| 1. |
|
|
| 2. |
- Farjana, Sadia, 1983, et al.
(författare)
-
Dry film photoresist-based microfabrication : A new method to fabricate millimeter-wave waveguide components
- 2021
-
Ingår i: Micromachines. - : MDPI AG. - 2072-666X. ; 12:3
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a novel fabrication method based on dry film photoresists to realize waveguides and waveguide-based passive components operating at the millimeter-wave frequency (30–300 GHz). We demonstrate that the proposed fabrication method has a high potential as an alternative to other microfabrication technologies, such as silicon-based and SU8-based micromachining for realizing millimeter-wave waveguide components. Along with the nearly identical transfer of geometrical structures, the dry film photoresist offers other advantages such as fewer processing steps, lower production cost, and shorter prototyping time over the conventional micromachining technologies. To demonstrate the feasibility of the fabrication process, we use SUEX dry film to fabricate a ridge gap waveguide resonator. The resonator is designed to exhibit two resonances at 234.6 and 284 GHz. The measured attenuation at 234 GHz is 0.032 dB/mm and at 283 GHz is 0.033 dB/mm for the fabricated prototype. A comparative study among different existing technologies indicates that the reported method can give a better unloaded Q-value than other conventional processes. The measured unloaded Q-values are in good agreement with the simulated unloaded Q-values. The signal attenuation indicates that SUEX dry film photoresists can be used to fabricate passive devices operating at millimeter-wave frequencies. Moreover, this new fabrication method can offer fast and low-cost prototyping. © 2021 by the authors.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Alavian Ghavanini, Farzan, 1978, et al.
(författare)
-
A method to evaluate MEMS bonding
- 2006
-
Ingår i: Micro Structure Workshop 2006. ; 1:1, s. 47-B3d
-
Konferensbidrag (refereegranskat)
|
|
| 6. |
- Alavian Ghavanini, Farzan, 1978, et al.
(författare)
-
An easy-to-implement method for evaluation of capacitive resonant sensors
- 2006
-
Ingår i: Journal of Micromechanics and Microengineering. - 1361-6439 .- 0960-1317. ; 16:6, s. s156-s160
-
Tidskriftsartikel (refereegranskat)abstract
- A novel method that can be used to characterize resonant capacitive sensors is presented. The method is based on measurement of the third harmonic of the current through the capacitor; thus the detection signal is frequencyseparated from the excitation signal. The measurement is time-continuousand only requires a very simple resonant structure where a single electrode is simultaneously used for excitation and detection. The readout circuit iseasily implemented with a single operational amplifier and standard equipment such as a lock-in amplifier or a function generator and a spectrum analyzer. Measurements of a resonant structure confirm the feasibility of the concept.
|
|
| 7. |
|
|
| 8. |
- Amin, Muhammad, 1979, et al.
(författare)
-
Coin-cell Supercapacitors Based on CVD Grown and Vertically Aligned Carbon Nanofibers (VACNFs)
- 2017
-
Ingår i: International Journal of Electrochemical Science. - : Elsevier BV. - 1452-3981. ; 12:7, s. 6653-6661
-
Tidskriftsartikel (refereegranskat)abstract
- Complete supercapacitors (SCs) comprising vertically aligned carbon nanofibers (VACNFs) as electrode materials have been assembled as coin-cells. The VACNFs were grown directly onto the current collector by direct current plasma enhanced chemical vapor deposition (DC-PECVD), thereby providing excellent contact with the current collector, but also eliminating the need of any binder. The vertical alignment facilitates fast ion transport and the electrolyte to access the entire surface of the CNFs. The morphology of the VACNFs was evaluated by scanning electron microscopy (SEM), while the performance was assessed by several methods: cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and device related cycling by galvanostatic charge/discharge. The capacitance, 3.64 mF/cm2 , is >15 times higher than the capacitance of a coin-cell without CNFs and the cyclic performance shows these proof-of-concept SCs to retain >80% of the capacitance after 2000 full charge/discharge cycles. The direct growth of VACNFs as electrodes at the current collector opens pathways for SC production using existing coin-cell battery production technology.
|
|
| 9. |
- Farjana, Sadia, 1983, et al.
