Abstract: A high-efficiency amplifier (10, 18) that may be used in, for example, a radar system to amplify signals received at an exciter (22) before they are applied to an antenna (20). The amplifier includes, among other components, an adaptive matching network (48) that is controlled by a processing system (26) to allow the amplifier to be adaptively matched to the load as the operating frequency of the system undergoes changes. Specifically, the network is adjusted based upon information regarding the ratio R of reflected power over incident power measured at the load the last time the system operated at the same frequency. As a result, the system is able to respond more quickly to frequency changes.

Abstract: A circuit for combining first and second signals having the same frequency. The signals have a relative phase shift, 2a(t). The circuit generates a signal that is proportional to the sum or difference of signals. The circuit appears to be a resistive load; however, the circuit can be constructed from purely reactive circuit elements, and hence, does not dissipate energy. In one embodiment, the circuit is constructed from a transformer and two LC circuits in which the capacitance is varied in response to a(t). The circuit may be used to construct a high efficiency RF amplification stage.

Abstract: A two-stage, interstage transformer-coupled amplifier is provided with a degeneration resistor coupled between the collector of the first stage transistor and the power supply to limit the power dissipated in the first stage transistor. The first and second stages are coupled to ground through capacitor/inductor circuits to eliminate signal noise in the supply voltage. The output is filtered to remove harmonics and provide output impedance matching.

Abstract: A buffer amplifier circuit of a wideband tuner has an output transistor. The output terminal of this transistor is grounded through a matching transformer having two taps. One of the taps constitutes a terminal through which the output signal is delivered to a mixer circuit, while the other tap is grounded through a capacitor which constitutes, in cooperation with the matching transformer, a trap circuit. This trap circuit is adapted to trap a frequency which is about twice as high as the low region oscillation frequency of a local oscillator which produces an input to the buffer amplifier circuit.

Abstract: A synchro buffer amplifier is provided which uses two matched amplifiers respectively connected to the primary windings of two transformers. Two input leads are respectively connected to the inputs of the two amplifiers and a third input lead is grounded. The secondary windings of the two transformers are connected in series, and three output leads are respectively connected to the other sides of the two secondary windings and to the common secondary connection. Direct feedback is provided for each amplifier. Any circuit unbalance is compensated by the insertion of a low value choke in the common transformer secondary connection. Three capacitors are connected across the respective output leads partially to tune the loads, and thereby to nullify to some extent the effects of heavy inductive loads so as to allow operation of the buffer amplifier over a wider range of loads than would otherwise be possible.

Abstract: A remotely powered intermediate amplifier for communications transmission incorporates two sectional amplifiers and a filter circuit interconnecting the output of the first sectional amplifier with the input of the second sectional amplifier.

Abstract: A DC isolation amplifier having improved conductive isolation between its input and output. The amplifier includes an input section having a modulator and an output section having a demodulator and an oscillator section. The modulator and demodulator are nonconductively coupled through inductive loops of two closed-loop cores of magnetic material each having windings inductively coupled to the material of their associated core and to the other of the modulator or the demodulator. Additionally, a unitary closed loop winding couples the two cores such that the net EMF induced in the turns of the winding accordingly such that the respective component of the external magnetic field of the turns is substantially normal to the respective plane of each turn of this plurality. Additionally, this unitary loop is twisted between the cores to comprise a twisted pair additionally to minimize the effects from external magnetic fields. In the preferred embodiment, this loop is limited to two turns per core.