WO2002103924A2 - Power control for non-constant envelope modulation - Google Patents
Power control for non-constant envelope modulation Download PDFInfo
- Publication number
- WO2002103924A2 WO2002103924A2 PCT/GB2002/002897 GB0202897W WO02103924A2 WO 2002103924 A2 WO2002103924 A2 WO 2002103924A2 GB 0202897 W GB0202897 W GB 0202897W WO 02103924 A2 WO02103924 A2 WO 02103924A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- signal
- power control
- control loop
- power
- modulation
- Prior art date
Links
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
- H03G3/3047—Automatic control in amplifiers having semiconductor devices in high-frequency amplifiers or in frequency-changers in modulators, frequency-changers, transmitters or power amplifiers for intermittent signals, e.g. burst signals
-
- 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
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
- H04W52/52—TPC using AGC [Automatic Gain Control] circuits or amplifiers
Definitions
- the present invention relates to a technique for power control in transmitters utilising non-constant envelope modulation techniques, and particularly but not exclusively to such transmitters forming part of a wireless communications system.
- Power control loops such as provided in wireless communication systems, are typically provided to control and maintain output power at a desired level, and to control transient responses when ramping up or down.
- a framed structure comprises a number of time slots (or channels) .
- a wireless communications system using TDMA for example a GSM (global system for mobile telecommunications) system, transmits and receives information over each assigned slot or channel.
- GSM global system for mobile telecommunications
- Each channel of a frame is assigned to a different user with transmission (uplink) information on one frequency band and reception (downlink) information on a separate frequency band communicated over each channel.
- Each channel is specified to ramp-up to a required power level for burst transmissions and ramp-down to a required power level in a predetermined amount of time, called a burst.
- a burst has a ramp-up phase or cycle, an operational phase or cycle, and a ramp-down phase or cycle.
- GSM specifications also require that the power at the start and end of a burst must be at a specified minimum level and that the transition from the minimum power level to the final required power level must be completed in a specified time window.
- the time frame for ramping up and down is specified in order to reduce the generation of transient side bands and interference on adjacent channels.
- the operation of a typical power control loop is divided into an open loop mode and a closed loop mode.
- the power control loop runs in open loop mode until the output of the power amplifier has reached a predetermined level, referred to as the switching point.
- an error signal is produced using the difference of a supplied reference signal and the output of a detector which samples the signal at the output of the control loop.
- An integrator is used to produce a control voltage from the error signal, which is used to control a variable attenuator as a means to control power levels when ramping and during transmission bursts.
- Figure 1(a) depicts a graph of the power output of a power amplifier controlled by a conventional power control loop.
- section A the power output rises to the appropriate level.
- section B the power output is held substantially steady by the power control loop.
- section C the power output falls.
- Figure 1 (b) depicts a graph of the power output of a power amplifier transmitting a non-constant envelope modulated burst, such as an AM burst.
- a non-constant envelope modulated burst such as an AM burst.
- the power output rises to the appropriate level.
- section B the power output fluctuates according to the amplitude of the signal being transmitted.
- section C the power output falls .
- a conventional power controller would tend to level out the variations in power due to the AM burst. Such a situation is unacceptable for advanced wireless transmissions using AM.
- a known solution allowing a conventional power control loop to be used with amplitude modulation transmissions is to add a sample and hold circuit to the power control loop. Power levels are sampled during ramping and the level is held steady during an AM burst.
- Figure 1(b) illustrates a disadvantage of this approach when applied to advanced modulation schemes, known as gain tilt. Gain tilt can occur during a transmission burst.
- Figure 1(b) depicts the gain tilt effect, showing the expected gain level at the end of the burst and the actual gain level due to gain tilt at the end of a burst.
- the sample and hold circuitry of a conventional power controller works on an assumption that gain does not change during a burst and does not attempt to control gain tilt during the burst.
- a power level detected at the output of the amplifier is compared to a reference signal to give an error signal used for attenuation of the output signal.
- the power level detected at the output of the amplifier is compared to the modulated RF signal to be transmitted to give the error signal used for attenuation of the output signal.
- the present invention provides a technique for control of transmitter power which preserves modulation characteristics, and which is thus particularly advantageous when utilised in systems with non-constant modulation schemes.
- This improvement is achieved by combining the power level control signal with the modulation envelope of the modulated RF carrier signal during a transmission burst. Further improvement may be obtained by reducing the bandwidth of the control system during the burst.
