Description:
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)

A ROVER HAVING AN ELECTROMAGNETIC SCANNER AND A GLOBAL NAVIGATION SATELLITE SYSTEM (GNSS)

TECHNOLOGY INNOVATION IN EXPLORATION & MINING FOUNDATION, a company incorporated in India, having address at 3rd Floor, i2h Tower (Institute Innovation Hub), IIT(ISM) Dhanbad, Jharkhand - 826004

The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
The embodiments of the subject matter described in this specification relate to a rover having an electromagnetic scanner and a global navigation satellite system (GNSS). More particularly, the rover comprises an electromagnetic scanner and a Post Processing Kinematic (PPK) enabled global navigation satellite system (GNSS).

BACKGROUND OF THE INVENTION
Subsurface electromagnetic (EM) scanner is widely used in the form of ground penetrating radar (GPR) or surface penetrating radar (SPR). Such devices can be used in air coupling or ground coupling mode to produce the pseudo image of the subsurface with specific resolution.
Lower frequency of operation is maintained to avoid soil attenuation at high frequency due to presence of water molecules. However, higher bandwidth is required for resolution improvement.
Further, global positioning system (GPS) or any real time kinematics (RTK) based positioning technology requires established network availability for data processing. To map/ survey in remote locations where established network connectivity is unavailable, such methods may fail. In addition, a single constellation like GPS might not properly cover the entire targeted geolocation. Therefore, the object of the present invention is to solve one or more of the aforementioned issues.

SUMMARY OF THE INVENTION
The embodiments of the subject matter described in this specification relate to a rover having an electromagnetic scanner and a global navigation satellite system (GNSS). More particularly, the rover comprises an electromagnetic scanner, a modified bowtie antenna (MBA) with frequency selective surface (FSS), and a global navigation satellite system (GNSS). According, to one of the embodiments, the rover comprises (a) a USB based signal generator; (b) a USB based power meter; (c) two (2) modified bowtie antennas (MBA) integrated with frequency selective surface (FSS) reflector; (d) a processing unit; (e) a display unit; (f) a PPK enabled Global Navigation Satellite System (GNSS) module; and (g) a power unit.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention concerning the accompanying drawings and specific embodiments are described below. The following description will briefly describe the drawings used in describing the embodiments.
Figure 1(a) shows conventional bowtie antenna;
Figure 1(b) shows spline-based bowtie antenna;
Figure 1(c) shows spline-based bowtie antenna with reduced flare angle;
Figure 1(d) shows orthogonally placed dual bowtie
Figure 1(e) shows a modified bowtie antenna with cap according to an embodiment of the subject matter;
Figure 1(f) shows a modified bowtie antenna with design parameters according to an embodiment of the subject matter;
Figure 2(a) shows a front view of modified bowtie antenna according to an embodiment of the subject matter;
Figure 2(b) shows a back view of modified bowtie antenna according to an embodiment of the subject matter;
Figure 3(a) shows FSS unit cell sub component according to an embodiment of the subject matter;
Figure 3(b) shows a fabricated prototype of FSS unit cell according to an embodiment of the subject matter;
Figure 4(a) shows transmission coefficient of the FSS in TE plane for various theta according to an embodiment of the subject matter;
Figure 4(b) shows transmission coefficient of the FSS in TM plane for various theta according to an embodiment of the subject matter;
Figure 5(a) shows reflection phase of the FSS in TE plane for various theta according to an embodiment of the subject matter;
Figure 5(b) shows reflection phase of the FSS in TM plane for various theta according to an embodiment of the subject matter;
Figure 6(a) shows surface current (A/m) distribution on the 4×4 FSS array in TE mode according to an embodiment of the subject matter;
Figure 6(b) shows surface current (A/m) distribution on the 4×4 FSS array in TM mode according to an embodiment of the subject matter;
Figure 7 shows circuit model of the FSS according to an embodiment of the subject matter;
Figure 8 shows circuit simulated, EM simulated and measured transmission coefficient of the FSS according to an embodiment of the subject matter;
Figure 9(a) shows modified bowtie antenna with FSS according to an embodiment of the subject matter;
Figure 9(b) shows a prototype of modified bowtie antenna with FSS according to an embodiment of the subject matter;
Figure 10 shows reflection coefficient of modified bowtie antenna with and without FSS;
Figure 11 shows gain of modified bowtie antenna with and without FSS;
Figure 12 shows radiation efficiency of modified bowtie antenna with and without FSS;
Figure 13 shows radiation pattern of the modified bowtie antenna with and without FSS;
Figure 14(a) shows magnitude response of transfer function (S21) of modified bowtie antenna with and without FSS;
Figure 14(b) shows group delay of modified bowtie antenna with and without FSS;
Figure 15(a) shows scanned image of sub-surface in GPR test area with only a modified bowtie antenna in dry soil;
Figure 15(b) shows scanned image of sub-surface in GPR test area with modified bowtie antenna and FSS in dry soil;
Figure 15(c) shows scanned image of sub-surface in GPR test area with only a modified bowtie antenna in wet soil;
Figure 15(d) shows scanned image of sub-surface in GPR test area with modified bowtie antenna and FSS in wet soil;
Figure 16(a) shows bottom view of a rover according to an embodiment of the subject matter;
Figure 16(b) shows FSS of a rover according to an embodiment of the subject matter;
Figure 16(c) shows modified bowtie antenna and FSS of a rover according to an embodiment of the subject matter;
Figure 16(d) shows a side view of a rover according to an embodiment of the subject matter;
Figure 17 shows system diagram of the rover having an electromagnetic scanner and a global navigation satellite system (GNSS);
Figure 18 shows Post Processing Kinematics (PPK) using compact, low-cost modules at base and rover;
Figure 19(a) shows positional scatter plots of a location GPR_L1;
Figure 19(b) shows positional scatter plots of a location GPR_L2;
Figure 20(a) shows error scatter plots of a location GPR_L1;
Figure 20(b) shows error scatter plots of a location GPR_L2.

