| 摘要 |
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.
|
