Method and apparatus for improving the directivity of an antenna

• US 7,369,833 B2
• Filed: 01/13/2006
• Issued: 05/06/2008
• Est. Priority Date: 12/03/1998
• Status: Expired due to Fees

• Current Assignee: Callahan Cellular LLC (Intellectual Ventures LLC)
• Original Assignee: Apex/Eclipse Systems, Inc.
• Inventors: Smith, Harry B
• Primary Examiner(s): Gesesse; Tilahun
• Application Number:
  US11/331,183
• Publication Number:
  US 20070026900A1
• Time in Patent Office: 844 Days
• Field of Search: 455/562.1, 455/561, 455/277.1, 455/277.2, 455/278.1, 455/63.1, 455/226.3, 375/347, 375/332
• US Class Current: 455/277.2
• CPC Class Codes: H01Q 3/26 varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture H01Q3/12, H01Q3/22, H01Q3/24 take precedence
• CPC Class Codes: H04B 7/0857 using maximum ratio combining techniques, e.g. signal-to- interference ratio [SIR], received signal strenght indication [RSS]

Abstract

A receive system, including special integrated circuits, for providing enhanced directivity in the form of a narrowed receive beam and a relatively small antenna with performance comparable to a much larger antenna at similar frequencies. Received signals are converted to digital values and stored in a manner which enables subsequent processing directed to improving the resolution of the received signals and to reduce the associated noise corresponding to the received data samples. The Signal-to-Noise ratio of the received data signals is improved as a result of processing techniques made possible by the configuration of the antenna and the digitally stored nature of the received data.

Claims

1. A method of improving the directivity of a receive system, the method comprising:

receiving receive signals from an antenna array, the antenna array comprising a plurality of elements;

amplifying the receive signals to form amplified signal-plus-noise signals;

determining a phi-phase equivalent to a difference between a reference phase and a phase of the amplified signal-plus-noise signals;

forming in-phase (I) and quadrature (Q) versions of the amplified signal-plus-noise signals by subtracting the phi-phase and adding or subtracting about ninety degrees from the in-phase version to form the quadrature version;

multiplying the phase difference by each of a series of integers to create a plurality of outputs;

summing the outputs coherently to form an improved overall output with an improved sensitivity substantially greater than a normal sensitivity of the receive signals; and

computing the arctangent of a noise reduced quadrature signal divided by a noise reduced in-phase signal to constitute an angle, phi, of the signal.

2. A method of improving the directivity of a receive system as claimed in claim 1, further comprising:

generating a plurality of new I and Q values by multiplying each angle, phi, by a series of respective integer multipliers; and

mathematically synthesizing a series of new antenna directivity patterns using one or more of the plurality of new I and Q values.

3. The method as claimed in claim 1, wherein the receive signals are received from a satellite.

4. The method as claimed in claim 3, further comprising receiving streaming transmissions of receive signals from the satellite and, wherein one or more of lower overall satellite transmission power, increased channels of information, lower power per channel and an increased ability to discriminate between desired receive signals and receive signals from unwanted directions is achieved.

5. A method as claimed in claim 1, wherein the elements of the antenna array are spaced apart from each other by a distance equal to an integer multiple of the wavelength of the receive signals.

6. A method of improving the directivity of an antenna of a receive system that receives receive signals, the method comprising:

forming a topological number array (TNA) for at least two successive trials of the receive signals, wherein the TNA contains data consisting of in-phase and quadrature versions of the receive signals;

performing an iterative process on the data contained in the TNA to determine an estimate of the magnitude and polarity of the noise portion of the receive signals for each trial, wherein the iterative process consists at least of successively adding a series of equally spaced values to the data and determining a particular value that causes the noise portion to change polarity;

subtracting each estimated noise value from the receive signals to obtain a noise-reduced signal;

computing the arctangent of a noise reduced quadrature signal divided by a noise reduced in-phase signal to constitute an angle, phi, of the signal.

7. A method of improving the directivity of an antenna that receives receive signals as claimed in claim 6, further comprising mathematically calculating new respective angles (phi prime), corresponding to receive angles of the receive signals, wherein the phi prime angles have significantly less phase dispersion as compared to the receive angles of the receive signals.

8. The method as claimed in claim 6, further comprising:

isolating one of the received signals;

synchronizing the receive system with a system timing clock, wherein the timing clock is used to sample both in-phase and quadrature analog signals; and

establishing a zero-phase reference.

9. The method as claimed in claim 6, wherein an extent to which noise has been reduced in the noise-reduced signal corresponds to noise remnants of one or more of quantization noise that occurs in a digital conversation process, phase noise from imperfect multiplication of the digital phase angle phi, residual noise that remains as a result of bipolar constants of integration, and other noise-like interference received from external sources.

