Patent ID: 8169269

Claim:
A Hartley voltage controlled oscillator (VCO) circuit comprising two inductors (L d , L g ), a transistor (Q 1 ) and a varactor (C) wherein the two inductors (L d , L g ) are arranged as a coupled inductor pair operable to enable positive mutual inductance (M) between them, wherein the arrangement comprising four inductors (L d1 , L g1 , L d2 , L g2 ) arranged into two coupled inductor pairs, two varactors (C 1 , C 2 ), and two transistors (Q 1 , Q 2 ), wherein: the first varactor (C 1 ) is arranged between first and second terminals (Q 11 , Q 12 ) of the first transistor (Q 1 ); a third terminal (Q 13 ) of the first transistor (Q 1 ) is grounded; a first inductor (L g1 ) is arranged between the first terminal (Q 11 ) and a first bias voltage source (V DD ) a second inductor (L g1 ) is arranged between the first terminal (Q 11 ) and a second voltages source (V g ); the second varactor (C 2 ) is arranged between a first and a second terminal (Q 21 , Q 22 ) of the second transistor (Q 2 ); a third terminal (Q 23 ) of the second transistor (Q 2 ) is grounded; a third inductor (L d2 ) arranged between the first terminal (Q 21 ) and the first bias voltage source (V DD ); a fourth inductor (L g2 ) is arranged between the first terminal (Q 21 ) of the second transistor (Q 2 ) and the second bias voltage source (V g ); and wherein the first inductor (L d1 ) and the fourth inductor (L g2 ) are arranged as a first coupled inductor pair, and the second inductor (L g2 ) and the third inductor (L d2 ) are arranged as a second coupled inductor pair to provide positive mutual inductance (M).