Abstract: A power control system for a multi-carrier base station transmitter is capable of controlling power levels of individual RF carriers. The power control system has a multi-channel conversion system for generating a plurality of analog reference signals corresponding to a plurality of digital input signals. The multi-channel conversion system also generates an analog multi-carrier signal and samples the multi-carrier signal. The multi-carrier signal represents a summed amplification of the digital input signals. A correlating power detection system is connected to the multi-channel conversion system and generates digital total power control signals based on the analog reference signals and the analog sampled multi-carrier signal. A feedback conversion module is connected to the multi-channel conversion system and the correlating power detection system and individually controls amplification of the digital input signals based on the total power control signals.

Abstract: A two stage mixer is configured to reduce the power levels of out of band spurious output signals or spurs, such as the leakage from the second stage mixer by way of phase modulation power spreading. The local oscillator signal applied to first mixer stage is phase modulated while the local oscillator signal applied to the second mixer stage is inverse modulated. As such, a problematic spur, such as leakage from the local oscillator applied to the second mixer stage is spread so that the power levels of the spur are distributed a wider bandwidth instead of concentrating the power levels at single frequencies, thus reducing the power level at any single frequency. By utilizing phase modulation, the need for relatively complex and expensive filters is eliminated.

Abstract: An optical device for use with an optical input beam comprising an optical thresholding device positioned along an optical path defined by the propagation direction of the optical input beam. If the combined intensity of the optical input beam and a control beam exceeds a threshold level, the optical beam passes through the thresholding device. Preferably, the optical thresholding device is a saturable absorber. When the device is configured as an optical comparator, the intensity of the optical input beam exceeds the threshold level and the thresholding device saturates and turns transparent so that the control beam passes through the thresholding device as an optical indicator beam. When the device is configured as an optical signal attenuator and the intensity of the optical input signal is negligible compared to that of the control beam, the combined intensity of the beams does not saturate the thresholding device.

Abstract: A method of manufacturing a HEMT IC using a citric acid etchant. In order that gates of different sizes may be formed with a single etching step, a citric acid etchant is used which includes potassium citrate, citric acid and hydrogen peroxide. The wafer is first spin coated with a photoresist which is then patterned by optical lithography. The wafer is dipped in the etchant to etch the exposed semiconductor material. Metal electrodes are evaporated onto the wafer and the remaining photoresist is removed with solvent.

Abstract: An optical inverting system employs a first optical structure having an index of refraction that varies with the intensity of an incident beam and a second optical structure having a constant index of refraction, and forming an interface therebetween. An optical pulse stream is combined with a laser beam and the combined beam is applied to the first optical structure, impinging the interface at a predetermined angle of incidence. If the angle of incidence is less than a critical angle, the beam is refracted into the second optical structure. If the angle of incidence is greater than the critical angle, the beam is completely reflected at the interface. Thus the output of the second optical structure is an inversion, and the output of the first optical structure is a level shifted replica, of the optical digital pulse stream.

Abstract: A time multiplexed multiple carrier transmitter includes a first data encoder that produces first transmit data and a second data encoder that produces second transmit data. In addition, the transmitter includes a digital multiplexer coupled to the first and the second data encoders. The digital multiplexer provides a transmit signal output. A transmit frequency upconverter coupled to a power amplifier and the transmit signal output provides a final upconversion (or direct upconversion) to a transmit frequency for each channel. The transmitter also includes a multiplexer control circuit coupled to the digital multiplexer through a multiplexer control input. The multiplexer control circuit produces a multiplexer control signal on the multiplex control input that selects between the first and second data encoders according to a transmit schedule. The transmit schedule determines when, at the frequency at which, the transmitter selects and transmits data from each data encoder.

Abstract: An optical inverting system employs a first optical structure having an index of refraction that varies with the intensity of an incident beam and a second optical structure having a constant index of refraction, and forming an interface therebetween. An optical pulse stream is combined with a laser beam and the combined beam is applied to the first optical structure, impinging the interface at a predetermined angle of incidence. If the angle of incidence is less than a critical angle, the beam is refracted into the second optical structure. If the angle of incidence is greater than the critical angle, the beam is completely reflected at the interface. Thus the output of the second optical structure is an inversion, and the output of the first optical structure is a level shifted replica, of the optical digital pulse stream.

