Showing papers by "Ulrich L. Rohde published in 1999"

Synthesizer Design for Microwave Applications

Abstract: The following is an introduction into the PLL basics; specifically, into such items as single- and multiloop synthesizers, including the use of fractional -division and direct digital synthesizers. We will look at the advantages and disadvantages of the various systems. Probably the most critical parameter in a synthesizer is its phase-noise performance; therefore, we are going to look at the various noise contributions within a synthesizer, and finally into its resulting overall phase noise. Some of the various approaches provide less phase noise than others; they will be discussed.

Pre-selection filter for high frequency receiver

Abstract: PROBLEM TO BE SOLVED: To suppress the generation of an interfering wave, also to eliminate switch abrasion and to make life long by always connecting an input side of plural filters having a different characteristic and making a semiconductor switch that is isolated from a reception/connection circuit and arranged turn on and off each filter. SOLUTION: A filter for high frequency reception which has plural T type filters F1 to Fn that tune in to different low-pass frequency bands is always connected to a receiving antenna side E through reception/connection circuits SE1 to SEn and an output is always connected to a mixer side A through circuit SA1 to SAn. Activation and deactivation of each filter F1 to Fn are performed with the on and off of diode switches D1 to Dn which are parallelly connected to parallel resonant circuits P1 to Pn. Further, the circuit SE and SA and a parallel resonant circuit P respectively tune in to the same center frequency. Thus, an inactive filter becomes an electrode in the cutoff area of an active filter, an edge is made steep, the generation of pole due to switch-off is prevented and applied voltage is reduced. COPYRIGHT: (C)2000,JPO