Mobile station having drift-free pulsed power detection method and apparatus

• US 6,173,160 B1
• Filed: 11/18/1996
• Issued: 01/09/2001
• Est. Priority Date: 11/18/1996
• Status: Expired due to Term

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Mobile Phones UK Limited (Nokia Corporation)
• Inventors: Liimatainen, Jukka
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Aoki, Makoto
• Application Number:
  US08/746,931
• Time in Patent Office: 1,513 Days
• Field of Search: 455/45, 455/91, 455/115, 455/116, 455/126, 455/127, 330/278, 330/279, 330/289
• US Class Current: 455/67.11
• CPC Class Codes: G01R 21/10 by using square-law characteristics of circuit elements, e.g. diodes, to measure power absorbed by loads of known impedance G01R21/02 takes precedence
• CPC Class Codes: H03G 3/3047 for intermittent signals, e.g. burst signals

Abstract

In accordance with a method of this invention, and circuitry for performing the method, there is disclosed a process for operating a radio frequency (RF) signal power detector. The method includes the steps of (a) sampling the output of an RF detector circuit to obtain a measurement of a value of the output when no RF signal is input to the RF detector circuit; (b) storing the measurement; and (c) subtracting, when an RF signal is input to the RF detector circuit, the stored measurement from the output of the RF detector circuit to provide a subtracted output signal. In pulsed (e.g., TDMA) embodiments of this invention the step of sampling occurs between RF bursts, while in continuous wave (cw) embodiments the step of sampling occurs during a time that an RF connection is opened or otherwise blocked at an input of the RF detector circuit and a source of the RF signal. A sample and hold function can be provided for sampling and holding the subtracted output signal during a time that the input of the RF detector circuit is blocked. The step of subtracting includes the steps of combining the measured value with a transmitter power setting signal to obtain a corrected transmitter power setting signal; and subtracting the output of the RF detector circuit, when the RF signal is input to the RF detector circuit, from the corrected transmitter power setting signal.

Claims

1. A method for operating a radio frequency (RF) signal power detector having an input node for receiving RF energy and an output node, comprising the steps of:

providing an envelope detector comprised of a series coupled first capacitance, a diode, and a second capacitance, wherein a first terminal of said first capacitance is coupled to said input node, a second terminal of said first capacitance is coupled to a first terminal of said diode, a second terminal of said diode is coupled to a first terminal of said second capacitance, and a second terminal of said second capacitance is coupled to a reference potential, wherein an output of said envelope detector is taken between said second node of said diode and said first node of said second capacitance, said output of said envelope detector being coupled to said output node of said RF signal power detector through a third capacitance;

during a time that an RF signal is not present, establishing a current flow path through said diode and storing a voltage potential appearing at said output of said envelope detector on said third capacitance; and

during a time that an RF signal is present, interrupting said current flow path and detecting with said diode the RF signal, whereby the voltage appearing at said output node of said RF signal power detector represents a peak value of the detected RF signal minus the voltage potential appearing on said third capacitance.

2. A method as set forth in claim 1, wherein the step of establishing a current flow path occurs between RF bursts.

3. A method as set forth in claim 1, wherein the step of establishing a current flow path occurs between RF bursts in a TDMA mobile station.

4. A method as set forth in claim 1, wherein the step of establishing a current flow path includes a preliminary step of blocking the RF signal from reaching said input node of the RF detector circuit, and wherein the step of interrupting includes a step of allowing the RF signal to reach said input node of the RF detector circuit.

5. A method for operating a radio frequency signal power detector, comprising the steps of:

sampling the output of an RF detector circuit to obtain a measurement of a value of the output when no RF signal is input to the RF detector circuit;

storing the measurement; and

subtracting, when an RF signal is input to the RF detector circuit, the stored measurement from the output of the RF detector circuit to provide a subtracted output signal,

wherein there are two RF detector circuits, and wherein the steps of sampling and storing occur in one RF detector circuit simultaneously with the step of subtracting in the other RF detector circuit.

