Cellular radio-telephone receiver employing improved technique for generating an indication of received signal strength
First Claim
1. A digital radio-telephone receiver employing an open-loop arrangement for generating a received-signal-strength-indicating ("RSSI") value suitable for use in mobile assisted hand-off ("MAHO") within a cellular telephone system, said receiver comprising:
- an amplifier for amplifying a received signal with a gain controlled by a gain-control signal so as to produce an amplifier output having amplitudes defining a signal envelope, an automatic-gain-control circuit responsive to the amplitude of the amplifier output and coupled in a feedback loop for applying an automatic-gain-control-circuit output signal to a control input of the amplifier as the gain-control signal, and means for generating an RSSI value by (i) opening the automatic-gain-control-circuit feedback loop, so that the automatic-gain-control-circuit output signal is not supplied to the amplifier, during a first period of time, (ii) during said first period of time, applying a ramp signal of increasing amplitude to the amplifier while the automatic-gain-control-circuit monitors the signal envelope, and (iii) when the signal envelope passes a pre-selected threshold, applying the then-occurring ramp-signal value to a look-up table to obtain the corresponding RSSI value stored therein.
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Accused Products
Abstract
In a digital radio-telephone receiver, an open-loop arrangement for generating a received-signal-strength-indicating ("RSSI") value suitable for use in mobile assisted hand-off within a cellular telephone system. The receiver has an amplifier for amplifying a received signal with a gain controlled by a gain-control signal, and an automatic-gain-control circuit ("AGC") responsive to the amplitude of the amplifier output and coupled in a feedback-loop for applying an AGC signal to the amplifier as the gain-control signal. An RSSI value is generated by (i) opening the AGC feedback loop so that the AGC output signal is not applied to the amplifier, (ii) applying a ramp signal of increasing amplitude to the VGA while the AGC monitors the signal envelope, and (iii) when the signal envelope passes a pre-selected threshold, applying the then-occurring ramp-signal value to a calibrated look-up table to obtain the corresponding RSSI value stored therein. Preferably, the receiver also employs a digital multiplexer ("MUX"), which provides to the amplifier as the gain-control signal, in response to a select signal, the ramp signal during a first period of time, and the AGC signal during a second period of time.
125 Citations
14 Claims
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1. A digital radio-telephone receiver employing an open-loop arrangement for generating a received-signal-strength-indicating ("RSSI") value suitable for use in mobile assisted hand-off ("MAHO") within a cellular telephone system, said receiver comprising:
- an amplifier for amplifying a received signal with a gain controlled by a gain-control signal so as to produce an amplifier output having amplitudes defining a signal envelope, an automatic-gain-control circuit responsive to the amplitude of the amplifier output and coupled in a feedback loop for applying an automatic-gain-control-circuit output signal to a control input of the amplifier as the gain-control signal, and means for generating an RSSI value by (i) opening the automatic-gain-control-circuit feedback loop, so that the automatic-gain-control-circuit output signal is not supplied to the amplifier, during a first period of time, (ii) during said first period of time, applying a ramp signal of increasing amplitude to the amplifier while the automatic-gain-control-circuit monitors the signal envelope, and (iii) when the signal envelope passes a pre-selected threshold, applying the then-occurring ramp-signal value to a look-up table to obtain the corresponding RSSI value stored therein.
- View Dependent Claims (2, 3, 4, 5, 6)
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7. In a digital mobile radio-telephone, a receiver comprising:
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A) means for tuning said receiver to a selected channel, B) an amplifier coupled to said tuning means for amplifying a signal received over the selected channel, said amplifier having a control input, the amplification gain of said amplifier being response to a control signal applied to said control input, C) a mixer coupled to said amplifier for generating baseband signals from the amplifier output, D) an analog-to-digital converter coupled to said mixer for generating digital baseband signals, said digital baseband signals being characterized by signal envelopes, E) a decoder coupled to said analog-to-digital converter for recovery of data from the digital baseband signals, F) a processor coupled to said tuning means, G) an automatic gain control circuit coupled to said analog-to-digital converter and said processor for monitoring the digital baseband signals, generating an automatic-gain-control-circuit signal from the digital baseband signals, said automatic-gain-control-circuit signal being responsive to the amplitudes of the envelopes of said digital baseband signals, and H) means for generating an RSSI value, including a memory storing a look-up table of RSSI values, and a ramp generator coupled to said amplifier, said processor and said memory for applying a ramp signal of increasing amplitude to said amplifier control input, and for applying the ramp value occurring when the signal envelope passes a pre-selected threshold to said look-up table memory to obtain the corresponding RSSI value stored therein.