DETAILED DESCRIPTION OF THE INVENTION
A rover having an electromagnetic scanner and a PPK enabled global navigation satellite system (GNSS) is described. In one of the embodiments, the rover comprises an electromagnetic scanner, a modified bowtie antenna (MBA) with frequency selective surface (FSS), and a PPK enabled global navigation satellite system (GNSS).
According, to one of the embodiments, the rover comprises (a) a signal generator; (b) a power meter; (c) two (2) modified bowtie antenna (MBA) integrated with frequency selective screen (FSS) reflector; (d) a processing unit; (e) a display unit; (f) a Global Navigation Satellite System (GNSS) module; and (g) a power unit.
The power meter collects the power of received signal at any particular frequency. The power meter is connected to the receiving modified bowtie antenna (MBA) to exhibit the received power by receiving antenna module. The frequency selective screen (FSS) reflector is placed behind the antenna. The transmitting antenna is connected to the USB based signal generator and the receiving antenna is connected to the USB based power meter. The power unit is power bank.
According to the present invention, the sub-surface scanning uses bi-static approach where one antenna-FSS unit acts as transmitter antenna which is connected to the signal generator and the second antenna-FSS unit acts as receiver antenna which is connected to the power meter. The receiver antenna assembles the reception recurrently at a stipulated time phrase for several data emissions. Data collected at target zones which are equally spaced and the data indulgence is passed in MATLAB. The rejection of backscattered noises is processed by the singular value decomposition (SVD) technique. This technique is effective to suppress the coupling of conveying/reception antennas, back scattered-reflected wave and litter fault of miscellaneous surface. The maximum power reception is captured in all the distinct location points which is processed to realize highest signal to interfering noise ratio (SINR) in compliance of target delay (D).
Mono-static approach is also possible where single antenna unit is used as both transmitter and receiver. Further, in bi-static approach, similar measurement can be carried by connecting the transmitter and receiver antenna units to the dual port vector network analyser (VNA) where transmission coefficient (S21) data is collected and processed for scanning result. However, in case source signal is continuous RF wave only which makes the method less efficient whereas in the proposed invention, vector signal generator can be used to transmit sub nanosecond pulses even with Gaussian or it monocycle shaping which results more efficient detection results.
The modified bowtie antenna is formed from a conventional biconical dipole antenna, and has a planar compact profile and light weight with wideband coverage. Such antennas provide a characteristic impedance (Zch) which is a function of flare angle (α) and calculated as follows,
Z_ch=(377 ((γ(r))/(γ^' (r))))/√(ε_eff ) (1)
Here γ and γ’ are oblique integrals and r=〖tan〗^2 (45^0-α/2)
To develop a modified bowtie antenna structure, initially a conventional bowtie antenna (CBA) is designed as shown in Figure 1(a). As the CBA has sharp edges at the corners, phenomenon like spurious radiation is observed. The steady impedance conversion realized by bending the radiator arm produces wide spectrum coverage and also helps to get 50Ω impedance matching. To get rid of spurious radiation and achieve the desired bandwidth, the CBA is modified by introducing curvature in the peripheral of radiating arms. Thus, the CBA is designed by rounding off the edges at the corners. To attain this design, a spline is used. This is shown in Figure 1(b).
In both the cases the flare angle is kept at 180o. Flare angle plays a crucial role in the case of antenna design as it signifies the direction of propagation in the dominant mode. To accomplish the task of attaining radiation in the desired directions, two steps are followed. Initially, the θ is reduced to 60o between the existing arms of the antenna which makes it compact in nature. It is shown in Figure 1(c). In the following step additional arms are introduced with the help of mirror imaging technique. The additional arms are placed orthogonally to get desired all directional coverage. The structure is modified as bidirectional orthogonally placed dual sets of bowties with limited flare angle. Thus, reaching to the table fan shaped structure shown in Figure 1(d). To realize the targeted bandwidth, an additional circular curvature cap is attached to each of the arms as shown in Figure 1(e). The modified bowtie antenna (MBA) provides extra path for flow of surface current and helps to reduce the lower band edge frequency (fL) which is a major requirement for ground penetrating radar (GPR) antennas to realize high resolution. By introducing a rounded edge cap supplementary capacitive effect has been created between the bowtie arm and the cap. This capacitive effect in return, broadens the impedance bandwidth further.
To further enhance the impedance bandwidth, the modified bowtie antenna (MBA) structure is improved by introducing a concentric ring around the bowties with cap as depicted in Figure 1(f). The concentric ring creates an extra capacitive effect that in turns broadens the impedance bandwidth. The design parameters can be evaluated from,

