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

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

View Full Document Right Arrow Icon
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 =Ω ): 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 l 2 l 1 Z S 50 50 Solution Check the stability of the transistor at 6 GHz: 22 2 11 22 11 22 12 21 12 21 1 0.238 169 1.925 2 SS K −− + ∆= = ° = = Thus 1 ∆< and 1 K > . The transistor is unconditionally stable. We can check by plotting the stability circles: ** 22 11 12 21 22 22 11 22 12 21 11 11 () 1.55 53 0.34 1.667 153 0.417 LL S S CR 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 11 1 2 2 2 2 2 1 1 1 2 2 2 1 1 1 0.8858 1 1.0008 0.3657 0.1846 0.2864 0.3742 BS S S CS S j S j =+ −∆ = =− = − = 1 2 12 44 0.670 153 0.705 53 SL BB C C CC −− − − Γ= = ° Γ= = ∠ ° The overall transducer gain will be 2 2 max 21 22 1 1 17.93 12.54dB 1 1 L T L S GS S −Γ = . Plot S Γ on the Smith chart and convert to the normalized admittance 2.18 2.4 S yj . 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, 1 b , where in this case, 2 1.8 b = . The open-
Background image of page 1

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

View Full DocumentRight Arrow Icon
circuited stub therefore needs to have an admittance of stub 2 1.8 yj b j == (since 0s t u b 2 yy y += ). From the Smith chart, the length of the open-circuited stub is found as 1 0.169 l .
Background image of page 2
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 yj =− . Rotate towards the load on a constant- Γ circle through a distance of 3 (0.427 0.187) 0.24 l λ = λ to a point on the 1 g = circle. At this point, 33 1 b =+ , where in this case, 3 1.97 b = . The open-circuited stub therefore
Background image of page 3

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

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 10/21/2011 for the course EE 44101 taught by Professor Huihoontat during the Spring '11 term at National University of Singapore.

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 Right Arrow Icon
Ask a homework question - tutors are online