Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03G—CONTROL OF AMPLIFICATION
  • H03G1/00—Details of arrangements for controlling amplification
  • H03G1/0005—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal
  • H03G1/0088—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal using discontinuously variable devices, e.g. switch-operated
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
  • H03F3/60—Amplifiers in which coupling networks have distributed constants, e.g. with waveguide resonators
  • H03F3/602—Combinations of several amplifiers
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
  • H03F3/72—Gated amplifiers, i.e. amplifiers which are rendered operative or inoperative by means of a control signal
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F2203/00—Indexing scheme relating to amplifiers with only discharge tubes or only semiconductor devices as amplifying elements covered by H03F3/00
  • H03F2203/72—Indexing scheme relating to gated amplifiers, i.e. amplifiers which are rendered operative or inoperative by means of a control signal
  • H03F2203/7239—Indexing scheme relating to gated amplifiers, i.e. amplifiers which are rendered operative or inoperative by means of a control signal the gated amplifier being switched on or off by putting into parallel or not, by choosing between amplifiers and shunting lines by one or more switch(es)

Definitions

• the present invention relates generally to power gain control for a power amplifier and particularly to a wireless communication device, such as a CDMA wireless phone.
• CDMA code-division-multiple-access
• TDMA time-division-multiple access
• RF power output from a mobile unit varies in large dynamic ranges.
• CDMA radiotelephone system multiple signals are transmitted simultaneously at the same frequency. The signals are spread with different digital codes, thus allowing detection of the desired signal while the unintended signals appear as noise or interference to the receiver.
• Spread spectrum systems can tolerate some interference, and the interference added by each new mobile station increases the overall interference in each cell site. Each mobile station introduces a unique level of interference, which depends on its received power level at the cell site.
• the CDMA system uses power control to minimize mutual interference.
• a precise power control is critical to avoid excessive transmitter signal power that is responsible for contributing to the overall interference of the system.
• Power of the individual mobile stations varies with the distance between the mobile station and the base station and the number of other subscriber mobile stations in that base station or sector.
• the power amplifier is biased class AB to reduce power consumption during periods of low transmit power, but power continues to be consumed.
• an isolator is used to isolate the power amplifier from the effects of load impedance in subsequent stages.
• One method to avoid continuous battery draw is to employ a means to bypass the amplifier with switches, and then remove DC power from the Amplifier. This method is illustrated in FIG. 7.
• a power amplifier circuit 8 is shown with a power amplifier 32 and an isolator 55.
• An RF input 12 having an RF-signal to be amplified is connected to a pole of a first switch 20.
• the switch 20 connects the RF-input 12, via path 28, to an input of power amplifier 32.
• the RF-signal is amplified and output to the isolator 55, and then transmitted through the second switch 42 to the RF-output 54 of the power amplifier circuit 8.
• the first switch 20 connects the RF-input 12 to the bypass path 30 and the second switch 42 transmits the signal to the RF-output 54.
• the drawback of this technique is that the amplifier must overcome the added switching loss during times that higher transmit power is required. This can tend to cancel the benefits of bypassing.
• using a switch and an isolator requires more power to operate and is more costly to build.
• FIG. 6 illustrates a prior art power amplifier circuit.
• An analog signal is fed from a driver amplifier 280 through a band pass filter 298 to a first switch 20.
• the switch 20 alternates between a bypass path 30 and an amplifier path 28, wherein a power amplifier 32 amplifies the signal.
• a second switch 42 connects the analog signal from either the bypass path 30 or the output of amplifier 32 to a circulator 55, which routes the signal to the RF-output port 54.
• An object of the present invention is to increase the efficiency of power amplifier usage by using the termination port of an isolator as the combining mechanism for the bypass network, the power amplifier output, and the RF-output port. With this configuration, an output switch becomes unnecessary.
• Another object of the present invention is to provide an improved power amplifier which requires less parts and is less complex to build.
• Yet another object of the present invention is to provide an improved power amplifier which is less costly to build.
• a bypass network is provided to bypass the power amplifier in the circuit when the amplifier gain is not required. During these periods of low power operation, the amplifier is turned off.
• the bypass network consists of a bypass path, and an attenuation path.
• the attenuation path allows variability through use of an external resistor, and the bypass path allows no variability.
