Complementary Metal-oxide-semiconductor Active Pixel Sensor Research Articles

Application of an in-house developed complementary metal-oxide-semiconductor-based optical computed tomography (CMOS-OCT) imaging system for stereotactic radiosurgery dosimetry using a PRESAGE® dosimeter

PRESAGE® dosimeter can be useful for 3D verification of radiotherapy treatment delivery when careful attention is given to the dosimeter measurement technique. Ideally, a low noise and fast optical CT scanning system is required for imaging the dosimeter for verification of advanced radiotherapy treatment delivery. We have developed a complementary metal-oxide-semiconductor (CMOS)-based optical computed tomography (OCT) system (CMOS-OCT), implementing the recent advances in CMOS active pixel sensor (APS) technology that offer on-chip image processing and high-speed readout. In this study, we present the dosimetric response of irradiated PRESAGE® dosimeter measured with the CMOS-OCT system and describe a feasibility study of using the calibrated system to verify stereotactic radiosurgery (SRS) treatment. PRESAGE® dosimeters were irradiated using a 6 MV Elekta Synergy linear accelerator to investigate dosimetric and geometric properties of PRESAGE® dosimeter with CMOS-OCT imaging system, in order to verify a clinical SRS treatment plan of the brain. The tomographic projection images of the PRESAGE® dosimeter were captured by the image sensor within 100 s for a 360-degree rotation. The CMOS-OCT imaging system showed good linearity in dose-response measured by PRESAGE® dosimeter. The correlation of the optical density (OD) changes measured from the CMOS-OCT with attenuation value measured using a calibrated UV/Vis spectrophotometer was found to be better than 0.996. The tomographic reconstruction of the dose distribution from the PRESAGE® showed good agreement when compared with the calculated dose distributions from the treatment planning software. The in-house CMOS-OCT imaging system is capable of visualising and verifying the dose distribution of stereotactic radiosurgery treatment. The CMOS-OCT imaging of the PRESAGE® dosimeter provides accurate dosimetric and geometric information on radiotherapy delivery in a three-dimensional volume, which is useful in advanced radiotherapy. The introduction of CMOS technology in the OCT improves the imaging speed of the dosimeters dose readout.

Influence mechanism and recognition algorithm of CMOS active pixel sensor radiation damage on star sensor star map recognition

In order to analyze the causes of star sensor performance degradation and attitude measurement accuracy reduction in space radiation environment, the total ionizing dose effects on complementary metal oxide semiconductor (CMOS) star sensor performance are studied. By using an established outfield star sensor test system, the Orion Nebula and the zenith direction of the sky are imaged. Through the experimental processes of star map data acquisition, star point extraction and star map matching, the influence mechanisms of complementary metal oxide semiconductor active pixel sensor (CMOS APS) noises on background gray mean value of star map and number of identified stars are analyzed. A recognition algorithm for finding stars annihilated by radiated noise is proposed. Through theoretical derivation, the quantitative relationships between CMOS APS dark current noise, dark signal non-uniformity noise and photon response non-uniformity noise and star centroid positioning error are established. The γ radiation results show that the image gray-mean of the whole star map increases, the number of identified stars decreases, and the star point centroid positioning accuracy decreases, which seriously affect star map recognition of star sensor. This research provides a theoretical basis for the radiation-resistant reinforcement design of high precision star sensors.

Power-law analysis of nonlinear active-pixel detector responses as a function of mammographic energy

Abstract This study investigates the imaging performance of a complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) array coupled with a gadolinium oxysulfide phosphor. A wide range of mammographic energy was considered, which corresponds to an aluminum-equivalent thickness in the range of 0.515 to 0.689 mm in terms of half-value layers. The performance metrics include the modulation-transfer function (MTF), Wiener noise-power spectrum (NPS), and detective quantum efficiency (DQE). The detector showed a nonlinear response at low exposure ranges, so it was described using a power-law model to linearize image data before evaluating the MTF, NPS, and DQE. We show that the NPS, which is measured from images without linearization but corrected by the exponent of the power function (viz., nonlinearity correction), can be consistent with that obtained using the linearization procedure. Negligible difference in MTFs measured with and without linearization showed good agreement between the nonlinearity-corrected and linearized DQEs. The DQE performance of the detector was comparable to published data for conventional digital mammography detectors. However, the detector design with a CMOS APS array in conjunction with a thin phosphor was energy-sensitive. The overall spatial-resolution performance (the size of effective aperture) improved by about 13%, the noise performance was degraded by about 22%, and the zero-frequency DQE was reduced by about 26% when measured with a Mo-target beam quality of 25 kV to 31 kV and a similar exposure of about 6 mR. The detector design may be appropriate for operation in a narrow range of energy. Further design considerations of the phosphor with output that tolerates variations in energy could lead to applications in convertible mammography and tomosynthesis.

