GB2330260A

GB2330260A - RF transmitter with temperature compensated output

Info

Publication number: GB2330260A
Application number: GB9821820A
Authority: GB
Inventors: Randall W Rich
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 1997-10-10
Filing date: 1998-10-08
Publication date: 1999-04-14
Anticipated expiration: 2018-10-08
Also published as: JPH11220410A; KR19990036990A; DE19846109A1; GB9821820D0; GB2330260B

Abstract

An arrangement for compensating temperature-induced variation in transmitter power amplifier 112 output in which temperature related power control data in a memory 142 is updated using data taken in a dynamic range for which the measured power output is considered reliable (because at low power levels the detector in particular is not reliable).

Description

2330260 RF Transmitter Having A Temperature Compensated Output Power Level

Control Circuit And Method Therefor

Field of the Invention

The present invention relates generally to radio frequency (RF) transmitters, and more particularly to a RF transmitter having a temperature compensated output power level control circuit and method therefor.

Background of the Invention

A radio frequency (RF) transmitter, such as the type embodied in a code division multiple access (CDNIA) cellular radiotelephone, provides an appropriate setting for describing the need for the present invention. A CDMA cellular radiotelephone is specified to transmit a signal over a 73 dB dynamic range extending from - 50 dBm to +23 dBm, according to the Electronic Industries Association TIA1ELAAS-95A 'Nobile Station-Base Station Compatibility $tandard for Dual-Mode Wideband Spread Spectrum Cellular Systern", published May 1995 (hereinafter referred to as 1S-95 Standard'). The output power level of the radiotelephone transmit signal is initially set based on an input level of a received signal and then corrected by commands received from a remote CDMA base station. Setting the output power based on the input level of the received signal is referred to as open loop power control. Correcting output power level of the transmitted signal by the remote CDNIA base station is referred to as closed loop power control.

-I- 1 The open loop power control relationship between the received signal level and the transmit signal level is described by the equation: Tx = Rx - 73 dB, where Tx is the output power level of the transmitted signal in dBm and Rx is the input level of the received signal in dBm. The allowable error in output power level of the transmitted signal for a given input level of the received signal is 9.5 dB over all operating conditions, including an ambient temperature range of -30'C to + WC. The effect of temperature on the receiver's gain and transmitter's gain is of particular concern when determining the output power level of the transmitted signal. The receiver's gain and the transmitter's gain need to be stable over the ambient temperature range and needs to be properly characterized so that temperature compensation can be applied so that the open loop gain variation will stay within the 9.5 dB window.

Typically, in radiotelephones designed for other cellular standards (AMTS, GSM, NADC), the trarismitter's gain variation over temperature is tracked out by a closed loop power control scheme within the radiotelephone. A radio frequency (RF) detector, typically implemented with a diode, detects the output power level of the transmitted signal and generates a voltage detect signal. The voltage detect signal is coupled to a negative input of an operational amplifier integrator. A positive input of the operational amplifier integrator is a predetermined voltage reference signal, converted by an digital to analog converter (DAC), which is set according to the desired output power level of the transmit signal. The voltage reference signal is typically determined during the manufacture of the radiotelephone. An output of the operational amplifier integrator is a control signal coupled to a voltage controlled amplifier (VCA) gain stage in the transmitter. The gain of the WA is adjusted responsive to the control signal to achieve the desired output. Using this scheme, the errors in the radiotelephone output power level due to temperature are mainly due to temperature variations in the RF detector which have been shown to be less than 0.5 dB.

