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Thanks to the special algorithms which have been developed during the research project and
described in the previous chapters, FMCW SAR images with a measured resolution up to 45 cm
times 25 cm (including Hamming windowing) were produced. Moreover, if the delay is larger than
the subpulse duration, also a phaseshift multiplication is needed. Through passing from atmosphere
some portion of the cosmic noise is absorbed by the atmosphere and reradiated as cosmic noise. In
designing a SAR system, the operational modes in which the sensor operates and thecharacteristics
of the aircraft which carries the sensor have to be taken into account. It cor-rects the non-linearity
effects for the whole range profile at once, and it allows a perfectrange focussing. Therefore, state-
of-the-art methods for the characterization of isolated UWB antenna elements are used. Phase noise
(PN) injected to the system is oriented from the voltage controlled oscillator (VCO); thermal noise
(TN) is oriented from VCO and from solar, galactic (which are called cosmic noises) and
atmospheric absorption noises. Chapter 4 derives a complete analytical model of the FMCW SAR
signal description in thetwo-dimensional frequency domain, starting from the deramped signal and
without us-ing the stop-and-go approximation. If a target is moving while being illuminated by the
radar, its radial velocity Time Am plit ude (a) Amplitude plot of a chirp signal. When the stop-and-go
approximation is not valid, the frequency of the received signal isbetter described as shifted with
respect to the transmitted by an amount equal to the Dopplerfrequency. Figure 4.2 shows
qualitatively the signal support band in the two-dimensionalrange spatial frequency Kr and azimuth
spatial frequency Kx domain for a wideband FMCWSAR. In Figure (4.20) isolation between ports 1
and 3 is given. After a pulse is transmitted, radar listens for the echoes from the targets until the next
pulse transmitted. Because pulse modulated FMCW radar utilizes the beat frequency measurement
instead of time delay measurement. Isolation has maximum with a value of 57 dB at 885 MHz from
port 1 to 3. 4.5.5 Switch Switches are operated such to determine the transmitting and receiving
modes of the radar. Component tests for fixed delay line are also conducted and the results are given
as well. It presented a novel processing solution, developed within the framework of thisthesis,
which completely removes the frequency non-linearity effects. The distance R can be calculated
from Equation (2.11). FM Transmitter Modulator Mixer Amplifier Limiter Frequency Counter
Indicator Reference Signal Receiving antenna Figure 2.5 FMCW radar system Transmitting antenna
Page 23. The novel approach presented in the appendix aims to combine the non-linearity correc-tion,
developed by the author within the framework of the thesis, the FSA and the removalof the FMCW
Doppler shift. This allows for simultaneous transmission and reception, providing continuous
measurement of range and velocity. Thesuppression is performed directly during the range
compression, avoiding in this way spec-trum aliasing problems in the Doppler domain. This technique
is based on the fact that the stepped frequency order inside the pulseis randomly changed from pulse
to pulse. In the present discussion, we will assume the aircraft velocity such that the resulting sam-
ples are equally spaced in the azimuth direction. The project presented in this master thesis aims to
the development of an AWR2944-based RADAR system embedded on a Printed Circuit Board. In
addition to the particular signal aspects relative to the combination of FMCW technol-ogy and SAR
techniques, the use of FMCW radars for long range high resolution applications Page 126. The
chapter proposes two novel methods to discriminate moving targets which have theirDoppler
spectrum folded back in the clutter region. In the alternative method a variable voltage source varies
the injected beat frequency. Page 84. Motion data are used to perform a first removal of the
motionerror effects, and then SAR algorithms process the collected raw data to produce SAR im-
ages. The only noise from VCO affecting the system is via LO port of the mixer (a) and reflecting
from ground (d). A wider range of frequencies swept by the modulation waveform and a higher
frequency of the modulating waveform will yield more accurate measurement of the range
information. The output of this process, the IntermediateFrequency (IF) signal, is successively high
pass filtered in order to remove the strong directcoupled signal, which could saturate the sampling
card, and amplified.
