| 1. |
- Azam, Sher, 1971-, et al.
(författare)
-
Performance of SiC Microwave Transistors in Power Amplifiers
- 2008
-
Ingår i: Proc. of MRS Symposium on wide bandgap semiconductor electronics 8. - 9781605110394 ; , s. 203-208
-
Konferensbidrag (refereegranskat)abstract
- The performance of SiC microwave power transistors is studied in fabricated class-AB power amplifiers and class-C switching power amplifier using physical structure of an enhanced version of previously fabricated and tested SiC MESFET. The results for pulse input in class-C at 1 GHz are; efficiency of 71.4 %, power density of 1.0 W/mm. The switching loss was 0.424 W/mm. The results for two class-AB power amplifiers are; the 30-100 MHz amplifier showed 45.6 dBm (∼ 36 W) output powers at P1dB, at 50 MHz. The power added efficiency (PAE) is 48 % together with 21 dB of power gain. The maximum output power at P1dB at 60 V drain bias and Vg= -8.5 V was 46.7 dBm (∼47 W). The typical results obtained in 200-500 MHz amplifier are; at 60 V drain bias the P1dB is 43.85 dBm (24 W) except at 300 MHz where only 41.8 dBm was obtained. The maximum out put power was 44.15 dBm (26 W) at 500 MHz corresponding to a power density of 5.2 W/mm. The PAE @ P1dB [%] at 500 MHz is 66 %.
|
|
| 2. |
- Azam, Sher, 1971-
(författare)
-
Wide Bandgap Semiconductor (SiC & GaN) Power Amplifiers in Different Classes
- 2008
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- SiC MESFETs and GaN HEMTs have an enormous potential in high-power amplifiers at microwave frequencies due to their wide bandgap features of high electric breakdown field strength, high electron saturation velocity and high operating temperature. The high power density combined with the comparably high impedance attainable by these devices also offers new possibilities for wideband power microwave systems. In this thesis, Class C switching response of SiC MESFET in TCAD and two different generations of broadband power amplifiers have been designed, fabricated and characterized. Input and output matching networks and shunt feedback topology based on microstrip and lumped components have been designed, to increase the bandwidth and to improve the stability. The first amplifier is a single stage 26-watt using a SiC MESFET covering the frequency from 200-500 MHz is designed and fabricated. Typical results at 50 V drain bias for the whole band are, 22 dB power gain, 43 dBm output power, minimum power added efficiency at P 1dB is 47 % at 200 MHz and maximum 60 % at 500 MHz and the IMD3 level at 10 dB back-off from P 1dB is below ‑45 dBc. The results at 60 V drain bias at 500 MHz are, 24.9 dB power gain, 44.15 dBm output power (26 W) and 66 % PAE.In the second phase, two power amplifiers at 0.7-1.8 GHz without feed back for SiC MESFET and with feedback for GaN HEMT are designed and fabricated (both these transistors were of 10 W). The measured maximum output power for the SiC amplifier at Vd = 48 V was 41.3 dBm (~13.7 W), with a PAE of 32 % and a power gain above 10 dB. At a drain bias of Vd= 66 V at 700 MHz the Pmax was 42.2 dBm (~16.6 W) with a PAE of 34.4 %. The measured results for GaN amplifier are; maximum output power at Vd = 48 V is 40 dBm (~10 W), with a PAE of 34 % and a power gain above 10 dB. The SiC amplifier gives better results than for GaN amplifier for the same 10 W transistor.A comparison between the physical simulations and measured device characteristics has also been carried out. A novel and efficient way to extend the physical simulations to large signal high frequency domain was developed in our group, is further extended to study the class-C switching response of the devices. By the extended technique the switching losses, power density and PAE in the dynamics of the SiC MESFET transistor at four different frequencies of 500 MHz, 1, 2 and 3 GHz during large signal operation and the source of switching losses in the device structure was investigated. The results obtained at 500 MHz are, PAE of 78.3%, a power density of 2.5 W/mm with a switching loss of 0.69 W/mm. Typical results at 3 GHz are, PAE of 53.4 %, a power density of 1.7 W/mm with a switching loss of 1.52 W/mm.
|
|
| 3. |
- Kashif, Ahsan-Ullah, 1974-, et al.
(författare)
-
Flexible power amplifier designing form device to circuit level by computational load-pull simulation technique
- 2008
-
Ingår i: Microelectonics Technology and Devices - SBMicro 2008, Vol. 14, issue 1. - Pennington, New Jersey : Electrochemical Society. - 9781566776462 ; , s. 233-239
-
Konferensbidrag (refereegranskat)abstract
- Matchingnetwork is major issue in broadband power amplifiers due tothe fact that the transistor impedances are varying both withfrequency and signal level. Thus it is difficult to matchthese impedances both at the input and output stages. Thetunable matching networks are very demanding and desired for buildingflexible systems, but their accuracy depends on the transistor performanceunder the large signal operation. Computational load pull (CLP) simulationtechnique is a unique way to extract the impedances ofpower transistor at desired frequencies which make the design ofmatching network much easier for multiple bands power amplifiers. AnLDMOS transistor is studied and its optimum impedances are extractedat 1, 2 and 2.5 GHz. Through optimum impedance, thetunable matching networks can be easily design for broadband amplifiers.
|
|
| 4. |
- Kashif, Ahsan-Ullah, et al.
(författare)
-
Influence of interface state charges on RF performance of LDMOS transistor
- 2008
-
Ingår i: Solid-State Electronics. - : Elsevier. - 0038-1101 .- 1879-2405. ; 52:7, s. 1099-1105
-
Tidskriftsartikel (refereegranskat)abstract
- Si-LDMOS transistor is studied by TCAD simulation for improved RF performance. In LDMOS structure, a low-doped reduced surface field (RESURF) region is used to obtain high breakdown voltage, but it reduces the transistor RF performance due to high on-resistance. The interface charges between oxide and the RESURF region are studied and found to have a strong impact on the transistor performance both in DC and RF. The presence of excess interface state charges at the RESURF region results not only higher DC drain current but also improved RF performance in terms of power, gain and efficiency. The most important achievement is the enhancement of operating frequency and RF output power is obtained well above 1 W/mm up to 4 GHz.
|
|
