We present a numerical model of a wideband injection-locked frequency modulator used in a polar transmitter for 3G cellular radio application. At the heart of the system is a self-injection-locked oscillator with a programmable linear tuning range of up to 200 MHz at 4-GHz oscillation frequency. The oscillator is injection locked to a time-delayed version of its resonating voltage, and its frequency is modulated by manipulating the phase and amplitude of the injected current. The model is used to study the feasibility of the proposed system by analyzing the impact of various impairments in the auxiliary injection loop on the system performance. The model is written in MATLAB/SIMULINK, and the simulation output is analyzed by a vector signal analyzer in terms of 3GPP specifications. Based on the simulation results, key specifications for individual blocks in the system are determined. The key benefits of the presented modeling methodology are simplicity, efficiency, and portability.@en

A digital-to-frequency converter (DFC) assisted by a built-in-self-measurement mechanism is presented. It demonstrates the capability to overcome oscillator pulling that is caused by the high-speed digital frequency-tuning signal that is fed into the DFC’s digitally-controlled-oscillator (DCO), thereby allowing the DFC to accommodate high-rate modulating data. Thus, by placing replica images and quantization noise far away from the transmitted carrier, the presented DFC is suitable for wireless applications having the most demanding spectral mask requirements, without necessitating RF filtering in the transmitter’s signal path. The proposed solution, designed with minimum overhead, reduces the extent of injection pulling experienced by the digitally controlled oscillator (DCO) due to ΣΔ dithering applied to its capacitor bank by adjusting the phase between the aggressor and victim signals through a digitally controlled delay (DCD) line. The proposed calibration and compensation scheme for the DCD is autonomous and simple computationally. The proposed solution has been demonstrated in a transmitter of a commercial cellular CMOS system-on-chip (SoC).@en

A programmable self-characterization technique is presented, whose purpose is to determine the extent of mismatches present in a variable-capacitor (varactor) array as part of an LC tank of a digitally controlled oscillator (DCO). The varactor array represents a digital-to-analog conversion function, such that mismatches in it cause distortion in the DCO's digital frequency tracking and modulation. The presented technique, relying exclusively on internal resources in the system-on-chip (SoC) and on dedicated software, is implemented in a 65nm CMOS Digital RF Processor (DRP) based transceiver, and demonstrates sufficient accuracy to allow relatively quick measurements of mismatches of a few percent.

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A novel approach for mitigation of self-interference in highly-integrated wireless transceivers is presented. Several examples of possible applications of this approach in a wireless cellular transceiver system-on-chip (SoC) are listed, and the application of one example is presented in detail. Mathematical analysis, simulation results, measurements, and implementation details are provided for the demonstrated technique, which was designed to minimize jitter induced onto the reference clock of a GSM transceiver's PLL. Excessive jitter on this clock, caused by multiple RF aggressors centered at harmonics of it, creates amplified in-band phase-noise at the RF output of the PLL, resulting in failures in the transmitter's performance. The identification of this highly complex interference mechanism, which represents a significant part of this work, is discussed in detail, as is the implemented solution. The presented phase-adjustment technique, leveraging specific features of the digitally intensive PLL and available digital-signal-processing resources, is demonstrated in a GSM system-on-chip (SoC) based on the Digital RF Processor (DRP) technology in 90 nm CMOS. As it does not involve dedicated hardware, nor does it noticeably increase the current consumption, it represents a cost-free solution in the final product.@en