Unfortunately, this closed loop power control scheme is not adequate for CDMA cellular radiotelephones. The response of the RF detector, implemented with a diode, has an exponential output voltage vs. input power (in dBm) characteristic and is only accurate over a top 25 dB of the specified 73 dB dynamic range needed in the CDMA system. Even if the RF detector is extremely well temperature compensated and the DAC has sufficient resolution to set the voltage reference signal at low power levels, external interference in the cellular transmit band could produce false RF detect readings when the radiotelephone output power level is low, and the external interference level is high. The false RF detect readings could cause the transmitter to reduce its gain. The remote CDMA base station could attempt to correct the radiotelephone output power level through closed loop power control. However, the radiotelephone's closed loop power control adjustment range is not infinite. The adjustment range is specified as 24 dB minimum around the open loop estimate in the IS-95 Standard. If the radiotelephone's output power cannot be increased adequately through closed power control, a call's audio quality could be degraded or the call could possibly be dropped.

Typically, controlling the output power in a closed loop mode with an RF detector reduces output power errors due to Tx gain variation to .5 dB at output power levels greater than 10 dBm. The output power error increases at levels below 10 dBm. Below an output power level of 0 dBm, controlling the output power in a closed loop mode with the RF detector is largely ineffective. The closed loop power control range can be extended somewhat by increasing the coupling ratio of an RF coupler andlor by adding more complex RF detector circuitry. However, there are drawbacks with each of these two approaches. Increasing the coupling ratio is equivalent to decreasing the efficiency of the transmitter and increasing current drain which is undesirable in a battery-powered radiotelephone. Increasing the complexity of RF detector circuitry increases product cost and parts count which is also undesirable. 71us, up to 60 dB of the 73 dB dynamic range required for CDMA operation may remain uncompensated using only the RF detector.

Another solution to this problem is to predetermine the transmitter's gain variations versus temperature and compensate the VCA's control signal based on a pre characterized value at a particular measured temperature. For this solution to be accurate and practicaL however, the variation in gain vs. temperature among different radiotelephones must be small and the variation in temperature sensors, providing the measured temperature, among different radiotelephones must be small. This could require extensive ongoing characterization during manufacturing and/or the adjustment of each radiotelephone over temperature before shipment to a customer. Both of these options are undesirable.

Accordingly, there is a need for a RF transmitter having a temperature compensated output power level control circuit and method therefor to permit the RF transmitter to operate over a wide dynamic range and over a wide temperature range.

Brief Description of the Drawings

FIG. 1 illustrates a block diagram of a radiotelephone including a transmitter having a temperature compensated output power level control circuit.

FIG. 2 is a flowchart illustrating a method, performed by the temperature compensated output power level control circuit of FIG. 1, for initializing access of the radiotelephone to a remote base station.

FIG. 3 is a flowchart illustrating a method, performed by the temperature compensated output power level control circuit of FIG. 1, for determining when and how to update temperature compensation values.

Detailed Description of a Preferred Embodiment

FIG. 1 illustrates a block diagram of a radiotelephone 100 micluding a transmitter 102 having a temperature compensated output power level control circuit 118. FIG. 2 is a flowchart 207 illustrating a method, performed by the temperature compensated output power level control circuit 118 of FIG. 1, for initializing access of the radiotelephone 100 to a remote base station 10 1. FIG. 3 is a flowchart 3 10 illustrating a method, performed by the temperature compensated output power level control circuit 118 of FIG. 1, for determining when and how to update temperature compensation values. FIGs. 1, 2 and 3 will be discussed interchangeably to integrate the structure of the RF transmitter 102, as represented by FIG. 1, with the method of operation of the RF transmitter, as represented by FIG. 2 and 3.

In the preferred embodiment of the present invention, radiotelephone 100 is a cellular radiotelephone. The radiotelephone 100 may take many forms that are well known in the art, such as a vehicular mounted unit, a portable unit, or a transportable unit.- According to the preferred embodiment of the present invention, the cellular radiotelephone is a CDMA cellular radiotelephone designed to be 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 and an antenna 106. The receiver 104 generally includes an Rx bandpass filter 120, a signal receiver 122, a decoder and demodulator 124 and an information sink 126. Generally, the receiver 104 and the antenna 106 are individually well known in the art, as taught in Motorola radiotelephone model number SUF 1712, U. S. Patent No. 5,3 21, 847 and the aforementioned IS-95 Standard, each herein incorporated by reference.

