US-20260128535-A1 - ACTIVE RECEIVE ANTENNA

US20260128535A1US 20260128535 A1US20260128535 A1US 20260128535A1US-20260128535-A1

Abstract

An exemplary receive antenna having a conductive surface. The conductive surface includes an aperture configured to operate as a slot antenna, and one or more amplifiers or buffer amplifiers is electrically connected across the aperture. At least one feed is connected between the one or more amplifiers and the aperture. An input impedance Z B of each of the one or more amplifiers at the at least one feed location is lower than 0.5× an impedance of the aperture Z A at a first resonance frequency.

Inventors

Carson White
Ryan Quarfoth
Amit Patel

Assignees

HRL LABORATORIES, LLC

Dates

Publication Date: 20260507
Application Date: 20251104

Claims (20)

1 . A receive antenna, comprising: a conductive surface having an aperture configured to operate as a slot antenna having a first resonance frequency; and an amplifier electrically connected across the aperture, wherein a magnitude of an input impedance of the amplifier is lower than one half of a magnitude of an impedance of the aperture at the first resonance frequency.
2 . The receive antenna of claim 1 , wherein the aperture includes a conductive cavity.
3 . The receive antenna of claim 2 , wherein a first resonance frequency of the conductive cavity is near the first resonance frequency of the slot antenna.
4 . The receive antenna of claim 1 , wherein the amplifier is disposed no more than one tenth of a wavelength from the aperture.
5 . The receive antenna of claim 1 , wherein the first resonance frequency of the slot antenna is below 2 GHz.
6 . The receive antenna of claim 1 , wherein a length of the aperture is less than 0.5 wavelengths.
7 . The receive antenna of claim 1 , wherein the amplifier comprises a common gate amplifier or common base amplifier.
8 . The receive antenna of claim 1 , wherein the amplifier is a buffer having an input stage and an output stage.
9 . The receive antenna of claim 8 , wherein the input stage includes a common gate amplifier, and the output stage includes a common source amplifier.
10 . The receive antenna of claim 8 , wherein an input impedance of the input stage is lower than an input impedance of the output stage.
11 . The receive antenna of claim 8 , wherein at least one of the input stage and the output stage is configured as a monolithic integrated circuit.
12 . The receive antenna of claim 8 , wherein the buffer is interfaced to the slot antenna through an electrical connection.
13 . The receive antenna of claim 1 , comprising: a plurality of amplifiers including the amplifier; a plurality of feeds; and a mode former, wherein the mode former has a plurality of ports and is configured to produce linear combinations of output signals received from the amplifiers.
14 . The receive antenna of claim 1 , comprising: a plurality of amplifiers including the amplifier; and a plurality of feeds, wherein a number of outputs corresponding to the plurality of amplifiers is greater than or equal to a number of signals received by the plurality of feeds.
15 . The receive antenna of claim 1 , comprising: a plurality of amplifiers including the amplifier; and a plurality of feeds, wherein: the receive antenna is configured to operate over a band of frequencies, and a spacing between the plurality of feeds is less than one wavelength at a maximum frequency within the band.
16 . A receive antenna, comprising: a conformal slot antenna formed in a conductive surface; and a buffer electrically connected to the conformal slot antenna, wherein the buffer includes an input stage and an output stage, the input stage having a lower impedance than the output stage.
17 . The receive antenna of claim 16 , comprising: a plurality of buffers including the buffer; a plurality of feeds connected between the conformal slot antenna and the buffers; a plurality of ports; and a mode former, wherein: each port is connected to receive an output produced by one of the buffers, and the mode former is connected to receive a signal from each port and generate a linear combination of outputs produced by the buffers.
18 . The receive antenna of claim 17 , wherein to generate the linear combination of outputs produced by the buffers, the mode former is configured to sum all the received outputs in-phase.
19 . The receive antenna of claim 17 , wherein: an aperture of the slot antenna is divided into two halves, and to generate the linear combination of outputs produced by the buffers, the mode former is configured to: sum the received signals from a first half of the aperture with a phase of substantially zero degrees; and sum the received signals from a second half of the aperture with a phase of substantially 180 degrees.
