Amplitude Monopulse Research Articles

Three-spatial-channel method for amplitude monopulse direction-finding of radar object

Three-spatial-channel method for amplitude monopulse direction-finding of radar object

The deception effect of FDA counteracting amplitude-comparison monopulse reconnaissance

Conventional phased array radar can direct the high-gain beam, resulting in high visibility under the reconnaissance system and even direct exposure to the enemy. As an amplitude-based direction-finding system, the amplitude monopulse system can recognize the traditional radar signals. However, there are still some issues with the countermeasures of the monopulse system, so it is necessary to find better styles of jamming. Since the beam of the frequency diverse array (FDA) signal at a certain angle varies with the range, we studied the deception effect of the FDA against the amplitude-comparison monopulse direction-finding system. By analyzing the established FDA-based direction-of-arrival location deception model against the amplitude-comparison monopulse system, we found that the introduction of the frequency increment might cause the FDA signals to deceit the monopulse system in principle. Then, to indicate the superiority of our deception method, we obtain the instantaneous signal-to-noise ratio, Cramér–Rao lower bound, root-means-square error, and variation. Numerical simulation results demonstrate that the FDA can generate deceptive signals to counteract the amplitude-comparison monopulse direction-finding system.

Design of a High-Power Gaussian Pulse Transmitter for Sensing and Imaging of Buried Objects

This paper aims to investigate a high-power and low-cost monopulse transmitter circuit for underground and underwater sensing and imaging. The transmitter utilizes two Marx transistor-based pulse generators, a balun, and a Vivaldi antenna. A simple output network, including an inductor and Schottky diode, is employed to compensate for the ringing level and distortion and improve the pulse width. The ringing level of the developed circuit is around 6 percent. The output is a Gaussian pulse with pulse width and amplitude of 481 ps and 50 V, respectively. In order to have a high amplitude monopulse, an exact replica of this network in parallel is exploited. The outputs of the parallel circuits are subtracted through the balun to have a dc-free monopulse with amplitude and pulse width of 26 V and 483 ps, respectively. The monopulse is radiated by a Vivaldi antenna toward a buried object. The image of the target is generated using the time-domain global back projection (TD-GBP) method. Three imaging experiments are conducted to verify the functionality of the designed sensor system. The reconstructed images and the reference images are shown high structural similarity indexes of 98.6%, 95.4%, and 97.6%.

Research on Monopulse Angle Measurement Algorithm in Pseudolite Local Positioning System

The pseudo-satellite local positioning system can solve the problem of blind spots in satellite navigation systems, such as tunnels, underground parking lots, and indoor positioning. The method of direction-finding positioning can be combined with distance-finding positioning to improve positioning accuracy, and it can also independently realize positioning functions. The basis of direction-finding positioning is to accurately estimate the direction of the signal source. The sum-difference patterns of amplitude monopulse angle measurement algorithm has mature applications in the field of tracking radar, and can achieve accurate angle estimation. The sum-difference patterns of amplitude monopulse angle measurement algorithm is applied to a pseudo-satellite local positioning system. Through simulation experiments, the angle measurement performance of the algorithm under different conditions is analyzed.

Monopulse angle estimation with MIMO radar

In this article a generalization of the amplitude monopulse method for angle estimation for radars with multiple input and multiple output (MIMO) elements is discussed. Bearing characteristics for sparse virtual antenna arrays are presented. A reconstructed image of the radiation source is presented for two cases of direction finding: based on calculation of the correlation integral and based on weighted sum of signals over the aperture of the virtual antenna array.

Hybrid Analog-Digital Processing System for Amplitude-Monopulse RSSI-Based MiMo WiFi Direction-of-Arrival Estimation

We present a cost-effective hybrid analog digital system to estimate the Direction of Arrival (DoA) of WiFi signals. The processing in the analog domain is based on simple well-known RADAR amplitude monopulse antenna techniques. Then, using the received signal strength indicator (RSSI) delivered by a commercial MiMo WiFi cards, the DoA is estimated using the so-called digital monopulse function. Due to the hybrid analog digital architecture, the digital processing is extremely simple, so that DoA estimation is performed without using IQ data from specific hardware. The simplicity and robustness of the proposed hybrid analog digital MiMo architecture is demonstrated for the ISM 2.45 GHz WiFi band. Also, the limitations with respect to multipath effects are studied in detail. As a proof of concept, an array of two MiMo WiFi DoA monopulse readers is distributed to localize the two-dimensional position of WiFi devices. This cost-effective hybrid solution can be applied to all WiFi standards and other Internet of Things narrowband radio protocols, such as Bluetooth Low Energy or Zigbee.

