Abstract: A method and an arrangement for detecting impedance mismatch between an output of a radio frequency amplifier (200, 901, 911, 921, 1101) which has an amplifying component (201, 301, Q46, 701, 801) and an input of a load (203, 302) coupled to the output of the radio frequency amplifier having: first monitoring means (401) to monitor a measurable electric effect (311) at a side of the amplifying component (201, 301, Q46, 701, 801) other than the load (203, 302) and to produce a first measurement signal (411). Second monitoring means (402) monitor a measurable electric effect (312) between the amplifying component (201, 301, Q46, 701, 801) and the load (203, 302) and produce a second measurement signal (412). Decision-making means (204, 902, 912, 923, 1102) receive said first (411) and second (412) measurement signals and decide, whether said first and second measurement signals together indicate impedance mismatch.

Abstract: A programable gain amplifier (PGA) has an amplifier and a variable resistor that is connected to the output of the amplifier. The variable resistor includes a resistor that is connected to a reference voltage and multiple parallel taps that tap off the resistor. A two-stage switch network having fine stage switches and coarse stage switches connects the resistor taps to an output node of the PGA. The taps and corresponding fine stage switches are arranged into two or more groups, where each group has n-number of fine stage switches and corresponding taps. One terminal of each fine stage switch is connected to the corresponding resistor tap, and the other terminal is connected to an output terminal for the corresponding group. The coarse stage switches select from among the groups of fine stage switches, and connect to the output of the PGA.

Abstract: Briefly, in accordance with an embodiment of the invention, an apparatus and method to increase efficiency of a power amplifier is provided. The apparatus may include a power amplifier, and a variable impedance matching circuit coupled to the power amplifier to improve the transmitter efficiency over a range of output power. The variable impedance matching circuit may be adapted to match the output impedance of the power amplifier. The method may include varying the impedance of a circuit coupled to the output of a power amplifier during operation of the power amplifier to match the output impedance of the power amplifier.

Abstract: The present invention provides a switchable gain amplifier comprising a high-pass filter pole. The switchable gain amplifier comprises first and second input nodes for receiving first and second components of a differential input signal. A first input terminal of a first differential amplifier is coupled to the first input node, and a first input terminal of a second differential amplifier is coupled to the second input node. A first variable resistance is coupled between the first input terminal of the first differential amplifier and a second input terminal of the first differential amplifier. A second variable resistance is coupled between the first input terminal of the second differential amplifier and a second input terminal of the second differential amplifier. A differential capacitor is coupled between the second input terminal of the first differential amplifier and the second input terminal of the second differential amplifier.

Abstract: A programable gain amplifier (PGA) has an amplifier and a variable resistor that is connected to the output of the amplifier. The variable resistor includes a resistor that is connected to a reference voltage and multiple parallel taps that tap off the resistor. A two-stage switch network having fine stage switches and coarse stage switches connects the resistor taps to an output node of the PGA. The taps and corresponding fine stage switches are arranged into two or more groups, where each group has n-number of fine stage switches and corresponding taps. One terminal of each fine stage switch is connected to the corresponding resistor tap, and the other terminal is connected to an output terminal for the corresponding group. The coarse stage switches select from among the groups of fine stage switches, and connect to the output of the PGA.

Abstract: Signal coupling systems are provided which enhance signal isolation and dynamic range with structures that increase bias voltages in upstream signal amplifiers to guard against transistor saturation that would otherwise increase current drain, reduce response time and possibly cause lock-up of an associated gain-control system. Dynamic range is thus enhanced because these systems can operate over an extended range of source signals. The increased bias voltages also decrease parasitic junction capacitances which increases input impedances and thereby enhances signal isolation and reduces signal distortion.

Abstract: A network amplifier is provided. The network amplifier includes a variable equalizer having at least one control input and a variable attenuator having at least one control input. The network amplifier also includes at least one amplifier circuit that is coupled in series with the variable equalizer and the variable attenuator in a signal path of the network amplifier. The network amplifier also includes an automatic gain control circuit with a processor that monitors signals in the signal path and generates control signals for the control input of the variable equalizer and the control input of the variable attenuator to control at least one characteristic of the network amplifier.

Abstract: A feedback network for connecting an output of an operational amplifier with a feedback input of the operational amplifier, wherein the feedback network comprises a feedback circuit. The feedback network comprises a semiconductor switch in series to the feedback circuit for turning off and on the feedback network.