6. A radio frequency (RF) signal power detector, comprising:

an RF detector circuit having an input coupled to a source of RF power and an output; and

circuitry including means for sampling the output of the RF detector circuit to obtain a measurement of a value of the output when no RF signal is input to the RF detector circuit, said circuitry including means for storing the measurement and means for subtracting, when an RF signal is input to the RF detector circuit, the stored measurement from the output of the RF detector circuit to provide a subtracted output signal,

wherein there are two RF detector circuits that are alternately coupled between said source of RF power and a circuit that subtracts the output of a currently coupled one of the RF detector circuits from a RF amplifier power setting signal.

7. A radio frequency (RF) signal power detector, comprising:

an RF envelope detector circuit having an input coupled to a source of RF power and an output;

a dc blocking capacitor coupled in series between said output of said RF envelope detector circuit and an output node; and

a switch coupled between said output node and a reference potential;

wherein

said source of RF power outputs bursts of RF power, and wherein said switch is closed between two bursts and opened during a burst.

8. A closed loop transmitter power control system for use in a mobile station comprising:

a variable gain transmitter amplifier having an input coupled to a source of a RF signal and an output coupled to an antenna;

a power coupler coupled in series between said output of said amplifier and said antenna;

a RF detector having an input coupled to an output of said power coupler;

first circuit means, coupled between said output of said RF power coupler and said input of said RF detector, for periodically preventing the RF signal from entering said RF detector;

second circuit means having an input coupled to an output of said RF detector, and operating during a time that said first circuit means prevents the RF signal from entering said RF detector, for sampling and storing a magnitude of an output voltage appearing at said output of said RF detector, said second circuit means further operating, during a time that said first circuit means does not prevent the RF signal from entering said RF detector, for subtracting the stored magnitude from the output of said RF detector to provide a corrected RF detector output signal;

third circuit means for sampling a magnitude of the corrected RF detector output signal and for holding the magnitude of the corrected RF detector output signal for a time just prior to and during said first circuit means operating to prevent the RF signal from entering said RF detector; and

a loop amplifier having a first input coupled to said output of said third circuit means, a second input coupled to a power setting signal, and an output coupled to a control input of said variable gain transmitter amplifier, said loop amplifier operating to provide a transmitter gain control signal to said transmitter amplifier that maintains said closed loop power control system in equilibrium.

9. A closed loop transmitter power control system for use in a mobile station comprising:

a variable gain transmitter amplifier having an input coupled to a source of a RF signal and an output coupled to an antenna;

a power coupler coupled in series between said output of said amplifier and said antenna;

a RF detector having an input coupled to an output of said power coupler;

first circuit means, coupled between said output of said power coupler and said input of said RF detector, for periodically preventing the RF signal from entering said RF detector;

second circuit means having a first input coupled to a transmitter amplifier power setting signal and a second input coupled to an output of said RF detector, said second circuit means having an output for outputting a power control signal;

a loop amplifier having a first input coupled to said output of said RF detector, a second input coupled to said output of said second circuit means, and an output coupled to a control input of said variable gain transmitter amplifier, said loop amplifier operating to provide a transmitter gain control signal to said transmitter amplifier that maintains said closed loop power control system in equilibrium; and

sample and hold circuit means coupled to said closed loop power control system, and operating during a time that said first circuit means prevents the RF signal from entering said RF detector, for maintaining said transmitter gain control signal at a level that was in effect just prior to a time that said first circuit means prevents the RF signal from entering said RF detector.

