Abstract: The present disclosure is concerned with a method for searching a search area, a missile, and a missile formation. According to the method, in each case at least one radar is arranged in at least two missiles, wherein the method involves: determining a total search time for searching the search area, splitting the search area into at least two search subareas, and searching the at least two search subareas by means of the respective radar of the at least two missiles. The at least two missiles carry out the searching cooperatively, wherein the search subareas are chosen such that a detection probability is maximized.

Abstract: The present invention realizes stable operation of a radar device even if there is radio wave interference between multiple radar devices. A radar device 108 is provided with the following: an oscillator 105 that generates a modulated signal that has undergone frequency modulation; a transmission unit 103 that emits a transmission signal that has undergone frequency modulation during a prescribed modulation operation period using the modulated signal generated by the oscillator 105; a reception unit 104 that receives a reception signal which is the transmission signal that has been reflected off of an object in the area; and a signal processing unit 106.

Abstract: A method of mitigates RF interference from an RF interferer. An RF signal is received at an RF transceiver during a time period. The RF signal that includes, for at least a portion of the time period, an interference signal having a cyclic transmission pattern with at least one deterministic feature. The received RF signal is analyzed in order to determine timing information for the at least one deterministic feature and the associated interference signal cyclic transmission pattern. Transmission of the RF signals from the RF transceiver are synchronized with the interference signal transmission pattern based on the determined timing information to mitigate interference between the RF signals and the interference signal.

Abstract: An antenna system for providing identification functionality comprising a main antenna and an auxiliary antenna, wherein the antennas are configured to at least transmit electromagnetic waves. The antenna system comprises a first channel interface and a second channel interface, a first switch and a transmission input means. The first switch is configured to switch between a first operation mode and a second operation mode. When set in the first operation mode the second channel interface is set to be in connection with the auxiliary antenna and when set in the second operation mode the second channel interface is set to be in connection with the main antenna. If transmission via the first transmission channel is expected the transmission input means is configured to set the first switch in the first operation mode.

Abstract: An apparatus for creating vibrations in a pipe string is disclosed. The device comprises a fluid pump which pumps fluid within a first fluid bore and is connected to the pipe string. A hydraulic pump pumps fluid within a second fluid bore and a movable plunger disposed between the first fluid bore and the second fluid bore intermittently opens and closes access to a tank based on changes to a pressure of the fluid pump. The tank for collecting at least a portion of the fluid is connected to the apparatus via the first fluid bore, and the movement of the plunger is configured to generate vibrations within the pipe string by altering the amount of fluid allowed to flow to the tank.

Abstract: Mud pulse telemetry. The various embodiments are directed to methods and systems of encoding data in a mud pulse telemetry system, where at least a portion of the data is encoded the time between pressure transitions. Moreover, the various embodiments are directed to detection methods and systems that detect the pressure transitions at the surface.

Abstract: The invention relates to a method for detecting a distance between a radar system and a reflecting surface. The method comprises the steps of transmitting a frequency modulated continuous wave (FMCW) radar signal from the radar system and receiving a reflected FMCW radar signal being the transmitted signal that has been reflected by the reflecting surface. Further, the method comprises the steps of providing a beat signal having a frequency that is equal to the frequency difference between the transmitted signal and the received signal and determining harmonics of the beat signal. The method also comprises the step of using phase shift information of at least one of said harmonics for determining a distance between the radar system and the reflecting surface.

Abstract: A method and arrangement for mud telemetry having components of a wellbore casing, a combination rotor stator positioned inside the wellbore casing, an uphole detection arrangement configured to sense increases and decreases in pressure, a valve actuator, a valve configured to be actuated by the valve actuator, the valve configured to convey a fluid from an inside of the wellbore casing to an outside of the wellbore casing and cause a decrease in fluid pressure in the wellbore casing, and a downhole tool configured to measure at least one formation parameter.

Abstract: A system for producing an output signal representing movement of an object's surface has a continuous wave (CW) signal source for producing an CW signal directed at the object's surface. The CW signal is produced at a first frequency. A receiving element receives a signal reflected from the object's surface when the CW signal hits this surface. A down-converting frequency mixer converts the received signal into a signal of a second frequency lower than the first frequency. The frequency mixer is configured to produce an output signal representing an amplitude-modulated (AM) component of the received signal and having a parameter representing movement of the object's surface.

