Browsing by Subject "Microwave circuits"

Now showing 1 - 6 of 6

Open Access
Low-voltage small-size double-arm MEMS actuator
(2009) Bıyıklı, Necmi; Damgaci, Y.; Cetiner, B.A.
The fabrication and characterisation of a double-arm cantilever-type metallic DC-contact MEMS actuator with low pull-down voltage are reported. Bi-layer TiW cantilevers with an internal stress gradient were fabricated using a microwave-compatible fabrication process. Owing to its small size, cantilever length (L=5-50m) and width (W=2-40m), i.e. ∼10-100 times smaller in lateral dimensions than a standard MEMS actuator, this actuator showed actuation voltages lower than 10 V. RF measurements of the 10m-wide actuators yielded an average insertion loss less than 1dB and isolation higher than 40dB up to 25GHz. The developed actuator is well suited for integration in reconfigurable microwave circuits and systems such as reconfigurable antennas and arrays. © 2009 The Institution of Engineering and Technology.
Open Access
A new method for the steady-state analysis of periodically excited nonlinear circuits
(Institute of Electrical and Electronics Engineers, 1996-12) Celik, M.; Atalar, Abdullah; Tan, M. A.
We propose a new method for the steady state analysis of periodically excited nonlinear microwave circuits. It is a modified and more efficient form of Newton-Raphson iteration based harmonic balance (HB) technique. It solves the convergence problems of the HB technique at high drive levels. The proposed method makes use of the parametric dependence of the circuit responses on the excitation level. It first computes the derivatives of the complex amplitudes of the harmonics with respect to the excitation level efficiently and then finds the Pade approximants for the amplitudes of the harmonics using these derivatives.
Open Access
Novel SIW based interdigital bandpass filter with harmonic suppression
(IEEE, 2014) Kurudere, S.; Ertürk, Vakur B.
A novel configuration for substrate integrated waveguide (SIW) based bandpass filter with interdigital type resonators is presented. In the proposed structure, interdigital type resonators consisting of vias and circular caps at top of them are combined into a bowtie SIW structure. SIW is fed by a tapered microstrip line transition providing low loss and good matching. In order to improve harmonic suppression performance of the filter, the dumbbell shaped defected ground structure (DGS) is etched to the ground side of the microstrip line feeding section. The proposed filter structure is put in a conducting box in order to improve attenuation levels at the band edges and prevent radiation to the outside. The prototype is designed at 9 GHz center frequency with 500 MHz bandwidth, analyzed and fabricated for verification. The measurement results are in good agreement with the simulations, and the filter exhibits more than 30 dB harmonic suppression.
Open Access
Pole-zero computation in microwave circuits using multipoint Padé approximation
(Institute of Electrical and Electronics Engineers, 1995-01) Celik, M.; Ocali, O.; Tan, M. A.; Atalar, Abdullah
A new method is proposed for dominant pole- zero (or pole-residue) analysis of large linear microwave circuits containing both lumped and distributed elements. The method is based on a multipoint Padé approximation. It finds a reduced-order rational s-domain transfer function using a data set obtained by solving the circuit at only a few frequency points. We propose two techniques in order to obtain the coefficients of the transfer function from the data set. The proposed method provides a more efficient computation of both transient and frequency domain responses than conventional simulators and more accurate results than the techniques based on single-point Padé approximation such as asymptotic waveform evaluation.
Open Access
SIW‐based interdigital bandpass filter with harmonic suppression
(John Wiley and Sons Inc., 2015) Kurudere, S.; Ertürk, V. B.
A novel configuration of interdigital bandpass filter based on the substrate integrated waveguide (SIW) technology is proposed. In addition to the interdigital resonators in SIW that determine the main response/characteristics of the filter, narrowing the width of the SIW at the center of the filter and additional vias at its input and output parts act as two additional control mechanisms to achieve the desired filter response. Moreover, dumbbells are etched to the ground side of the microstrip feeding sections at both ends of the filter to improve its harmonic suppression. A prototype filter is designed and fabricated for verification. The measured results are in good agreement with the simulations, and the filter exhibits very good harmonic suppression. © 2015 Wiley Periodicals, Inc.
Open Access
Using phase relations in microstrip directional couplers to achieve high directivity
(2013) Tas, V.; Atalar, Abdullah
We analyze the microstrip directional couplers with a special focus on the phase difference between the coupled and isolated ports. The analysis uses the even-odd mode decomposition technique and network theory. The results show that the phase difference between the signals at the coupled port and the isolated port is close to \pi in a very wide band. This property can be used to achieve a broadband directivity by inducing a voltage cancellation at the isolated port of the couplers. Two different cancellation methods are investigated. Analytical formulas for the required component values of both methods are given. Higher directivity can be obtained at the expense of reduced bandwidth.