WO2014140791A1

WO2014140791A1 - Electrically steerable passive array radiator antenna with reconfigurable radiation pattern and method of configuring the same

Info

Publication number: WO2014140791A1
Application number: PCT/IB2014/000570
Authority: WO
Inventors: Shaowei LIAO; Wei Ni; Wei Wang; Gang Shen
Original assignee: Alcatel Lucent
Priority date: 2013-03-13
Filing date: 2014-03-07
Publication date: 2014-09-18
Also published as: EP2973867A1; CN104051850A

Abstract

The present application relates to an ESPAR antenna including a ground plane; a drive unit, located on the ground plane and oriented outward from the ground plane; and a parasitic element, located around the drive unit, comprising a control circuit configured to control electrical length between the parasitic element and the ground plane. The application further provides a method for configuring an antenna including scanning beams of the antenna in various possible operating states; comparing results of the scanning with predetermined radiation performance criteria and selecting one of the scanning results which most satisfies the predetermined radiation performance criteria; configuring the antenna based on the selected scanning result; and measuring radiation performance of the antenna, and repeating the foregoing operations when the radiation performance measured is below the predetermined radiation performance criteria.

Description

Electrically Steerable Passive Array Radiator Antenna with Reconfigurable Radiation Pattern and Method of

Configuring the Same Field

The present disclosure generally relates to an antenna technology and particularly to an Electrically Steerable Passive Array Radiator (ESPAR) antenna with a reconfigurable radiation pattern and method of configuring the same.

Background

A reconfigurable antenna refers to an antenna of which electrical characteristics including radiation pattern, polarization or operating frequency can be reconfigured or adjusted. Since wireless communication requires adaptability to a variety of different environments, antennas with a reconfigurable radiation pattern can be adopted in many situations. ESPAR antennas are one of such antennas. Fig.1 (a) is a perspective view of a conventional ESPAR antenna 100. In addition to a drive unit 102 and a ground plane 106, the ESPAR antenna 100 includes several parasitic elements 104 surrounding the drive unit 102. Fig.1(b) illustrates a typical control circuit of a parasitic element 104 in the conventional ESPAR antenna 100. Under the control of a control signal S I , the control circuit, by using variable voltage source 112, is configured to generate various direct-current voltages, to thereby adjust the equivalent capacitance value of variable capacitor 114. Accordingly, the ESPAR antenna 100 may generate various radiation patterns.

Summary

One of the problems of conventional ESPAR antennas is that variable voltage sources and variable capacitors are required to change the electromagnetic characteristics of parasitic elements, which leads to complex structure and high cost of conventional ESPAR antennas.

In view of the foregoing problem, it is desirable to provide an ESPAR antenna with simpler structure and lower cost.

One aspect of the present application discloses an antenna including: a ground plane; a drive unit, located on the ground plane and oriented outward from the ground plane; and a parasitic element, located around the drive unit, comprising a control circuit configured to control electrical length between the parasitic element and the ground plane.

Particularly, the control circuit comprises: a first switch, configured to couple the parasitic element with the ground plane over a first electrical length under control of a first signal; and a second switch configured to couple the parasitic element with the ground plane over a second electrical length under control of a second signal; and wherein the first electrical length is different from the second electrical length.

Particularly, the parasitic element further comprises a metal rod oriented outward from the ground plane; the control circuit further comprises a transmission line coupled between the metal rod and the second switch; the first switch is located between the metal rod and the ground plane; the first electrical length is a length of the metal rod; and the second electrical length is a sum of lengths of the metal rod and the transmission line.

Particularly, the transmission line is a co-polar waveguide or other planar transmission line embedded in the ground plane and located around the metal rod.

Particularly, the parasitic element further comprises an isolation stripe between the transmission line and the ground plane, and the first and second switches are located in the isolation stripe.