Abstract: Fast switching and fast settling is achieved in a phase locked loop (“PLL”) containing a bandwidth switched active loop filter (8) by feeding the phase error signal of the phase detector (1) of the PLL to the non-inverting input of the amplifier (7) within the loop filter and having the electronic switch (17) control the loop filter bandwidth through changing the resistance (9, 11) to ground at the inverting input of the amplifier between a high and low value associated respectively with broad bandwidth and narrow bandwidth to the loop filter. Switching is possible in as little as one microsecond, and is accompanied by fast settling of the loop with minimal generation of phase/frequency perturbation. The foregoing PLL is of particular benefit in fast switching frequency synthesizers, such as used in frequency hopping frequency synthesizers of frequency and time division multiplexing systems.

Abstract: A variable delay line detector (34, 48, 66)includes a power splitter (36, 50, 68), a mixer (44, 62, 72) and a variable delay line (42,52, 70). Various devices are suitable for the variable delay line (42, 52, 70), such as a non-linear transmission line (NLTL). By providing a variable delay line, the variable delay line detector (34, 48, 66) is adapted to be programmed in real time thus making it suitable in applications where the phase and or frequency of the input signal varies. As such, the variable delay line detector (34, 48, 66) may be used in applications heretofore unknown, such &a an inexpensive demodulator in a frequency hopped spread spectrum system.

Abstract: An optical device for use with an optical input beam comprises and optical thresholding device having a predetermined threshold level, and is positioned along an optical path defined by the propagation direction of the optical input beam. A source generates a control beam through the optical thresholding device, wherein if the combined intensity of the optical input beam and the control beam is large enough to exceed the threshold level of the thresholding device, the optical beam passes through he thresholding device. The thresholding device attenuates the optical beam as it passes therethrough. In a preferred embodiment, the optical thresholding device is a saturable absorber.

Abstract: An optical device for use with an optical input beam comprises and optical thresholding device having a predetermined threshold level, and is positioned along an optical path defined by the propagation direction of the optical input beam. A source generates a control beam through the optical thresholding device, wherein if the combined intensity of the optical input beam and the control beam is large enough to exceed the threshold level of the thresholding device, the optical beam passes through he thresholding device. The thresholding device attenuates the optical beam as it passes therethrough. In a preferred embodiment, the optical thresholding device is a saturable absorber.

Abstract: An optical device for use with an optical input beam comprises and optical thresholding device having a predetermined threshold level, and is positioned along an optical path defined by the propagation direction of the optical input beam. A source generates a control beam through the optical thresholding device, wherein if the combined intensity of the optical input beam and the control beam is large enough to exceed the threshold level of the thresholding device, the optical beam passes through he thresholding device. The thresholding device attenuates the optical beam as it passes therethrough. In a preferred embodiment, the optical thresholding device is a saturable absorber.

Abstract: A programmable phase shifter (20, 40, 54, 60, 62) includes a variable delay line formed from a nonlinear transmission line (NLTL) (26, 28, 46, 28), which enables the device to be used in applications where the frequency of the input signal varies. A variable DC bias applied to the NLTL (26, 28, 46, 48) varies the NLTL's phase velocity and delay. Since the characteristic impedance of a transmission line changes as a function of the DC bias, the input voltage standing wave ratio (VSWR) also changes. In order to compensate for the change in the input VSWR, a pair of NLTLs (26, 28, 46, 48) are coupled at the input and output to a pair of hybrid couplers (22, 42). In an alternate embodiment of the invention, the hybrid couplers (22, 24) are replaced with 180° power splitters (42, 44) in order to reduce distortion of the device. In other embodiments of the invention (40, 54), a nonlinear transmission lines are used to form both discretely variable and continuously variable digital phase shifters (60, 62).

Abstract: An adaptive transceiver architecture which reallocates communications resources in real time based on the amount of bandwidth being used in communications channels in the system. The transceiver receives communications signals from a plurality of communications beam spots. Each communications beam spot has a predefined bandwidth divided into non-overlapping subbands. The transceiver further comprises a plurality of front end signal conditioners for receiving communications signals from an equal plurality of communications beam spots. A predetermined number of the conditioned signals are then combined by an interconnect. The interconnect receives composite signals from the front end signal conditioners, and it combines at least first and second communications signals from first and second respective composite signals to form an output processing signal.