Analysis of proton and γ-ray radiation effects on CMOS active pixel sensors**Project supported the National Natural Science Foundation of China (Grant No. 11675259), the West Light Foundation of the Chinese Academy of Sciences (Grant Nos. XBBS201316, 2016-QNXZ-B-2, and 2016-QNXZ-B-8), and Young Talent Training Project of Science and Technology, Xinjiang, China (Grant No. qn2015yx035).

Radiation effects on complementary metal–oxide–semiconductor (CMOS) active pixel sensors (APS) induced by proton and γ-ray are presented. The samples are manufactured with the standards of CMOS technology. Two samples have been irradiated un-biased by 23 MeV protons with fluences of and , respectively, while another sample has been exposed un-biased to 65 krad(Si) 60Co γ-ray. The influences of radiation on the dark current, fixed-pattern noise under illumination, quantum efficiency, and conversion gain of the samples are investigated. The dark current, which increases drastically, is obtained by the theory based on thermal generation and the trap induced upon the irradiation. Both γ-ray and proton irradiation increase the non-uniformity of the signal, but the non-uniformity induced by protons is even worse. The degradation mechanisms of CMOS APS image sensors are analyzed, especially for the interaction induced by proton displacement damage and total ion dose (TID) damage.

Three-dimensional cascaded system analysis of a 50 µm pixel pitch wafer-scale CMOS active pixel sensor x-ray detector for digital breast tomosynthesis

High-resolution, low-noise x-ray detectors based on the complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) technology have been developed and proposed for digital breast tomosynthesis (DBT). In this study, we evaluated the three-dimensional (3D) imaging performance of a 50 µm pixel pitch CMOS APS x-ray detector named DynAMITe (Dynamic Range Adjustable for Medical Imaging Technology). The two-dimensional (2D) angle-dependent modulation transfer function (MTF), normalized noise power spectrum (NNPS), and detective quantum efficiency (DQE) were experimentally characterized and modeled using the cascaded system analysis at oblique incident angles up to 30°. The cascaded system model was extended to the 3D spatial frequency space in combination with the filtered back-projection (FBP) reconstruction method to calculate the 3D and in-plane MTF, NNPS and DQE parameters. The results demonstrate that the beam obliquity blurs the 2D MTF and DQE in the high spatial frequency range. However, this effect can be eliminated after FBP image reconstruction. In addition, impacts of the image acquisition geometry and detector parameters were evaluated using the 3D cascaded system analysis for DBT. The result shows that a wider projection angle range (e.g. ±30°) improves the low spatial frequency (below 5 mm−1) performance of the CMOS APS detector. In addition, to maintain a high spatial resolution for DBT, a focal spot size of smaller than 0.3 mm should be used. Theoretical analysis suggests that a pixelated scintillator in combination with the 50 µm pixel pitch CMOS APS detector could further improve the 3D image resolution. Finally, the 3D imaging performance of the CMOS APS and an indirect amorphous silicon (a-Si:H) thin-film transistor (TFT) passive pixel sensor (PPS) detector was simulated and compared.

Development of cluster count algorithm for radiation measurement using complementary metal oxide semiconductor camera

Complementary metal oxide semiconductor (CMOS) camera was used as radiation detector. The methodology to use CMOS active pixel sensor for radiation monitoring purpose is discussed. A new cluster count algorithm to measure dose rates from the images captured using the commonly available CMOS cameras in cell phones and tablets for gamma radiation measurement was developed and implemented on personal computer (PC). Images were taken in standard gamma fields and analyzed on PC to generate the calibration coefficients. The algorithm was validated using 60Co source for dose rates up to 10 Gy/h by images captured on Samsung Galaxy GT-6800 tablet. The algorithm was also tested using other radiation sources such as 137Cs, 241Am, and X-rays for different dose rates.

