MXPA97006993A - Power control circuit for a radiofrecuen transmitter - Google Patents

Abstract

The present invention relates to a gain controller (130) for a radio frequency (RF) transmitter (102) that controls the power level of a signal (123) transmitted within a predetermined range of output power levels. The gain controller (130) provides the first gain control signal (131) and the second gain control signal (133), in response to a control signal (150) of the output power level. The first gain control signal (131) controls the gain of a variable gain first stage (144) to vary the power level of the transmission signal (115) to an intermediate frequency, which causes the power level of The output of the transmission signal (123) varies over a lower range of the predetermined range of output power levels. The second gain control signal (133) controls the gain of the second variable gain stage (120) to vary the power level of the transmission signal (121) to a radio frequency which causes the output power level of the transmission signal (123) varies over a higher range of the predetermined range of output power levels. The power control circuit (130) is advantageously used in a radiotelephone (100) with code division multiple access (CDMA) to provide power control over a range of 85 dB of power levels while reducing the minimum noise emissions from the sideband, the current consumption and the complexity of the transmitter (102) of

Description

POWER CONTROL CIRCUIT FOR A RADIO FREQUENCY TRANSMITTER FIELD OF THE INVENTION The present invention relates generally to radiofrequency transmitters and, more particularly, to a power control circuit for a radio frequency (RF) transmitter that can be used advantageously in a multiple access radiotelephone by division of code (CDMA).

BACKGROUND OF THE INVENTION The performance requirements for a code division multiple access cellular subscriber (CDMA) mobile station are specified in the document of the Electronic Industries Association EIA / TIA / IS-95"Mobile Station - Land Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System ", published in July 1993 (referred to herein as "Standard IS-95"). Standard IS-95 specifies a minimum dynamic range for the control of the output power of a transmission signal and the minimum allowable amount of noise emissions from the transmission sideband. The minimum dynamic range for the control of the specified output power for a mobile station of P1354 / 97MX Class III is 73 dB (-50 dBm to +23 dBm). When considering the tolerances of the transmission gain, the required dynamic range is 85 dB. The emission specification of the transmission sideband demands a limit dBc that is applicable to a higher output power and an emission floor or bottom that is applicable to lower or lower levels of output power. For frequency shifts from the carrier frequency between 900 kHz and 1.98 MHz, the maximum emission must be less than that which is greater than 42 dBc / 30 kHz with respect to the desired transmission power in a bandwidth of 1.23 MHz or both. -60 dBm / 30 kHz as -55 dBm / 1 MHz. For carrier frequency shifts greater than 1.98 MHz, the maximum emission must be less than greater than -54 dBc / 30 kHz with respect to the power of the carrier. desired transmission in a bandwidth of 1.23 MHz or both -60dBm / 30kHz and -55 dBm / 1 MHz. To produce high-quality mobile stations, a margin of 10 dB is added to the bandwidth emission specification. Therefore, the design objective for the floor or base of the emissions (-60dBm / 30kHz and -55dBm / l MHz) is -70dBm / 30kHz and -65dBm / l MHz. In other cellular systems (AMPS, NAMPS , NADC, GSM, PDC, etc.), the dynamic range for the control of P1354 / 97MX output power required for mobile stations is usually much lower (ie 20 to 30 dB) than the dynamic range for the control of the required output power (ie 85 dB) for mobile stations CDMA. In these other systems, the dynamic range required to control the output power is usually supplied by controlling a variable gain stage, such as a variable gain power amplifier (PA), which amplifies a radio frequency (RF) signal or by controlling a voltage controlled attenuator (VCA) that attenuates an intermediate frequency (IF) signal. Individually, these schemes do meet the requirement of the dynamic range to control the output power or, the requirement of sideband emission for the CDMA mobile stations. A good performance of the transmission sideband emission is obtained when the gain control circuitry for the RF signal is placed or placed near the antenna. Unfortunately, under these conditions, it is not easy to achieve 85 dB gain control of the RF signal without providing very good protection and grounding. A range of gain control of 85dB can be achieved in a transmission signal in the IF range or range which is normally 100 to 200 MHz. However, P1354 / 97MX control a dynamic range of 85 dB of power control in the IF range is disadvantageous, because it does not optimize the requirement of side band noise emissions. To meet the requirement of sideband noise emissions, the gain that follows the gain control stage must be reduced to the minimum in order to reduce the noise of the sideband produced in the transmitter, at low power output levels. This requires a higher level of output taken from the transmission IF gain. This implies a high freedom for the transmission IF gain stages which results in a higher current consumption. For example, the SONY CXA3002N transmission gain control amplifier has a dynamic range of 85 dB only at intermediate frequencies, a third-order intersection point with + 10dBm output (0IP3) and a current draw of 35 mA. Another disadvantage of having the 85 dB gain control stage control the transmission signal in the IF range is the susceptibility to spurious leads and noise generated in other sections of the radius. For example, if the maximum output power of each stage controlled by gain is -5 dBm for an adequate release and the worst case of maximum gain that follows the stage controlled by gain is 35 dB, the noise and the P1354 / 97MX maximum parasitic derivations captured at this point should be less than -105dBm / 30kHz as -90dBm / l MHz to pass the floor or emission background with a good margin. It is not possible to reach these levels, however, this would probably require the use of extra armor and several tables and / or IC revisions. Even if the degree of isolation is achieved, the current consumption would still be higher than desired. In accordance with the foregoing, there is a need for a power level control circuit for an RF transmitter that provides a wide dynamic range to control the output power while minimizing sideband noise emissions, the current consumption and the complexity of the RF transmitter.