J.-M. Duchamp

A Semi-Lumped Miniaturized Spurious Less Frequency Tunable Three-port Divider\Combiner with 20 dB Isolation Between Output Ports

We propose a new topology based on a semi-lumped complex impedance transformer for the design of a frequency tunable three-port power divider. A prototype has been realized in a hybrid technology with commercially available varactor diodes. Our design is based on an impedance transformer in the input branch (with electrical length of 20.4deg), and a loop in the output branches (with electrical length of 2times24deg). This leads to a miniaturized device, more than two times shorter than a classical Wilkinson power divider. This divider can be tuned over plusmn30% around 1.35 GHz (from 0.95 GHz to 1.75 GHz) with insertion loss lower than 0.3 dB, return loss better than 20 dB and isolation between the two output ports better than 20 dB. Moreover, the low-pass behavior of the input impedance transformer leads to a good rejection of the second harmonic

A compact tune-all bandpass filter based on coupled slow-wave resonators

A compact hybrid tune-all bandpass filter based on coupled slow-wave resonators is demonstrated. The performance of such a filter electronically tuned with commercially available low-cost semiconductor varactors is promising in terms of center-frequency (f/sub c/) and bandwidth wide continuous tunings. Indeed, the -3 dB bandwidth of this filter can be tuned between /spl sim/50 MHz and /spl sim/78 MHz for a /spl plusmn/ 18%-center-frequency tuning around 0.7 GHz, an insertion loss smaller than 5 dB and a return loss higher than 13 dB at the center frequency. Moreover, for a /spl sim/50 MHz fixed bandwidth, the center frequency can be tuned between 0.51 GHz and 0.81 GHz leading to a relative /spl plusmn/ 24%-center-frequency tuning. Finally, the total physical length of the prototype filter is about 0.27/spl lambda//sub c/ for a 0.7 GHz center frequency.

Low-Loss Paper Substrate for Printed High Efficiency Antennas at 2.45 GHz

In this letter, we present an innovative solution to achieve high efficiency printed antennas made on paper substrate. A corrugated cardboard is introduced for the first time for RF circuits. This substrate has been characterized with small perturbation method. It presents a dielectric constant of 1.41 and loss tangent of 0.042. Subsequently, patch antennas were realized on corrugated cardboard and classical paper substrate. A measured gain of 5.12 dBi is reached with corrugated cardboard compared to -3.24 dBi for classical paper. Simulation results show a good agreement with measurement.

Miniature DBR with series capacitive loading

A new miniature Dual Behavior Resonator (DBR) topology with capacitors placed in series between the feed lines and the stubs is demonstrated. Design equations are derived. For a proof-of-concept, a first-order prototype with a 1-GHz working frequency and 70 % size reduction is realized, measured and compared to a classical DBR. The design method is simpler and more accurate compared to a miniaturized DBR with capacitors connected at the end of the stubs. Hence, the agreement between simulation and measurement results is better than previously published results of a miniature DBR using capacitors at the end of the stubs. Results also point out a quality factor improvement of 12 %.

CPW on silicon substrates: propagation constant modeling and substrate free carriers contribution

We present a mixed approach associating Drudes and Heinrichs models for the modelling of attenuation and dispersion of coplanar waveguides. We investigate both single- and multi-layered substrates for which our approach is in good agreement with measurements. In the case of single-layered substrates, no adjustable parameter is required and we validate the model for both high and low resistivity silicon substrates.

Some rules for the choice of the C(V) characteristic for the design of frequency triplers with symmetrical varactors

In this paper we consider multipliers designed with varactors that have a symmetric C(V) capacitance-voltage characteristic, i.e. triplers, quintuplers, ... We show that for a tripler the optimal C(V) characteristic is not the most abrupt one, as stated in much works, but rather a cosine-like one. Our work is validated with the design of a frequency tripler based on the use of HBVs non-linear transmission lines. We obtained a significant improvement for the maximum conversion efficiency when a cosine C(V) is used instead of an abrupt one, for a 15 HBVs NLTL frequency tripler.

PIN diode characterization and modelling on SOI substrate for millimeter-wave applications

We present high frequency measurements, simulation and modeling of PIN diodes on silicon on insulator (SOI ) substrate from 40 MHz to 40 GHz and from 74 to 114 GHz. Comparison between simulations and measurements brings to the fore a frequency dependent PIN diode capacitance with reverse bias. We show that the free carriers injected in the diode intrinsic channel induce a frequency dependent complex permittivity of the silicon substrate that is responsible of the frequency behaviour of the PIN diode capacitance. Moreover, no adjustable parameter is required in this model as all the required parameters can be easily measured.

Comparison of Fully Distributed and Periodically Loaded Nonlinear Transmission Lines

Two different approaches to realizing nonlinear transmission lines (NLTLs) are compared in detail: those using fully-distributed and those employing periodically-loaded nonlinearities. Hetrostructure-barrier varactor measured characteristics are used as the nonlinear elements in the pulse-compression and harmonic-generation (20-60GHz tripler) simulations. We point out that the choice of simulation step size is critical in the case of fully-distributed NLTLs. It must be chosen so that no numerical Bragg cutoff frequency appears. For the frequency tripler, simulations show that with periodically loaded NLTLs, 21% efficiency at 210mW output power and 30% bandwidth can be obtained, whereas only 4.8% efficiency is possible using fully-distributed NLTLs. For pulse compression, the results are comparable but in the fully-distributed case the NLTL cannot be matched and significant reflections occur at the NLTL far end.