the invention provides a compact , low - cost , millimeter - wave radar transceiver device having all components on a single multilayer printed circuit board . the board includes a two - dimensional configurable antenna module , a combined transmit / receive module , a data reduction and analysis module , a calibration module , and a user interface module . the device is designed to provide data collection and analysis in a single unit . according to a preferred method of analysis , the data are transformed by multiplying the radar reflection signal from a target by the radar emission signal of the device , and calculating a fast fourier transform ( fft ) of the resulting product . the fft result is compared to a library of calibrated fft results to identify a structural characteristic of the target . fig1 shows a block diagram that illustrates these modules schematically and how they can be functionally and structurally integrated into a single device . fig2 shows a layout of one embodiment of the circuit board . fig3 shows an actual multilayer circuit board of the invention , and fig4 shows a circuit diagram for a circuit board of the invention . the device is particularly well - suited for identifying roadway characteristics , including pavement water content , surface ice , surface water , pavement microcracks , pavement macrocracks , ruts , potholes , skid resistance , estimated braking distance , surface resistivity , surface conductivity , pavement dielectric constant , and surface roughness . the radar device also can detect obstacles in the environment of a vehicle , such as a human or animal , another vehicle , a guard rail , a curb , a wall , a barrier , a post , a column , a piece of construction equipment , a building , a tree , or a utility pole . the device can be mounted on a moving motor vehicle , and data can be collected and analyzed at ordinary highway speeds ( e . g ., greater than 50 , or up to 55 , 60 , 65 , or 70 miles / hr or more ). the antenna module preferably includes a phased array antenna . the antenna can include from 1 to n elements ( typically n is less than 100 ), and the elements are preferably distributed in a linear , rectangular , trapezoidal , or circular array on the circuit board of the radar device . the elements can be rectangular or circular , elliptical or custom - designed patch antennas , and they can be fed through a parallel or series feed , or a combination of parallel - series feed . through the use of phase shifting , the emitted radar beam can be focused and directed onto a surface or object in the near environment of the device , or of a vehicle in , on , or beneath which the device is mounted . the antenna array can be planar or , if a flexible circuit board is used , the antenna can take on a non - planar ( e . g , curved ) shape . the antenna can be configured by varying the number and position of active elements together with phase shifting , so that the antenna is rendered sensitive to the type and proximity of desired target structure ( s ). these adaptations can be performed “ on the fly ” by the transmit / receive module which controls transmission of radar emissions through the antenna and reception of radar reflections through the antenna . preferably , the antenna module is on one surface of a multilayer circuit board , while most or all of the remaining circuit components are disposed on the opposite surface of the board , or located within the board laminate . circuit components can be either surface - mounted or through - hole mounted . the data reduction and analysis module performs the operations indicated above , or other user - defined data reduction and analysis . in some embodiments , the user can input desired data reduction and analysis parameters or algorithms , which are then executed by the data reduction and analysis module . this module can be located on the circuit side of the board or embedded into the inner layers of the printed circuit board . while in some embodiments the use of radar can be combined with collection of image data through a camera , in preferred embodiments there is no image collection or processing , as that would greatly slow the processing of data and increase the need for additional memory on the device . a major advantage of the present invention is the high speed of data collection and processing and the low cost of the device , and this is enabled in part by reliance on the use of data reduction and determination of fft profiles that can be compared to calibrated results stored onboard . the calibration module accepts the reduced and transformed data from the data reduction and analysis module and compares the transformed data to an onboard library of stored and calibrated data . the calibrated data can be obtained , for example , by using the same device under controlled conditions to detect known and / or standardized structures representing the roadway characteristics and / or vehicle environmental characteristics ( e . g ., obstacles ) sought to be analyzed or detected . the calibrations can be performed under controlled laboratory conditions , or out “ in the field ” ( i . e ., outdoors under actual driving conditions ). alternatively , the user can input their own calibrations , e . g ., as digital files , through the user interface module . the user interface module includes one or more input connectors and electronic components through which the user can input selections for controlling operation of the radar device ( e . g ., choosing an operation mode , type of target to be detected , radar frequency band , resolution , or depth of field ) and inputting parameters , choice of algorithms , calibrations , and the like . similarly , the user interface can include one or more output connectors through which reduced or transformed data or identified target characteristics can be displayed ( e . g ., on a display screen built into the vehicle or on a smart phone , tablet computer , notebook computer , or remote computer workstation ). user input can be mediated by controls such as buttons , dials , slides , a touch screen , and the like , or can be entered via wireless communications . similarly , data output can be sent directly