Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
  • H04W52/04—Transmission power control [TPC]
  • H04W52/52—Transmission power control [TPC] using AGC [Automatic Gain Control] circuits or amplifiers
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B17/00—Monitoring; Testing
  • H04B17/10—Monitoring; Testing of transmitters
  • H04B17/11—Monitoring; Testing of transmitters for calibration
  • H04B17/13—Monitoring; Testing of transmitters for calibration of power amplifiers, e.g. gain or non-linearity

Definitions

• the RF amplifier gain is controlled in incremental steps.
• the system further comprises a transmit power control circuit to generate a step gain control signal, based on the error signal, to control the incremental gain steps of the RF amplifier.
• FIG. 6 is a more detailed functional block diagram of a portion of the block diagram of FIG. 4.
• FIG. 7 is a functional block diagram of another exemplary embodiment of the presently disclosed subject matter.
• the presently disclosed subject matter is directed to a technique to control the transmit power and overcome the inherent nonlinearities of control voltage of a variable gain amplifier.
• a dynamic feedback loop is provided that permits precise control of transmit power without the need for a linearizer.
• FIG. 4 is a functional block diagram of one exemplary embodiment of the presently disclosed subject matter to control transmit power.
• the presently disclosed subject matter is embodied in a system 100 that dynamically adjusts the transmit power using a feedback loop.
• the system 100 includes a receiver portion 104 and a transmitter portion 106.
• the antenna 12 is coupled to the transmitter portion 104 and the receiver portion 106 through a diplexer 108.
• the diplexer 108 permits the receiver portion 104 and the transmitter portion 106 to share a common antenna ⁇ i.e., the antenna 12).
• the diplexer 108 is a common device and need not be described in greater detail herein.
• the receiver portion 104 includes certain elements that have previously been discussed in the functional block diagram of FIG. 1. ' However, for the sake of clarity, the receiver portion 104 in FIG. 4 only includes certain elements from FIG. 1. Specifically, the RSSI is provided to the linearizer 40. The output of the linearizer 40 is coupled to the DAC 42 which, in turn, generates the control voltage V CONT . The control voltage V CONT controls the gain of the VGA 18.
• the output of the linearizer 40 is provided to the transmitter portion 106.
• the transmitter portion 106 is implemented using two different gain control factors.
• the first gain control factor sometimes referred to as an open-loop gain control simply sets the gain of the transmitter at a predetermined level relative to the received signal level. This factor is sometimes referred to in the industry as a "turn- around constant.”
• the transmit power is the received power plus the turn-around constant.
• the turn-around constant is determined by industry standards and can vary based on the particular type of wireless technology.
• the turn-around constant for cellular telephones is set by industry standard to be +73 dB. That is, the transmit power is set to 73 dB above the power of the received signal.
• PCS personal communication systems
• the presently disclosed subject matter is not limited by the particular level for the turn-around constant.
• the system 100 includes a closed-loop power control. While open-loop power control depends only upon the industry standard ⁇ i.e., the turn-around constant) and the received signal strength ⁇ i.e., RSSI), closed-loop power control is based solely on commands from a base station transceiver system (BTS) (not shown).
• BTS base station transceiver system
• the BTS sends commands to the mobile unit ⁇ i.e., the system 100) to increase or decrease transmit power.
• the BTS sends a command to increase the transmit power when the error rate of data received by the BTS is unacceptably high. Conversely, if the error rate is low, the BTS may send a command to the system 100 to decrease the transmit power.
• FIG. 4 illustrates a transmit power reference 114, which represents both the open-loop power control signal ⁇ i.e., the turn-around constant) and the closed-loop power control signals based on commands received from the BTS (not shown).
• the output of the linearizer 40 which is indicative of the received signal strength, is provided as an input to a summer 110.
• the transmit power reference 114 provides a signal corresponding to the selected turn-around constant, and may be an AC signal or a DC signal depending on the particular circuit implementation.
• the signal input to the VGA 122 comes from transmitter circuitry that, for the sake of clarity, is not illustrated in FIG. 4.
• the transmitter circuitry which may typically include a microphone, vocoder, and transmitter modulator, operate in a conventional manner to provide an input signal that will actually be transmitted by the system 100.
