Radiometry^ Communications, and Radar
7.1 An intrusion alarm uses a HgCdTe photovoltaic mode detector in an
optical system with aperture diameter of 2 cm and focal length of 20 cm.
If an intruding object suddenly fills the detector FOV, we wish to find
how small a temperature difference will yield a (S/N)y of 10, which
would assure a high detection probability and low false-alarm
detector has a wavelength cut-off of 5 /jm, an 7j of 1, an area of
a zero-bias junction resistance of 10 Q, and operates at room
temperature, 300 K. Since the detected radiation is on the "tail" of the
blackbody curve, it may be approximated by
(b) What is
for the detector ?
(c) Assume junction noise is dominant and find the NEP for a
(d) What is the minimum temperature change that will give a
reliable alarm ?
amplifier sensitivity for direct detection at the end of
Section 7.2 was A3
or 5 x
(a) Find the sensitivity for the same data rate using ideal
MHz, and the same BER =
(b) Find the new achievable range for a fiber attenuation of 0.2
and P ^
7.3 A museum exhibit is held in a large room with a ceiling height of 10
m. To supply multilingual narrative, the visitors are supplied with
earphones equipped with a PIN-FET /audio amplifier with an optical
filter tuned to one of several semiconductor laser wavelengths. In the
ceiling, various lasers transmit audio messages in the various languages.
All the lasers operate near
Each laser radiating area is
the threshold current is 20 mA, operating point, 50 mA, atl5 mW. The
maximum audio signal is thus a sinusoid with a full excursion between