to a display screen ( which can be the same screen , such as a touch screen , computer , tablet , or smart phone used for input ) connected to the radar device by wires or cables or via wireless transmission . alternatively , both user input and data output can be by means of wireless communications with a remote computer or control center . the millimeter - wave ( e . g ., 24 ghz , but not limited to this frequency ) transmit / receive module with integrated , configurable antenna can be used for a variety of applications , such as perimeter defense , traffic safety , vehicle radar ( e . g ., wideband , with imaging capability ), road infrastructure monitoring , and the like , the radar device operates in the unlicensed industrial , scientific and medical ( ism ) band and works by generating a millimeter wave ( e . g ., 24 ghz ) frequency signal that is transmitted towards a target , while a reflected signal is received and processed in order to describe the target under test . the integration of three different components — hardware , software / firmware , and data reduction and analysis — into a single unit is a major advantage of the invention . the millimeter - wave frequency applied to sensor technology provides the following advantages : accuracy , compactness , robustness , and manufacturing flexibility . sensors built to work in this frequency range have a higher accuracy and resolution ( to less than 1 mm ; resolution increases with increasing frequency over the range 10 - 100 ghz ), they also can be compact and robust , with miniaturized devices that can reach a few cubic cm . furthermore , the commercial availability of semiconductor chip sets in this frequency range from more than one supplier allow for a cost - effective bill - of - materials for the sensor systems . one application of the sensor device is material characterization , more specifically identification and classification of various sample materials which constitute an equivalent device or target under test ( dut ). the dut is placed in the proximity of the sensor system , and complex signals are reflected from the dut are processed by the sensor system . the resulting data are analyzed , and unique deterministic decisions are made depending on the sensor goals . for example , detecting skid resistance in pavement ( as a potential civil engineering application ) requires the identification of material ( pavement ) characteristics , such as dielectric constant , surface resistivity / conductivity , as well as other information such as surface roughness of the pavement . the millimeter wave technology allows a non - destructive non - contact methodology that has not been used previously . the output data from the sensor module can provide a substantial data - rate system , requiring complex high speed analog to digital converter ( adc ). the data also can be filtered and parsed for anomalies and outliers , while an averaging algorithm computes the statistically significant information about the dut . the radar module allows multiple modes of operation with respect to the integrated antennas . these modes allow built - in data averaging across a material surface , thereby reducing complexity of the output data while maintaining accuracy and reliability of the measurement . while the device can be fabricated and programmed to carry out many possible data reduction and analysis algorithms , one embodiment of such an algorithm operates as follows . the algorithm and data processing are tied together . the sensor itself is operated as a frequency modulated continuous wave system . a standard voltage sweep is used to shift the frequency of a sinusoidal wave across a chosen bandwidth . the bandwidth and speed of the shift result in the application of interest — for example , a larger bandwidth results in a finer range of resolutions ( i . e ., depth of field ). the outgoing signal is amplified by the transmit antenna and propagated through the medium ( air ) towards the target . the size of the antenna and distribution of its elements aid in focusing / defocusing of the signal ( hence the antenna is reconfigurable ). once the signal is received , it is mixed ( multiplied ) by the sent signal in order to obtain a low - frequency signal which is then digitized and the fast fourier transform ( fft ) is applied . the algorithm then looks at the fft fingerprint to evaluate the material information and / or the condition of the surface being measured ; this information is looked up a table or database of pre - calibrated materials to match with the fft information about the material present and to thereby identify the target material or object . the algorithm can be prototyped and refined on a computer connected to the radar sensor , and then software to run the algorithm can be embedded in the data reduction and analysis module of the final device . thus , with embedded software , the algorithm runs automatically during data collection , without user input or intervention . as an example of the identification of a roadway characteristic using an algorithm with the device , skid resistance ( defined as the cumulative effect of ice , snow , water , loose materials , and the road surface on the traction produced by the wheels of a vehicle ) can be determined as a skid coefficient . the skid coefficient is calculated using the algorithm based on information gathered by the radar device on the presence or absence of ice , water , loose materials and road surface texture . as used herein , “ consisting essentially of ” does not exclude materials or steps that do not materially affect the basic and novel characteristics of the claim . any recitation herein of the term “ comprising ”, particularly in a description of components of a composition or in a description of elements of a device , system , or method , can be exchanged with “ consisting essentially of ” or “ consisting of ”. while the present invention has been described in conjunction with certain preferred embodiments , one of ordinary skill , after reading the foregoing specification , will be able to effect various changes , substitutions of equivalents , and other alterations to the compositions and methods set forth herein .