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates a block diagram of a radiotelephone adapted for use in a code division multiple access (RF) radio frequency (CDMA) cellular telephone system; Figure 2 illustrates a block diagram of a gain controller shown in the radiotelephone of Figure 1; Figure 3 illustrates a graph, which combines the P1354 / 97MX graphs shown in Figures 3 and 4, showing the total gain against the output power of a transmitter shown in the radio telephone of Figure 1, Figure 4 illustrates a graph showing the gain versus the power of output for a first variable gain stage of a transmitter shown in the radiotelephone of Figure 1; Figure 5 illustrates a graph showing the gain against the output power of a second variable gain stage of a transmitter shown in the radiotelephone of Figure 1.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a block diagram of a radiotelephone 100 adapted for use in a code division multiple access radio frequency (RF) cellular telephone system (CDMA). In the preferred embodiment of the invention, the radiotelephone 100 is a cellular radiotelephone. The radiotelephone 100 can take many forms that are well known in the art, such as a vehicle mounted unit, a portable unit or a transportable unit. In accordance with the preferred embodiment of the present invention, the cellular radiotelephone is a code division multiple access (CDMA) cellular radiotelephone designed to be P1354 / 97MX compatible with a CDMA cellular radiotelephone system, as described in the aforementioned IS-95 standard. The radiotelephone 100 generally includes a transmitter 102, a receiver 104, a radiotelephone controller 105 and an antenna 106. The receiver 104 generally includes a reception bandpass filter 140 (Rx), a signal receiver 142, a decoder and demodulator 144 and an information sink 146. The controller 105 of the radiotelephone generally includes a microprocessor, a read-only memory and a random access memory. Generally, receiver 104, controller 105 of the radiotelephone and antenna 106 individually are well known in the art, as taught in a radiotelephone having the model # SUF1712, U.S. Patent No. 5,321,847 and the above mentioned Standard IS-95, each incorporated herein by reference. The transmitter 102 generally includes an information source 108, an encoder and modulator 110, a local oscillator 112 of intermediate frequency (IF) of transmission (Tx), a first stage of variable gain 114, an upconversion stage 116, an oscillator local radio frequency (RF) 118 (Tx), a second variable gain stage 120, a final stage 122 and a gain controller 130. The conversion stage Upward P13S4 / 97MX 116 generally includes a upconversion mixer 160 and a first RF bandpass filter 162. The final stage 122 generally includes a driver amplifier 170, a second RF bandpass filter 172, a power amplifier 174 and a third RF bandpass filter 176. The transmission alignment for the upconversion stage 116 and the final stage 122 is described as an example only. Other transmission alienations compatible with the present invention may be implemented, as is well known to those skilled in the art of transmitter design. The encoder portion 110 of the transmitter 102 and decoder and demodulator 144 of the receiver 104 are generally incorporated into a specific application integrated circuit (ASIC) as described in "DMA Mobile Station modem ASIC", Proceedings of the IEEE 1992 Custom Integrated Circuits Conference, section 10.2, pages 1-5, and as taught in a document entitled "The CDMA Digital Cellular System as ASIC Overview," Proceedings of the IEEE 1992 Custom Integrated Circuits Conference, section 10.1, pages 1-7 (incorporated herein by reference). During the operation, the radio transmitter 102 receives information from the information source P1354 / 97MX 108, normally as voice or data. The information source provides an information signal 109 that will be encoded and modulated by the encoder and the modulator 110. The local oscillator IF Tx 112 generates a local oscillator signal Tx IF which, for example, has a frequency of 150 MHz. The encoder and modulator 110 modulates the local oscillator signal 111 Tx in response to the information signal 109 to produce a modulated signal 113. The center frequency of the modulated signal 113 is referred to as the IF frequency Tx and is, for example, 150 MHz. The modulated signal 113 is amplified by a variable gain stage 114 having a gain controlled by a gain control signal 131 to produce an IF signal Tx 115. The local RF oscillator Tx 118 generates an oscillator signal 117 local RF Tx that has a frequency of 150 MHz higher than the desired RF Tx center frequency (for example, from 824 to 894 MHz). The frequency of the upconversion stage 116 translates the IF signal Tx 115 from the center frequency IF Tx to the desired RF center frequency Tx and filters this signal using the first RF bandpass filter 162 to produce a first RF signal Tx 119. The first RF signal Tx 119 is amplified by a second variable gain stage 120 having a gain controlled by a gain control signal 133 to produce a second RF signal Tx 121.