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8. In a digital mobile radio-telephone, a receiver comprising:
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A) means for tuning the receiver to a selected channel, B) an amplifier coupled to said tuning means for amplifying a signal received over the selected channel, said amplifier having a control input, the amplification gain of said amplifier being response to a control signal applied to said control input, C) a mixer coupled to said amplifier for generating baseband signals from the amplifier output, D) an analog-to-digital converter coupled to said mixer for generating digital baseband signals, said digital baseband signals being characterized by signal envelopes, E) a decoder coupled to said analog-to-digital converter for recovery of data from the digital baseband signals, F) a processor coupled to said tuning means, G) an automatic gain control circuit coupled to said analog-to-digital converter and said processor for monitoring the digital baseband signals, generating an automatic-gain-control-circuit signal from the digital baseband signals, said automatic-gain-control-circuit signal being responsive to the amplitudes of the envelopes of said digital baseband signals, and H) means for generating an RSSI value, including i) a memory storing a look-up table of RSSI values, ii) a ramp generator coupled to said amplifier, said processor and said memory for generating a ramp signal of increasing amplitude, and iii) a multiplexer for passing one of said ramp signal and said automatic-gain-control-circuit signal to said amplifier control input in response to a select signal, and for applying the ramp value occurring when the signal envelope passes a preselected threshold to said look-up table memory to obtain the corresponding RSSI value stored therein. - View Dependent Claims (9)
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10. For generating a received-signal-strength-indicating value suitable for use in mobile-radio-telephone-assisted hand-off within a cellular telephone system, an arrangement comprising:
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A) a variable-gain amplifier for amplifying a received signal with a gain controlled by a gain-control signal so as to produce an amplifier output having amplitudes defining a signal envelope; B) An automatic-gain-control circuit coupled with the amplifier for monitoring the signal envelope of the amplifier output and generating an automatic-gain-control signal responsive to the amplitude of the amplifier output; C) selecting means coupled with the automatic-gain-control circuit and a ramp-generating means and responsive to a select signal for passing one of the automatic-gain-control signal and a ramp signal having increasing amplitudes to a control input of the amplifier;
wherein, when the automatic-gain-control signal is passed to the amplifier, the automatic-gain-control signal causes the amplifier output to remain within a pre-selected range; andD) a memory for storing a look-up table of received-signal-strength-indicating values corresponding to ramp-signal values, the selecting means applying the ramp-signal value occurring when the signal envelope passes a pre-selected threshold to the memory for obtaining the corresponding received-signal-strength-indicating value stored therein. - View Dependent Claims (11, 12)
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13. For generating a received-signal-strength-indicating value suitable for use in mobile-radio-telephone-assisted hand-off within a cellular telephone system, a method comprising the steps of:
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A) amplifying a received signal in an amplifier with a gain controlled by a gain-control signal so as to produce an amplifier output having amplitudes defining a signal envelope; B) monitoring the signal envelope of the amplifier output and generating an automatic-gain-control signal responsive to the amplitude of the amplifier output; C) generating a ramp signal having increasing amplitude; D) responsive to a select signal, passing one of the automatic-gain-control signal and the ramp signal to a control input of the amplifier; E) wherein, when the automatic-gain-control signal is passed to the amplifier, the automatic-gain-control signal causes the amplifier output to remain within a pre-selected range; F) storing a plurality of received-signal-strength-indicating values corresponding to ramp-signal values in a memory; and G) applying the ramp-signal value occurring when the signal envelope passes a pre-selected threshold to the memory for obtaining the corresponding received-signal-strength-indicating value stored therein. - View Dependent Claims (14)
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Specification