WO2018111211A1 - A monopulse radar antenna system - Google Patents

A monopulse radar antenna system Download PDF

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Publication number
WO2018111211A1
WO2018111211A1 PCT/TR2017/050456 TR2017050456W WO2018111211A1 WO 2018111211 A1 WO2018111211 A1 WO 2018111211A1 TR 2017050456 W TR2017050456 W TR 2017050456W WO 2018111211 A1 WO2018111211 A1 WO 2018111211A1
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WO
WIPO (PCT)
Prior art keywords
antenna
waveguide
monopulse radar
antenna system
card
Prior art date
Application number
PCT/TR2017/050456
Other languages
French (fr)
Inventor
Gökhan GÜLTEPE
Doğanay DOĞAN
Özlem AYDIN ÇİVİ
Original Assignee
Aselsan Elektroni̇k Sanayi̇ Ve Ti̇caret Anoni̇m Şi̇rketi̇
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Aselsan Elektroni̇k Sanayi̇ Ve Ti̇caret Anoni̇m Şi̇rketi̇ filed Critical Aselsan Elektroni̇k Sanayi̇ Ve Ti̇caret Anoni̇m Şi̇rketi̇
Publication of WO2018111211A1 publication Critical patent/WO2018111211A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q21/00—Antenna arrays or systems
    • H01Q21/0006—Particular feeding systems
    • H01Q21/0037—Particular feeding systems linear waveguide fed arrays
    • H01Q21/0043—Slotted waveguides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q13/00—Waveguide horns or mouths; Slot antennas; Leaky-waveguide antennas; Equivalent structures causing radiation along the transmission path of a guided wave
    • H01Q13/08—Radiating ends of two-conductor microwave transmission lines, e.g. of coaxial lines, of microstrip lines
    • H01Q13/085—Slot-line radiating ends
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q25/00—Antennas or antenna systems providing at least two radiating patterns
    • H01Q25/02—Antennas or antenna systems providing at least two radiating patterns providing sum and difference patterns