The transmitter 102 generally includes an information source 108, an encoder and modulator 110, an amplifying stage 112, a radio frequency (RF) coupler 114, a Tx bandpass filter 116 and a temperature compensated output power control circuit 118 (hereinafter referred to as "control circuit 118'). The amplifying stage 112 generally includes a variable gain amplifier 128 and a fixed gain amplifier 130. The fixed gain amplifier 130 represents the net gain of all stages including amplifiers, mixers, and/or filters typically found in the transmitter after the modulator 110 excluding the variable gain amplifier 128. The control circuit 118 generally includes a radio frequency (RF) detector 132, an analog to digital converter (ADC) 134, a voltage to power converter (VPC) 136, a temperature sensor 138, an analog to digital converter (ADC) 140, a memory device 142, a memory device 168, an error correction circuit 145, a controller 146, a voltage to power converter (VPC) 150, and a digital to analog converter (DAC) 154, a power to voltage converter (PVC) 164, and a summer 166. The error correction circuit 145 generally includes a comparator 160 and an error update circuit 144.

In the control circuit 118, the detector 132, the temperature sensor 138, the ADC 134, the ADC 140, and the DAC 154 are preferably implemented in hardware. Further, In the control circuit 118, the VPC 136, the controller 146, the memory device 142, memory device 168, the error correction circuit 145 (including the comparator 160 and the error update circuit 144), the VPC 150, the PVC 164 and the summer 166 are preferably implemented in software. However, any allocation of hardware and software among the elements of the control circuit 118 can be used as well known to one skilled in the art Portions of the known elements and functions of the transmitter 102 and the receiver 104 are generally embodied within an application specific integrated circuit (ASIC) as described in "CDMA Mobile Station Modem ASIC% Proceedings ofthe YEE 1992 Custom Integrated Circuits Conference, section 10.2, pages 1-5, and taught in a paper entitled "The CDMA Digital Cellular System an ASIC Overview% Proceedings of the IEEE 1992 Custom Integrated Circuits Conference, section 10. 1, pages 1-7 (herein incorporated by reference).

The mean transmit level of a CDMA cellular radiotelephone has been experimentally shown to be about 10 dBm in field trials. Therefore, it is reasonable to expect that subscriber units will operate above 10 dBm 50% of the time in a typical system. The coupling ratio of the RF coupler 114 is typically - 14 dB to - 17 dB. At transmitter output power levels above approximately 0 dBm to 10 dBm, the coupled signal 115 is within an acceptable range for closed loop operation with the RF detector 132. Note that the RF detector 132 is already available in a dual mode radiotelephone (i.e.

CDMA/ANTS), since it is used during an analog mode of operation.

In operation, the radio transmitter 102 receives information from the information source 108, typically as voice or data. The information provides an input signal 109 to be encoded and modulated by the encoder and modulator 110 to produce a modulated signal 111. The modulated signal 111 is amplified by the amplifying stage 112, having variable gain, for amplifying the modulated signal 111 with a gain corresponding to a control signal to produce an amplified signal 113 having an output power level within the specified 73 dB output power dynamic range. The amplified signal at line 113 is filtered by the Tx bandpass filter 116 for transmission by the antenna 106. The RF coupler 114 couples off a portion of the amplified signal at line 113 for use by the control circuit 118.

The temperature compensation output power level control circuit 118 and method therefor adapts to reduce the output power error due to transmitter gain variations over temperature. This is accomplished in the control circuit 118 by combining the RF detector 132 with the temperature senzor 138 and a software algorithm to provide adaptive temperature compensation of the output power level of the amplified signal 113 over a dynamic range greater than the useable range of the R.F detector 132 alone.