Best Student Paper Award, Waveform Diversity and Design Conf. It is further shown how this
model is related to the narrowband models used for DOA estimation in traditional multi-channel
FMCW RADAR systems. Subsequently refined beamforming algorithms based on the approaches of
Bartlett and Capon, which take into account the received IF signal of the UWB FMCW sensor array,
are proposed. Monostatic radar utilizes a common antenna both for transmitting and receiving. The
received signal (c) and the transmitted are then mixed,producing the beat signal (d). Page 30. The
project presented in this master thesis aims to the development of an AWR2944-based RADAR
system embedded on a Printed Circuit Board. The integration of the non-linearity correction in
FMCW SAR algo-rithms is described in appendix A. 3.4.1 Algorithm overview In this section a
heuristic overview of the proposed method is given. B 1 GHz Ru 150 m N 1000 RTs150 m Ts 1 ?s
target 1 50 m PRI 1 ms target 2 225 m PRF 1 kHz target 3 400 m A bandwidth of 1 GHz is
transmitted using 1000 subpulses, leading to an unambiguousrange (Ru) of 150 m for linear
modulation. Today SAW devices have many applications, every modern television have at least one
receiver with a SAW filter and many of the telecommunication system, satellite systems, and smaller
radar systems utilizes the high performance SAW filter techniques. In the United States much of
radar research also took place at the Massachusetts Institute of Technology’s (MIT) Radiation
Laboratory. By the developing technology the operating frequency of the equipment used in radar
systems are increased and higher frequencies used in radars. You can download the paper by clicking
the button above. At the same time it is important that ICs contain only transistors, diodes, resistors
and capacitors. It also works at Ka band and is foreseen to bedeployed on a similar Stemme motor
glider as the one used for the TU Delft FMCW SARflight test campaign. The theoretical relation of
the bandwidth given by: (3.8) where ?F is the bandwidth and f0 is the center frequency. The affect of
the cosmic noise will be calculated throughout this section. To browse Academia.edu and the wider
internet faster and more securely, please take a few seconds to upgrade your browser. Electronic-
photonic 3D integration of optoelectronic components can greatly improve the performance of
FMCW LIDAR sources. Equation (2.6) expresses the power received from a target at distance R and
whose RCS is ?, the operating wavelength is. It is evident how the three differ-ent Doppler regions
can be suppressed separately, enhancing in this way the moving targetindication capability.
Automotive FMCW Radar System Design using 3D Framework. SCLF- 1000 from Mini-Circuits
and LMS1000-5CC from Lark Engineering was measured. The non-linearities present in the beat
signal are the result of the interaction between thetransmitted and received non-linearities. The noise
level is directly proportional to the bandwidth of the signal thus increasing the frequency resolution
yields an increase in the noise power. To determine this delay marker?delay method of the network
analyzer HP 8720D was used. I would like to express my gratitude to my colleagues at IRCTR. Two
novel, slightly different, methods to correct for nonlinearities in the frequency sweep by digital post-
processing of the deramped signal were introduced independently by Burgos-Garcia et al. (Burgos-
Garcia, Castillo et al. 2003) and Meta et al. (Meta, Hoogeboom et al. 2006). In these publications,
however, no formal proof of the techniques was given, and no limitations were described. A wide
band filter cannot be designed by using arbitrary materials. The equivalent squint angle depends on
the targetvelocity; therefore, there are certain velocities that induce a squint angle such that the
movingtarget Doppler bandwidth falls over (due to the undersampling) in the clutter region. S12 is
the reverse isolation that is the signal that gets from output port to the input. In fact, the assumption
that the non-linearity effects in the intermediate signallinearly depend on the time delay is valid only
for small range intervals.