Abstract: An amplifier circuit having a high time constant. An operational amplifier includes a non-converting input terminal coupled to a ground, a converting input terminal and an output terminal. A first resistor network including at least one stage is coupled between the converting input terminal and the output terminal. Each stage of the first resistor network includes a first node, a first current path and a second current path connected to the first node. The first current path of each stage of the first resistor network is connected to the first node of the next stage, the second current path of each stage of the first resistor network is grounded, and the first current path of the first stage of the first resistor network is connected to the converting input terminal. A loading unit is coupled between the converting input terminal and the output terminal.

Abstract: An amplifier circuit having a controllable output power level comprises an attenuator configurable for receiving an input signal and operative to control an attenuation thereof, and an amplifier coupled to the attenuator, the amplifier receiving the attenuated input signal and generating an amplified output signal. The amplifier circuit further includes at least one power detector configurable to independently detect at least a portion of an incidental wave and a reflected wave corresponding to the amplified output signal and to generate first and second signals representative of the detected incidental and reflected waves, respectively. A controller is coupled between the power detector and the attenuator in a feedback configuration, the controller controlling the attenuation of the input signal and/or an amplification of the input signal as a function of the first and second signals from the power detector.

Abstract: A composite amplifier includes a main power amplifier (10) and an auxiliary power amplifier (12), which are connected to a load (14) over a Doherty output network (16). Filters (26, 28) are provided for pre-filtering the amplifier input signals in such a way that the signals meeting at the output of the main amplifier have essentially the same frequency dependence.

Abstract: A signal sensing module senses an RF signal and produces one or more secondary signals representative of the RF signal. An impedance matching control module generates a control signal, based on the one or more secondary signals, which is indicative of an impedance mismatch between a load and a communications device. The control signal is then applied to at least one variable impedance device to adjust the impedance of an impedance matching network and thereby reduce the impedance mismatch between the load and the communications device. In an embodiment, the at least one variable impedance device is a barium strontium titanate, thin film, parallel plate capacitor. In other embodiments, other variable impedance devices such as other types of thin film capacitors or varactor diodes are used to adjust the impedance of the impedance matching network.

Abstract: An apparatus for electromagnetic processing comprises a controller and a processor for receiving an input signal. The processor comprises one or more stages in communication with the controller. The controller is capable of regulating the input signal and the one or more stages to generate an output signal.

Abstract: A buffer amplifier is provided which includes an amplifying transistor, an inductance element for feeding power to the collector of the amplifying transistor from a power supply, a resistance attenuator having an input end, an output end, and a ground end, and an output terminal connected to the resistance attenuator. The input end of the resistance attenuator is directly connected to the collector of the amplifying transistor. The ground end is connected to the power supply. The output end is connected to the output terminal through a coupling capacitor.

Abstract: An amplifier circuit having a controllable output power level comprises an attenuator configurable for receiving an input signal and operative to control an attenuation thereof, and an amplifier coupled to the attenuator, the amplifier receiving the attenuated input signal and generating an amplified output signal. The amplifier circuit further includes at least one power detector configurable to independently detect at least a portion of an incidental wave and a reflected wave corresponding to the amplified output signal and to generate first and second signals representative of the detected incidental and reflected waves, respectively. A controller is coupled between the power detector and the attenuator in a feedback configuration, the controller controlling the attenuation of the input signal and/or an amplification of the input signal as a function of the first and second signals from the power detector.

Abstract: A Power Amplifier (PA) exhibits non-linear characteristics as a result of Amplitude Modulation-Phase Modulation (AM-PM) conversions resulting in intermodulation. Inter-modulation affects the RF signal spectrum at the output of the PA. The invention presents a method and apparatus for reducing intermodulation generated at the output of a PA as a result of AM-PM conversion. Presented is a RF power detector utilized in feedback control circuitry where the induction of odd-order harmonics into the feedback path acts to reduce AM-PM intermodulation at the output of the PA. The RF power detector comprises an detector input for receiving RF power and a detector output containing a pre-corrected detected voltage. The RF power detector comprises a pre-correcting circuit for generating odd-order harmonics at a specific power level. The pre-correcting circuit induces odd-order harmonics into the detected portion of output power allowing feedback control circuit to compensate for AM conversions.

Abstract: In a predistortion type linearizer including a FET, an input matching circuit connected to the drain of the FET for receiving an input signal, an output matching circuit connected to the source of said the FET for outputting an output signal, and a inductor having a first terminal connected to the gate of the FET and a second terminal for receiving a first control voltage, a variable impedance circuit is connected to the second terminal of the inductor, and the impedance of the variable impedance circuit is adjusted by a second control voltage.