In operation, the control circuit 118 automatically temperature compensates the output power level of the amplified signal 113 responsive to a reference signal 147 to maintain a desirable output power level of the amplified signal 113 over temperature. The RF detector 132, coupled to the amplitiing stage 130, produces a detected signal 133 indicative of an output power level of the amplified signal 113. The RF detector 132 and its operation in an output control circuit of a RF transmitter is implemented using a diode as taught in U.S. Patents 4,523,155-Walczak et al. and 4,602,218-Vilmur et al., herein incorporated by reference. When the detected signal 133 is within a predetermined dynamic range of the RF detector 132 corresponding to a predetermined dynamic transmitter output power range, the detected signal 133 will contribute to the updating of the temperature correction signals in the memory device 142. When the detected signal 133 is not within the predetermined dynamic range of the RF detector 132, the detected signal 133 does not contribute to the updating of the temperature correction signals in the memory device 142.

The temperature sensor 138 produces a plurality of temperature signals resMnsive to corresponding temperatures measured near the amplifying stage 112. 71e temperature sensor 138 may be a Motorola (TM) 5109768D04, for example. The sensitivity of the temperature sensor 138 is typically 10mWC. The range of the temperature sensor 138 is typically -40C to +125C The temperature sensor 138 is located in a housing of the radiotelephone 100 and preferably mounted on a circuit board near the amplifying stage 112 of the transmitter 102. The step of measuring the temperature is represented as block 201 in FIG. 2.

The memory device 142, coupled to the temperature sensor 138, stores a plurality of temperature gain correction signals therein and provides one of the plurality of temperature gain correction signals 143 responsive to receiving a corresponding one of the plurality of temperature signals 139. Thus, the temperature gain correction signals 143 are indexed according to the measured temperature at the time the control circuit 118 determines the control signal 155. In the preferred embodiment, the magnitude of the plurality of temperature gain correction signals 143 is limited to discrete steps corresponding to discrete steps of the measured temperatures. The memory device 142 permits the magnitude of the one of the plurality of temperature gain correction signals 143 to change in the discrete steps for each power level adjustment cycle until the desired change is accomplishecL In the preferred embodiment the memory device 142 is implemented as random access memory (RAM). The contents of the memory device 142 are downloaded by the controller 146 from an electrically erasable programmable read only memory (EEPROM) device 168 to the memory device 142 via signal line 158 after the radiotelephone 100 has turned on but prior to active operation of the radiotelephone 100. The contents of the memory device 142 are written back into the memory device 168 via signal line 158 by the controller 146 prior to termination of the radiotelephone's operation. This operation permits the contents of the memory device 142 to be retained by the memory device 168 when the radiotelephone is inactive.

The temperature gain correction signals stored Mi the memory device 168 are initially pre-characterized based on the characteristics of the transmitter 102 and loaded into the memory device 168 prior to delivery to a customer. Preferably, each of the temperature gain correction signals stored therein corresponds to a range of measured temperatures. The resolution of the temperature gain correction signals over temperature is predetermined and based on desired performance requirements of the control circuit 118. The temperature gain correction signals are preferably represented in a table. Tle table represents the temperature gain correction signals versus temperature range. The table initially consists of predetermined default temperature gain correction signals versus temperature. The temperature gain correction signals in the table are updated to more accurate values during operation of the radiotelephone, as will be described in further detail hereinbelow. Tlius, the temperature gain correction signals in the table become customized or adapted to the characteristics of the transmitter 102 and receiver 104 of a particular radiotelephone 100 over time. Use of this customized set of temperature gain correction signals advantageously provides more accurate operation of the RF transmitter 102 than use of only the initial predetermined default temperature gain correction signals.

