This thesis presents the design of a broadband and high speed dc-coupled AGC amplifier for multi-level (4-PAM) signaling with a symbol rate of 1-GS/s ( 2-Gb/s ) . It is a high frequency analog design with several design challenges such as high -3 dB bandwidth ( greater than 500 MHz ) and highly linear gain while accommodating a large input swing range ( 120 mVp-p to 1800 mVp-p diff.) and delivering constant differential output swing of 1700 mVp-p to 50-ohm off-chip loads at high speed. Moreover, the gain control circuit has been designed in analog domain. The amplifier incorporates both active and passive feedback in shunt-shunt topology in order to achieve wide bandwidth. This standalone chip has been implemented in AMS 0.35 micron CMOS process. The post layout eye-diagrams seem to be quite satisfactory.

The rapid evolution of wireless communication technologies increased the need for handheld devices that can support dissimilar standards or better user mobility and more battery life. Traditional radio architectures fail to satisfy these challenging features. Software Defined Radio (SDR) is recently introduced to implement a new generation of wireless radios capable of coping with these stringent requirements through software reprogramming. Although the term SDR is widely used, it is still an idealized method and is not implementable using available technologies. Hence, the term “SDR”, has been so far, referring to only partially upgradeable radios. Two current practical solutions substituting SDR are broadband and multiband transceivers. Radio Frequency (RF) front ends and especially the power amplifier is the main challenge in implementation of software defined radios. Power Amplifiers (PA) dominate the sources of distortions and power consumption in the RF-front end. They are typically operated in linear classes in order to minimize the linearity degradation. However, they lead to poor average power efficiency especially when fed with signals with high Peak to average power ratio (PAPR) such as Wideband Code Division Multiple Access (W-CDMA) and Long Term Evolution (LTE) signals. This is the main cause of short battery life in transceivers. To remedy this issue, some advanced methods like Doherty amplifier and drain modulation based architectures are introduced. This thesis expounds on the implementation of high efficiency radio transmitters, capable of multi standard operation. The RF amplifier is still one of the main challenges in the realization of these transmitters. In this work, two RF PAs, having multiband and broad band characteristics, were implemented using 0.13µm CMOS technology. The first PA operates at two frequency bands, 2.4GHz and 3.5GHz. The other PA has center frequency equal to 2.4GHz and 600MHz bandwidth, respectively. These PAs are expected to lay the foundation for the realization of high efficiency drain modulation based multiband and broadband transmitters.

This thesis consists of two parts. Part one presents a design of class-AB power amplifier in 0.15£gm pHEMT process, and establishes a nonlinear model with memory effects for the power amplifier using Volterra series. To observe the memory effects, two-tone continuous wave signals have been applied to the model to predict the phase variation between IM3H and IM3L as a function of tone spacing. In the meanwhile, a time-domain measurement technique for the third-order intermodulation responses using a digital storage oscilloscope has been developed to verify the modeled predictions on IM3H and IM3L. Comparison between modeled and measured results shows good agreement. Part two of this thesis is to study the CMOS power-combining techniques. At first, the pros and cons between series and parallel combining transformers are discussed. Then, a design of class-E power amplifier using a pair of parallel combining transformers for power combining is presented. Both simulated and measured results show that the presented Class-E power amplifier has a high power-added efficiency.

The thesis is composed of tow topics: a high performance current-balancing instrumentation amplifier (IA) for ECG (Electrocardiogram) monitoring systems and an IA with CMRR (Common-Mode Rejection Ratio) self-calibration. In the first topic, a high common mode rejection ratio (CMRR) and a low input referred noise instrumentation amplifier (IA) is presented for ECG applications. A high pass filter (HPF) with a small-Gm OTA using a current division technique is employed to attain small transconductance, which needs only a small capacitor in the HPF such that the integration on silicon is highly feasible. The proposed design is carried out by TSMC standard 0.18 £gm CMOS technology. CMRR is found to be 127 dB and the voltage gain is 45 dB according to the simulation results. The second topic discloses an instrumentation amplifier with CMRR self-calibration capability. The propose design is also carried out by TSMC standard 0.18 £gm CMOS technology. To achieve a CMRR of more than 80 dB, a calibration resistance string and a detection circuit have been utilized. The DC gain of the proposed design is 60 dB and the frequency bandwidth is bound in 10 KHz, which is adaptable for biomedical signal acquisition applications.

