Modulated backscatter microstrip patch antenna

• US 5,825,329 A
• Filed: 07/23/1996
• Issued: 10/20/1998
• Est. Priority Date: 10/04/1993
• Status: Expired due to Fees

• Current Assignee: TC License Limited
• Original Assignee: Amtech Corporation (McClarin Plastics LLC)
• Inventors: Carrender, Curtis L., Veghte, Richard L.
• Primary Examiner(s): Le, Hoanganh T.
• Application Number:
  US08/687,089
• Time in Patent Office: 819 Days
• Field of Search: 343/700 MS, 343/742, 343/867, 343/876, 343/895, 340/572
• US Class Current: 343/700.0MS
• CPC Class Codes: G01S 13/756 using a signal generator for modifying the reflectivity of the reflector G01S13/758 takes precedence
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 19/07786 the antenna being of the HF type, such as a dipole
• CPC Class Codes: G06K 7/10316 using at least one antenna particularly designed for interrogating the wireless record carriers antennas in general H01Q1/22
• CPC Class Codes: G06K 7/10346 the antenna being of the far field type, e.g. HF types or dipoles
• CPC Class Codes: H01Q 1/3233 particular used as part of a sensor or in a security system, e.g. for automotive radar, navigation systems
• 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 21/29 Combinations of different interacting antenna units for giving a desired directional characteristic H01Q25/00 takes precedence
• CPC Class Codes: H01Q 21/293 one unit or more being an array of identical aerial elements adaptive arrays H01Q3/2605
• CPC Class Codes: H01Q 3/44 varying the electric or magnetic characteristics of reflecting, refracting, or diffracting devices associated with the radiating element
• CPC Class Codes: H01Q 3/46 Active lenses or reflecting arrays
• CPC Class Codes: H01Q 9/0407 Substantially flat resonant element parallel to ground plane, e.g. patch antenna dipole H01Q9/285; monopole H01Q9/40
• CPC Class Codes: H01Q 9/0442 with particular tuning means

Abstract

The invention provides a microstrip patch antenna for emitting backscatter-modulated signals in response to a received signal. The antenna has two segments that are connected together by a switch. When the switch is ON, the antenna is a full wave length antenna with its two segments out-of-phase with each other, thus producing minimal backscatter. When the switch is OFF, the two segments of the antenna act in concert with each other to produce a backscatter-modulated signal. Multiple pairs of such antennas can be connected together to make a single antenna with increased signal power.

Claims

1. A microstrip patch antenna for emitting backscatter-modulated signals at a fundamental frequency in response to a received signal from a reader, said antenna comprising:

two one-half wavelength segments, at least one of which has an input line for receiving an external signal;

a switch connecting each of the two one-half wavelength segments together at one end and having a closed position and an open position;

the two segments of the antenna being out-of-phase with each other when the switch is in the closed position, whereby no significant signal is reflected back to the reader, and the two segments of the antenna acting in concert when the switch is in the open position, thereby producing a backscatter-modulated signal at the fundamental frequency; and

a switching circuit for actuating the switch between the open position and the closed position in response to the external signal.

2. A microstrip patch antenna according to claim 1 wherein said external signal is derived from the received signal.

3. A microstrip patch antenna according to claim 1 wherein the switching circuit contains a memory for holding received data, and wherein one of the one-half wavelength segments has an input line for writing data into the memory.

4. A microstrip patch antenna according to claim 3 wherein the external signal is for writing data into the memory.

5. A microstrip patch antenna according to claim 1 wherein both segments have input lines for receiving an external signal.

6. A microstrip patch antenna according to claim 5 wherein each of the input lines is located on one of the segments on a side opposite the switch.

7. A microstrip patch antenna according to claim 5 wherein each of the input lines is located in one of the segments on a side opposite the switch.

8. A microstrip patch antenna according to claim 1 wherein the input line is located on a side of one segment opposite the switch.

9. A microstrip patch antenna according to claim 1 wherein each of the segments has circular polarization.

10. A microstrip patch antenna assembly, comprising:

a first segment;

a second segment;

a switch coupled to the first segment and to the second segment, the switch having an open position and a closed position;

wherein one of the first segment and the second segment includes an input line for receiving an external signal;

wherein the first segment is coupled to the second segment when the switch is in the closed position and the first segment is electrically isolated from the second segment when the switch is in the open position; and

wherein the microstrip patch antenna assembly generates a backscatter pattern comprising a series of nulls and peaks in response to a received signal and according to the closing and opening of the switch.

11. A microstrip patch antenna assembly according to claim 10 wherein the first segment and the second segment are each one-half wavelength segments connected together at one end by the switch.

12. A microstrip patch antenna assembly according to claim 10 wherein the switch opens and closes in response to an external signal.

13. A microstrip patch antenna assembly according to claim 10 wherein the external signal is incorporated in the received signal.

14. A microstrip patch antenna assembly according to claim 10 further comprising a temporary memory for storing data from the received signal.

15. A microstrip patch antenna assembly according to claim 10 wherein both the first segment and the second segment have separate input lines for receiving an external signal.

16. A microstrip patch antenna assembly according to claim 10 wherein each of the first segment and second segment has circular polarization.