NULL-IF CONVERTER WITH RC FILTER

摘要

PROBLEM TO BE SOLVED: To obtain a null-IF converter with high quality where a phase and an amplitude between two signals or more are very stable. SOLUTION: A filter respectively provided to each path for two base band signals I, Q. A thin film component is provided, which has two RC filters each consisting of a resistor and a capacitor having a lower electrode, an upper electrode 1 and a dielectric material 2. The RC filters are laid out on a common substrate. In the capacitor whose capacitance is 55 pF/mm2, a Si3N4 made dielectric layer with a thickness of 1.1μm is deposited on a lower electrode having a NiCrAl resistance layer whose surface resistance is 8.5 ohm/(square). A NiCrAl resistance layer whose surface resistance is 100 ohm/(square) as the upper electrode is placed on the lower electrode. The lower resistance layer configures a distributed notch resistor and is electrically grounded when the filters are in operation.