Siemens Aktiengesellschaft

Friedrich L Kuenemund

Wilhelm Volejnik

Roland Schreiber

Hermann Betzl

Karl Traub

Hans Albsmeier

A filter circuit for electrical waves including at least one line which supplies electrical input waves and at least one line for withdrawing output electrical waves and in which the frequency dependent transmission characteristic is determined by coupled line loops each of which is in the form of a line ring and wherein coupling between the line loops is unidirectional and the individual line loops are designed so that they have unidirectional transmission characteristics.

Filter circuit for electric waves

A carrier frequency communication transmission system has a premodulation band above the transmission position of the base primary group of 60-108 kHz and utilizes mechanical filters as channel filters and also a common group filter in order to filter out the primary group band. Bending resonators having longitudinal coupling are utilized as the mechanical filters. The frequency range of the premodulation band at its lower limit is determined by a frequency spacing of at least 4 kHz from the upper band limit of the primary group band and the upper limit of the frequency range is determined in that the interfering natural oscillations, inasmuch as they occur in the lower stop band of the channel filter, lie at least 12 kHz below the lower limit of the primary group band. Highly stabilized piezo ceramics is used as the electromechanical transducer material.

Carrier frequency communication transmission system having premodulation

A switching circuit (2) consisting of CTD lines (p.sub.1,q.sub.1,p.sub.2,q.sub.2,p.sub.3,q.sub.3) is specified in which the properties characteristic for non-unidirectional microwave lines (FIG. 1) are also retained for CTD switching circuits (FIG. 2). To that end, CTD lines (for example, p.sub.1,q.sub.1) exhibiting mutually opposing conducting directions are combined into a line pair and each incoming line (p.sub.1) is connected with each out-going line (q.sub.1). The connection ensues partially via CTD lines (c.sub.1 +c.sub.1 ') and, for the other part, via a galvanic line (L.sub.1). Such switching circuits can be employed for the construction of CTD filters with steepness-increased transmission characteristic and also for the construction of correcting circuits.

Switching circuit consisting of CTD lines

An electromechanical filter comprising a plurality of parallel mounted mechanical resonators which are generally cylindrical in shape with a plurality of input and output resonators operating in a bending mode and at least one intermediate mechanical resonator operating in a torsional mode and being generally dumbbell shaped with two or more cylindrical portions connected by a torsion member and with electrostrictive transducer input and output members connected to the input and output resonators so as to provide filters having wide band characteristics.

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Munich, Germany

Friedrich L Kuenemund