiconductor laser is directly modulated by the information-bearing RF signal. Due to the nonlinear relationship between the input current and the output optical power of the semiconductor laser, distortion is introduced to the RoF transmission system.

In this chapter, RF modulation schemes effects on RF power amplifier nonlinearities are presented. A review of various power amplifier RF linearization techniques are discussed.

In this chapter, analysis of the distributed amplification principles are presented in this chapter. Different linearized transconductors to compensate for the nonlinearity are also presented.

The interest in high-level integration and highly linear multi-functional broadband subsystems motivates the development of linearized distributed circuit applications. In this chapter, the application of RF linearization to distributed circuit functions such as fully-integrated CMOS linearized distributed active power splitter (unbalanced input, balanced output) and a linearized CMOS distributed matrix amplifier are presented. Also the linearized CMOS distributed paraphase amplifier employing derivative superposition linearization is presented as well.

In this chapter, we demonstrate a fully-integrated fully-differential linearizedCMOS distributed bidirectional amplifier that achieves large IMD3 distortion reduction over broadband frequency range for both RF paths. The drain and gate transmissionlines were stagger-compensated. Reducing the DA IM3 distortion by mismatching the gate and drain LC delay-line ladders. A CMOS cross-coupled compensator transconductor is proposed to enhance the linearity of the DA gain cell with a varactor-based active post nonlinear drain capacitance compensator for wider linearization bandwidth.

This chapter presents several practical layout guidelines of the fully-integrated fully-differential linearized distributed bidirectional amplifier implemented in IBM CMOS RF 0.13µm silicon process. The total chip silicon area is 1.5mm² including testing pads. The circuit elements forming the linearized CMOS bidirectional distributed amplifier are discussed in terms of their physical arrangement and layout.

This chapter presents the experimental test setups for the fully-integrated linearized CMOS RF 0.13µm bidirectional distributed amplifier. The chip measurements that are carried out include small-signal s-parameters such as gain and return loss, harmonics power measurements such as 1-dB compression, IMD (intermodulation distortion) and noise figure measurements. All RF measurements are performed with on-wafer probing.

The emphasis on higher data-rates has driven the industry towards linear modulation techniques such as QPSK, QAM and multi-carrier configurations. Spectral efficiency has become a significant factor in the use of such linear modulation techniques. The result is a signal with a fluctuating envelope which generates intermodulation distortion from the power amplifiers. Linear modulation techniques are more spectral efficient however requires a linear power amplifier. Broadband power amplifiers are important RF components in a wireless communications system. All power amplifiers exhibit inherent nonlinearity which causes spectral regrowth in systems using non-constant envelope digital modulation schemes. The main source of spectral regrowth is the intermodulation distortion of the modulated carrier by nonlinearities in the transmitter power amplifier. Requirements for suppression of spectral regrowth have become more stringent and the improvement in spectral regrowth suppression is the primary reason for using power amplifier linearization techniques.