The transmitted and received echo signal power levels calculated and noise of the system
determined. The blind range (Rp) is calculated from Equation (2.12) and the multiples of the blind
range are also blind. The thesis isorganized as follows: Chapter 2 provides a short overview of the
FMCW radar and SAR principles. This reflects a different response in linear FMCW radars, because
the Dopplercomponent within one single pulse could be not negligible. If not performed beforeevery
measurement, a drawback of this method (as well as of any other solution based on the Page 77. The
subpulse duration is 1 ?s, so the range profileis divided in parts (RTs ) of 150 m extension. The
circular antenna array is optimized for vehicle rooftop integration and is based on mechanically
robust Monocone antenna elements. Outside the working hours, I was never alone and for this I
thank all the friends of Delft,particularly Marco Pausini and George Papaefthymiou for having
agreed to serve as “paran-imf” during my Ph.D. defense. And, of course, my friends from
Roccasecca, which were(and are!) always close to me in spite of the distance. This noise will be
injected to the IF stage via reflecting back from the ground. Continuous wave radars are unable to
measure the distance between radar and target. In linear FMCW, thederamping technique is often
adopted for range processing in order to drastically reduce thesampling frequency. A HP-83640A
Synthesized Sweeper was used as the local oscillator. 4.5.1 Voltage Controlled Oscillator (VCO)
Frequency deviation (?F) of the pulse FMCW radar can be achieved by using suitable VCO. The
sampled IF signal isthen processed via the algorithms described in chapter 3 in order to obtain the
range infor-mation. These harmonics will be suppressed approximately 50 dB by using a low pass
filter at the output of the VCO. If the target is in motion and the beat signal contains a component
due to doppler frequency shift, the range frequency (fb-fd) can be extracted from the received
signal. RCS of a target depends on the shape, size, material, properties of the target and the
frequency, polarization and angle of arrival of the incident wave. Laboratory and ground based
measurementsshow very good consistency with the calculated values, validating the model descrip-
tion. The transmitted signal path is from port 1 to 2 and the echo signal path is from port 2 to 3.
Isolation has maximum with a value of 57 dB at 885 MHz from port 1 to 3. 4.5.5 Switch Switches
are operated such to determine the transmitting and receiving modes of the radar. S12 is the reverse
isolation that is the signal that gets from output port to the input. A third harmonic with a power
level Figure 4.14 Photograph of JTOS-1025 Page 67. However, since the derived expres-sion is a
more general description of the SAR signal, it has to hold also when the true velocityvalue is
inserted. If we add a delay to the reference signal as long as the delay of the test board phase of the
system will be calculated as zero. From each of them, oneFMCW SAR image is produced and
successively the two are processed using interferometric deforma-tion techniques in order to detect
changes induced by moving targets. Page 65. By using recursive adaptive Simpson quadrature in the
m file named “Pr.m”, integral is calculated with an error of less than e-6. In order to have agood
understanding of how the algorithm works, it is preferable to have a clear visual rep-resentation of
which is the distinct transmitted and received non-linearity contribution in theresulting beat signal
non-linearities. Power received from an angle of incidence from an angular width of ? is; (4.10)
where; (4.11) (4.12) 4.3 Echo Power Angular Distribution Angular distribution (density) of the
received echo signal at the antenna of the system is plotted using Equation (4.10), changing from -
10o to 70o for different Q values corresponding to distance of 100, 500 and 1000 meters. Equation
(2.6) expresses the power received from a target at distance R and whose RCS is ?, the operating
wavelength is. In the pulse modulated FMCW radar, the transmitter transmits the signal only for a
limited time interval and then the receiver listen for the echoes of the transmitted signal. The second
category gives rise to bistatic effects while the motion duringtransmission and reception of the pulse
is usually neglected.
This in order to guarantee enough signal to noise ratio and resolution. Page 26. Automotive FMCW
Radar System Design using 3D Framework. The doppler frequency shift will causes the beat
frequency echo signal to be shifted up or down by doppler shift (fd). Figure (2.9) illustrates the beat
frequency time plot of the echo signal. Speed of light, modulation frequency (fm) and the deviation
of the modulation frequency (?f) is assumed to be constant, thus the distance from radar to the
target is a function of the beat frequency (fb). For different values of the distance d phase noise (Pn)
is calculated and given in Table (4.1). Table 4.1 Received echo signal power and phase noise level d
(m) 100 500 1000 Received Echo (Pr,dBm) -48.8 -62.8 -68.9 Phase Noise (Pn,dBm) -122.8 -136.8 -
142.9 The system is also affected from thermal noise. The integration of the non-linearity correction
in FMCW SAR algo-rithms is described in appendix A. 3.4.1 Algorithm overview In this section a
heuristic overview of the proposed method is given. Two images are reproduced in fig. 7.14 and fig.