Definitions

  • the present invention is related to antenna structures used in monopulse radar systems.
  • signals are transmitted towards the region, and the reflections from that region are sensed by processing the echo signals from the region.
  • the sensed reflections allow having information about the objects in the region.
  • the spatial distribution of the signals that are sent to the concerned region is defined as beam.
  • the beams are generated by an antenna, and sent to a corresponding region.
  • One of the beamforming techniques used in identifying a target is the use of monopulse radar beams.
  • Monopulse radars receive back the reflections of the signal sent to the target, and sample them by means of a plurality of different beams formed at the same time. The location of the target can be detected by comparing the signals received from different beams.
  • the most commonly used beams in monopulse radars are sum and difference beams. Sum beams are obtained by equiphase excitation of the entire antenna aperture. In this case, an approximately Gauss-shaped beam is formed.
  • a difference beam one half of the antenna aperture is excited with a phase difference of 180 degrees with respect to the other half.
  • a beam that cannot receive signal from the main axis emerges.
  • Travelling wave waveguide array antennas are often preferred in radar applications due to their easy producibility, capability of high power emission and high energy efficiency.
  • the desired beam is formed by the interference of the fields emitted from the slots that are opened on the waveguide arrays in various forms at periodical intervals.
  • the contribution of each slot to the main beam is determined by the conductance of that slot. Amplitude distribution of the array is formed by the adjusted conductances.
  • the amplitude distribution in the travelling wave waveguide arrays is not affected by the feed mechanism of the slots, the amplitude distribution of the array is distorted with frequency on the frequency axis later than that of the standing wave waveguide. Therefore, a design with a broader band than that of standing wave waveguide is possible. Frequency-dependent distortion is only caused by the slot conductances that vary depending on the frequency. Nonetheless, this method is not suitable for a wideband design due to the slots used therein.
  • the monopulse radar antenna system developed according to the present invention comprises at least two waveguides, each of which comprising at least one ridge and at least one slot, fitting in a single element spacing; at least two antenna cards, each of which has at least one antenna arm thereon and each of which is disposed in at least one slot provided on at least one waveguide; at least one connection foot for fixing each antenna card to the waveguide having the corresponding slot in which the each antenna card is positioned and for providing electrical connection between the waveguide and at least one of the antenna arms disposed on the antenna card; at least one connection probe, at least one side of each of which is connected with at least one other of the antenna arms disposed on the antenna card, at least the other side of which extends into the waveguide through said slot, and feeds the antenna arm to which it is connected through the waveguide to which it is connected.
  • the monopulse radar antenna system of the present invention easy producibility is ensured because said waveguides are preferably in the form of a travelling wave waveguide. In addition, due to the high power emission capability and high energy efficiency of the travelling wave waveguide, it is ensured that the monopulse radar antenna system of the present invention operates efficiently. Furthermore, the antenna card in the form of an integrated printed circuit provided onto the waveguides in the form of travelling wave waveguide enables the frequency band to widen with respect to the previous structures.
  • An object of the invention is to develop a monopulse radar antenna system to form low side lobe level beams in monopulse radar systems. Another object of the invention is to develop a monopulse radar antenna system, the frequency bandwidth of which is wide.
  • Yet another object of the invention is to develop a robust monopulse radar antenna system.
  • Figure 1 is a perspective view of the monopulse radar antenna system according to the present invention.
  • Figure 2 is a side sectional view of the monopulse radar antenna system according to the present invention.
  • Figures 3 is a top view of the monopulse radar antenna system according to the present invention.
  • Figure 4 is a front sectional view of the monopulse radar antenna system according to the present invention.
  • Figure 5 is a perspective view of an alternative embodiment of the monopulse radar antenna system according to the present invention.
  • Figure 8 is a graph of angle versus dB of ideal sum and difference beams in the monopulse radar antenna system according to the present invention. All the parts illustrated in the drawings are individually assigned a reference numeral and the corresponding terms of these numbers are listed as follows:
