JPH01500218A - Radiometric imager with frequency dispersive linear array antenna - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] frequency dispersive linear array antenna radiometric imager with [Background of the invention] The present invention relates generally to radiometric imagers, and particularly to line source or linear array antennas. Defining the frequency spectrum of a 2D scene using beam and fan beam inversion It concerns radiometric imagers.

High resolution radiometric imagers are used in aviation, meteorology, oceanography and astronomy. It has various practical applications in academic fields. Radiometers are especially useful on land. Surveying, atmospheric and oceanic features, water vapor, rainfall and sea surface temperature measurements, and cloudiness It is also very suitable for evaluating water level phenomena and water surface conditions under rain.

The scene is created using a source antenna that scans the scene with a series of multiple fan beams. A conventional microwave radiometer that provides two-dimensional images of U.S. Patent No. 607,869 filed on May 7, 2016 owaveRadioa+eter Using Fanbeam Inver s1on'). This document is called “S pinrad” (S p Radlometer). of that statement One embodiment shown therein includes a mechanically scanned pillbox antenna; However, other embodiments include electronically scanned and rotatable linear array antennas. ing. In both cases the antenna signal is properly processed and reconstruct the radiometric image of the signal.

Applications of radiometric imaging often require the use of scanned scenes. We need to know the frequency spectrum of each segment. In the past this has been A source antenna whose beam direction does not change over the required frequency range, i.e., a non-frequency Achieved by using dispersive antenna wires. bandpass filter band The link divides the antenna output signal into multiple separate frequency bins and then A video of a recorded scene is generated using data contained in various frequency bins. will be accomplished. Rotmann lens or planar reflector (i.e. pillbox) The large number of sources used in systems such as ) are structurally complex. vinegar Other source antennas, such as dangling wave arrays, use lenses and reflectors. Although it is small and lightweight compared to the data processor, its bandwidth is inadequately limited.

Therefore, it is possible to provide a spectral image of the scene over a wide frequency range and A radiometric instrument that is not unnecessarily large, complex, or unduly bandwidth-limited. It is thought that Mejia is necessary. The present invention satisfies this requirement. .

[Summary of the invention] This invention describes the use of a lightweight, frequency-dispersive linear array antenna to image secondary A radiometric image that determines the frequency spectrum of each segment of the original scene. and related methods. The antenna can be used over a predetermined frequency range. in response to radiation received along multiple conical fan beams representing individual frequencies of provides the output signal. These fan beams consist of multiple spaced conical sections. intersects the scanned scene in the area. Those with predetermined conical fan beams substantially perpendicular to the antenna axis and parallel to the scene, so that the A locking means is included for controllably rocking the antenna about a rocking axis.

The antenna output signal captures all segments of the scene in a predetermined frequency range. Contains data indicating the reception of all radiation from. This data is stored in It is accumulated in stages. According to the present invention, the radiometric imager In order to control the movement of the antenna by another method to resolve the ambiguity in the data, have supplementary means of transportation for The data processing means then segment the scene of interest. Process the accumulated data to determine the frequency spectrum of the target.

In one embodiment, the supplementary movement means moves the antenna substantially relative to the antenna axis and the swing axis. and means for controlling rotation about both vertical axes. Therefore, lock The king means and the rotation means are configured such that each cone area is rotated multiple times through each segment of the scene. work together to intersect with the target. The rotation means are each for increasing sway Preferably, the antenna is rotated through substantially 360 degrees relative to its position.

In other embodiments of the invention, the radiometric imager includes substantially the first It has a second frequency dispersive linear array antenna that is the same as the antenna. two antennas Na forms an interferometer with a series of conical fan beams to scan the scene. They are arranged parallel to each other and spaced apart from each other. This is RADSAR (Ra diometrlc 5ynthetic ApertureRader) It will be revealed.

In these other embodiments, the supplemental movement means can take multiple forms. So One example is to position the first and second antennas substantially perpendicular to the antenna axis with respect to the scene. It moves in a direction parallel to the scene. Instead, supplementary means of transportation means for controllably rotating the two antennas about an axis parallel to their longitudinal axes; You can Between the two antennas along the axis perpendicular to the direction of the scene like this The effective spacing of can be controlled and varied. In still other embodiments , the two antennas are moved close to each other while maintaining a parallel relationship between the two antennas. and means for controllably moving it away. This will cause The effective spacing of the two antennas along an axis perpendicular to the direction of the beam is controllably varied. .

