Roghoyeh Salmeh

A comparison of bipolar and CMOS mixer structures for direct conversion modulation at microwave frequencies

The mixer is one of the fundamental circuit blocks of any wireless communication system. Most portable communication systems have at least two mixers, one in the receiver and another in the transmitter. Although high performance bipolar and CMOS mixers have been available for some time, their implementation is still a challenging subject for high frequencies, low-voltage and low-power circuit design. In this paper double balanced mixers performing direct conversion modulation are studied. The problems of noise and non-linearities are also addressed.

Impacts of the pads, ESD diodes and package parasitic on the noise figure and gain of a common source low noise amplifier

The impacts of the pads, ESD diodes, wirebonds and package parasitic on the noise figure of a common source low noise amplifier (LNA) are studied. For the general case a common source LNA without the source degeneration inductor has been considered. An electrical model for quad flat nonleaded (QFN) package is presented and used to examine the effects of package parasitic. Equations of input impedance and transconductance of the LNA are derived. Effects of the pads, ESD diodes, package parasitic and input matching components on the gain and noise figure for power constrain optimization technique are highlighted.

A low voltage linearly tuned fully differential CMOS OTA and its applications in filter design

This paper presents an adaptation of a transconductor built around MOSFETs operating in saturation. The circuit operates off a 3.3 V single supply and has a fully differential output. A common mode feedback circuit maintains the output near midsupply. Simulation results show that the transconductor is linearly tunable over a wide range of bias voltages. The transconductor is used to realize a second order filter in TSMC (Taiwan Semiconductor Manufacturing Corporation) 0.18 /spl mu/m CMOS technology. Tuned by a DC voltage V/sub fo/ the filter center frequency was measured to be almost linearly adjustable from 833 kHz up to 1.3 MHz. The common mode voltage at the filter output was also observed to vary by no more than 24 mV about the desired value. A maximum THD of -35 dB is guaranteed at V/sub out/=600 mV/sub pp/ within the tuning range of the filter.

Two-Tone Phase Delay Control of Center Frequency and Bandwidth in Low-Noise-Amplifier RF Front Ends

This brief presents a two-tone system for controlling the center frequency and bandwidth of an RLC tank with an application to center frequency and bandwidth control in low noise amplifier (LNA) RF front ends. The circuit operates based on the fact that an RLC tank induces a phase difference with special properties between two frequencies. The system is demonstrated in hardware in the TSMC CMOS 0.18-μm process for a center frequency of 2.45 GHz and a bandwidth of 60 MHz. The LNA center frequency can be controlled with a precision of ≈0.2% while the bandwidth can be controlled with a precision of ≈8%. The tuning time is 3 μs multiplied by the number of tuning states. The tuning states are the circuit states set digitally and analyzed until the desired operating point is achieved.

A novel wide-band 5.3 GHz ESD protected input and output matched low noise amplifier

In this paper the design of a novel 5.3 GHz wide band input and output matched low noise amplifier (LNA) is presented. The LNA uses a conventional cascode architecture and is implemented in IBM SiGe5AM technology. Powered by a 2-V supply the LNA features 11.13dB of measured power gain and a 3 GHz bandwidth at 5.3 GHz. The LNA draws only 8 mA current from a 2 V supply. Input and output return losses of -12.6 dB and -9.16 dB have been achieved, respectively.

An Ultra Low Power ESD Protected Mixer in 90nm RF CMOS

Behavioral analysis of a low voltage/low power mixer in 90 nm CMOS technology is demonstrated. The down conversion mixer achieves a measured conversion gain of 2.55 dB and input 1 dB compression point of- 6.5 dBm. The mixer draws only 0.24 mA from a 1.2 V supply. A wide band output IF of 500 kHz up to 100 MHz was also achieved.

Effects of variation of input matching inductor on the minimum noise figure of a low noise amplifier

This paper describes the effects of gate inductance on noise figure of a low noise amplifier designed based on a noise optimization technique. We show that the minimum noise figure of the LNA is not very sensitive to the changes in L/sub g/. A 1.57 GHz, 0.55 dB noise figure LNA was designed in CMOS 0.13 /spl mu/m technology to confirm the validity of the theory. Powered by a 1.1 V supply the LNA features 12.9 dB of gain and is stable over a wide frequency range. The LNA draws only 1 mA and has an input return loss of -17 dB.

VLSI implementation of an automatic Q tuning system

In this paper we present an innovative approach to VLSI implementation of Q tuning of analog lowpass filters. The proposed scheme uses the LMS algorithm to adaptively compensate changes in input amplitude and frequency. A tunable OTA is designed to implement the automatic control loop in the integrated circuit. The tuning system was implemented in CMOS 0.18 µ m technology in a master-slave configuration.

A novel Q -tuning scheme for continuous time filters

A quality-factor-tuning scheme for analogue lowpass or highpass continuous time filters is presented. The proposed method uses the LMS algorithm to simultaneously adapt the quality factor of a desired filter and the phase shift of an allpass filter. Simulation results confirm the validity of the technique for both Q and phase shift tuning. An experimental setup of a circuit using discrete components shows that an error in Q of 1.7% at a desired Q of 0.68 is possible and that the scheme is adaptive to changes in input amplitude and frequency.

Novel centre frequency and bandwidth control of RF LNA using two-tones phase delay

This paper presents a two-tone system to control the center frequency and bandwidth of an RLC tank in front-end LNAs. The control mechanism is based on the characteristic of an RLC tank, which induces a phase difference between the two frequencies. The proposed system is implemented on chip in the TSMC 0.18 μm CMOS technology. The LNAs centre frequency and bandwidth were set at 2.45 GHz and 60 MHz, respectively. Precisions of 0.2% for centre frequency control and 8% for the bandwidth control were achieved. The two-tones phase delay principle can be generalized to tuning based on any information signal containing two tones with related phases and known frequencies.