Raytheon Company

Marc R Sheade

Raymond S Pengelly

Paul A Murphy

A frequency converter employs a balanced bridge mixer of switching elements such as field-effect transistors (FETs) with a local oscillator supplying control signals to gate terminals of the transistors. A carrier at intermediate frequency (IF) or at radio frequency (RF) is modulated for communication of data, and is applied to alternate nodes of the bridge. The remaining bridge nodes supply output signals to respective branches of an output circuit. Each branch of the output circuit is provided with a bandpass filter having a spectral characteristic corresponding to the spectral characteristic of a specific one of plural output signals to be outputted via the branch. Each branch may contain an active element, such as an amplifier, which is activated for outputting a signal, and which is deactivated for when node signal is to be outputted. A switchable impedance circuit is included within each of the branches to present a substantially constant impedance characteristic to the bridge, independently of whether the bridge amplifier is activated or deactivated. The local oscillator may provide plural frequencies, as by use of a variable-frequency oscillator or by use of plural oscillators, to place an output signal within the frequency band of a specific one of the output branches.

Plural band converter

A Detector Log Video Amplifier (DLVA) comprising a first RF detector for detecting the power levels of received RF signals having power levels within a first range (e.g., -40 dBm to -20 dBm) and producing corresponding first video frequency signals having amplitudes representative thereof, from which are produced output signals having amplitudes logarithmically proportional to such received signals. A second RF detector detects the power levels of received RF signals having power levels within a second range (e.g., -20 dBm to +20 dBm) and produces corresponding second video frequency signals having amplitudes representative thereof, from which are produced output signals having amplitudes logarithmically proportional to such received signals. A control signal is produced from the second video frequency signals, the control signal having a level in accordance with the power levels of received RF signals. Received RF signals having power levels equal to or exceeding a first level (e.g., 0 dBm) are attenuated in accordance with the control signal level and coupled to the first detector. A limiter is responsive to the power levels of received RF signals exceeding a second level (e.g., +5 dBm) for limiting the power levels of such RF signals coupled to the attenuator in accordance with the power levels of such signals exceeding the second level. With such arrangement, the RF signals coupled to the first detector are prevented from exceeding the first level, thereby significantly reducing the DLVA's recovery time, for example to less than 500 nanoseconds.

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Cupertino, CA, United States of America

Marc R Sheade