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Placement
Papers >>
Hardware Questions
>>
RF and Radio
Engineering Interview Questions
- What’s a
PCB? Printed Circuit Board.
- 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. </>
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