| 1. |
- Ahmad, Ashfaq, et al.
(författare)
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Design, Fabrication, and Measurements of Extended L-Shaped Multiband Antenna for Wireless Applications
- 2018
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Ingår i: Applied Computational Electromagnetics Society Journal. - : Applied Computational Electromagnetics Society (ACES). - 1054-4887. ; 33:4, s. 388-393
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Tidskriftsartikel (refereegranskat)abstract
- This article expounds a multi-band compact shaped antenna, which is based on CPW ground plane. FR-4 with a thickness of 1.6 mm is used as a substrate for the proposed antenna. The proposed antenna is capable of operating at 1.56 GHz for (Global Positioning System), 2.45 GHz (Wireless Local Area Network) and 4.49 GHz (Aeronautical Mobile Telemetry (AMT) fixed services). The efficiency at 1.56, 2.45, and 4.49 GHz is 79.7, 76.9 and 76.7%, respectively. The VSWR of the presented antenna is less than 1.5 at all the desired resonance modes, which confirms its good impedance matching. The performance of the proposed antenna is evaluated in terms of VSWR, return loss, radiation pattern and efficiency. CST (R) MWS (R) software is used for simulations. In order to validate the simulation results, a prototype of the designed antenna is fabricated and a good agreement is found between the simulated and measured results.
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| 2. |
- Ahmad, Ashfaq, et al.
(författare)
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Flexible and Compact Spiral-Shaped Frequency Reconfigurable Antenna for Wireless Applications
- 2020
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Ingår i: IETE Journal of Research. - : TAYLOR & FRANCIS LTD. - 0377-2063 .- 0974-780X. ; 66:1, s. 22-29
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Tidskriftsartikel (refereegranskat)abstract
- A flexible, spiral-shaped frequency reconfigurable antenna with a compact size (20 x 24 mm(2)) is presented. The proposed antenna has a low-profile planar structure and is able to operate at five different frequency bands, i.e., 4.19-4.48, 5.98-6.4, 3.42-4.0, 5.4-5.68, and 6.8-7.0 GHz. The multiband operation enables the antenna to cover aeronautical radio navigation, fixed satellite communication, WLAN, and WiMAX standards. A radiating element is backed by Rogers (R) 5880 substrate with a thickness of 0.508 mm and dielectric constant of 2.2. The spiral shape is achieved by introducing different strips. Frequency reconfiguration is achieved by the incorporation of a lumped element in a strip, so that the antenna can switch between different resonances. To validate the performance of the antenna, the prototype of the design was fabricated and tested. Good acquiescent is seen between simulated and measured results. The proposed antenna operates efficiently with appreciable return loss, directivity, bandwidth, and peak gain.
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| 3. |
- Ahmad, S. A., et al.
(författare)
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Penta-band antenna with defected ground structure for wireless communication applications
- 2019
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Ingår i: 2019 2nd International Conference on Computing, Mathematics and Engineering Technologies, iCoMET 2019. - : Institute of Electrical and Electronics Engineers Inc.. - 9781538695098
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Konferensbidrag (refereegranskat)abstract
- This work proposes a compact, penta-band, slotted antenna with Defected Ground Structure (DGS). The proposed multiband resonator is intended for integration into microwave circuits and portable RF portable devices. The prototype with spurlines and DGS is designed on thin Rogers RT Duroid 5880 substrate having thickness 0.508 mm. The presented radiator is capable to cover the frequency bands 2.46-2.59 GHz, 2.99-3.78 GHz, 5.17-5.89 GHz, 6.86-7.36 GHz, 9.38-11 GHz. The impedance bandwidths of 5.24%, 23.68%, 12.8%, 7.24% and 16.08% is obtained for the covered frequency bands respectively. The antenna proposed in this work thus supports WLAN, WiMAX, ISM, LTE, Bluetooth, C-band and X-band applications. The radiator attains 4.2 dB peak gain. It is apparent from the radiation performance of the prototype, that it is an effective candidate for current and forthcoming multiband wireless applications.