f_L=c/(√(ε_eff )(4L_1+3W_1+R)) (2)
Where R=R_o (Radius of outer circle)-R_i (Radius of inner circle), effective permittivity ε_eff=√((ε_r+1)/2); εr = Relative permittivity.

The modified bowtie antenna (MBA) is fabricated using FR4 epoxy cost-effective material. It has dielectric constant εr = 4.4, loss tangent tan(δ) = 0.018 and thickness Hs = 0.8 mm. The antenna has a dimension of 0.28λ×0.28λ×0.0017λ where λ represents lower band edge frequency.
Parameter Value
(mm) Parameter Value
(mm) Parameter Value
(mm) Parameter Value
(mm)
Ls 132 Ws 132 L1 49.5 W1 28
W2 2.344 W3 15 R 2.4

Table 1: Geometrical Parameters of the Proposed Antenna

Figure 2(a) shows a front view of modified bowtie antenna according to an embodiment of the subject matter, and Figure 2(b) shows a back view of modified bowtie antenna according to an embodiment of the subject matter.
A reflective frequency selective surface (FSS) screen is designed with a stop band in the operating range of the modified bowtie antenna (MBA). The FSS is intended to be used as a reflector placed below the MBA to enhance the antenna radiation in the broadside direction. The FSS unit cell is formed by a 4×4 array of sub components that has dimensions of 53.578mm×53.578mm. As shown in Figures 3(a) and 3(b), a patch type hexagonal component cell is chosen that is surrounded by a square-like ring where the square ring is joined at the middle of hexagonal in order to achieve the desired stop band response. The FSS is designed on a high permittivity (εr= 11.2) low loss (loss tangent of 0.002) Rogers RO 3010 substrate with the thickness of 0.67 mm. The unit cell is structured by ‘L’ shaped metallic strips with a gap in between to incorporate capacitance. Variable width of the metallic strip at the joint induces two different inductances based on the current on its surface. The unit cell is chosen symmetric in order to realize polarization independence of the FSS.
The unit cell sub component dimensions are as follows: Px= Py= 13.06 mm, a= 5.48 mm, b= 1.5 mm, d= 1.4 mm, m= 2.11 mm and the gap between two consecutive components g= 0.7 mm. The FSS is analyzed in terms of fundamental characteristics such as transmission coefficient and corresponding phase response. The analysis is done using EM simulator CST Studio Suite followed by fabrication and measurements. The transmission coefficient S21 is investigated in both the TE and TM planes as shown in Figures 4(a) and 4(b) for various angles of incidence (theta).
It is observed from the plots that the stop band with S21 reference level -10 dB ranges from 0.55 GHz to 7 GHz with the resonance at 2.66 GHz for the normal incidence of plane wave leading to a bandwidth of 170.86%. In the TE (transverse electric) planes and TM (transverse magnetic) planes, the resonance does not vary significantly up to a theta value of 30 degree. This, therefore, substantiates the angular stability of the FSS. The reflection phase of the FSS in the TE and TM planes are plotted and shown in Figures 5(a) and 5(b). From the analysis of the graph shown in Figures 5(a) and 5(b), it can be observed that in both the TE and TM planes and across the certain angles of incidence (up to 300), the reflection phase of the FSS decreases linearly with frequency in the desired band of operation (0.5 GHz to 7 GHz). The linear variation of the phase makes it suitable for its use as a reflector below a bi-directional radiator in order to enhance its gain in the broadside direction. This linearly decreasing reflection phase profile ensures that the reflected signal will be co-phased to the signal towards broadside direction. Therefore, the co-phased reflected signal will be added constructively to the transmitted signal to broadside direction to enhance the antenna gain.
The surface current distribution of a 4×4 array of the FSS is analysed and the plots in TE and TM modes at various operating frequencies are depicted and shown in Figures 6(a) and 6(b). It can be observed that most of the currents are flowing through the isolated metallic strips symmetrically at all the frequencies.
The characteristic of the FSS is verified using its equivalent circuit model as shown in Figure 7. The equivalent circuit for the FSS is designed with LC components modelled from the observation of the surface current distribution. The circuit contains two similar LC resonators connected in cascade each made of the combination of series and shunt LC components. Each LC resonator models two vertical L shaped strips separated by a gap ‘d’ as shown in Figures 3(a) and 3(b). The electric field in the gap between two consecutive unit cells is represented by the capacitor C1 whereas the L1 models the current flow in the horizontal section of the ‘L’ shaped strip. The series combination of L2, L3 and C2 are used to model the vertical sections of the strips and the gap between them respectively. The gap between horizontal sections of the ‘L’ shaped strip in the unit cell is modelled using the capacitor C3.
The substrate is modelled using the transmission line consisting of series inductor Ls and shunt capacitance Cs. This inductor is calculated using LS= μ0μrh and the capacitor that models the substrate is calculated using CS= ε0εrh where h= 0.67 mm is the substrate thickness. The two ends of the FSS are modelled using impedances ZT1 and ZT2 which are equivalent to the free space impedance of 377 Ohms. The LC values are estimated from the below mentioned equations. The effective permittivity ɛeff in the equations is estimated using ɛeff = (ɛr+1)/2 where ɛr= 11.2 is the relative permittivity of the dielectric substrate. Similarly, the effective permeability μeff corresponds to (μr+1)/2 where μr= 1. The value of P corresponds to periodicity of Px=Py. In the equations t= 0.035 mm is the thickness of the copper layer of the strips.
C1 = ε_0 ε_eff 2P/π ln⁡(1/(□sin sin (π×g)/2P )) (3)