Abstract: According to one embodiment of the present invention, determining the location of a target of interest includes determining a beacon location of the beacon. The beacon location is transmitted to a sensor. The sensor is operable to determine a sensor location of the sensor. The sensor is further operable to determine a target location of the target according to the beacon location and the sensor location. The target location is distinct from the beacon location.

Abstract: In an example method, a vehicle is configured with a radar system used to aid in vehicle guidance. The method could include an array of antennas plurality of antennas configured to receive a radar signal. The array of antennas has a respective spacing between the given antenna and an adjacent antenna; however, the plurality of spacings includes at least two different spacings. A portion of the method may be performed by a processor configured to calculate a detection channel, based on a difference between differential phases associated with two antenna pairs in the array. The processor may also calculate an unambiguous angle based on the detection channel and the plurality of antenna spacings. Additionally, the processor may control the radar unit based on the calculated unambiguous angle.

Abstract: A radar system includes an antenna. The radar system comprises a processor for providing an error in ground speed estimate based upon Doppler velocity data, and a transmitter. The frequency of radar signals from the transmitter is adjusted according to a velocity of the aircraft calculated using the error in ground speed estimate or using the error in ground speed estimate. The adjusted frequency can allow ground clutter to be removed by high pass filtering in one embodiment.

Abstract: Provided are a method and apparatus (receiver) of receiving and processing a radio signal in a transmitter-receiver environment. The radio signals are transmitted across a wireless interface using Ultra Wideband (UWB) pulses. A transmitted reference approach is utilized. The radio signal include pairs of UWB pulses with each pair of pulses separated by a fixed time delay. The two pulses are then combined to provide for improved noise immunity.

Abstract: A DDS based system, such as a radar, includes means for generating a plurality of transmission signals using a DDS, and means for integrating signals derived therefrom, such as received signals. The system further includes means for varying the relative starting phase of the plurality of transmission signals, or adjusting the DDS input clock while maintaining similar primary output frequency characteristics of the transmission signals. The approach has the effect of changing the location of unwanted frequency spurs in each of the transmission signals, and hence the effects of these are decreased in the integration process. An improvement in the sensitivity of the system results. Although primarily suited to radar applications the invention may find utility in other systems such as sonar or lidar systems.

Abstract: The invention includes a method for transmitting and detecting high speed Ultra Wideband pulses across a wireless interface. The transmitter includes a serializer and pulse generator. The receiver comprises a fixed delay line, multiplier, local serializer (with a sequence matching the transmitter), digital delay lines, low noise amplifier and logic fan-out buffer along with an array of D flip-flop pairs. Each flip-flop pair is enabled, at fixed time increments, to detect signals at a precise time; the timing is controlled by the pseudo-random sequence generated by the local serializer. A local tunable oscillator is controlled by detecting the phase change of the incoming signal and applying compensation to maintain the phase alignment and clock synchronization of the receiver to the clock reference of the transmitter. The invention uses a pair of pulses with a fixed delay and then relies on mixing the two to provide better noise immunity.

Abstract: Provided is a radar apparatus including an envelope detector unit that acquires an envelope component of a signal transmitted from a receiving antenna in at least one combination of a plurality of combinations of transmitting antennas and receiving antennas whose spatial phases become equal to each other in the array antenna; a determination unit that determines an amount of compensation in the at least one combination based on the envelope component acquired by the envelope detector unit; and a compensator unit that compensates a phase of a signal transmitted from each of the receiving antennas before aperture synthesis by using the amount of compensation determined by the determination unit, or compensates a phase of a signal radiated from the transmitting antenna in another combination.

Abstract: A homodyne motion sensor or detector based on ultra-wideband radar utilizes the entire received waveform through implementation of a voltage boosting receiver. The receiver includes a receiver input and a receiver output. A first diode is connected to the receiver output. A first charge storage capacitor is connected from between the first diode and the receiver output to ground. A second charge storage capacitor is connected between the receiver input and the first diode. A second diode is connected from between the second charge storage capacitor and the first diode to ground. The dual diode receiver performs voltage boosting of a RF signal received at the receiver input, thereby enhancing receiver sensitivity.