Particularly, the isolation stripe is a slot around the parasitic element or a stripe made of insulating material(s). Particularly, when the first switch is closed and the second switch is open, the parasitic element operates in a director mode; and when the first switch is open and the second switch is closed, the parasitic element operates in a reflector mode.

Particularly, the switches include PIN diode switches, MOSFET switches, Micro-Electronic-Mechanical (MEMS) Radio Frequency (RF) switches or other radio frequency switches.

Particularly, the antenna further comprises a number of the parasitic elements, each of which includes at least one of the control circuits configured to control electrical length between a corresponding one of the parasitic elements and the ground plane.

Particularly, the ground plane is in a circular shape and the parasitic elements are distributed along a radius direction of the ground plane.

In the embodiments of the application, the radiation pattern of the ESPAR antenna may be directly adjusted by using a simple digital circuit control signal. Such an antenna has a simpler structure, lower manufacturing cost and has higher reliability compared with the conventional ones.

Another aspect of the application discloses a method for configuring the foregoing antenna including scanning beams of the antenna in all possible operating states; comparing results of the scanning with predetermined radiation performance criteria and selecting one of the scanning results which most satisfies the predetermined radiation performance criteria; configuring the antenna based on the selected scanning result; and measuring radiation performance of the antenna, and repeating the foregoing operations when the radiation performance measured is below the predetermined radiation performance criteria.

Particularly, said configuring the antenna comprises adjusting states of switches in control circuits of parasitic elements based on the selected scanning result.

With the method of the application, a user is enabled to adjust the configuration of the ESPAR antenna flexibly in response to various demands as well as changes in the application environment.

Brief description of drawings

Fig.1 (a) is a perspective view of a conventional ESPAR antenna;

Fig.1 (b) is a typical control circuit of a parasitic element in the conventional ESPAR antenna;

Fig.2(a) is a perspective view of an ESPAR antenna according to one embodiment of the present application;

Fig.2(b) is an enlarged view of a parasitic element in the ESPAR antenna illustrated in Fig.2(a);

Fig.2(c) illustrates a control circuit of the parasitic element in the ESPAR antenna illustrated in Fig.2(a);

Fig.2(d) is a top view of the ESPAR antenna illustrated in Fig.2(a); Fig.3 shows radiation patterns of the ESPAR antenna according to one embodiment of the present application; and

Fig.4 is a flow chart of a method for configuring the ESPAR antenna according to one embodiment of the present application. Detailed description

The making and use of embodiments of the present application is discussed below in details. However it shall be appreciated that the application is intended to provide numerous feasible innovative concepts which can be embodied in various particular environments. The particular embodiments discussed later are merely illustrative of particular modes of making and using the invention but not intended to limit the scope of the application.

Fig.2(a) illustrates a perspective view of an ESPAR antenna 200 according to an embodiment of the present application. The antenna 200 includes a drive unit 202 and a ground plane 206. The ground plane may be in the shape of a circular, and may be surrounded by an electrically conductive sleeve 208. One or more parasitic elements 204 may be distributed around the drive unit 202, and the plurality of parasitic elements 204 can be structurally identical.

As illustrated in Fig.2(b), each parasitic element 204 may include a metal rod 212 and a control circuit. The control circuit includes a transmission line 214, switches 216 and 218, and an isolation stripe 217 between the transmission line 214 and the ground plane 206. In an embodiment of the application, the transmission line 214 may be embedded in the ground plane 206 and extend along radius direction of the ground plane 206. The transmission line 214 may be made of a co-planar waveguide, a micro-stripe line or other planar transmission lines. The isolation stripe 217 may be a slot surrounding the transmission line 214 or be made of any insulating material well known to those skilled in the art.

According to an embodiment of the invention, the switches 216 and 218 may be PIN diode switches as illustrated. In another embodiment, the switches 216 and 218 may alternatively be Micro-Electronic-Mechanical (MEMS) Radio Frequency (RF) switches or MOS transistors or other radio frequency switching devices.