7.15. After non-linearity correction, theprocessed SAR bandwidth has been set to 200 Hz, and an
averaging of 16 cells in the crossdirection has been performed in order to reduce the speckle. In fig.
7.15, the response of acorner reflector is visible belove the crossing-roads. The Doppler frequency of
thetarget is finally obtained using also the ambiguous Doppler information estimated from the Table
7.2: Results for the moving target analysis. Usually, in pulse SAR radars,the PRF can be chosen high
enough for the unambiguous velocity to be less unlikely tooccur; however, a large pulse duration,
and therefore a low PRF, is desirable in FMCW SARbecause this relaxes the sampling requirements
and the circuitry complexity for a given rangeresolution and maximum range. Since the measurable
shift is not ?x but actually?ximage, the velocity estimation can be ambiguous. The computational
load of the described non-linear frequency scaling algorithm ispractically the same as the
conventional one. However, these components were not available atthe time of the assembling, and
the obtainable improvement (noise level decreased of about5 db) was not crucial for proving the
feasibility of an FMCW SAR. 6.2.1 Steering signal In order to avoid problems related with the
discrete nature of the steering signal, an ex-ternal voltage offset has been provided implementing an
operational amplifier. RCS of a target depends on the shape, size, material, properties of the target
and the frequency, polarization and angle of arrival of the incident wave. Frequency response of
SCLF-1000 and LMS1000-5CC are given in Figure (4.16). The characteristic of LMS1000-5CC is
much more ideal than the characteristics of SCLF-1000. Figure 4.15 Photograph of SCLF-1000 (left)
and LMS1000-5CC (rigth) Page 68. IGARSS’03, Toulouse, France, July 2003, vol. VI, pp. 4074-
4076. Page 131. The following subsections give an overview of the al-gorithm, followed by an
analytical development, simulation results and discussion of someimplementation details. It is
notpossible to discriminate these moving targets using solely the Doppler information. The
interference signal of light in the two paths on a photodetector generates a sinusoidal beat signal
whose frequency is proportional to the distance of the target. If the noise signal level exceeds the
echo signal level or very close to each other the receiver maybe unavailable to detect the beat
frequency signal. In practical FMCW sensors, in fact, the presence of unwantednon-linearities in the
frequency modulation severely degrades the radar performances forlarge distances. By the
development of radar, its application areas become larger as well. A complete model description of
the X-band FMCW SARfront-end system developed at the IRCTR, Delft University of Technology,
has beenprovided. The input and output return losses are obtained from S11 and S22 parameters
respectively. The aim of this chapter is to develop a complete FMCW SAR signal model which
takesinto account also the effects of the motion during the sweep. If the target is in motion relative
to the radar a doppler shift in the frequency of the received signal will occur. Based on thismodel,
proper algorithms have been developed which guarantee the best performance whenprocessing
FMCW SAR data. Continuous wave radars are unable to measure the distance between radar and
target. The aim is to penetrate clothes and to find personal-born weapons and explosives under
clothes. Although the IMU-FMCW SAR joint experiment failedto produce good results during the
2004 flight campaign, it provided very good experience. The frequency shift fd is proportional to
oscillation frequency f0 and the relative velocity of the target ?r. (2.10) The graph of Doppler
frequency as a function of oscillation frequency and some relative target velocities calculated using
MATLAB 6.5 is given in Appendix B.
