154results about "Control circuit for distortion reduction" patented technology

The present invention reduces automatic gain control (AGC) transients using first and second AGC processing branches to receive a signal. A gain is selectively adjusted (if desired) in the one of the AGC processing branches during a first time period. However, a gain is not adjusted in the other AGC processing branch during that first time period. The signals generated by the first and second AGC processing branches are then diversity processed to generate a received signal. The diversity processing effectively reduces the effect of any AGC transient.

A bias circuit 22 in a power amplifier 1 is provided with a VBE-controlled voltage source circuit 20 and a Nagata current mirror circuit 21. The Nagata current mirror circuit 21 includes a transistor Tr5 and a transistor Tr6. The transistor Tr5 has its emitter grounded, its base connected to a control input terminal 17 via a resistor R3, and its collector connected to that base via a resistor R4. The transistor Tr6 has its emitter grounded, its base connected to the collector of the transistor Tr5, and its collector connected to the base of the transistor Tr3. The arrangement is capable of compensating both the temperature characteristics of the gain of the power amplifier 1 and the control input voltage characteristics of the gain of the power amplifier 1. In other words, the arrangement is capable of reducing the temperature dependence and control input voltage dependence of the gain of the power amplifier 1.

A gain boost circuit and methodology are described for providing improved gain boosting with tuned amplifier circuits, such as differential low noise amplifier circuits having output resonant tank circuits. By selectively controlling the current source for a negative transconductance stage coupled between the differential amplifier output and the output resonant tank circuits, the amplifier gain may be adjusted to compensate for temperature variations. In addition, the amplifier gain boost may be selectively added, removed or even incrementally adjusted by using a current source control circuit in the negative transconductance stage to adjust the negative transconductance value generated by the negative transconductance stage.

The invention provides a gain compensation device over temperature and a method thereof. the gain compensation device for adjusting gain of an amplifier over temperature is disclosed. The gain of the amplifier is controlled by signals on a gain control end of the amplifier. The gain compensation device comprises a temperature compensation generator, an adder, and a temperature sensor. The temperature compensation generator is for generating an additional gain parameter according to a reference temperature, a current temperature, and a temperature coefficient. The adder comprises a first input end, coupled to the temperature compensation generator for receiving the additional gain parameter, a second input end for receiving a default gain parameter, and an output end coupled to the gain control end of the amplifier for outputting sum of the additional gain parameter and the default gain parameter. The temperature sensor is for providing the current temperature. The gain compensation device could make the actual gain keep constant owing to temperature change according to gain of temperature adjusting gain amplifier so as to provide great convenience.

A novel method of enhancing power amplifier linearity is disclosed. The invention is for use within a transceiver system and provides a method in the digital domain for predistorting a digital modulated signal to compensate for the non-linearity properties of the power amplifier and other components within the transmitter system. The RF output signal of the transmitter circuit is sampled and the corresponding amplitude and phase are detected using a receiver circuit. In dependence upon the amplitude and phase information, a look-up table is indexed to select the predistortion data and predistortion of the digital modulated signal occurs within the predistortion circuit.

A sound volume adjuster includes: a storage which stores a first value of a volume setting value and an allowable maximum change amount; a receiver which receives a change request indicating a second value of the volume setting value; a determiner which, when a change amount of the volume setting value between the first value and the second value exceeds the allowable maximum change amount, determines that the change request is an excessive request; and an adjuster which, when the determiner determines that the change request is the excessive request: changes the first value stored in the storage by a change amount which is equal to or smaller than the allowable maximum change amount to set a third value of the volume setting value; and adjusts a sound volume by the third value.

The invention discloses a compensation device for a power amplifier and a related method. The method for determining a pre-distortion value of the power amplifier comprises the following steps of: providing a first power input signal to make the power amplifier generate a first power output signal; receiving a first receiving signal which is acquired according to the first power output signal; detecting the predetermined gain of the power amplifier by using the first power input signal and the first receiving signal; providing a second power input signal to make the power amplifier generate a second power output signal; receiving a second receiving signal which is acquired according to the second power output signal; and determining a pre-distortion amplitude value and a pre-distortion phase value of the power amplifier by using the predetermined gain, the second power input signal and the second receiving signal.

There is provided a variable gain amplifier that is implemented with a CMOS device and has wide band variation and wide bandwidth by a predetermined exponential function. A variable gain amplifier having wide gain variation and wide bandwidth according to an aspect of the invention may include: a differential amplification section differentially amplifying an input signal according to a gain adjustment signal; and a gain adjustment section supplying the gain adjustment signal on the basis of an approximated exponential function determined according to a predetermined bias current, and adjusting a gain of the differential amplification section.

An apparatus and method for compensating the gain of an Automatic Gain Controller (AGC) for stabilizing the reception power of discontinuously transmitted packet data in a mobile communication system are disclosed. A compensation controller receives an AGC value from the AGC, sampling the AGC value by a predetermined sample number for a predetermined period, and obtains an AGC compensation gain by comparing a predetermined value with the difference between a sampled AGC value with a reference gain for the predetermined period. A compensator compensates the AGC value with the AGC compensation gain, thereby correcting errors generated in view of the nature of the AGC.

The direct conversion receiving apparatus has a gain control amplifier for variably amplifying a base band signal based on a gain switching control signal. A high pass filter has a first circuit including capacitors connected in parallel that are inserted in a path connecting an input terminal to an output terminal and switching effective total capacitance of the capacitors based on a first time constant switching control signal, and a second circuit including a resistor for providing a predetermined direct current voltage to the output terminal and switching the effective resistance value of the resistor based on a second time constant switching control signal. A control circuit outputs the gain switching control signal, and the first and second time constant switching control signals according to the change of the gain control of said gain control amplifier.

The invention discloses an adjustable gain audio power amplification circuit which comprises an input unit, an audio amplification unit, a gain adjusting unit, a control unit, a comparison unit and an output unit, wherein the audio amplification unit is connected with the input unit, the gain adjusting unit is connected with the audio amplification unit, the control unit is connected with the gain adjusting unit, the comparison unit is connected between the gain adjusting unit and the control unit, and the output unit is connected with the audio amplification unit; the comparison unit compares an output signal of the output unit with a common-mode reference voltage and outputs a gain adjusting control signal to the control unit, and the gain adjusting control signal is inversed when the output signal of the output unit is equal to the common-mode reference voltage; when detecting that the gain adjusting control signal is inversed, the control unit transmits a received gain adjusting signal to the gain adjusting unit; then, the gain adjusting unit controls the gain of the adjustable gain audio power amplification circuit according to the received gain adjusting signal. The adjustable gain audio power amplification circuit disclosed by the invention is simple in structure, and cracking noise generated by gain adjusting is avoided.

A variable gain amplifier includes a direct current (DC) blocking capacitor (1) which receives an input signal at a first terminal, a variable amplifier unit (4), having a variable transistor size, which amplifies an output of a second terminal of the DC blocking capacitor (1), a load impedance unit (2) coupled to an output of the variable amplifier unit (4), a bias resistor (2) having a first terminal coupled to the second terminal of the DC blocking capacitor (1), a variable bias voltage generator (5) which applies a variable bias voltage to a second terminal of the bias resistor (2), and a gain controller (9) which provides control to decrease the variable bias voltage when an effective transistor size of the variable amplifier unit (4) is controlled so as to increase, and provides control to increase the variable bias voltage when the effective transistor size of the variable amplifier unit (4) control is controlled so as to decrease.