• Switches operate to control the flow of the signal to the amplifier, or through either the bypass path or the attenuation path.
• the signal from the bypass network is input to a circulator, which routes the signal to the port connected to the output of the power amplifier. Because the power amplifier is turned off during periods when the bypass is used, it appears to be a very large impedance to the signal.
• the band pass filter is placed in the amplification path such that filtering is bypassed when the power amplifier is bypassed. This reduces the gain step size when changing modes from amplification to bypass.
• the driver amplifier therefore becomes the output amplifier and the filter following the amplifier circuitry operates to remove any undesired spurs.
• FIG. 1 is a plan drawing of the first embodiment of the present invention
• FIG. 2 provides a block diagrammatic representation of a mobile station spread spectrum transmitter in which may be incorporated an efficient power amplifier of the present invention
• FIG. 3 shows an exemplary implementation of an RF transmitter included within the spread spectrum transmitter of FIG. 2;
• FIG. 4 is a plan drawing of a second embodiment of the present invention.
• FIG. 5 is a plan drawing of a third embodiment of the present invention.
• FIG. 6 is a plan drawing of a prior art amplifier circuit
• FIG. 7 is a plan drawing of a prior art power amplifier circuit.
• FIG. 1 is a schematic diagram showing the broad concept of the invention.
• a power amplifier circuit indicated generally by reference numeral 10 comprises a power amplifier 32, a circulator 52, a series of switches, 20, 24 and 42, and bypass paths 34 and 36 around the power amplifier 32.
• An RF-input 12 having an RF-signal to be amplified is connected to a pole of first switch 20.
• the switch 20 connects the RF-input 12, via a path 28, to an input of power amplifier 32.
• the RF- signal is amplified and output from the power amplifier toward the circulator 52.
• the circulator 52 routes the signal to port of the RF-output 54 of power amplifier circuit 10.
• the switch 20 switches the signal path to a bypass network 48 comprising a bypass path 36 and an attenuated path 34.
• switches 24 and 42 switch to a first position such that the signal flows through bypass path 36.
• Switches 24 and 42 can also switch the signal to flow through the attenuated path 34.
• From switch 42 the signal is transmitted to an input of circulator 52.
• the circulator 52 routes the signal to the port connected to the output 50 of the power amplifier 32.
• the output of the power amplifier 50 appears as a high impedance to the signal and thus the signal is reflected back to the circulator 52, which routes the signal to the port of the RF-output 54 of amplifier circuit 10.
• FIG. 2 is a schematic diagram illustrating the use of the power amplifier of the present invention in the signal processing circuitry of a mobile station.
• orthogonal signaling is employed to provide a suitable ratio of signal to noise on the mobile station- to-base station link, or the "reverse" channel.
• Data bits 200 consisting of, for example, voice converted to data by a vocoder, are supplied to an encoder 202 where the bits are convolutionally encoded.
• code symbol repetition may be used such that the encoder 202 repeats the input data bits 200 in order to create a repetitive data stream at a bit rate which matches the operative rate of the encoder 202.
• the encoded data is then provided to block interleaver 204 where it is block interleaved.
• each character is encoded into a Walsh sequence of length 64. That is, each Walsh sequence includes 64 binary bits or "chips", there being a set of 64 Walsh codes of length 64.
• the 64 orthogonal codes correspond to Walsh codes from a 64 by 64 Hadamard matrix wherein a Walsh code is a single row or column of the matrix.
• the Walsh sequence produced by the modulator 206 is provided to an exclusive-OR combiner 208, where it is then "covered” or multiplied at a combiner with a PN code specific to a particular mobile station.
• a "long" PN code is generated at a rate R c by a PN long code generator 210 in accordance with a user PN long code mask.
• the long code generator 210 operates at an exemplary chip rate, R c , of 1.2288 Mhz so as to produce four PN chips per Walsh chip.
• the output of the exclusive -OR combiner 208 is split into identical signals A and B. Signals A and B are input into the exclusive-OR combiners 256 and 254 of FIG. 3 as described below.
• FIG. 3 is a schematic diagram showing an exemplary implementation of the RF transmitter 250 in a mobile station.
• a pair of short PN sequences PN j and PN Q , are respectively provided by a PN j generator 252 and a PN Q generator 254 to exclusive-OR combiners 256 and 258, along with the output A and B from exclusive-OR combiner 208 of FIG. 2.
• the PN j and PN Q sequences relate respectively to in phase (I) and quadrature phase (Q) communication channels, and are generally of a length (32,768 chips) much shorter than the length of each user long PN code.
• the resulting I- channel code spread sequence 260 and Q-channel code spread sequence 262 are then passed through baseband filters 264 and 266, respectively.
• Digital to Analog (D/A) converters 270 and 272 are provided for converting the digital I-channel and Q-channel information, respectively, into analog form.