Ile error correction circuit 145 is coupled to the RF detector 132, the controller 146 and the memory device 142. Tle error correction circuit 145 updates one of the temperature gain correction signals, stored in a memory device 142 associated with the RF transmitter 102, corresponding to one of the temperatures 139 responsive to the detected signal 133 and the reference signal 147 during the mission of the amplified signal 113 and when the detected output power signal 133 is within the predetermined dynamic rangeThe reference signal 147 is preferably provided by the controller 146. In the preferred embodiment the reference signal 147 is the sum of a scaled received signal strength indication (RSSI) signal 123, a closed loop correction signal 125, and a channel gain adjustment signal (stored in the controller 146). The channel gain adjustment signal compensates the control loop for gain versus frequency variations in both the receiver 104 and the transmitter 102. The channel gain adjustment signals are predetermined and stored in the controller during the manufacture of the radiotelephone 100.

lle table of temperature correction signals in the memory device 142 is updated on an interrupt basis as directed by the controller 146 while the RF transmitter 102 is transmitting as represented by block 300 in FIG. 3. In the error correction circuit 145, the comparator 160, coupled to the power level detector 132 and the reference signal 147, subtracts the reference power signal 151 from the detected power signal 137 to produce an error signal 161. The step of calculating the error signal is represented in block 305 'm FIG. 3. The steps of reading the detected signal 133 and reading the reference signal 147 are represented in block 301 in FIG. 3. The error update circuit 144 updates one of the temperature gain correction signals, stored in a memory device 142 associated with RF transmitter 102, corresponding to one of the temperatures responsive to the output power error signal during the transmission of the amplified signal 113 and when the detected output power signal 133 is within the predetermined dynamic range of the detector 132. The step of measuring the temperature of the RF transmitter 102 is represented by block 301 of FIG. 3. The step of determining whether the detected output power signal 133 is within the predetermined dynamic range of the detector 132 is represented by block 303 in FIG. 3. The error update circuit 144 performs the updating via signal lines 157, 156 and 143. The step of updating is represented by blocks 306, 307 and 308 in FIG. 3. Any type of method or update algorithm may be used, as recognized by one of ordinary skill Mi the art. In the preferred embodiment, the new temperature correction signals are averaged with the old temperature correction signals represented by signal lines 143 and 156, respectively, while taking into account the present temperature correction signal 157. Further, all of the temperature correction signals stored in the memory device 142 are smoothed or averaged over when transferred to the memory device 168. 7be smoothing of the temperature correction signals across the temperature range of the table produces a more continuous temperature correction profile which yields more accurate and smaller step changes between temperature correction signals when applied to determine the control signal 155. After the table is updated, the method of the controller 146 returns from the interrupt, as represented by 309, to continue processing other radiotelephone functions.

The summer 166 is coupled to the PVC 164 and the reference signal 147. The summer 166 sums the updated temperature gain correction signal 157 with the reference signal 147 to produce the control signal 153 for the amplifying stage 112. The step of summing is represented as block 203 in FIG. 2. Therefore, the reference signal 147 is corrected by the control circuit 118 to correct the control signal 155.

In operation, the temperature gain correction signal 143 in the memory device 142 is updated responsive to the updated temperature gain correction signal 157. At the same time as the updated temperature gain correction signal 157 is produced, the software algorithm updates the one of the temperature gain correction signals stored in the table of the memory device 142. Thus, the new value replaces the old value in the table of the memory device 142. The updating is performed so that more accurate initial temperature compensation will be applied to output power levels of the amplified signal 113.

In the preferred embodiment, the radio transmitter 102 initializes the process of accessing the remote station in response to the send key being depressed or in response to a page being received from the remote base station 101, for example. This initial step is represented by block 200 of FIG. 2. The step of looking up the temperature correction value from the table in the memory device 142 is represented as block 202 in FIG. 2. It is important to properly determine the initial output power level estimate to minimize the load on the radiotelephone system which is power sensitive. Applying the control signal 155 to the amplifier 128 is represented by block 204 of FIG. 2. Keying up the transmitter 102 is represented by block 205 in FIG. 2. After the RF transmitter 102 is keyed up and in a call, the remote base station controls the output power level of the radio transmitter 102. This is known as closed loop output power level control as described hereinabove and is represented as block 206 in FIG. 2. During the closed loop output power level control, the temperature compensated output power level control circuit 118 preferably does not contribute to controlling the output power level of the radio transmitter 102 during the call. However, during the call, the control circuit 118 actively operates to update the values in the table of the memory device 142. Therefore, the table in the memory device 142 has the most up to date values at the time the call is completed. The process is repeated the next time the radio transmitter 102 keys up.