Fig.2(c) is a circuit diagram of a control circuit of a parasitic element 204. Specifically a first branch includes a resistor Rl and an inductor LI coupled in series, and optionally an amplifier 211 coupled in series therewith. One end of the inductor LI may be coupled with the metal rod 212, and with one end of the transmission line 214 and the switch 216. A second branch includes a resistor R2 and an inductor L2 coupled in series, and optionally an amplifier 213 coupled in series therewith. One end of the inductor L2 may be coupled with one end of the switch 218, and with the other end of the transmission line 214 through a capacitor C.

In a first scenario, signals Sa and Sb are inputted to close the switch 216 and open the switch 218. Thus the metal rod 212 may be coupled directly to the ground level through the switch 216. In this scenario, according to an embodiment of the application, the electrical length between the parasitic elements 204 and the ground level may be about the length of the metal rod 212 which is slightly shorter than a 1/4 wavelength. Therefore, the parasitic elements 204 may operate in a director mode.

In a second scenario, another set of signals Sa and Sb are inputted to open the switch 216 and close the switch 218. Thus the metal rod 212 may be coupled to the ground level through the transmission line 214 and the switch 218. The capacitor C may be configured to isolate the influence of the direct-current control signal Sa upon the switch 218, and the capacitor C may have no influence upon alternating-current signals flowing through the metal rod 212. In this scenario, according to an embodiment of the application, the electrical length between the parasitic elements 204 and the ground level may be about the sum of the length of the metal rod 212 and the length of the transmission line 214, which may be slightly longer than a 1/4 wavelength, therefore the parasitic elements 204 may operate in a reflector mode.

According to an embodiment of the application, the first scenario may apply when both the switches 216 and 218 are closed.

Thus, the different state combinations of the switches 216 and 218 may provide the parasitic elements 204 different electromagnetic characteristics, which may have different influence upon the directivity of the antenna 200.

It shall be noted that the parasitic elements 204 including two switches 206 and 208 is just an example. In other embodiments of the present application, the parasitic elements may include more switches. By controlling the electrical length between the parasitic elements 204 and the ground level, for example, coupling the parasitic elements 204 to the ground level through a portion of the transmission line 214, the characteristics of the parasitic elements 204 may be controlled, and thereby the radiation pattern of the antenna 200 may be adjusted.

Fig.2(d) is a top view of the ESPAR antenna 200 according to an embodiment of the application. In the example illustrated in Fig.2, 12 parasitic elements 204 may be grouped into 6 sets, and are uniformly distributed on the ground plane 206 along the radius direction at an interval of 60°, where each parasitic element may include two switches A and B. As described above, there may be three valid states for each parasitic element, therefore there may be 3 12 different combinations of states for the antenna 200 illustrated in Fig.2(d). Table 1 lists only a part of these combinations.

Fig.3 illustrates radiation patterns of the antenna 200 corresponding to the combinations listed in Table 1. As illustrated in Fig.3(a)-(d), in combinations 0-3, the antenna 200 can generate a unidirectional beam with different beam width and beam direction. As illustrated in Fig.3(e)-(g), in combinations 4-6, the radiation patterns of the antenna 200 may include two primary beams with different angle intervals. As illustrated in Fig.2(d), the adjacent groups of the parasitic elements are rotationally symmetric with an interval of 60°, therefore the radiation pattern of the antenna 200 may also has a corresponding symmetric distribution.

In the combinations listed in Table 1 , all the Voltage Standing Wave Ratios (VSWRs) of the antenna 200 are below 5, and even some of them are below 3. For example, in combination 1, the antenna 200 may have a gain up to 8.8dB. According to another embodiment of the application, an impendence matching network can further configured externally for better matching.

Of course, the distribution in Fig.2(d) described here is merely illustrative. Various ESPAR antennas may be provided with different distributions of parasitic elements.