Design of a Low Noise Active Pixel Sensor using Complementary Metal-Oxide-Semiconductor Technology

In this paper, our focus is on designing of complementary metal-oxide-semiconductor (CMOS) photodiode based active pixel sensor (APS) and performance analysis and achievements for CMOS image sensor. Different important design parameters like photocurrent, conversion gain, conversion factor, dynamic range, readout speed, and quantum efficiency have been calculated. Noise is also considered for the design at different phase of operations of CMOS APS. Various design parameters of our design are computed and compared with simulated results. Noise calculation shows that the pixel noise is dominated by reset noise.

Design and Analysis of High Frame Rate Capable Active Pixel Sensor by Using CNTFET Devices for Nanoelectronics

This paper presents a high frame rate capable Active Pixel Sensor (APS) using Carbon Nanotube Field Effect Transistor (CNTFET) instead of Complementary Metal Oxide Semiconductor (CMOS). Conventionally, the design of a single APS circuit is based on three transistors (3T) model. In order to achieve higher frame rate, one extra transistor with a column sensor circuit has been introduced in the proposed design to reduce the readout time. This study also concerns about the effect of transistor sizing, bias current, and moreover, the chiral vector of CNTFET. The power consumption and power delay product (PDP) are also investigated for specific sets of reset and row selector signal. Data for these studies were collected with the help of HSPICE software which were further plotted in OriginPro to analyze the optimal operation point of APS circuit. The bias current was also recorded for the readout transistor which is uniquely introduced in the proposed model for achieving better readout time. Hence, the main focus of this paper is to improve the frame rate by reducing the readout time. Results of the proposed CNTFET APS circuit are compared with the conventional CMOS APS circuit. The performance benchmarking shows that CNTFET APS cell significantly reduces readout time, PDP, and thus can achieve much higher frame rate than that of conventional CMOS APS cell.

Large area CMOS active pixel sensor x-ray imager for digital breast tomosynthesis: Analysis, modeling, and characterization.

Large area x-ray imagers based on complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) technology have been proposed for various medical imaging applications including digital breast tomosynthesis (DBT). The low electronic noise (50-300 e-) of CMOS APS x-ray imagers provides a possible route to shrink the pixel pitch to smaller than 75 μm for microcalcification detection and possible reduction of the DBT mean glandular dose (MGD). In this study, imaging performance of a large area (29×23 cm2) CMOS APS x-ray imager [Dexela 2923 MAM (PerkinElmer, London)] with a pixel pitch of 75 μm was characterized and modeled. The authors developed a cascaded system model for CMOS APS x-ray imagers using both a broadband x-ray radiation and monochromatic synchrotron radiation. The experimental data including modulation transfer function, noise power spectrum, and detective quantum efficiency (DQE) were theoretically described using the proposed cascaded system model with satisfactory consistency to experimental results. Both high full well and low full well (LFW) modes of the Dexela 2923 MAM CMOS APS x-ray imager were characterized and modeled. The cascaded system analysis results were further used to extract the contrast-to-noise ratio (CNR) for microcalcifications with sizes of 165-400 μm at various MGDs. The impact of electronic noise on CNR was also evaluated. The LFW mode shows better DQE at low air kerma (Ka<10 μGy) and should be used for DBT. At current DBT applications, air kerma (Ka∼10 μGy, broadband radiation of 28 kVp), DQE of more than 0.7 and ∼0.3 was achieved using the LFW mode at spatial frequency of 0.5 line pairs per millimeter (lp/mm) and Nyquist frequency ∼6.7 lp/mm, respectively. It is shown that microcalcifications of 165-400 μm in size can be resolved using a MGD range of 0.3-1 mGy, respectively. In comparison to a General Electric GEN2 prototype DBT system (at MGD of 2.5 mGy), an increased CNR (by ∼10) for microcalcifications was observed using the Dexela 2923 MAM CMOS APS x-ray imager at a lower MGD (2.0 mGy). The Dexela 2923 MAM CMOS APS x-ray imager is capable to achieve a high imaging performance at spatial frequencies up to 6.7 lp/mm. Microcalcifications of 165 μm are distinguishable based on reported data and their modeling results due to the small pixel pitch of 75 μm. At the same time, potential dose reduction is expected using the studied CMOS APS x-ray imager.