Abstract: Provided are transmitter topology, receiver topology and methods for generating and transmitting a radio signal at a transmitter and detecting and processing a radio signal at a receiver. The radio signals are transmitted across a wireless interface using Ultra Wideband (UWB) pulses. A transmitted reference approach is utilized. The radio signal include pairs of UWB pulses with each pair of pulses separated by a fixed time delay. The two pulses are then combined to provide for improved noise immunity.

Abstract: A method and system are described whereby a magnetron-based radar transmission signal is accurately measured, allowing for measurement of absolute phase change returns from fixed clutter targets caused by changes in the refractive index of the transmission medium.

Abstract: A true time delay beamforming system and calibration method for transmission and reception of a beam is disclosed. The true time delay beamforming system comprises at least one input signal received by at least one signal conditioning device, wherein the signal conditioning device is adapted to provide selective, independent, and variable control of one of a phase delay, a time delay and an amplitude of the input signal to produce an output signal. A control logic device is adapted to provide a control logic signal to the at least one signal conditioning device for selectively activating and controlling the signal conditioning device. The true time delay beamforming system may further include an automatic calibration system that generates an error correction signal based on errors detected in the output signal, and selectively adjusts the control logic signal based thereon.

Abstract: This disclosure provides a device, which includes a transceiver for outputting a reception signal according to an echo intensity of a transmission signal, a reception signal monitoring module for monitoring an intensity of the reception signal based on a saturation condition, and a transmitting condition setting module for controlling a transmitting power according to the intensity of the reception signal monitored by the reception signal monitoring module.

Abstract: The invention relates to a direct-current blocking circuit, and a hybrid circuit device, a transmitter, a receiver, a transmitter-receiver and a radar device that have the direct-current blocking circuit. A dielectric substrate (2) is provided with a conductor layer (3) disposed parallel with the dielectric substrate (2), first and second planar lines (4, 5) each containing a part of the conductor layer (3), and a waveguide (6) containing a part of the conductor layer (3). The first and second planar lines (4, 5) are located on one surface (2a) side of the dielectric substrate (2) with respect to the conductor layer (3), and the waveguide (6) is located on another surface (2b) side of the dielectric substrate (2). In a transmission direction (X) of electric signals, as to the waveguide (6), its one end overlaps with one end of the first planar line (4), and its another end overlaps with one end of the second planar line (5).

Abstract: For use in conjunction with a microwave antenna having a radiator array configured to scan in a horizontal direction, a method for scanning in the vertical direction. A first FMCW microwave signal having a first bandwidth is transmitted at a first microwave frequency and the echo, if any, is received by the radiator array. A second FMCW microwave signal having a second bandwidth is also transmitted at a different center frequency and the echo, if any, is received by the radiator array. The different frequencies cause an elevational shift in the received signal. The receipt of the echoes is then processed to identify the location or locations of the object or objects causing the echo and communicating such location or locations to a user.

Abstract: For use in conjunction with a microwave antenna having a radiator array configured to scan in a horizontal direction, a method for scanning in the vertical direction. A first FMCW microwave signal having a first bandwidth is transmitted at a first microwave frequency and the echo, if any, is received by the radiator array. A second FMCW microwave signal having a second bandwidth is also transmitted at a different center frequency and the echo, if any, is received by the radiator array. The different frequencies cause an elevational shift in the received signal. The receipt of the echoes is then processed to identify the location or locations of the object or objects causing the echo and communicating such location or locations to a user.

Abstract: A weather radar includes an antenna unit of an active phased array system in which a plurality of antenna elements configured to transmit a radar pulse and receive a reflected pulse are arranged in a vertical direction, a transmission beam formation unit configured to divide an observation range in the elevation angle direction into a plurality of observation elevation angles, subdivide each observation elevation angle into a plurality of regions, assign a set of a plurality of regions not adjacent to each other to a pulse repetition interval (PRI), and form a fan-shaped transmission beam in the elevation angle direction for each of the regions in the set, and a reception beam formation unit configured to form a plurality pencil-shaped reception beams for each of the plurality of regions.

Abstract: In a CW radar system for detecting motion behind a wall involving modulation of the radar transmission, means are provided to interrupt the CW wave when motion is detected and to use the same radar transmitter to transmit a serial digital message to a remote monitoring receiver. The encoding can include a receiver wakeup message to turn on the receiver only when motion has been detected. In one embodiment, a microprocessor is used to detect when motion exists behind a wall and to provide a tailorable message to modulate the radar's transmitter in the period when the CW signal from the radar is turned off after motion detection.