- a method of control in a power control loop comprising the steps of: amplifying a non-constant envelope modulation signal to thereby produce an output signal; combining a power level control signal with a signal representing the envelop of modulation; comparing the combined signal to a signal representing the power level of the output signal to thereby produce a comparison signal; and attenuating the amplified signal in dependence on said comparison signal.
- the power control loop may have at least a ramp-up cycle and an operational cycle. During the operational cycle the bandwidth of the power control loop may be reduced. The method may be implemented during all cycles of the power control loop.
- the power control loop may further include a ramp-down cycle.
- the technique of the invention is applied during all phases of operation, and not just during the burst.
- the technique is used during the ramp-up phase.
- the present invention does not suffer from the drawbacks of the prior art technique of WO 01/03292, as discussed hereinabove.
- the present invention provides a method of control in a power control loop, comprising the steps of: ramping up an output signal during a first cycle; and maintaining a substantially constant output signal during a second cycle, wherein in said first and second cycles the method further comprises: amplifying a non-constant envelope modulation signal to thereby produce the output signal; combining a power level control signal with a signal representing the envelop of modulation; comparing the combined signal to a signal representing the power level of the- output signal to thereby produce a comparison signal; and attenuating the amplified signal in dependence on said comparison signal.
- the present invention still further provides in another aspect a power control loop, comprising: an amplifier for amplifying a non-constant envelop modulation signal to thereby produce an output signal; a combiner for combining a power level control signal with a signal representing the envelop of modulation; a comparator for comparing the combined signal to a signal representing the power level of the output signal to thereby produce a comparison signal; and an attenuator for attenuating the signal to be amplified in dependence on said comparison signal.
- Figure 1(a) illustrates a graph of the power output of a power amplifier controlled by a conventional power control loop
- Figure 1(b) illustrates a graph of the power output of a power amplifier transmitting a non-constant envelope modulated signal
- FIG. 2 illustrates a block diagram of a power control loop in accordance with a preferred embodiment of the present invention. Description of Preferred Embodiment
- the power control system includes a variable attenuator 500, a power amplifier 502, a detector/lineariser comprising a diode 528, a comparator formed by resistors 506 and 526, a mixer 504, an error amplifier comprising operational amplifier 510 and resistor 508, a bandwidth switch comprising resistor 512 and switch 516, a loop filter comprising operational amplifier 522, resistor 518 and capacitor 520, and a buffer 524.
- the variable attenuator 500 receives as a first input on line 530 a modulated RF carrier signal to be transmitted. As will be described in further detail hereinbelow the variable attenuator receives as a second input an attenuator control signal on line 540.
- the modulated RF carrier signal after attenuation in the variable attenuator 500, is applied to the power amplifier 502. An amplified output signal is then generated on line 536.
- the input to the detector/lineariser on line 538 detects a sample of the output signal on line 536, and generates a detected voltage signal Vdet on line 542.
- the mixer 504 receives as a first input a power level control signal Vc on line 532, and as a second input the envelope signal of the modulated RF carrier on line 534.
- the signal Vc is generated within a digital ASIC which provides all the control signals for the transmitter.
- the modulation envelope, provided on line 534, is also generated within such a digital ASIC.
- the ASIC preferably includes the modulator, and hence it is easy to generate an envelope signal of the modulation directly.
- the signals on lines 532 and 534 - Vc and the modulation envelope - are preferably both digital words.
- the signal Vc(e) on line 544 may be generated by passing the output from the mixer into a digital-to-analogue converter to produce an analogue voltage.
- Such an implementation is preferred because it is relatively easy to implement the mixing process digitally.
- it is possible to implement the generation of Vc(e) using a mixing process if Vc and the modulation envelope are both analogue quantities.
- the modulation envelope could be generated by detecting the amplitude of the modulated carrier at IF or RF.
- clearly producing Vc (e) by processing digital quantities is more efficient than using analogue quantities.
- the mixer 504 multiplies the power level control signal Vc with the envelope signal and thereby generates a composite level control signal Vc(e) on line 544.
- the envelope of the composite level control signal Vc(e) tracks the envelope of the modulated RF carrier.
- the composite level control signal Vc(e) on line 544 is compared to the detected voltage level Vdet on line 542 at the input to the error amplifier.
- the error amplifier output is amplified and applied to control input of the variable gain RF attenuator 500, via the bandwidth switch, loop filter and buffer.
- the error amplifier output thus adjusts the transmitter output level on line 536.