Thus, the control circuit 118 keeps the table in the memory device 142 updated during closed loop operation so that the radio transmitter 102 transmit s at a more accurate output power level the next time it keys up. Alternatively, during the closed loop output power level control, the temperature compensated output power level control circuit 118 may contribute to controlling the output power level of the radio transmitter 102 during the call.

The voltage signal to power signal converter 136 converts the detected signal 133 from a detected voltage signal 135 to a detected power signal 137. The step of converting the detected signal 133 from a detected voltage signal 135 to a detected power signal 137 is represented as block 302 in FIG. 3. The acceptable range of the detected signal 133 corresponding to an output power level above the mit threshold is determined during manufacture of the radiotelephone 100. The conversion may be implemented as an equation or a lookup table. The conversion is preferably implemented using an equation having the form P = m, Ln(V-C) + bl, where P is the output power Mi dBm, V is the detected signal 133 voltage, Ln represents a natural logarithmic operation, and m], C, and b] are constants determined during the manufacture of the radiotelephone 100. In the preferred embodiment bl is a function of the frequency of operation within the transmit frequency band (824 lUh to 849 MHz), and is predetermined during the manufacture of the radiotelephone. The controller 146 provides a value for bl based on a radiotelephone channel assignment prior to operation of the radiotelephone 100 on the assigned channel.

The voltage signal to power signal converter 150 converts the reference voltage signal 147 to a reference power signal 15 1. The step of converting the reference voltage signal 147 to a reference power signal 151 is represented in block 304 of FIG. 3. The conversion may be implemented as an equation or a lookup table. The conversion is preferably implemented using an equation having the form P = m2V + b2, where P is the output power in dBni V is the reference signal 147 represented as a voltage signal, and M2 and b2 are constants determined during the manufacture of the radiotelephone. In the preferred embodiment, b2 is a function of the frequency of operation within the transmit frequency band (824 NB-1z to 849 Nffiz), and is predetermined during the manufacture of the radiotelephone. The controller 146 provides b2 based on a radiotelephone channel assignment prior to operation of the radiotelephone 100 on the assigned channel.

The power signal to voltage signal converter 164 converts the updated temperature gain correction signal 157 from an updated temperature correction power signal 157 to an updated temperature correction voltage signal 165. This converting step is represented by block 208 of FIG. 2. In the power signal to voltage signal converter 164, the updated temperature gain correction signal 157 is scaled by a constant value to generate the control signal 155. The scaling is required to match the sensitivity (dB/V) of the reference signal 147. Preferably the scaling constant is 11m2.

Preferably the method for operating the control circuit 118 is performed in software. Therefore, appropriate signal type conversions are necessary. The analog to digital converter 134 is coupled to the power level detector 132 and converts the detected signal 133 from an analog detected signal 133 to a digital detected signal 135. The analog to digital converter 140 is coupled to the temperature sensor 138 and converts the plurality of temperature signals 139 from a plurality of analog temperature signals 139 to from a plurality of digital temperature signals 141. The digital to analog converter 154 is coupled to the combining circuit 144 and converts the control signal 153 from a digital control signal 153 to an analog control signal 155.

