Science topic

# Radar - Science topic

Radar is a system using beamed and reflected radio signals to and from an object in such a way that range, bearing, and other characteristics of the object may be determined.

Questions related to Radar

We are planning to perform MIMO- SAR using FMCW Radar sensor on a moving platform. Any suggestions and inputs from anyone. Thank you.

Hello all,

I am planning to develop a radar to detect water leakages in pipes. These pipes can be present in buildings (inside walls) or underground (including concrete). Before I begin with building the radar, I intend to do extensive literature survey regarding the different problems this poses as well as current technologies in place.

It would be really helpful if any resources pertaining to above problem statement is shared.

Thanks and Regards

Abhishek

How do I compute the height of tallest skyscraper of Wuhan (Wuhan Greenland center) from S1A images using radar geometry?

Looking for alternative MIMO based automotive radars other than TI make with low cost and yet provide good performance.

We wish to write verilog code, which can be placed on an FPGA to generate FMCW radar waveform. Could, anyone suggest any code/ program pertaining to this. Thank you.

please indicate RCS and auto locking capabilities

I am looking for low cost radar sensors, which can detect targets up to 150 m in range, while simultaneously providing good range, velocity and angular resolutions.

Looking for drone tracking radar, starting from several kilometers and 0.01 RCS

Dear Researcher,

I have the following MATLAB codes that generate FMCW signal. However, I have two basic problem with code I appreciate it if you can help/guide me to resolve them:

1. Based on my understanding, this code generates FMCW for one Target as the dimension of the sig is 1 x N which must must be L x N (L is the number of target)

2. the Dechirped signal, which is Analog, at the receiver have to be converted to digital in my algorithm

Note/ I want to apply this time of signal (FMCW) to Direction of Arrival Estimation (DOA) algorithm

Again I highly appreciate your time and consideration to help me to overcome these uncertainness.

%%CODES for generating FMCW signal%%%%%%%%

% Compute hardware parameters from specified long-range requirements

fc = 77e9; % Center frequency (Hz)

c = physconst('LightSpeed'); % Speed of light in air (m/s)

lambda = freq2wavelen(fc,c); % Wavelength (m)

% Set the chirp duration to be 5 times the max range requirement

rangeMax = 100; % Maximum range (m)

% In general, for an FMCW radar system, the "sweep time" should be at least five to six times the round trip time

tm = 5*range2time(rangeMax,c); % Chirp duration (s)=Symbol duration (Tsym)

% Determine the waveform bandwidth from the required range resolution

rangeRes = 1; % Desired range resolution (m)

bw = rangeres2bw(rangeRes,c); % Corresponding bandwidth (Hz)

% Set the sampling rate to satisfy both the range and velocity requirements for the radar

sweepSlope = bw/tm; % FMCW sweep slope (Hz/s)

fbeatMax = range2beat(rangeMax,sweepSlope,c); % Maximum beat frequency (Hz)

vMax = 230*1000/3600; % Maximum Velocity of cars (m/s)

fdopMax = speed2dop(2*vMax,lambda); % Maximum Doppler shift (Hz)

fifMax = fbeatMax+fdopMax; % Maximum received IF (Hz)

fs = max(2*fifMax,bw); % Sampling rate (Hz)

% Configure the FMCW waveform using the waveform parameters derived from the long-range requirements

waveform = phased.FMCWWaveform('SweepTime',tm,'SweepBandwidth',bw,...

'SampleRate',fs,'NumSweeps',2,'SweepDirection','Up');

% if strcmp(waveform.SweepDirection,'Down')

% sweepSlope = -sweepSlope;

% end

N=tm*fs; % Number of fast-time samples

Nsweep = 192; % Number of slow-time samples

sigTx = waveform();

for i=1:K

doas_rad=AOA_Degree*pi/180;

A=exp(-1i*2*pi*d*(0:M-1)'*sin([doas_rad(:).']));

sigRx=A*sigTgt';

sigRx=sigRx+awgn(sigRx,SNR);

%DeChirped and conevrt it to Digital

% DesigRx=dechirp(sigRx,sigREF);

DechirpedSignal= sigTgt .* conj(sigRx);

end

I am doing some research in using mm wave for sensing and i am looking for a book that can help me

How do we calculate the radiated power of an aesa radar if it is using 80 T/R modules, while each TR module produces 26 dBm of power. Will that be simple arithmetic addition to 32KW or there is some other procedure to calculate the EIRP.

