Abstract: A novel mixer of good noise performance for operation at microwave frequencies (e.g. the 22 GHz communications band) is disclosed. The mixer comprises a waveguide to which signals and local oscillations are coupled, and from which the intermediate frequency output is derived. The principal circuitry is provided on a metallized substrate set within the waveguide in a "finline" construction. The metallized substrate performs the essential functions of impedance matching the mixer to the source of signal and local oscillations, a bridge for isolating the signal port from local oscillations and for isolating the LO port from the signal, and means to adjust the application of signal and load to the mixer diodes for optimum signal conversion. The noise figure achieved is approximately 4 db at 22 GHz, and represents an improvement over known competitive designs.

Abstract: A datum is disclosed for use as a coordinate reference in a numerically controlled machine tool. The datum which is active, consists of an elongated member, typically one half wavelength in length, supported at its center (and antinode) by a plate, and including electromechanical transducers for exciting resonance in a desired fundamental longitudinal mode. The datum is operated by an operational amplifier having the transducers connected in the amplifier feedback path. Assurance against the excitation of undesired modes is achieved by limiting the gain of the operational amplifier throughout the response band of the transducers, by use of an inductor for resonating the input capacitance of the driving transducer at the frequency of the desired mode and by gain bandwidth limits of the operational amplifier. The datum is active at an ultrasonic frequency suited to touch sensing and thus produces a response in a touch sensing system when the cutter is touched to the datum.

Abstract: The present invention relates to a mixer for use at high microwave frequencies (typically 21.8.times.23.2 GHz) in a low cost communications application. The invention utilizes low cost microwave components, including a low cost compartmented waveguide, shared by the signal and local oscillator and extensive microstrip circuitry. The provision of a pair of novel 1/4 wave impedance transformers coupled into the waveguide compartments provides efficient antenna and local oscillator input filtering, and efficient coupling from the waveguide sections to the microstrip circuitry. The mixer operation is carried out in the microstrip circuitry, which contains a hybrid coupler, a balanced diode detector, and the required mixer output filter. The arrangement is of low cost, and provides a low noise figure (7 db including the preamplifier), good band selectivity (15 db return loss over the communications band), and low local oscillator radiation.