Waveform generator electronics based on tuned LC circuits

1. An apparatus for generating a periodically varying electrical signal for creating a periodically varying electrical field between electrodes of an ion mobility spectrometer, comprising:

an output port;

a first tuned circuit for being electrically coupled to an external power source and for, in isolation, providing a first periodically varying electrical signal having a first frequency, the first tuned circuit coupled to the output port for providing an output electrical signal having a component at the first frequency thereto; and,

a second tuned circuit for being electrically coupled to an external power source and for providing a second periodically varying electrical signal having a second frequency different from the first frequency, the second tuned circuit coupled to the first tuned circuit for adding a component at the second frequency to the output electrical signal.

2. An apparatus according to claim 1 , wherein the first tuned circuit comprises:

at least a first inductor having a primary winding and a secondary winding;

a capacitive load coupled to the secondary winding of the at least a first inductor and including a first tunable capacitance and electrodes of an ion mobility spectrometer; and,

a load resistor coupled to the primary winding.

3. An apparatus according to claim 2 , wherein the second tuned circuit comprises at least a second inductor having a primary winding and a secondary winding, and wherein the secondary winding of the at least a second inductor is electrically coupled to a center-tap of the secondary winding of the at least a first inductor.

4. An apparatus according to claim 3 , comprising switches electrically coupled to the apparatus for in a first switched mode providing current along a first direction through the primary windings of each one of the at least a first inductor and the at least a second inductor, and for in a second other switched mode providing current along a second other direction through the primary winding of each one of the at least a first inductor and the at least a second inductor.

5. An apparatus according to claim 2 , wherein the at least a first inductor comprises two inductors coupled in series one to the other.

6. An apparatus according to claim 5 , wherein the second tuned circuit comprises two inductors coupled in series one to the other, and wherein the two inductors of the second tuned circuit are electrically coupled to a center-tap between the two inductors of the first tuned circuit.

7. An apparatus according to claim 2 , wherein the second tuned circuit comprises two inductors coupled in series one to the other, and wherein the two inductors of the second tuned circuit are electrically coupled to a center-tap on the secondary winding of the at least a first inductor of the first tuned circuit.

8. An apparatus according to claim 2 , wherein the load resistor is selected to ensure approximately sinusoidal variations in electrical currents in the primary winding.

9. An apparatus according to claim 8 , wherein the load resistor is selected such that a desired voltage of the first periodically varying electrical signal is obtained with approximately minimum consumption of power from the external power source.

10. An apparatus according to claim 2 , comprising switches electrically coupled to the apparatus for in a first switched mode providing current along a first direction through the primary winding of the at least a first inductor, and for in a second other switched mode providing current along a second other direction through the primary winding of the at least a first inductor.

11. An apparatus according to claim 1 , wherein the first frequency and the second frequency differ by a factor of substantially two.

12. An apparatus according to claim 1 , comprising a pair of electrodes disposed for forming an analyzer region therebetween.