We have collected some data from a automotive radar sensor and a camera sensor simultaneously, and we wish to fuse the track data from both these sensors. Could any one provide the methods, approaches and techniques pertaining to this important problem and any sample codes that are available. That would help us significantly.

Generally radar detection algorithms to work in real time would require less computational complexity. CA-CFAR is good candidate algorithm in the presence of noise and when electronic counter measures/intentional interference is present, multiple detection comes in the R-D map. We have collected some real time data from mmWave sensor in the presence of ECM. Can any one of you suggest, which one is a good detection algorithms to detect the target in this scenario?. Thank you very much.

I am using a radar sensor for physiological monitoring. Suppose my required physiological frequency range is A to B Hz. I find the power of the signal in A to B Hz range and also of the remaining range. Suppose the power of the required range is U and the power of the remaining range is V. Now my query is can U/V serve as an estimation of SNR?

I'm working with a radar image and using the SNIC algorithm to segment it in Google Earth Engine. From what I have read, by viewing the region of interest and changing specific parameter values, the best result can be achieved, am I right?

I read the article about the algorithm but it is still not very clear which parameters is better to pin and which to change depending on results from every test performed.

How to set the optimal values of the parameters of the SNIC algorithm?

Thanks in advance

I m a biologist who is starting to pursue a career in Physics now! in particular, on the subject of radar. Can anyone interested in this subject guide me on a book list or articles regarding Radar basics

As per recent media reports and apprehensions from airlines, the 5G services in the vicinity of airports might affect the landing and navigation of flights, especially due to C-band of 5G which is very close to altimeter frequency of RADAR. One of such media reports can be seen at: https://www.reuters.com/technology/exclusive-major-us-airline-ceos-urge-action-avoid-catastrophic-5g-flight-2022-01-17/

Does this apprehension stand valid?

Is there any script or tuturial that use indexes or other calcs for this purpose? I need find vegetation, urban areas, water bodies and bare soil in an S-1 image. Thank you, in advance.

I want to use radar photos to study the earthquake. Is there a way to know where to be a pair of interference photos?

As we know that FMCW radars often use two antennas to increase the transmit/receive isolation.

Assume we have stationary target at certain range , and The transmitted signal is LFM signal, when starting the transmission process , The baseband spectrum shows a single echo , firstly I thought that this echo is The target echo, but when I turned on The transmitter again With no targets , I found The same results as With a target (no changes in The spectrum) Why the receiver Only sense The transmitted Signal Without any echoes received and how i separate between The transmitted signal and The received echoes??

I need to present some data in a form of a Radar graph and I don't want to use excel and I need another software.

What is the best way of making this kind of chart that can be accepted academically?

Thank you for your help and software

Please find attached two images.

On image shows the location of 5 polygons, two of them at the ocean, three at land.

The other image shows radar Sentinel-1 time-series data (in decibels) from 2014 to 2021. The plots show the mean and standard deviation into each polygon. In blue are plotted the ocean polygons and behave clearly the same way.

Some jumps can be easily seen both in std and mean values (specially in January 2020).

Why might it happen? Did something changed in the processing of sentinel 1 images?

thank you all in advance.

Hello everyone,

Can someone please let me know what does "ensemble average for a given window of pixels" mean when calculating a coherency or covariance matrix? I have taken this sentence from a paper "Polarimetric Target Decompositions and Light Gradient Boosting Machine for Crop Classification: A Comparative Evaluation".

According to my understanding I have to consider a window of size m x n and take the pixels of a radar image in that window and then perform ensemble averaging i.e. mean of those pixels. Please let me know whether my understanding is correct or not.

As of now I am performing a 2D convolution with a square window and varying their size to analyse the performance.

Thanks in advance.

Best regards

Pavan Kumar.