Predicted image quality of a CMOS APS X-ray detector across a range of mammographic beam qualities

Digital X-ray detectors based on Complementary Metal-Oxide- Semiconductor (CMOS) Active Pixel Sensor (APS) technology have been introduced in the early 2000s in medical imaging applications. In a previous study the X-ray performance (i.e. presampling Modulation Transfer Function (pMTF), Normalized Noise Power Spectrum (NNPS), Signal-to-Noise Ratio (SNR) and Detective Quantum Efficiency (DQE)) of the Dexela 2923MAM CMOS APS X-ray detector was evaluated within the mammographic energy range using monochromatic synchrotron radiation (i.e. 17-35 keV). In this study image simulation was used to predict how the mammographic beam quality affects image quality. In particular, the experimentally measured monochromatic pMTF, NNPS and SNR parameters were combined with various mammographic spectral shapes (i.e. Molybdenum/Molybdenum (Mo/Mo), Rhodium/Rhodium (Rh/Rh), Tungsten/Aluminium (W/Al) and Tungsten/Rhodium (W/Rh) anode/filtration combinations at 28 kV). The image quality was measured in terms of Contrast-to-Noise Ratio (CNR) using a synthetic breast phantom (4 cm thick with 50% glandularity). The results can be used to optimize the imaging conditions in order to minimize patient's Mean Glandular Dose (MGD).

Combined reactor neutron beam and 60Co γ-ray radiation effects on CMOS APS image sensors

The combined reactor neutron beam and 60Co γ-ray radiation effects on complementary metal-oxide semiconductor (CMOS) active pixel sensors (APS) have been discussed and some new experimental phenomena are presented. The samples are manufactured in the standard 0.35-μm CMOS technology. Two samples were first exposed to 60Co γ-rays up to the total ionizing dose (TID) level of 200 krad(Si) at the dose rates of 50.0 and 0.2 rad(Si)/s, and then exposed to neutron fluence up to 1 × 1011 n/cm2 (1-MeV equivalent neutron fluence). One sample was first exposed to neutron fluence up to 1 × 1011 n/cm2 (1-MeV equivalent neutron fluence), and then exposed to 60Co γ-rays up to the TID level of 200 krad(Si) at the dose rate of 0.2 rad(Si)/s. The mean dark signal (KD), the dark signal non-uniformity (DSNU), and the noise (VN) versus the total dose and neutron fluence has been investigated. The degradation mechanisms of CMOS APS image sensors have been analyzed, especially for the interaction induced by neutron displacement damage and TID damage.

Synchrotron based planar imaging and digital tomosynthesis of breast and biopsy phantoms using a CMOS active pixel sensor

The SYRMEP (SYnchrotron Radiation for MEdical Physics) beamline at Elettra is performing the first mammography study on human patients using free-space propagation phase contrast imaging. The stricter spatial resolution requirements of this method currently force the use of conventional films or specialized computed radiography (CR) systems. This also prevents the implementation of three-dimensional (3D) approaches. This paper explores the use of an X-ray detector based on complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) technology as a possible alternative, for acquisitions both in planar and tomosynthesis geometry.Results indicate higher quality of the images acquired with the synchrotron set-up in both geometries. This improvement can be partly ascribed to the use of parallel, collimated and monochromatic synchrotron radiation (resulting in scatter rejection, no penumbra-induced blurring and optimized X-ray energy), and partly to phase contrast effects. Even though the pixel size of the used detector is still too large – and thus suboptimal – for free-space propagation phase contrast imaging, a degree of phase-induced edge enhancement can clearly be observed in the images.