P1354 / 97MX The second RF signal Tx 121 is amplified and filtered by the final stage 122 to produce the output signal Tx 123 that will be transmitted by the antenna 106. In the preferred embodiment, the first variable gain stage 114 and the second variable gain stage 120 are variable voltage controlled attenuators, continuously compensated by temperature. The gain transfer function for each gain stage, G (V), is mainly a linear function of a control voltage over the operating range, where G (V) is the gain in dB and V is the voltage of control. Alternatively, the variable gain stages could be implemented as digitally controlled attenuators or as variable gain amplifiers as is well known to one skilled in the art. The receiver 104 provides a reception signal intensity signal 148 (RSSI) and a closed loop correction signal 147 to the radiotelephone controller 105 in a conventional manner. In the conventional manner as described in the IS-95 standard, the radiotelephone controller 105 combines these two signals with a channel gain adjustment signal indicative of the variation in transmitter and receiver gain against the frequency channel, to produce a signal 150 of output power control Tx indicative of the P1354 / 97MX desired power output from the transmitter. During the manufacture of the radiotelephone 100, a table of channel gain adjustment signals against frequency channel is determined and stored in the radiotelephone controller 105. The radiotelephone controller 105 provides the output power control signal Tx 150 and a transition threshold signal 151 to the gain controller 130. The signal 151 of the transition threshold is an important feature of the present invention and will be described in detail further with reference to Figures 2, 3, 4 and 5. The gain controller provides the first gain control signal 131 and the second gain control signal 133 to the first variable gain stage 114 and to the second stage 120. of variable gain, respectively, in response to the output power signal 150 Tx and signal 151 of the transition threshold, to control the output power of the transmitter while minimizing the noise of the sideband of the transmit signal. transmission output. The operation of the gain controller 130 is described below in greater detail and with reference to Figure 2. The sideband noise of the transmission output signal can be expressed as the sum of the noise of the independent noise sources amplified by the Gain stages that follow noise sources. The P1354 / 97MX noise sources include the thermal noise of a gain stage, referred to its input and external interference coupled to the input of a stage. The thermal noise of a gain stage referred to its input is defined as kT * B * (Fl) in terms of the noise data (F), of the Boltzman constant (k, where k = 1.38 * 10-23 joule / K), the temperature in degrees Kelvin (T) and the measurement of the bandwidth (B) in Hz, as is well known to one skilled in the art. The thermal noise referred to the input is denoted below as Nesipio. For example, at T = 298K (25 ° C), the thermal noise referred to the input of a stage with a noise data of 10 measured in a bandwidth of 30 kHz is 1.07 femtoWatts (fW) or -119.7 dBm . Extreme interference at the input to the stage can be produced by a common mode coupling to the supplies and the saws of the stage and / or the pickup of the radiated interference from the noise sources. The interference generally consists of clock harmonics and harmonics of high-speed data signals generated by other circuits in the radiotelephone. In extreme cases, the interference can also be caused by high-power radio sources external to the radiotelephone, such as television transmitters, for example. The output or total noise emission of a gain stage that has gain (G) is P1354 / 97MX [Nth + I] * G + No * G, where I is the interference picked up at the input and Usual output is the output noise from the previous stage. In the transmitter 102, the total output noise (N) can be expressed by equation 1 (Eq. 1) shown below.