Abstract: A charge pump includes: a control input for applying a control pulse, a pulsed current source for generating a current pulse in accordance with the control pulse, a direct current source for generating a direct current, and a current output that is connected to the pulsed current source and to the direct current source.

Abstract: A system and method for adaptation of a radar receiver in response to frequency drift in a transmission source is disclosed that utilizes a stable local oscillator established at a single, non-fluctuating frequency and compensates for transmission frequency fluctuation in the signal processor module. The disclosed system and method use mathematical processing techniques to compensate for variations in transmitter frequency during baseband processing of radar reflectivity signals. The system estimates the frequency of the transmitter to a high degree of accuracy and mathematically converts the reflectivity signal energy to a baseband intermediate frequency which is adjusted to compensate for fluctuations in transmitter frequency. A digital down converter circuit and numerically controlled oscillator circuit are also utilized to convert reflectivity signal energy to baseband and compensate for transmitter frequency drift.

Abstract: A radar apparatus has a plurality of receiving antennas and an array transmitting antenna controlled to successively vary the direction of a transmitted beam within a range which includes a target detection range of directions. The direction of any target within the target detection range is detected based on a phase difference between incident reflected waves of adjacent receiving antennas. To eliminate false targets resulting from aliasing, each detected target is authenticated based upon closeness of its detected direction to the current transmitted beam direction. The receiving antennas and transmitting antenna are configured to exclude directions of grating lobes of the transmitted beam from the detection range, and thereby suppress effects of received reflected waves that originate from grating lobes.

Abstract: An all-digital line-of-sight (LOS) process architecture addresses the size, weight, power and performance constraints of a receiver for use in semi-active or active pulsed electromagnetic (EM) targeting systems. The all-digital architecture provides a platform for enhanced techniques for sensitive pulse detection over a wide field-of-view, adaptive pulse detection, LOS processing and counter measures.

Abstract: An all-digital line-of-sight (LOS) process architecture addresses the size, weight, power and performance constraints of a receiver for use in semi-active or active pulsed electromagnetic (EM) targeting systems. The all-digital architecture provides a platform for enhanced techniques for sensitive pulse detection over a wide field-of-view, adaptive pulse detection, LOS processing and counter measures.

Abstract: A phased array radar system comprising a plurality of radiating elements configured in a common array aperture for detecting and tracking targets; and a transmit and receive arrangement responsive to a first control signal for configuring the plurality of radiating elements to define a plurality of sub-apertures from the common array aperture for detecting and tracking short range targets, wherein the plurality of sub-apertures are independently steerable array apertures and include an amplitude taper applied across each of the plurality of sub-apertures to reduce a peak sidelobe level.

Abstract: Provide an on-vehicle radar device that performs transmission control of a monitoring signal, following fixed rules, so that interference with other radar devices can be avoided with certainty. An on-vehicle radar device comprises a transceiver which transmits/receives a monitoring signal at a specified frequency band and transmits a priority order signal at a frequency within the above-mentioned frequency band, and a controller which switches the signals transmitted by the transceiver. The transceiver receives a priority order signal of another radar device, and when interference with the signal of the other radar device is detected, the controller, based on the priority order of that other device and on the priority order of the device itself, shifts, by a specified frequency amount, the frequency band of the monitoring signal transmitted by the transceiver.

Abstract: A circuit for a radar level gauge for measuring the level of the surface of a product stored in a container, wherein the gauge includes a radar for transmitting microwave signals from a multiband antenna unit towards the surface for receiving microwave signals reflected by the surface and for determining the level based on an evaluation of the time lapsed between the received and the transmitted signals and said radar operating on at least two different frequency bands. The circuit includes: a first microwave provision means for providing a microwave signal of a first frequency band having a first center frequency, a second microwave provision means for providing a microwave signal of a second frequency band having a second center frequency. The ratio between the second and the first center frequency is quantified as at least greater than 1.5:1 and preferably greater than 2:1.

Abstract: The search/detection apparatus modulates a carrier signal by a modulation signal, generates a probe signal for detecting the location of a target, and receives the probe signal reflected by the target as an echo signal. Then, the search/detection apparatus detects the existence of an interference signal other than the echo signal from the received signal and modifies the parameter of the modulation signal and/or carrier signal.

