Comprehensive transmitter power control system for radio telephones

• US 6,236,863 B1
• Filed: 03/17/1998
• Issued: 05/22/2001
• Est. Priority Date: 03/31/1997
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: OKI Telecom, Inc. (OKI Electric Industry Company Limited)
• Inventors: Lyall, Robert L. Jr., Waldroup, Anthony B., Bain, Richard I.
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): Tran, Congvan
• Application Number:
  US09/042,759
• Time in Patent Office: 1,162 Days
• Field of Search: 455/13.4, 455/63, 455/67.3, 455/69, 455/133, 455/134, 455/135, 455/136, 455/295, 455/296, 455/422, 455/522, 455/572, 455/571, 455/574, 455/429, 455/246.1, 455/126, 455/420, 375/205, 375/254, 375/278, 375/284, 375/285, 375/346, 370/320, 370/342
• US Class Current: 455/522
• CPC Class Codes: H03F 1/30 Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters in differential amplifiers H03F3/45479
• CPC Class Codes: H03G 3/3052 in bandpass amplifiers (H.F. or I.F.) or in frequency-changers used in a (super)heterodyne receiver H03G3/32, H03G3/34 take precedence
• CPC Class Codes: H03G 3/3078 Circuits generating control signals for digitally modulated signals
• CPC Class Codes: H04B 1/04 Circuits
• CPC Class Codes: H04B 2001/0416 having gain or transmission power control
• CPC Class Codes: H04W 52/08 Closed loop power control
• CPC Class Codes: H04W 52/10 Open loop power control
• CPC Class Codes: H04W 52/52 using AGC [Automatic Gain Control] circuits or amplifiers

Abstract

An output power control system prevents saturation by limiting total output power and maintaining closed loop responsiveness for a radio telephone having closed loop and open loop gain control systems. The output power control system determines when total output power exceeds an output power trigger level and automatically enters a saturation prevention mode whereby total output power is reduced through modification of a closed loop power control register. In one embodiment, an output detector and an output comparator continuously monitor output power, and in another embodiment, an analog-to-digital converter samples output power levels. Saturation prevention processes of various preferred embodiments include, through continual monitoring, edge-triggered interrupt servicing, and level-triggered interrupt servicing, subsequently modifying the closed loop power control register to decrease the closed loop output power control portion of the total output power until the output power falls below the output trigger level. A saturation prevention method of yet another embodiment includes maintaining the closed loop power control register at a constant level unless a decrease in received signal strength is detected, in which case the closed loop power control register is modified to compensate for an increased open loop component of the total output power.

Claims

1. A method of controlling output power of a radio telephone communicating with a base station, said method comprising steps of:

attenuating received RF signals on an RF signal receiver line of the radio telephone to reduce intermodulation (IM) distortion including a step of coupling a variable attenuator circuit to the RF signal receiver line; and

determining the output power according to received RF signal attenuation information and closed loop power control information received from the base station, including steps of determining an open loop output power correction value corresponding to the attenuation levels of the received RF signals, and adjusting the output power according to the open loop output power correction value to compensate for attenuation of received RF signals.

2. The method of claim 1, wherein the determining step includes a step of adjusting an open loop power control signal according to the received RF signal attenuation information and the closed loop power control information received from the base station.

3. The method of claim 2, wherein the adjusting step includes a step of adjusting a closed loop power control signal according the received RF signal attenuation information and the closed loop power control information.

4. A method of controlling output power of a radio telephone communicating with a base station, said method comprising steps of:

attenuating received RF signals on an RF signal receiver line of the radio telephone to reduce intermodulation (IM) distortion including a step of coupling a variable attenuator circuit to the RF signal receiver line; and

determining the output power according to received RF signal attenuation information and closed loop power control information received from the base station, including a step of adjusting an open loop power control signal according to the received RF signal attenuation information and the closed loop power control information received from the base station, wherein the adjusting step includes a step of adjusting a closed loop power control signal according to the received RF signal attenuation information and the closed loop power control information, wherein the step of adjusting the closed loop power control signal includes a step of combining the received RF signal attenuation information and the closed loop power control information.