CMOS ACTIVE PIXEL DESIGN USING 0.6 ?M IMAGE SENSOR TECHNOLOGY

This paper describes the Complementary Metal Oxide Semiconductor (CMOS) Active Pixel Sensor (APS) that has become a huge demand for imaging systems because of a better picture quality, low cost, low power consumption and lesser noise as compared with the features of charged coupled devices (CCDs). In this paper, we have designed a CMOS Photodiode APS in 0.6 μm technology that has a lower voltage and noise reduction capability for the pixel. Simulation results with PSPICE and schematic design are presented and discussed. The measured voltage swing at the output for the APS design is 0.47 V to 3.04 V for the supply voltage of 3.3 V and the calculated conversion gain is 5.24590 μV/e. The total capacitance has calculated by simulation result is 30.50 fF. Lastly, we concluded with a description of some applications and opportunities for the CMOS APS.

Research on dark signal degradation in 60Co γ-ray-irradiated CMOS active pixel sensor

A study of ionizing radiation effects is presented for CMOS active pixel sensors manufactured in a 0.5-μm CMOS (complementary metal oxide semiconductor)by n-well technology. The basic mechanisms that may cause failure are also presented. After exposure in γ-rays, the most sensitive parts to radiation-dark signals and dark signal non-uniformity are discussed, i.e. the physical mechanism of the degradation by irradiation. One can see from the experiment that the mean dark signals are dramatically increased with total dose for both operated and static devices. Static device seems more affected by irradiation than operated device. We find that most part of the total dark signal in a pixel comes from the depletion of the photodiode edge at the surface and the rest part is caused by the leakage of the source region of the reset transistor. Dark signal non-uniformity follows the dark current evolution with total dose. Further study of photodiode and LOCOS (local oxidation of silicon) isolation behaviors under irradiation should be done so as to correctly use this qualification techniques on MOS sensors manufactured in CMOS n-well technology process.

Irradiation Damage Tests on Backside-Illuminated CMOS APS Prototypes for the Extreme Ultraviolet Imager On-Board Solar Orbiter

Complementary metal oxide semiconductor (CMOS) active pixel sensor (APS) prototypes made using 0.18 μm technology process have been developed for the Extreme Ultraviolet Imager of the Solar Orbiter mission. Backside illuminated CMOS APS devices, i.e., 256 × 256 pixels area, 10 μm pixel pitch with different pixel designs have been fully characterized in the visible and in EUV wavelengths. A set of irradiation tests were carried out to investigate the degradation of the devices expected in the space environment conditions of Solar Orbiter. Total ionizing dose effects from grounded measurements are presented up to 150 krad[SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ]. The prototype sensors show the immunity to single-event latch up at linear energy transfer's of 67.7 MeV cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /mg but were observed to suffer from strong degradations after proton irradiation test (with a cumulated fluence up to 4×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> protons/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) and from single event functional interrupt.

Near-infrared fluorescence goggle system with complementary metal–oxide–semiconductor imaging sensor and see-through display

We have developed a near-infrared (NIR) fluorescence goggle system based on the complementary metal-oxide-semiconductor active pixel sensor imaging and see-through display technologies. The fluorescence goggle system is a compact wearable intraoperative fluorescence imaging and display system that can guide surgery in real time. The goggle is capable of detecting fluorescence of indocyanine green solution in the picomolar range. Aided by NIR quantum dots, we successfully used the fluorescence goggle to guide sentinel lymph node mapping in a rat model. We further demonstrated the feasibility of using the fluorescence goggle in guiding surgical resection of breast cancer metastases in the liver in conjunction with NIR fluorescent probes. These results illustrate the diverse potential use of the goggle system in surgical procedures.

