Varactor element and low distortion varactor circuit arrangement
AssigneeTechnische Universiteit Delft
InventorLeonardus Cornelis Nicolaas De Vreede
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Abstract
A varactor element having a junction region, in which the depletion capacitance of the varactor element varies when a reverse bias voltage is applied to the varactor element. The varactor element has an exponential depletion capacitance-voltage relation, e.g. obtained by providing a predetermined doping profile in the junction region. The varactor element can be used in a narrow tone spacing varactor stack arrangement, in which two varactor elements are connected in an anti-series configuration. A low impedance path for base band frequency components between a control node and each of two RF connection nodes is provided, while for fundamental and higher order harmonic frequencies, a high impedance path is provided.
Claims19
A varactor stack circuit arrangement, comprising:
- two varactor elements each having two terminals and comprising:
- a junction region, in which the depletion capacitance of the varactor element varies when a reverse bias voltage is applied to the varactor element, wherein the varactor element has an exponential depletion capacitance-voltage relation, in which the junction region comprises a single sided junction;
- the varactor element is provided with a doping profile substantially defined by:
- N
-
- (
- x
- )
- =
- N
- /
- (
- x
- x
- low
- )
- m
- wherein N(x) is the varactor element's doping concentration in one dimension as a function of x (for x>xlow), where x is a distance from the single sided junction, N is a predefined doping concentration constant, and m is an exponential factor;
- the junction region comprises a filling layer in an interval of distances lower than xlow with a doping concentration of Nfill lower than the doping concentration at distance xlow (N(xlow));and
- the two varactor elements are connected in an anti-series configuration, such that a control node is provided by two interconnected terminals and two RF connection nodes by the other terminals.
Dependencies are inferred from the claim text.