20 . The receive antenna of claim 17 , wherein: an aperture of the slot antenna is divided into two halves, and to generate the linear combination of outputs produced by the buffers, the mode former is configured to: sum all the received outputs in-phase; sum the received signals from a first half of the aperture with a phase of substantially zero degrees; and sum the received signals from a second half of the aperture with a phase of substantially 180 degrees.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S) The present application is a continuation of U.S. patent application Ser. No. 18/356,364, filed Jul. 21, 2023, entitled “ACTIVE RECEIVE ANTENNA”, the entire contents of all of the documents identified in this paragraph are incorporated herein by reference. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT This invention was made with Government support, contract number 18-C-8681. The Government has certain rights in this invention. FIELD The present disclosure relates to an active receive antenna, and more particularly to a conformal antenna with broadband reception. BACKGROUND INFORMATION In known antenna designs an input impedance of the antenna must be matched to a transmission line impedance (e.g., 50 Ohms) for proper signal reception within a specified bandwidth. A poor impedance match directly degrades receiver sensitivity. The general rule of thumb for a receive antenna is that the amplifier should have high input impedance to maximize the input voltage. Conformal antennas can include flat array antennas that are designed to follow a prescribed shape over a slot or aperture. These antennas are suitable for mounting on curved surfaces of land, air, and space vehicles. The gain of the conformal antenna is dependent on the antenna's shape. Conformal antennas can have a small bandwidth due to the strong resonant loading of the cavity backing, which results in a high quality factor and a narrowband response. Several techniques have been used to reduce the quality factor but can result in poor reception. Broadband receive antennas can come in various forms and configurations, such as a blade antenna, active monopole antenna, an active dipole antenna, a passive cavity-backed-slot antenna, and a loop-stick antenna. Blade antennas are used in designs requiring broadband sensitive reception. These antennas are designed to protrude from the conductive surface on which it is mounted. In known implementations, a blade antenna extends from the mounting surface in a normal direction. The physical profile of the blade antenna and its mounting characteristics can negatively impact aerodynamics of a vehicle, as well as fuel economy. Moreover, in some platforms and applications, the shape and placement of a blade antenna on the conductive surface could increase the antenna's susceptibility to breakage. Active monopole and dipole antennas are unique in that a poor impedance match does not necessarily affect receiver sensitivity. Further, these antennas are capacitive and operate below the first resonance. An active monopole antenna has a rod-shaped conductor that extends in a normal direction or perpendicular to the conductive surface to which it is mounted. The active dipole antenna has two identical rod conductors that extend perpendicularly from the conductive plane. In aerospace applications, the active monopole and dipole antennas can be implemented in the shape of a blade antenna. Passive cavity-backed-slot antennas are used as high-gain sensitive conformal antennas. One drawback is that they operate in a narrowband. Several techniques can be used to increase bandwidth, but also lead to a reduction in gain and receiver sensitivity. Loop-stick antennas can be formed with a core of material with magnetic permeability surrounded by a coil of wire. Loop-stick antennas achieve broad bandwidth and can be deployed conformally, but they have low antenna gain and, therefore, poor sensitivity. SUMMARY An exemplary receive antenna is disclosed comprising: a conductive surface having an aperture configured to operate as a slot antenna; and one or more amplifiers electrically connected across the aperture, at least one feed connected between the one or more amplifiers and the aperture; wherein an input impedance ZB of each of the one or more amplifiers at the at least one feed location is lower than 0.5× an impedance of the aperture ZA at a first resonance frequency. Another exemplary receive antenna is disclosed, comprising: a conformal slot antenna formed in a conductive surface; and plural buffers electrically connected to the slot antenna, wherein each buffer includes an input stage and an output stage, the input stage having a lower impedance than the output stage. DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a receive antenna in accordance with an exemplary embodiment of the present disclosure. FIG. 2 illustrates a cavity-backed slot antenna (CBSA) in accordance with an exemplary embodiment of the present disclosure. FIG. 3A illustrates a performance of the slot antenna based input impedance in accordance with an exemplary embodiment of the present disclosure. FIGS. 3B and 3C illustrate performance of a slot antenna in accordance with a known implementation. FIG. 4 illustrates a buffer amplifier in accordance with an exemplary embodiment of the present disclosure. FIG. 5 illustrates a buffer amplifier mounted to a PCB in accordance with an exemplary embodiment of