In FDTD there are two kinds of farfield results, namely antenna gain and scatterer RCS. So what's the difference between positive and negative RCS (in dB)? Is it related with energy absorption?

I have two .pcd files and I have extracted features using FPFH estimator. Now I want to compare these descriptors, would that be possible? if so, then how can i do that?

Any help would be appreciated!

Thank you.

I performed a test simulation with the WRF model by applying the Shuttle Radar Topography Mission (SRTM) 1-3 arcseconds data, compared with the United States Geographical Survey (USGS) data. I expected the simulation results to be better with SRTM. Unlike, I found the results to be better with USGS. I am wondering if I made a mistake during the model performance.

Hi,

Are there any research on radar used for inspecting indoor wall, i.e detecting insulation material apart from just concrete and rebars?

I have the scattering matrix images (8 images: S11_real, S11_imaginary, similarly for S22, S12, S21) and I need to create the coherency matrix images (6 images: Diagonal and upper elements T11,T22,T33,T12,T13,T23). The sensor is mono-static so S12=S21. How can it be done using python\MATLAB. Kindly share the required library/code or equation, required for it.

Should we perform radiometric calibration, multi looking etc. for the processing?

What pre-processing steps must be performed for further forming the coherency matrix?

How can I download free radar images using archeology and explore radiographs a few centimeters deep?

How many vegetation indices are there using radar images not multispectral bands?

Dear all:

When dealing with historical single radar station data (default coords system is polar), when I convert the polar coords system into cartesian system (e.g. WGS84), there will be some NaN region left around four corners for converted data. How to deal with these NaN value regions by proper interpolating methods?

Thank you all.

In physics, the description of the properties of light generally refers to its wavelength (nm), while in the range of microwaves and radio waves we refer to the frequency of a signal (e.g. kHz or MHz). Why is that so?

I've trying to access hourly precipitation data from NCEI's Radar Archive however I've not been able to configure past the downloads. Is there any code available to decode the data?

I am currently working on the radar technology and am currious what is exactly the list of all possible informations a radar can deliver.

I know that it measures the time, intensity, and other characteristics of the energy that returns from targets and determins the range, angle, and velocity of this objects.

But is that it?

Dear all, I'd like to open here a sort of forum for understanding how the geodesists community is moving in view of the X-band SAR satellite constellation. The new constellation will offer new "free, near real-time SAR data" with the "latest information about any spot on the planet within the hour". This will open completely new horizons for InSAR monitoring of ground deformation especially for rapid phenomena such as eruptions and seismic crises. The huge amount of so frequent data acquisitions will open also new needs for rapid and automatic processing. My question are: who knows more? Are you planning a routine use of these data? How?

If a radar send an electromagnetic wave to track some object I would expect that the returned wave (from the object) is accompanied by backscattering from atmosphere molecules. My question is, how is this atmospheric backscattering with respect to the transmitted wave?. The magnitude of the backscattering as well as the shape of the power spectrum concerns me. Thanks!

Dear everyone,

I performed some experiements with a FMCW Radar Instrument emitting waves of 3.8mm. I can see some "movements" when I am looking on the relative displacements (+/- 0.15mm) over multiple stable points (corner reflectors). I assume part of this "displacements" is caused by temperature, humidity and pressure variation over the time of measurement (outdoor experiment). However, when applying Rüeger (2002, Refractive Index Formulae for Radio Waves) formula then the values are about a factor of 10x too small. There does not seem to be an error of units. The paper mentions resonance lines at about 67GHz and I am wondering if this could have an influence on the measurements with 79.5GHz and is there a publication specifically for the frequencies around 80 GHz?

Would anyone have a suggestion what else could cause this "movements". The radar and the targets are mounted on a concrete pillar and I assume that there is no relative displacements due to the similar setup.

Thank you very much and best regards,

Andreas

I'm looking for a method to find the Doppler center of complex SAR image. Can anyone suggest the easiest way to estimate the Sentinel image Doppler center ?

I want to extract RCS values or backscattering coefficients from available Radar imagery and create a Geospatial layer out of it.

Thank you.

