| 摘要 |
<p>TV-RF input circuit provided with an RF coupling device via which an aerial input is coupled to first, second and third parallel tunable RF resonant circuits (11, 21, 31) for a parallel selection of a desired frequency in first, second and third TV frequency bands (50 - 160 MHz; 160 - 470 MHz; 470 - 860 MHz) substantially succeeding one another in frequency, said RF coupling device having a high-pass eta -section (C, L2, L3) for suppressing frequencies below the first TV frequency band and being provided with a capacitive series branch and first and second inductive shunt branches, said eta -section (C, L2, L3) being coupled via a first series inductance (L1) to the first RF resonant circuit (11). In order to ensure, without extra elements, a substantially reflection-free supply of TV-RF reception signals to each of the said RF resonant circuits, second and third series inductances (L2, L3) of mutually equal order are arranged in the first and second inductive shunt branches, respectively, which inductances are coupled at one end to either side of a capacitor (C) arranged in the capacitive series branch and at the other end to the second and third RF resonant circuits (21, 31), respectively, said first series inductance (L1) being at least several times larger than each of the two other series (L2, L3) inductances.</p> |