Abstract: An apparatus (800) and method (1000) for forming a shapeable and directable composite beam (305) from a plurality of pixel beams (302). The apparatus (800) includes a front-end unit (810) which communicates element signals through antenna array elements (808). The apparatus (800) also includes a back-end unit (850) which forms the composite beam from a set of pixel beams by converting between a composite signal and a set of corresponding pixel signals. The back-end unit (850) further adjusts the amplitude and phase of the set of pixel signals to form the composite beam. The apparatus (800) further includes an interconnecting beamforming network (820) interposed between the back-end unit (850) and the front-end unit (810) which couples the back-end unit (850) to the front-end unit (810) by converting between the pixel signals of the back-end unit (850) and the element signals of the front-end unit (810). The method (1100) includes determining a desired shape and direction for the composite beam (1110).

Abstract: An optical analog-to-digital converter (10) that makes use of a downward-folding successive approximation conversion scheme that employs subtraction of optical signals. A pulsed optical signal (20) to be converted is applied as an input to each of a plurality of converter channels (12, 14, 16, 18), where each channel (12, 14, 16, 18) outputs one of the bits of the digital output of the converter (10). The input signal (20) to each channel (12, 14, 16, 18) is sent to a thresholding device (24, 40, 60, 80) that determines whether the intensity of the signal is greater than or less than a predetermined threshold value. The first channel thresholding device (24) compares the input signal (20) to a threshold value that is one-half of a known maximum intensity. Subsequent channel thresholding devices (40, 60, 80) compare the input signal to a threshold value that is one-half of the intensity used in the previous channel in a downward-folding scheme.

Abstract: A nonlinear transmission-line waveform generator for generating a comb of frequencies and relatively short duration pulses, for example, in the range of picoseconds and tens of picoseconds, that are adapted to being utilized with ultra wideband radios in order to improve the bandwidth of such radios by an order of magnitude, for example, up to tens and even hundreds of GHz. In particular, the nonlinear transmission line waveform generator in accordance with the present invention consists of a microstrip or coplanar waveguide line. In accordance with an important aspect of the invention, the &Dgr;C/&Dgr;V characteristic of the nonlinear transmission line is matched to the frequency and amplitude of the input sinusoid. By matching the &Dgr;C/&Dgr;V characteristics of the nonlinear transmission line to the input sinusoid, the output of the nonlinear transmission line produces a comb of frequencies that are multiples of the input sinusoid frequency, making it suitable as a harmonic generator.

Abstract: A dual phased array payload (100) for use onboard a communications satellite is disclosed. The payload includes one or more phased array receive antennas (102-108) including numerous individual receiving elements distributed in a predetermined configuration. Each of the individual radiating elements is selectively adjustable in amplitude and phase to achieve scanning beams for receiving information transmitted from the ground in an uplink beam. The payload includes a packet switch (114) connected to the phased array receive antennas (102-108). The packet switch (114) includes a set of inputs and a set of outputs. The set of inputs are selectively connectable to the set of outputs. The payload (100) includes one or more phased array transmit antennas (120-126) connected to the packet switch (114). The phased array transmit antennas (120-126) include numerous individual radiating elements distributed in a predetermined configuration.

Abstract: The optical hold unit (100) of the present invention includes an optical modulator (108) that has an electrical input, an optical input, and an optical output. A 1.times.N optical splitter (106) is also provided that has an optical input and N optical outputs. In addition, N optical paths (112) are individually coupled to the N optical outputs and carry one of the N output signals. Each optical path has an associated propagation delay. Optical delay elements may be located in any of the N optical paths that carry the output signals. The optical delay elements serve to lengthen the propagation delay (114a-e) of the optical path (112a-e) in which the optical delay element is located. In an alternative embodiment, the optical hold unit (200) includes an optical modulator (108) that has an electrical input, an optical input, and an optical output. An optical resonator (202) is also provided and connected to the optical output of the modulator (108).

Abstract: An optical quantizer (10) that employs a chain of optical thresholding devices (16) positioned in the propagation path of an optical input beam (12) to be quantized. Each optical thresholding device (16) saturates and turns transparent if the intensity of the optical beam (12) that impinges it is above a predetermined threshold level designed into the device (16). If the input beam (12) saturates the optical thresholding device (16), the device (16) outputs an indicator signal (22) identifying the saturation. The input beam (12) propagates through the optical thresholding device (16) with some attenuation caused by the saturation, and impinges subsequent optical thresholding devices (16) in the chain. Eventually, the attenuation of the input beam (12) caused by the multiple saturations will decrease the beam intensity below the threshold level of the next optical thresholding device (16). The number of indicator signals (22) gives an indication of the intensity of the input beam (12).