I am quite familiar with the general concept of bistatic FMCW radar. The issue that I was trying to understand relates to an HF bistatic FMCW radar and what techniques are available that allow detection of zero Doppler targets in the presence of the direct radiated signal. This radiated signal will results in a zero Doppler response at all ranges in the direction of the transmitter that in general will dominate and hence mask returns from these stationary targets if not removed.

I have searched but can not find a reference as to how this issue is addressed.

Hello,

I am trying to optimize an antenna array for MIMO radar.

I want to start by using a MATLAB code to display the aperture and the PSF (point spread function) of the array.

Could anyone give me advice on where to start or suggest a Matlab tool for me?

I am working on Radar Emitter Classifiers and I want test my codes. unfortunately I'm unable to find a dataset to test my algorithms. I'll be glad if someone can help me with this...

My vision on the future of automotive radar! What is yours?

Future automotive radars will soon go back to analogue as it is the only way to overcome what are perceived as the limitations of conventional radars, in terms of reduction of both computational efforts and radio frontends complexity and mutual interference mitigation, by using agile waveforms based on pseudo-noise generation (analogue) electronic circuitry and metamaterial-based analogue beamforming. Ultimately, it will give room for artificial intelligence engines to be built into a complete radar package, leveraging radar solutions to the next level. This imposes stringent requirements to build an affordable, high performance analogue radar platform with the complexity and cost that one would see in military grade operations.

I am really pleased and honoured to have just delivered my keynote on "Future Automotive Radar Goes Back to Analogue" to a massive internet audience, promoted by

**#BOSCH**PORTUGAL.Please follow this link to watch my talk and do provide your feedback on the disruptive ideas for next radar generation: https://media.video.bosch.com/media/t/0_t5el3pb5 [in Portuguese]. This talk has addressed ongoing research topics by my research group towards the use of pseudo-noise based radar in real case scenarios, including a benchmark against well established commercial off-the-shelf (COTS) radar solutions. On the antenna beamforming technology, electronic tunable metamaterial-based solutions will be presented as a way to mitigate the extremely slow reaction speeds in fast time-varying scenarios using current market solutions and, thus, to create the opportunity to introduce artificial intelligence into all-encompassing radars platforms for target detection and identification in harsh environments.

You may follow our recent publications on this disruptive radar topic. Cheers.

Given the I and Q channel data of the radar received signal, how to calculate the signal-to-noise ratio of the signal?

I am performing measurements with a ground-based scatterometer (or radar) to measure the backscattering coefficient (s0) of ground surfaces. My scatterometer basically consists of a vector network analyzer (VNA) and two dual polarized broadband gain horns, one for transmit (tx) and the other for receive (rx). The two VNA's transmitters are connected directly (I omit test port couplers) to the two input ports for the tx antenna (one for horizontal- the other for vertical polarization). The two VNA receivers are also connected directly to the rx antenna outputs (also h- and v pol.).

Now for my question. I want to determine the lowest possible signal I can measure with my scatterometer. Do I need to consider the gated sky measurement as my lowest possible signal as is done in for example [1], or is the lowest possible signal (still) simply the noise level of the receivers? Personally I think the latter is correct because you substract the gated sky measurement from any target target response. The gated sky measurement, as I see, it is simply a(known) offset. same time it still captures what part of the coupling is still contained in the time window associated with the target. When calculating s0, I substract the gated 'sky measurement' from the response I get from the target.

Now for my question. I want to determine the lowest possible signal I can measure with my scatterometer. Do I need to consider the gated sky measurement as my lowest possible signal as is done in for example [1], or is the lowest possible signal (still) simply the noise level of the receivers? Personally I think the latter is correct because you substract the gated sky measurement from any target response. The gated sky measurement, as I see, it is simply a(known) offset.

Any help would be appreciated.

[1] Nagarajan K., Liu P., et al., 2014, IEEE GRSL, Automated L-band radar system for sensing soil moisture at high temporal resolution.

noise detection filters like median filter is not useful for random value impulse noise. How RVIN can be detected?