10. A closed loop transmitter power control system for use in a mobile station comprising:

a variable gain transmitter amplifier having an input coupled to a source of a RF signal and an output coupled to an antenna;

a power coupler coupled in series between said output of said amplifier and said antenna;

a RF detector having an input coupled to an output of said power coupler, said RF detector comprising means for subtracting a magnitude of a detector bias potential from a magnitude of a detected RF signal plus detector bias potential;

circuit means, coupled between said output of said power coupler and said input of said RF detector, for periodically preventing the RF signal from entering said RF detector;

a loop amplifier having a first input coupled to said output of said RF power detector, a second input coupled to a transmitter amplifier power setting signal, and an output coupled to a control input of said variable gain transmitter amplifier, said loop amplifier operating to provide a transmitter gain control signal to said transmitter amplifier that maintains said closed loop power control system in equilibrium; and

sample and hold circuit means coupled to said closed loop power control system, and operating during a time that said first circuit means prevents the RF signal from entering said RF detector, for maintaining said transmitter gain control signal at a level that was in effect just prior to a time that said first circuit means prevents the RF signal from entering said RF detector.

11. A radio frequency (RF) energy power detector, comprising:

an RF envelope detector circuit having an input coupled to a source of RF energy and an output;

a dc blocking capacitor coupled in series between said output of said RF envelope detector circuit and an output node; and

a switch coupled between said output node and a reference potential;

wherein

said source of RF energy outputs bursts of RF energy, and wherein said switch is closed between bursts and opened just prior to a beginning of a burst.

12. A radiotelephone that operates in accordance with a time division, multiple access (TDMA) air interface, said radiotelephone comprising receiver circuitry and transmitter circuitry, said transmitter circuitry including a radio frequency (RF) energy detector, comprising:

an RF energy envelope detector circuit having an output and an input that is coupled to a source of bursts of RF energy;

a dc blocking capacitor coupled in series between said output of said RF envelope detector circuit and an output node; and

a switch coupled between said output node and a reference potential;

wherein

said source of RF energy outputs bursts of RF energy, and wherein said switch is controlled so as to be closed between bursts of RF energy and opened just prior to a beginning of a burst of RF energy.

13. A radio frequency (RF) signal power detector having an input node for receiving an RF signal and an output node, comprising an envelope detector comprised of a series coupled first capacitance, a diode, and a second capacitance, wherein a first terminal of said first capacitance is coupled to said input node, a second terminal of said first capacitance is coupled to a first terminal of said diode, a second terminal of said diode is coupled to a first terminal of said second capacitance, and a second terminal of said second capacitance is coupled to a reference potential, wherein an output of said envelope detector is taken between said second node of said diode and said first node of said second capacitance, said output of said envelope detector being coupled to said output node of said RF signal power detector through a third capacitance;

said RF signal power detector further being comprised of a switch that is closed during a time that the RF signal is not present for establishing a current flow path through said diode for storing a voltage potential appearing at said output of said envelope detector on said third capacitance, said switch being opened during a time that the RF signal is present for interrupting said current flow path, said diode detecting the RF signal during the time that the RF signal is present and outputting a voltage that appears at said output node of said RF signal power detector, said voltage representing a magnitude of the detected RF signal minus the voltage potential that was stored on said third capacitance.

14. The RF signal power detector of claim 13, wherein the RF signal occurs in bursts.

15. The RF signal power detector of claim 13, wherein the RF signal is present during a burst transmitted by a wireless user terminal.

16. The RF signal power detector of claim 13, wherein the RF signal is periodically present during a transmission by a wireless user terminal.

17. The RF signal power detector of claim 13, and further comprising means for generating a bias potential for said diode, and wherein said stored potential includes said bias potential.

18. The RF signal power detector of claim 13, wherein said RF signal power detector is coupled between an output of an RF transmitter amplifier and a gain control input of said RF transmitter amplifier in a closed loop feedback arrangement.

19. The RF signal power detector as in claim 18, wherein said RF signal power detector and said RF transmitter amplifier form a part of a wireless personal communicator.

20. The RF signal power detector as in claim 18, wherein said RF signal power detector and said RF transmitter amplifier form a part of a wireless personal communicator that transmits bursts of RF energy, and wherein the stored voltage potential is comprised of an undesirable bias voltage potential.