Omer Bayraktar

Beam Switching Reflectarray Monolithically Integrated With RF MEMS Switches

A reflectarray antenna monolithically integrated with 90 RF MEMS switches has been designed and fabricated to achieve switching of the main beam. Aperture coupled microstrip patch antenna (ACMPA) elements are used to form a 10 × 10 element reconfigurable reflectarray antenna operating at 26.5 GHz. The change in the progressive phase shift between the elements is obtained by adjusting the length of the open ended transmission lines in the elements with the RF MEMS switches. The reconfigurable reflectarray is monolithically fabricated with the RF MEMS switches in an area of 42.46 cm2 using an in-house surface micromachining and wafer bonding process. The measurement results show that the main beam can be switched between broadside and 40° in the H-plane at 26.5 GHz.

Circumferential Traveling Wave Slot Array on Cylindrical Substrate Integrated Waveguide (CSIW)

Traveling wave slot array on cylindrical substrate integrated waveguide (CSIW) is designed, fabricated and measured at K-band. CSIW is formed by wrapping the substrate integrated waveguide (SIW) around the cylinder in the circumferential direction. 16 element longitudinal slot array on the broad wall of single CSIW is designed by the Elliots design procedure. The spacings between the slot elements are determined to reduce the half power beam width (HPBW) and to obtain good matching at 25 GHz. A 4 × 16 slot array is formed using 4 CSIW array each having 16 traveling wave longitudinal slots and the array is fed by 1 × 4 SIW power divider structure. About 10 ° beam steering is achieved when frequency is swept from 24 to 26 GHz. Gain of the antenna is 14 dB. Very good agreement between the simulated and measured results is obtained.

A Reconfigurable RF MEMS Triple Stub Impedance Matching Network

This paper presents a reconfigurable triple stub impedance matching network using RF MEMS technology centered at 10GHz. The device is capable of covering impedances on the whole Smith Chart. The device structure consists of three variable length stubs which are designed as distributed MEMS transmission lines and two lambdag/8 length CPW transmission lines connecting the stubs. The variable length stubs are implemented with 12 MEMS switches over CPW lines and CPW lines connecting the switches. lambdag/8 spacing between the stubs is selected to obtain a uniform distribution of the impedance points on the Smith Chart. Initial measurement results of the fabricated structure show a good agreement with the simulation results

Reconfigurable reflectarray using RF MEMS technology

This paper presents the design of a reconfigurable microstrip slot-coupled patch reflectarray using RF MEMS switches. The reflectarray is designed on two back-to-back bonded glass substrates front side of which contains the microstrip patch antenna elements and the backside contains the phase shifting elements. The phase shifting elements consist of microstrip lines the lengths of which are adjusted with MEMS switches resulting with adjustable phase characteristics of each antenna element. A transmission line based model is used to model the unit element of the array which is used to obtain a phase design curve and the design is verified with HFSS. The 4 × 1 array is then designed at 26 GHz to verify the phase design curve and according to the HFSS simulations, the main beam of the array is rotated by 14° by reconfiguring the length of the microstrip transmission lines with RF MEMS switches.

Slot array on curved substrate integrated waveguide

Longitudinal slot array on broad wall of substrate integrated waveguide (SIW) placed on cylindrical surface is designed at 25 GHz for conformal array applications where the SIW lies in the circumferential direction of cylinder.

Slots on cylindrical substrate integrated waveguide

Longitudinal slots and coupling between slots placed on the broad wall of a cylindrical substrate integrated waveguide (SIW) are modeled and characterized in order to design a slotted cylindrical SIW array. Characteristics of slot on the SIW bended on a cylindrical surface and effects of radius of curvature to the slot and mutual coupling characteristics are investigated at K band using FEM simulator.

Reconfigurable slot antenna with fixed-fixed beam type RF MEMS capacitors

This paper presents a reconfigurable dual-frequency rectangular slot antenna using MEMS technology. MEMS fixed-fixed beam type capacitors loading the antenna are actuated electrostatically to change the equivalent capacitance of the antenna which provides shift in the resonant frequencies. The measurement results show very good agreement with the simulation results and the resonant frequencies are shifted 1 GHz and 350 MHz continuously at around 8.5 GHz and 10.5 GHz, respectively.

Ka-band phased array antenna with circular rim

16 × 16 phased array antenna composed of microstrip antipodal tapered slot antenna elements is designed at Ka-band. The array element is designed by using infinite array simulations to approximate the mutual coupling effects to obtain good input match for various beam steering angles in the final array. A circular rim with ground plane is added to the final array to suppress grating lobes appear when the beam is steered. It is shown by simulations that grating lobe is suppressed to a level less than -20 dB at 35 GHz.

Cylindrical substrate integrated waveguide (CSIW) slot arrays with uniform and nonuniform spacings

Pattern synthesis of a traveling wave longitudinal slot array on the broad wall of cylindrical substrate integrated waveguide (CSIW) is presented at 25 GHz. In order to have low side lobe level (SLL) and high directivity, the Elliots design procedure for 1 × 25 slotted waveguide array is applied to satisfy the required slot voltage distribution found by aperture projection method for evenly distributed slot array with complex slot voltage distribution. The results are compared with the design which makes use of only the phase compensation of the resonant slots using non-uniform spacing to obtain high directivity. The advantages and disadvantages of both designs are compared in terms of the design procedure and electrical performance. CSIW array with nonuniform spacing has been fabricated and measured. Reasonable agreement between the simulation and measurement results is observed.

Investigation of On-Wafer TRL Calibration Accuracy Dependence on Transitions and Probe Positioning

This paper presents the effects of various transition types from the measurement plane to the reference plane in TRL calibration and probe positioning effects for on wafer measurements of CPW based devices. Fourteen different transition types, with direct, linear and exponential transitions, including 3 different variations of ground-signal-ground (GSG) spacing are examined. To observe the performance of the transitions, simple CPW transmission lines of different characteristic impedances are fabricated using standard lithography techniques on glass substrate and S-parameters are measured in 4.5-20 GHz band. Results are compared with electromagnetic simulations. The effects of probe misplacement along the lateral and horizontal axis are also investigated