Prosiding Seminar Radar Nasional 2008., Jakarta, 30 April 2008., ISSN : 1979-2921.
4. KESIMPULAN
1. Kegiatan pembangunan radar VHF LAPAN di
Pameungpeuk oleh LAPAN telah dimulai sejak tahun 2006 dan diharapkan selesai pada tahun
2010.
2. Desain konfigurasi radar, pemilihan perangkat
keras, dan pembangunan radar VHF LAPAN dilakukan sendiri oleh LAPAN bekerjasama
dengan pakar radar dari DLR Jerman dan ISRO India.
3. Instalasi dan pengujian awal radar VHF LAPAN
di Pameungpeuk telah dilaksanakan pada bulan Desember 2007 dimana terdeteksi adanya sinyal
echo dari atmosfer yang terganggu oleh sinyal big-bang ground clutter.
4. Diperlukan pengukuran lebih banyak lagi dan
pengujian data echo secara matematis untuk memastikan bahwa sinyal echo yang diterima
adalah benar sinyal radar yang dihamburbalikan oleh lapisan atmosfer dan bukannya sinyal
interferensi radio.
5. Penyempurnaan pada bulan Maret dan April 2008
berupa penggunaan metal pemisah shielding antara unit-unit pada pengontrol radar,
penggunaan konektor mini dan kabel coax 50Ohm pada penyaluran sinyal antar unit, serta
penggunaan sinyal pulsa kontrol yang benar-benar pada level TTL, menghasilkan penerimaan sinyal
echo yang jauh lebih bersih.
6. Dari pengalaman mendesain dan membangun
sendiri radar VHF LAPAN, telah diperoleh banyak informasi dan teknik radar yang sukar
diperoleh dari text book. Bantuan dari para pakar radar dunia seperti Prof. J. Roettger dan Prof.
Madhu Chandra sangat membantu LAPAN dalam penguasaan teknologi radar atmosfer. Diharapkan
selanjutnya kita akan mampu membangun sendiri sistem radar atmosfer yang kita inginkan. Dengan
menggunakan teknologi dan komponen elektronika saat ini, telah terbukti kitapun dapat
membangun perangkat keras radar atmosfer.
DAFTAR REFERENSI
[1] Eddy Hermawan, ”Trainers, Radar Unik di Garut”, Harian Pikiran Rakyat, Bandung, 17
Februari 2005, hal. 17. [2] Joergen Roettger, Terrestrial Research by
Atmosphere and Ionosphere Networks Employing Radio Science, TRAINERS
Multinational Project for Equatorial Atmosphere and Ionosphere Studies 1
st
Workshop, Bandung, 2004
[3] Mohamad Sjarifudin, “Ionospheric Observations in Indonesia : Ionospheric Research
Possibilities by Using VHF Radar”, TRAINERS Multinational Project for Equatorial Atmosphere
and Ionosphere Studies 1
st
Workshop, Bandung, 2004.
[4] Meilhaus Editor, “Manual ME- 4650466046704680”, Meilhaus Electronic
Manual, 2005. [5] Mohamad Sjarifudin, Aries Kurniawan, Adi
Purwono, Peberlin Sitompul, “Sistem Instrumentasi dan Konfigurasi Perangkat Keras
Radar VHF LAPAN”, Seminar Nasional Sains Antariksa III, LAPAN, Bandung, 2006.
[6] Viswanathan G., “A Wind Profiler for Satish Dhawan Space Centre-Shar”, TRAINERS
Multinational Project for Equatorial Atmosphere and Ionosphere Studies 1
st
Workshop, Bandung, 2004.
[7] S. Kaloka, M. Sjarifudin, E. Hermawan, J. Roettger, T. Weissenberg, C. Marcuse, M.
Chandra, C. Jacobi, G. Viswanathan, R. Ranga Rao, The LAPAN-TRAINERS VHF Radar for
Tropical Atmosphere Research in Indonesia, Proceedings of MST-11, Gadanki India, 2006.
24
Prosiding Seminar Radar Nasional 2008., Jakarta, 30 April 2008., ISSN : 1979-2921.
A Method to Determine Radial Speed of Target from the FMCW Radar Signal
W. Sediono
1,2
and A. A. Lestari
1,2,3
1
Radar Communication Systems, Jl. Prof. Dr. Satrio KAV 6, Jakarta 12940 – INDONESIA
2
Agency for the Assessment and Application of Technology, Jl. M. H. Thamrin 8, Jakarta 10340 – INDONESIA
3
International Research Centre for Telecommunication and Radar - Indonesian Branch IRCTR-IB , STEI-ITB IRCTR-TU Delft,
Jl. Ganesha 10, Bandung 40132 – INDONESIA
ABSTRACT
An established method to detect a target from the FMCW radar signal is implemented by using the method of range FFT Fast Fourier Transform. By repeating the same procedure many times at a certain azimuth angle, it
is possible to additionally compute the radial speed of the suspected target. This paper describes a method to determine the radial speed of target by extracting the phase data from the repeated range FFTs. To verify this
method a series of computer simulations was conducted at our research group. Keywords: FMCW radar, radial speed, rate of change of phase
1. INTRODUCTION
In the frequency-modulated continuous wave FM- CW radar, the transmitter frequency is changed as a
function of time in a known manner. For a saw-tooth shaped FMCW radar signal the transmitter frequency
is increased linearly with the time fig. 1.
Fig. 1: Saw-tooth shaped FMCW radar signal. The frequency of the transmitted signal is linearly increased
about ∆F within the sweep time t
s
.
If there is a reflecting target at a distance R it will cause a beat signal with the frequency [1,2]
R c
F f
m R
2 =
, 1
and the rate of frequency modulation F
m
s m
t F
F ∆
=
. By applying the Fourier transform range FFT we
will get the spectrum of this beat signal. The distance or range of the target can be determined by measuring
the peak distance from the origin of the spectrum. On the other hand, due to the Doppler effect, radar
signal reflected by a moving target in radial direction will additionally show a frequency shift [1]. The
relation between the frequency shift of radar signal and the radial speed of target is mathematically
described as
c f
v f
T r
d
2 =
2 where
v
r
= radial speed of target, f
d
= frequency shift due to Doppler effect, f
T
= transmitted frequency, and c = speed of light.
In term of complex number notation the beat signal of a moving target with constant radial speed v
r
at a range R can be formulated as
t j
t j
d R
e A
e A
t
ω ω
ϕ
+
⋅ =
⋅ =
Y
with the phase
t t
d R
ω ω
ϕ +
=
3
R R
f 2
π ω
=
and
d d
f 2
π ω =
. 4 From the above equations 1 – 4 we can rewrite the
phase of beat signal into
25
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