Masoud Koochakzadeh

Tunable Filters With Nonuniform Microstrip Coupled Lines

A basic wideband tunable filter design based on combline topology is presented. At the presence of the parasitic effects, the structure of the filter must be modified by introducing additional degrees of freedom to the geometry of the coupled line segment. A design procedure involving iterative steps will be described. This procedure is used to design two bandpass filters with more than one octave tuning range in the UHF band. The experimental results are presented for the filter prototypes implemented using printed circuit boards and PIN diodes.

Miniaturized Transmission Lines Based on Hybrid Lattice-Ladder Topology

This paper introduces hybrid structures with unit cells that are a combination of lattice and ladder topologies. These unit cells dramatically increase the quality factor, miniaturization, and maximum frequency of synthetic transmission lines. Also, it is shown that lattice topologies in general are less vulnerable to the effect of parasitics, such as self resonance of loading capacitors or mutual inductance between different cells. The underlying theory is studied, and simple formulas are given for predicting the behavior of these lines. A few examples are presented that, based on full-wave simulations, show the large gain in miniaturization, quality factor, or bandwidth compared to the simple ladder or lattice structures. Measured results for a fabricated synthetic line are presented that show a miniaturization factor of n=¿{¿eff¿eff}=16.5 for Z 0=50 ¿ and a very small dispersive behavior from dc to 2.5 GHz.

Switchable Bandpass Filter for 0.3-0.6 GHz

A switchable filter topology is proposed in the form of a self-scalable comb-line structure. This topology is capable of implementing a tunable frequency response with consistent performance over very large tuning ranges. A two-pole prototype has been fabricated using 10 discrete PIN diodes and is capable of covering the frequency range of 290 to 600 MHz in four steps (2-bit tuning). The in-band loss of the filter is better than 2 dB for all modes when a DC voltage of 5 V is used for biasing the PIN diodes. The filter has a IIP3 of greater than 32 DBR, and its RF structure occupies an area of 9 times 21 mm2.

Multi-scale tunable filter covering a frequency range of 6.5:1

A multi-scale filter topology is proposed in the form of a switched comb-line structure loaded by varactors. This topology is capable of implementing a tunable frequency response with consistent performance over very large tuning ranges. Two prototype filters of orders two and four have been fabricated in a coplanar geometry. The filters are tunable in a 6.5:1 frequency range.

A multi-resolution channel-select filter with ultra-wide frequency coverage

A multi-resolution channel select filter topology is proposed for ultra-wideband coverage, as the multi-stage cascade of bimodal filters with self-complementary periodic frequency response. A 4-stage implantation based on PIN diode switches is presented. This prototype covers DC-2.5 GHz in 16 equal bandwidth channels of 156 MHz with a maximum insertion loss of 6.5 dB.

Closed-Form Formulas for Predicting the Nonlinear Behavior of All-Pole Bandpass Filters

The nonlinear behavior of the all-pole passive bandpass filters close to their center frequency is studied using first-order approximations. The focus of this study is on approximate calculation of third-order intermodulations through an iterative process, and it is shown that it can be generalized to higher order effects. Nonlinearities in both resonators and inverters are considered. Simple formulas are given to calculate the effect of individual elements in the overall response in lossless and lossy filters. It is shown that the presence of loss will increase the third-order intermodulation intercept point of the filter, while it usually decreases the output third-order intercept point. In comparison to the nonlinear resonators, the relative effect of nonlinear inverters is larger; however, the losses of the inverters are found to have a smaller effect on the nonlinear response. Finally, simple formulas are given to predict the changes in the center frequency due to the reactive effects of the nonlinearities. In all cases, the analytical results are verified through comparison with harmonic balance simulations.

Multiresolution Channel-Select Filter With Ultrawide Frequency Coverage

A multiresolution channel select filter topology is proposed for implementing a digitally-tunable bandpass response with ultra-wideband tuning range. This filter is composed of a chain of bimodal filter stages with self-complementary periodic frequency response. The frequency response behavior of this filter, the effect of parasitics, and the nonlinearities are studied in detail. A four-stage implementation is presented which is based on p-i-n diode switches and covers dc-2.5 GHz in 16 equal bandwidth channels with a maximum insertion loss of 6.7 dB.

Design of band-select filters with arbitrary characteristics using overlapped loaded line topologies

The design of a new class of band-select filters is proposed. For operation between the load and source impedances of Z0 Ω, the filter is composed of a carrier line of the same impedance that is loaded by capacitors and inductors. The choice of active inductors and capacitors enables the band-select filtering. The frequency response characteristics for each band are independent of the rest of the bands, and therefore the proposed topology is suitable for multi-band designs with many degrees of freedom. Two different examples of this topology are presented.

Elastic Modes of an Anisotropic Ridge Waveguide

A semi-analytical method for finding the elastic modes propagating along the edge of an anisotropic semi-infinite plate is presented. Solutions are constructed as linear combinations of a finite number of the corresponding infinite plate modes with the constraint that they decay in the direction perpendicular to the edge and collectively satisfy the free boundary condition over the edge surface. Such modes that are confined to the edge can be used to approximate solutions of acoustic ridge waveguides whose supporting structures are sufficiently far away from the free edge. The semi-infinite plate or ridge is allowed to be oriented arbitrarily in the anisotropic crystal. Modifications to the theory to find symmetric and antisymmetric solutions for special crystal orientations are also presented. Accuracy of the solutions can be improved by including more plate modes in the series. Numerical techniques to find modal dispersion relations and orientation dependent modal behavior, are discussed. Results for ridges etched in single crystal Silicon are found to be in good agreement with Finite Element simulations. It is found that variations in modal phase velocity with respect to crystal orientation are not significant, suggesting that anisotropy may not be a critical issue while designing ridge waveguides in Silicon.

A sub-resonant 40GHz clock distribution network with near zero skew

A sub-resonant mm-wave clock distribution network is presented. The proposed solution introduces near zero skew while consumes significantly less power than alternative approaches such as mesh networks. The clock distribution network was implemented using the TSMC 40nm LP CMOS process and measured using a 4-port vector network analyzer. It measures sub-psec skew from 36.6 to 40.2GHz with less than 20% power penalty compared to resonant solutions.