Blake Gray

Analytical Modeling of Microwave Parametric Upconverters

Parametric amplification is a well-studied phenomenon by which a nonlinear reactance mixes an RF large-signal (pump) with an IF small-signal (source) to generate mixing products with gain. In this paper, two analytical models are derived and validated that predict limitations in the gain and efficiency of a parametric upconverter associated with varactor tuning range and quality factor. The analytical models are validated by circuit simulations and by two breadboard upconverters.

Behavioral modeling and simulation of a parametric power amplifier

Parametric amplification is a well known technique for achieving power gain at microwave frequencies. By modulating a nonlinear reactance using a large (pump) signal, a smaller (source) signal is up-converted with gain. The ideal gain predicted by the Manley-Rowe relations are theoretically limited by the ability to suppress the pump signal and unwanted mixing products of the nonlinear reactance. When using ideal nonlinear reactances (i.e. infinite Q) parametric amplification is lossless, resulting in 100% conversion efficiency of the pump signal power to the desired mixing product. In this paper we develop a behavioral model to predict limitations in gain driven by changes in a nonlinear capacitance, which enables practical circuit design. The model is validated by circuit simulations, and by a breadboard parametric mixer.

A Broadband Double-Balanced Phase-Coherent Degenerate Parametric Amplifier

A broadband double-balanced phase-coherent degenerate parametric amplifier is presented that provides an average gain of 26 dB over 1 GHz of usable bandwidth centered at 650 MHz. A prototype board was constructed, and its measured and simulated data match well with one another. Using a harmonic-balance simulator, the stability of the amplifier was analyzed by observing the evolution of the system poles as both the pump power level and the temperature of operation varied.

Microdegree frequency and phase difference control using fractional-N PLL synthesizers

Two independently programmable on-chip delta-sigma fractional-N phased-locked loop (PLL) synthesizers were developed in 65 nm CMOS with a total die size of 2 mm × 2 mm to demonstrate a millidegree phase shifter. Both PLLs use a 24 bit fractional modulator, thus a theoretical phase shift as small as 21 microdegrees is possible. Due to limitations in the noise floor at microwave frequencies, data was collected at postdivided frequencies 50 MHz and 400 MHz resulting in a best case measured phase step of 21 millidegrees at 50 MHz with a high degree of measurement certainty.

Optical projection and image processing approach for mine wall monitoring

Wall movement in an underground mine must be continually monitored to provide real-time assessment of dynamic stress changes around mining excavation and to warn against rock failure. An in situ approach using optical spot projection and image processing can measure submillimeter movements. The system can be easily automated and poses no obstruction to mine traffic. The position of an off-normal laser spot will shift as the target wall moves. The centroid of this projected spot can be measured through image processing of a digital image. Multiple laser spots give the system simultaneous information over a larger sampled area. Software processing can measure subpixel shifts of the spot centroid. The resolution depends on the pixel count, the magnification of the camera lens (and hence the field of view), the optical-beam angle, and the spot characteristics. A laboratory table-top experiment demonstrated the system for distances up to 3 m and for a resolution of 0.1 mm. The results were linear in target movement, with standard errors between 0.83% and 5.38%. An automated system is described for a mine environment.

Analytical modeling of transducer gain and gain compression in degenerate parametric amplifiers

Analytical models accurately describing transducer gain and gain compression of degenerate parametric amplifiers are presented. To validate the models, a prototype broadband double-balanced phase-coherent degenerate parametric amplifier was constructed that provides an average gain of 26 dB over 1 GHz of usable bandwidth centered at 650 MHz. The analytical models agree with measured data over a wide range of operating conditions.

In-depth stability analysis of degenerate parametric amplifiers

A relevant instability phenomenon in degenerate parametric power amplifiers is the division by two of the pump frequency. Because of the existence of an input source at the same frequency of the instability, the degenerate parametric power amplifier will exhibit a specific bifurcation behavior, inherent to this type of circuit. The anomalous shape of the solution curves with high slope and generation of new paths will be associated with an imperfect Pitchfork bifurcation. Its understanding will be essential for a proper interpretation of the simulated and measured results. For illustration, a global stability analysis of a broadband phase-coherent degenerate parametric amplifier is presented. Good agreement has been obtained with the measurement results.

Phase-locked loop design with SPO detection and charge pump trimming for reference spur suppression

As an important factor for long-term jitter in clock synthesis and distribution, reference spurs result from circuit mismatch and nonlinear effects that induce periodic perturbations in phase-locked loops (PLLs). In this paper, a PLL with built-in static phase offset (SPO) detector and charge pump current trimming for self-calibration circuits is proposed. By adjusting the charge pump current ratio determined by an SPO detector, minimum and maximum improvements of 12dB and 22.99dB in reference spur suppression can be achieved. The best improvement reduces the integrated jitter by 10% over a 10kHz to 10MHz bandwidth. The technique is demonstrated for a PLL output frequency from 400 MHz to 1 GHz. The ring oscillator based PLL is designed with 200 KHz bandwidth and 70 degree phase margin. Measurement results from chips across different corners are provided to verify the calibration technique.

A Phase-Coherent Upconverting Parametric Amplifier

A phase-coherent negative-resistance upconverting parametric amplifier is presented that upconverts to three times the source input frequency and exhibits over 600 MHz, or 33%, fractional usable bandwidth at the upconverted output. An analytical model for the transducer gain is presented, enabling an initial selection of the termination resistors and pump signal. A prototype board was constructed and measured data matches well with both simulated results and those predicted by the analytical model. Simulations, measurements, and the analytic derivation demonstrate that when the source and pump frequencies are phase coherent, it is possible to achieve a transducer gain greater than the theoretical limit imposed by the Manley-Rowe relations for phase-incoherent upconverters.