The data processing means conveniently generate recorded images of a plurality of scenes, each image being Data accumulated for specific frequency bands within a predetermined frequency range It is based on These images are transformed using a modified Radon transform algorithm. Conveniently generated from accumulated data.

Other features and advantages of the invention will be apparent from the accompanying drawings, which illustrate by way of example the principles of the invention. It will become clear from the following description of preferred embodiments, to which reference is made.

[Brief explanation of the drawing] FIG. 1 shows a radiometric imager according to one embodiment of the frequency dispersion of the present invention. Fig. 2 shows the linear array antenna of Fig. 1, with two Figure 3 represents the conical fan beam for the separated frequencies of Figure 1. Intersection of multiple conical fan beams showing ray antenna and with scanned scene 4(a) and (b) represent two exemplary rotational positions and all at the same frequency F o for several exemplary locking positions on the main beam. illustrating two sets of fan beam intersections with imaged scenes; Figure 5 is for multiple rotational positions for fan beam and spinrad diagrams. Shows the intersection of a single pixel P and multiple Fo fan beams in the imaged scene. 6, each spaced apart to form a scanning interferometer. Two frequency dispersive linear array antennas (RADSAR) arranged in parallel Figure 2 briefly illustrates another embodiment of the invention, including:

[Example] Referring to the drawings, in particular in FIGS. 1 to 3, scene 11 (FIG. 3) is scanned. and the first stage of the radiometric imager to generate a set of recorded images of the scene. 1 embodiment is shown, each image representing radiation received in a unique narrow frequency band. It represents. The radiometric imager consists of a single frequency dispersive linear array. The antenna 13 receives light from a series of conical fan beams. generates an output signal based on the radiation emitted. The two exemplary fan beams are It is designated by reference number 15 in the figure. Each fan beam has its own narrow It collects radiation in a frequency band, regardless of the direction around the circle in which the radiation is received. without affecting the output signal. These frequency bands range at certain extreme angles. from the low frequency of Fo to the high frequency of FrL at the opposite extreme angle . A fan beam can be either multiple separate conical beams or a continuum of beams It is.

The antenna 13 comprises a long feed line with an input port at one end and a load at the other end. A conventional traveling wave linear array is preferred. The radiator runs along its length. is connected to the power supply line.

As best shown in FIG. The conical fan beam 15 is arranged in a plurality of spaced conical sections 16. intersects with lane 11. If the scene is exactly flat, these conical areas are true It becomes an upper hyperbola. However, if the scene forms part of the spherical surface of the Earth, then the cone The areas form more complex curves. However, in a narrow sense, hyperbolas are these curves. It can be used as an appropriate approximation of a line.

According to the invention, the radiometric imager has a fan beam 15 that 11, with each beam intersecting each small segment of the scene many times. A scanning mechanism 17 (first (Fig. 1). In the embodiment of FIGS. 1 to 3, this mechanical scanning is Centered on an axis substantially aligned in the direction of the scene, i.e. the Z axis in FIG. controllably rotate the antenna to align the axis perpendicular to the antenna axis and parallel to the scene, i.e. That is, this is achieved by swinging the antenna around the Y axis in FIG.

For each increasing swing position, the antenna 13 completes its full rotation of 360 degrees. Rotate range. The resulting data is It is organized into a set of scans for frequency. Figures 4(a) and (b) show such runs. Two sets of tests are shown for the Fo fan beam. FIG. 4(a) shows multiple examples. The intersection of the Fo fan beam for the given oscillating position is shown for a specific rotational position. However, FIG. 4(b) shows Fo for the same exemplary rocking position for another rotational position. The intersection of the fan beams is shown. The sheet being scanned at each rotational position All segments in 11 are intersected simultaneously by each fan beam. . included in the output signal generated while the antenna performs the above rocking and rotating motions. The data is stored for further processing.

Referring to FIG. 1, a radiometric imager according to a first embodiment of the present invention is shown. A simple block diagram is shown.

