Abstract:
A linear RF transmitter (100) includes a forward path (102, 105, 107) for receiving and processing a baseband input signal, the forward path including an upconverting mixer (120, 122) operable to convert a baseband signal into a modulated RF signal, and a RF (radio frequency) power amplifier (126) operable to amplify a modulated RF signal produced by the mixer, a non-linearity detector (125) connected to the forward path to sample a baseband signal for delivery to the mixer and operable to detect non-linearity of the transmitter and to provide in response a control signal to change operation of the transmitter to reduce the non-linearity, and characterised in that the transmitter further includes a regulator (111) connectible to a supply voltage source (113) and to the RF power amplifier to deliver a variable supply voltage (VS) to the RF power amplifier and a controller (127) operable to produce a control signal which controls adjustment by the regulator (111) of the supply voltage, wherein the non-linearity detector is connected to the controller and is operable upon detecting non-linearity to deliver a control signal to the controller which causes the controller to adjust the regulator to increase the supply voltage. Also described is a method of operation (200) in the transmitter.
Abstract:
A digital communication transmitter serves as a signal path (10) which uses an adaptive equalizer (18) in a predistortion role. The adaptive equalizer (18) pre-distorts a complex digital communication signal (12) that need not exhibit any distortion. Subsequent analog distortionintroducing segments (24, 30, 36, 42) then distort a predistorted signal (22) output from the adaptive equalizer (18). An error signal (46) is formed from a reference signal (52) and a return signal (54). The equalizer (18) implements an adaptation algorithm that adjusts filter (68) coefficients to minimize correlation between one of the reference and return signals (52, 54) and the error signal (46). The equalizer (18) generates four sets of coefficients for four different filters. Consequently, the equalizer (18) exhibits four degrees of freedom in introducing predistortion into a complex signal to counter the distortion subsequently introduced in the signal path (10) by the distortion-introducing segments (24, 30, 36, 42).
Abstract:
A circuit is provided that includes a Cartesian feedback loop (400). The Cartesian feedback loop (400) includes one or more operational amplifiers (250a-c). At least one of the operational amplifiers (250a) includes two or more cascaded amplifier stages (420a, 420b) and one or more bypass amplifier stages (422). The bypass amplifier stages (422) are connected in parallel with the cascaded amplifier stages (420a, 420b).
Abstract:
An IQ -modulator pre-distorter includes an iteratively updated digital filter ( gQ 0 , gQ 1 ) for filtering one of the branches of an IQ -signal to compensate for IQ - modulator generated amplitude errors. An iteratively updated digital filter ( cQI 0 , cQI 1 ), cross-connected from one of the branches to the other branch, filters one of the components of an IQ -signal to compensate for IQ -modulator generated inter-modulation between the branches. Iteratively updated compensators ( dcI, dcQ ) counteract IQ -modulator generated offset errors.
Abstract:
By the present invention is provided an inventive radio transmitter and a method to operate a radio transmitter, by which the quality of a transmitted radio signal can be improved. The radio transmitter comprises at least one digital filter having adjustable parameters. Via a control signal input the transmitter can receive a feedback signal being indicative of the output signal from the transmitter. The radio transmitter comprises programmable digital circuitry adapted to analyzing the feedback signal and to generating an analysis result. The programmable digital circuitry is further adapted to adjusting the adjustable parameters of the digital filter in accordance with the analysis result.
Abstract:
In the present invention, pre-distortion of drive signal (26) and generation of bias signal (36) to a power amplifier are both controlled dependent on an instantaneous size of the input signal, for producing a predetermined gain characteristics. Preferably, the bias signal (36) is kept low in amplitude ranges having a high probability to occur, thus giving a high efficiency, and is allowed to increase towards higher amplitudes, preferably all the way to the maximum amplitude. The pre-distorted drive signal (26) is preferably higher than the input signal in the high-efficiency ranges. Preferably, the drive signal (26) is predominantly composed of low-order components. In cases where signal paths of bias signal (36) and drive signal (26) differs significantly, inverse filtering is applied to ensure the simultaneousness at he input of the amplitude element.
Abstract:
An amplifier system (120, 820) for radio frequency signals comprises a phase and gain adjuster (122) which receives an input signal and a control vector (C) for producing a distortion-adjusted input signal. The distortion-adjusted input signal is applied to a main amplifier (126) which generates an amplified output signal. A control loop generates a control vector (P) indicative of distortion of the main amplifier. A modified pre-distortion vector generator (199, 899) generates a modified pre-distortion vector (P') which is combined with the control vector to produce a composite control vector (Comp). The composite control vector is applied to the phase and gain adjuster, thereby enabling the phase and gain adjuster to produce the distortion-adjusted input signal. In essence, the modified pre-distortion vector generator performs a vector multiplication (coordinate rotation) of a pre-distortion vector so that the resultant modified pre-distortion vector has a proper direction relative to the control vector.
Abstract:
A distortion compensator for compensating the nonlinearity of a power amplifier of a radio communication device. The operation such as automatic phase adjustment, automatic delay adjustment, equalizer adjustment, or update of a distortion compensation table is suspended if the input such as a reference signal, a feedback signal, an address of a distortion compensation table, or a phase value to the distortion compensating block is abnormal.
Abstract:
The control scheme uses the input and output signals of an amplifier (10) to control a lineariser (24) operating on the amplifier (10). The input and output signals are sensed and used to develop assay signals that have ideal inter-relationships when the amplifier is operating as desired. The control scheme modifies the operation of the lineariser to account for any departures observed in the relationships.