Ec. 1: N = (Nentradal + Njnod) * Gl * Gu * G2 * Gf + Nentradau * GuG2 * Gf + Nentrada2 * G2 * Gf + Nentradaf * Gf where Gk is the gain of stage k, Nentradak = Nésimok + Ik, Nésimok is the thermal noise of stage k, Ik is the input interference in stage k, Centered is defined as the quantity (Nth + 1) and Nmod is the output noise of the encoder / modulator 110. The definition of the subscripts, k, is as follows: 1 - first variable gain stage 114 u - ascending conversion stage 116 2 - second variable gain stage 120 f - stage end 122 Note that in equation 1, a reduction in the gain of the second stage of variable gain 120 will reduce the contributions to total noise output from all sources except the final stage. Therefore, in order to minimize the total noise output it is desirable to minimize the gain of the final stage 122 e P1354 / 97MX maximally increase the range of the second stage of variable gain 120. In the ideal approach, the entire dynamic range of output power would be achieved by controlling the second variable gain stage 120 only and the first variable gain stage would be eliminated . However, practical considerations avoid this for portable units, such as for example a CDMA radio telephone, which are small and light, have low cost and low power dissipation and have high frequency power control and high dynamic range. In the transmitter 102, the level of the output power (P) of the desired output signal Tx 123 can be expressed by the following equation 2: Eq. 2: P = P; nod * Gl * Gu * G2 * Gf where Gk is the gain of a stage k and Pmod is the power level of the modulated signal 113. The definition of the subscripts, k, is the same as that described above in equation 1. A challenge for the implementation of the ideal approach is to achieve the dynamic range of output power control from 85 dB to the RF frequency (eg, 824-849 MHz). The challenge becomes even greater at higher frequencies. At the minimum output power, the input signal to the second variable gain stage 120 is up to 85 dB greater than the output power. Some of P1354 / 97MX the same subjects discussed above with respect to interference apply to the coupling of the input signal of the second variable gain stage 120 to the output of the stage. The coupling can be produced by a common mode coupling in the supplies and the ground of the stage and / or the pickup at the output of a radiated input signal. Theoretically, this problem can be overcome using multiple stages to radio frequency, good landing and shielding practices; however, this is usually impractical for a small, lightweight, low-cost portable unit. In accordance with the preferred embodiment of the present invention, a more practical solution is to divide the dynamic range requirements of power control between a variable gain stage at the RF frequency Tx (824-849 MHz), such as for example the second variable gain stage 120 and a variable gain stage at the IF frequency Tx (150 MHz), such as for example the first variable gain stage 114. A power control scheme controls the second variable gain stage 120 over the most possible of the dynamic range of power control and controls the first variable gain stage 114 over the remaining range. Therefore, the range of gain control of the second stage of variable gain 120 is increased to the maximum, limited only P1354 / 97MX for practical considerations at 45 dB, for example. The gain control range of the first variable gain stage 114 is then designed to be at least 40 dB (ie 85 dB-45 dB). Equation 1 described above shows that the output noise is higher at the higher gain settings. Therefore, it is desirable to adjust the second variable gain stage 120 on the high power end of the dynamic range of output power and adjust the first variable gain stage 114 on the lower power end of the dynamic power range of departure. In accordance with the preferred embodiment, the practical operation of the power control scheme is further illustrated in Figures 3, 4 and 5. Figure 3 illustrates a graph that combines the graphs shown in Figures 3 and 4, showing the total gain against the total output power for a transmitter shown in the radiotelephone 1. The graph of Figure 3 shows the division of the gain control function of the transmitter between the first variable gain stage 114 and the second variable gain stage 120. Curve 300 is a graph of the transmitter gain in dB against the transmitter output power in dBm. Stroke line 301 denotes the level of gain transmission. The P1354 / 97MX dashed line 302 denotes the power transition level. At point A of curve 300, both the first variable gain stage 114 and the second variable gain stage 120 are at their predetermined maximum gain settings. At point B of curve 300, the first variable gain stage 114 is adjusted to its predetermined maximum gain setting and the second variable gain stage 120 is adjusted to its predetermined minimum gain setting. Point B of curve 300 denotes a transition in the gain control between the second variable gain stage 120 and the first variable gain stage 114. At point C of curve 300, both the first variable gain stage 114 and the second variable gain stage 120 are in their predetermined minimum gain settings. Region 1 on the graph below dashed line 301 and to the left of dashed line 302 corresponds to the lower end of the transmitter's output / gain power. In this region, the gain of the second variable gain stage 120 is kept constant at its minimum value and the gain of the first variable gain stage 114 is varied to vary the output power of the transmitter. In region 1, a 1 dB reduction in the desired output power results in a 1 dB reduction in the gain of the first variable gain stage 114 P1354 / 97MX and results in a 1 dB reduction in the contributions of the first term of equation 1, described above. The region 2 of the graph above dashed line 301 and to the right of dashed line 302 corresponds to the high end of the transmitter's output / gain power. In this region the variable gain second stage 120 is varied to vary the output power of the transmitter and the gain of the first variable gain stage 114 is kept constant at its maximum setting. In region 2, a 1 dB reduction in the desired output power results in a 1 dB reduction in the gain of the second stage of variable gain 120 and results in the reduction of all contributions of the output noise with the exception of of the last term (final stage) of equation 1, described above. Figure 4 illustrates a graph showing the gain versus the output power for the first variable gain stage 114. The curve 400 is a graph of the gain of the first variable gain stage 114 in dB against the output power of the transmitter in dBm. Dashed