The antenna output signal is amplified from antenna 13 on line 19 for proper amplification. It is sent to the container 21. The amplified signal is sent to each fan beam on line 23. A bank of bandpass filters 25 with one filter is fed. fill The data signal is fed on line 27 to a bank of detection circuits 29 to detect the amplitude of the signal. be done. The detected amplitude is the intersection of the fan beam 15 with the scene 11 being scanned. n consecutive narrow frequency bands for the conical area 16 defined by the difference section represents the collection of radiation intensities received by the antenna at .

The n intensity signals generated by the bank of sensing circuits 29 are connected to the data on line 31. data is supplied to the data storage device 33, and the data storage device 33 stores the data for the next sub-segment processing. Accumulate data for this purpose. At the same time, the antenna 13 swings and rotates at a certain moment Data representing the position is provided from the scanning mechanism 17 to the data storage device 33 in line 35. This data is important because it provides a good representation of the antenna data.

The accumulated data is the spectrum of the smallest segment in the scene being scanned. The data processing device 2 is continuously processed in line 37 to determine the 9 is output. The result is a plurality of recording plane images, which are output on line 41. Images, on the other hand, each represent the received radiation in a unique narrow frequency band. .

radiated by each segment of scene 11 in a separate frequency range from Fo to Fn. The intensity of the emitted radiation is adjusted to suit all accumulated data for each segment. Measured by decomposition. In particular, for each narrow frequency band a given Radiation intensity measurements for all scans passing through the segment are taken together and averaged. be converted into Accuracy of the radiation intensity whose average value is emitted by a particular segment This is a measured value. This data decomposition method is described in the US patent referenced above. It is shown in detail in Application No. 607889. The method is practically indicated in the specification. This is a composite variation of the fan beam inversion method, which is used n times. repeated, each in a predetermined frequency range from Fo to FrL. This is done once for each narrow frequency band.

For each n narrow frequency band (i.e. F. to Fn>), The intersection of the fan beam 15 corresponding to the scene 11 as the beam scans the scene. The radiation received from the conical area 16 defined by the scene profile form a function named function or projection. The conical area is virtually straight Then, this function is the Radon transform of the scene, which is often defined in the prior art. Are known. However, since the conical area is not a straight line, the Radon transform must be slightly modified so that it can be used for mathematical processing.

Such modified Radon transforms are shown in detail in the above specification.

Figure 5 shows one intersecting scene segment P that is unique for the spinrad structure. A set of conical areas is shown for the characteristic frequency of (i.e., Fo). these If the average of the measurements of Fo radiation for all cone areas 1B is a high value, then this A high value of This is thought to be due to the corresponding increase in the price. Similarly, the plane of all these intersecting conical areas If the mean value is a relatively low value, then the radiation of Fo received from this segment is It is thought that the strength was correspondingly lower.

In FIG. 5, a relatively small number of intersecting cone areas for segment P of the scene Only the following are considered to be examples.

Antenna movement can be controlled to provide any level of resolution desired It is Noh. For example, a rocking motion is performed over a range of 40 degrees in 1/3 degree increments. , the rotational movement can similarly be performed over a range of 360 degrees in 1/3 degree increments. can. This applies to each scene segment and narrow frequency band. This is performed for 1000 intersecting cone sections.

FIG. 6 shows another embodiment of the present invention, which includes a second perimeter installed in a space. It includes a wave number dispersive linear array antenna 13'. This is called the RADSAR structure. ing. A conical fan beam of two antennas means that the two antennas are connected to scene 1. substantially larger than the distance between the antennas to form an interferometer for scanning 1'. They are arranged with a certain distance between them. Each fan beam has a predetermined The interferometer lobe pattern is determined by its frequency and the spacing between the antennas. determined according to. The signals from the two antennas are by a predetermined cone area 16' in the scene multiplied by the waveform pattern. generates a set of profiles (one for each frequency) representing the radiation emitted by the be combined (e.g., multiplied) appropriately to form

The embodiment of Figure 6 shows that the two antennas are perpendicular to the antenna axis and are being scanned. FIG. This embodiment is similar to the embodiment of FIGS. However, this is done in the embodiments shown in Figures 1 to 3. Instead of rotating the antenna about an axis aligned in the scene direction, as in , this example moves the antenna in any of a number of different ways, and these All methods function to transform the interferometer fan beam with respect to the scene.

