Resonator configuration

#The present invention relates, generally, to a resonator system and a method for resonator tuning.

#Resonators are subject to certain manufacturing fluctuations in production. Furthermore, aging and temperature fluctuations occur during operation. This has the effect that the frequency position of a circuit resonator used in a circuit generally does not correspond exactly to the manufacturing specifications and also can vary over the course of time.

#However, it is of crucial importance, particularly in the case of modern telecommunications devices, such as, for example, mobile telephones and other mobile terminals, that circuit resonators are used with a frequency position that is predetermined as exactly as possible. This is all the more true for direct conversion methods, whose use is spreading and which can only be achieved with filters that operate extremely precisely.

#FIG. 1 shows a resonator system in accordance with the teachings of the present invention.

#FIG. 1 reveals a resonator system 1 with an antenna 2, via which a radio frequency signal is received and passed to the input 3 of the resonator system 1. The radio frequency signal is, in particular, a mobile radio signal according to the GSM or UMTS standard, a signal according to the Bluetooth standard or another digital or analog signal which serves for transmitting information. A filter 4 containing a tunable circuit resonator 5 and a second tunable circuit resonator 6 is arranged at the input 3 of the resonator system. The filter 4 is constructed as a ladder-type filter in which the circuit resonator 5 is connected in series in the radio frequency signal path, while the second circuit resonator 6 is grounded in a parallel circuit with respect to the signal path. The filtered radio frequency signal leaves the filter as output signal of the filter circuit at the filter output 7 and is mixed in a mixer 8 with an oscillator signal, generated by an oscillator 9, to form an intermediate frequency signal. Before the oscillator signal from the oscillator 9 reaches the mixer 8, it passes through a buffer amplifier 10.

#The oscillator 9 is embodied as a voltage-controlled oscillator (VCO). It is arranged with a reference resonator 11 in an oscillator circuit. The reference resonator 11 is linked into a phase-locked loop (PLL). To that end, the oscillator circuit signal is fed to a phase comparator 13 via a programmable divider 12. Via a comparison frequency generator 15, which is embodied, in particular, as a stabilized bulk acoustic oscillator, preferably as a quartz crystal, and a programmable divider 16, a comparison frequency is passed to the phase comparator 13, at whose output there is available the controlled variable UR for the reference resonator 11, the controlled variable being filtered by the low-pass filter 14. It is, thus, ensured that the reference resonator 11 has its predetermined reference value.

#The oscillator circuit signal is fed to a microcontroller 18 via an A/D converter 17. The controlled variable UR for the reference resonator 11 is used by the microcontroller 18 as a measure of the tuning of the tunable circuit resonator 5. To that end, in a manner dependent on the controlled variable UR for the reference resonator 11, a controlled variable US1 for the tunable circuit resonator 5 is calculated, which, as prescribed by the microcontroller 18, is converted by the D/A converter 19 and applied to the tunable circuit resonator 5.