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| 4. |
- Ahmad, Waqar, et al.
(författare)
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Decoupling capacitance for the power integrity of 3D-DRAM-over-logic system
- 2012
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Ingår i: IEEE 13th Electronics Packaging Technology Conference (EPTC), 2011. - : IEEE conference proceedings. - 9781457719813 ; , s. 590-594
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Konferensbidrag (refereegranskat)abstract
- The 3D-DRAM stacked over the processor is a vibrant technique in order to overcome the memory wall as well as the bandwidth wall problems. We considered a system with two DRAM dies over a single processor die. We assumed the decoupling capacitors to be placed on each DRAM die and connected to the power distribution TSV pairs, where the TSVs pass through the DRAM stack. In this paper we proposed a mathematical model for the optimum value of the decoupling capacitance on each DRAM die along with the optimum values of the effective resistance of the interconnecting power distribution TSV pairs in order to ensure the power integrity of the logic load during switching. The proposed model has a maximum of 1.1% error as compared to the Ansoft Nexxim4.1.
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| 5. |
- Ahmad, Waqar, et al.
(författare)
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Fast Transient Simulation Algorithm for a 3D Power distribution Bus
- 2010
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Ingår i: Proceedings of IEEE Asia Symposium on Quality Electronic Design. ; , s. 343-350
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Konferensbidrag (refereegranskat)abstract
- Extensive transient simulations for on-chip power delivery networks are required to analyze power delivery fluctuations caused by dynamic IR and Ldi/dt drops. Speed and memory has become a bottleneck for simulation of power distribution networks in modern VLSI design where clock frequency is of the order of GHz. The traditional SPICE based tools are very slow and consume a lot of memory during simulation. The problem is further aggravated for huge networks like power distribution network within a stack of ICs inter-connected through TSVs. This type of 3D power distribution network may contain billions of nodes at a time. In this paper we proposed a faster transient simulation algorithm using visual C++. First we reduce 3D power distribution bus containing n nodes to a two terminal 7 network. Then we solve this two terminal reduced network for voltages and currents. After this, we apply back solving algorithm to the network to solve it for each of the intermediate nodes using visual C++. The proposed algorithm is quite accurate with 1-2% error when compared with Ansoft Nexxim4.1. The proposed algorithm is several times faster than Ansoft Nexxim as well as consumes significantly less memory as compared to Nexxim.
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| 6. |
- Ahmad, Waqar, et al.
(författare)
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Modeling of peak-to-peak core switching noise, output impedance, and decoupling capacitance along a vertical chain of power distribution TSV pairs
- 2012
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Ingår i: Analog Integrated Circuits and Signal Processing. - : Springer Science and Business Media LLC. - 0925-1030 .- 1573-1979. ; 73:1, s. 311-328
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Tidskriftsartikel (refereegranskat)abstract
- In this article we propose an efficient and accurate model to estimate peak-to-peak core switching noise, caused by simultaneous switching of logic loads along a vertical chain of power distribution TSV pairs in a 3D stack of dies interconnected through TSVs. The proposed model is accurate with only a 2–3% difference in peak-to-peak core switching noise as compared to the Ansoft Nexxim4.1 equivalent model. The proposed model is 3–4 times faster than Ansoft Nexxim4.1 and uses two times less memory as compared to the Ansoft Nexxim4.1 equivalent model. In this article we also thoroughly establish design guidelines for almost flat output impedance magnitude at each stage of a vertical chain of power distribution TSV pairs to realize a resonance free scenario over a wide operating frequency range. We also establish decoupling capacitance design guidelines based on the optimum output impedance and critically damped supply voltage for the core logic for each stage of a vertical chain of power distribution TSV pairs.
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| 7. |
- Ahmad, Waqar, et al.
(författare)
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Modeling of peak-to-peak switching noise along a vertical chain of power distribution TSV pairs in a 3D stack of ICs interconnected through TSVs
- 2010
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Ingår i: 28th Norchip Conference, NORCHIP 2010.
