Electrically small, source direction resolving antennas

• US 8,362,956 B2
• Filed: 11/18/2010
• Issued: 01/29/2013
• Est. Priority Date: 11/18/2010
• Status: Active Grant

• Current Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Original Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Inventors: Behdad, Nader, Al-Joumayly, Mudar Ala
• Primary Examiner(s): Phan, Dao
• Application Number:
  US12/949,276
• Publication Number:
  US 20120127035A1
• Time in Patent Office: 803 Days
• Field of Search: 342/434, 342/442, 342/445, 342/448
• US Class Current: 342/442
• CPC Class Codes: G01S 3/48 the waves arriving at the antennas being continuous or intermittent and the phase difference of signals derived therefrom being measured
• CPC Class Codes: H01Q 3/36 with variable phase-shifters

Abstract

An electrically small receiver system is provided. The receiver system includes a plurality of antennas and a signal processing circuit. The plurality of antennas includes a first antenna configured to receive a first signal and a second antenna configured to receive a second signal. The signal processing circuit includes a first resonant loop and a second resonant loop. The first resonant loop is mounted to receive the first signal from the first antenna. The second resonant loop is mounted to receive the second signal from the second antenna. The first resonant loop and the second resonant loop are coupled such that the first output signal and the second output signal are generated as a function of the first signal and the second signal. A phase difference between the first output signal and the second output signal is greater than a phase difference between the first signal and the second signal.

Claims

1. A receiver system comprising:

a plurality of antennas comprising

a first antenna configured to receive a first signal; and

a second antenna configured to receive a second signal; and

a signal processing circuit comprising

a first resonant loop mounted to receive the first signal from the first antenna; and

a second resonant loop mounted to receive the second signal from the second antenna, wherein the first resonant loop and the second resonant loop are coupled to generate a first output signal and a second output signal that are a function of the first signal and the second signal, and further wherein a first phase difference between the first output signal and the second output signal is greater than a second phase difference between the first signal and the second signal.

2. The receiver system of claim 1, wherein the first resonant loop and the second resonant loop are coupled by a capacitor mounted in parallel with the first resonant loop and the second resonant loop.

3. The receiver system of claim 2, wherein the capacitor is a varactor.

4. The receiver system of claim 3, wherein adjustment of a capacitance of the varactor changes a response of the first phase difference as a function of an angle of incidence of a source of the first signal relative to a boresight of the plurality of antennas.

5. The receiver system of claim 4, wherein the source of the first signal is the same as a second source of the second signal.

6. The receiver system of claim 2, wherein the capacitor generates a third output signal.

7. The receiver system of claim 1, wherein the first resonant loop comprises a first resistor, a first inductor, and a first capacitor connected in series.

8. The receiver system of claim 7, wherein the first resistor includes a radiation resistance of the first antenna.

9. The receiver system of claim 7, wherein the first resistor includes a resistance of a transmission line connecting the first antenna with the signal processing circuit.

10. The receiver system of claim 7, wherein the first capacitor is a reactive part of an input impedance of the first antenna.

11. The receiver system of claim 7, wherein the second resonant loop comprises a second resistor, a second inductor, and a second capacitor connected in series.

12. The receiver system of claim 11, wherein the first inductor and the second inductor have approximately the same value of inductance.

13. The receiver system of claim 1, wherein the first resonant loop comprises a resistor, an inductor, and a capacitor connected in parallel.

14. The receiver system of claim 1, further comprising a phase shifter electrically connected to receive the second signal from the second antenna to form a phase-shifted second signal, wherein the second resonant loop receives the phase-shifted second signal.

15. The receiver system of claim 14, wherein the first resonant loop and the second resonant loop are coupled by a capacitor mounted in parallel with the first resonant loop and the second resonant loop to generate a third output signal.

16. The receiver system of claim 15, wherein the plurality of antennas further comprise a third antenna configured to receive a third signal, and the signal processing circuit further comprises:

a third resonant loop mounted to receive the second signal from the second antenna and to generate a fourth output signal;

a fourth resonant loop mounted to receive the third signal from the third antenna and to generate a fifth output signal; and

a second capacitor mounted in parallel with the third resonant loop and the fourth resonant loop to generate a sixth output signal.

17. The receiver system of claim 16, further comprising:

a first amplitude detector configured to receive the first output signal;

a second amplitude detector configured to receive the third output signal;

a first comparator configured to receive the amplitude detected first output signal and the amplitude detected third output signal;

a third amplitude detector configured to receive the fourth output signal;

a fourth amplitude detector configured to receive the sixth output signal; and

a second comparator configured to receive the amplitude detected fourth output signal and the amplitude detected sixth output signal.

18. The receiver system of claim 15, further comprising:

a first amplitude detector configured to receive the first output signal;

a second amplitude detector configured to receive the third output signal; and

a comparator configured to receive the amplitude detected first output signal and the amplitude detected third output signal.

19. The receiver system of claim 1, wherein the plurality of antennas further comprise a third antenna configured to receive a third signal, and the signal processing circuit further comprises:

a third resonant loop mounted to receive the second signal from the second antenna and to generate a third output signal; and

a fourth resonant loop mounted to receive the third signal from the third antenna and to generate a fourth output signal,

wherein the third resonant loop and the fourth resonant loop are coupled, and further wherein a third phase difference between the third output signal and the fourth output signal is greater than a fourth phase difference between the second signal and the third signal.

20. The receiver system of claim 1, wherein a spacing between the first antenna and the second antenna is less than or equal to λ

₀/π

, where λ

₀=c/f₀, where c is the speed of light and f₀ is a carrier frequency of the first signal.