{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

# tut1rev - Tutorial 1 Q1 Design an amplifier for maximum...

This preview shows pages 1–4. Sign up to view the full content.

Tutorial 1 Q1 . Design an amplifier for maximum gain at 6 GHz using single-stub matching sections. Calculate the gain. The GaAs FET has the following S parameters ( 0 50 Z = ): f (GHz) S 11 S 21 S 12 S 22 6.0 0.55 150 ∠ − ° 2.56 108 ° 0.04 30 ° 0.60 50 ∠ − ° 50 50 l 4 l 3 Z L 50 50 l 2 l 1 Z S 50 50 Solution Check the stability of the transistor at 6 GHz: 2 2 2 11 22 11 22 12 21 12 21 1 0.238 169 1.925 2 S S S S S S K S S + ∆ ∆ = = ° = = Thus 1 ∆ < and 1 K > . The transistor is unconditionally stable. We can check by plotting the stability circles: * * 22 11 12 21 2 2 2 2 22 22 * * 11 22 12 21 2 2 2 2 11 11 ( ) 1.55 53 0.34 ( ) 1.667 153 0.417 L L S S S S S S C R S S S S S S C R S S − ∆ = = ° = = − ∆ − ∆ − ∆ = = ° = = − ∆ − ∆ Therefore the stability circles are outside the Smith chart, and all values of L Γ and S Γ will result in stable operation. Calculate 2 2 2 2 2 2 1 11 22 2 22 11 * * 1 11 22 2 22 11 1 0.8858 1 1.0008 0.3657 0.1846 0.2864 0.3742 B S S B S S C S S j C S S j = + − ∆ = = + − ∆ = = − ∆ = − = − ∆ = 2 2 2 2 1 1 1 2 2 2 1 2 4 4 0.670 153 0.705 53 2 2 S L B B C B B C C C Γ = = ° Γ = = ° The overall transducer gain will be 2 2 max 21 2 2 22 1 1 17.93 12.54dB 1 1 L T L S G S S − Γ = = = Γ − Γ . Plot S Γ on the Smith chart and convert to the normalized admittance 2.18 2.4 S y j = . We then rotate towards the load on a constant- Γ circle through a distance of 2 (0.288 0.183) 0.105 l = λ = λ to a point on the 1 g = circle. At this point, 2 2 1 y jb = + , where in this case, 2 1.8 b = . The open-

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
circuited stub therefore needs to have an admittance of stub 2 1.8 y jb j = = (since 0 stub 2 y y y + = ). From the Smith chart, the length of the open-circuited stub is found as 1 0.169 l = λ .
The lengths of the transmission line sections for the output matching section can be found in a similar way by starting with L Γ and working toward the load on the Smith chart. Plot L Γ on the Smith chart and convert to the normalized admittance 0.21 0.47 L y j = . Rotate towards the load on a constant- Γ

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 8

tut1rev - Tutorial 1 Q1 Design an amplifier for maximum...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online