Fig.4 illustrates a flow chart of a method for configuring the ESPAR antenna in accordance with another embodiment of the application. In step 402, a base station may scan beams of the antenna 200 operated in various possible operating states. Such scan may be a 360° scan of beams throughout the plane covered by the antenna 200. The various possible operating states may be decided by different state combinations of the switches in the parasitic elements. In step 404, the base station may receive the scan results and compare the results with predetermined criteria of radiation characteristics. The radiation characteristics of the antenna may include a radiation pattern, polarization, an operating frequency, power, a signal to noise ratio, etc. In step 406, one or more combinations satisfying the predetermined radiation characteristics criteria may be located according to the results derived in the step 404. In step 408, the antenna may be configured according to the one or more combinations located. According to an embodiment of the application, the configuration may be implemented by adjusting states of the switches in the antenna. In step 410, radiation characteristics of the antenna may be measured, and if the measured characteristics are below the predetermined criteria, then the flow may return to the step 402 and restart scanning; otherwise, the antenna 200 may be maintained in the configuration.

Those skilled in the art can readily appreciate that the material and the method can be varied without departing the scope of the invention. It shall be further appreciated that the invention provides numerous applicable innovative concepts in addition to the particular context where the embodiments are described. Correspondingly the appended claims are intended to encompass in their scope such processes, machines, articles of manufacturing, combinations of sustenance, means, methods or steps.

Claims

1. An antenna, comprising:

a ground plane;

a drive unit, located on the ground plane and oriented outward from the ground plane; and

a parasitic element, located around the drive unit, comprising a control circuit configured to control electrical length between the parasitic element and the ground plane.

2. The antenna according to claim 1 , wherein the control circuit comprises:

a first switch, configured to couple the parasitic element with the ground plane over a first electrical length under control of a first signal; and a second switch configured to couple the parasitic element with the ground plane over a second electrical length under control of a second signal; and

wherein the first electrical length is different from the second electrical length.

3. The antenna according to claim 2, wherein the parasitic element further comprises a metal rod oriented outward from the ground plane; the control circuit further comprises a transmission line coupled between the metal rod and the second switch; the first switch is located between the metal rod and the ground plane; the first electrical length is a length of the metal rod; and the second electrical length is a sum of lengths of the metal rod and the transmission line.

4. The antenna according to claim 3, wherein the transmission line is a co-polar waveguide or other planar transmission line embedded in the ground plane and located around the metal rod.

5. The antenna according to claim 4, wherein the parasitic element further comprises an isolation stripe between the transmission line and the ground plane, and the first and second switches are located in the isolation stripe.

6. The antenna according to claim 5, wherein the isolation stripe is a slot around the parasitic element or is made of insulating material(s).

7. The antenna according to claim 2, wherein when the first switch is closed and the second switch is open, the parasitic element operates in a director mode; and when the first switch is open and the second switch is closed, the parasitic element operates in a reflector mode.

8. The antenna according to claim 2, wherein the switches include PIN diode switches, MOSFET switches, Micro-Electronic-Mechanical (MEMS) Radio Frequency (RF) switches or other radio frequency switches.

9. The antenna according to any one of claims 1-8, further comprising a number of the parasitic elements, each of which includes at least one of the control circuits configured to control electrical length between a corresponding one of the parasitic elements and the ground plane.

10. The antenna according to claim 9, wherein the ground plane is in a circular shape and the parasitic elements are distributed along a radius direction of the ground plane.

11. A method for configuring an antenna of claim 9, the method comprising:

scanning beams of the antenna in all possible operating states;

comparing results of the scanning with predetermined radiation performance criteria and selecting one of the scanning results which most satisfies the predetermined radiation performance criteria;

configuring the antenna based on the selected scanning result; and measuring radiation performance of the antenna, and repeating the foregoing operations when the radiation performance measured is below the predetermined radiation performance criteria.

12. The method according to claim 11, wherein said configuring the antenna comprises adjusting closed or open states of switches in control circuits of parasitic elements based on the selected scanning result.