  • the monopulse radars used for detection of location of a target reflections of the signal sent to the target are received back by means of the sum and difference beams formed at the same time, and these beams are compared so as to determine the position of the target with respect to the radar. It is preferred that frequency bandwidth of the beams formed for scanning different regions and different targets by the radar is wide. For this reason, with the present invention, there is provided a monopulse radar antenna system which allows for obtaining beams, the frequency bandwidth of which is wide, for monopulse radars. Widening of the frequency band is ensured by integrating the printed circuit antenna card into the structure.
  • the monopulse radar antenna system (S), the exemplary views of which are illustrated in Figures 1-6, according to the present invention, comprises at least two waveguides (1), each of which comprising at least one ridge (2) and at least one slot (3) and fit in at least a single element spacing; at least two antenna cards (4), each of which has at least one antenna arm (5) thereon and each of which is disposed in at least one slot (3) provided on at least one waveguide (1); at least two connection feet (6) for fixing each antenna card (4) to the waveguide (1) having the corresponding slot (3) in which the each antenna card (4) is positioned and for providing electrical connection between the waveguide (1) and at least one of the antenna arms (5) disposed on the antenna card (4) (in other words, for grounding said antenna arm (5) through the waveguide (1)); and at least one connection probe (7), at least one side of each of which is connected with at least one of the antenna arms (5) disposed on the antenna card (4), at least the other side of which extends into the waveguide (1) through said slot (3), and feeds
  • At least one of the said waveguides (1) is in connection with a difference signal source whereas at least one other of the waveguides (1 ) is in connection with a sum signal source.
  • the difference signal passing through the waveguide (1) that is in connection with the difference signal source is fed, by means of the connection probe (7), to the antenna arm (5) to which said connection probe (7) is connected so that a difference beam is formed in the antenna card (4) to which the antenna arm (5) is connected.
  • the sum signal passing through the waveguide (1 ) that is in connection with the sum signal source is fed, by means of the connection probe (7), to the antenna arm (5) to which said connection probe (7) is connected so that a sum beam is formed in the antenna card (4) to which the antenna arm (5) is connected.
  • said monopulse radar antenna system (8) comprises at least two support wails (8) which are provided on the waveguides (1) and to which the antenna cards are connected on at least two sides.
  • the support wall (8) which is preferably in the form of a metal plate, prevents the antenna cards (4) from being damaged due to the external environmental conditions (e.g., wind etc.) by increasing the strength of said antenna cards (4).
  • each antenna card (4) comprises at least one insulating body (e.g. a PCB card) on which said antenna arms (5) are placed.
  • said antenna arms (5) have a structure of a microstrip formed on the insulating body by, for example, a printed circuit production method.
  • the antenna arms (5) provided on each antenna card (4) are in the form of a dipole antenna.
  • the antenna arms (5) provided on each antenna card (4) are in the form of a Vivaldi antenna.
  • the monopuise radar antenna system (8) comprises a plurality of (at least two) waveguides (1) that are positioned adjacent to each other as shown in Figure 5.
  • the adjacent waveguides (1) are in connection with different signal sources.
  • the first waveguide (1) is connected to a difference signal source
  • the second waveguide (1) is connected to a sum signal source
  • the third waveguide (1) is connected to a difference signal source
  • the fourth waveguide (1) is connected to a sum signal source.
  • the odd numbered waveguides (1) form an array of difference (1 a)
  • the even numbered waveguides (1) form an array of sum (1 b).
  • the sum pattern is obtained when only the signals received from the array of sum (1 b) are combined
  • the difference pattern is obtained when only the signals received from the array of difference (1a) are combined. Since the array of sum (1 b) and the array of difference (1 a) can operate independently, the sum and difference patterns are able to be obtained at the same time.
  • the graph of angle versus dB of the sum beam (H2) and the difference beam (H1) formed by means of the array of sum (1 b) and the array of difference (1 b) is shown in Figure 6.
  • the monopu!se radar antenna system (S) of the present invention easy producibi!ity is ensured because said waveguides (1) are preferably in the form of a travelling wave waveguide.
  • the monopulse radar antenna system (8) of the present invention operates efficiently.
  • the antenna card (4) in the form of an integrated printed circuit provided onto the waveguides (1) in the form of travelling wave waveguide enables the frequency band to widen with respect to the previous structures.