- the power level control signal Vc is ramped at the start and end of each 'timeslot, and sets the average RF power level during the burst.
- the value of Vc, at the input to the mixer 532 sets the average RF level. Due to the use of the modulation envelope signal at the input to the mixer 504, the average power is controlled without distorting the modulation envelope.
- the instantaneous value of the power level control signal tracks the envelope of the modulated RF signal, and closed-loop power control is therefore possible without distortion of the RF modulation envelope.
- the technique of the present invention is therefore particularly advantageous in systems utilising non-constant modulation techniques, such as EDGE systems.
- the bandwidth switch is ⁇ opened' during the active part of the burst, thereby reducing the control loop bandwidth.
- the control-loop bandwidth is reduced during the useful part of the burst which limits the sensitivity of the control-loop to timing differences present in practical systems.
- the bandwidth switch reduces the sensitivity of the control loop to timing differences.
- the minimum control loop bandwidth required to track the ramp-up and ramp-down of the power level control signal (at the start and end of the burst) is approximately 50kHz.
- systems are designed with a maximum bandwidth of 200kHz to 300kHz, because of variations in loop bandwidth over the operating range of the variable attenuators.
- the recommended loop bandwidth during the burst is approximately 10kHz, thus a bandwidth reduction ratio of 20 is implemented.
Abstract
Description
Claims
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU2002314336A AU2002314336A1 (en) | 2001-06-20 | 2002-06-19 | Power control for non-constant envelope modulation |
AT02740906T ATE303018T1 (en) | 2001-06-20 | 2002-06-19 | POWER CONTROL FOR NON-CONSTANT ENVELOPE MODULATION |
DE60205757T DE60205757T2 (en) | 2001-06-20 | 2002-06-19 | POWER CONTROL FOR NON-CONSTANT SLEEVE MODULATION |
US10/481,726 US7289777B2 (en) | 2001-06-20 | 2002-06-19 | Power control for non-constant envelope modulation |
EP02740906A EP1415410B1 (en) | 2001-06-20 | 2002-06-19 | Power control for non-constant envelope modulation |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB0115082.0 | 2001-06-20 | ||
GBGB0115082.0A GB0115082D0 (en) | 2001-06-20 | 2001-06-20 | Power control for non-constant envelope modulation |
Publications (2)
Publication Number | Publication Date |
---|---|
WO2002103924A2 true WO2002103924A2 (en) | 2002-12-27 |
WO2002103924A3 WO2002103924A3 (en) | 2004-03-04 |
Family
ID=9917003
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB2002/002897 WO2002103924A2 (en) | 2001-06-20 | 2002-06-19 | Power control for non-constant envelope modulation |
Country Status (9)
Country | Link |
---|---|
US (1) | US7289777B2 (en) |
EP (1) | EP1415410B1 (en) |
CN (1) | CN1524342A (en) |
AT (1) | ATE303018T1 (en) |
AU (1) | AU2002314336A1 (en) |
DE (1) | DE60205757T2 (en) |
ES (1) | ES2244786T3 (en) |
GB (1) | GB0115082D0 (en) |
WO (1) | WO2002103924A2 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8391814B2 (en) | 2007-12-18 | 2013-03-05 | Intel Mobile Communications GmbH | Power control loop, transmitter with the power control loop and method for controlling output power of a transmitter device |
Families Citing this family (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7570709B2 (en) * | 2001-03-08 | 2009-08-04 | Siemens Aktiengesellschaft | Automatic transmit power control loop with modulation averaging |
US7385536B2 (en) * | 2004-12-14 | 2008-06-10 | Texas Instruments Incorporated | Methods and circuits for output of sample-and-hold in pipelined ADC |
US7148749B2 (en) * | 2005-01-31 | 2006-12-12 | Freescale Semiconductor, Inc. | Closed loop power control with high dynamic range |
US7522676B2 (en) * | 2006-02-06 | 2009-04-21 | Nokia Corporation | Method and system for transmitter envelope delay calibration |
CN101578763B (en) * | 2007-01-12 | 2012-01-04 | 松下电器产业株式会社 | Transmission power control method and transmission device |
