Antenna phase modulator

• US 20040214534A1
• Filed: 04/28/2003
• Published: 10/28/2004
• Est. Priority Date: 04/28/2003
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Carlson, Dennis
• Granted Patent: US 7,035,584 B2
• Time in Patent Office: Days
• US Class Current: 455/121
• CPC Class Codes: H01Q 9/0435 using two feed points
• CPC Class Codes: H01Q 9/045 with particular feeding means for circular polarisation H01Q9/0428
• CPC Class Codes: H03C 3/40 using two signal paths the outputs of which have a predetermined phase difference and at least one output being amplitude-modulated
• CPC Class Codes: H04B 1/0483 Transmitters with multiple parallel paths

Abstract

A phase modulator comprised of a plurality of circuit paths operates to receive a data signal and a radio frequency carrier signal and to couple the radio frequency carrier signal into an antenna at a feedpoint associated with a circuit path, whereby the electric field vector phase of the emitted radio frequency signal is determined by the data state of the received data signal. The circuit has at least one circuit path, which is determined by the data state of the input data signal, to couple the radio frequency carrier signal to the antenna feedpoint to adjust the phase.

Claims

1. A radio frequency communication device, comprising:

an antenna including a plurality of spaced apart feedpoints; and

a circuit including a plurality of circuit paths operable to receive a data signal and a radio frequency carrier signal, each of the circuit paths operably coupled to one of the feedpoints, wherein the circuit routes the radio frequency carrier signal along the circuit paths based on a data state of the data signal, and wherein the electric field vector phase of the radio frequency signal emitted from the antenna is adjusted based on a position of the feedpoint associated with the circuit path through which the radio frequency carrier signal is routed.

2. The radio frequency communication device of claim 1, wherein the antenna is selected from the group consisting of a probe fed circular patch antenna having a center point on the antenna connected to the ground plane through a resistor-capacitor circuit, a probe fed square patch antenna having a center point on the antenna connected to the ground plane through a resistor-capacitor circuit and a probe fed rectangular patch antenna having a center point on the antenna connected to ground through a resistor-capacitor circuit.

3. The radio frequency communication device of claim 1, wherein the data signal is unipolar and comprises a first and a second data signal, the second data signal comprising the complement of the first data signal, and wherein the first data signal allows the radio frequency carrier signal to travel a first circuit path and the second data signal prevents the radio frequency carrier signal from traveling a second circuit path.

4. The radio frequency communication device of claim 3, wherein a change in the data state of the data signal switches the circuit path the radio frequency carrier signal travels, wherein, upon switching, the first data signal prevents the radio frequency carrier signal from traveling the first circuit path and the second data signal allows the radio frequency carrier signal to travel the second circuit path.

5. The radio frequency communication device of claim 4, wherein the first and second circuit paths direct the radio frequency carrier signal into an operably positioned first or second feedpoint on the antenna, wherein the first feedpoint causes the antenna to emit a radio frequency signal having a first electric field vector phase and the second feedpoint causes the antenna to emit a radio frequency signal having a second electric field vector phase, wherein the first and second electric field vector phases are 180 degrees out of phase.

6. The radio frequency communication device of claim 1, wherein the data signal is unipolar and comprises a first and second data stream, the first data stream comprising a first and a second data signal, the second data signal comprising the complement of the first data signal, and the second data stream comprising a third and fourth data signal the fourth data signal comprising the complement of the third data signal, wherein the first data signal allows the radio frequency carrier signal to travel a first circuit path and the second data signal prevents the radio frequency carrier signal from traveling a second circuit path, and wherein the third data signal allows the radio frequency carrier signal to travel a third circuit path and the fourth data signal prevents the radio frequency carrier signal from traveling a fourth circuit path.

7. The radio frequency communication device of claim 6, wherein a change in the data state of the first data signal prevents the radio frequency carrier signal from traveling the first circuit path, wherein the second data signal allows the radio frequency carrier signal to travel the second circuit path, and wherein a change in the data state of the third data signal prevents the radio frequency carrier signal from traveling the third circuit path, wherein the fourth data signal allows the radio frequency carrier signal to travel the fourth circuit path.

8. The radio frequency communication device of claim 7, wherein the first or second circuit path and the third or fourth circuit path simultaneously direct the radio frequency carrier signal into operably positioned first and second feedpoints to emit from the antenna a radio frequency signal having one of four electric field vector phases based on the data state of the first and third data signals and wherein the four electric field vector phases are 90°

out of phase with each other.

9. The radio frequency communication device of claim 7, wherein the first data stream is identical to the second data stream, wherein the first and second circuit paths contain quarter wave transmission lines, and wherein the first or second circuit path and the third or fourth circuit path simultaneously direct the radio frequency carrier signal into operably positioned first and second feedpoints to emit from the antenna a radio frequency signal having a first circularly polarized electric field vector or a second circularly polarized electric field vector, wherein the first circularly polarized electric field vector and the second circularly polarized electric field vector are 180°

out of phase with each other.

10. The radio frequency communication device of claim 1, wherein the data signal comprises a data stream of logic 1 and logic 0 bits.