In one example of an embodiment of the interferometer of the invention, the two antennas 13 and 13' are 2 perpendicular to the antenna axis while maintaining a constant distance between the two antennas. The displacement with respect to scene 11' along the axis parallel to , i.e. the Y axis in FIG. be operated to move. This latter motion is the result of one or two aircraft in a non-geostationary orbit. This is achieved by installing two antennas on the satellite. funbee Each beam forms an interferometer whose response characteristics are predetermined as a function of angular direction. This movement behavior depends on which particular time the signal is received. Even angular orientation can be used to resolve ambiguity. No. The data accumulated by this embodiment of the invention, as in the embodiment of FIGS. Suitable methods for processing are given in detail in the above specification. The method is clear A compound variant of the method presented in the specification, where the method described is repeated n times. once for each narrow frequency band.

Two antennas 13 and 13' in two examples of embodiments of the interferometer of the invention allow control of their effective spacing along the axis perpendicular to the direction of the scene 11'. Moved in a changing way. In one of these embodiments, the antenna so that they rotate together about an axis parallel to their own axes, i.e. the X axis in Figure 6. Made from sea urchin. In other embodiments, the two antennas are each in close proximity or controllably moved apart, ie along the Y-axis in FIG. stomach In either case, the distance between the two antennas is controllably varied for each frame. Deform the interferometer pattern of the fan beam to determine the specific direction of the radiation source detected by the antenna. allows accumulating data used to resolve ambiguities in again This data is decomposed into a set of recorded images of the scene, such as an image for each frequency. Suitable methods of production are given in the above specification. The next method will be explained in the statement. A complex variant of the one-dimensional aperture synthesis method presented, this method This is repeated n times, once for each frequency band.

From the above, the present invention provides multiple recorded images of a scene, each image having a unique narrow frequency Improved radio that corresponds to the radiation pattern received for the band It is considered to provide a metric imager. An example (spin Rad structure) provides a single frequency output signal based on multiple conical fan beams. Includes a numerically dispersive linear array antenna, where the antenna controllably oscillates about an axis vertically so that each unbeam intersects each segment of the scene multiple times. controllably rotated about an axis. In another embodiment (RADSAR structure) The radiometric imager has a second antenna placed parallel to the first antenna. frequency dispersive linear array antenna to produce a fan beam interferometer. 2 Movement of one antenna, rotation of two antennas about an axis parallel to the antenna axis , or in combination with movements in which the two antennas approach and separate. The oscillating motion of the two antennas provides important data to produce recorded images. It is something.

Although the present invention has been described in detail with reference to a preferred embodiment, it will be apparent to those skilled in the art that various modifications may be made to the invention. It will be understood that modifications may be made without departing from the scope of the invention.

Accordingly, the invention is limited only by the scope of the following claims.

FIG.2 FIG. 3 θノ international search report 1a+s+11m++l1ill＾5sUc・! mha, PcT/US8710 1194

Claims (18)