Applying the model developed in the chapter, deramped linear FMCWSAR data can be correctly
processed and theoretical results are obtained. To calculate the power related issues we must define
the illuminated area (?S) with respect to angle of incidence (), beamwidth of the antenna (B) and
distance from target (d). As in conventionalpulse SAR systems, the stop-and-go approximation could
be used; such an approximationassumes the radar platform stationary during the transmission of the
electromagnetic pulseand the reception of the corresponding echo. Radar transmits a form of
electromagnetic energy such as pulsed modulated wave and receives the reflected electromagnetic
energy back from the object. The system’s frequency range is from 6 GHz to 9 GHz and hence
possesses a relative bandwidth of 40 %. In order to have agood understanding of how the algorithm
works, it is preferable to have a clear visual rep-resentation of which is the distinct transmitted and
received non-linearity contribution in theresulting beat signal non-linearities. The antenna is usually
mountedon an aircraft or satellite, which provide the moving platform. The particular response of
thesestrong stationary targets in the interferogram, similar to a moving target response, is due tothe
fact that part of the processed target energy is coming from the antenna sidelobes. In both the
operational modes, the imageswath is limited by the PRF in conventional radars; its value is
determined by the maximumallowable distance travelled by the radar platform between successive
transmitted pulses andby the fact that the PRF has to be high enough to sample the instantaneous
clutter Dopplerbandwidth. Page 53. The radar must be designed to have the maximum detectable
range longer than 1000 meters. If your waves are focused in a narrow beam, you can know the
direction of the object by moving the beam from side to side. Circulator is a 3-port ferrite device.
Figure 4.17 Photograph of MS850-4CC Frequency (Hz) S21 (dB) Figure 4.18 Frequency response
of MS850-4CC Page 70. Moving Target Indication (MTI) with frequency modulated CW SAR.
Acoustic surface waves nowadays called Rayleigh waves are useful because the propagation of these
waves is very much smaller compared to the velocity of the electromagnetic waves. The second
makes use of the Doppler filtering properties of randomized SFCW modulations. 5.1 Introduction
There is a need in several applications for the detection of ground moving targets and theestimation
of their velocity. Such techniqueshave already been successful employed in the field of radar earth
observation by using co-herent pulse radars. The distance of the target is determined by the amount
of time transmitted signal is traveled from antenna to object of interest (target) and back from object
to the antenna. The receiving antenna collects the reflected energy and delivers it to the receiver for
determining necessary information such as presence, range, location and relative velocity of the
target. Several tests performed during the flight campaign (imaging at different resolutions, varying
the incident angle, MTI experiment) are reported and discussed. To have the complete range profile,
this operationhas to be performed varying the parameter l. Furthermore, such sensors are of military
interest; reconnaissance tasks could beperformed with small unmanned aerial vehicles (UAVs),
reducing in this way the risk forone’s own troops. The second-generation RADAR chip,
manufactured by Texas Instruments, brings new features with respect to the first-generation one
which are crucial for the detection accuracy improvement. We will calculate phase noise in Section
(4.4.4). 4.4.3 Antenna Thermal Noise In previous section we show that the thermal noise of the VCO
is very small compared to the phase noise of the VCO. The proposed method is superior compared to
the existing non- Figure 3.1: Range dependent non-linear effects in the beat frequency signal. Page
29. The re-ceived signal intercepted by the antenna beam is amplified with a low noise amplifier
(LNA)and mixed with part of the transmitted signal. Thanks to the special algorithms
developed,FMCW SAR images with 45 cm times 25 cm resolution (including windowing) havebeen
obtained for the first time. 1.4 Outline of the thesis The remaining of this thesis is divided in seven
chapters: in the first four, the theory ofFMCW SAR is introduced. A careful comparison of the
refined algorithms with the traditional algorithms is used to demonstrate their superior performance
in UWB FMCW RADAR systems. In addition it is shown that a sensor element spacing larger than
the traditionally known limit may be used, which simplifies the design of UWB array antennas. The
doppler frequency shift will causes the beat frequency echo signal to be shifted up or down by
doppler shift (fd). Figure (2.9) illustrates the beat frequency time plot of the echo signal. We offer an
overview of SDR architecture and its basic components, then discuss the significant design trends
and development tools. A third harmonic with a power level Figure 4.14 Photograph of JTOS-1025
Page 67.
