Abstract: A phased-array antenna (14) is disclosed including modules (12) that respond to optic signals provided by a central processor (16) vai an optic feed network (18). In a transmit mode of operation, the central processor provides optic transmit signals to the modules, controlling the phase and attenuation of the various signals to accomplish the desired steering of the antenna beam produced by the array. A mixer or avalanche photodiode (42) in each module provides suitable optical-to-RF power conversion for the input signal to allow antenna elements (44) in the module to radiate the desired electromagnetic beam. During a receive interval, a received electric signal produced by the antenna elements is combined by the mixer with a local oscillator frequency optic signal applied to the mixer by the central processor. As a result, the RF frequency of the received signal is reduced to an IF frequency for low-cost amplification by an amplifier (52).

Abstract: The optical receiver has a photodiode (10) which is reverse biased by a voltage supply (14). The voltage supply provides a variable bias voltage determined by a control unit (16) and the photodiode is matched to the load (22) by an impedance matching circuit (12). The photodiode exhibits large capacitance changes over a range of bias voltages and may be implemented using a Schottky barrier or P.sup.+ N photodiode. By changing the bias voltage, the photodiode capacitance changes to vary the tuned frequency of the receiver. The matching circuit cancels the reactive component of the photodiode impedance and matches the resistive component to the load. The photodiode may have a doping profile in which an intrinsic or lightly doped region of width greater than the average photon penetration depth is located next to the junction. After the intrinsic region, the doping profile may be selected to achieve linear tuning. This doping profile gives linear tuning without sacrificing photodiode conversion efficiency.

Abstract: A portion of a radar transmit pulse is inserted into a recirculating delay line having a one cycle delay equal to the duration of a transmit pulse. A pulse train coupled from the recirculating delay serves as a local oscillator for the radar receiver. The delay medium may be an optical fiber, a coaxial transmission line or a surface acoustic wave (SAW) device.

Abstract: The optical power emitted from a light energy producing diode is stabilized over temperature using a simple bias circuit consisting of a voltage source with a series resistance or a current source with a shunt resistance. The bias circuit resistance is equal to the slope of the bias line formed by the constant optical power bias points of the diode plotted on a voltage versus current graph. The voltage source or current source value in the bias circuit is equal to the zero current or zero voltage intercept value, respectively.

Abstract: A device for receiving intensity modulated optical input signals, and producing an electronic output signal having a magnitude corresponding to the sum of the intensities of the input signals. The device comprises a plurality of photodetectors for receiving the input signals, the photodetectors being connected in parallel between first and second conductor lines. The photodetectors are reverse biased, preferably through a low pass filter, and a high pass filter is positioned between the conductor lines and a pair of output terminals at which the output signal is produced. The device may also include frequency compensation and/or impedance matching means connected between the high pass filter and the output terminals. Where the input signals are provided on fiber-optic cables or optical waveguides, means may also be provided for positioning the fiber-optic cables or waveguides such that the input signals are efficien=tly coupled onto the photodetectors.

Abstract: The corporate feed network employs light emitting opto-electronic components, such as laser diodes (12), connected together in a string (14) for distributing RF, microwave, MMW, digital signals, and pulse modulated light. Each diode provides two ports or facets which are coupled to optical fibers (16, 18) to connect to an active phased array antenna, for example. The diodes are selected in number and impedance to provide a good wideband impedance match to the RF/microwave/MMW/digital driving source. Multiple series strings of diodes may be employed, connected in parallel for larger corporate feed structures.

Abstract: A pulse modulator including a pulse forming network comprising a multiple section ladder network of series inductors and shunt capacitors. The series inductors are flat, spiral inductors etched on microstrip. The pulse forming network is charged negatively through an IMPATT diode, and is switched to ground by a set of p-channel VMOS power FETs. By switching off the FET switches before the pulse forming network is completely dicharged, the fall time of the current pulse is reduced. The shape of the current pulse can be adjusted by varying the impedance of the section or sections of the pulse forming network whose position in the network corresponds to the position in the current pulse which it is desired to change. The variation in impedance is realized by bringing metallic slugs, mounted in the housing of the pulse forming network, into proximity with the flat, spiral inductors.