Abstract

The monopulse radar antenna system (S) developed according to the present invention comprises at least two waveguides (1), each of which comprising at least one ridge (2) and at least one slot (3), fitting in an element spacing; at least two antenna cards (4), each of which has at least one antenna arm (5) thereon and each of which is disposed in at least one slot (3) provided on at least one waveguide (1); at least one connection foot (6) for fixing each antenna card (4) to the waveguide (1) having the corresponding slot (3) in which the each antenna card (4) is positioned and for providing electrical connection between the waveguide (1) and at least one of the antenna arms (5) disposed on the antenna card (4); and at least one connection probe (7), at least one side of each of which is connected with at least one other of the antenna arms (5) disposed on the antenna card (4), at least the other side of which extends into the waveguide (1) through said slot (3), and feeds the antenna arm (5) to which it is connected through the waveguide (1) to which it is connected.

Description

A MONOPULSE RADAR ANTENNA SYSTEM
Field of the Invention The present invention is related to antenna structures used in monopulse radar systems.
Background of the Invention
In radar systems, in order to scan objects in a region, signals are transmitted towards the region, and the reflections from that region are sensed by processing the echo signals from the region. The sensed reflections allow having information about the objects in the region. Here, the spatial distribution of the signals that are sent to the concerned region is defined as beam. The beams are generated by an antenna, and sent to a corresponding region.
In the contemporary art, different beamforming techniques are used for accurate detection of the location of a target in a region. One of the beamforming techniques used in identifying a target is the use of monopulse radar beams. Monopulse radars receive back the reflections of the signal sent to the target, and sample them by means of a plurality of different beams formed at the same time. The location of the target can be detected by comparing the signals received from different beams. The most commonly used beams in monopulse radars are sum and difference beams. Sum beams are obtained by equiphase excitation of the entire antenna aperture. In this case, an approximately Gauss-shaped beam is formed. On the other hand, in a difference beam, one half of the antenna aperture is excited with a phase difference of 180 degrees with respect to the other half. In this case, a beam that cannot receive signal from the main axis emerges. Travelling wave waveguide array antennas are often preferred in radar applications due to their easy producibility, capability of high power emission and high energy efficiency. The desired beam is formed by the interference of the fields emitted from the slots that are opened on the waveguide arrays in various forms at periodical intervals. The contribution of each slot to the main beam is determined by the conductance of that slot. Amplitude distribution of the array is formed by the adjusted conductances. Since the amplitude distribution in the travelling wave waveguide arrays is not affected by the feed mechanism of the slots, the amplitude distribution of the array is distorted with frequency on the frequency axis later than that of the standing wave waveguide. Therefore, a design with a broader band than that of standing wave waveguide is possible. Frequency-dependent distortion is only caused by the slot conductances that vary depending on the frequency. Nonetheless, this method is not suitable for a wideband design due to the slots used therein.
The prior art concerning the travelling wave waveguide antenna systems that are used in monopulse radars is disclosed by Richard R. Kinsey in the document "IEEE Transactions on Antennas and Propagation, vol. 47, no. 3, March 1999". According to this antenna system, a sum beam and a difference beam are obtained such that the successive waveguide arrays are excited by sum minus difference and sum plus difference beams, and the sum or difference of these excitation beams are obtained via a hybrid module. In this system, a tilted narrow edge-slotted travelling wave waveguide array is used. However, it has been seen that wideband beams cannot be formed in this structure due to the frequency-dependent characteristics of the slots caused by the use of thin waveguides. In addition, since the used slots are tilted, cross-polarization lobes appear at high side lobe levels in these arrays.
Brief Description of the Invention The monopulse radar antenna system developed according to the present invention comprises at least two waveguides, each of which comprising at least one ridge and at least one slot, fitting in a single element spacing; at least two antenna cards, each of which has at least one antenna arm thereon and each of which is disposed in at least one slot provided on at least one waveguide; at least one connection foot for fixing each antenna card to the waveguide having the corresponding slot in which the each antenna card is positioned and for providing electrical connection between the waveguide and at least one of the antenna arms disposed on the antenna card; at least one connection probe, at least one side of each of which is connected with at least one other of the antenna arms disposed on the antenna card, at least the other side of which extends into the waveguide through said slot, and feeds the antenna arm to which it is connected through the waveguide to which it is connected.
With the monopulse radar antenna system of the present invention, easy producibility is ensured because said waveguides are preferably in the form of a travelling wave waveguide. In addition, due to the high power emission capability and high energy efficiency of the travelling wave waveguide, it is ensured that the monopulse radar antenna system of the present invention operates efficiently. Furthermore, the antenna card in the form of an integrated printed circuit provided onto the waveguides in the form of travelling wave waveguide enables the frequency band to widen with respect to the previous structures. Object of the invention
An object of the invention is to develop a monopulse radar antenna system to form low side lobe level beams in monopulse radar systems. Another object of the invention is to develop a monopulse radar antenna system, the frequency bandwidth of which is wide.
Yet another object of the invention is to develop a robust monopulse radar antenna system.
Description of the Drawings
Exemplary embodiments of the monopulse radar antenna system developed according to the present invention are illustrated in the attached drawings, wherein:
Figure 1 is a perspective view of the monopulse radar antenna system according to the present invention. Figure 2 is a side sectional view of the monopulse radar antenna system according to the present invention.
