Saswata Basu

An SOLR calibration for accurate measurement of orthogonal on-wafer DUTs

Orthogonal CPW thrus are notorious for generating undesired modes due to the bend discontinuity. These undesired modes are not accounted for in conventional calibration methods such as SOLT, LRM, and TRL, since they require, by definition, well-behaved thru standards. In this paper, we will demonstrate through experimental results how the Short-Open-Load-Reciprocal thru (SOLR) approach, which avoids imposing any dependency on the nature of the thru standard itself, provides a superior calibration.

Design and performance of a planar star mixer

This paper describes the realization of a hybrid star mixer as a planar circuit. The mixer has a minimum conversion loss of 5 dB and, for a conversion loss of less than 9 dB, spans over 2.2 GHz in IF bandwidth and 8 GHz in RF/LO bandwidth. The mixer employs a novel, planar balun structure, similar to conductor-backed CPW, that is suitable for realization as a monolithic circuit. >

Stability analysis for large signal design of a microwave frequency doubler

Microwave circuits such as frequency doublers are notorious for instabilities under parametric variation. The instabilities manifested in the doubler are due to the minority carrier lifetime of the pn junction diode. They are calculated using a simpler stability formulation. A global stability chart is computed using a novel technique called the piecewise stability analysis (PSA) method and found to be in close agreement with the experimental values. These instabilities are characterized by secondary Hopf bifurcations and their eventual breakdown to chaos has been observed. The onset of Hopf bifurcation has been verified both experimentally and numerically.

A membrane quadrant probe for R&D applications

Membrane probes are known for their applications to production probing and their ability to integrate RF lines, matching networks and good power supply bypassing for known good die testing on-wafer. Nonetheless, they require die-specific design and are not reconfigurable. In this paper, we discuss a quadrant probe based on membrane technology which offers this alternative with lower loss than membrane probes and better DC bypassing capability than any other quadrant probe.

Impedance Matching Probes for Wireless Applications

This work describes the motivation, technology, design, and performance of impedance matching probes that address the needs of wireless applications. The impedance matching solution can be implemented in two distinctly different technologies, air-coplanar and thin-film membrane. Impedance matched probes offer improved load-pull characterization of power, gain and efficiency, and accurate characterization of devices with non-standard impedances.

Experimental and numerical verification of the cause of Hopf bifurcation in a microwave doubler

The appearance of Hopf bifurcation in a microwave doubler is due to the relative speed of the recombination delay of the junction diode with the input RF signal, which results in a dynamical negative resistance. This is verified here experimentally by using a back-to-back diode structure that quenches Hopf bifurcation numerically through stability analysis in the frequency domain. >

Quasi-periodic route to chaos in a microwave doubler

Quasi-periodic route to chaos was observed as the bias level was increased in a 5-10 GHz frequency doubler. The appearance of spurious oscillations is a consequence of the dynamical negative resistance manifested by the p-n junction diode in the doubler. This phenomenon is caused by the long minority carrier recombination time of the junction diode compared to the period of the input signal. >

Piecewise stability analysis in microwave circuits

A novel method for analyzing the global stability of microwave circuits under multi-parameter variation is presented. In this method, an arbitrary linear circuit is divided up into subcircuits containing parametric elements and a fixed linear circuit. This approach improves the computational efficiency by eliminating the need for recalculation of the Y-parameters of the fixed part of the linear circuit. >

Predicting the onset of instabilities in frequency multipliers

Microwave multipliers are notoriously unstable with input power, bias and load variations. In this paper, we predict the onset of a chaotic type of instability using the Hopf bifurcation concept as the input power level is increased. The measurement and the predicted theoretical results are in agreement to within 1.5 dB.<<ETX>>

A Membrane Probe for Testing High Power Amplifiers at mm-Wave Frequencies

Traditional coaxial-needle probe cards have difficulty in incorporating combiner structures and generally have poor bypassing capability at high frequencies. In this paper, we will demonstrate how membrane probes can incorporate these features with minimal parasitic effects and conduct accurate and fast testing of power amplifiers at Ka-band.