Abstract: A feedback loop corrects timing errors by reducing deviations from a constant radar sweep rate. Errors are detected and fed back to a phase corrector in a high gain feedback system. A precision radar rangefinder can be implemented with a direct digital synthesizer (DDS) that includes feedback error correction for reducing range errors by, for example, 100 times, or to 0.1 mm. An error-corrected DDS swept timing system can enable a new generation of highly flexible, repeatable and accurate radar, laser and guided wave rangefinders.

Abstract: A phased array radar system comprising a plurality of radiating elements configured in a common array aperture for detecting and tracking targets; and a transmit and receive arrangement responsive to a first control signal for configuring the plurality of radiating elements to define a plurality of sub-apertures from the common array aperture for detecting and tracking short range targets, wherein the plurality of sub-apertures are independently steerable array apertures.

Abstract: A microwave imaging system captures a microwave image of a target and minimizes noise in the microwave image using phase differentiation. A reflector antenna array is provided including a plurality of antenna elements for reflecting microwave radiation towards the target and for reflecting microwave radiation reflected from the target towards a microwave receiver. A processor programs the antenna elements with respective first phase shifts to capture a first microwave image of the target, and programs the antenna elements with respective second phase shifts to capture a second microwave image of the target. The first phase shift of each antenna element is 180 degrees different than the second phase shift for that antenna element. The processor minimizes noise from a combination of the first microwave image and the second microwave image.

Abstract: A method for transmitting a signal waveform from a transmitter within an adaptive broadcast radar system. In one embodiment, wherein the transmitter comprises at least one sub-aperture, the method includes: generating the signal waveform at the at least one sub-aperture; coding the signal waveform at the at least one sub-aperture, wherein the signal waveform is coded with transmitter data; phase shifting the signal waveform at the at least one sub-aperture; and, transmitting the coded signal waveform from an array element coupled to the sub-aperture according to the phase shifting.

Abstract: A signal transformation apparatus capable of performing stable transformation of a signal using a Mechanical switch includes a signal generator which generates a reserve pulse signal in response to an applied sync signal, a signal controller which outputs control signals to change and transform the reserve pulse signal to pulse signals having a predetermined pulse width, and a signal modulator which transforms the reserve pulse signal to the pulse signals having different pulse widths in response to the control signals. The signal modulator includes a switch bank in which a plurality of mechanical switches are connected in parallel, and a transmission line between nodes where the mechanical switches are formed.

Abstract: The present invention is related a method and system for irradiating a target location or material with high-amplitude narrow pulses of electromagnetic (EM) energy at a periodic or quasi-periodic rate. The method and system comprises generating at least three electromagnetic signals simultaneously in space from at least three sources, each signal having the same repetition rate and a different frequency, and directing each signal to at least one predetermined target, and adjusting the phase of each signal, so that its peak field occurs at the same instant as the occurrence of the peak fields of all the signals at the target.

Abstract: In a radio wave radar system using a two-frequency CW modulation method, it is possible to detect a distance between a host vehicle and a forward vehicle and to realize a stable ACC following travel, even in a condition in which the relative speed is 0. By combining the two-frequency CW modulation method with the frequency pulse CW modulation method, that is, by using combination with the two-frequency CW method when the relative speed occurs and the frequency pulse CW method when the relative speed is close to 0, even if the relative speed is 0, the IF signal obtained from the reflected wave from the forward vehicle can be generated to detect the existence of the ACC target vehicle, so that it is possible to realize a stable ACC following travel.

Abstract: The present invention relates to a radar measuring device which, with a simple design, ensures reliable distance determination even when a mixed signal is zero, and a method for operating a radar measuring device. The radar measuring device includes: A high-frequency oscillator (11) which emits two different carrier frequency signals (F1, F2), A first switching device (14) for switching the carrier frequency signals (F1, F2) as a function of first pulse signals (P1) and emitting radar pulse signals (T1, 2), A transmission antenna (16) and a receiving antenna (18), A second switching device (24) for switching the carrier frequency signals as a function of a delayed second pulse signal (P2) and emitting delayed radar pulse signals (S1, 2), A mixing device (21) for mixing received radar signals (R1, 2) with the delayed radar pulse signals (S1, 2) and emitting mixed signals (M1, 2).