L1 = μ_0 μ_eff P/2π □ln ln (1/(□sin sin (π×m)/2P )) (4)
L2 = L3 = μ_0 μ_eff P/2π □ln ln (1/(□sin sin (π×b)/2P )) (5)
C2 = ε_0 ε_eff 2P/π ln⁡(1/(□sin sin (π×d)/2P )) (6)
C3 = (ε_0×ε_eff×b×t)/((2a+d)) (7)
The values of free space permittivity and permeability are used as ε0 = 8.85×10-12 F/m and μ0= 4π×10-7 H/m. The LC values are initially calculated from the above equations followed by fine tuning in the ADS simulator. The finally estimated values are: C1 = 2900 fF, L1 = 1.1 nH, L2 = L3 = 1.4 nH, C2 = 1900 fF, and C3 = 1.5 fF whereas Ls = 5 nH and Cs = 25 fF. The circuit model is simulated using ADS and the transmission coefficient achieved from circuit simulation is plotted as shown in Figure 8 along with the S21 obtained using EM simulator CST-MWS. The S21 obtained from the measurement of the fabricated 4×4 array of the FSS is also included in the same plot. It is evident that circuit simulated result and the measured result are closely related to the EM simulated one.
The modified bowtie antenna (MBA) is integrated to the FSS based reflector. The air gap between the proposed bowtie antenna and the FSS based reflector is finalized based on extensive parametric analysis. The final selected air gap is 140mm that is close to λ/4. Figure 9(a) shows modified bowtie antenna with FSS according to an embodiment of the subject matter. As shown in Figure 9(b), the antenna hardware and FSS hardware are cascaded using foam as it has electric property close to air.
The performance analysis of modified bowtie antenna (MBA) with frequency selective surface (FSS) is studied by both EM simulation in CST microwave studio suite and experimental study. The reflection coefficient (S11) of the composite structure is plotted and shown in Figure 10. Clearly, the antenna itself offers an impedance bandwidth from 0.64 to 3.05 GHz with prominent resonances at 1GHz and 2.7GHz. Addition of FSS to the back of the antenna as a reflector unchanged the impedance bandwidth. However, the second resonance has a minor shift to 2.6GHz. Decent pact amid the CST plots and measured plots can be detected.
Gain of the MBA with and without FSS are plotted and shown in Figure 11. The MBA offers a gain variation between 3-5.5 dBi which indicates a steady gain profile. However, this gain value is comparatively lower for scanning applications. Integration of FSS ensures gain augmentation that is maximum of 5.3dBi at 2.8GHz. The MBA-FSS composite structure offers a gain variation from 6 to 10.5 dBi which is much higher than the gain of an MBA excluding FSS.
High radiation efficiency is a much-desired characteristic of GPR antennas for better scanning resolution. As shown in Figure 12, the MBA offers simulated radiation efficiency of about 97% on an average over the impedance. The measured data suggested the average radiation efficiency value of 85% throughout the working spectrum. Addition of FSS does not alter the radiation efficiency profile which is a vital outcome. The MBA efficiency is measured following the modified wheeler cap method. An average variation of 10-12% among the simulated and measured study is expected of this method due to the assumptions made in wheelers strategy. Several assumptions are made in the wheelers cap method such as:
The metallic box completely suppresses radiation from the antenna, such that any power supplied to the antenna with shield is dissipated as ohmic losses in the antenna structure.
The metallic box alters only the radiated power and does not significantly affect the antenna's stored reactive energy or impedance due to near-field interactions.
The ohmic and dielectric losses of the antenna remain the same whether the metal shield is present or not.
The metallic box is sufficiently large to completely enclose the radiating parts of the antenna and prevent any leakage of radiation.
The antenna behaves linearly, meaning the input power and resulting losses follow a predictable and proportional relationship.
The metallic shield itself introduces no significant additional losses, such as eddy current losses or resistive heating in the cap material.
The measurements of input impedance and power (both with and without the cap) are accurate and free from external interference, noise, or calibration errors.
Such assumptions are very difficult to maintain at the time of practical measurement of antenna radiation efficiency following the wheeler cap method which is the reason behind deviation in measured efficiency value compared to the simulated data.
Further, the simulated and measured radiation efficiency data are generated at some distinct frequency point. The difference of radiation efficiency value obtained by experimental measurement to the simulated value is ranging from 2% at 3GHz (minimum) to 17% at 1.75GHz (maximum). The average of this difference is 10-12%.
Radiation characteristic of the single MBA and MBA-FSS is compared and shown in Figures 13(a) to 13(f). Apparently, the antenna gives non-directional H-plane and bidirectional E-plane patterns similar to any wideband monopole antenna. However, the cascading of FSS results in boosting the broadside radiation and reduces the back radiation significantly in all the frequencies over the impedance bandwidth. This outcome is highly desired as it signifies better depth resolution of the GPR antenna.
Magnitude response of antenna transfer function (|S21|) and group delay (GD) is studied by keeping two similar ‘bowtie antenna-FSS’ prototypes in face-to-face and side-by-side conformations. This study is vital to identify the dispersiveness of the proposed composite structure. As depicted in Figures 14(a) and 14(b), The ‘bowtie antenna-FSS’ exhibits linear |S21| (variation less than 12 dB) and flat GD (variation lower than 2ns) responses over the working spectrum which justify the non-dispersive nature of the integrated antenna-FSS structure for both the conformations.
