An Integrated IF Amplifier and Detector for an A.M. Upconversion Radio
This paper presents a monolithically integrated IF amplifier and envelope detector for an AM upconversion car-radio receiver. This receiver is intended for the reception of the long-wave and medium-wave frequency bands and uses an intermediate frequency of 10.7 MHz. Specific requirements resulting from the upconversion concept will be illustrated and the basic considerations for maximization of the signal-to-noise ratio as a function of the input signal level will be given. Furthermore, a new method will be presented for fixing the signal levels and the AGC speed in the amplifier. The amplifier uses two emitter-driven variable-gain pairs alternated by negative-feedback current amplifiers. It has an AGC range of 90 dB and a gain of 66 dB. The audio output level is constant within 0.2 dB over the full controll range. A cross-quad compensated envelope detector is driven at a level as low as 30 mV and shows less than 3-percent distortion at a modulation depth of 80 percent.
A High-Dynamic-Range Front End for an Upconversion Car-Radio Receiver
A monolithically integrated high-performance front end for an AM radio receiver is presented. Medium- and long-wave reception without any tuned-circuit alignments or band switches is made possible by using an intermediate frequency of 10.7 MHz, well above the maximum frequency to be received. Image- and oscillator-harmonics-related spurious responses are rejected by a simple low-pass filter. The upconversion concept puts high demands on the front-end circuits. A high intermodulation free dynamic range is realized by applying several unconventional and new circuit techniques. A low-noise low-distortion wide-band input amplifier with capacitive negative feedback realizes the required antenna match. The gain of this amplifier is automatically switched to a lower value in the vicinity of transmitters with high field strengths. A double-balanced mixer, driven by an oscillator employing a novel amplitude stabilization technique, provides the frequency conversion up to 10.7 MHz. Digital toning can be achieved very simply because only the local-oscillator frequency has to be varied. The dynamic range of this front end amounts to 130 dB. Field strengths up to about 20 and 200 mV/m can be handled without noticeable second- and third-order intermodulation, respectively.
Grazing incidence optics for wide-field x-ray survey imaging: a comparison of optimization techniques
Discussions of optimizing wide-field x-ray optics, with field-of-view less-than 1.1 degree-squared, have been made previously in the literature. However, very little has been published about the optimization of wide-field x-ray optics with larger field-of-views, which technology could greatly enhanced x-ray surveys. We have been working on the design of a wide-field (3.1 degree-squared field-of-view), short focal length (190.5 cm), grazing incidence mirror shell set, with a desired rms image spot size of 15 arcsec. The baseline design consists of Wolter 1 type mirror shells with polynomial perturbations applied to the baseline design. The overall optimization technique is to efficiently optimize the polynomial coefficients that directly influence the angular resolution, without stepping through the entire multi-dimensional coefficient space. We have investigated optimization techniques such as the downhill simplex method, fractional factorial, and response surface (including Box- Behnken and central composite) design. We have also investigated the use of neural networks, such as backpropagation, general regression, and group method of data handling neural networks. We report our findings to date.