Abstract: A guitar amplifier having an input terminal, an audio output and an audio level controller connected between the input terminal and the audio output. The audio level controller includes a first attenuation path, a second attenuation path having a fixed attenuation and a switch connecting only one of the first or second attenuation paths between the input and the audio output. The switch is preferably controlled remote from the amplifier and preferably by a foot-controlled switch. The first attenuation path is preferably variable. The audio level controller can include a first variable resistor coupled to the input terminal and having a wiper coupled to the audio output, the first variable resistor being coupled to a source of reference voltage through a second resistor to form the first attenuation path, the switch being coupled between the junction of the first and second resistors and the source of reference voltage to provide the second attenuation path.

Abstract: A high impedance attenuator for use in a test and measurement instrument employs compensation to adjust the low frequency attenuation to match the high frequency attenuation exhibited by the attenuator, rather than attempting to adjust the high frequency attenuation exhibited by the attenuator. In an alternate embodiment of the invention, compensation to adjust low frequency attenuation is employed in a feedback loop and an opposite compensation is applied in a parallel attenuation stage to stabilize the input resistance. In yet another embodiment of the invention, compensation to adjust low frequency attenuation is employed by means of an R-C time constant of an additional R-C circuit in a feed forward loop. This additional time constant is matched to the R-C time constant of the input R-C network. The input resistance of the attenuator is not changed.

Abstract: A distortion compensation output control circuit has an adder 1 for adding a value of input electric power and a value of a part of output electric power negatively fed backed together, a variable attenuator 2 for attenuating the electric power output from the adder 1, an electric power amplifier 3 for amplifying the electric power output from the variable attenuator 2 and outputting the output electric power set to a prescribed value, a variable attenuator 4 for attenuating the output electric power output from the electric power amplifier 3 and negatively feeding back the attenuated output electric power to the adder 1, a control circuit 12 for controlling the variable attenuator 4 so as to obtain the output electric power of the prescribed value, and a control circuit 11 for controlling the variable attenuator 2 so as to obtain a loop gain depending the output electric power of the prescribed value.

Abstract: An operational amplifier circuit with improved feedback factor is provided that includes an input impedance, an operational amplifier, and a current conveyor. The input impedance is operable to receive an input signal. The operational amplifier comprises an inverting input node, a non-inverting input node, and an output node. The operational amplifier is operable to generate an output signal at the output node based on the input signal. The current conveyor is coupled between the input impedance and the inverting input node of the operational amplifier. The current conveyor is operable to provide a low impedance to the input impedance and a high impedance to the operational amplifier.

Abstract: A power amplifier circuit (30, 60) improves the linearity of an amplified output signal. The power amplifier circuit (30, 60) includes an input (33, 63) for receiving a carrier signal (34, 64) and an array of combined amplifiers (32, 62) of a predetermined type for amplifying the carrier signal (34, 64). At least one amplifier (48, 78) of the predetermined type is located between the input (33, 63) and the array of combined amplifiers (32, 62) for amplifying the carrier signal (34, 64) to produce a predistorted carrier signal (34b1, 64b1) with a carrier signal component and a distortion component to condition the carrier signal (34, 64) for input into the array of combined amplifiers (32, 62), and specifically to compensate for nonlinearities produced by the array of combined amplifiers (32, 62).

Abstract: A composite amplifier includes a main power amplifier (10) and an auxiliary power amplifier (12), which are connected to a load (26) over a Doherty output network. An attenuator (34) is provided for activating the auxiliary power amplifier (12) before the main amplifier (10) is saturated. Preferably the input drive voltage to the auxiliary power amplifier (12) is increased along a smooth curve as the input signal amplitude to the composite amplifier increases.

Abstract: A signal sensing module senses an RF signal and produces one or more secondary signals representative of the RF signal. An impedance matching control module generates a control signal, based on the one or more secondary signals, which is indicative of an impedance mismatch between a load and a communications device. The control signal is then applied to at least one variable impedance device to adjust the impedance of an impedance matching network and thereby reduce the impedance mismatch between the load and the communications device. In an embodiment, the at least one variable impedance device is a barium strontium titanate, thin film, parallel plate capacitor. In other embodiments, other variable impedance devices such as other types of thin film capacitors or varactor diodes are be used to adjust the impedance of the impedance matching network.