The description will briefly describe the drawings used in describing the embodiments.
Figure 1(a) shows conventional bowtie antenna;
Figure 1(b) shows spline-based bowtie antenna;
Figure 1(c) shows spline-based bowtie antenna with reduced flare angle;
Figure 1(d) shows orthogonally placed dual bowtie
Figure 1(e) shows a modified bowtie antenna with cap according to an embodiment of the subject matter;
Figure 1(f) shows a modified bowtie antenna with design parameters according to an embodiment of the subject matter;
Figure 2(a) shows a front view of modified bowtie antenna according to an embodiment of the subject matter;
Figure 2(b) shows a back view of modified bowtie antenna according to an embodiment of the subject matter;
Figure 3(a) shows FSS unit cell sub component according to an embodiment of the subject matter;
Figure 3(b) shows a fabricated prototype of FSS unit cell according to an embodiment of the subject matter;
Figure 4(a) shows transmission coefficient of the FSS in TE plane for various theta according to an embodiment of the subject matter;
Figure 4(b) shows transmission coefficient of the FSS in TM plane for various theta according to an embodiment of the subject matter;
Figure 5(a) shows reflection phase of the FSS in TE plane for various theta according to an embodiment of the subject matter;
Figure 5(b) shows reflection phase of the FSS in TM plane for various theta according to an embodiment of the subject matter;
Figure 6(a) shows surface current (A/m) distribution on the 4×4 FSS array in TE mode according to an embodiment of the subject matter;
Figure 6(b) shows surface current (A/m) distribution on the 4×4 FSS array in TM mode according to an embodiment of the subject matter;
Figure 7 shows circuit model of the FSS according to an embodiment of the subject matter;
Figure 8 shows circuit simulated, EM simulated and measured transmission coefficient of the FSS according to an embodiment of the subject matter;
Figure 9(a) shows modified bowtie antenna with FSS according to an embodiment of the subject matter;
Figure 9(b) shows a prototype of modified bowtie antenna with FSS according to an embodiment of the subject matter;
Figure 10 shows reflection coefficient of modified bowtie antenna with and without FSS;
Figure 11 shows gain of modified bowtie antenna with and without FSS;
Figure 12 shows radiation efficiency of modified bowtie antenna with and without FSS;
Figure 13 shows radiation pattern of the modified bowtie antenna with and without FSS;
Figure 14(a) shows magnitude response of transfer function (S21) of modified bowtie antenna with and without FSS;
Figure 14(b) shows group delay of modified bowtie antenna with and without FSS;
Figure 15(a) shows scanned image of sub-surface in GPR test area with only a modified bowtie antenna in dry soil;
Figure 15(b) shows scanned image of sub-surface in GPR test area with modified bowtie antenna and FSS in dry soil;
Figure 15(c) shows scanned image of sub-surface in GPR test area with only a modified bowtie antenna in wet soil;
Figure 15(d) shows scanned image of sub-surface in GPR test area with modified bowtie antenna and FSS in wet soil;
Figure 16(a) shows bottom view of a rover according to an embodiment of the subject matter;
Figure 16(b) shows FSS of a rover according to an embodiment of the subject matter;
Figure 16(c) shows modified bowtie antenna and FSS of a rover according to an embodiment of the subject matter;
Figure 16(d) shows a side view of a rover according to an embodiment of the subject matter;
Figure 17 shows system diagram of the rover having an electromagnetic scanner and a global navigation satellite system (GNSS);
Figure 18 shows Post Processing Kinematics (PPK) using compact, low-cost modules at base and rover;
Figure 19(a) shows positional scatter plots of a location GPR_L1;
Figure 19(b) shows positional scatter plots of a location GPR_L2;
Figure 20(a) shows error scatter plots of a location GPR_L1;
Figure 20(b) shows error scatter plots of a location GPR_L2.
EXPERIMENT AND RESULTS
Test Field Set up Experimental setup
The scanning test area of dimension 20feet×10feet is prepared at the playground of NIT Jamshedpur as shown in Figure 16(b). The scanning is performed in some discrete points of uniform distances along the marked lines covering the targeted test points. Two targeted test points are prepared where very thin metal (aluminum) sheets are buried at a thickness of 1 meter and 1.5 meter respectively. The lattepanda board is getting its required power from a power bank, placed at the middle of the cart. The signal generator, power meter and UBLOX boards are connected to the lattepanda board. Gaussian monocycle as expressed in equation 8, is generated from source and transmitted by Tx antenna at a start frequency 600 MHz with transmitting power of -10 dBm. Stop frequency is fixed at 3 GHz with IF bandwidth 2.4 GHz and frequency step size 10 MHz. The Rx antenna, connected to the power meter, collects the receiving data continually for a preset time period for multiple transmissions. The Tx and Rx antennas are placed in proximity to the ground surface of the test area. The data collection was carried at discrete points with uniform spacing of six inches. The data dispensation is carried in the MATLAB simulator. Background cancellation is carried using the singular value decomposition (SVD) method. SVD approach is used to mitigate the coupling between Tx and Rx antennas, reflection from ground and clutter error of diverse soil. The received signal with highest power among all transmissions at any particular location is stored and processed further to ensure maximum signal to interference (SIR) ratio conforming to target delay (τ) which is nothing but a matched filter approach.
p(t)=A{1-4π((t-T_c)/T_d )^2}×exp⁡{-2π((t-T_c)/T_d )^2} (8)
Here A is amplitude, T_d is pulse width. The target delay (τ) can be calculated from,

