GB2307807A - Detecting and controlling radio frequency power using feedback to attenuator and amplifier - Google Patents

Detecting and controlling radio frequency power using feedback to attenuator and amplifier Download PDF

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Publication number
GB2307807A
GB2307807A GB9524584A GB9524584A GB2307807A GB 2307807 A GB2307807 A GB 2307807A GB 9524584 A GB9524584 A GB 9524584A GB 9524584 A GB9524584 A GB 9524584A GB 2307807 A GB2307807 A GB 2307807A
Authority
GB
United Kingdom
Prior art keywords
radio frequency
amplifier
attenuator
output
input
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB9524584A
Other versions
GB9524584D0 (en
Inventor
Stephen W Wasko
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nokia Oyj
Original Assignee
Nokia Telecommunications Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nokia Telecommunications Oy filed Critical Nokia Telecommunications Oy
Priority to GB9524584A priority Critical patent/GB2307807A/en
Publication of GB9524584D0 publication Critical patent/GB9524584D0/en
Publication of GB2307807A publication Critical patent/GB2307807A/en
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers without distortion of the input signal
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H03G3/3036—Automatic control in amplifiers having semiconductor devices in high-frequency amplifiers or in frequency-changers
    • H03G3/3042—Automatic control in amplifiers having semiconductor devices in high-frequency amplifiers or in frequency-changers in modulators, frequency-changers, transmitters or power amplifiers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers without distortion of the input signal
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H03G3/3036—Automatic control in amplifiers having semiconductor devices in high-frequency amplifiers or in frequency-changers

Abstract

Apparatus for detecting and controlling radio frequency power comprises an attenuator (2) to which a radio frequency input signal is applied. The output of the attenuator (2) is fed to a variable gain amplifier (3). The output of the amplifier (3) is fed to a power detector (4) the output of which is fed to an error amplifier (5) providing an output (6). The output (6) is fed back by means of a feedback loop (7) to control the attenuation of the attenuator (2) and the gain of the amplifier (3) so as to maintain the magnitude of the radio frequency power at the input of the power detector (4) at a predetermined level.

Description

TITLE: DETECTING AND CONTROLLING RADIO FREOUENCY POWER This invention relates to apparatus for and a method of detecting and controlling radio frequency power.
According to one aspect of the invention there is provided apparatus for detecting and controlling radio frequency power, comprising input means for the application of a radio frequency signal, a series arrangement to which the radio frequency signal is applied and which includes a controllable amplifier means, a power detector and an error amplifier, and a feedback loop for feeding back to the amplifier means a feedback signal representative of the output of the error amplifier, the feedback signal controlling the gain of the amplifier means to maintain the magnitude of the radio frequency power at the input of the power detector at a predetermined level or within a predetermined range. The use of the amplifying means increases the level of signal at the power detector, increasing the absolute power range that can be detected.
The series arrangement may additionally include a variable attenuator connected between the input means and the controllable amplifier means, the feedback signal being additionally applied to the variable attenuator to control the attenuation level.
In a known form of a power detector using a diode, the dynamic range is limited by the detector diode or its linearising circuit. In the inventive apparatus, the dynamic range of the amplifying means (and the attenuator, if present) determines the dynamic range of the apparatus, resulting in an extension of the practical detection range by over 20 dB for a simple implementation.
According to another aspect of the invention a method of detecting and controlling radio frequency power comprises applying a radio frequency signal to a series arrangement comprising a controllable amplifier means, a power detector and an error amplifier, feeding back from the error amplifier to the controllable amplifier means a feedback signal which is representative of the output of the error amplifier and which controls the gain of the amplifier means to maintain the magnitude of the radio frequency power at the input of the power detector at a predetermined level or within a predetermined range.
Preferably, the feedback signal is additionally applied to an attenuator to the input of which the radio frequency signal is applied and the output of which supplies the controllable amplifier means, the feedback signal controlling the attenuation level of the attenuator.
Apparatus according to the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic view of the apparatus, Figure 2 shows how the apparatus of Figure 1 can be incorporated in a radio transmitter, and Figure 3 shows how the apparatus of Figure 1 can be incorporated in a radio receiver.
Referring to Figure 1, a radio frequency input signal, e.g. at 1.8 GHz, is applied at an input 1. The input signal carries information by means of a modulation, such as GMSK modulation.
The input signal is applied to a variable attenuator 2, the attenuation of which is typically variable between -3 and -30 dB. The output of the attenuator is fed to a variable gain amplifier 3 the gain of which is variable between 0 and 20 dB. The output of the variable gain amplifier is fed to the input of a power detector 4 whose output is connected to one input of an error amplifier 5. The other input to the error amplifier 5 is a fixed reference voltage, and the error amplifier produces an output 6 dependent on the difference between its two inputs. The output 6 of the error amplifier 5 constitutes the output signal of the apparatus and is representative of the radio frequency power level of the input signal.
The output signal, or a signal derived therefrom e.g. by scaling, is applied, by means of a feedback loop 7, to the attenuator 2 and to the variable gain amplifier 3.
The feedback signal applied by the feedback loop 7 varies the attenuation level applied to the input signal by the attenuator 2, and also varies the gain of the amplifier 3, in such manner as to tend to maintain the radio frequency power level at point 8 (the input to the power detector 4), at a constant level or within a predetermined limited range. For example, if the power level of the input signal increases, the feedback signal causes the attenuation applied by the attenuator 2 to increase and the gain of the amplifier 3 to decrease, thus bringing the power level at the point 8 back to the predetermined level.
Similarly, if the power level of the input signal decreases, the feedback signal causes the attenuation level to decrease and the gain to increase, again bringing the power level at the point 8 back to the predetermined level.
The radio frequency power level at point 8 is thus maintained at a predetermined quiescent level. In consequence, the power detector 4 need have temperature compensation for one power level only, an important advantage over many prior art arrangements.
The dynamic range of the apparatus depends on the attenuation and gain ranges of the attenuator 2 and variable gain amplifier 3 respectively. if the range of the input signal is between -17dB and 30dB, the attenuator typically has a range of -3db to -30db, making the range of the output signal from the attenuator -20dB to OdB. The gain range of the amplifier is 20dB to OdB, bringing the gain at point 8 to OdB. The linearity of the output signal 6 depends on the linearity of the attenuator 2 and the variable gain amplifier 3.
The described apparatus may be modified so as to omit the attenuator 2. In this case, the input signal is applied directly to the amplifier 3, the feedback signal from the feedback being applied solely to the amplifier 3. In this case, the amplifier 3 preferably has a gain range of +20dB to -20dB, bringing the gain at the quiescent level at point 8 to 3dB.
Apparatus according to the invention may be used in a transmitter and/or receiver of a portable handset or a base station in a cellular or cordless radio telephone system.
In Figure 2, the whole of the apparatus illustrated in Figure 1 is shown at 10. The output of the radio transmitter 12 is fed, through a coupler 13, to the inventive apparatus 10, the output 6 of which is fed back to the transmitter 12 to stabilise the power level of the transmitter output fed through an antenna 14.
Figure 3 illustrates the corresponding circuitry for a receiver where the input from an antenna 15 is fed to an amplifier 16 the output of which is coupled (via coupler 17) to the inventive apparatus 10 whose output 6 is fed back to the amplifier 16.