According to the attached paper, dated 1977, in the American Journal of Physics, by Professor P.D. Gupta of Purdue University, a Lorentz transformation analysis of the longitudinal Doppler shift in light, over a two-way path, is equivalent to two separate classical analyses.

Are we sure that we can definitely use the Lorentz transformation analysis over a one-way path?

**Hello,**

**My question is what is the best and the most accurate method to simulate Radar Cross Section for simple objects (circular flat plate, rectangular flat plate, ... etc) using ANSYS HFSS19, I found some methods in google but some of that do not make sense while you thinking about it.**

**So if you got any good method to get accurate total RCS vs Aspect angle results using HFSS, please put that as soon as possible.**

**Thank you all.**

**Best regards.**

I am dealing with ' Optimal signal processing of frequency-stepped CW radar data' from the website of

I want to find the hidden defect in ceramic sample.

I will use the proposed method inside the paper to overcome the limitation of IFFT which is giving can giving correct number of peaks inside the graph after using the proposed method. However inside the paper, one of the procedure state that assume a set of t and n number of Ai and ti to be extracted

My question is

1.how to assume a set of t and n number of Ai and ti to be extracted?

I have a set of data in time domain with the number of 3 peaks and 101 points of data

2. Can introduce me other similar papers as well so that I can solve my problem in finding hidden defect in ceramic sample in matlab?

The Phalanx CIWS is a computer-controlled cannon system. This system, which is deployed on many American warships, is designed at the flick of a switch to detect, track, engage, and confirm kills using self-contained radar. A human operator cannot match the performance of such a device. But the duration of its automaticity is regulated by a human operator. Will a day come when such automaticity is controlled by another automaton due to its superior performance? How many layers of automaticity should be tolerated when fighting a war? Some have suggested using block-chain computer code to better regulate autonomous systems (Husain 2017).

Reference

Husain A (2017) The Sentient Machine. The Coming Age of Artificial Intelligence. Simon & Schuster, New York.

I am wondering how to use FMCW radar to estimate ego-motion? Is there any publication focusing on this topic? If one radar on the vehicle is not enough for estimation, how about using both on the vehicle and road, utilizing the sensor redundancy to make up the weakness？

Why choose radar is because in contrast to cameras, lidars, GPS, and proprioceptive sensors, radars are affordable and efficient systems that operate well under variable weather and lighting conditions, require no external infrastructure, and detect long-range objects.

I have been looking for open data bases on micro-Doppler for drones but I couldn't one. Does anyone know where I can find such a database for download?

Ionospheric radar it can generate 2D image forming technique my the linear rectangular array Ionosphere radar are recently established at Gadanki (13.5°N, 79.2°E; 6.5°N magnetic latitude) in this Radar is operated in the frequency range 30MHz operation in this are used to finding in the atmospheric layer characteristics coherently Radar imaging technique I have generates In phase and quarter phase IQ data of the Each range bin and each height of the radar and it takes the visibility matrix of each height and each time of NFFT points how is it generates an image of each receiver visibility matrix are to be multiplied are not to the weighing vector

plese give me the solution of this work this RAW DATA are 5 channel receiver database papers of the following are their

Some radars use several pulse-widths. I encountered a radar uses 2 kind of pulse-widths in turn.

I think 2 pulse-widths are used to solve ambiguity in Doppler and range.

What else are the reasons?

Do you know any more reason?

What is the principle difference between RF RMS Power Detector, log Power Detector and RF Envelope detector?

What is their application difference and I want to detect a received signal envelope (Pulse Modulation) at 10 GHz which type of detector would work best?

For radar with long pulse duration and low pulse repetition frequency, the velocity of the target changes between different PRT or even within the PRT, and it will affect the correlation properties of the sequences.

In some FMCW radar configurations, I & Q demodulator is used to dechirp the RADAR received signal. The difference between these 2 components is in phase, Q channel is shift by 90°.

I have a real adc raw data contain 512 samples ( I & Q channels), extracted from an Evaluation Development kit and I want to get target range & relative velocity.

Usually a Range-FFT is applied after a windowing function to estimate target range or at least to get beat frequencies and this is what I exactly did. I assume after the FFT processing I have to see some peaks (targets, and multipath and multipaths).

