Radio telephone using received signal strength in controlling transmission power
DCFirst Claim
1. A radio telephone for receiving a first broadcasted, radio-frequency communication signal over a selected channel from which an acoustic signal is extracted and provided to a speaker, and for transmitting an amplified, second, radio-frequency communication signal over said selected channel, aid radio telephone comprising:
- A) means for generating a strength-indicating signal representative of the strength of said received first communication signal;
B) means responsive to said strength-indicating signal for generating a control signal, said control-signal-generating means including(i) means for calibrating said strength-indicating signal using a calibration factor corresponding to said selected channel, and(ii) means for deriving said control signal using said calibrated strength-indicating signal; and
C) means coupled to said control-signal-generating means for amplifying a second communication signal in response to said control signal to produce an amplified second communication signal.
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Abstract
A radio telephone uses a signal indicating the strength of received communication signals as a measure of prevailing signal propagation conditions to control the gain of a power amplifier in its transmitter. Where conditions are favorable, the gain can be reduced without deleterious effects on transmitted signals, and with a resulting savings in power drain on the radio telephone'"'"'s power supply (e.g., batteries). In this way, talktime on a single battery charge can be significantly lengthened. Where conditions are adverse, e.g., at outlying or fringe areas of a cellular telephone system of which the radio telephone is a station, the gain can be increased to produce stronger transmitted signals, at times extending the effective coverage area of such systems. Preferably, the output of the power amplifier remains at all times within a power range prescribed by applicable standards, and is increased or decreased within the power range in accordance with prevailing conditions indicated by the received signal strength signal.
159 Citations
22 Claims
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1. A radio telephone for receiving a first broadcasted, radio-frequency communication signal over a selected channel from which an acoustic signal is extracted and provided to a speaker, and for transmitting an amplified, second, radio-frequency communication signal over said selected channel, aid radio telephone comprising:
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A) means for generating a strength-indicating signal representative of the strength of said received first communication signal; B) means responsive to said strength-indicating signal for generating a control signal, said control-signal-generating means including (i) means for calibrating said strength-indicating signal using a calibration factor corresponding to said selected channel, and (ii) means for deriving said control signal using said calibrated strength-indicating signal; and C) means coupled to said control-signal-generating means for amplifying a second communication signal in response to said control signal to produce an amplified second communication signal. - View Dependent Claims (2, 3, 4)
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5. A communication apparatus for receiving a radio-frequency receive signal over a selected channel, and for transmitting an amplified radio-frequency transmit signal over said selected channel at a selected power level within a defined range of power levels, said communication apparatus comprising:
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A) a transmitter including means for converting audio and control signals into said transmit signal, means for amplifying said transmit signal, said amplifying means having a gain responsive to a gain control signal, and a gain control circuit for deriving said gain control signal from a power control value; and B) a receiver including means for converting said receive signal into audio and control signals, and means for deriving a signal indicative of the strength of said receive signal, whereby said receive-signal-strength signal is indicative of prevailing signal propagation conditions; and C) a processor coupled to said transmitter and said receiver, said processor (i) computing a time-averaged value of said receive-signal-strength signal over a selected period of time, (ii) calibrating said time-averaged value using a calibration factor corresponding to said received-signal-strength signal and to said selected channel, (iii) deriving a target power level for said transmit signal using said calibrated time-averaged value, said target power level being within said range of power levels; and (iv) deriving said power control value using said target power level, and wherein said gain control signal controls the gain of aid power amplifier to drive said power level of said transmit signal toward said target power level in response to an indication of prevailing signal propagation characteristics. - View Dependent Claims (6)
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7. Apparatus for controlling the power level of signals transmitted by a radio telephone, said telephone having a transmitter including a power amplifier whose gain is controlled by an automatic-gain-control circuit, said apparatus comprising:
