I am familiar with circuit design - Basic Op-Amp Design, concepts like stablity, Phase margin and I am a beginner in Microwave Engineering. I am familiar with some basic ideas and little familiar with devices like pHEMT (High Electron Mobility Transistor) ,mHEMT,HBT and working principles.
I have a task to give a presentation on this Paper (patent) which can be downloaded here.
The title of the Patent is Switchable Multiband LNA Design. This patent talks about designing a Low Noise Amplifier. On the whole I understand the circuit, which consists of a cascode transistors to avoid the miller effect and the feedback (Which also gives some stability problems). I can understand the circuit theory part of it but I wanted to really understand the Radio Frequency Engineering used in this patent - but I am stuck with some basic questions like:
- What are the challenges in designing Amplifiers with high frequencies? - Is it not possible with popular technologies like CMOS - why are they using something like Si/Ge or InGaAs?
- Above which frequencies does the amplifier design becomes difficult? How far does the normal Op-Amp with Differential stage work? (I usually design it from DC-some MHz)
What basic knowledge is required in LNA Design? Why can't we use the same approach that we do in a normal Amplifier design? Like if we directly connect wires, impedance won't match? What is that 50 Ohms matching anyways? Why can't other others other than 50 Ohms can be used for matching? Its just we need matched resistances right?
What is noise matching?
Why in RF (Radio frequency) -MMIC (monolithic microwave Integrated circuits), few transistors are used and why are they usually big?
I tried to read this paper but concepts were just totally new and wierd to me - like using spiral inductors, biasing for transistors, variable capacitor. ]
If anybody could recommend a text book which could provide a basic knowledge for this given paper, it would be helpful.