Selectively erbium (Er) doped titanium (Ti) in-diffused optical waveguide amplifiers on lithium niobate (LiNbO3) substrate have been fabricated and characterized in the wavelength regime around λ = 1.53μm using counter-directional pumping at λP = 1.48μm. LiNbO3 waveguide amplifiers are desirable for providing gain in optical circuit chips through integration with other optical elements on a single substrate. A prerequisite for achieving useful gain rests on the optimization of overlap between the incident guided optical signal mode distribution and the evolving emission from excited Er ions. The extent of overlap can be controlled by adjusting fabrication parameters. Fabrication parameters for Er-doped Ti in-diffused waveguide amplifiers of useful optical gain have been optimized by diffusing selective patterns of vacuum-deposited 17nm-thick erbium film at 1100˚C for 100 hours into LiNbO3, and integrating with 7μm-wide single mode straight channel waveguides formed by diffusing 1070Å thick titanium film into the LiNbO3. Small-signal gain characterization was carried out with a -30 dBm of transmitted input signal power at λS=1531nm with counter-directionally launched pump power ranging between 0 to 119mW at λP=1488nm, using TM polarization for both the signal and pump beams. At a maximum launched pump power of 119mW, a signal enhancement of 8.8dBm for 25mm-long erbium doped region, and 11.6dBm for 35mm-long erbium doped region were obtained. The corresponding calculated net gain values are 1.8dB and 2.8dB, for the 25mm-long and 35mm-long Er-doped regions, respectively.

The maximum capacity of an optical fiber transmission system more than doubled every year to match the fast-growing communication need. The technology break through in dry fiber fabrication opens the possibility for fiber bandwidth all the way from 1.3 mm to 1.6 mm. The fast increasing demand of communication capacity results in the emergence of wavelength division multiplexing (WDM) technology, which results in the need for wideband optical amplifier. Cr4+:YAG has a strong spontaneous emission that covers 1.3 mm to 1.6 mm. Besides, its absorption spectrum is between 0.9 mm to 1.2 mm, which matches with the pumping source in current erbium doped optical amplifier. Such a fiber is, therefore, eminently suitable for optical amplifier applications. We have successfully fused the double cladding Cr4+:YAG crystal fiber with single mode fiber by fusion splicer. The crystal fibers are grown by the laser-heated pedestal growth technique. The splicing parameters are optimized to achieve an insertion loss of below 1 dB. Since, the core diameter tapering will increase the propagation loss and reduce the gross gain. Adiabatically tapered fiber is discussed. Simulations are performed to predict the loss, and compare with the experimental results, then find out the way to improve the gross gain. Numerical simulation indicates that the gross gain could reach 37.2 dB at 0.5 W pump, if the core diameter of the double cladding Cr4+:YAG crystal fiber is reduced to 5 mm. In the future, in order to increase gross gain we will improve the mode matching between the cores of single mode fiber and the double cladding Cr4+:YAG crystal fiber. Gradual change of the refractive index at the splicing region as well as high Cr4+ doping concentration can also improve the gross gain.

In this thesis, we use InP based multiple quantum well epi-wafer with modulation doping in the active layer to design the semiconductor optical amplifier and ring laser for the optical communication at 1.55£gm wavelength. We also finish the mask design and fabrication of theses two devices. Besides, we have established an optical measurement system, including the L-I measurement, the optical spectrum measurement and the far field measurement, to test the device parameters. In the device process, we use the new method, called the Multi-Step Undercutting, to precisely control the undercut in the wet etching process. With this technique, we can get a smooth and vertical sidewall for our devices. For the semiconductor optical amplifier, we design two different types, one is the Fabry-Perot Amplifier and the other is the Traveling Wave Amplifier. We use the Multi-Step Undercutting process in the fabrication of these two devices. The main parameters for semiconductor optical amplifier are the change of the output power versus the input current, the spontaneous emission spectrum and the photocurrent spectrum. For the ring laser, we combine the concept of Loop Mirror and Asymmetric Mach-Zehnder Interferometer to obtain the laser with good side mode suppression for a single wavelength light source.

