Adaptive automatic antenna tuning method and apparatus

• US 5,483,688 A
• Filed: 01/22/1993
• Issued: 01/09/1996
• Est. Priority Date: 01/22/1993
• Status: Expired due to Term

• Current Assignee: Seiko Instruments Incorporated (Seiko Group)
• Original Assignee: Seiko Communications Holding N.V.
• Inventors: English, James D., Nepple, Bruce C.
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): VO, NGUYEN THANH
• Application Number:
  US08/007,443
• Time in Patent Office: 1,082 Days
• Field of Search: 455/193.1, 455/184.1, 455/193.2, 455/193.3, 455/226.2, 455/290, 455/195.1, 455/173.1, 455/187.1, 455/169.1, 455/150.1, 455/197.2, 455/254 , 455/180.3, 455/180.4, 455/183.1, 455/183.2, 455/154.1, 455/150.1, 455/197.3
• US Class Current: 455/184.1
• CPC Class Codes: H01Q 3/2605 Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays
• CPC Class Codes: H01Q 7/005 with variable reactance for tuning the antenna
• CPC Class Codes: H04B 1/18 Input circuits, e.g. for coupling to an antenna or a transmission line coupling networks between antennas or lines and receivers independent of the nature of the receiver H03H

Abstract

An improved method and apparatus for automatically tuning an antenna includes adaptive antenna tuning based on a current radio reception frequency and on prior antenna tuning cycles to establish a predictor value. The predictor value establishes an antenna tuning voltage sub-range most likely to contain the optimum antenna tuning voltage, but is a smaller range than the full antenna tuning voltage range. The antenna tuning voltage sub-range is then traversed while monitoring a signal strength indicator to identify an antenna tuning voltage providing optimum tuning conditions. Because only a sub-range of the full antenna tuning voltage range need be traversed, by virtue of the predictor value, relatively small increments in antenna tuning voltage may be used in traversing this sub-range. As a result, the execution time and accuracy of the antenna tuning method of the present invention is improved relative to prior automatic antenna tuning methods.

Claims

1. A programmable antenna tuning device for coupling an antenna and a radio receiver, said device generating an antenna tuning signal, said radio receiver being able to tune over a range of frequencies, and being responsive to a signal representing a desired reception frequency, said device comprising:

an antenna tuning element coupled to said antenna and responsive to said antenna tuning signal, said antenna tuning element being operable within a first range of said antenna tuning signal;

a prediction element responsive to at least one of said signal representing a desired reception frequency and a prior stored preferred antenna tuning signal for producing a predicted tuning signal representing a predicted value for said antenna tuning signal, and for producing a sub-range signal which defines a sub-range for said antenna tuning signal, said sub-range being less than said first range and including the value of said predicted tuning signal; and

a control element means for receiving from said prediction element said sub-range signal and for applying said antenna tuning signal through the range of said sub-range, identifying a preferred antenna tuning signal by detecting the optimum output from said antenna, storing said preferred antenna tuning signal, and applying said preferred antenna tuning signal to said antenna tuning element.

2. A device according to claim 1 wherein said sub-range signal defines an offset value and a gain parameter and said control element means includes an analog voltage device producing variation in voltage within said sub-range in response to said offset value and said gain parameter for application to a voltage responsive tuning network of said antenna tuning element.

3. A device according to claim 1 wherein said control element means returns to said prediction element a representation of said preferred antenna tuning signal.

4. A device according to claim 1 wherein said prediction element is responsive to said signal representing a desired reception frequency and said prediction element produces said predicted tuning signal as a function of a radio frequency at which said radio receiver is to receive information when attached to said antenna tuning element.

5. A device according to claim 1 wherein said control element means provides to said prediction element a representation of a value of said preferred antenna tuning signal as stored, and said prediction element produces a next predicted antenna tuning signal taking into account said preferred antenna tuning signal.

6. A method of tuning an antenna for optimum reception of a desired frequency signal by application of an antenna tuning signal to an antenna tuning network, said network having the the full tuning range, the method comprising the steps:

predicting a preferred antenna tuning signal based upon at least one of said desired frequency and a prior stored preferred antenna tuning signal;

identifying an antenna tuning sub-range less than said full range, said sub-range including said predicted preferred antenna tuning signal;

applying to said antenna tuning network antenna tuning signals having values within said sub-range while monitoring a received signal strength indicator;

detecting a preferred antenna tuning signal associated with a maximum value in said received signal strength indicator;

storing said preferred antenna tuning signal; and

applying said detected preferred antenna tuning signal to said network.

7. A method of tuning an antenna for reception of a desired frequency in a radio receiver and antenna combination, said radio receiver being tunable to several radio signal frequencies and having an antenna tuning element responsive to an antenna tuning control signal, said tuning control signal having a first range, the antenna tuning element providing a preferred antenna tuning at a given tuning control signal value, the method of antenna tuning comprising the steps:

calculating a predicted preferred antenna tuning control signal value as a function of at least one of said desired frequency and a prior stored preferred antenna tuning control signal;

selecting an antenna tuning sub-range within said antenna tuning control signal range as a function of said predicted preferred antenna tuning control signal value, said sub-range being less than said first range;

operating said radio receiver on said desired frequency while monitoring a received signal strength indicator;

presenting to said antenna tuning element antenna tuning control signal values taken from said sub-range;

selecting and storing a preferred antenna tuning control signal value in association with a maximum received signal strength indicator; and

applying said selected preferred antenna tuning control signal value to said antenna tuning element.

8. A method of generating an antenna tuning signal for a multifrequency radio receiver, said radio receiver being tuned to a desired frequency, said tuning signal having a tuning range, including the steps of:

a) calculating a predicted value of said tuning signal based entirely upon the value of said desired frequency, and determining an error in said predicted value,

b) modifying said predicted value of said tuning signal based upon an error found in a previous predicted value to generate a modified predicted value,

c) tuning said antenna over a subset range of said tuning range, said subset range being determined by and including said modified predicted value, said subset range being less than said tuning range,

d) modifying said modified predicted value based upon the value of tuning signal which produces the optimum reception by said radio receiver,

e) calculating the error between the predicted value and the value of the tuning signal that produces the optimum reception by said radio receiver for use for use in performing the calculation of a predicted value when the value of said desired frequency changes.