Adrian Tang

A New CMOS Active Transformer QPSK Modulator With Optimal Bandwidth Control

This brief presents a new quadrature phase-shift keying (QPSK) modulator for Bluetooth applications with an optimal transaction bandwidth control. The modulator reduces the bandwidth of the modulated carrier by minimizing their transition sharpness. CMOS active transformers are developed and utilized in quadrature oscillator and multiplexer of the modulator to provide comparable phase noise performance without using spiral inductors and transformers. The performance of the modulator is assessed using a 1.6-GHz QPSK base-band modulator implemented in TSMC 0.18-mum 1.8-V CMOS technology and analyzed using SpectreRF from Cadence Design Systems with BSIM3v3 device models. The total transistor area and power consumption of the modulator are 2840 mum2 and 30 mW, respectively. The phase noise of the quadrature oscillator is 110 dBc/Hz at 500-kHz frequency offset.

Current-Mode Phase-Locked Loops With CMOS Active Transformers

This paper introduces active transformer current- mode phase-locked loops (PLLs). The proposed PLLs replaces the RC loop filter of voltage-mode PLLs with an active transformer loop filter to take the advantage of their large inductance and small silicon area. A current-controlled LC oscillator with active inductors is employed to further reduce silicon area. The sensitivity of the cutoff frequency of active transformer loop filter to supply voltage fluctuation and process variation is analyzed. A 3-GHz PLL has been implemented in TSMC 0.18-mum 6-metal 1.8-V CMOS technology and analyzed using SpectreRF with BSIM3v3 device models and Verilog-AMS from cadence design systems. The lock time of the PLL is 60 ns. The power consumption and phase noise of the PLL are 16 m W and -100 dBc/Hz at 1-MHz frequency offset, respectively. The layout area of the PLL is 2800 mum2.

CMOS active transformer current-mode phase-locked loops

This paper introduces active transformer current- mode phase-locked loops. The proposed current-mode PLLs differ from voltage-mode PLLs by replacing their RC loop filter with an active transformer loop filter to take the advantage of the large self and mutual inductances, and small silicon area of active transformers. Implemented in TSMC-0.18 mum CMOS technology, the simulation results of a 3 GHz active transformer current-mode PLL demonstrate that the PLL has the lock time 50 ns, silicon area 2800 mum2, dc power consumption 12.2 mW, and phase noise of -81.5 dBc at 1 MHz frequency offset.

A New CMOS BPSK Modulator with Optimal Transaction Bandwidth Control

A new BPSK modulator for Bluetooth applications is presented. The proposed modulator minimizes the bandwidth of the modulated carrier by minimizing the degree of sharpness of the transactions of modulated carrier. To avoid the drawbacks of large silicon area requirement of passive spiral inductors and transformers, CMOS active transformers are developed from corresponding CMOS active inductors. They are utilized in the design of the 1.6 GHz quadrature oscillator to provide a high-quality sinusoidal output. To assess the performance of the proposed modulator, a 1.6 GHz BPSK modulator has been implemented in a TSMC-0.18mum 1.8V CMOS technology and analyzed using SpectreRF from Cadence Design Systems with BSIM3v3 device models and the simulation results are presented.

A new WiMAX sigma-delta modulator with constant-Q active inductors

This paper presents a new over-sampling sigma delta modulator for WiMAX applications using an active inductor based loop filter and CCO. The loop filter is composed of floating active inductors and offers several key advantages over its MIM capacitor loop filter counterpart including an adjustable bandwidth, an adjustable quality factor, an extremely small silicon area requirement and full compatibility with digitally oriented CMOS processes. The proposed modulator is implemented in UMCs 0.13 mum 1.3 CMOS process. The sigma delta modulator comparator and sampler are driven from a new constant-Q active inductor CCO that provides phase noise below 118 dBc/Hz at 4 GHz operation. The sigma delta modulator exhibits a signal to noise ratio (SNR) of 42 dB and a dynamic range (DR) of 63 dB at a sample rate of 2 G/s with an oversampling ratio (OSR) of 40 making it ideal for base-band sampling in WiMAX transceivers.

CMOS current-mode active transformer sigma-delta modulators

This paper presents a new current-mode sigma-delta modulator for Bluetooth base-band applications. The modulator employs a current-mode ADC, a current-mode DAC, and a new active transformer loop filter to provide the desired noise shaping characteristics. The modulator provides the advantages of tunable filter bandwidth and an extremely small silicon area consumption. The modulator has been implemented in TSMCpsilas 0.18 mum 1.8V CMOS technology and analyzed using SpectreRF from Cadence Design Systems with BSIM3V3-RF device models. The simulation results have demonstrated that the modulator exhibits a SNR of 65 dB and a dynamic range of 50 dB at a sample rate of 500 M/s and a bandwidth of 5 MHz while occupying 0.0073 mm2 silicon area.

Low-nose CMOS active transformer voltage-controlled oscillators

This paper presents CMOS active transformers synthesized using MOS transistors only and their applications in VCOs. The characteristics of CMOS active transformers are analyzed, and the self and mutual components of the quality factor of transformers are investigated. Simulation results of LC, quadrature, and transformer VCOs with active inductors and active transformers show that active transformer VCOs exhibit a much lower level of phase noise as compared with corresponding LC and quadrature VCOs with active inductors. The phase noise of the designed 1.5 GHz active transformer VCO in TSMC-0.18 mum 1.8 V CMOS technology is -109.4dBc/Hz at a 1 MHz offset the carrier and is comparable to that of VCO with spiral inductors. The power consumption of the oscillator is 30.5 mW with 83 mum2 active area.

Class AB CMOS Active Transformer Voltage-Controlled Oscillators

This paper presents class AB CMOS active transformers synthesized using MOS transistors only and their applications in voltage-controlled oscillators. It is shown that the class AB active transformer VCO exhibits lower phase noise than class A transformer configurations. Simulation results of self and mutual inductance, impedance, and phase noise of class A and class AB active transformer oscillators are presented. The phase noise of the designed 1.6 GHz class AB active transformer VCO in TSMC-0.18 mum 1.8 V CMOS technology is -122.9 dBc/Hz at a 1 MHz offset the carrier and is comparable to that of VCOs with passive spiral inductors.

A New 2.4GHz CMOS Low-Noise Amplifier with Automatic Gain Control

A new 2.4 GHz CMOS low-noise amplifier with automatic gain control that provides an enhanced dynamic range of up to 40 dB over conventional low-noise amplifiers is proposed. The proposed low-noise amplifier automatically adjusts its voltage gain by monitoring the amplitude of its output voltage so as to achieve a large dynamic range. The proposed low- noise amplifier allows a receiver system to become adaptive to antenna array, waveguides, and transmission lines, as well as standard antenna signal powers. The amplifier provides a gain of over 35 dB, a noise figure below 0.5 dB, and reflection coefficient below -35 dB at 2.4 GHz. The transient time of the amplifier is approximately 23 mus with the variation of the input RF power of 30 dBm.