Fixed-frequency beam-steerable leaky-wave microstrip antenna

• US 7,002,517 B2
• Filed: 06/20/2003
• Issued: 02/21/2006
• Est. Priority Date: 06/20/2003
• Status: Expired due to Fees

• Current Assignee: Anritsu Corporation
• Original Assignee: Anritsu Corporation
• Inventors: Noujeim, Karam Michael
• Primary Examiner(s): Ho, Tan
• Application Number:
  US10/600,293
• Publication Number:
  US 20050012667A1
• Time in Patent Office: 977 Days
• Field of Search: 343/700.MS, 343/745, 343/749, 343/754, 343/757, 343/824, 343/860
• US Class Current: 343/700.0MS
• 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 13/20 Non-resonant leaky-waveguide or transmission-line antennas; Equivalent structures causing radiation along the transmission path of a guided wave
• CPC Class Codes: H01Q 13/206 Microstrip transmission line antennas
• CPC Class Codes: H01Q 23/00 Antennas with active circuits or circuit elements integrated within them or attached to them

Abstract

A fixed frequency continuously beam-steerable leaky-wave antenna in microstrip is disclosed. The antenna'"'"'s radiating strips are loaded with identical shunt-mounted variable-reactance elements, resulting in low reverse-bias-voltage requirements. By varying the reverse-bias voltage across the variable-reactance elements, the main beam of the antenna may be scanned continuously at fixed frequency. The antenna may consist of an array of radiating strips, wherein each strip includes a variable-reactance element. Changing the element'"'"'s reactance value has a similar effect as changing the length of the radiating strips. This is accompanied by a change in the phase velocity of the electromagnetic wave traveling along the antenna, and results in continuous fixed-frequency main-beam steering. Alternatively, the antenna may consist of two long radiating strips separated by a small gap, wherein identical variable-reactance elements are mounted in shunt across the gap at regular intervals. A continuous change in the reactance value has a similar effect as changing continuously the width of the radiating strips. This results in a continuous change in the phase velocity of the electromagnetic wave traveling along the antenna, thereby achieving continuous fixed-frequency main-beam steering.

Claims

1. A fixed-frequency beam-steerable leaky-wave microstrip antenna comprising:

a grounded element;

a dielectric coupled to said grounded element; and

conducting traces coupled to the dielectric, the conducing traces including;

a pair of non-radiating conductive elements; and

a plurality of radiating strips, each of the radiating strips connected between the pair of non-radiating conductive elements, each of said plurality of radiating strips including a center-loaded varying reactance element.

2. The fixed frequency beam steerable leaky wave microstrip antenna of claim 1 wherein each of the varying reactance elements is a variable capacitor.

3. The fixed frequency beam steerable leaky wave microstrip antenna of claim 1 wherein each of the varying reactance elements is a varactor diode.

4. The fixed frequency beam steerable leaky wave microstrip antenna of claim 1 wherein the pair of non-radiating conductive elements includes:

a driving port having a first and second driving end, the first driving end configured to receive a first driving signal, the second driving end configured to receive a second driving signal, the first signal being 180 degrees-out-of-phase with the second driving signal;

a terminating port having a first terminating end and a second terminating end, the first terminating end connected to a first resistive load, the second terminating end connected to a second terminating load.

5. The fixed frequency beam steerable leaky wave microstrip antenna of claim 4 further comprising:

a biasing DC voltage source coupled between the first terminating end and the second terminating end.

6. The fixed frequency beam steerable leaky wave microstrip antenna of claim 1 wherein each of the radiating strips has the same width, length and inter-strip spacing.

7. A fixed frequency beam steerable leaky wave microstrip antenna, comprising:

a grounded element;

a dielectric coupled to said grounded element; and

a pair of radiating strips coupled to said dielectric, the pair of radiating strips separated by a generally uniform gap and including;

variable reactance elements mounted in shunt across the gap,

wherein the pair of radiating strips includes;

a driving port having a first and second driving end, the first driving end configured to receive a first driving signal, the second driving end configured to receive a second driving signal, the first signal being 180 degrees-out-of-phase with the second driving signal;

a terminating port having a first terminating end and a second terminating end, the first terminating end connected to a first resistive load, the second terminating end connected to a second terminating load.

8. A fixed-frequency beam-steerable leaky-wave microstrip antenna comprising:

a grounded element;

a dielectric coupled to said grounded element; and

a pair of radiating strips coupled to said dielectric, the pair of radiating strips separated by a generally uniform gap and including;

variable reactance elements mounted in shunt across the gap, wherein the pair of

radiating strips includes;

a driving port having a first and second driving end, the first driving end configured to receive a first driving signal, the second driving end configured to receive a second driving signal, the first signal being 180 degrees-out-of-phase with the second driving signal;

a terminating port having a first terminating end and a second terminating end, the first terminating end connected to a first resistive load, the second terminating end connected to a second terminating load;

a biasing DC voltage source coupled between the first terminating end and the second terminating end.

9. A method for generating a fixed-frequency beam-steerable leaky wave from a leaky wave microstrip antenna, comprising:

providing conducting traces coupled to a dielectric, the dielectric coupled to a grounded element, the conducting traces including;

a pair of non-radiating conducting strips; and

a plurality of radiating strips, the plurality of radiating strips coupled between the pair of non-radiating conducting strips, each of said plurality of radiating strips including;

a variable reactive-element having a reactance value;

driving the microstrip with a 180-degree hybrid fixed-frequency signal, the signal configured to excite the micro strip in a first higher order mode and configure the leaky wave antenna to transmit a beam-steerable leaky wave;

varying the variable reactive-element reactance value to provide continuous fixed frequency main beam steering.

10. The method of claim 9 wherein each of the variable reactive-elements is center loaded on each of the plurality of radiating strips.

11. The method of claim 9 wherein each of the variable reactance-elements is a varactor diode.

12. The method of claim 9 wherein each of the plurality of radiating strips is configured to have a substantially similar length, width and inter-strip spacing.

13. A method for generating a fixed-frequency beam-steerable leaky wave from a leaky-wave microstrip antenna, comprising:

providing conducting traces coupled to a dielectric, the dielectric coupled to a grounded element, the conducting traces including;

a pair of radiating strips, the pair of radiating strips separated by a generally uniform gap and including;

variable reactance-elements having a reactance value and mounted in shunt

across the gap;

driving the radiating strips with a 180-degree-hybrid fixed-frequency signal, the signal configured to excite the micro strip in a first higher order mode and configure the leaky wave antenna to transmit a beam steerable leaky wave;

varying the variable reactance-element reactance value to provide continuous fixed-frequency main-beam steering.

14. The method of claim 13 wherein each of the variable reactance-elements is a varactor diode.