Method for Estimating the Number of Radiation Sources in the Problem of the Amplitude Monopulse Direction Finding

We propose an algorithm for processing the signals received by a multichannel amplitude monopulse direction-finding system, which allows one to estimate the radiation-source number in the operating region of space. The decision on the number of sources is made on the basis of the threshold method. The threshold value is determined using the criterion of minimum of the sum of the conditional error probability.

Research on Method of Monopulse Estimation Based on Variable Pulse Repetition Time Stepped-Frequency Waveform

Stepped-frequency signal is an important high distance resolution signal, but it is easy to be effected by target motion. When the target moves, the phenomenon of waveform broaden and range walk would appear if we process the echo of normal stepped-frequency signal directly, so we should compensate target velocity before angle measurement; in regard to variable pulse repetition time stepped-frequency signal, there is only range walk without waveform broaden if we process the echo directly, so we could conduct the amplitude and sum-difference monopulse estimation without velocity compensation, measuring efficiency could be improved. In this article, we analyzed the principle of variable PRT stepped-frequency signal, compare it with the normal stepped-frequency signal to prove its effectiveness. Then we verify the feasibility of angle measurement by using this method.

Application of the Total Least Square ESPRIT Method to Estimation of Angular Coordinates of Moving Objects

The TLS ESPRIT method is investigated in application to estimation of angular coordinates (angles of arrival) of two moving objects at the presence of an external, relatively strong uncorrelated signal. As a radar antenna system, the 32-element uniform linear array (ULA) is used. Various computer simulations have been carried out in order to demonstrate good accuracy and high spatial resolution of the TLS ESPRIT method in the scenario outlined above. It is also shown that accuracy and angle resolution can be significantly increased by using the proposed preprocessing (beamforming). The most of simulation results, presented in a graphical form, have been compared to the corresponding equivalent results obtained by using the ESPRIT method and conventional amplitude monopulse method aided by the coherent Doppler filtration.

Switched Directional/Omnidirectional Antenna Module for Amplitude Monopulse Systems

An L-band switched directional/omnidirectional antenna module, consisting of a four-monopole antenna, a switched beamforming network (SBFN), a matching network, and an interface, is described. The antenna includes four folded monopoles, parasitic elements, a special base plate, a common capacitive top hat, and a radome. The special switched-line 0°/180° phase shifter of the switched beamforming network provides switching between the directional and the omnidirectional modes. The beamforming network (BFN) includes four 90° hybrids, connected with each other through four invertors. A practical application of this antenna module for aircraft amplitude monopulse systems is considered in this article. Over a frequency range of 10%, the experimental antenna module exhibited directional gain greater than +10 dBi, from 90° to 100° beamwidth, a return loss less than -13.0 dB, side/back lobe levels than -10.0 dB, and an rms bearing error of less than 2°.

Phase and amplitude monopulse techniques to increase the accuracy of within-beam bearing estimates of volume scatterers.

Traditionally, designers of multibeam sonars have limited the accuracy of echo angle-of-arrival (bearing) estimates by mapping each measured echo to its beam’s maximum response axis. Although this bearing accuracy can be improved for large targets, e.g., the ocean floor, by applying filtering techniques to the time series of bearing estimates, the echoes from water column scatterers are often only a few time samples in duration. Therefore, it is beneficial to both increase the quantity and improve the accuracy of these few echo bearing estimates. Phase and amplitude monopulse techniques use linear mappings between the sine of the echo bearing and (1) the differential signal phase and (2) the natural logarithm of the ratio of the signal magnitudes, respectively, of neighboring beams to provide within-beam echo bearing estimates. Using either of these techniques, the accuracy of the bearing estimates of the echo’s acoustic center is improved compared to maximum-response-axis mapping. By using both techniques simultaneously, the effective number of echo bearing estimates is doubled. These techniques are applicable to both planar and cylindrical multibeam sonar systems.

Use of within-beam mapping in conjunction with Kalman filtering to improve angle of arrival estimation accuracy in multibeam echo-sounding.