[Claims] (1) Radiometric image for determining the frequency spectrum of a two-dimensional scene In the camera, It has a vertical axis and represents characteristic frequencies extending over a predetermined frequency range. Multiple conical fan beams that intersect a 2D scene in spaced conical areas a frequency dispersive linear antenna that provides an output signal corresponding to the radiation received along the Na and The output signal consists of emissions from all segments of the scene in a predetermined frequency range. The interval is determined in a predetermined manner to include data representing the reception of all rays. substantially perpendicular to the antenna axis so that the attached conical area scans the scene. oscillation for controllably oscillating a linear antenna about a oscillation axis parallel to the scene. means and Extract and store the data contained in the output signal provided by the linear antenna. data storage means for Compensation for controllably moving linear antennas in different ways to eliminate clarity foot transportation means, Data storage to determine the frequency spectrum of virtually all segments of the scene. and a data processing means for processing data accumulated by the product means. imager. (2) The supplementary means is a linear antenna centered on an axis substantially perpendicular to the antenna axis and the swing axis. including rotation means for controllably rotating the tenna; The rocking means and the rotating means are such that each cone section intersects each segment of the scene multiple times. 2. The radiometric imager of claim 1, wherein the radiometric imager operates in conjunction with each other to (3) Claim in which the rotating means rotates the linear antenna over a range of substantially 360 degrees. 2. The radiometric imager described in 2. (4) A second frequency dispersive linear antenna that is substantially the same as the first frequency dispersive linear antenna. the first and second frequency dispersive linear antennas scan the scene; the claims each being spaced apart and in parallel relationship so as to form an interferometer for 1. The radiometric imager according to 1. (5) The supplementary moving means scans the scene being scanned by the first and second linear antennas. the direction of movement being substantially perpendicular to the longitudinal axis of the antenna; 5. The radiometric imager of claim 4, wherein the radiometric imager is direct and parallel to the scene. (6) Supplementary movement means are located between the two antennas along the axis perpendicular to the direction of the scene. relative to an axis parallel to the longitudinal axes of the two antennas so that the effective spacing is controllably varied. and means for controllably rotating the first and second linear antennas. The radiometric imager according to item 4. (7) The supplementary moving means moves the first and second linear antennas closer and closer together, respectively. Two anchors along an axis perpendicular to the direction of the scene while controllably moving apart. maintain their parallelism so that the effective spacing between the antennas is controllably varied. 5. The radiometric imager of claim 4, further comprising means for determining. (8) The data processing means uses a modified Radon transform algorithm to The radiometric imager of claim 1, wherein the radiometric imager processes data. (9) The data processing means generates recorded images of a plurality of scenes, each image being Based on data accumulated for specific frequency bands in the frequency range The radiometric imager of claim 1. (10) A geometric tool for determining the frequency spectrum of a two-dimensional scene In imaging methods, a characteristic having a vertical axis and extending over a predetermined frequency range is Intersect the two-dimensional scene in multiple spaced conical areas representing the frequency provides output signals corresponding to radiation received along multiple conical fan beams. A frequency dispersive linear antenna is installed, The output signal provided by the linear antenna is preset to contain data representing the reception of all radiation from all segments of the zone. The implementation is performed such that the spaced conical areas scan the scene in a defined manner. A linear antenna is constrained with respect to a swing axis that is qualitatively perpendicular to the antenna axis and parallel to the scene. data contained in the output signal provided by the linear antenna. extract and accumulate data, Straight line to eliminate ambiguity in data accumulated by data accumulation means Controllably move the antenna to cover virtually any frequency spectrum of a segment of the scene. Process the data accumulated in the extraction and accumulation steps to determine the A radiometric imaging method comprising the steps of: (11) The controllably moving step is substantially perpendicular to the antenna axis and the rocking axis. controllably rotating the linear antenna about an axis; Controllably rocking steps and controllably rotating steps move each circle multiple times 11. The conical section is operated together to intersect each segment of the scene. radiometric imaging methods. (12) The controllably rotating step provides a linear antenna with a range of substantially 360 degrees. 12. The radiometric imaging method according to claim 11, further comprising rotating the . (13) Providing a second frequency dispersive linear antenna that is substantially the same as the first linear antenna. the first and second frequency dispersive linear antennas define the scene; spaced apart and parallel to each other to form an interferometer for scanning The radiometric imaging method according to claim 10. (14) controllably moving the first and second linear antennas; The direction of the movement is substantially the same as that of the antenna. 14. The radiometric device of claim 13, wherein the radiometric device is perpendicular to the longitudinal axis of the na and parallel to the scene. Imaging method. (15) The controllably moving step consists of two steps along an axis perpendicular to the direction of the scene. the longitudinal axes of the two antennas such that the effective spacing between the antennas is controllably varied; a step for controllably rotating the first and second linear antennas about an axis parallel to the 14. The radiometric imager of claim 13, comprising: a. (16) controllably moving the first and second linear antennas; an axis perpendicular to the direction of the scene, each moving controllably toward and away from the scene. of the two antennas such that the effective spacing between them along is controllably varied. 14. The radiometric image of claim 13, comprising the step of maintaining parallelism. method. (17) The processing step uses a modified Radon transform algorithm to 11. The radiometric imaging method of claim 10, comprising the step of processing the data. Law. (18) The processing step generates recorded images of multiple scenes, each image being Based on data accumulated for specific frequency bands in the frequency range The radiometric imaging method according to claim 10.