A system using a personal computer, speaker, and a microphone is used to detect objects, and make crude measurements using a carrier modulated by a pseudorandom noise (PN) code. This system can be constructed using a personal computer and audio equipment commonly found in the laboratory or at home, or more sophisticated equipment that can be purchased at a reasonable cost. We demonstrate its value as an instructional tool for teaching concepts of remote sensing and digital signal processing.

1.
N.
Takeuchi
,
N.
Sugimoto
,
H.
Baba
, and
K.
Sakurai
, “
Random modulation CW lidar
,”
Appl. Opt.
22
(
9
),
1382
1386
(
1983
).
2.
N.
Takeuchi
,
H.
Baba
,
K.
Sakurai
, and
T.
Ueno
, “
Diode- laser random-modulation CW lidar
,”
Appl. Opt.
25
(
1
),
63
67
(
1986
).
3.
F. J.
MacWilliams
and
N. J. A.
Sloane
, “
Pseudo-random sequences and arrays
,”
Proc. IEEE
64
(
12
),
1715
1729
(
1976
).
4.
D. V.
Sarwate
and
M. B.
Pursley
, “
Crosscorrelation properties of pseudorandom and related sequences
,”
Proc. IEEE
68
(
5
),
593
619
(
1980
).
5.
“Linear feedback shift registers implementation, M-sequence properties, feedback tables new wave instruments,” 〈www.newwaveinstruments.com/resources/articles/m_sequence_linear_feedback_shift_register_lfsr.htm〉.
6.
C.
Zeitnitz
, “
WaveIO: A soundcard interface for Labview
,” www.zeitnitz.de/Christian/waveio〉.
7.
Audacity, 〈audacity.sourceforge.net/〉.
8.
Joel F.
Campbell
,
N.
Prasad
,
M.
Flood
, and
F.
Harrison
, “
Experiments in Mathematica with spread spectrum SONAR
,”
Wolfram Technology Conference
, October 14,
2010
.
9.
Playrec is an example of a sound card interface that works with both Octave and Matlab, 〈www.playrec.co.uk/index.php〉.
10.
J.
Campbell
,
Narasimha S.
Prasad
,
M.
Flood
, and
W.
Harrison
, “
Pseudorandom noise code-based technique for cloud and aerosol discrimination applications
,”
Proc. SPIE
8037
,
80370L
(
2011
).
AAPT members receive access to the American Journal of Physics and The Physics Teacher as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.