In summary of the preferred embodiment of the present invention, the RFtransmitter 102 temperature compensates an output power level of a signal transmitted by the RF transmitter 102. The reference signal source (here the controller 146) provides a voltage based, digital based reference signal 147. The voltage to power converter 150 converts the voltage based, digital based reference signal 147 to a power based, digital based reference signal 15 1. The amplifier 128 having variable gami amplifies an analog information signal 111 to produce an analog based amplified signal 113 for transmission by the RF transmitter 102 responsive to a voltage based, analog based control signal 155. 15 The RF coupler 114 samples an output power level of the analog based amplified signal 113 to produce an analog based sampled output power signal 115. The detector 132 detects the analog based sampled output power signal 115 to produce an analog based detected output power signal 133 having a predetermined range. The analog to digital converter 134 converts the analog based detected output power signal 133 to a digital 20 based detected output power signal 135. The voltage to power converter 136 converts the digital based detected output power signal 135 from a voltage based, digital based detected output power signal 135 to a power based, digital based detected output power signal 137. The temperature sensor 138 measures a plurality of temperatures 139 of the RF transmitter 102. Tle analog to digital converter 140 converts the plurality of temperatures 139 from an analog based plurality of temperatures 139 to a digital based plurality of temperatures 141. The comparator 160 compares the power based, digital based detected signal 13 7 and the power based, digital based reference signal 15 1 to produce a power based, digital based error output power signal 16 1. The error update circuit 145 updates one of a plurality of power based, digital based temperature gain correction signals, stored in a memory device 142 associated with RF transmitter 102, corresponding to one of the plurality of digital based temperatures 141 responsive to the power based, digital based output power error signal 161 during the transmission of the analog based amplified signal 113 and when the analog based detected output power signal 133 is within the predetermined range. The power to voltage converter 164 converts one of the plurality of power based, digital based temperature gain correction signals 157 to a voltage based, digital based temperature gain correction signal 165. The summer 166 sums the voltage based, digital based temperature gain correction signal 165 and the voltage based, digital based reference signal 147 to produce a voltage based, digital based control signal 153. The digital to analog converter 154 converts the voltage based, digital based control signal 153 to the voltage based, analog based control signal 155. The controller 146 controls the amplifier 128 responsive to the reference signal 147 as determined by the RF transmitter 102 and an initial temperature gain correction signal 157 and responsive to the RF transmitter 102 operating in an open loop output power control configuration with respect to a remote base station 101. The controller 146 keys up the RF transmitter 102 responsive to controlling the amplifier 128 to transmit the information signal 111 at a desirable output power level. The controller 146 controls the amplifier 128 responsive to the reference signal 147 as determined by the remote base station 10 1 responsive to keying up the RF transmitter 102 and responsive to the RF transmitter 102 operating in a closed loop output power control configuration with respect to the remote base station 101.

In summary, a temperature compensated output power level control circuit 118 comprises the RF detector 132 combined with the temperature sensor 138 and a software algorithm to provide adaptive temperature compensation of the output power level of the amplified signal 113 over a dynamic range greater than the useable range of the RF 5 detector alone.

Claims

What is claimed is:

Claims 1. A method for operating a radio frequency (RF) transmitter to temperature compensate an output power level of a signal transmitted by the RF transmitter, the method comprising the steps of.

amplifying an information signal to produce an amplified signal for transmission by the RF transmitter responsive to a reference signal and at least one of a plurality of temperature gain correction signals; detecting an output power level of the amplified signal to produce a detected output power signal having a predetermined range; measuring a plurality of temperatures of the RF transmitter; and updating one of a plurality of temperature gain correction signals, stored in a memory device associated with the RF transmitter, corresponding to one of the plurality of temperatures responsive to the detected output power signal and the reference signal during the mission of the amplified signal and when the detected output power signal is within the predetermined range.
2.