• the analog waveforms produced by D/A converters 270 and 272 are provided with a local oscillator (LO) carrier frequency signals Cos (2 ⁇ ft) and Sin (2 ⁇ ft), respectively, to mixers 288 and 290 where they are mixed and provided to summer 292.
• the quadrature phase carrier signals Sin (2 ⁇ ft) and Cos (2 ⁇ ft) are provided from suitable frequency sources (not shown). These mixed IF signals are summed in summer 292 and provided to mixer 294.
• Mixer 294 mixes the summed signal with an RF frequency from frequency synthesizer 296 so as to provide frequency upconversion to the RF frequency band.
• the RF may then be bandpass filtered 298 and provided to an efficient parallel stage RF amplifier 10 of the invention.
• the filter 298 removes undesired spurs caused from upconversion 296.
• a similar filter (not shown) may be located following the amplifier circuitry to remove undesired spurs when the circuit is operating in bypass mode. In a bypass mode, the previous driver amplifier becomes the output amplifier and filtering may be necessary to prevent extra spurs from mixing in the non-linearities of the amplifier. This filtering may be accomplished by the similar filter (not shown), thus the band-pass filter 298 may be located in the amplification path as illustrated in FIGS. 4 and 5 discussed below. This also increases flexibility in choosing gain steps.
• FIG. 4 is a second embodiment of the present invention wherein the analog signal is switched 20 between a bypass path 30 and an amplifier path 28.
• band-pass filtering 298 only occurs in the amplifier path 28.
• the signal is band-pass filtered 298 and fed to the power amplifier 32, amplified, and transmitted to the circulator 55, which routes the signal towards the RF-output port 54.
• the circulator 55 is connected to ground through a switch 43 and a resistor 45 and the output port 54 of the circuit when the first switch 20 directs the analog signal through the amplifier path. Accordingly, with this configuration, when reflected or returned RF signals enter the circulator 55 from the direction of the RF-output port 54, the reflected signal is routed by the circulator 55 to ground.
• the second switch 43 connects the bypass path 30 to the circulator 55, and the signal is routed toward the output of the amplifier. This will appear as a high impedance, reflecting the signal back through isolator 55 and to RF-output port 54.
• the power amplifier 32 When high output power is not needed, the power amplifier 32 is turned off and the first switch 20 switches to the bypass path 30, whereby the power amplifier 32 is bypassed and the driver amplifier 280 operates as the power amplifier.
• the second switch 43 connects the bypass path 30 to the circulator 55.
• the input signal in this mode is routed through the bypass path 30 to the circulator 55.
• the signal is routed by the circulator to the output of the power amplifier 32, and is reflected back through the isolator 55 and to the output of the RF-output port 54.
• FIG. 5 shows a third embodiment of the present invention having a driver amplifier 280 and a band-pass filter 298 for filtering the amplified signal before a first switch 20.
• the output from the band pass filter 298 is switched by the first switch 20 which switches between an amplifier path 28 and a bypass path 30.
• the power amplifier 32 in the amplifier path amplifies and transmits the signal to a circulator 55, which routes the signal towards an RF-output port 54.
• the first switch 20 alternates between transmitting the filtered signal to the amplifier path 28 or the bypass path 30.
• a second switch 43 in the bypass path is included which connects the circulator 55 to ground through a resistor 45 in a first mode, and connects the circulator 55 to the bypass path 30 in a second mode.
• the resistor 45 may have a value of 50 ohms, for example.
• any feedback or return signal from the RF-output port 54 is routed to ground when the second switch 43 is in the second mode.
• switch 43 transmits the signal from the bypass path 30 to the circulator 55.
• the circulator 55 routes the signal to the output of the power amplifier, which appears to be a large impedance and reflects most of the signal back to the circulator 55.
• the signal is then routed toward the RF-output port 54. Accordingly, the switch 43 adds isolation due to the fact that the signal cannot be switched to an attenuation path. This embodiment is applicable when only one gain step is desired.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Amplifiers (AREA)
• Mobile Radio Communication Systems (AREA)
• Transmitters (AREA)

Priority Applications (1)

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• 1999
  • 1999-09-22 AU AU61549/99A patent/AU772636B2/en not_active Ceased
  • 1999-09-22 WO PCT/US1999/021758 patent/WO2000018005A1/en not_active Ceased
  • 1999-09-22 AU AU61548/99A patent/AU6154899A/en not_active Abandoned
  • 1999-09-22 CA CA002345089A patent/CA2345089A1/en not_active Abandoned
  • 1999-09-22 JP JP2000571558A patent/JP2002525951A/ja active Pending
  • 1999-09-22 WO PCT/US1999/021757 patent/WO2000018004A1/en not_active Ceased
  • 1999-09-22 EP EP99948347A patent/EP1116325A1/en not_active Ceased
  • 1999-09-22 CN CN99813495.3A patent/CN1326614A/zh active Pending

Non-Patent Citations (1)

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