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

• US 6,370,358 B2
• Filed: 12/29/2000
• Issued: 04/09/2002
• Est. Priority Date: 11/18/1996
• Status: Expired due to Term

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Corporation
• Inventors: Liimatainen, Jukka
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): Tran, Congvan
• Application Number:
  US09/751,731
• Publication Number:
  US 20010006887A1
• Time in Patent Office: 466 Days
• Field of Search: 455/67.1, 455/67.3, 455/115, 455/116, 455/126, 455/127, 455/151.1, 455/151.4, 455/13.4, 455/522, 330/278, 330/279
• 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) transmitter power control loop comprising the steps of:

sampling an output of an RF detector circuit to obtain a measurement of a value of the output of the RF detector circuit during a time when an RF signal is not input to the RF detector circuit;

storing the measurement;

during a time when an RF signal is input to the RF detector circuit, using a loop error amplifier for providing a control signal that is corrected by a difference between the stored measurement and the output of the RF detector circuit when the RF signal is input to the RF detector circuit,

wherein the step of providing includes the steps of;

converting the measured value from an analog signal to a digital signal representation thereof;

combining the digital representation of the measured value with a transmitter power setting signal to obtain a digital corrected transmitter power setting signal;

converting the digital corrected transmitter power setting signal to an analog corrected transmitter power signal; and

during a time when an RF signal is input to the RF detector, subtracting in the loop error amplifier the output of the RF detector circuit from the analog corrected transmitter power setting signal.

2. 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;

during a time that an RF signal is not present, establishing a current flow path through said diode, switchably coupling the output of said envelope detector to a third capacitance having a first terminal coupled to a first input of an amplifier and a second terminal coupled to a reference potential, and storing a voltage potential appearing at the output of said envelope detector circuit on said third capacitance; and

during a time that an RF signal is present, establishing a current flow path through said diode, switchably coupling the output of said envelope detector to a second input of the amplifier, and obtaining a voltage potential at the output of said envelope detector when the RF signal is present, wherein the amplifier operates to output a signal having a magnitude that is indicative of a difference between the potentials applied to the first and second inputs of said amplifier.

3. A radio frequency (RF) signal power detector having an input node for coupling to a source of an RF signal to be detected and an output node, comprising:

an RF detector circuit having an input coupled to the input node of said RF signal power detector for receiving an RF signal that is input to the input node, and an output; and

circuitry including means for sampling the output of the RF detector circuit to obtain a measurement of a value appearing at the output of the RF detector during a time when no RF signal is input to the RF detector circuit, said circuitry including means for storing the measurement wherein said storing means is comprised of a capacitance coupled in series between said output of said RF detector circuit and said output node of said RF signal power detector, and means for subtracting, during a time 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 during the time when an RF signal is input to the RF detector circuit said output of said RF detector is indicative of an amplitude of the RE signal input to the RF detector.

4. A detector as set forth in claim 3, wherein the means for sampling operates between RF bursts.

5. A detector as set forth in claim 3, wherein the sampling means includes means for preventing the RF signal from entering the input of the RF detector circuit during the operation of said sampling means.

6. A detector as set forth in claim 3, wherein the sampling means is comprised of a switch coupled in series between the input of the RF detector circuit and the source of RF power, said switch being operated to open during the operation of said sampling means and to close during the operation of said subtracting means.

7. A detector as set forth in claim 3, and further comprising a sample and hold means coupled to the output of said RF detector circuit.

8. A detector as set forth in claim 3, and further comprising a sample and hold means coupled to the output of said subtracting means.

9. A detector as set forth in claim 3, and further comprising a closed loop RF amplifier gain control circuit that includes said detector, comprising:

means for combining the measured value with a transmitter power setting signal to obtain a corrected transmitter power setting signal; and

said means for subtracting subtracts 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.

10. A detector as set forth in claim 3, wherein said sampling means and storing means are comprised of a switch for periodically coupling, during a calibration period, the output of the RF detector circuit to a capacitance connected to a first input of an amplifier for impressing a potential across the capacitance that is equal to a potential output from the RF detector circuit, wherein the switch couples the output of the RF detector circuit to a second input of the amplifier at a termination of calibration period, and wherein the amplifier outputs a signal having a magnitude that is indicative of a difference between the potentials applied to the first and second inputs.

11. 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.

12. 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,

wherein said third circuit means comprises;

analog-to-digital converter circuit means coupled to the output of the RF detector for converting the output appearing at the output of the RF detector during a time said first circuit means operates to prevent to RF signal from entering said RF detector to a digital representation thereof;

fourth circuit means for combining the digital representation of the RF output with a transmitter power setting signal and outputting a digital corrected transmitter power setting signal;

digital-to-analog converter circuit means for converting the digital corrected transmitter power setting signal to an analog corrected transmitter power signal, and

a loop amplifier having a first input coupled to said output of said third circuit means, a second input coupled to said analog corrected transmitter power 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.

13. 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;

analog-to-digital converter circuit means coupled to a output of the RF detector for converting the output appearing at the output of the RF detector during a time said first circuit means operates to prevent the RF signal from entering said RF detector to a digital representation thereof;

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

digital-to-analog converter circuit means for converting the digital corrected transmitter power setting signal to an analog corrected transmitter power signal;

a loop amplifier having a first input coupled to said output of said RF detector, a second input coupled to said analog corrected transmitter power 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.

14. 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;

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;

analog-to-digital converter circuit means coupled to the output of the RF detector for converting the output appearing at the output of the RF detector during a time said first circuit means operates to prevent the RF signal from entering said RF detector to a digital representation thereof;

second circuit means for combining the digital representation of the RF output with a transmitter power setting signal to obtain a digital corrected transmitter power setting signal;

digital-to-analog converter circuit means for converting the digital corrected transmitter power setting signal to an analog corrected transmitter power signal;

a loop amplifier having a first input coupled to said output of said RF power detector, a second input coupled to the analog corrected transmitter 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 RE 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.