line 401 denotes the maximum gain level of the first variable gain stage. Dashed line 402 denotes the threshold level of power transition. At point A of curve 400, the first stage of gain P1354 / 97MX variable 114 is subject to its maximum predetermined gain setting. At point B of curve 400, the first variable gain stage 114 is subject to its maximum predetermined gain adjustment. Point B of curve 400 denotes a transition in the gain control between the second variable gain stage 120 and the first variable gain stage 114. At point C of curve 400, the first variable gain stage 114 is found at its minimum gain adjustment. Region 1 of the graph to the left of dashed line 402 corresponds to the low end of the transmitter's output / gain power. In this region, the gain of the second variable gain stage 120 is kept constant at its minimum value and the gain of the first variable gain stage 114 is varied to vary the output power of the transmitter. The region 2 of the graph to the right of the dashed line 402 corresponds to the high end of the transmitter's output / gain power. In this region, the gain of the first variable gain stage 114 remains constant or subject to its maximum adjustment. Figure 5 illustrates a graph showing the gain against the output power for the second variable gain stage 120. The curve 500 is a graph of the gain of the second variable gain stage 120 in P1354 / 97MX dB against the transmitter output power in dBm. The dashed line 501 denotes the minimum predetermined gain level of the second variable gain stage. Stroke line 502 denotes the power transition threshold level. At point A of curve 500, the second variable gain stage 120 is adjusted to its maximum gain setting. At point B of curve 500, the second variable gain stage 120 is subject to its minimum predetermined gain adjustment. Point B of curve 500 denotes a transition in the gain control between the second variable gain stage 120 and the first variable gain stage 114. At point C of curve 500, the second variable gain stage 120 is found at its minimum gain adjustment. Region 1 on the graph to the left of dashed line 502 corresponds to the lower end of the transmitter's output / gain power. In that region, the gain of the second gain stage 120 remains constant or subject to its minimum value. The region 2 of the graph to the right of the dashed line 502 corresponds to the high end of the transmitter's output / gain power. In this region, the second variable gain stage 120 is varied to vary the output power of the transmitter. Referring now to Figure 2 a block diagram of the gain controller 130 is illustrated as P1354 / 97MX is shown in Figure 1. The gain controller 130 is coupled to the first variable gain stage 114 and the second variable gain stage 120 by the gain control signal 131 and the second gain control signal 133 , respectively. The gain controller 130 is coupled to receive the level control signal 150 of the transmit output power and the gain transition threshold signal 151. The gain controller 130 generally includes a first fixator 200, a first control signal processor 214, a first digital-to-analog converter (DAC) 212, a second fixer 220, a second control signal processor 234 and a second converter from digital to analog (DAC) 232. The first control signal processor 214 generally includes a first multiplier or demultiplying circuit 202, a first adder or displacement circuit 204 and a first predistortion circuit 210. The first predistortion circuit 210 generally it includes a first control linearization circuit 206 and a third adder 208. The second control signal processor 234 generally includes a second multiplier or demultiplying circuit 222, a second adder or displacement circuit 224 and a second predistortion circuit 230. The second predistortion circuit 230, generally includes a P1354 / 97MX second gain control linearization circuit 226 and third adder 228. In gain controller 130, DAC 212 and DAC 232 are preferably implemented in the hardware. In addition, in the gain controller 130 the fixer 200, the fixer 220, the first control signal processor 214 and the second control signal processor 234 are preferably implemented in the software. However, any hardware and software allocation between the elements of the gain controller 130 can be used, as is well known to one skilled in the art. The desired output power level is supplied to the gain controller 130 by an output power control signal 150 from the controller 105 of the radiotelephone. A transition threshold signal 151 is also provided to the gain controller 130 from the controller 105 of the radiotelephone. The transition threshold signal 151 is indicative of the output power level or the gain level of the transmitter to which the transmitter output / gain power control is transitioned between the first variable gain stage 114 and the second gain stage. variable 120. The transition threshold signal 151 is a function of the frequency channel and is stored in the P1354 / 97MX controller 105 of the radiotelephone as a table during the manufacture of the radiotelephone 100. The output power control signal 150 and the transition threshold signal 151 are applied to the inputs of the circuits of the first fixator 200 and of the second fixer 220 • Generally, the first fixator 200 and the second fixator 220 comprise a transition circuit that provides continuous control of the output power level of the transmission signal between the lower range and the upper range of the predetermined range of transmission levels. output power by controlling the first gain control signal 131 and the second gain control signal 133, in response to the output power level control signal 150 and a transition threshold signal 151. More particularly, the first fixator 200 generates a first output signal 201 of the fixator in response to signal 150 controlling the output power and the threshold signal 151. The second fixer 220 generates a second fixer output signal 221, in response to the control signal 150 of the output power and the transition threshold signal 151. When the output power control signal 150. is greater than the transition threshold signal 151, the first output signal 203 of the fixator is equal to the transition threshold signal P1354 / 97MX 151 and the output signal 223 of the fixator is equal to the control signal 150 of the output power. When the control signal 150 of the output power is less than the transition threshold signal 151, the first output signal 203 of the fixer is equal to the control signal 150 of the power output and the second output signal 223 of the fixator is equal to the transition threshold signal 151. The first output signal 203 of the fixator is