Abstract: A system and method is provided for translating a wide common mode voltage range into a narrow common mode voltage range. The system and method extend the common mode voltage range of functional devices beyond the supply rails of the functional device, while keeping the differential signal loss to a minimum. The system and method translate a common mode input signal from a wide common mode voltage range into a narrow common mode voltage range utilizing a feedback technique.

Abstract: The present invention provides a slope equalizer for use in a voice frequency channel card, which is preferably electronically and remotely controllable, and retrocompatible with existing telecommunication systems. The slope equalizer of the invention includes a high-pass filter followed by a variable gain stage amplifier, where the variable gain stage amplifier is an operational amplifier with a plurality of parallel input signal paths, each of the signal paths being a series-connected resistor and switch. The switch is preferably a FET transistor that is electronically and, optionally, remotely controllable. The circuit topology allows the use of FET transistors having relatively high on-resistances. A further advantage of the topology is that the FET switches are connected to a virtual ground by way of an operational amplifier, thereby reducing on-resistance modulation caused by signal variations across the FET.

Abstract: In a transfer linearization (TL) circuit one or more biased nonlinear elements form a nonlinear attenuator and a biased network to allow adjustment of diodes to linearize the overall transfer of the TL circuit and an amplifier being linearized. The transfer linearization circuit reduces distortion encountered in a broadband RF amplifier. The circuit compensates for attenuation of amplified broadband signals in CATV systems. The transfer linearization circuit provides low insertion loss and requires very low power consumption. Nearly constant impedance and constant insertion loss is provided across a wide frequency range and reduces both in-band and out-of-band third order distortions. The TL circuit exhibits instantaneous amplitude and phase transfer correction. No tuned frequency selective components are required so that adjustments are relatively straightforward.

Abstract: A front-end signal-processing device having an automatic gain-control function used in the analog-to-digital conversion. The circuit comprises a buffer circuit, an amplifying/attenuating circuit, a pre-processing gain-adjusting circuit and an amplification/attenuation gain-adjusting circuit. In the front-end signal-processing device having an automatic gain-control function used in the analog-to-digital conversion, a set of gain-adjusting signals S1 and S2 are produced by hardware for controlling the amplification or attenuation gain of signals, thereby automatically adjusting the amplitude of the input signals. In addition, the microprocessor can select an appropriate restoring parameter according to the gain-adjusting signals to ensure that the numeral result conforms to the original input signal.

Abstract: A high impedance attenuator for use in a test and measurement instrument employs compensation to adjust the low frequency attenuation to match the high frequency attenuation exhibited by the attenuator, rather than attempting to adjust the high frequency attenuation exhibited by the attenuator. In an alternate embodiment of the invention, compensation to adjust low frequency attenuation is employed in a feedback loop and an opposite compensation is applied in a parallel attenuation stage to stabilize the input resistance. In yet another embodiment of the invention, compensation to adjust low frequency attenuation is employed by means of an R-C time constant of an additional R-C circuit in a feed forward loop. This additional time constant is matched to the R-C time constant of the input R-C network. The input resistance of the attenuator is not changed.

Abstract: A device for linearizing an RF or microwave signal output to an amplification stage including a traveling wave tube or a solid-state amplifier. A separator including a circulator and of a Schottky diode arrangement matched to the low-amplitude signals creates, for cheaper cost of components, of assemblage and of tuning, a compression path and an expansion path with excellent isolation performance and stability performance. Such a device may find particular application to telecommunications or to radar.

Abstract: Amplifier systems and methods are provided which closely approximate a constant output impedance and a constant quiescent output signal during forward and reverse modes of operation. The systems can be realized with small, inexpensive components that are compatible with integrated-circuit fabrication processes. A system embodiment includes a signal amplifier, a feedback path that is coupled across at least part of the signal amplifier to reduce its impedance, a reverse amplifier which is coupled to drive at least a feedback portion of the feedback path and a signal generator which controls operational timing of the signal amplifier and reverse amplifier. Another system embodiment includes an error-current canceler that cancels error currents of the signal amplifier with substantially equal and opposite correction currents.

Abstract: A programmable gain amplifier (PGA) has an amplifier and a variable resistor that is connected to the output of the amplifier. The variable resistor includes a resistor that is connected to a reference voltage and multiple parallel taps that tap off the resistor. A two-stage switch network having fine stage switches and coarse stage switches connects the resistor taps to an output node of the PGA. The taps and corresponding fine stage switches are arranged into two or more groups, where each group has n-number of fine stage switches and corresponding taps. One terminal of each fine stage switch is connected to the corresponding resistor tap, and the other terminal is connected to an output terminal for the corresponding group. The coarse stage switches select from among the groups of fine stage switches, and connect to the output of the PGA.

