Adjustable capacitative element
View Patent ↗The invention relates to an adjustable capacitative element which can assume discrete capacity values the impedance values Z i of which that it can assume are distributed as evenly as possible in the Smith Chart. An adjustable capacitative element comprises a capacitor which can assume discrete capacity values. The phase of the reflection factor or the impedance values of the capacity values are interspaced equidistantly.
1. An adjustable capacitive element, comprising a capacitor which is intended to accept n+1 discrete capacitance values C 0 to C n , wherein
the capacitance values C i from C 0 to C n are chosen such that a set of impedance values Z i , which are dependent on the capacitance values, from Z 0 =Z(C 0 ) to Z n =Z(C n ) or a set of phase values φ i (C i ), which are dependent on the capacitance values, from φ 0 (C 0 ) to φ n (C n ) are at equidistant intervals, where n is an integer greater than one,
Z(C) is the frequency-dependent impedance of the capacitive element,
φ(C) is the phase of the reflection factor
ρ
=
Z
-
Z
0
Z
+
Z
0
,
and
Z 0 is a standard impedance.
2. The adjustable capacitive element according to claim 1 , comprising a capacitor which is intended to accept n+1 discrete capacitance values C 0 to C n , wherein
the n+1 impedance values Z i (C i ) from Z 0 (C 0 ) to Z n (C n ) are at equidistant intervals, and
C
i
=
1
ω
Z
i
,
where ω is the angular frequency of a radio-frequency signal.
3. The adjustable capacitive element according to claim 2 , wherein
the adjustable capacitive element is connected in series in the RF signal path of an impedance matching circuit, and
a digitally tunable capacitance bank is connected in a parallel path between the RF signal path and ground.
4. The adjustable capacitive element according to claim 1 , comprising a capacitor which is intended to accept n+1 discrete capacitance values C 0 to C n , wherein
the n+1 phase values φ i (C i ) from φ 0 (C 0 ) to φ n (C n ) are at equidistant intervals and
C
i
=
1
ω
Z
0
-
sin
ϕ
i
(
1
+
cos
ϕ
i
)
,
where ω is the angular frequency of a radio-frequency signal.
5. The adjustable capacitive element according to claim 1 , wherein the capacitor comprises
a varactor,
a capacitance bank having capacitance elements which can be individually connected, or
at least two capacitance elements which can be exclusively individually connected.
6. The adjustable capacitive element according to claim 1 , the capacitor of which also comprises two digitally adjustable capacitance banks which provide piece-by-piece linear approximation of contiguous capacitance ranges.
7. The adjustable capacitive element according to claim 1 , wherein the adjustable capacitive element is connected in series in an RF signal path of an impedance matching circuit.
8. The adjustable capacitive element according to claim 1 , wherein
the adjustable capacitive element is connected in an impedance matching circuit,
the impedance matching circuit comprises an RF signal path, and
the adjustable capacitive element is connected in a parallel path between the RF signal path and ground.
9. The adjustable capacitive element according to claim 1 , wherein the standard impedance is 50 ohms.
10. The adjustable capacitive element according to claim 1 , wherein the capacitor comprises cascaded capacitance elements.