processed by the first processor 214 of the control signal to produce a first output signal 209 of the processor of the control signal. The first output signal 209 of the processor of the control signal is converted from a digital signal into an analog signal, by the DAC 212, to produce the gain control signal 131. In the preferred embodiment, the demultiplexer circuit 202 and the displacer 204 form a first linear transformer, coupled to receive the first output signal 201 of the fixator of the first fixator, to convert the first output signal 201 of the fixator into a first output signal 205 of the linear transformer, representative of the first gain control signal 131. The function of the first processor 214 of the control signal is to transform the gain transfer function of the first variable gain stage 114 into a preferred gain transfer function. The function of P1354 / 97MX gain transfer of the first variable gain stage 114 is defined as the gain of the first variable gain stage 114, as a function of the first control signal 131. The preferred gain transfer function for the first stage Variable gain 114 is defined as a function of the output power control signal 150. Preferably, the preferred gain transfer function is of the form G (P) = P + al, where G (P) is the gain of the first variable gain stage 114 in dB, P is the value in dBm of the 150 signal to control the output power and al is a constant. The constant 150 is also referred to as a mismatch. The slope of the desired transfer function is 1, such that a change of 1 dB in the control signal 150 of the output power results in a 1 dB change in the gain of the first variable gain stage 114 The slope of the preferred gain transfer function is also referred to as a sensitivity representing a change in gain in a change in the control signal of the output power. In the same way, the second output signal 223 of the fixer is processed by the second processor 234 of the control signal to produce a second output signal 229 of the control signal processor. The second P1354 / 97MX signal 229 of the processor output of the control signal is converted from a digital signal into an analog signal by the DAC 232, to produce the second gain control signal 133. In the preferred embodiment, the demultiplexer circuit 222 and the displacer 224 form a second linear transformer, coupled to receive the second output signal 221 of the fixator from the second fixator 220, to convert the second output signal 221 of the fixator to a second signal 225 of the linear transformer output, representative of the second gain control signal 133. The function of the second processor 234 of the control signal is to transform the gain transfer function of the second variable gain stage 120 into a preferred gain transfer function. The gain transfer function of the second variable gain stage 114 is defined as the gain of the second variable gain stage 114 as a function of the second control signal 131. The preferred gain transfer function for the second stage of Variable gain 114 is defined as the gain of the second variable gain stage 114, as a function of the output power control signal 150. Preferably, the preferred gain transfer function has the form G (P) = P + a2, where G (P) is the gain of the P1354 / 97MX second stage of variable gain 120 in dB, P is the value in dBm of the control signal 150 of the output power and a2 is a constant. The constant a2 is also referred to as a mismatch. The slope or sensitivity of the preferred gain transfer function is 1, such that a change of 1 dB in the output power control signal 150 results in a 1 dB change in the gain of the second gain stage variable 120. The circuits of the first processor 214 of the control signal and of the second processor 234 of the control signal are preferably used because the gain transfer functions of the first variable gain stage 114 and the second stage of Variable gain 120 are not perfectly represented by the preferred gain transfer function and / or are not perfectly represented by a linear equation over the entire operating range. In the preferred embodiment, the first variable gain stage 114 and the second variable gain stage 120 have gain transfer functions that are primarily linear over their respective gain control ranges and are monotonically increased with the control signal. In general, these gain transfer functions have the form G (V) = mV + b + d (V), where V is the voltage of the gain control signal, G (V) is the gain in dB, m P1354 / 97MX and b are constant and d (V) represents any deviation from the linear portion of the equation mV + b. The constant m represents a slope or sensitivity and b represents a mismatch. The circuits of the first processor 214 of the control signal and of the second processor 234 of the control signal are adjusted during manufacturing, so that the cascade of the control signal processor stage with the corresponding transfer function G (V ) of the variable gain stage produces the preferred gain transfer functions G (P). In other words, G (V (P)) = P + a for the first processor 214 of the control signal or G (V (P)) = + a2 for the second processor 234 of the control signal. The operation of the first processor 214 of the control signal is further described below. The operation of the second processor 234 of the control signal is identical to the operation of the first processor 214 of the control signal, with appropriate changes in the nomenclature and, it is omitted for reasons of brevity. In the first processor 214 of the control signal, the first output signal 203 of the fixator is multiplied by a first multiplier 202 having a gain kl, to produce a first output signal 203 of the multiplier. At the first output signal 203 of the multiplier is added the constant cl, in the first P1354 / 97MX adder 204 to produce a first output signal 205 of the adder. The first output signal 205 of the adder is provided to a first predistortion circuit 210 to produce the first output signal 209 of the control signal processor. The transfer function of the first processor 214 of the control signal is first described for the case where the first variable gain stage 114 has a linear gain transfer function G (V) = ml * V + bl, ie d (V) = 0. Again, the preferred gain transfer function G (V (P)) has the form G (V (P)) = P + al. The desired transfer function of the first processor 214 of the control signal then has the form V (P) = kl * P + cl, where kl = 1 / ml, and cl = (al-bl) / ml. kl and cl are determined during the manufacture of the radiotelephone. In this equation V (P) = kl * P + cl, kl represents a slope or sensitivity and cl represents a mismatch. The gain transfer function of the first