In this thesis, we focus on the investigation of semiconductor optical amplifier and ring laser. We use InP based multiple quantum well epi-wafer with modulation doping in the active layer to design the semiconductor optical amplifier and ring laser for the optical communication at 1.55£gm wavelength. We combine the concept of Loop Mirror and Asymmetric Mach-Zehnder Interferometer to obtain the laser with good side mode suppression for a single wavelength light source. For the semiconductor optical amplifier, we design two different types, one is the Fabry-Perot Amplifier and the other is the Traveling Wave Amplifier. Furthermore, We use the Multi-Step Undercutting process in the fabrication of these two devices. We have established an optical measurement system, including the L-I measurement, the optical spectrum measurement and the far field measurement, to test the device parameters. After annealing, these devices with two different serial number exhibited the contact resistances of 9£[ and 16£[, respectively. Under CW operation, these FPA exhibited the threshold current of 62mA and 70mA at 20¢J, respectively. The stimulated emission wavelength was at 1531nm and 1522nm, respectively.

The maximum capacity of an optical fiber transmission system more than doubled every year to match the fast-growing communication need. The technology break through in dry fiber fabrication opens the possibility for fiber bandwidth all the way from 1.3 £gm to 1.6 £gm. The fast increasing demand of communication capacity results in the emergence of wavelength division multiplexing (WDM) technology, which results in the need for wideband optical amplifier. Cr4+:YAG has a strong spontaneous emission that covers 1.3 £gm to 1.6 £gm. Besides, its absorption spectrum is between 0.9 £gm to 1.2 £gm, which matches with the pumping source in current erbium doped optical amplifier. Such a fiber is, therefore, eminently suitable for optical amplifier applications. We have successfully fused the double cladding Cr4+:YAG crystal fiber with single mode fiber by fusion splicer. The crystal fibers are grown by the laser-heated pedestal growth technique. The splicing parameters are optimized to achieve an insertion loss of 3.8 dB. Througth the splicing images, we can quantitatively analyze the splicing results caused by fine tuned parameters, and aimed at the evolution of the ASE, that is dissipated into inner cladding. The simulation program is revised with better fitting. We can find the reason why net gain is under 0 dB by simulation result, and find the way to improve. Numerical simulation indicates that the gain can reach 2 dB at 1 W pump, if the core diameter of the double cladding Cr4+:YAG crystal fiber is reduced to 10 £gm. In the future, we¡¦ll reduce the core diameter of Cr4+:YAG crystal double cladding fiber to less than 10 £gm, and enhance the Cr4+ ion concentration to lower the insertion loss after two-sided splicing, Hopefull, super-wideband optical amplifier can be realized.

The maximum capacity of an optical fiber transmission system more than doubled every year to match the fast-growing communication need. The technology break through in dry fiber fabrication opens the possibility for fiber bandwidth all the way from 1300nm to 1600nm. The fast increasing demand of communication capacity results in the emergence of wavelength division multiplexing (WDM) technology, which results in the need for ultra-wideband optical amplifier. Cr4+:YAG has a strong spontaneous emission that covers 1300nm to 1600nm. Besides, its absorption spectrum is between 900nm to 1200nm, which matches with the pumping source in current erbium doped optical amplifier. Such a fiber is, therefore, eminently suitable for optical amplifier applications. In this article, we will introduce the development of ultra-wideband optical amplifier using the double-clad Cr4+:YAG crystal fiber, which is grown by laser heated pedestal growth(LHPG) technique. Its material properties as well as optical gain will be characterized. By butt-coupling method, a low insertion loss of 4.2 dB was achieved in a SMF-CDF-SMF configuration, and it was measured to demonstrate a gross gain of 2.4 dB at 1 W bi-directional pump power. Moreover, theoretical models and numerical simulations have been developed to predict the experimental results. Numerical simulation indicates that the efficiency of mode overlapping between signal and pump is crucial to gain performance. The mode overlapping efficiency is about 25%~30% for our crystal fiber under current circumstances. In the future, we will make an attempt to reduce the index contrast between core and cladding for better mode overlapping efficiency. At the same time, we also try to grow crystal fiber of smaller core diameter to improve gain performance.