A comprehensive review of the electrical performance of passive transformers fabricated in silicon IC technology is presented. Two types of transformer construction are considered in detail, and the characteristics of two-port (1:1 and 1:n turns ratio) and multiport transformers (i.e., baluns) are presented from both computer simulation and experimental measurements. The effects of parasitics and imperfect coupling between transformer windings are outlined from the circuit point of view. Resonant tuning is shown to reduce the losses between input and output at the expense of operating bandwidth. A procedure for estimating the size of a monolithic transformer to meet a given specification is outlined, and circuit examples are used to illustrate the applications of the monolithic transformer in RF ICs.

Monolithic transformers for silicon RF IC design

Underlying physical mechanisms controlling the noise properties of oscillators are studied. This treatment shows the importance of inductance selection for oscillator noise optimization. A design strategy centered around an inductance selection scheme is executed using a practical graphical optimization method to optimize phase noise subject to design constraints such as power dissipation, tank amplitude, tuning range, startup condition, and diameters of spiral inductors. The optimization technique is demonstrated through a design example, leading to a 2.4-GHz fully integrated, LC voltage-controlled oscillator (VCO) implemented using 0.35-/spl mu/m MOS transistors. The measured phase-noise values are -121, -117, and -115 dBc/Hz at 600-kHz offset from 1.91, 2.03, and 2.60-GHz carriers, respectively. The VCO dissipates 4 mA from a 2.5-V supply voltage. The inversion mode MOSCAP tuning is used to achieve 26% of tuning range. Two figures of merit for performance comparison of various oscillators are introduced and used to compare this work to previously reported results.

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Concepts and methods in optimization of integrated LC VCOs

This paper will summarize the technology tradeoffs that are involved in the implementation of radio frequency integrated circuits for wireless communications. Radio transceiver circuits have a very broad range of requirements-including noise figure, linearity, gain, phase noise, and power dissipation. The advantages and disadvantages of each of the competing technologies-Si CMOS and bipolar junction transistors (BJTs), Si/SiGe HBTs and GaAs MESFETs, PHEMTS and HBTs will be examined in light of these requirements.

Integrated circuit technology options for RFICs-present status and future directions

The construction and electrical characteristics of two-port transformers (1:1 and 1:n turns ratio) and multi-port transformer baluns fabricated in a production silicon technology are presented. A high-linearity 5 GHz mixer design illustrates the advantages of the trifilar transformer in an RF IC application.

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We present a theory of the noise transfer in LC tuned oscillators accounting for the nonlinear operation of the transconductor. We show that the transconductor switching causes a folding of the wide-band noise such as the thermal noise of the spreading resistance of the bipolar transistors and the noise of the tail current generator. The effect is similar to what happens in sampled systems, however, for a careful evaluation of the oscillator phase noise, the correlations between the folded terms is of chief importance. We show how to account for the effect, we assess the impact on the oscillator noise performance and we give the guidelines for the circuit optimization.

Spectrum folding and phase noise in LC tuned oscillators

This work introduces fully-integrated VCOs implemented in the mature ISOSAT silicon bipolar RFIC process. The ISOSAT silicon bipolar process has transistors with 15GHz f/sub T/ and 30GHz f/sub max/, along with MIS capacitors of Q > 50 and spiral inductors with Q up to 10 for the values and frequency range of interest. Recently, a voltage-variable capacitor (or varactor) was characterized within the process. This device has up to 3:1 capacitance range from 0 to 3V reverse bias and also has Q of 3060 in the 1.1-2.2GHz frequency range desired for these VCOs.

S. Jansen

Papers

Silicon bipolar VCO family for 1.1 to 2.2 GHz with fully-integrated tank and tuning circuits