variable gain stage 114 increases monotonically with the voltage of the control signal. Therefore, the first predistortion circuit 210 can be implemented as described below. The first output signal 205 of the summer (VI) is provided to the first gain control linearization circuit 206 and to the third summer 208. The first circuit 206 of P1354 / 97MX gain control linearization produces a value of a plurality of correction values e (Vl) in response to the first output signal 205 of the adder. The correction value is added to the first output signal 205 of the summer by the third summer 208 to produce the first output signal 209 of the control signal processor. The correction values e (Vl) are preferably predetermined based on the known characteristics of the gain transfer function of the first variable gain stage 114 and are stored in a table of the first gain control linearization circuit 206. The correction values e (vl) have the property that ml * e (Vl) = -d (Vl + e (Vl)). The table of correction values e (Vl) is linked to VI. In an alternate embodiment, the function of the first gain control linearization circuit 206, e (V1) is implemented as a linear correction equation by segments. Alternatively, the correction values or the linear correction equation by sections are determined and stored during the manufacture of the radiotelephone. The operation of the first processor 214 of the control signal is described below for the case where the first variable gain stage 114 has a non-linear gain transfer function (G (V) = ml * V + bl + d (V) First, consider the function of P1354 / 97MX cascade transfer of the first predistortion circuit 210 and the gain transfer function of the first variable gain stage 114 which is G (V1) = ml * (Vl + e (Vl)) + bl + d (Vl) + e (Vl)). Since e (Vl) is such that ml * e (Vl) = -d (Vl + e (Vl)), G (Vl) = ml * Vl + bl. The non-linear case has now degenerated to the linear case described above, G (V) = mi * + bl, where V is replaced by VI. Therefore, the desired transfer function of the input of the first multiplier 202 at the output of the first adder 204 is the same and the constants kl and cl are the same (kl = 1 / ml, and cl = (al - bl) / ml). In summary, a gain controller (130) for a transmitter (102) of (RF) controls the power level of a signal (123) transmitted within a predetermined range of output power levels. The gain controller (130) provides the first gain control signal (131) and the second gain control signal (133) in response to a control signal (150) of the output power level. The first gain control signal (131) controls the gain of a variable gain first stage (144) to vary the power level of the transmission signal (115) to an intermediate frequency which causes the power level of output of the transmission signal (123) varies P1354 / 97MX over a lower range of the predetermined range of power output levels. The second gain control signal (133) controls the gain of the second variable gain stage (120) to vary the power level of the transmission signal (121) to a radiofrequency which causes the level of the output power The transmission signal (123) varies over a higher range than the predetermined range of output power levels. The power control circuit (130) is advantageously used in a code division multiple access (CDMA) radiotelephone (100) to provide power control over a range of 85 dB of power levels at the same time as minimizes the sideband noise voltages, current consumption and complexity of the RF transmitter (102).

P1354 / 97MX

Claims (10)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property; 1. A transmitter for transmitting a transmission signal at a power level within a predetermined range of output power levels, the transmitter being characterized by: a signal generator for generating the transmission signal at an intermediate frequency; a first variable gain stage, coupled to the signal generator, for controlling the power level of the transmission signal at the intermediate frequency, in response to a first gain control signal; an upstream signal converter, coupled to the first variable gain stage, for converting the frequency of the transmission signal that is at an intermediate frequency into a transmission signal to a radio frequency; a second stage of variable gain, coupled to the upstream signal converter, to control the power level of the transmission signal to the radio frequency in response to a second control signal P1354 / 97MX gain; and a gain controller, coupled to the first variable gain stage and the second variable gain stage, to provide the first gain control signal and the second gain control signal, in response to a control signal of the gain level. the output power, wherein the first gain control signal controls the gain of the first variable gain stage to vary the power level of the transmission signal to the intermediate frequency, causing the power output level of the Transmission signal varies over the lower range of the predetermined range of output power levels and wherein the second gain control signal controls the gain of the second variable gain stage, to vary the power level of the transmission signal to radiofrequency, causing the output power level of the transmission signal to vary over a higher range than the predetermined range of eles of output power.
2. 2. A transmitter according to claim 1, wherein the signal generator is further characterized by: a local oscillator of intermediate transmission frequency to provide a signal of P1354 / 97MX local oscillator intermediate frequency transmission; and a modulator for modulating the signal of the local oscillator of intermediate transmission frequency with an information signal, to produce the transmission signal at the intermediate frequency.
3. A transmitter according to claim 1, wherein the upstream signal converter is further characterized by: a local transmitting radio frequency oscillator for providing a local radio frequency transmitter signal; and a mixer for converting upstream of the transmission signal at the intermediate frequency to the transmission signal to the radio frequency, in response to the signal of the local radio frequency transmitter oscillator.
4. A transmitter according to claim 1, wherein the gain controller is further characterized by: a transition circuit to provide continuous control of the level of the output power of the transmission signal between the lower range and the upper range of the predetermined range of output power levels, controlling the first gain control signal and the second control signal of P1354 / 97MX gain, in response to the control signal of the output power level and a transition threshold signal.