This limitation is due to the fact that only one antenna is used. The proposed method operates
directly on the deramped data and it is very computationally efficient. The first detection of an
aircraft is in 1930 by L. A. Hayland from NRL. The operating frequency of this radar was around 26
MHz. The processing block diagram is shown in fig. 5.4. An example of the application of themethod
on real data is reported in section 7.8. Figure 5.4: MTI with triangular FMCW modulation. By
calculating the frequency difference, the radar can determine the target's velocity. The transmitted
and received echo signal power levels calculated and noise of the system determined. Detailed
discussions on system performance predictions and enhancements, as well as design considerations,
are provided. The frequency response (S21) is given in Figure (4.25) and the phase response given in
Figure (4.26). 7 7.5 8 8.5 9 9.5 10 x 108 -34 -33 -32 -31 -30 -29 -28 -27 -26 Insertion loss of the test
board varies between -26.5 to -27.5 dB. Center frequency is 850 MHz and the 3 dB bandwidth is
equal to 250 MHz. Another sub equation; (2.4) defines the isotropically scattered power density at
the position of the receiving antenna. FMCW SAR images produced with the upslope part of
themodulation (a) show opposite range shift compared to downslope image (b). The reduction of the
velocity is in the order of 0.1% to 5% and is very precise. The actual development of radar is between
World War I and World War II as a tool for detecting enemy aircrafts from long distances. The major
use of radar is in military applications such as surveillance, navigation and control and guidance of
weapons. The output power transmitted at the antenna (Pt) is taken as 30 dBm (1W) and the
elevation and azimuth beamwidths of the antenna (B,?B) are taken as both 80o and the gain of the
antenna (G) is taken as 8 dB. Page 49. Effective area represents the amount of the physical area of an
antenna that serves as an electrical antenna. ABSTRACT RANGE RESOLUTION
IMPROVEMENT OF FMCW RADARS Sinan KURT. The fundamentals of this technique lie in the
discovery of the piezoelectricity by the brother Curie in 1880 and of the surface acoustic waves in
1885 which is the basis of the SAW devices by the famous English scientist Lord Rayleigh. Thus the
noise from VCO cancelled when the radar is on receiving (listening) mode. In section 4.2, a brief
heuristicoverview of the FMCW SAR signal is described, indicating when conventional SAR algo-
rithms cannot be used, while section 4.3 derives an analytical description of the FMCW SARsignal
without any approximation. However, radar sensors used forimaging purposes exhibit relative low
resolution in the cross-range or azimuth dimension, andfurthermore it gets coarser with increasing
distance due to the constant antenna beamwidth.This limitation is overcome by Synthetic Aperture
Radar (SAR) techniques. One is the phase noise and the other is the thermal noise. Signal Processing
of FMCW Synthetic Aperture Radar Data. The pictures on the cover are FMCW SAR images
produced with and withoutusing the range frequency non-linearity correction algorithm developed
by theauthor. (See also figure 7.11 of this thesis). Page 3. Therefore, state-of-the-art methods for the
characterization of isolated UWB antenna elements are used. Nevertheless, the introduction of the
Ethernet interface in the AWR2944 chip enables the exchange of large quantities of data with other
sub-systems. The starting point of this work was the Printed Circuit Board design that embeds the
first-generation AWR1843 chip. Ans. FMCW radar can be affected by interference from other radar
systems operating in the same frequency band. The noise level is directly proportional to the
bandwidth of the signal thus increasing the frequency resolution yields an increase in the noise
power. England was very vulnerable to attacks from the German air force, and so in the late 1930s a
network of radars was constructed along the southern English coast called “Chain Home”. The
doppler frequency shift will causes the beat frequency echo signal to be shifted up or down by
doppler shift (fd). Figure (2.9) illustrates the beat frequency time plot of the echo signal. With the
development of ICs, the problem of miniaturization of filters, delay lines and other components that
included inductive elements appeared.