• the output of the RF power amplifier 124 is also provided as an input to the transmit power processor 116.
• the transmit power processor 116 generates signals indicative of the actual transmit power and provides that indicator as negative feedback to the transmitter power control circuit 120.
• the transmitter portion 106 includes dynamic power adjustments that are extremely accurate and which eliminates the linearization process required in conventional wireless systems.
• the output of the adder 118 (see FIG. 4) is coupled as an input to the transmit power control circuit 120.
• the signal from the adder 118 includes the desired transmit power signal and the negative feedback signal.
• the signal from the adder 118 which is essentially an error signal, is provided to an integrator 144.
• the integrator 144 averages out the error signal and also controls the response time of the feedback loop. As those skilled in the art can appreciate, a longer integration time for the integrator 144 results in slower response time for the feedback loop.
• the actual selection of the integrator time is a matter of design choice that is within the knowledge of one skilled in the art based on the present disclosure.
• the step gain control 148 may increase the transmit power of the RF power amplifier 124 to, by way of example, +20 dBm.
• the output of the DAC 146 is adjusted correspondingly to provide any additional gain that is required beyond the gain of the power amplifier 124.
• VGA 122 may be implemented as a series of amplifier gain stages that are coupled in series and controlled by the signal generated by the transmit power control circuit 120.
• the two stages of amplification illustrated in FIG. 4 and controlled by the DAC 146 and step gain control 148, respectively, may be combined into a single amplification stage.
• the step gain control 148 may use a different step size or a different number of gain steps. The actual step size may be based on the dynamic range of the DAC 146.
• the presently disclosed subject matter is not limited by the specific architecture of the variable gain amplifier 122, RF power amplifier 124, and the specific control signals associated therewith.
• the circuit of FIG. 4 provides a dynamic feedback loop that completely eliminates the need for linearization in the transmitter of a wireless device.
• This approach eliminates a large number of calibration steps that must be performed on each wireless device during the manufacturing process.
• the system 100 greatly increases productivity of the manufacturing process and may reduce the overall costs of the wireless device since costly and time-consuming calibration steps have been eliminated.
• the transmitter portion 106 has a linearizer, but utilizes the calibrated receiver portion 104 to eliminate the need for external test equipment that would otherwise be required for calibration of the transmitter portion of the wireless device.
• the un-calibrated output of the transmitter portion 106 is coupled to the calibrated receiver portion 104 so that the receiver portion can be used to accurately measure the actual transmitted power levels and allow linearization of the transmitter portion.
• FIG. 7 This embodiment is illustrated in the functional block diagram of FIG. 7.
• the demodulator 19 of FIG. 1 includes components, such as mixers 20 and 22, low-pass filters 24 and 26, and the like.
• those components are illustrated in the functional block diagram of FIG. 7 as the demodulator 19.
• the AGC 31, which comprises a number of components illustrated in FIG. 1, are merely shown in block diagram form as the AGC 31.
• FIG. 7 illustrates additional components in the transmitter portion 106 that are not illustrated in the functional block diagram of FIG. 4.
• FIG. 7 illustrates a mixer 160 and local oscillators 162 that modulate data, such as voice data from a vocoder circuit (not shown) to generate the desired radio frequencies.
• the output of the mixer 160 is coupled to the VGA 122 whose output is coupled, in turn, to the RF power amplifier 124.
• the output of the RF power amplifier 124 is coupled to the diplexer 108 via the isolator 126, as described above.
• the system 100 of FIG. 7 includes a second mixer 164 coupled to the output of the variable gain amplifier 122 and the local oscillators 162.
• the mixer 164 shifts the frequency of the transmitted output signal to IF frequencies compatible with the receiver portion 104.
• a typical wireless communication device includes a single master oscillator from which the various local oscillator frequencies are derived.
• the transmitter and receiver operate at different frequencies that are offset by a predetermined amount that is set by industry standards. For example, in a cellular telephone operation, the transmitter and receiver are offset by 45 MHz.
• the circuitry used to derive the local oscillator frequencies to produce the desired offset is known in the art and need not be described herein.
