1. Field of the Invention
The present invention relates to resonators having ready-to-use conductor lines mounted with other circuit components on printed circuit boards, and more particularly relates to a resonator in which inductance or impedance may be varied uniformly in the longitudinal direction of a conductor line.
2. Description of the Related Art
A resonator, for example, for determining the oscillating frequency of a voltage-controlled oscillator, has been constructed with a strip conductor line directly formed on a printed circuit board on which other circuit components for the circuit construction are mounted.
FIG. 7 illustrates a conventional resonator. In FIG. 7, a printed circuit board 21 has circuit components (not shown) constituting the voltage-controlled oscillator or the like, mounted thereon. A strip conductor line 22 is directly formed on this printed circuit board 21 and is connected to circuit components.
For example, when the oscillating frequency is adjusted, as shown in FIG. 8, the inductance or the impedance of the resonator is varied by locally changing the width of a slit 23 provided in the conductor line 22.
As described above, the conventional resonator, in which the conductor line 22 is used, is directly formed on the printed circuit board on which circuit components are mounted. Accordingly, in a case where conductor lines 22 having different widths or different lengths are required, since the design for each printed circuit board is different, a universal printed circuit board cannot be designed.
Since the oscillating frequency is adjusted by locally changing the width of the slit 23, the inductance or the impedance of the conductor line 22 varies in accordance with the position of the conductor line 22 in the longitudinal direction thereof. In order to secure the required range of frequency change, the optimal position of the slit 23 must be selected. Moreover, the impedance locally increases in the periphery of the slit 23. Additionally, as the width of the conductor line 22 decreases, loss therein increases and the Q-factor therein decreases.