Abstract: A digital polarimeteric system employs a signal time stretching technique and digital signal processing of the time-stretched signal to accurately measure the polarization of a received RF signal with commercially available digital hardware. A superheterodyne receiver down converts received RF signal components to IF, and analog-to-digital converters sample the signal components at much lower sampling rates than would normally be required to accurately measure the signal polarization. Each signal sample is “time stretched” by storing each sample in M locations in a memory, such that N samples occupy M×N memory locations. A digital signal processor applies incremental phase shifts to the digital samples until a phase-shifted combination of the digital samples yields a minimum null output. The phase shifts producing the minimum null identify the polarization of the received signal.

Abstract: A radar based sensor detection system comprises a microwave source operative to provide a continuous wave signal at an output. A pulse-former is coupled to the output of the source and is operative to provide at an output a variable length pulse that increases the transmitted energy of the radar system according to the range of object detection. A modulator is coupled to the output of the pulse-former for providing a modulated pulse signal when required. A transmit/receive switch coupled to the output of the modulator is selectively operative between a first transmit position and a second receive position. A transmit channel coupled to the transmit/receive switch transmits the pulse signal when the switch is operated in the transmit position. A receiving channel coupled to the transmit/receive switch receives the modulator signal when the switch is operated in the receive position.

Abstract: This invention relates to a frequency modulation of continuous wave (“FMCW”) radar altimeter capable of controlled linear sweep modes. The FMCW radar altimeter is characterized by the following functions: (1) adopts sweep up frequency and sweep down frequency to solve problems of distance and doppler signal mixture; (2) injects a random generated variable time delay in between sweep intervals to overcome interferences among different altimeters; and (3) switches different sweep frequency bands in accordance with different altitudes.

Abstract: Embodiments of the present invention are directed to a method and apparatus for substituting temperature sensor data for a satellite signal in a GPS receiver. In one embodiment of the present invention, a mathematical model of a GPS receiver's clock's response to temperature change is maintained. In one embodiment, the mathematical model is a third order polynomial. In one embodiment, when a GPS receiver has contact with at least four GPS satellites, the receiver collects data on changes in temperature and resulting changes in the GPS receiver's clock frequency. The data is incorporated into the GPS receiver's mathematical model. In one embodiment, the data is incorporated by modifying one or more coefficients in the mathematical model. In one embodiment, if a GPS receiver only has contact with three GPS satellites, changes in temperature and the mathematical model are used to estimate an adjustment to the signal generated by the clock.

Abstract: A radar device is described having means (12) for generating a first code, means (18) for modulating a transmission signal in a transmitting branch using the first code, means (32) for delaying the first code, means (20) for modulating a signal in a receiving branch using the delayed first code, and means for mixing a reference signal with a reception signal, multiple receiving channels (111, 112, . . . 11k) being provided, the receiving channels (111, 112, . . . 11k) having means (1201, 1202, . . . 120k) for generating additional codes (C1, C2, . . . Ck), the receiving channels (111, 112, . . . 11k) having means (131, 132, . . . 13k) for demodulating using the respective additional codes (C1, C2, . . . Ck), and means (15) being provided for modulating the transmission signal using at least one of the additional codes (C1, C2, . . . Ck). A method which may be implemented advantageously using the radar device described is also described.

Abstract: A radar system achieves adjustment of a time-change characteristic of a frequency-modulating voltage signal to a voltage-controlled oscillator for determining a transmitting signal such that the time-change characteristic of the frequency-modulating voltage signal is changed by a minute amount and the frequency spectrum of a beat signal is determined. The adjustment is performed so that the shape of a bulge in signal intensity included in the frequency spectrum is the sharpest.

Abstract: An HF radar system comprises a transmitting system, a receiving system, a signal processing system and a frequency management/ionospheric sounding system. The transmitting system comprises a transmitting antenna array configured to transmit a beam in a near vertical direction and a transmitting device arranged to drive the transmitting antenna array at frequencies suitable for downward refraction by the ionosphere. The receiving system comprises a receiving antenna array configured to receive returning signals from a target area returning to the receiving antenna array via refraction at the ionosphere. The signal processing system comprises a digital data processing system. The frequency management/sounding system comprises cooperating transmitting and receiving systems sending H-F signals to the ionosphere and analysing the returning signals. Alternatively, the system may have a duplexed antenna array.