*Atteched picture presents different plots I got:*

*Hanning s used as a windowing function.*

**Questions:**

**Why there is 2 channels and we can work only with one IF channel?****Do I need to perform any additional post processing algorithm before applying Range-FFT?**

Conventionally radar QPEs are evaluated considering gauge data as the ground truth. Is there any other reference data or other method that we could use?

Autonomous Driving:

We just get from the sensors (Lidar, Radar, Video) the position of the other objects (x, y) and directly (Radar x´) and indirectly (LAser, Video by differentiating y we get y´).

How can we get x´´ and y´´, which means the prediction of the trajectory of the other objects?

1.) We can extrapolate x´and y´ by Kalman filters.

2.) We can make a driving dynamics prediction by taking Kamm´s circle.

3.) We can make a prediction based on the environment like curves and stop signs, traffic lights.

4.) We make an ethical prediction by estimating how the other driver/pedestrian/cyclist behaves to not cause an accident.

Especially to points 3 and 4 I would like to get bettern known the state of the art. Who knows the relevant research in this field?

Thanks

Hi everyone

is there any practical dataset of human body radar micro-doppler signatures for download?

for example a radar version of mocap dataset of CMU?

I really seeking for such a dataset. :-(

the difference between these two products.

**Level-1 GRD**consist of focused SAR data that has been detected, multi-looked and projected to ground range using an Earth ellipsoid model. The ellipsoid projection of the GRD products is corrected using the terrain height specified in the product general annotation. The terrain height used varies in azimuth but is constant in range.

**Phase information is lost.**The resulting product has approximately square resolution pixels and square pixel spacing with reduced speckle at the cost of reduced geometric resolution. Ground range coordinates are the slant range coordinates projected onto the ellipsoid of the Earth. Pixel values represent detected magnitude. The resulting product has approximately square resolution pixels and square pixel spacing with reduced speckle, but with reduced resolution.

**Level-1 SLC**products consist of focused SAR data geo-referenced using orbit and attitude data from the satellite and provided in Zero-Doppler slant-range geometry and have been corrected for azimuth bi-static delay, elevation antenna pattern and range spreading loss.

**Slant range is the natural radar range observation coordinate**, defined as the line-of-sight from the radar to each reflecting object. The products are in Zero-Doppler orientation where each row of pixels represents points along a line perpendicular to the sub-satellite track. The products include a single look in each dimension using the full TX signal bandwidth and consist of complex samples

**preserving the phase information**.

I've been looking for any standard to evaluate radars capability in electronic warfare. In other words if you buy a radar is there any standard to test and evaluate its ECCM capability?

SENTINEL-1 IW Level-1 products are Single Look Complex (SLC) and Ground Range Detected (GRD).

Which one is better for Land Cover Classification?

Below is the difference between these two products.

**Level-1 GRD**consist of focused SAR data that has been detected, multi-looked and projected to ground range using an Earth ellipsoid model. The ellipsoid projection of the GRD products is corrected using the terrain height specified in the product general annotation. The terrain height used varies in azimuth but is constant in range.

**Phase information is lost.**The resulting product has approximately square resolution pixels and square pixel spacing with reduced speckle at the cost of reduced geometric resolution. Ground range coordinates are the slant range coordinates projected onto the ellipsoid of the Earth. Pixel values represent detected magnitude. The resulting product has approximately square resolution pixels and square pixel spacing with reduced speckle, but with reduced resolution.

**Level-1 SLC**products consist of focused SAR data geo-referenced using orbit and attitude data from the satellite and provided in Zero-Doppler slant-range geometry and have been corrected for azimuth bi-static delay, elevation antenna pattern and range spreading loss.

**Slant range is the natural radar range observation coordinate**, defined as the line-of-sight from the radar to each reflecting object. The products are in Zero-Doppler orientation where each row of pixels represents points along a line perpendicular to the sub-satellite track. The products include a single look in each dimension using the full TX signal bandwidth and consist of complex samples

**preserving the phase information**.

I am working with a synthetic aperture radar system with fmcw signal, which transmits and receives signals continuously. The received signals are dechirped and their type is double (not complex). I want to separate the received signal of each pulse and prepare it for the range and cross-range compression.