(författare)
-
Micromachined Ridge Gap Waveguide Transmission Line and Transition at 220-310 GHz
- 2021
-
Ingår i: 2021 IEEE International Symposium on Antennas and Propagation and North American Radio Science Meeting, APS/URSI 2021 - Proceedings. - 9781728146706 ; , s. 1297-1298
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a vertical wideband transition between a standard WR-3.4 rectangular waveguide (RW) and ridge gap waveguide (RGW) operating at 220-310 GHz. To achieve a wideband impedance matching a capacitive stub is used instead of multiple steps in the ridge section to reduce the manufacturing complexity. The designed back-to-back transition is fabricated with SUEX dry film photoresist. The attractive features of the designed transition are simplicity and high tolerances to manufacturing errors, without compromising the wideband performance. The measurement results of the fabricated prototype show good agreement with simulations over the frequency band of interest and the measured average insertion loss is 0.075 dB/mm and the measured input reflection coefficient is below -12 dB for the back-to-back structure. Measurement results indicate that SUEX dry film photoresist is a suitable material to fabricate waveguide components operating at and above the millimeter-wave range.
|
|
| 10. |
- Kabir, Mohammad, 1974, et al.
(författare)
-
A Test Vehicle for RF/DC Evaluation and Destructive Testing Of Vertically Grown Nanostructures (VGCNS)
- 2011
-
Ingår i: Proceedings of the NT11 International Conference on the Science and Application of Nanotubes, Cambridge, UK, July 10-16, 2011.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We have developed an RF test vehicle suitable for measuring DC and microwave performance of vertically grown carbon nanostructures (VGCNS) as via-interconnects. A first version of the interconnect test vehicles devices were designed, fabricated and characterized. The RF small signal (S-parameter) and large signal measurements show that carbon nanofibres can be used as interconnects in microwave circuit, even for power devices. The design of test vehicle employs a three metal layer concept, forming sequentially the ground, signal and device under test structures for characterization in a microstrip configuration. The structures as such consisted of interconnects of dimensions ranging from 50 nm to 100 µm diameter made of VGCNS. In the first version of the interconnect test vehicles, the interconnects were made of carbon nanofibers grown at 450 C. From SEM measurement we found that the resulting height was around 1.5-2 µm. Epoxy polymer SU-8 was employed by spinning on the device and a subsequent etch back process was carried out to open up the tip of the fibres to connect to consecutive interconnects with the third metallisation layer. After growing the nanofibres, it was observed, using SEM, that interconnect sizes smaller than 10 µm diameter suffered from parasitic growth and therefore the effective device dimension deviated from the initial design. We carried out small signal measurements using a vector network analyser for frequency ranging from 1 to 25 GHz, in order to characterise the transmission and reflection/absorption of the devices as function of their diameter size. The large signal evaluation was performed by measuring the gain compression of the devices. In addition destructive tests, aiming at testing the current carrying capability of the interconnect, have also been performed.The resistivity of interconnects was measured to vary varies from 0.2 µΩ·mm-1.3 mΩ·mm. Apparently, the device performance is considerably influenced by the fill factor of the interconnect with VGCNS. Small variations in fill factor (in %) provided a large variations in device resistivity. Furthermore, it was also observed that the resistance drops at higher power levels. RF conductivity of interconnects ranges from 5x10^3 S/m to 7x10^5 S/m. The average input power before interconnect destruction is larger than 25W with effective device diameter ranging from 3 µm to 100 µm interconnects. In addition, the average gain compression before interconnect destruction was found to be 0.6 dB. It was not possible to extract the conductivity value of an individual nanofiber using comparison to simulation data, since the devices might have suffered from parasitic growth as well as pinhole metal diffusion during top metal contact formation. This certainly affects the actual device dimension and properties. Nevertheless, the proof of concept of design and manufacturing a test vehicle for RF measurements of vertically grown nanostructures was achieved. We will report the findings and anomalies in the measured devices. Further improvement is expected in the coming test vehicle version.
|
|