Abstract: When a change of an output signal is detected by an output-signal-state-change detector, a continuous-change performing part controls an output impedance changing part, which is provided between an output buffer and a signal line, so as to continuously change an output impedance from low impedance to high impedance, at the changing timing of the output signal.

Abstract: A programable gain amplifier (PGA) has an amplifier and a variable resistor that is connected to the output of the amplifier. The variable resistor includes a resistor that is connected to a reference voltage and multiple parallel taps that tap off the resistor. A two-stage switch network having fine stage switches and coarse stage switches connects the resistor taps to an output node of the PGA. The taps and corresponding fine stage switches are arranged into two or more groups, where each group has n-number of fine stage switches and corresponding taps. One terminal of each fine stage switch is connected to the corresponding resistor tap, and the other terminal is connected to an output terminal for the corresponding group. The coarse stage switches select from among the groups of fine stage switches, and connect to the output of the PGA.

Abstract: Circuitry to remove switches from signal paths in integrated circuit programmable gain attenuators. Programmable gain attenuators and programmable gain amplifiers commonly switch between signal levels using semi-conductors switches. Such switches may introduce non-linearities in the signal. By isolating the switches from the signal path linearity of the PGA can be improved.

Abstract: A transconductance circuit having a high output impedance has a dual input differential transconductor (10) with first (14) and second (16) differential inputs and a differential output (18). The first differential input (14) is connected to receive a dc voltage (20). An inverting feedback path is connected between the second differential input (16) and the differential output (18). A differential difference amplifier (24) has a first input (26) connected to receive the dc voltage (20) and a second input (28) connected to the inverting feedback path. A variable resistor (22) is connected across the differential output (18). The output (30) of the differential difference amplifier (24) is connected to control the variable resistor (22) to minimize the output of the differential difference amplifier (24), thereby creating a high output impedance from said transconductor (10).

Abstract: Disclosed in this application is the placement of an additional integrator between the first stage integrator output and the input to the attenuator/low pass filter. This approach reduces the input referred offset by a factor equal to the gain of the additional integrator, and the offset of the additional integrator itself will be divided by the gain of the first-stage integrator.

Abstract: A buffer amplifier is provided which includes an amplifying transistor, an inductance element for feeding power to the collector of the amplifying transistor from a power supply, a resistance attenuator having an input end, an output end, and a ground end, and an output terminal connected to the resistance attenuator. The input end of the resistance attenuator is directly connected to the collector of the amplifying transistor. The ground end is connected to the power supply. The output end is connected to the output terminal through a coupling capacitor.

Abstract: An electronic volume circuit is provided, which can be driven by a single power source and can therefore be formed by an LSI that can be fabricated in a simple manner using an oxide film and a junction process for a single power source. A first amplifying circuit attenuates the amplitude of a bipolar input signal and converts the attenuated input signal to a unipolar signal, and a variable resistor device controls the degree of attenuation of the first amplifying circuit based on an externally supplied signal.

Abstract: A high speed differential attenuator is formed on low temperature co-fired ceramic substrate structure having first and second parallel resistor-capacitor divider networks with each divider network having first and second parallel resistors and capacitors. The substrate has first and second dielectric layers with the top surface of the first dielectric layer having a voltage potential lead formed thereon for receiving an integrated circuit device. Each divider network further has first and second conductive elements formed on the top surface of the first dielectric layer functioning as first capacitive plates for the first and second capacitors. A third conductive element is disposed between the first and second dielectric layers and positioned beneath the first conductive element functioning as the other capacitive plate for the first capacitor.

Abstract: The performance of a power amplifier used in a signal transmitter, such as in a communication system (e.g., a personal communication system PCS), is optimized by coupling a controllable impedance to the output impedance of the power amplifier. The power output level of the amplifier, which is variable over a range from a minimum level to a maximum level and which is accompanied by a corresponding amplifier output impedance change, is detected, as is the operating power supplied to the amplifier. The controllable impedance that is coupled to the amplifier output is controlled as a function of the detected amplifier power output level and sensed operating power.

Abstract: A circuit for controlling frequency and/or phase response characteristic of a signal amplification system or channel has a serial architecture composed of a plurality of cells and a selector for deriving the signal after any one of the cascaded cells. At least one component of the RC network of each cell is in the form of a plurality of elements connected in series, each of the elements having a value which is a fraction of the design value of the component. A short-circuiting switch is associated with each element; the overall effect may be chosen by selecting the derivation node of the output signal and a certain configuration of the short-circuiting switches of the RC networks of the various cells. An outstanding flexibility of selection is achieved.