The positions of both water column scatterers and the ocean floor can be estimated using data from multibeam sonars. In a previous presentation [D. S. Brogan and C. P. de Moustier, J. Acoust. Soc. Am. 119, 3352 (2006)] it was shown that a Kalman filter could be used to track echo angles of arrival (bearings) versus time for such targets using quadrature‐sampled multibeam sonar data. In that research, the inputs to the Kalman filter were the echo magnitude time series of each beam placed on that beam’s maximum response axis. While the results using this approach proved to be superior to those of a conventional split‐aperture processor, the bearing accuracy can be further improved by applying a pre‐processing stage that maps each echo to its acoustic center rather than to its beam’s maximum response axis. This mapping is accomplished using phase and/or amplitude monopulse techniques that provide linear mappings between the sine of the echo bearing and (1) the differential signal phase and (2) the natural logarithm of the ratio of the signal magnitudes, respectively, of neighboring beams to provide within‐beam echo bearing estimates. Results are compared both with and without the pre‐processing stage.

A 24 GHz Amplitude Monopulse Comparator in 0.13 $\mu$m CMOS

This letter presents the design and implementation of a wideband 24 GHz amplitude monopulse comparator in 0.13 mum CMOS technology. The circuit results in 9.6 dB gain in the sum channel at 24 GHz with a 3-dB bandwidth of 23.0-25.2 GHz, and a sum/difference ratio of > 25 dB at 20-26 GHz. The measured input PI dB is -14.4 dBm at 24 GHz. The chip is only 0.55 times 0.50 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (without pads) and consumes 44 mA from a 1.5 V supply, including the input active baluns and the differential to single-ended output stages (28 mA without the input and output stages). To our knowledge, this is the first demonstration of a high performance mm-wave CMOS monopulse comparator RFIC.

Comparative analysis of a phase and an amplitude processor for amplitude monopulse systems

The theoretical performance of an amplitude monopulse processor is compared with that of a phase monopulse processor in the presence of thermal noise. Both processors use the sum and difference beam antenna model. Both processors exhibit a bias error at signal-to-noise ratios below 20 dB. The phase processor demonstrates a smaller standard deviation in the angle estimate for target angles in the vicinity of the monopulse boresight.

Performance Analysis of Pulse Doppler Digital Radars with Application to the Shuttle Ku-Band System

The performance of a class of pulse Doppler radars with a digitally implemented signal processing unit is investigated. The Ku band rendezvous radar onboard the Shuttle Orbiter is a pulse Doppler radar which is in this class. The detection capability is first presented. A unified analysis of digital radar tracking loops is presented which employs logarithmic discriminants. The results are applied to angle, range, and range rate tracking loops. Numerical results of the amplitude monopulse angle tracking loop are presented for the Ku -band rendezvous radar of the Space Shuttle.

On the Passive Resolution of Broadcasting Targets with a Monopulse Antenna

This paper indicates a basic constraint on angular resolution of targets using monopulse measurements. The specific case at hand is the angular resolution of several broadcasting targets by a passive, standard, four-horn amplitude monopulse system. It is shown that when all broadcasting targets emit spectrally equivalent wide-sense stationary signals and the antenna and target geometry are fixed, the signals presented to the radar signal processor are equivalent to those of a canonical complex of threee broadcasting targets, one at an arbitrary angle θT, one at a null of the sum channel pattern, and one at a null of the difference channel pattern. In the case of broadband flat spectral transmission, two of the three targets in the canonical complex cannot be distinguished from receiver noise. A simple method for determining the angle (or angles) at which a monopulse antenna will attempt to track a broadcasting target complex is presented. Generalizations of this theory to active and/or more complicated monopulse systems are possible.

On the Optimum Squint Angles of Amplitude Monopulse Radar and Beacon Tracking Systems

The different quantitative criteria (and numerical results) for analytically determining the optimum squint angle of an amplitude monopulse system in the track mode are compared and reconciled, and the results are generalized to include mutual coupling.

Comments on "Angular accuracy of amplitude monopulse off-boresight radar"

Comments on "Angular accuracy of amplitude monopulse off-boresight radar"

Comment on "Variance Analysis of the Angle Output Voltage for an Amplitude Monopulse Receiver"

The above paper contains a misleading calculation of the mean of the output of a logarithmic detector whose input is a sine wave plus Gaussian noise. In this correspondence the nature of the inaccuracy is described, an exact expression for the mean is derived, and asymptotic expressions for the cases of low signal-to-noise and high signal-to-noise are obtained and compared to the previous result.

Monopulse Antenna Performance When Receiving Nonuniform Waves

Variations in apparent target direction, or glint, as sensed by an amplitude monopulse tracking antenna are analyzed for several cases when a nonuniform wave is incident on the antenna. Results are given for a target consisting of two isotropic scatterers, and compared with results previously obtained for the case of a locally uniform wave incident on the antenna.