In some instances, I've seen that the Hilbert transform is implemented on the signals to generate analytical complex signal, but I don't know its main reason and in many cases, it doesn't work appropriately!

I attached part of the received and transmitted signals.

I appreciate your comments in advance.

The radar system that I'm working with contains a linear FMCW S-band (2.26-2.59 GHz) signal with a bandwidth of 330MHz and a pulse duration of 20ms. Also, the received signal is dechirped.

Thanks for your comments and suggestions in advance.

How to plot antenna radiation pattern with MS Excel, I have tried with Radar and got the shape but unable to change the angle step (angle value/range)?

When calculating interferometric coherence, why can't you do so on a pixel by pixel basis? I know the equation for estimating coherence = (|S1∙S2* |)/√(S1∙S1*∙S2∙S2*) where S1 and S2 are the two single look complexes. And I know this calculation uses a maximum likelihood estimator but why do you need to specify an estimation window and why cant the estimation window size be 1?

Thank you.

There exist some basic models for the angle dependence of sigma0. In R.E. Clapp, 1946, “

*A theoretical and experimental study of radar ground return*” three such models are presented:[1] sigma0(theta) = constant * cos(theta)

^{2}called: “Lambert’s law”[2] sigma0(theta) = constant

[3] sigma0(theta) = constant * cos(theta)

[3] is actually more complicated since it can also include multiple reflections from deeper layers of the surface. If however one only considers direct reflections the model takes the form as shown above.

In Ulaby, Moore, Fung, 1982, “

*Microwave Remote Sensing, Active and Passive*” vol. II the authors also discuss these models of Clapp.With models [1] and [3] one cosine(theta) term accounts for the decrease in incident power per unit surface area when the radar measures the ground return under angle theta. With [1] a seccond cosine(theta) term is added in accordance with Lambert’s law: a radiating surface whose angle-dependent emission is according to I = I

_{0}* cos(theta) [Wm-2].The well-known integral form of the radar equation applied to surface returns is (see for example Ulaby1982):

P

_{rx}= P_{tx}* [ lambda^{2}/ (4 pi)^{3}] * integral[ G^{2}/ R^{4}* sigma^{0}(theta) , dA ]What I don’t understand is why there is not a cosine term in this equation by default? So

P

_{rx}= P_{tx}* [ lambda^{2}/ (4 pi)^{3}] * integral[ G^{2}/ R^{4}* sigma^{0}(theta) * cos(theta) , dA ]Because the way I see it: regardless of the scattering properties of any surface the incident power per unit surface area must be rescaled according to cos(theta).

Hi.I'm a student of communications engineering. I've been working on airborne radar target tracking methods.Is there any book you suggest me to study? Actually I found some books but I look for one to specifically study about "Airborne radar tracking methods"

I wish to collect images of vehicle from radar (using radar imaging) I can see alot of journals talking about mathematics or theory of it but noonr gives practical tutorials on it ...can someone help me obtain radar images ?

When measuring the radar cross section (RCS) of a target the incident wave at the target must be planar or close to planar. As explained in for example: Kouyoumjian R.G. and Peters L. jr., 1965, "Range Requirements in Radar Cross-Section Measurements", a maximum deviation of pi/8 from a planar phase for the phase front over the extend of the target is still permittable. Using this pi/8 -criteria for a target with maximum dimmension L one can find the well-known formula R_min = 2 x L^2 / lambda, as is also explaned in aforementioned paper.

However, with some other publications, see for example Geldsetzer T., Mead J.B. e.a., 2007, "Surface-based polarimetric C-band scatterometer for field measurements of sea ice", the antenna's maximum apperture dimension D is used instead in the same equation R_min = 2 x D^2 / lambda to calculate the far field.

Is there a reason why one would use the antenna apeture dimmension D instead of that of the target L?

I am gratefull for your comments/answers,

Jan Hofste

University of Twente (Netherlands)