| 1. |
- Albani, M, et al.
(författare)
-
Concepts for polarising sheets & “dual-gridded” reflectors for circular polarisation
- 2011
-
Ingår i: 2010 Conference Proceedings ICECom, 20th International Conference on Applied Electromagnetics and Communications. - 9789536037582 - 9781612849980 ; , s. 1-4
-
Konferensbidrag (refereegranskat)abstract
- C-, Ku- and Ka-band communications and broadcast satellites use so-called dual-gridded reflector antennas for linear polarisation to provide independent reflector surfaces and/or independent feeds for the two orthogonal polarisations. This paper describes initial work to extend this concept to circular polarisation. First we set up preliminary specifications and identify several antenna concepts based upon planar transmission sheet polarisers. Next we identify a number of polarisers of which the most promising is the meander-line, the L+C strip-grids and the parallel-plate polariser. Finally we review the conclusions of the analyses and preliminary designs of the sheet polarisers - on the antenna level as part of a reflector antenna system, on the polariser level, and on the sheet level inside the polariser.
|
|
| 2. |
- Alderman, Byron, et al.
(författare)
-
A New Pillar Geometry for Heterostructure Barrier Varactor Diodes
- 2001
-
Ingår i: 12th International Symposium on Space Terahertz Technology. ; , s. 330-339
-
Konferensbidrag (refereegranskat)abstract
- We report on a novel diode geometry, with reduced thermal resistance, for Heterostructure Barrier Varactor, HBV, diodes. The pillar geometry presented here involves the complete removal of the substrate, electrical contacted is made by the forward and reverse side processing of metallic pillars. We propose that there is a limit to the maximum number of barriers that can be used to increase the power capability of a HBV. An analytical model has been developed to study these effects. In considering the case of a perfect thermal heat sink the limit is found to be fourteen, in applying this model to the new pillar structure this is reduced to six.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Linder, M., et al.
(författare)
-
Extraction of emitter and base series resistances of bipolar transistors from a single DC measurement
- 2000
-
Ingår i: IEEE transactions on semiconductor manufacturing. - : Institute of Electrical and Electronics Engineers (IEEE). - 0894-6507 .- 1558-2345. ; 13:2, s. 119-126
-
Tidskriftsartikel (refereegranskat)abstract
- A new procedure for extracting the emitter and base series resistances of bipolar junction transistors is presented. The parameters are extracted from a single measurement in the forward active region on one transistor test structure with two separate base contacts, making it a simple and attractive tool for bipolar transistor characterization. The procedure comprises two methods for extracting the emitter resistance and two for extracting the base resistance. The choice of method is governed by the amount of current crowding or conductivity modulation present in the intrinsic base region. The new extraction procedure was successfully applied to transistors fabricated in an in-house double polysilicon bipolar transistor process and a commercial 0.8-mu m single polysilicon BiCMOS process. We found that the simulated and measured Gummel characteristics are in excellent agreement and the extracted series resistances agree well with those obtained by means of HF measurements. By adding external resistors to the emitter and base and then extracting the series resistances, me verified that the two base contact test structure offers a simple means of separating the influence of emitter and base series resistances on the transistor characteristics.
|
|
| 6. |
- Linder, M., et al.
(författare)
-
On DC modeling of the base resistance in bipolar transistors
- 2000
-
Ingår i: Solid-State Electronics. - 0038-1101 .- 1879-2405. ; 44:8, s. 1411-1418
-
Tidskriftsartikel (refereegranskat)abstract
- The total base resistance R-BTot constitutes a crucial parameter in modeling bipolar transistors. The significant physical effects determining R-BTot are current crowding and conductivity modulation in the base, both causing reduction of R-BTot With increasing base current I-B. In this paper, it is shown that the reduction of R-BTot(I-B) With increasing I-B is directly related to the physical effect dominating in the base. A new model for R-BTot(I-B) is presented where a parameter alpha is introduced to account for the contributions of current crowding and conductivity modulation in the base. Theoretically, alpha is equal to 0.5 when conductivity modulation is dominant and close to 1.0 when current crowding is the most significant effect. This was verified by measurements and simulations using a distributed transistor model which accounts for the lateral distribution of the base current and the stored base charge. The model proposed for R-BTot(I-B) is very suitable for compact transistor modeling since it is given in a closed form expression handling both current crowding and conductivity modulation in the base. An accurate extraction procedure of the model parameters is also presented.
|
|
| 7. |
- Stake, Jan, 1971, et al.
(författare)
-
Improved Diode Geometry for Planar Heterostructure Barrier Varactors
- 1999
-
Ingår i: Tenth International Symposium on Space Terahertz Technology. ; , s. 485-491
-
Konferensbidrag (refereegranskat)abstract
- We report state-of-the-art performance of tripler efficiency and output power for a new design of AlGaAs-based heterostructure barrier varactor diodes. The new diodes were designed for reduced thermal resistance and series resistance. An efficiency of 4.8% and a maximum output power of 4 mW was achieved at an output frequency of 246 GHz.
|
|