τ=(2√(ε_e ))/c×√(〖(d-x_1)〗^2+y_1^2 ) (9)
The received signal (r(t)) is processed for maximizing SIR to get the outcome (y(t)) from,
y(t)=r(t)*h(t)=∫_(-∞)^∞ r(φ)h(t-φ)dφ (10)
Where the matched filter impulse response h(t) is calculated from,
h_opt (t)=αp(τ-t);0≤t≤τ (11)
here α is a matched filter constant that is assumed to be 1.
Four different measurement environments with two variation categories are considered. In the first category the variation is in the MBA with and without FSS based reflector. In the second category of variation the soil type is varied from dry soil to wet soil. The scanned results, generated in MATLAB for all four experimental environments are shown in Figures 15(a) to 15(d).
Result
The results clearly show that a better scan resolution is realized while MBA is added with FSS reflector as it signifies improved depth resolution due to radiation improvement in the direction of interest. Also, the presence of water molecules in case of wet soil is more which increases the attenuation of transmitted waves. The scanned images to identify the metal sheet location has better clarity for dry soil subsurface than the wet soil sub surface as depicted in Figures 15(c) and 15(d). Further the image of buried objects at lower depth (1 meter) is more prominent compared to the buried object of greater depth (1.5 meter) which is a well expected outcome.
A similar experiment was also carried at NIT Children Park where similar result was obtained.
In preferred embodiments, the rover comprising an electromagnetic scanner and global navigation satellite system is described. The rover comprises:
an USB based signal generator;
an USB base Power meter;
two similar MBA with uniplanar FSS reflectors;
a lattepanda board with display;
an UBLOX ZED F9P with ANN patch antenna; and
a power bank to supply power to the lattepanda board.
Two similar MBAs with uniform uniplanar FSS as reflector are integrated at the bottom of the rover as shown in Figures 16(a) to 16(d). Replacing the conventional GPR measurement from S21 measurement using vectored network analyzer (VNA), here a USB based signal generator is integrated to the transmitting antenna and USB based power meter is connected to the receiver antenna. Apart from scanning, PPK based positioning with precision also aims to achieve for which UBLOX ZED F9P with ANN patch antenna is integrated and placed on top of the rover. All these components are connected to the Latte Panda board and placed on top of the cart as shown in Figure 17.
The signal generator can be USB based so that it can be used for field study. Also, it is better to have vector signal generator so that it can produce nano second pulses with gaussian (or any of its derivative) shaped pulses. However, USB based RF signal generator can also be used where scanned images need to processed further for echo cancellation as significant echoes will be present in the received signal for RF signal generator.
The Power Meter can be USB based so that it can be used for field study.
UBLOX ZED F9P is used which is a low cost multi GNSS board that supports RTK and PPK. Any multi GNS RTK and PPK enable portable board can be used in place of UBLOX ZED F9P.
Lattepanda is a pocket computer. Raspberry Pi board/notepad/laptop can also be used in place of Lattepanda board.
All these products can be procured from any company with compatible specifications.

