A pair of active rate limiting filters which limit the rate of change of the output thereof with respect to the input thereto include means to compare the output with the input and to increase the slew rate significantly when the output differs by more than the predetermined amount from the input. Additionally, the slew rate can be increased in response to an external control signal.

A canceller for eliminating the cross-polarization interference in incoming signals having polarizations which are orthogonal to one another is proposed. Each incoming signal is coupled to an associated adaptive filter. Each filter output is then summed with an associated one of the incoming signals which has a polarization orthogonal to that of the filter input signal. The signal sums formed are the canceller output signals. Adjustment of the adaptive filters so as to cancel the cross-polarization interference in each received signal is made in response to the incoming signals and the canceller output signals at selected times. During these times, circuitry for adjusting the adaptive filters examines spectral tones formed by the incoming signals and the canceller output signals.

An interference reduction circuit to provide isolation in frequency reuse systems operates on two or more non-isolated signals by cross-coupling the signals such that the interfering signals are cancelled on each channel. In a dual-polarized frequency reuse system, cancellation is effected by adding a sample of an oppositely polarized channel of equal amplitude, but of opposite phase, to the interference. Practical implementation includes closed-loop, digital feedback control to permit dynamic signal-to-interference improvement involving no a priori knowledge of the nature of the incoming signals. The circuit has applications in satellites and earth stations in a communications satellite system.

The bidirectional transmission for reading and writing data is performed between a write/read unit and a memory module using the contactless induction coupling of induction coils. The write/read unit frequency multiplexes a power source signal, a sync clock, and an enable clock and transmits the frequency multiplexed signals to the memory module. The memory module rectifies the received frequency multiplexed signals to produce an operating power source and to reproduce the sync clock and enable clock and to form an enable signal from the OR of both clocks. The write and read access information transmitted through another route is read in response to the reproduced sync clock and enable signal, thereby executing the writing and reading operations of a non-volatile memory.

Each of a transmitter and a receiver connected to an antenna through a duplexer includes a .pi./2 and a .pi. polarizer and an ortho-mode transducer (OMT) serially interconnected. In the receiver the OMT is connected at one output to a branching circuit and at the other output to a coupler which is connected to the branching circuit through a transfer circuit. In the transmitter, the OMT is connected at one input to a branching circuit and at the other input to a coupler subsequently connected to the branching circuit through a transfer circuit.