Extremely high-Q tunable inductor for Si-based RF integrated circuit applications

Experimental study of integrated tunable transformer

“…This results indicate that maximizing the Q p leads to a higher G MSG , which agreed with the simple analysis of maximum available gain discussed in [8]. This, however, can be disadvantage of tunable inductors [5,6] because the power coupled between the inductor and other components [9] can be larger than conventional inductors when the quality factor of the tunable inductors is maximized. The input impedance is given by…”

“…The tuning technique can provide impedance matching at a frequency by adjusting the input power to drive the coupled inductor. Note that the measurement results reported in [5] reveal that a variety of power levels changes the real and imaginary parts of the input impedance of a tunable inductor. These results show that the proposed tunable transformer is useful for RF IC designs because of its higher performance compared to the conventional transformer used in RF ICs.…”

“…Moreover, the transformer winding configuration improves the quality factor of each spiral winding compared to separated inductor topology [3]. A frequency tuning method with varactors is, however, widely employed in transformer-based circuits [1,4], although advanced tuning techniques with magnetically coupled inductors have been reported [5,6]. This paper presents a tunable transformer topology in conjunction with its tuning technique based on the concept of magnetically tunable inductor [5].…”

“…A frequency tuning method with varactors is, however, widely employed in transformer-based circuits [1,4], although advanced tuning techniques with magnetically coupled inductors have been reported [5,6]. This paper presents a tunable transformer topology in conjunction with its tuning technique based on the concept of magnetically tunable inductor [5]. The maximum stable gain G MSG [7] and input impedance Z in of a conventional transformer, and the quality factor of the primary winding Q P are tuned.…”

“…Figure 1 shows a die microphotograph of the proposed 3-port tunable transformer and the exploded view. A simple tunable spiral inductor structure [5] (a) (b) was extended to the tunable transformer topology. A spiral microstrip line of the tunable inductor is utilized as the primary winding of the tunable transformer, while the other spiral is used as the coupled inductor.…”