11. The radio frequency communication device of claim 10, wherein the circuit further comprises an encoder circuit operable to organize a portion of the data signal into one of a plurality of groupings of multiple logic bits, wherein each grouping of multiple logic bits is operable to allow the radio frequency carrier signal to travel a circuit path, wherein the circuit path directs the radio frequency carrier signal to an operably positioned feedpoint on the antenna, wherein application of the radio frequency carrier signal to the feedpoint causes the antenna to emit a radio frequency signal having one of a plurality of electric field vector phases based on the input data signal.

12. The radio frequency communication device of claim 1, further comprising:

a quarter wave transmission line and a shunt capacitor on each of the plurality of circuit paths, operably configured to provide coupling of the data signal to the plurality of circuit paths, radio frequency carrier signal isolation, and capacitance tuning.

13. The radio frequency communication device of claim 1, further comprising:

a PIN diode on each of the plurality of circuit paths, operably configured to switch the radio frequency carrier signal from a first circuit path to a second circuit path.

14. The radio frequency communication of device of claim 1, further comprising:

at least two radio frequency coupling capacitors, operably configured to block direct current from the radio frequency carrier signal source and to couple the radio frequency carrier signal to the plurality of circuit paths.

15. The radio frequency communication device of claim 1, further comprising:

half wavelength transmission lines on each of the plurality of circuit paths, operably configured to provide isolation between the feedpoints on the antenna.

16. The radio frequency communication device of claim 1, further comprising:

connecting the center point of the probe fed patch antenna to the ground plane through a resistor-capacitor circuit, wherein the resistor-capacitor circuit is part of a first and a second circuit path, wherein the current flows through a first PIN diode in at least a first circuit path to turn ON the first PIN diode, and wherein the patch data signal voltage between the antenna and ground plane reverse biases a second PIN diode in at least a second circuit path to turn OFF the second PIN diode.

17. A method for operating a radio frequency communication device, the method comprising:

receiving a radio frequency carrier signal;

receiving a data signal;

determining at least one circuit path associated with a position along an antenna based on a data state of the data signal;

emitting a radio frequency signal; and

adjusting the electric field vector phase of the emitted radio frequency signal based on the determined circuit path.

18. The method of claim 17, wherein the radio frequency carrier signal is a continuous wave signal at a predetermined frequency.

19. The method of claim 17, wherein the data signal is unipolar.

20. The method of claim 17, further comprising:

operably positioning half wavelength transmission lines to prevent impedance transformation, upon switching between a first circuit path and a second circuit path.

21. The method of claim 17, wherein the data signal comprises a first and second data signal, the second data signal comprising the complement of the first data signal.

22. The method of claim 17, wherein determining at least one circuit path associated with a position along an antenna based on a data state of the data signal comprises:

switching diodes of a diode pair between an ON or OFF state, wherein one of the diode pair is OFF and the other of the diode pair is ON;

isolating the data signal source from the radio frequency carrier signal with quarter wave transmission lines; and

directing the radio frequency carrier signal along at least one circuit path with the diode pair and a pair of capacitors.

23. The method of claim 17, wherein determining at least one circuit path associated with a position along an antenna based on a data state of the data signal comprises:

switching diodes of a diode plurality between an ON or OFF state, wherein one of the diode plurality is ON and the remainder of the diode plurality are OFF;

isolating the data signal source from the radio frequency carrier signal with quarter wave transmission lines; and

directing the radio frequency carrier signal along one circuit path with the plurality of diodes.

24. The method of claim 17, wherein adjusting the electric field vector phase of the emitted radio frequency signal based on the determined circuit path, comprises:

feeding the radio frequency carrier signal to an antenna feedpoint set by the determined circuit path.

25. The method of claim 17, wherein the data signal, comprises a first and second data stream, wherein the first data stream comprises a first and a second data signal, the second data signal comprising the complement of the first data signal, wherein the second data stream comprises at least a third and a fourth data signal, the fourth data signal comprising the complement of the third data signal.

26. The method of claim 25, wherein determining at least one circuit path associated with a position along an antenna based on a data state of the data signal comprises:

switching diodes of two diode pairs between an ON or OFF state, wherein a first of each diode pair is OFF and a second of each diode pair is ON;

isolating the data signal source from the radio frequency carrier signal with quarter wave transmission lines; and

directing the radio frequency carrier signal along two circuit paths simultaneously with the two diode pairs and capacitors.

27. The method of claim 26, wherein adjusting the electric field vector phase of the emitted radio frequency signal based on the determined circuit path, comprises:

feeding a radio frequency carrier signal traveling simultaneously along two circuit paths to an antenna at two orthogonally spaced feedpoints set by the two circuit paths.

28. A radio frequency communication device comprising:

means for receiving an radio frequency carrier signal;

means for receiving at least a first data signal;

means for determining a circuit path based on a data state of the first data signal; and

means for adjusting the electric field vector phase of an emitted radio frequency signal based on the determined circuit path.

29. The means of claim 28, further comprising:

means of positioning half wavelength transmission lines to prevent impedance transformation, upon switching between a first circuit path and a second circuit path.

30. The means of claim 28, further comprising:

means of orthogonally spacing the feedpoints of a probe fed patch antenna to implement quadrature phase modulation.