5. A transmitter according to claim 1, wherein the transition circuit is further characterized by: a first fixator, coupled to receive the signal controlling the level of the output power and the transition threshold signal, to produce a first signal output of the fixator representative of the first gain control signal, wherein the level of the first output signal of the fixator is fixed at a level of the transition threshold signal, when a level of the output power control signal is greater than the level of the transition threshold signal and in wherein the level of the first output signal of the fixer is equal to the level of the control signal of the level of the output power, when the level of the output power control signal is less than the level of the threshold signal of the output power. transition; and a second fixator, coupled to receive the control signal of the output power level and the transition threshold signal, to produce a second output signal of the fixator representative of the second gain control signal, wherein the level of the second output signal of the fixer is fixed at a level of P1354 / 97MX the transition threshold signal, when the level of the output power control signal is lower than the level of the transition threshold signal and, where the level of the second output signal of the fixator is equal to the level of the control signal of the output power level, when the level of the output power control signal is greater than the level of the transition threshold signal.
6. 6. A transmitter according to claim 5, wherein the gain controller is further characterized by: a first linear transformer, coupled to receive the first output signal of the first fixer, to convert the first output signal of the fixator into a first signal output of the linear transformer representative of the first gain control signal; and a second linear transformer, coupled to receive the second fixator output signal of the second fixer, to convert the second output signal of the fixator into a second linear transformer output signal representative of the second gain control signal.
7. 7. A transmitter according to claim 6, wherein the first linear transformer further comprises: P1354 / 97MX a first demultipler circuit, coupled to receive the first fixator output signal from the first fixer, to scale the first fixator output signal at a first predetermined factor, so that the gain sensitivity of the first stage of variable gain to the output power control signal is equal to one; a first displacement circuit, coupled to the first demultipler circuit, for moving the first output signal of the fixator at a second predetermined factor, to produce a first mismatch between the first output signal of the fixator and the output signal of the linear transformer; and wherein the second linear transformer further comprises: a second demultiplexing circuit, coupled to the second fixer, for scaling the second fixator output signal at a third predetermined factor, such that the gain sensitivity of the second variable gain stage at the control signal of the output power is equal to one; and a second displacement circuit, coupled to the second demultiplying circuit, for moving the second output signal of the fixator in a fourth predetermined factor to produce a second P1354 / 97MX mismatch between the second output signal of the fixator and the output signal of the linear transformer.
8. A transmitter according to claim 6, wherein the gain controller is further characterized by: a first predistortion circuit, coupled to the first linear transformer, for predistorting the first gain control signal in response to the first output signal of the transformer, to compensate for non-linearities in a first transfer function representative of the gain as a function of the first gain control signal for the first variable gain stage; and a second predistortion circuit, coupled to the second linear transformer, to predistort, the second gain control signal in response to the second output signal of the linear transformer, to compensate for the non-linearities in a second transfer function representative of the gain as a function of the second gain control signal for the second variable gain stage; a transition threshold signal.
9. 9. A method for controlling the output power level of a transmission signal within a predetermined range of output power levels, P1354 / 97MX method is characterized by the steps of: varying the power level of the transmission signal to an intermediate frequency to produce the output power level for the transmission signal, within a lower range of the predetermined range of output power levels; and varying the power level of the transmission signal to a radio frequency to produce the output power level for the transmission signal within a range above the predetermined range of output power levels. A method according to claim 9, further characterized by the steps of: determining the output power level for the transmission signal; and comparing the output power level with a threshold level of transmission of the output power; wherein the step of varying the power level of the transmission signal to an intermediate frequency is effected when the level of the output power is lower than the threshold level of transition of the output power, to produce the power level of the output. output for the transmission signal and where the step of varying the level of P1354 / 97MX power of the transmission signal to a radio frequency, is carried out when the level of the output power is greater than or equal to the threshold level of transition of the output power to produce the output power level for the transmission signal . P1354 / 97MX SUMMARY OF THE INVENTION A gain controller (130) for a radio frequency (RF) transmitter (102) controls the power level of a signal (123) transmitted within a predetermined range of output power levels. The gain controller (130) provides the first gain control signal (131) and the second gain control signal (133), in response to an output power level control signal (150). The first gain control signal (131) controls the gain of a variable gain first stage (144) to vary the power level of the transmission signal (115) to an intermediate frequency, which causes the power level of The output of the transmission signal (123) varies over a lower range of the predetermined range of output power levels. The second gain control signal (133) controls the gain of the second variable gain stage (120) to vary the power level of the transmission signal (121) to a radio frequency which causes the output power level of the transmission signal (123) varies over a higher range of the predetermined range of output power levels. The power control circuit (130) is advantageously used in a radiotelephone (100) with code division multiple access (CDMA) P1354 / 97MX to provide power control over a range of 85 dB of power levels while minimizing side band noise emissions, current consumption and the complexity of the RF transmitter (102). P1354 / 97MX