Electromagnetic radiation sensor

• US 5,030,962 A
• Filed: 02/03/1989
• Issued: 07/09/1991
• Est. Priority Date: 03/11/1981
• Status: Expired due to Term

• Current Assignee: Qinetiq Limited (QinetiQ Group PLC)
• Original Assignee: Secretary of State of Defence In Her Britannic Majesty's Government of The United Kingdom of Great Britian and Northern Ireland
• Inventors: Rees, Huw D.
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US07/314,693
• Time in Patent Office: 886 Days
• Field of Search: 343/700 MS File, 343/785, 343/753, 343/909, 343/911 R
• US Class Current: 343/700.0MS
• CPC Class Codes: H01Q 1/247 with frequency mixer, e.g. for direct satellite reception or Doppler radar
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 9/285 Planar dipole H01Q9/065 takes precedence; patch antenna H01Q9/0407

Abstract

An electromagnetic radiation sensor for use at microwave frequencies compes a sheet substrate bearing an array of dipolar antennas. The antennas have respective mixer diodes connected between adjacent dipole limbs, and the antenna array is located in the focal plane of a dielectric lens. Individual antenna center positions correspond to different beam directions for radiation incident on the lens, and the antenna center positions are in accordance with the Rayleigh resolved spot criterion. The dimensions, dielectric properties and relative positioning of the lens and substrate are such as to provide for the antennas to couple predominantly to radiation passing through the lens. The substrate thickness may lie between the lens and antenna array, or alternatively the array may lie between the substrtate and lens. In the latter case, the lens is of higher dielectric constant material than the substrate, at least in the lens region adjacent the array. The sensor of the invention provides a robust, low cost means of monitoring radiation directionally without requiring scanning means.

Claims

1. An electromagnetic radiation sensor of modular construction including:

(a) a substrate module in the form of a sheet and retaining;

(i) an array of antennas each having at least two dipole limbs supported by a substrate sheet surface,

(ii) a respective mixing means for each antenna, the mixing means comprising at least one high frequency mixer diode connected between two antenna limbs,

(iii) means for relaying low frequency signals developed by the mixing means to sensor outputs,

(b) a dielectric lens module assembled together with and closely adjacent to the substrate to transmit radiation incident on the lens to the antenna array, the lens being configured such that the antenna center positions in the array correspond to differing beam directions for radiation incident on the lens, and the lens-antenna array spacing and the lens and substrate dimensions and dielectric properties being in combination such as to provide for each antenna to couple predominantly to radiation passing through the lens.

2. A sensor according to claim 1 wherein the spacing of neigbouring antenna centres in the array is substantially equal to the Rayleigh resolved spot separation defined by the lens F-number and dielectric constant together with the sensor operating wavelength, and where the antenna array is located within the depth of focus of the lens so that each antenna is disposed to receive a respective radiation beam.

3. A senor according to claim 1 wherein the lens is arranged to couple radiation to the antenna array through the substrate thickness, the lens and substrate having dielectric constants with similar values.

4. A sensor according to claim 3 wherein the substrate, antenna array, mixing means and low frequency relaying means are formed in combination as an integrated circuit.

5. A sensor according to claim 4 including a low frequency amplifier integrated in the substrate and arranged to amplify signals received via the low frequency relaying means.

6. A sensor according to claim 1 wherein t he lens has a lower dielectric constant than that of the substrate and is arranged to couple radiation to the antenna array through the substrate thickness, and the substrate conductivity and thickness are arranged in combination to inhibit radiation trapping.

7. A sensor according to claim 1 wherein the lens has a dielectric constant larger than that of the substrate and the antenna array is sandwiched between the lens and substrate.

8. A sensor according to claim 1 including means for relaying a local oscillator signal to each antenna of the array.

9. A sensor according to claim 1 wherein each antenna dipole is crossed by a second-two-limb dipole having at least one longitudinally divided limb providing the said low frequency output signal relaying means.

10. A sensor according to claim 9 wherein the mixing means comprises mixer diodes connected between adjacent limbs of different dipoles, the diodes being arranged to provide any one of balanced mixing and coherent mixing.

11. A sensor according to claim 10 including respective limiter diodes shunting respective mixer diodes.

12. A sensor according to claim 10 wherein each dipole antenna includes a respective transmission line section connecting pairs of mixer diodes.