5. A method of controlling output power of a radio telephone communicating with a base station, said method comprising steps of:

attenuating received RF signals on an RF signal receiver line of the radio telephone to reduce intermodulation (IM) distortion including a step of coupling a variable attenuator circuit to the RF signal receiver line; and

determining the output power according to received RF signal attenuation information and closed loop power control information received from the base station, including a step of adjusting an open loop power control signal according to the received RF signal attenuation information and the closed loop power control information received from the base station, wherein the adjusting step includes a step of adjusting a closed loop power control signal according the received RF signal attenuation information and the closed loop power control information, wherein the step of adjusting the open loop power control signal further includes a step of adding the adjusted closed loop power control signal to the open loop power control signal.

6. A method of controlling output power of a radio telephone communicating with a base station, said method comprising steps of:

attenuating received RF signals on an RF signal receiver line of the radio telephone to reduce intermodulation (IM) distortion including a step of coupling a variable attenuator circuit to the RF signal receiver line; and

determining the output power according to received RF signal attenuation information and closed loop power control information received from the base station, including a step of adjusting an open loop power control signal according to the received RF signal attenuation information and the closed loop power control information received from the base station, wherein the step of adjusting an open loop power control signal includes steps of determining an open loop output power correction value corresponding to the attenuation levels of the received RF signals, and adjusting the open loop power control signal according to the open loop output power correction value to compensate for attenuation of received RF signals.

7. The method of claim 6, wherein the step of adjusting the open loop power control signal according to the open loop output power correction value includes a step of adjusting a closed loop power control signal to compensate for the attenuation of the received RF signals.

8. The method of claim 6, wherein the step of determining an open loop output power correction value includes a step of determining relationships between the received RF signal strengths and an attenuation activation threshold level.

9. The method of claim 8, wherein the step of determining relationships between the received RF signal strength and an attenuation activation threshold level includes a step of comparing relationships between a received RF signal strength indication (RSSI) and the attenuation activation threshold level through an operational amplifier configured to provide a comparison output representative of the level of attenuation of the received RF signal.

10. The method of claim 9, wherein the step of continually determining an open loop output power correction value further includes steps of

generating and storing an integer value based on the comparison output, and

determining from the integer value the open loop output power correction value by comparing the integer value to a table of predefined open loop output power correction values.

11. The method of claim 6, wherein the step of determining an open loop output power correction value further includes steps of

generating and storing an integer value based on the received RF signal attenuation information, and

determining from the integer value the open loop output power correction value.

12. The method of claim 7, wherein the step of adjusting the closed loop power control signal includes a step of adjusting the closed loop power control signal by approximately one decibel every 1.25 milliseconds.

13. The method of claim 7, wherein the step of adjusting the closed loop power control signal includes a step of adjusting a digital memory element in response to the open loop output power correction value.

14. The method of claim 7, wherein the step of adjusting the closed loop power control signal further includes steps of

defining a filtered output power correction change to be a filtered change in output power required to compensate for attenuation of the received RF signals,

generating and supplying the filtered output power correction change, and

continually adjusting a digital memory element in response to a non-zero filtered output power correction change to continually adjust the closed loop power control signal.

15. The method of claim 14, wherein the step of generating and supplying the filtered output power correction change includes a step of generating and supplying the filtered output power correction change by comparing a filtered open loop output power correction value to an open loop output power counter value.

16. The method of claim 14, wherein the step of adjusting the closed loop power control signal further includes a step of continually adjusting a digital memory element in response to the filtered output power correction change to continually adjust the closed loop power control signal by one decibel every 1.25 milliseconds.

17. The method of claim 15, wherein the step of adjusting the closed loop power control signal further includes steps of

responsive to determining that the filtered output power correction change is positive wherein the filtered open loop output power correction value is greater than the open loop output power counter value,

adjusting the digital memory element to decrement the closed loop control system portion of the output power by approximately one decibel, and

incrementing the open loop output power counter value by one;

responsive to determining that the filtered output power correction change is negative wherein the filtered open loop output power correction value is less than the open loop output power counter value,

adjusting the digital memory element to increment the closed loop control system portion of the output power by approximately one decibel, and

decrementing the open loop output power counter value by one; and

repeating the above continually adjusting a digital memory element step every 1.25 milliseconds while the filtered output power correction change is non-zero.