VARACTOR TUNED MULTI-LAYER CERAMIC FILTER WITH EMBEDDED VOLTAGE MULTIPLIER
Original Publication Date: 2003-Jun-25
Included in the Prior Art Database: 2003-Jun-25
Combining discrete parts with Multi-Layer Ceramic (MLC) technology is a well known concept employed in pre-selector filter design. This circuit re-uses this concept and expands it by including a Voltage multiplier, along with a varactor tuned filter, in the Multi-Layer Ceramic wafer.
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Combining discrete parts with� Multi-Layer Ceramic (MLC) technology is a well known concept employed in pre-selector filter design. This circuit re-uses this concept and expands it by including a Voltage multiplier, along with a varactor tuned filter, in the Multi-Layer Ceramic wafer.
� DC voltage Multiplier circuits are typically stand-alone, external devices whose outputs are applied to the controlled device. Combining a voltage multiplier with the filter on the same Multi-Layer ceramic wafer will result in increased design flexibility by allowing the filter designer more control over the tuning voltage range. The suggested multiplier circuit requires an input AC voltage and employs several well known concepts including, a capacitive transformer, a series resonant network, and full wave rectification to realize a high DC voltage.�
� Control Voltage is provided by a DAC as with other designs except that the DAC voltage is not applied directly to the filter varactors.� Instead, it is applied to the voltage multiplier circuit first. The DAC voltage controls the Q of a resonant circuit� via a varactor and capacitive transformer circuit which in turn control a rectified, differential DC voltage at the multiplier output. That is, the multiplier’s output voltage is set by controlling the transformation ratio of a capacitive transformer at the multiplier’s input.� This is achieved by controlling the series capacitance of the transformer via a DAC driven varactor circuit.
The capacitive� transformer (Figure 1) reduces the output resistance of the input AC signal source by a factor of .� This results in a higher loaded Q...