Hossein Miar-Naimi

Conventional analyses of phase and amplitude imbalances in quadrature LC CMOS oscillators are typically performed in the time-domain under large-signal conditions, where tank series losses are approximated as a fixed parallel resistance to simplify the analysis. However, this simplification fails to accurately capture the effects of practical tank losses, which are inherently represented as a series resistance in real LC oscillators. To address this limitation, a novel theoretical framework is developed for analyzing phase and amplitude imbalances in quadrature LC CMOS oscillators. The analysis is carried out in the phasor-domain using a modified small-signal circuit model (MSSCM). Unlike prior studies, the proposed approach explicitly incorporates the series resistance of the inductor as the dominant tank loss, resulting in a nonlinear formulation for phase and amplitude imbalances. Closed-form expressions for these errors are derived across three fundamental topologies: series-coupled, parallel-coupled, and source-injection-coupled accounting for Q variations. Additionally, the maximum steady-state oscillation amplitude under mismatch conditions is derived. The accuracy of the proposed model is validated through extensive simulations, showing strong agreement with numerical results. This comprehensive analysis offers deeper insight into the mechanisms underlying phase and amplitude imbalances and, ultimately, presents multiple techniques for the simultaneous compensation of these errors across different quadrature oscillator topologies.

This paper aims to find a closed-form expression for the frequency and amplitude of single-ended ring oscillators when transistors experience all regions. In this paper, the analytical relationships presented for ring oscillator amplitude and frequency are approximately derived due to the nonlinear nature of this oscillator, taking into account the differential equation that governs the ring oscillator and its output waveform. In the case where the transistors experience the cut-off region, the relationships presented so far have no connection between the frequency and the dimensions of the transistor, which is not valid in practice. The relationship is presented for the frequency, including the dimensions of the transistor. Also, a simple and approximately accurate relationship for the oscillator amplitude is provided in this case. The validity of these relationships has been investigated by analyzing and simulating a single-ended oscillator in 0.18 µm technology.

This article presents a solution based on continuous mode for designing broadband class-E power amplifiers (PAs), which is realized by transmission of the second-harmonic current with appropriate phase to load network of a class-E PAs. This theory allows selecting appropriate second-harmonic impedance causing part of efficiency to be sacrificed to get a bandwidth over one octave. The mathematical formulation for optimum load impedance in main harmonic, second harmonic, output power, drain efficiency (DE), and load quality factor (QL) is developed in this case. Theoretical results are compared with conventional narrowband class-E counterparts. To check the authentication of mathematical analysis and simulation results, a proof-of-concept broadband continuous-mode class-E PAs is fabricated using the CGH40025F transistor. The manufactured PAs show 43-dBm output power, with average DE 70% over the 0.6–1.8-GHz frequency range. Also, a narrowband conventional class-E PA for frequency range 1.2–1.8 GHz with the same transistor as broadband class-E PA is fabricated for better comparison. The output power and average DE of the conventional class-E PA are 42.5 dBm and 80%, respectively.

A modified noise/nonlinearity cancellation low-noise transconductance amplifier (LNTA) based on an inductively degenerated common-source stage is proposed to improve linearity. The linearity of the proposed LNTA is analyzed using the Volterra series yielding closed-form equations for the third-order input intercept point (IIP3) that shows excellent matching with the simulation results. The derived equations for noise figure (NF) and IIP3 are simple enough to be used for design optimization. Calculations and simulation results show that the proposed LNTA is more linear than a conventional one, while NF approximately remains unchanged. Another feature of the proposed noise-canceling LNTA is that no additional baseband recombination stage is needed, leading to reduced complexity in the receiver baseband stage. The NF and out-of-band (OOB) IIP3 of the receiver is about 3.3 dB and more than 20 dBm, respectively. The receiver consumes 10.5 mA from 1.8-V supply voltage. The current consumption of the LO divider is 6.5 mA from a dedicated 1-V supply voltage.

In Gray coded rectangular and square quadrature amplitude modulation(QAM), for each bit, the bit decision boundaries are distributed only along one dimension. Consequently, the exact calculation of bit error probability(BEP) of rectangular and square QAM in the additive white Gaussian noise(AWGN) channel results in simple one-dimensional(1-D) error/Q-functions. This is while the symbol decision boundaries involve two dimensions. This paper presents exact and general expressions for the BEP of Gray coded M-ary rectangular and square QAM in the presence of phase noise in the AWGN as well as flat-fading channels. In doing so, we first derive exact expressions for the BEP of MQAM in the presence of a fixed phase error. The expression will be a weighted sum of 1-D complementary error functions for the AWGN channel. For the flat-fading channels, these formulas consist of only single integrals or simple functions. We then integrate these formulas across noise distribution, to derive the average BEP expression of Gray coded MQAM in the presence of random phase error. Moreover, we provide an exact expression for the bit error floor(BEF) of MQAM in the presence of phase noise in the AWGN and fading channels. The exact expressions include numerous terms for higher order MQAM. Considering the most dominant terms of the exact expressions, we also propose simpler expressions. Simulation results validate the accuracy of the proposed exact expressions for arbitrary levels of input SNR. Moreover, the results show very good performance for the approximate expressions.