Abstract: A phase shifter includes a transmission line and a plurality of varactor diodes connected in parallel to the transmission line. The varactor diodes have a high enough density that they uniformly load the transmission line. By controlling the reverse biasing of the varactor diodes, the phase shift produced by the phase shifter can be controlled.

Abstract: A subharmonic image rejection and image enhancement mixer for mixing millimeter wavelength signals using a low conversion loss technique is described. A local oscillator frequency from an external source is fed to a first subharmonic mixer and through a phase shifter to a second subharmonic mixer. The phase shifter delays the local oscillator signal by (90.degree./n), where n is the multiple of the subharmonic mixers and is greater than 1. The first and second subharmonic mixers mix the local oscillator frequency with an input signal, which includes a desired frequency and an image frequency, to produce an intermediate frequency having a desired component and an image component at a select phase. A 0.degree.-90.degree. hybrid separates and terminates the image component of the intermediate frequency.

Abstract: A frequency multiplier in which one or more varactors each include arrays of Schottky barrier diodes combined in rows of parallel-connected diodes and columns of series-connected diodes. The arrays are dispersed on a thermal substrate, or confined to a GaAs strip guide on a suitable substrate and in either case employed in various discrete-component or integrated circuit transmissions systems. These series-parallel arrays can be increased in size as desired for power handling capabilities or thermal dissipation and provide readily selectable impedance levels and breakdown voltages. These properties make the frequency multipliers useful in microwave and millimeter-wave systems, including those requiring high-power transmitters.

Abstract: The invention provides frequency multiplier circuitry which may be used in the output section of high power microwave systems to efficiently provide higher output frequencies. Generally, one multiplier stage may be utilized to double the frequency of the input signal with several stages being cascaded to achieve even higher frequencies. The varactor diodes utilized in circuits of the invention are preferably constructed primarily of silicon carbide, which has many advantages when compared with current varactors constructed of GaAs or silicon. Some presently preferred embodiments utilize a four terminal varactor bridge instead of a single varactor diode. The invention also teaches several significant techniques for improving the bandwidth of the circuitry, thus allowing variation of the frequency of the input signal without significantly attenuating the output signal.

Abstract: A navigation system for a vehicle travelling along a highway that has an interrogator mounted on the vehicle and, a retrodirective transponder mounted alongside the highway for updating vehicle location. For collision avoidance systems, interrogators transmit and receive fore and aft, and transponders are mounted to respond to signals fore and aft of the vehicle. The transponder modulates information onto the interrogation signal, and retransmits the encoded interrogation signal back in the direction of arrival of the collected interrogation signal. The responder uses a Van Atta array antenna and is capable of responding to an interrogator signal incident over a wide solid angle of arrival while retrodirectively retransmitting without amplification substantially all of the collected signal within a narrow solid angle. The responder may be implemented using monolithic microwave integrated circuit technology (MMIC), thus being suitable for high volume production.

Abstract: The present invention provides a monolithic superheterodyne detector pixel operable to receive a radio frequency (RF) signal at millimeter wavelength and produce a video output signal with many orders of improved sensitivity when compared with the prior art. This sensitivity improvement is achieved by translating the received RF signal to a intermediate frequency (IF) signal before detection of the video signal. At the lower frequency of the IF signal, monolithic amplification circuitry can be fabricated more easily to provide necessary gain than would be achievable if simple amplification of the RF signal were attempted. Detector pixels constructed in accordance with the invention each contain an antenna for receiving the RF signal. Local oscillator (LO) signal circuitry likewise apply an externally generated LO signal to the pixel. The RF signal and LO signal are then applied by interconnecting conductors to appropriate mixer means to produce the IF signal.

Abstract: A retrodirective interrogation responsive system wherein a responder, illuminated by an interrogator, receives an interrogation signal, modulates information onto the interrogation signal, and retransmits the encoded interrogation signal back in the direction of arrival of the collected interrogation signal. The responder uses a Van Atta array antenna and is capable of responding to an interrogator signal incident over a wide solid angle of arrival while retrodirectively retransmitting without amplification substantially all of the collected signal within a narrow solid angle. The responder may be implemented using monolithic microwave integrated circuit technology (MMIC), thus being suitable for high volume production.

