interview question, rfic
This position is an Application Engineer so they won't ask IC process question.
Could you please proivde must-know questions with transceiver ?
Such like "what is DC-Offset" , "What is (dis)advantage of Zero-IF architecture"...
Thanks for your help.
DC offset is the mean amplitude of a waveform. DC offset is usually undesirable. For example, in audio processing, a sound that has DC offset will not be at its loudest possible volume when normalized (because the offset consumes headroom), and this problem can possibly extend to the mix as a whole, since a sound with DC offset and a sound without DC offset will have DC offset when mixed. [ref. wikipedia]. You can simply eliminate it with a high-pass filter.
The advantages of a Zero-IF (Direct-Conversion) architecture are;
1)relatively simple, 2)highest integration potential, 3)no image problem
The disadvantage may be
1) DC offset
good luck
modulation ,and demodulation schemes , some about system design like NF of cascaded block
the blockers performance , enhancement of sensitivity
matching networks
PA loading
khouly
IP3 and NF of cascaded blocks, different Transceivers toplologies like superheterodyne, low IF and zero-IF, image rejection including filters (real and complex),blocker mask ,pulse mask,i think also some modulation schemes, AGC,...............
I would add I-Q imbalance to the disadvantage of zero IF system.
disadv. of zero is in any rf book like razavi's?
they are:
1-DC offset
2-LO-RF leakage
3-even order modulation
4-flicker noise
5-I/Q mismatch
for more details plz refer to Razavi rf.
I think the path propagation model, sensitivity vs. noise figure, how to determine ADC bits, frequency sync. such as AFC.
The best question/answer showing the experience of the interviewed guy is the following one:
Which is the relation between the phase noise of the local oscillator (LO) of any zero IF transciever and the SNR of the output signal in the absence of the IQ baseband modulator ? The transciever has an internal PLL with a multiplication factor set on 62.5 and LO = 40Mhz.
In fact, such question can be found in many rf books.
I would be asking que's about forward and reverse bias power supplies, advantages and effecencies, for todays power hungry world, and of coarse the software designed radioes and new band split requirements.
Which is the impact of of parallel routing of the IQ signals with ground shield available versus non parallel routing or I routed on different layer than Q ?
check out www.aicdesign.com
Disadvantage of zero dc offset IF is that it is sensitive to noise and small interference in the circuit and cause the system to saturate quickly.
So any small interference from LO/supply/etc cause the receiver goes to saturation .
Mehdi
Added after 2 hours 8 minutes:
there might be some question about noise figure / gain /AGC dynamic range calculation as well
Mehdi
maybe the EMC question is more appropriate for application engineer.
Hi,
You also should consider about the simple questions: Technology, Tool...
Enumerate three IQ transcievers IC you've heard or worked with, available on the market, which are running between 900MHz and 5GHz.
I would ask what's the dynamic range of a transceiver and how it's related with the design of each block
we are a new build company making radios
what ways has the new laws on polutant free solders and components
affected the way you think in relation to new parts, techniques and repair
Hello, 1st thing a RFIC AE needs to get done is
how to get the synthesizer properly work.
2nd might be how to poperly decouple power supplys,
analog VDD, digital VDD, PLL VDD, LNA VDD, PA VDD....
We want to know if you hired someone or not.
What do you think ?:D