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Konferensbidrag (refereegranskat)abstract
- On-chip power supply noise has become a bottleneck in 3D ICs as scaling of the supply network impedance has not been kept up with increasing device densities and operating currents with each technology node due to limited wire resources. In this paper we proposed an efficient and accurate model to estimate peak-to-peak switching noise, caused by simultaneous switching of logic loads along a vertical chain of power distribution TSV pairs in a 3D stack of ICs. The proposed model is quite accurate with only 2-3% difference from Ansoft Nexxim4.1 equivalent model. The proposed model is 3-4 times faster than Nexxim4.1 as well as consumes two times less memory as compared to Nexxim4.1equivalent model. We analyzed peak-to-peak switching noise along a vertical chain of power distribution TSV pairs by varying physical dimensions of TSVs and value of decoupling capacitance. We also thoroughly investigated the peak-to-peak noise sensitivity to TSV effective inductance and decoupling capacitance.
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| 8. |
- Ahmad, Waqar, et al.
(författare)
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Peak-to-Peak Ground Noise on a Power Distribution TSV Pair as a Function of Rise Time in 3-D Stack of Dies Interconnected Through TSVs
- 2011
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Ingår i: IEEE Transactions on Components Packaging and Manufacturing Technology. - 2156-3950. ; 1:2, s. 196-207
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Tidskriftsartikel (refereegranskat)abstract
- Supply grids of integrated chips are interconnected through through-silicon vias (TSVs) in modern design techniques to form a 3-D stack in vertical direction. The load on each chip is supplied through (power/ground) TSV pairs. Accurate estimation of power/ground noise on each TSV pair of a 3-D power distribution network is necessary for a robust power supply design. The worst case noise obtained with fast switching characteristics may not be significantly accurate. The behavior of power/ground noise as a function of rise time for an inductive power distribution TSV pair with decoupling capacitance, is investigated in this paper. An equivalent rise time corresponding to resonance is presented to accurately estimate the worst case power/ground noise in the time domain. In addition noise sensitivity to decoupling capacitance and TSV inductance is evaluated as a function of rise time. We also discuss noise accumulation as a result of worst case damping factor in this paper.
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| 9. |
- Ahmad, Waqar, et al.
(författare)
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Peak-to-peak Switching Noise and LC Resonance on a Power Distribution TSV Pair
- 2010
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Ingår i: 2010 IEEE 19th Conference on Electrical Performance of Electronic Packaging and Systems, EPEPS 2010. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 173-176
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Konferensbidrag (refereegranskat)abstract
- How peak-to-peak switching noise as well as the LC resonance term varies by varying different circuit parameters of a power distribution TSV pair (having decoupling capacitance and logic load), within a 3D stack of ICs interconnected through TSVs.
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| 10. |
- Ahmad, Waqar, et al.
(författare)
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Power distribution TSVs induced core switching noise
- 2011
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Ingår i: Electrical Design of Advanced Packaging & Systems Symposium (EDAPS), 2010 IEEE. - : IEEE conference proceedings. - 9781424490691
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Konferensbidrag (refereegranskat)abstract
- Size of on-chip interconnects as well as the supply voltage is reducing with each technology node whereas the operating speed is increasing in modern VLSI design. Today, the package inductance and resistance has been reduced to such an extent that core switching noise caused by on-chip inductance and on-chip resistance is gaining importance as compared to I/O drivers switching noise. Both on-chip inductance and skin effect are prime players at frequencies of the order of GHz. The problem is further aggravated when chips are interconnected through TSVs to form a 3D integrated stack in order to achieve low form factor and high integration density. In this paper we analysed peak core switching noise in a 3D stack of integrated chips interconnected through power distribution TSV pairs, through our comprehensive mathematical model which has been proved to be quite accurate as compared to SPICE. We analysed the effect of number of chips in a 3D stack, rise time, decoupling capacitance, and skin effect on power distribution TSVs induced core switching noise in this paper.
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