Abstract: An improved distributed amplifier usable, for example, in the gigahertz frequency range for radar and electronic warfare applications is disclosed. In the amplifier stage a combination of optimum amplifier stage loading, a reflection cancelling output network, and an amplifier capacitance hiding input arrangement are employed. The disclosure includes specific component values for one embodiment of the invention.

Abstract: An improved, dual frequency transmit-receive module operable for use with two harmonically related frequencies. This dual frequency transmit-receive module utilizing; a push-pull class B power amplifier having dual output ports, a standard frequency mixer and a harmonic mixer, is operable to transmit or receive an original frequency as well as a second harmonic of that same frequency, simultaneously or at distinct, discrete intervals. This improved dual frequency transmit-receive module is operable in any radar system, using only one, or a multiplicity of antennas. However, this transmit-receive module has specific application to active aperture radar systems utilizing one antenna means for each individual transmit-receive module in an active antenna array.

Abstract: A wideband 180-degree digital phase shifter bit is provided which is operable independently of input rf frequency over a predetermined bandwidth of interest. The phase shifter bit comprises a coupled transmission line segment and a pi network segment, with switching means for alternatively connecting the rf input and rf output first to the coupled transmission line segments, and then to the pi network.

Abstract: A power amplifier that divides input power among a plurality of parallel channels through a radial line divider, amplifies the power in each channel with three terminal devices, and combines the amplified power in a radial line combiner to produce an output signal. The radial line divider/combiner includes a radial transmission line having a plurality of sectors symmetrically disposed around the inner radius of a supporting annular substrate. The sectors are connected to respective three terminal devices through microstrip transmission lines, and are isolated from laterally adjacent sectors by thin film isolation resistors.

Abstract: A harmonic mixer utilizing an anti-parallel configuration of two diodes which, when excited by a voltage waveform V.sub.LO sin .omega..sub.LO t + V.sub.s sin .omega..sub.s t where V.sub.LO is much greater than V.sub.s, yields a terminal current having angular frequency components m .omega..sub.LO .+-. n .omega..sub.s with the restriction that m + n is an odd integer. The diode configuration results in low conversion loss mixing when the local oscillator frequency is a subharmonic of the usually required local oscillator frequency, suppression of local oscillator noise sideband effects without the use of filters or hybrid junctions, and suppression of direct video detection.

Abstract: A push-pull power amplifier for amplifying an input signal is described where anti-phase signals are generated from the input signal using a first hybrid junction for driving a pair of transistors and where anti-phase transistor output signals are combined in-phase on an output line by using a second hybrid junction. An independent port may be added to the hybrid junction for isolating and terminating even order harmonics and even order intermodulation products.

Abstract: An expendable signal repeater for transmitting a replica of received signals in which the received signals are converted to an intermediate frequency by mixing in a down-converter with an upper harmonic of a heterodyning signal provided by a local oscillator; the intermediate frequency signals are delayed; and the delayed, intermediate frequency signals are converted to the transmitted signal by mixing in an up-converter with the upper harmonic of the amplified, local oscillator heterodyning signal. A mechanism is provided for switching the local oscillator between the down-converter and the up-converter during the delay of the intermediate frequency signals to prevent feedback of the transmitted signal.

Abstract: A radiometer in which independent thermal signals are combined to form first and second receiver channel input signals that are coherent with respect to each other. The first and second receiver channel input signals are independently processed in parallel receiver channels to provide first and second correlation signals, each of which include a thermal signal component and a noise signal component. The first and second correlation signals are then correlated to provide an output signal for the radiometer.

Abstract: A balanced circuit for IMPATT amplifiers and oscillators, which includes at least one pair of anti-series connected matched avalanche diodes electrically connected to the junction of a balanced and an unbalanced transmission line is disclosed. The diodes which are pumped by a large-signal input, are d-c biased to operate in the avalanche condition. A parametrically generated pair of unwanted idler frequencies are separated so that one component of the parametric-pair flows in the balanced line, and the other component flows in the unbalanced line. A central branch of the unbalanced line portion is resistively loaded to overcome the parametrically induced negative resistance of the diodes operating in the avalanche condition, and to suppress all incipient unwanted parametrically generated frequencies. The resistance loading, which is frequency independent, has little effect on the impedance presented to the diodes at the large-signal frequency.