Patent ID: 6486757
Filing Date: 2002-11-26
Classification: H03J

Abstract:
A double-tuned circuit of a tuner, comprising:a primary tuning circuit; a secondary tuning circuit; and first and second band selecting terminals to apply a changeover voltage that switches the primary tuning circuit and the secondary tuning circuit to a low-band television signal receiving mode or a high-band television signal receiving mode, wherein each of the primary tuning circuit and the secondary tuning circuit has: a varactor diode; a high-band receiving coil and a low-band receiving coil each having a first end and a second end and connected in series at the first end thereof; and a switching diode having a first end and a second end, the first end of the switching diode is connected with a connection point of the high-band receiving coil and the low-band receiving coil, the second end of the switching diode is grounded high-frequency-wise; the varactor diode is connected in parallel to the series combination of the high-band receiving coil and the low-band receiving coil, and the first end of the low-badnd receiving coil is grounded high-frequency-wise in the primary tuning circuit and the secondary tuning circuit; the second end of each of the switching diodes is connected DC-wise to the first band selecting terminal; the first end of the switching diode of one of the primary tuning circuit and the secondary tuning circuit is connected to the second band selecting terminal via a first resistor; and the first end of the switching diode of the other of the primary and secondary tuning circuits is connected to the second band selecting terminal DC-wise via the low-band receiving coil of the other of the primary and secondary tuning circuits, and wherein the first end of the switching diode in the other of the primary and secondary tuning circuits is connected to the second band selecting terminal via the low-band receiving coil and a second resistor in series.