Method and apparatus for calibration of a wireless transmitter

• US 6,256,483 B1
• Filed: 09/28/1999
• Issued: 07/03/2001
• Est. Priority Date: 10/28/1998
• Status: Expired due to Term

• Current Assignee: Tachyon, Inc. (Tachyon Networks Incorporated)
• Original Assignee: Tachyon, Inc. (Tachyon Networks Incorporated)
• Inventors: Becker, Donald W., Moerder, Karl E.
• Primary Examiner(s): Nguyen, Lee
• Application Number:
  US09/407,641
• Time in Patent Office: 644 Days
• Field of Search: 455/115, 455/116, 455/126, 455/127, 455/69, 455/63, 455/522, 330/144, 330/284, 330/279
• US Class Current: 455/115.1
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04
• CPC Class Codes: H03G 3/3047 for intermittent signals, e.g. burst signals
• CPC Class Codes: H04B 17/13 of power amplifiers, e.g. gain or non-linearity
• CPC Class Codes: H04W 52/36 with a discrete range or set of values, e.g. step size, ramping or offsets
• CPC Class Codes: H04W 52/52 using AGC [Automatic Gain Control] circuits or amplifiers

Abstract

When an installed wireless remote unit is operating in the field, routine operation is interrupted to enter a calibration mode. In calibration mode, the compression point of a circuit element is determined by applying a series of different drive levels to the circuit element. Based upon the determination of the compression point, a maximum transmission point is selected for the remote unit. Upon resumption of normal operation, the remote unit uses the maximum transmission point to limit the signal power level transmitted over the wireless link. As time passes or operating conditions change, the calibration process is re-executed.

Claims

1. An installed communication unit, comprising:

a first unit comprising;

a power amplifier configured to receive a driving signal and producing a transmission signal;

a power detector coupled to said power amplifier so as to receive said transmission signal and producing an indication of a signal power level of said transmission signal;

a microprocessor coupled to said power detector so as to receive said indication produced by said power detector and configured to produce a corresponding digital data output value; and

a second unit comprising;

a variable gain amplifier having a gain setting input coupled to said power amplifier and producing said driving signal;

a controller coupled to said microprocessor and coupled to said gain setting input, said controller configured to interrupt routine operation to determine a maximum value for said gain setting input corresponding to a compression point of said power amplifier at current operating conditions by increasing a value of said gain setting input such that said driving signal is of sufficient amplitude to drive said power amplifier into compression, recording a first corresponding digital data output value and decreasing said value of said gain setting input until a second corresponding digital data value falls below said first corresponding digital data value by a predetermined amount; and

a memory coupled to said controller and storing said maximum value.

2. A method of calibrating transmission circuitry of an installed communication unit, comprising the steps of:

interrupting routine operation;

generating a driving signal at a first level which drives a circuit element into saturation;

measuring a first signal power level produced by said circuit element;

setting said level of said driving signal to a second level that is lower than said first driving signal level;

measuring a second signal power level produced by said circuit element;

comparing said first signal power level to said second signal power level;

if said second signal power level is less than said first signal power level by more than a predetermined amount, using said second driving signal level as a maximum drive level for said circuit element upon resuming routine operation;

measuring a temperature at which said circuit element is operating; and

executing said step of interrupting routine operation in response to a change in said temperature.

3. A method of calibrating transmission circuitry of an installed communication unit, comprising the steps of:

interrupting routine operation;

generating a driving signal at a first level which drives a circuit element into saturation;

measuring a first signal power level produced by said circuit element;

setting said level of said driving signal to a second level that is lower than said first driving signal level;

measuring a second signal power level produced by said circuit element;

comparing said first signal power level to said second signal power level;

if said second signal power level is less than said first signal power level by more than a predetermined amount, using said second driving signal level as a maximum drive level for said circuit element upon resuming routine operation;

measuring current conditions at which said circuit element is operating;

comparing said current conditions to a list of previously stored maximum drive levels and corresponding operating conditions; and

executing said step of interrupting routine operation if no previously stored maximum drive level listing is available for said current conditions.

4. A method of calibrating transmission circuitry of an installed communication unit, comprising the steps of:

interrupting routine operation;

generating a driving signal at a first level which drives a circuit element into saturation;

measuring a first signal power level produced by said circuit element by

generating said driving signal such that an amplitude of said driving signal varies over time;

converting a series of analog values, each corresponding to an instantaneous signal power level produced by said circuit element, into a set of digital values; and

averaging said set of digital values to determine said first signal power level;

setting said level of said driving signal to a second level that is lower than said first driving signal level;

measuring a second signal power level produced by said circuit element;

comparing said first signal power level to said second signal power level; and

if said second signal power level is less than said first signal power level by more than a predetermined amount, using said second driving signal level as a maximum drive level for said circuit element upon resuming routine operation.