10. The method as claimed in claim 6, wherein the receive signals have frequencies in the range of 10-23 gigahertz and the noise-reduced signal compensates for noisier reception caused by increased signal attenuation.

11. The method as claimed in claim 6, wherein a fast matched filter is achieved by estimating the polarity and magnitude of the noise in two half-cycles at an intermediate carrier frequency.

12. The method as claimed in claim 6, wherein additional noise is removed with each iteration of the TNA.

13. The method as claimed in claim 11, further comprising integrating the reduced-noise signals one or more times to further reduce the amount of noise in the receive signals, wherein the amount of signal-to-noise improvement increases exponentially with each additional integration.

14. The method as claimed in claim 6, wherein the signal-to-noise improvement is equivalent to placing the signal within an acceptance region of a phase gate while gating out a non-informational portion of the noise.

15. A receive system with improved directivity, the system comprising:

an antenna array comprising a plurality of elements, each element operable to receive electromagnetic waves over a band of frequencies, wherein the electromagnetic waves comprise receive signals;

an amplifier operable to amplify the receive signals to form amplified signal-plus-noise signals;

means for determining a phi-phase equivalent to a difference between a reference phase and a phase of the amplified signal-plus-noise signals;

means for forming in-phase and quadrature versions of the amplified signal-plus-noise signals by subtracting said phi-phase and adding or subtracting about ninety degrees from the in-phase version to form the quadrature version;

means for multiplying the phase difference by each of a series of integers to create a plurality of outputs;

means for summing the outputs coherently to form an improved overall output with an improved sensitivity substantially greater than a normal sensitivity of the receive signals; and

means for computing the arctangent of a noise reduced quadrature signal divided by a noise reduced in-phase signal to constitute an angle, phi, of the signal.

16. The receive system as claimed in claim 15, wherein each of the antenna array elements comprise at least one of a dipole, a waveguide slot, a spiral or open-ended waveguide and a horn.

17. The receive system as claimed in claim 15, wherein the plurality of elements of the antenna array form an asymmetrical pattern.

18. The receive system as claimed in claim 15, wherein each of the antenna array elements comprise a horn that receives the receive signals with at least one of linear and circular polarization.

19. The receive system as claimed in claim 15, further comprising:

means for generating one or more simultaneous phase gates, each phase gate corresponding to a predetermined segment of angular coverage with respect to the receive signals at different angles corresponding to different signal directions resulting in stacks of beams covering multiple directions for reception of the receive signals.

20. The receive system as claimed in claim 15, wherein the receive signals result from transmitted signals transmitted from a transmitter in a two-way system and wherein, further, echo signals generated by the transmitted signals reflecting off one or more objects are effectively canceled.

21. A computer program storage medium readable by a computer system and encoding a computer program for executing a process, the process comprising:

receiving receive signals from an antenna array, the antenna array comprising a plurality of elements;

amplifying the receive signals to form amplified signal-plus-noise signals;

determining a phi-phase equivalent to a difference between a reference phase and a phase of the amplified signal-plus-noise signals;

forming in-phase (I) and quadrature (Q) versions of the amplified signal-plus-noise signals by subtracting the phi-phase and adding or subtracting about ninety degrees from the in-phase version to form the quadrature version;

multiplying the phase difference by each of a series of integers to create a plurality of outputs;

summing the outputs coherently to form an improved overall output with an improved sensitivity substantially greater than a normal sensitivity of the receive signals; and

computing the arctangent of a noise reduced quadrature signal divided by a noise reduced in-phase signal to constitute an angle, phi, of the signal.

22. A computer program product encoding a computer program for executing on a computer system a computer process, the computer process comprising:

receiving receive signals from an antenna array, the antenna array comprising a plurality of elements;

amplifying the receive signals to form amplified signal-plus-noise signals;

determining a phi-phase equivalent to a difference between a reference phase and a phase of the amplified signal-plus-noise signals;

forming in-phase (I) and quadrature (Q) versions of the amplified signal-plus-noise signals by subtracting the phi-phase and adding or subtracting about ninety degrees from the in-phase version to form the quadrature version;

multiplying the phase difference by each of a series of integers to create a plurality of outputs;

summing the outputs coherently to form an improved overall output with an improved sensitivity substantially greater than a normal sensitivity of the receive signals; and

computing the arctangent of a noise reduced quadrature signal divided by a noise reduced in-phase signal to constitute an angle, phi, of the signal.

23. The computer program product as claimed in claim 22, the computer process further comprising:

generating one or more simultaneous phase gates, each phase gate corresponding to a different segment of angular coverage with respect to the receive signals.