ROVER SETUP AND METHODOLOGY

Experimental setup

Setting up the base station in Satellite Navigation Laboratory (SNL), NIT Jamshedpur using a compact, low-cost dual-frequency multi-GNSS receiver module, the uBlox ZED F9P, paired with a low-cost survey-grade antenna (SKYTRAQ) installed on a rooftop with an open sky view. To ensure precise base station location, an online Precise Point Positioning (PPP) service is utilized, processing 24 hours of GPS+GLONASS data logged at a 1 Hz rate. At the Rover end, a different configuration of the uBlox ZED F9P module and an uBlox ANN patch antenna is employed. The GNSS module connected to lattepanda board via USB, is set up to deliver raw data in .ubx format using a hybrid mode of multi-constellation GNSS: GPS (L1 and L2), Galileo (E1 and E5), and QZSS (L1). Concurrent data is collected for one hour at various Rover locations with different baseline distances from the Base. The hybrid-GNSS mode ensures continuous data collection at both ends.

Post-processing software is used to correct for minor discrepancies in data collection time spans. Data collected through UBLOX are processed in RTKLib software, and thereafter corrections are made by further processing through MATLAB. Figure 18 shows the data recording setup of the low-cost Post Processing Kinematics (PPK) system. After each data collection campaign for a specific Rover location, the data from both the Base and Rover endpoints are combined for further post-processing to achieve accurate geolocation of buried objects.

GNSS data from the Base and Rover are post-processed using the open-source RTKLib software (version 2.4.3_b33) for PPK solutions. The .ubx raw files from both GNSS modules are first converted to Receiver Independent Exchange Format (RINEX) files using RTKCONV, a utility within RTKLib. These RINEX files are then input into RTKPOST, another RTKLib utility, for post-processing. This generates navigation solutions for various Rover locations, which are analyzed further. Any software that supports RTK and PPK can be used for post-processing purpose.
To validate the PPK integration with GPR, two locations with buried metals are selected. The PPK Rover system, integrated with GPR, collects data for 30 minutes at each location using a multi-GNSS mode at a 1 Hz data rate. The collected data is transferred to the Base station and processed using the same methodology described above, allowing for an assessment of the PPK-enhanced GPR performance in detecting buried objects.
Navigation results and discussion
In this study, the performance of the PPK technique is evaluated for short-baseline lengths (≤ 3 km). GNSS data is collected at a 1 Hz rate in multi-GNSS mode for one hour at each test location for PPK analysis. The evaluation involves calculating both two-dimensional (2D) and three-dimensional (3D) positional parameters using compact, low-cost GNSS modules.
The precision of position solutions is assessed based on Distance Root Mean Square (2DRMS), Circle of Error Probable (CEP), Spherical Error Probable (SEP), and Mean Radial Spherical Error (MRSE) relative to PPP coordinates. These metrics, detailed in Table 2, reflect the solution quality at different baseline distances. To compute these precision parameters, standard deviations in latitude, longitude, and altitude are determined. Specifically, σ_x represents the standard deviation in the east direction, σ_yin the north direction, and σ_z in the vertical direction. These metrics are used to evaluate the accuracy and reliability of the PPK solution.
(12)
(13)
(14)
(15)

2DRMS indicates the radius of a circle where 95.8% to 98.2% of position solutions are present. CEP represents the radius of a circle within which 50% of the solutions lie. SEP is the radius of a sphere containing 50% of the 3D position estimates, while MRSE is the radius within which 61% of the 3D estimates are found.

Rover Location
Accuracy (m) Aerial Distance from Base station (km)
2D 3D
2DRMS CEP SEP MRSE
A 0.0261 0.0143 0.0358 0.1885 0.061
B 0.0315 0.0210 0.0460 0.3084 0.212
C 0.0367 0.0591 0.0793 0.5694 2.469

Table 2. Short Baseline PPK Analysis using hybrid constellation GPS+Galileo+QZSS for 30 minutes data @1Hz
The study demonstrates that PPK solutions achieve sub-40 cm accuracy within a 2.5 km baseline. Accuracy slightly deteriorates with increased baseline length. Key factors for achieving high accuracy include selecting sites with an unobstructed sky view, ensuring common satellite visibility, and proper antenna placement.
For the analysis, points with an aerial distance of 117.49 cm were chosen. The location results from PPK analysis, using a hybrid GNSS constellation (GPS+Galileo+QZSS), are detailed in Table 3. The position solution quality is assessed through 2D and 3D precision parameters, with the results presented in Table 3. This evaluation provides insights into the performance of the PPK system under the given conditions.
Rover Location
Aerial Distance 2D Precision(m) 3D Precision(m)
2DRMS CEP SEP MRSE
GPR_L1 (22.77756994o N, 85.15000575o E) 117.49 cm 0.0164 0.1634 0.7951 0.8361
GPR_L2 (22.7775601o N, 86.15000188 o E) 0.2340 0.3346 0.5725 0.5523