Figures 3 is a top view of the monopulse radar antenna system according to the present invention.
Figure 4 is a front sectional view of the monopulse radar antenna system according to the present invention.
Figure 5 is a perspective view of an alternative embodiment of the monopulse radar antenna system according to the present invention.
Figure 8 is a graph of angle versus dB of ideal sum and difference beams in the monopulse radar antenna system according to the present invention. All the parts illustrated in the drawings are individually assigned a reference numeral and the corresponding terms of these numbers are listed as follows:
Monopulse radar antenna system (S)
Difference beam (H1)
Sum beam (H2) Waveguide (1)
Array of difference (1 a)
Array of sum (1 b)
Ridge (2) Slot (3)
Antenna card (4)
Antenna arm (5)
Connection foot (6)
Connection probe (7) Support wall (8)
Description of Invention
In the monopulse radars used for detection of location of a target, reflections of the signal sent to the target are received back by means of the sum and difference beams formed at the same time, and these beams are compared so as to determine the position of the target with respect to the radar. It is preferred that frequency bandwidth of the beams formed for scanning different regions and different targets by the radar is wide. For this reason, with the present invention, there is provided a monopulse radar antenna system which allows for obtaining beams, the frequency bandwidth of which is wide, for monopulse radars. Widening of the frequency band is ensured by integrating the printed circuit antenna card into the structure.
The monopulse radar antenna system (S), the exemplary views of which are illustrated in Figures 1-6, according to the present invention, comprises at least two waveguides (1), each of which comprising at least one ridge (2) and at least one slot (3) and fit in at least a single element spacing; at least two antenna cards (4), each of which has at least one antenna arm (5) thereon and each of which is disposed in at least one slot (3) provided on at least one waveguide (1); at least two connection feet (6) for fixing each antenna card (4) to the waveguide (1) having the corresponding slot (3) in which the each antenna card (4) is positioned and for providing electrical connection between the waveguide (1) and at least one of the antenna arms (5) disposed on the antenna card (4) (in other words, for grounding said antenna arm (5) through the waveguide (1)); and at least one connection probe (7), at least one side of each of which is connected with at least one of the antenna arms (5) disposed on the antenna card (4), at least the other side of which extends into the waveguide (1) through said slot (3), and feeds the antenna arm (5) to which it is connected through the waveguide (1) to which it is connected. Here, said waveguide (1) is preferably in the form of a travelling wave waveguide.
In an exemplary embodiment of the invention, at least one of the said waveguides (1) is in connection with a difference signal source whereas at least one other of the waveguides (1 ) is in connection with a sum signal source. In this embodiment, the difference signal passing through the waveguide (1) that is in connection with the difference signal source is fed, by means of the connection probe (7), to the antenna arm (5) to which said connection probe (7) is connected so that a difference beam is formed in the antenna card (4) to which the antenna arm (5) is connected. Similarly, the sum signal passing through the waveguide (1 ) that is in connection with the sum signal source is fed, by means of the connection probe (7), to the antenna arm (5) to which said connection probe (7) is connected so that a sum beam is formed in the antenna card (4) to which the antenna arm (5) is connected.
In a preferred embodiment of the invention, said monopulse radar antenna system (8) comprises at least two support wails (8) which are provided on the waveguides (1) and to which the antenna cards are connected on at least two sides. The support wall (8), which is preferably in the form of a metal plate, prevents the antenna cards (4) from being damaged due to the external environmental conditions (e.g., wind etc.) by increasing the strength of said antenna cards (4).
In another preferred embodiment of the invention, each antenna card (4) comprises at least one insulating body (e.g. a PCB card) on which said antenna arms (5) are placed. In this embodiment, said antenna arms (5) have a structure of a microstrip formed on the insulating body by, for example, a printed circuit production method.
In another preferred embodiment of the invention, the antenna arms (5) provided on each antenna card (4) are in the form of a dipole antenna. On the other hand, in an alternative embodiment, the antenna arms (5) provided on each antenna card (4) are in the form of a Vivaldi antenna. Yet, in another preferred embodiment of the invention, the monopuise radar antenna system (8) comprises a plurality of (at least two) waveguides (1) that are positioned adjacent to each other as shown in Figure 5. In a preferred embodiment, the adjacent waveguides (1) are in connection with different signal sources. In other words, for example, the first waveguide (1) is connected to a difference signal source, the second waveguide (1) is connected to a sum signal source, the third waveguide (1) is connected to a difference signal source, and the fourth waveguide (1) is connected to a sum signal source. To put it differently, the odd numbered waveguides (1) form an array of difference (1 a) and the even numbered waveguides (1) form an array of sum (1 b). In this embodiment, the sum pattern is obtained when only the signals received from the array of sum (1 b) are combined, whereas the difference pattern is obtained when only the signals received from the array of difference (1a) are combined. Since the array of sum (1 b) and the array of difference (1 a) can operate independently, the sum and difference patterns are able to be obtained at the same time. In an exemplary embodiment of the invention, the graph of angle versus dB of the sum beam (H2) and the difference beam (H1) formed by means of the array of sum (1 b) and the array of difference (1 b) is shown in Figure 6.
With the monopu!se radar antenna system (S) of the present invention, easy producibi!ity is ensured because said waveguides (1) are preferably in the form of a travelling wave waveguide. In addition, due to the high power emission capability and high energy efficiency of the travelling wave waveguide, it is ensured that the monopulse radar antenna system (8) of the present invention operates efficiently. Furthermore, the antenna card (4) in the form of an integrated printed circuit provided onto the waveguides (1) in the form of travelling wave waveguide enables the frequency band to widen with respect to the previous structures.