5. A method of calibrating transmission circuitry of an installed communication unit, comprising the steps of:

interrupting routine operation;

generating a driving signal at a first level which drives a circuit element into saturation;

measuring a first signal power level produced by said circuit element;

setting said level of said driving signal to a second level that is lower than said first driving signal level;

measuring a second signal power level produced by said circuit element;

comparing said first signal power level to said second signal power level;

if said second signal power level is less than said first signal power level by more than a predetermined amount, using said second driving signal level as a maximum drive level for said circuit element upon resuming routine operation;

resuming routine operation;

receiving a command from a hub station to increase a signal power level at which said circuit element produces a signal;

increasing the level of said driving signal if said level is less than said maximum drive level; and

decreasing a data rate at which data is transmitted if said level of said driving signal is greater than or equal to said maximum drive level.

6. An apparatus for calibrating transmission circuitry of an installed communication unit, comprising:

means for interrupting routine operation;

means for generating a driving signal at a first level which drives a circuit element into saturation;

means for measuring a first signal power level produced by said circuit element;

means for setting said level of said driving signal to a second level that is lower than said first driving signal level;

means for measuring a second signal power level produced by said circuit element;

means for comparing said first signal power level to said second signal power level, and, if said second signal power level is less than said first signal power level by more than a predetermined amount, using said lower value as a maximum drive level for said circuit element upon resuming routine operation; and

means for measuring a temperature at which said circuit element is operating and interrupting routine operation in response to a change in said temperature.

7. An apparatus for calibrating transmission circuitry of an installed communication unit, comprising:

means for interrupting routine operation;

means for generating a driving signal at a first level which drives a circuit element into saturation;

means for measuring a first signal power level produced by said circuit element;

means for setting said level of said driving signal to a second level that is lower than said first driving signal level;

means for measuring a second signal power level produced by said circuit element; and

means for comparing said first signal power level to said second signal power level, and, if said second signal power level is less than said first signal power level by more than a predetermined amount, using said lower value as a maximum drive level for said circuit element upon resuming routine operation;

means for measuring current conditions at which said circuit element is operating; and

means for comparing said current conditions to a list of previously stored maximum drive levels and corresponding operating conditions and activating said means for interrupting routine operation if no previously stored maximum drive level listing is available for said current conditions.

8. An apparatus for calibrating transmission circuitry of an installed communication unit, comprising:

means for interrupting routine operation;

means for generating a driving signal at a first level which drives a circuit element into saturation;

means for measuring a first signal power level produced by said circuit element, including

means for generating said driving signal such that an amplitude of said driving signal varies over time;

means for converting a series of analog values, each corresponding to an instantaneous signal power level produced by said circuit element, into a set of digital values; and

means for averaging said set of digital values to determine said first signal power level;

means for setting said level of said driving signal to a second level that is lower than said first driving signal level;

means for measuring a second signal power level produced by said circuit element; and

means for comparing said first signal power level to said second signal power level, and, if said second signal power level is less than said first signal power level by more than a predetermined amount, using said lower value as a maximum drive level for said circuit element upon resuming routine operation.

9. An apparatus for calibrating transmission circuitry of an installed communication unit, comprising:

means for interrupting routine operation;

means for generating a driving signal at a first level which drives a circuit element into saturation;

means for measuring a first signal power level produced by said circuit element;

means for setting said level of said driving signal to a second level that is lower than said first driving signal level;

means for measuring a second signal power level produced by said circuit element;

means for comparing said first signal power level to said second signal power level, and, if said second signal power level is less than said first signal power level by more than a predetermined amount, using said lower value as a maximum drive level for said circuit element upon resuming routine operation;

means for receiving a command from a hub station to increase a signal power level at which said circuit element produces a signal upon resuming routine operation; and

means for increasing a level of said driving signal if said level is less than said maximum drive level, and decreasing a data rate at which data is transmitted if said signal level is greater than or equal to said maximum drive level.

10. A method of limiting the output power of a wireless unit, comprising the steps of:

interruptions routine operation of an installed communication unit;

selecting a maximum transmission point for said installed communication unit by applying a series of different drive levels to a circuit element within the installed communication unit to determine a compression point of the circuit element;

resuming routine operation using said maximum transmission point to limit a transmission power of said installed communication unit

measuring current conditions at which said installed communication unit is operating;

comparing said current conditions to a list of previously stored maximum transmission points and corresponding operating conditions; and

executing said step of interrupting routine operation if no previously stored maximum transmission point listing is available for said current conditions.