| 摘要 |
1,228,081. Variable capacitors. ROHDE & SCHWARZ. 21 March, 1969 [10 April, 1968; 4 Dec., 1968], No. 14854/69. Headings H1M and H1R. [Also in Division H3] In a tunable oscillator, band switching is obtained by switching on and off the supply voltage to one of a number of oscillator units E1, E2, E3, the individual oscillator units each include an active oscillating element T and are mounted on sector shaped boards P1, P2, P3 which are arranged around a common rotary capacitor rotor and an individual stator body C1, C2 is mounted on each sector so as to cooperate capacitively with the rotor D1, D2. Each oscillator E1 may include a transistor T (Fig. 3) and is formed as a printed circuit on a ceramic board P1, P2, P3. The stator plates C1 and C2 are similarly formed as printed circuits on opposite sides of these boards P1-P3 to co-operate with two rotary plates D1, D2 operated by a spindle W. The capacitor C3 is formed by a piston type trimmer attached to plate D1 by a disc D4. When the spindle W is rotated the oscillator which is ON is tuned through its band by the rotary plate of the common rotor. At the end of its band microswitches V are operated to disconnect the supply to oscillator E1 and connect it to E2 which is then tuned through its band by the rotor and so on for E3. A seal may be marked on a drink which rotates with the spindle W and co-operates with a pointer Z. The spindle may have a fine and coarse drive. The oscillator units may be tuned to bands which are not adjacent or to a continuous succession of bands and automatic scale switching after completion of a band may be provided by a reduction gear between the rotor shaft and the pointer Z so that all scales may have the same starting point. By making ring D3 between the rotor plates D1, D2 of a material having about the same co-efficient of thermal expansion as ceramic variation of frequency with temperature is minimized. The rotor plate is preferably 360-360 degrees divided by the number of sector boards P1-P3. The peripheral shapes of the stator plates Cl are selected so as to provide a linear scale and C2 provides a linear frequency modulation characteristic. Frequency modulation is obtained by varying the potential on a voltage variable capacitor H. In a modified oscillator unit (Fig. 4, not shown), the voltage variable capacitor (11) is connected between a tapping on inductor L and via a trimmer (12) to C2, C1 being connected to the end of the inductor L. The oscillator may be encapsulated by a housing G. |