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A) means responsive to a received communication signal for deriving an analog signal to indicate the strength of the received communication signal, and thereby to indicate prevailing signal propagation conditions encountered by the received signal, B) means for converting the strength-indicating signal into a digital signal, C) means for sampling the digital strength-indicating signal and deriving an average value therefrom over a selected period of time, whereby transient components of the signal are reduced, D) means for calibrating the average value of the digital strength-indicating signal, E) means responsive to the calibrated strength-indicating value for deriving a target transmission power for the signal propagation conditions indicated thereby, F) means responsive to the target transmission power for deriving a power control signal, which, when applied to the automatic-gain-control circuit, will produce an output power from the amplifier equal to the target transmission power, and G) means for applying the power control signal to the automatic-gain-control circuit, and H) wherein said automatic-gain-control circuit includes means for deriving an automatic gain control signal corresponding to the difference between the power control signal and the power amplifier output, and for applying the automatic gain control signal to a control input of the power amplifier so as to control its gain, and thereby drive the power level of its output toward the target transmission power. - View Dependent Claims (8, 9, 10, 11, 12)
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13. Apparatus for controlling the power level of signals transmitted by a radio telephone, said telephone having a transmitter including a power amplifier whose gain is controlled by an automatic-gain-control circuit, said apparatus comprising:
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A) means responsive to a received communication signal for deriving an analog signal to indicate the strength of the received communication signal and thereby an indication of prevailing signal propagation conditions encountered by the received signal, B) means for converting the strength-indicating signal into a digital signal, C) means for deriving an average value for the digital signal over a selected period of time, D) means for calibrating the average value of the digital strength-indicating signal, whereby transient components of the signal are reduced, said calibrating means including calibration look-up table means responsive to the average strength-indicating value for providing a calibrated strength-indicating value, E) target-transmission-power look-up table means responsive to the calibrated strength-indicating value for providing a target transmission power, F) power-control-signal look-up table means responsive to the target transmission power for providing a power control signal, which, when applied to the automatic-gain-control circuit, will produce an output power from the amplifier equal to the target transmission power, and G) means for applying the power control signal to the automatic-gain-control circuit, and H) wherein said automatic-gain-control circuit includes means for deriving an automatic-gain-control signal corresponding to the difference between the power control signal and the power amplifier output, and for applying the automatic-gain-control signal to a control input of the power amplifier so as to control its gain, and, thereby drive the power level of its output towards the target transmission power. - View Dependent Claims (14, 15)
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16. A method of controlling the power of an RF signal amplified by a variable-gain power amplifier of a radio telephone prior to transmission thereof, said method comprising:
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A) determining prevailing signal propagation conditions by, i) generating a strength-indicating signal representative of the strength of a communication signal received over a selected channel, and ii) calibrating said strength-indicating signal using a calibration factor corresponding to said selected channel, B) computing a target power level for said RF signal using the calibrated strength-indicating signal, and C) controlling the gain of said power amplifier by generating a control signal that will drive the output power of said power amplifier toward said target power level, and applying said control signal to said amplifier.
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17. Method of controlling the power level of signals transmitted by a radio telephone, said telephone having a transmitter including a power amplifier whose gain is controlled by an automatic-gain-control circuit, said method comprising the steps of:
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A) from a received communication signal, deriving an analog signal to indicate the strength of the received communication signal and thereby an indication of prevailing signal propagation conditions encountered by the received signal, B) converting the strength-indicating signal into a digital signal, C) sampling the digital strength-indicating signal and deriving an average value for the signal over a selected period of time, D) calibrating the average value of the digital strength-indicating signal, whereby transient components of the signal are reduced, E) from the calibrated strength-indicating value, deriving a target transmission power for the signal propagation conditions indicated thereby, F) from the target transmission power, deriving a suitable power control signal, which, when applied to the automatic-gain-control circuit, will produce an output power from the amplifier equal to the target transmission power, G) applying the power control signal to the automatic gain-control circuit, H) in the automatic-gain-control circuit, deriving an automatic-gain-control signal proportional to the difference between the power control signal and the power amplifier output, and applying the automatic gain control signal to a control input of the power amplifier so as to control its gain, and drive the power level of its output toward the target transmission power. - View Dependent Claims (18, 19, 20, 21, 22)
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Specification