Table 3. PPK integrated with GPR Positional Performance analysis

Figures 19 and 20 show the position scatter plot and error scatter plot for two locations. The scatter plots show the distribution of east and north errors, highlighting the variation in errors obtained. The surrounding circle on the scatter plot represents the probable confidence interval, illustrating where most of the errors lie. Both plots reveal that errors are clustered around the central points, indicating that the PPK method generally delivers precise solutions. The observed errors suggest that PPK accuracy is influenced by factors such as satellite geometry and environmental conditions. Despite these influences, the PPK system consistently outperforms standalone GNSS in terms of solution accuracy. This high level of precision is crucial for applications demanding exact positioning, demonstrating the effectiveness of PPK in providing reliable and accurate geolocation data.
INDUSTRIAL APPLICABILITY AND ECONOMIC SIGNIFICANCE
The modified bowtie antenna with frequency selective surface (FSS), and a rover has vast industrial applicability:
As ground penetrating radar for sub-surface scanning (up to 2 meter depth) with precise location information.
Sub-surface mapping with positioning.
Civil applications
Military Applications
Coal-Mine Application for detection of mining zone with precise positioning and identification of buried objects/human beings in post disaster rescue operation.
Disaster Management and rescue.

Advantages:
Em-scanning to produce the pseudo image of subsurface.
Positioning with centimeter level precision.
It can work even with non-availability of existing wireless network and Internet connectivity.
It can be used for areas not covered by any specific positioning constellation such as GPS.
It can be made truly based on Indian Constellation NAVIC also when in future the same will be deployed.
The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the disclosure.
, Claims:I/We claim:
1. A rover comprises:
a. a signal generator;
b. two (2) modified bowtie antenna (MBA) integrated with frequency selective screen (FSS) reflector;
c. a power meter connected to the modified bowtie antenna (MBA);
d. a processing unit;
e. a display unit;
f. a PPK enabled Global Navigation Satellite System (GNSS) module; and
g. a power unit.
2. A rover as claimed in claim 1, wherein the signal generator is a USB based signal generator.
3. A rover as claimed in claim 1, wherein the power meter is a USB based power meter.
4. A rover as claimed in claim 1, wherein the modified bowtie antenna (MBA) has a table fan like shaped structure with concentric ring around the bowties with cap.
5. A rover as claimed in claim 5, wherein the concentric ring of the modified bowtie antenna (MBA) creates an extra capacitive effect that in turns broadens the impedance bandwidth.
6. A rover as claimed in claim 1, wherein the modified bowtie antenna (MBA) offers simulated radiation efficiency of about 97% on an average over the impedance and the average radiation efficiency value of 85% throughout the working spectrum.
7. A rover as claimed in claim 1, wherein the modified bowtie antenna (MBA) accomplishes the task of attaining radiation in the desired directions.
8. A rover as claimed in claim 1, wherein the modified bowtie antenna (MBA) is fabricated using FR4 epoxy cost-effective material.
9. A rover as claimed in claim 1, wherein the FSS reflector comprises a plurality of FSS unit cells.
10. A rover as claimed in claim 8, wherein the FSS unit cell is of patch type hexagonal component cell surrounded by a square-like ring joined at the middle of hexagonal to achieve the desired stop band response.
11. A rover as claimed in claim 8, wherein the FSS unit cell has sub component dimensions of Px= Py= 13.06 mm, a= 5.48 mm, b= 1.5 mm, d= 1.4 mm, m= 2.11 mm and the gap between two consecutive components g= 0.7 mm.
12. A rover as claimed in claim 1, wherein the FSS reflector is formed by a 4×4 array of FSS unit cells that has dimension of 53.578mm×53.578mm.
13. A rover as claimed in claim 1, wherein FSS reflector is used as a reflector placed below the modified bowtie antenna (MBA) to enhance the antenna radiation in the broadside direction.
14. A rover as claimed in claim 1, wherein air gap between the modified bowtie antenna (MBA) and the frequency selective screen (FSS) reflector is 140mm that is close to λ/4.
15. A rover as claimed in claim 1, wherein the composite structure of modified bowtie antenna (MBA) and the frequency selective screen (FSS) reflector offers a gain variation from 6 to 10.5 dBi.
16. A rover as claimed in claim 1, wherein the processing unit comprises a display.
17. A rover as claimed in claim 1, wherein the processing unit is lattepanda board which is connected to signal generator, the power meter, the Global Navigation Satellite System (GNSS) module, and display unit.
18. A rover as claimed in claim 1, wherein the GNSS module comprises a GNSS system and an antenna.
19. A rover as claimed in claim 1, wherein the GNSS module comprises an uBlox ZED F9P module and an uBlox ANN patch antenna.
20. A rover as claimed in claim 1, wherein the processing unit is configured for post-processing to correct for minor discrepancies in data collection time spans are corrected through.