WO2008084850A1 (en) * | 2007-01-12 | 2008-07-17 | Panasonic Corporation | Polar modulation transmission device and transmission power control method |
US8081710B2 (en) | 2007-11-08 | 2011-12-20 | Pine Valley Investments, Inc. | System and method for corrected modulation with nonlinear power amplification |
US8233852B2 (en) * | 2008-04-04 | 2012-07-31 | Pine Valley Investments, Inc. | Calibration techniques for non-linear devices |
US8463209B1 (en) * | 2009-07-27 | 2013-06-11 | Rf Micro Devices, Inc. | Pre-charge of a power amplifier pedestal voltage |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5697074A (en) * | 1995-03-30 | 1997-12-09 | Nokia Mobile Phones Limited | Dual rate power control loop for a transmitter |
WO2001003292A1 (en) * | 1999-07-02 | 2001-01-11 | Nokia Networks Oy | Power control for non-constant envelope modulation |
WO2001010013A1 (en) * | 1999-07-29 | 2001-02-08 | Tropian, Inc. | High-efficiency modulating rf amplifier |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH04103207A (en) * | 1990-08-22 | 1992-04-06 | Mitsubishi Electric Corp | Automatic power controller for linear modulation wave |
GB9219825D0 (en) | 1992-09-18 | 1992-10-28 | Philips Electronics Uk Ltd | Power amplifier and a transmitter including the power amplifier |
FI97179C (en) * | 1994-06-15 | 1996-10-25 | Nokia Mobile Phones Ltd | Controlling the output power of a pulsed transmitter and shaping the power envelope curve |
GB9825414D0 (en) | 1998-11-19 | 1999-01-13 | Symbionics Limted | Linear RF power amplifier and transmitter |
FI982561A (en) | 1998-11-26 | 2000-05-27 | Nokia Networks Oy | Power control method and power control system |
NZ338097A (en) | 1999-09-29 | 2001-05-25 | Tait Electronics Ltd | Digitally controlled envelope elimination and restoration phase lock loop radio frequency amplifier |
WO2001022575A1 (en) | 1999-09-23 | 2001-03-29 | Wey Chia Sam | Method and apparatus for providing a constant loop bandwidth of a power control loop system at different power levels |
DE10056472A1 (en) * | 2000-11-15 | 2002-05-29 | Infineon Technologies Ag | Polar loop transmission circuit has oscillator producing HF signal depending on phase comparison, amplitude modulator, feedback path, amplifier between amplitude modulator, mixer |
-
2001
- 2001-06-20 GB GBGB0115082.0A patent/GB0115082D0/en not_active Ceased
-
2002
- 2002-06-19 WO PCT/GB2002/002897 patent/WO2002103924A2/en not_active Application Discontinuation
- 2002-06-19 ES ES02740906T patent/ES2244786T3/en not_active Expired - Lifetime
- 2002-06-19 DE DE60205757T patent/DE60205757T2/en not_active Expired - Fee Related
- 2002-06-19 AT AT02740906T patent/ATE303018T1/en not_active IP Right Cessation
- 2002-06-19 EP EP02740906A patent/EP1415410B1/en not_active Expired - Lifetime
- 2002-06-19 US US10/481,726 patent/US7289777B2/en not_active Expired - Fee Related
- 2002-06-19 AU AU2002314336A patent/AU2002314336A1/en not_active Abandoned
- 2002-06-19 CN CNA028123387A patent/CN1524342A/en active Pending
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5697074A (en) * | 1995-03-30 | 1997-12-09 | Nokia Mobile Phones Limited | Dual rate power control loop for a transmitter |
WO2001003292A1 (en) * | 1999-07-02 | 2001-01-11 | Nokia Networks Oy | Power control for non-constant envelope modulation |
WO2001010013A1 (en) * | 1999-07-29 | 2001-02-08 | Tropian, Inc. | High-efficiency modulating rf amplifier |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8391814B2 (en) | 2007-12-18 | 2013-03-05 | Intel Mobile Communications GmbH | Power control loop, transmitter with the power control loop and method for controlling output power of a transmitter device |
Also Published As
Publication number | Publication date |
---|---|
DE60205757D1 (en) | 2005-09-29 |
ES2244786T3 (en) | 2005-12-16 |
GB0115082D0 (en) | 2001-08-15 |
DE60205757T2 (en) | 2006-01-12 |
WO2002103924A3 (en) | 2004-03-04 |
US20040166885A1 (en) | 2004-08-26 |
AU2002314336A1 (en) | 2003-01-02 |
US7289777B2 (en) | 2007-10-30 |
EP1415410B1 (en) | 2005-08-24 |
CN1524342A (en) | 2004-08-25 |
ATE303018T1 (en) | 2005-09-15 |
EP1415410A2 (en) | 2004-05-06 |
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