Claims (5)

1. Apparatus for detecting and controlling radio frequency power, comprising input means for the application of a radio frequency signal, a series arrangement to which the radio frequency signal is applied and which includes a controllable amplifier means, a power detector and an error amplifier, and a feedback loop for feeding back to the amplifier means a feedback signal representative of the output of the error amplifier, the feedback signal controlling the gain of the amplifier means to maintain the magnitude of the radio frequency power at the input of the detector at a predetermined level or within a predetermined range.
2. Apparatus according to claim 1, wherein the series arrangement additionally includes a variable attenuator connected between the input means and the controllable amplifier means, the feedback signal being additionally applied to the variable attenuator to control the attenuation level.
3. A method of detecting and controlling radio frequency power comprises applying a radio frequency signal to a series arrangement comprising a controllable amplifier means, a power detector and an error amplifier, feeding back from the error amplifier to the controllable amplifier means a feedback signal which is representative of the output of the error amplifier and which controls the gain of the amplifier means to maintain the magnitude of the radio frequency power at the input of the power detector at a predetermined level or within a predetermined range.
4. A method according to claim 3, wherein the feedback signal is additionally applied to an attenuator to the input of which the radio frequency signal is applied and the output of which supplies the controllable amplifier means, the feedback signal controlling the attenuation level of the attenuator.
5. Apparatus for or a method of detecting and controlling radio frequency power, substantially as herein particularly described with reference to the accompanying drawings.
GB9524584A 1995-12-01 1995-12-01 Detecting and controlling radio frequency power using feedback to attenuator and amplifier Withdrawn GB2307807A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9524584A GB2307807A (en) 1995-12-01 1995-12-01 Detecting and controlling radio frequency power using feedback to attenuator and amplifier

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9524584A GB2307807A (en) 1995-12-01 1995-12-01 Detecting and controlling radio frequency power using feedback to attenuator and amplifier

Publications (2)

Publication Number Publication Date
GB9524584D0 GB9524584D0 (en) 1996-01-31
GB2307807A true GB2307807A (en) 1997-06-04

Family

ID=10784757

Family Applications (1)

Application Number Title Priority Date Filing Date
GB9524584A Withdrawn GB2307807A (en) 1995-12-01 1995-12-01 Detecting and controlling radio frequency power using feedback to attenuator and amplifier

Country Status (1)

Country Link
GB (1) GB2307807A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003075452A2 (en) * 2002-03-01 2003-09-12 Sige Semiconductor Inc. Method of adjusting gain and current consumption of a power amplifier circuit while maintaining linearity

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0405445A2 (en) * 1989-06-27 1991-01-02 Nec Corporation Output waveform control circuit
WO1992022143A1 (en) * 1991-06-03 1992-12-10 Motorola, Inc. Power control circuitry for achieving wide dynamic range in a transmitter
US5179353A (en) * 1991-01-10 1993-01-12 Mitsubishi Denki Kabushiki Kaisha Power control circuit used for both analog/digital dual mode

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0405445A2 (en) * 1989-06-27 1991-01-02 Nec Corporation Output waveform control circuit
US5179353A (en) * 1991-01-10 1993-01-12 Mitsubishi Denki Kabushiki Kaisha Power control circuit used for both analog/digital dual mode
WO1992022143A1 (en) * 1991-06-03 1992-12-10 Motorola, Inc. Power control circuitry for achieving wide dynamic range in a transmitter

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003075452A2 (en) * 2002-03-01 2003-09-12 Sige Semiconductor Inc. Method of adjusting gain and current consumption of a power amplifier circuit while maintaining linearity
WO2003075452A3 (en) * 2002-03-01 2004-04-29 Sige Semiconductor Inc Method of adjusting gain and current consumption of a power amplifier circuit while maintaining linearity
GB2401737A (en) * 2002-03-01 2004-11-17 Sige Semiconductor Inc Method of adjusting gain and current consumption of a power amplifier circuit while maintaining linearity
GB2401737B (en) * 2002-03-01 2006-09-06 Inc Sige Semiconductor Method of adjusting gain and current consumption of a power amplifier circuit while maintaining linearity

Also Published As

Publication number Publication date
GB9524584D0 (en) 1996-01-31

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Legal Events

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)