A novel wafer-scale CMOS APS X-ray detector for breast cancer diagnosis using X-ray diffraction studies

The current study uses a novel large area (12.8 cm × 13.1 cm) complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) X-ray detector, named Dynamic range Adjustable for Medical Imaging Technology (DynAMITe), for breast cancer diagnosis. The detector consists of two geometrically superimposed grids: a) 2560 × 2624 fine-pitch grid of pixels (50 μm pitch), named Sub-Pixels (SP camera), for low intrinsic noise and high spatial resolution and b) 1280 × 1312 large-pitch grid of pixels (100 μm pitch), named Pixels (P camera), for high dynamic range. X-ray performance characterization measurements show that the detective quantum efficiency (DQE) of the SP camera is in the range 0.7–0.75 at low spatial frequencies using a tungsten (W) anode X-ray source at 28 kV. Hence, the detector is suitable for mammography. Furthermore, we used the SP camera to combine mammograms with angle dispersive X-ray diffraction (ADXRD) measurements in order to apply the X-ray biopsy concept in one examination. The results show that ADXRD technique indicates the presence of cancer in suspicious areas on the mammogram. Hence, it could be used to determine the region affected by cancer and assist in planning surgery. This study is the proof of concept that mammography and ADXRD can be combined in one examination.

Development of Highly Sensitive Ion Imager Corresponding to Real-Time Readout Having Single-Ion Detectability

We designed a new type of stacked complementary metal–oxide–semiconductor active pixel sensor (SCAPS) for charged particles with real-time readout and single-ion detection capabilities. Here we present the characteristics of a new imager, SCAPS-II, which implements a newly devised pixel structure of 504×504 pixels for high sensitivity and a noise-reduction mechanism with analog accumulation capabilities inside the column readout circuits. The sensitivity for ions was estimated to be 150 µV/ion under 10 keV Si+ ion irradiation, which is 5 times greater than that of conventional SCAPS. The noise floor was at the 3 ion level without the noise-reduction mechanism at a frame rate of 0.16 s/frame. The noise reduction mechanism reduced the noise to the 1.7 ion level at 0.3 s/frame with 13 samplings. A combination of the noise-reduction mechanism and a multiple-frame-averaging technique achieved a noise level of 0.3 ions. Single-ion detectability was demonstrated using a combination of the noise-reduction mechanism and the multiple-frame-averaging technique that reduced the noise to the 0.3 ion level with 13 samplings, employing an integration circuit and 50-frame averaging at 14.4 s/frame.

Design and image-quality performance of high resolution CMOS-based X-ray imaging detectors for digital mammography

In digital X-ray imaging systems, X-ray imaging detectors based on scintillating screens with electronic devices such as charge-coupled devices (CCDs), thin-film transistors (TFT), complementary metal oxide semiconductor (CMOS) flat panel imagers have been introduced for general radiography, dental, mammography and non-destructive testing (NDT) applications. Recently, a large-area CMOS active-pixel sensor (APS) in combination with scintillation films has been widely used in a variety of digital X-ray imaging applications. We employed a scintillator-based CMOS APS image sensor for high-resolution mammography. In this work, both powder-type Gd2O2S:Tb and a columnar structured CsI:Tl scintillation screens with various thicknesses were fabricated and used as materials to convert X-ray into visible light. These scintillating screens were directly coupled to a CMOS flat panel imager with a 25 × 50 mm2 active area and a 48 μm pixel pitch for high spatial resolution acquisition. We used a W/Al mammographic X-ray source with a 30 kVp energy condition. The imaging characterization of the X-ray detector was measured and analyzed in terms of linearity in incident X-ray dose, modulation transfer function (MTF), noise-power spectrum (NPS) and detective quantum efficiency (DQE).

Characterization study of an intensified complementary metal–oxide–semiconductor active pixel sensor

An intensified CMOS active pixel sensor (APS) has been constructed for operation in low-light-level applications: a high-gain, fast-light decay image intensifier has been coupled via a fiber optic stud to a prototype "VANILLA" APS, developed by the UK based MI3 consortium. The sensor is capable of high frame rates and sparse readout. This paper presents a study of the performance parameters of the intensified VANILLA APS system over a range of image intensifier gain levels when uniformly illuminated with 520 nm green light. Mean-variance analysis shows the APS saturating around 3050 Digital Units (DU), with the maximum variance increasing with increasing image intensifier gain. The system's quantum efficiency varies in an exponential manner from 260 at an intensifier gain of 7.45 × 10(3) to 1.6 at a gain of 3.93 × 10(1). The usable dynamic range of the system is 60 dB for intensifier gains below 1.8 × 10(3), dropping to around 40 dB at high gains. The conclusion is that the system shows suitability for the desired application.