Abstract: A transcoding and transdecoding unit in a digital mobile radio system, and methods for adjusting their output signals. The unit includes an expander for converting companded digital data into a linear signal; a speech encoder for coding a linearized signal into encoded form; and an amplifier for amplifying the expanded signal. In order that the outbound audio signal not suffer interference due to the raised level, the transcoding unit further includes a level monitor for monitoring the amplitude of the linearized signal and for controlling amplifier such that the signal produced by the amplifier is of a desired level.

Abstract: An arrangement for controlling a high-frequency power amplifier, including a high-frequency power amplifier, a feedback line between the input side and the output side of the high-frequency power amplifier, a control connected to the input side of the high-frequency power amplifier and communicating with the feedback line, a sampler and a detector connected to the feedback line between the output side and the input side of the high-frequency power amplifier, as well as a switch connected to the forward line for bringing the high-frequency power amplifier to an OFF state controlled by a control signal. A parallel loop provided with a reference voltage feed is connected to the feedback line. The loop includes a signal adapter, the transfer function of which is dimensioned to substantially correspond to the transfer function of a power control loop constituted by the forward line and the feedback line, measured at switching points of the parallel loop.

Abstract: An arrangement for controlling the operation of a high-frequency power amplifier includes a high-frequency power amplifier connected to a forward line and a control, and an attenuator connected to the input side thereof. A sampler and a detector are connected to a feedback line between the output side and the input side of the high-frequency power amplifier. An amplifier is connected to the feedback line on the input side of the detector, the gain of the latter amplifier being of the same order of magnitude as the attenuation provided by the attenuator.

Abstract: A digitally controlled variable gain circuit which receives an analog input voltage and produces an analog output voltage. The digitally controlled variable gain circuit includes a first resistor string having first and second ends and a plurality of resistors connected in series between the first and second ends, the second end of the first resistor string being grounded and the analog input voltage being applied across the first and second ends of the first resistor string. A first selection mechanism, coupled to the first resistor string and responsive to a first digital control signal, provides a selectively determinable voltage divided output from the first resistor string.

Abstract: An output level automatic control apparatus suitable for use to keep a transmitted output level of a radio system constant has an objective to prevent an output level above a specified value from being transmitted if an input level abruptly becomes a normal level from a break state, and to stabilize the output level with a simple configuration. The output level automatic control apparatus includes a main amplifier output level feed-back control loop extending from an output side of a main amplifier to a variable attenuator, which main amplifier output level feed-back control loop includes an output level detecting means, a reference value setting means, and a control means controlling the variable attenuator on the basis of a result obtained by comparing a detected output of the main amplifier with a reference value.

Abstract: The apparatus first measures the peak power of a multichannel signal, or representation thereof. The peak power is compared with one or more peak power threshold values. If the measured peak power exceeds a threshold value, the multichannel signal is attenuated prior to being processed by the linear power amplifier.

Abstract: The disclosure relates to the linear power amplification, in a single channel, of a composite signal formed by two independent signals. In a single channel formed by correction means followed by a linear preamplifier followed by a saturated amplifier, the filtering and symmetry effect produced, both in the correction means and in the saturated amplifier, is advantageously used to compensate for clipping of the composite signal due to the amplifier. This makes it possible to obtain an undistorted output signal whose amplitude exceeds the level of saturation of the saturated amplifier. The compensation makes it necessary for the transfer characteristic of the correction means to have a given slope between two points beyond which the saturation appears in the saturated amplifier and a slope that is substantially thrice the given slope on each side of these two points.

Abstract: Broadband amplifiers which are intended to be linear suffer from distortion and although many techniques have been devised to overcome this problem significant improvements are required especially at frequencies above 100 MHz. An error signal is formed from the output of the amplifier 4 by comparison in a subtractor 11 with its input and the error signal is combined in a coupler 17 with the amplifier output to reduce distortion. The present invention provides automatic amplitude and phase control of the signals forming the error signal by means of components 24 and 25 in a multi-channel input and in the error signal by means of components 13 and 14. These components receive control signals from feedback networks 18' and 20' which each process two of three input signals from: couplers 34, 36 before the subtractor 11, a coupler 22 which passes the error signal and a coupler 21 after the coupler 17.