A method according to claim 1 further compn'sm"g the step of.

sampling the output power level of the amplified signal to produce a sampled 20 output power signal responsive to the step of amplifying, wheremi the step of detecting detects the output power level of the sampled output power signal to produce the detected output power signal having the predetermined range.
3. A method according to claim 1 further comprising the step of.. comparing the detected output power signal and a reference signal to produce a error output power signal prior to the step of updating, wherein the step of updating updates the plurality of temperature gain correction signals, stored in the memory device associated with the RF transmitter, corresponding to the plurality of temperatures responsive to the error output power signal during the mission of the amplified signal and when the detected output power signal is within the predetermined range.
4. A method according to claim 1 further comprising the step of.

summing the reference signal and the one a plurality of temperature gain correction signals to produce a control signal, wherein the step of amplifying amplifies the information signal to produce the amplified signal for transmission by the RF transmitter responsive to the control signal.
5. A method according to claim 1 further comprising the steps of. controlling the step of amplifying responsive to the reference signal as determined by the RF transmitter and an iruitial temperature gain correction signal and responsive to the RF transmitter operating in an open loop output power control configuration with respect to a remote base station; keying up the RF transmitter responsive to the step of generating the reference signal to transmit the information signal at a desirable output power level; and controlling the step of amplifying responsive to the reference signal as determined by the remote base station, responsive to the step of keying up the RF transmitter and responsive to the RF transmitter operating in a closed loop output power c3ntrol configuration with respect to the remote base station.
6. A method according to claim 5 wherein the step of controlling the step of amplifying responsive to the reference signal as determined by the remote base station further controls the step of amplifying responsive to updated voltage based temperature gain correction signals, responsive to the step of keying up the RF transmitter and responsive to the RF transmitter operating in a closed loop output power control configuration with respect to the remote base station
7. A radio frequency (RF) transmitter having a temperature compensated output power level control circuit, the RF transmitter comprising: an amplifier having variable gain for amplifying an information signal to produce an amplified signal for transmission by the RF transmitter responsive to a reference signal 15 and at least one of a plurality of temperature gain correction signals; a detector for detecting an output power level of the amplified signal to produce a detected output power signal having a predetermined range; a temperature sensor for measuring a plurality of temperatures of the RF transmitter; and 20 an error correction circuit for updating one of a plurality of temperature gain correction signals, stored in a memory device associated with the RF transmitter, corresponding to one of the plurality of temperatures responsive to the detected output power signal and the reference signal during the transmission of the amplified signal and when the detected output power signal is withmi the predetermined range.
8. A RF mitter according to claim 7 farther comprising: a RF coupler for sampling the output power level of the amplified signal to produce a sampled output power signal, wherein the detector detects the output power level of the sampled output power signal to produce the detected output power signal having the predetermined range.
9. A RF transmitter accordmig to claim 7 further comprising: a comparator for comparing the detected output power signal and a reference signal to produce a error output power signal prior to the error correction circuit updating 10 one of a plurality of temperature gain correction signals, wherein the error correction circuit updates the plurality of temperature gain correction signals, stored in the memory device associated with the R.F transmitter, corresponding to the plurality of temperatures responsive to the error output power signal during the mission of the amplified signal and when the detected output power 15 signal is within the predetermined range.
10. A R.F transmitter according to claim 7 furffier comprising: a summer for summing the reference signal and the one a plurality of temperature gain correction signals to produce a control signal, 20 wherein the amplifier amplifies the information signal to produce the amplified signal for transmission by the RF transmitter responsive to the control signal.
A RF transmitter according to claim 7 further comprising: a controller for performing the steps of. controlling the amplifier responsive to the reference signal as determined by the R-F transmitter and an initial temperature gain correction signal and responsive to the RF transmitter operating Mi an open loop output power control configuration with respect to a remote base station; keying up the RF transmitter responsive to the step of controlling the amplifier to transmit the information signal at a desirable output power level; and controlling the amplifier responsive to the reference signal as determined by the remote base station, responsive to the step of keying up the RF transmitter and responsive to the RF transmitter operating in a closed loop output power control configuration with respect to the remote base station.
12. A RF transmitter according to claim 11 wherein the step of controlling the step of amplifying responsive to the reference signal as determined by the remote base station further controls the step of amplifym"g responsive to updated voltage based temperature gain correction signals, responsive to the step of keying up the RF transmitter and responsive to the RF transmitter operating in a closed loop output power control configuration with respect to the remote base station.