Abstract:
A modulator (100) for producing a modulated carrier signal in a radio transmitter and suitable for coupling to a power amplifier (40) whose output power is controllable by a DC supply voltage. The modulator (100) comprises quadrature generation means (110) for generating baseband in-phase (I) and quadrature-phase (Q) signal components for a non-constant envelope modulation scheme from a base band data signal, means (30, 32) for scaling the I and Q signal components by a scaling factor for effecting transmitter power control, quadrature modulation means (34 for modulating a carrier signal with the I and Q signal components, and power supply control means (120) for generating, from a baseband signal prior to modulation of the carrier, a power supply control signal which tracks the envelope of the modulated carrier signal for controlling a DC supply voltage of the power amplifier (40). The modulator (100) may comprise additional modes of operation encompassing peak envelope tracking, constant envelope modulation, and envelope elimination and restoration.
Abstract:
An automatic gain control (AGC) controls the signal amplitude at the input to an analog to digital converter (ADC) input by applying a gain that produces a desired overall amplitude resolution of the patterns actually presented by the signal delivered by the ADC converter. Short RLL patterns will have sufficient resolution for reliable extraction as a result of having sufficient overall amplitude, which thereby strengthens the ability of the read channel to correctly extract data. Moreover, the system determines correct AGC settings responsive to measurements of user data parameters. The system 0 also detects and corrects for DC offsets in the signal whose gain is controlled.
Abstract:
A transmitter includes a dual mode modulator and an amplifier coupled to the dual mode modulator. The dual mode modulator implements a linear modulation scheme during a first mode of the modulator to produce a variable envelope modulated signal. The dual mode modulator implements a non-linear modulation scheme during a second mode of the modulator to produce a constant envelope modulated signal. The amplifier is biased as a linear amplifier during the first mode of the modulator and is biased as a non-linear amplifier during the second mode of the modulator. A feed-forward connection between the dual mode modulator and the amplifier is used to indicate a change in modulation mode and to adjust the bias of the amplifier. A power of the constant envelope modulated signal is increased such that an operating point of the amplifier remains substantially constant during the first and second modes of the modulator.
Abstract:
A received frame is branched into a gain control system (20A) for common pilot signals and a gain control system (20B) for individual data signals. The gain control system (20A) controls the gain of the common pilot signals, and the gain control system (20B) controls the gain of the data signals. A signal processor (30) establishes synchronization of frames, outputs a gain control signal (g1) so that the gain of the common pilot signal is constant, to a gain control circuit (21a) for the common pilot signals, and outputs a gain control signal (g2) so that the gain of the data signal is constant, to a gain control circuit (21b) for the data signals. The gain is controlled to be constant, thereby preventing saturation of ADC (26a, 26b, 27a, 27b) and S/N deterioration.