Claims

A monopulse radar antenna system (S) characterized by comprising: at least two waveguides (1), each of which comprising at least one ridge
(2) and at least one slot (3) and fit in a single element spacing;
at least two antenna cards (4), each of which has at least one antenna arm (5) thereon and each of which is disposed in at least one slot (3) provided on at least one waveguide (1);
at least one connection foot (6) for fixing each antenna card (4) to the waveguide (1) having the corresponding slot
(3) in which the each antenna card (4) is positioned and for providing electrical connection between the waveguide (1) and at least one of the antenna arms (5) disposed on the antenna card (4); and at least one connection probe (7), at least one side of each of which is connected with at least one of the antenna arms (5) disposed on the antenna card
(4), at least the other side of which extends into the waveguide (1) through said slot (3), and feeds the antenna arm
(5) to which it is connected through the waveguide (1) to which it is connected.
A monopulse radar antenna system (S) according to Claim 1 , characterized in that the waveguide (1) is in the form of a travelling wave waveguide.
A monopulse radar antenna system (S) according to Claim 1 , characterized in that at least one of the said waveguides (1) is in connection with a difference signal source whereas at least one other of the waveguides (1) is in connection with a sum signal source.
A monopulse radar antenna system (S) according to Claim 1 , characterized by comprising at least two support walls (8) which are provided on the waveguides (1) and to which the antenna cards (4) are connected on at least two sides.
A monopulse radar antenna system (S) according to Claim 4, characterized in that the support wall (8) is in the form of a metal plate.
6. A monopulse radar antenna system (S) according to Claim 1 , characterized in that each antenna card (4) comprises at least one insulating body on which said antenna arms (5) are placed.
7. A monopulse radar antenna system (S) according to Claim 6, characterized in that said antenna arms (5) have a structure of a microstrip formed on the insulating body.
8. A monopulse radar antenna system (S) according to Claim 1 , characterized in that the antenna arms (5) provided on each antenna card (4) are in the form of a dipole, monopole, Vivaldi or other printed circuit antenna having a mono-layered or antipodal structure.
9. A monopulse radar antenna system (S) according to Claim 1 , characterized by comprising at least two waveguides (1) positioned adjacent to each other.
10. A monopulse radar antenna system (S) according to Claim 10, characterized in that the adjacent waveguides (1) are in connection with different signal sources.
PCT/TR2017/050456 2016-12-16 2017-09-28 A monopulse radar antenna system WO2018111211A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
TR2016/18802A TR201618802A1 (en) 2016-12-16 2016-12-16 A single pulse radar antenna system.
TR2016/18802 2016-12-16

Publications (1)

Publication Number Publication Date
WO2018111211A1 true WO2018111211A1 (en) 2018-06-21

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3636563A (en) * 1968-05-31 1972-01-18 Emi Ltd Aerial arrangements
EP0257881A2 (en) * 1986-08-29 1988-03-02 Decca Limited Slotted waveguide antenna and array
US20120007771A1 (en) * 2010-07-06 2012-01-12 Tetsuya Miyagawa Slot array antenna and radar device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3636563A (en) * 1968-05-31 1972-01-18 Emi Ltd Aerial arrangements
EP0257881A2 (en) * 1986-08-29 1988-03-02 Decca Limited Slotted waveguide antenna and array
US20120007771A1 (en) * 2010-07-06 2012-01-12 Tetsuya Miyagawa Slot array antenna and radar device

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
RICHARD R. KINSEY, IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, vol. 47, no. 3, March 1999 (1999-03-01)

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