Name some band definitions. L-Band - 1-2 GHz, S-Band - 2-4 GHz, C-Band - 4-8 GHz, X-Band - 8-12 GHz, Ku-Band - 12-18 GHz.
What’s the definition of gain? The signal going into the device is smaller than the signal going out.
What’s a definition of an amplifier? It’s a device that exhibits gain.
Insertion loss? The signal going in is greater than the signal that’s coming out.
Thermal impedance? A measure of how hot the device gets with varying electrical input.
What’s the relation between dB and change of signal? +3 dB is 2 times bigger, +10 dB is 10 times bigger.
What’s an octave? The bandwidth characterized by higher band being twice as much as lower band (100-200 MHz).
What’s a decade? A bandwidth, where the higher band is 10x the lower band (100 MHz - 1 GHz).
Skin effect? The signal is reported on the surface of the object, but not inside, e.g. a solid brick wall.
VSWR? Voltage Standing Wave Ratio. The numeric representation of the device leak, written like X:1 where X is greater when the leak is greater and 1:1 is the absolute no-leakage VSWR.
Describe an impedance matching circuit. A circuit capable of changing the impedance with different values for incoming and outgoing impedance.
Describe circular polarization. The signal travels both vertically and horizontally.
What’s the job of the amplifier? To increase the incoming signal.
What is noise figure? The level of noise that a low-noise amplifier (LNA) is capable of discriminating.
What’s a transfer curve? It is a graph of the output power versus the input power of an amplifier.
What’s the 911 point? The point where the input power results in flames on the other end.
What’s saturation point? The point where the amplifier loses its linearity of the transfer curve.
What does balanced amplifier consist of? Two amplifiers stuck together.
What is the filters function? To filter out all the unwanted radio signals.
What filter types are there? Low-pass (all frequencies below are allowed to pass in), high-pass, bandpass (all frequencies of a given bandwidth are allowed) and band-reject.
What are saw filters used for? Very low frequency filtering.
What are mixers used for? To change the frequency of the signal.
What’s a superheterodyne receiver? It’s a receiver that uses two mixers in a row.
Describe VCO. Voltage-controlled oscillators change the frequency of the produced sine wave depending on the voltage they receive.
Who is responsible for PLLs? Phase-locked loops are done by synthesizer, that samples the sine wave and if it’s not good enough, changes it.
no offense intended, but whoever wrote the answers to these questions is demonstrating an extremely limited understanding of the concepts involved (Q 7, 10), and in some cases is just plain wrong (Q 13, 15)
#What are PRI & BRI?
Both are ISDN services, band width of PRI (Primary Rate Interface)is 2MB or rather its an E1 stream can give up to 30 telephne connections
BRI (Basic Rate Interface) is our ordinary ISDN connection that is 128kbps , CAn be configured as 2 voice or 1 voice+ 1 data or 128kbps data service .
The BRI line is 2B+1D .
I have an interview coming up and haven’t really been
doing any active engineering work for 2 or so years. thank you so much for posting this QnA. definitely got my mind joggin on the engineering path again.
To the guy Cam, I’d hoping you don’t act this cocky in your work place. That is totally unnecessary on your perhaps. Even if you knew your stuffs, you will never make it in the work place with that attitude. These questions are hard to come by and you should appreciate them for being listed here.
since cam was a pussy to tell us the real answers. IMHO these answers are not bad, but
#5: means attenuation
#10: this is actually correct answer but you should say: the current distribution density is higher on the skin than the core of a conductor
#13: Cam is an idiot, this is 100% correct it just doesn’t sound so fluent, who cares, Cam is still an idiot. You must be one bad stuck up white boy aren’t you?
#15: NF measures the noise level that an amplifier produces. Every amplifier/mixer/circuit devices adds noises to a system. LNA is no exception.
#26: PLL just make sure the output of synthesizer have the same phase as the reference frequency.
other questions you should know:
How does GSM & CDMA works: GSM is TDMA where it assigns user to a specific time slot on an assigned frequency. CDMA is spread spectrum, instead of assigning user to a specific channel or time slot of that channel, it multiplies the signal by higher code, chop it up then spread it to any open slot on the entire spectrum.
I got killed by Qualcomm/Broadcom on mix-signal and ultrawide band. So, I never made it far into the process. That was a while ago so I can’t remember the exact questions, if you guys knew them please list them here along with the answers. I’d like to give qual another beasty shot. thanks
These questions are mostly for engineers. Can anyone list possible questions for a LMR system intergration and system engineer where one’s position requires one to have knowledge of P25 requirements, narrow band migration, encryption, software defined subscriber units, interoperability gateways etc.
10 Comments on RF and radio engineering interview questions
no offense intended, but whoever wrote the answers to these questions is demonstrating an extremely limited understanding of the concepts involved (Q 7, 10), and in some cases is just plain wrong (Q 13, 15)
difference b/w mobile & cell phones
#Expand GSM & CDMA?
GSM- Global system for Mobile communication
CDMA- Code Division Multiple Access
#Expand BTS?
Base Station Transiever Subsystem
#What are PRI & BRI?
Both are ISDN services, band width of PRI (Primary Rate Interface)is 2MB or rather its an E1 stream can give up to 30 telephne connections
BRI (Basic Rate Interface) is our ordinary ISDN connection that is 128kbps , CAn be configured as 2 voice or 1 voice+ 1 data or 128kbps data service .
The BRI line is 2B+1D .
I have an interview coming up and haven’t really been
doing any active engineering work for 2 or so years. thank you so much for posting this QnA. definitely got my mind joggin on the engineering path again.
To the guy Cam, I’d hoping you don’t act this cocky in your work place. That is totally unnecessary on your perhaps. Even if you knew your stuffs, you will never make it in the work place with that attitude. These questions are hard to come by and you should appreciate them for being listed here.
since cam was a pussy to tell us the real answers. IMHO these answers are not bad, but
#5: means attenuation
#10: this is actually correct answer but you should say: the current distribution density is higher on the skin than the core of a conductor
#13: Cam is an idiot, this is 100% correct it just doesn’t sound so fluent, who cares, Cam is still an idiot. You must be one bad stuck up white boy aren’t you?
#15: NF measures the noise level that an amplifier produces. Every amplifier/mixer/circuit devices adds noises to a system. LNA is no exception.
#26: PLL just make sure the output of synthesizer have the same phase as the reference frequency.
other questions you should know:
How does GSM & CDMA works: GSM is TDMA where it assigns user to a specific time slot on an assigned frequency. CDMA is spread spectrum, instead of assigning user to a specific channel or time slot of that channel, it multiplies the signal by higher code, chop it up then spread it to any open slot on the entire spectrum.
also know db dbm
I got killed by Qualcomm/Broadcom on mix-signal and ultrawide band. So, I never made it far into the process. That was a while ago so I can’t remember the exact questions, if you guys knew them please list them here along with the answers. I’d like to give qual another beasty shot. thanks
saw filter definition is incorrect
These questions are mostly for engineers. Can anyone list possible questions for a LMR system intergration and system engineer where one’s position requires one to have knowledge of P25 requirements, narrow band migration, encryption, software defined subscriber units, interoperability gateways etc.