• the local oscillators 162 provide the necessary frequencies to the mixers 160 and 164, respectively.
• the local oscillators 162 provide one frequency to the mixer 160 for the transmitter portion 106 and provide a second frequency to the mixer 164 to convert the transmitted signal to the receiver IF frequency.
• the output of the mixer 164 is coupled through a band pass filter 168 to a VGA 170.
• the band pass filter 168 operates in a conventional manner as an IF filter. It should be noted that the output of the band pass filter 168 is coupled to the input of the VGA 170 via a switch 172, such as an electronic switch.
• the operation of the switch 172 which functions as a coupling circuit to couple the transmitter portion 106 to the receiver portion 104, will be described in greater detail below.
• the output of the VGA 170 and the VGA 18 are combined by a summer 176.
• the system 100 utilizes the calibration of the receiver portion 104 to calibrate the transmitter portion 106.
• the calibration of the receiver portion 104 is performed in a manner known in the art and described above.
• the switch 172 is deactivated so that no output from the band pass filter 168 is provided to the VGA 170.
• the switch 172 is activated such that the signal from the band pass filter 168 is now provided as an input to the VGA 170.
• the transmitter portion 106 is calibrated during the manufacturing process in the following manner.
• Control signals set the gain of the VGA 122 at the predetermined transmit power level.
• the signal from the output of the VGA 122 is mixed with the local oscillator signal 162 by the mixer 164 to produce an output signal compatible with the frequencies of the receiver portion 104.
• the output of the mixer 164 is provided to the VGA 170 via the band pass filter 168 and the switch 172.
• the system 100 utilizes the previously calibrated receiver portion 104 to accurately determine the received signal level, which is proportional to the transmitted power level from the VGA 122. If the transmitted signal level is greater than or less than the desired transmitted power level, the error is detected by the calibrated receiver circuitry and the deviation is stored in the form of interim results 180. The interim results the process may be repeated for numerous transmitter gain steps and different transmitter frequencies. In addition, calibration processes may be performed for different power supply levels and different temperature settings to provide an accurate characterization of the transmitter portion 106.
• the interim results 180 are used to generate a transmitter linearizer 182.
• the interium results 180 indicate an error difference between the desired transmit power level and the actual transmit power level. These interium data results are used to create the transmitter linearizer 182 and effectively determine the actual gain control curve for the VGA 122.
• the transmitter linearizer 182 operates in a manner similar to that described above with respect to that described above with respect to the receiver linearizer 40. That is, the transmitter linearizer 182 breaks the variable gain curve for the VGA 122 into a plurality of piece-wise linear portions that describe the actual gain characteristics and provide sufficient gain resolution. Whenever the system 100 calls for a particular gain setting for the transmitter portion 102, the transmitter linearizer 182 is used to select the actual control voltage for the variable gain amplifier 122. It should be noted that the switch 172 is deactivated during normal operation of the wireless device. In the deactivated position, the switch 172 provides a desired degree of isolation between the receiver portion 104 and the transmitter portion 106.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Nonlinear Science (AREA)
• Electromagnetism (AREA)
• Transmitters (AREA)
• Transceivers (AREA)
• Mobile Radio Communication Systems (AREA)
• Control Of Amplification And Gain Control (AREA)

Priority Applications (4)

Applications Claiming Priority (4)

Publications (2)

Family

ID=26872885

Family Applications (1)

Country Status (7)

Cited By (8)

Families Citing this family (189)

Family Cites Families (29)

• 2002
  • 2002-06-20 US US10/177,057 patent/US6819938B2/en not_active Expired - Fee Related
  • 2002-06-25 JP JP2003507979A patent/JP4095020B2/ja not_active Expired - Fee Related
  • 2002-06-25 WO PCT/US2002/020377 patent/WO2003001701A2/en not_active Ceased
  • 2002-06-25 CA CA002451320A patent/CA2451320A1/en not_active Abandoned
  • 2002-06-25 RU RU2004101967/09A patent/RU2297714C2/ru not_active IP Right Cessation
  • 2002-06-25 AU AU2002322339A patent/AU2002322339A1/en not_active Abandoned
  • 2002-06-25 EP EP02756324A patent/EP1400033A2/en not_active Withdrawn
• 2004
  • 2004-10-12 US US10/964,404 patent/US7076266B2/en not_active Expired - Fee Related
  • 2004-10-12 US US10/964,118 patent/US8457570B2/en not_active Expired - Fee Related

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