Frequency filtering circuit for wireless communication devices

• US 20060087387A1
• Filed: 10/25/2004
• Published: 04/27/2006
• Est. Priority Date: 10/25/2004
• Status: Active Grant

• Current Assignee: Micro Mobio Corporation
• Original Assignee: Micro Mobio Corporation
• Inventors: Ichitsubo, Ikuroh, Kubota, Kanya
• Granted Patent: US 7,262,677 B2
• Time in Patent Office: Days
• US Class Current: 333/204
• CPC Class Codes: H03H 7/0123 comprising distributed impedance elements together with lumped impedance elements
• CPC Class Codes: H03H 7/1725 Element to ground being common to different shunt paths, i.e. Y-structure
• CPC Class Codes: H03H 7/1758 Series LC in shunt or branch path H03H7/1791 takes precedence
• CPC Class Codes: H03H 7/1766 Parallel LC in series path H03H7/1783 takes precedence

Abstract

Systems and methods are disclosed for a frequency filtering circuit for wireless communications that includes a first resonator circuit comprising a first transmission line and a first capacitor coupled to the first transmission line and a second resonator circuit in parallel to the first resonator circuit, said second resonator circuit comprising a second transmission line and a second capacitor coupled to the second transmission line. A coupling circuit couples the first resonator circuit and the second resonator circuit.

Claims

1. A frequency filtering circuit for wireless communications, comprising

a first resonator circuit comprising a first transmission line and a first capacitor coupled to the first transmission line;

a second resonator circuit in parallel to the first resonator circuit, said second resonator circuit comprising a second transmission line and a second capacitor coupled to the second transmission line; and

a coupling circuit that couples the first resonator circuit and the second resonator circuit.

2. The frequency filtering circuit of claim 1, wherein the coupling circuit includes

a third capacitor;

and

a first inductor in parallel to the third capacitor, wherein the third capacitor and the first inductor are coupled to the first transmission line and the second transmission line.

3. The frequency filtering circuit of claim 1, further comprising a second inductor that is connected grounded at one end and is coupled with the first capacitor and the second capacitor at another end.

4. The frequency filtering circuit of claim 1, wherein the first transmission line is grounded at first end and is connected to the first capacitor at the second end.

5. The frequency filtering circuit of claim 1, wherein the coupling circuit couples with the first resonator circuit at the first end of the first transmission line.

6. The frequency filtering circuit of claim 1, wherein the second transmission line is grounded at first end and is connected to the second capacitor at the second end.

7. The frequency filtering circuit of claim 1, wherein the coupling circuit couples with the second resonator circuit at the first end of the second transmission line.

8. The frequency filtering circuit of claim 1, wherein the layout of first transmission line or the second transmission line includes a folded hairpin geometry.

9. The frequency filtering circuit of claim 1, wherein the layout of the first transmission line and the second transmission line include substantially symmetric folded hairpin geometries.

10. The frequency filtering circuit of claim 1, wherein the length of the first transmission line is substantially one quarter of the wavelength of the resonant frequency of the first resonator circuit.

11. The frequency filtering circuit of claim 1, further comprising:

input electric signals provided to the first resonator circuit; and

output electric signals received from the second resonator circuit in response to the input electric signals, wherein the frequency performance function of the output electric signals includes at least one downward notch at a frequency adjacent to one side the pass band.

12. The frequency filtering circuit of claim 11, wherein the frequency performance function of the output electric signals forms a pass band around a peak frequency.

13. The frequency filtering circuit of claim 12, wherein the peak frequency is about 2 GHz or 5 GHz.

14. The frequency filtering circuit of claim 11, wherein the frequency performance function of the output electric signals forms a low-pass band.

15. The frequency filtering circuit of claim 11, wherein the frequency performance function of the output electric signals forms a high-pass band.

16. A wireless communications device, comprising:

a semiconductor substrate;

a frequency filtering circuit, comprising

a first resonator circuit comprising and a first transmission line fabricated on the semiconductor substrate and a first capacitor coupled to the first transmission line;

a second resonator circuit in parallel to the first resonator circuit, said second resonator circuit comprising a second transmission line fabricated on the semiconductor substrate and a second capacitor coupled to the second transmission line; and

a coupling circuit that couples the first resonator circuit and the second resonator circuit.

17. The wireless communications device of claim 16, wherein the frequency filtering circuit is fabricated on the semiconductor substrate.

18. The wireless communications device of claim 16, wherein the semiconductor substrate is a passive semiconductor substrate.

19. The wireless communications device of claim 16, wherein the coupling circuit includes

a third capacitor;

and

a first inductor in parallel to the third capacitor, wherein the third capacitor and the first inductor are coupled to the first transmission line and the second transmission line.

20. The wireless communications device of claim 16, wherein the coupling circuit includes a second inductor that is connected grounded at one end and is coupled with the first capacitor and the second capacitor at another end.

21. The wireless communications device of claim 16, wherein the first transmission line is grounded at first end and is connected to the first capacitor at the second end.

22. The wireless communications device of claim 16, wherein the coupling circuit couples with the first resonator circuit at the first end of the first transmission line.

23. The wireless communications device of claim 16, wherein the second transmission line is grounded at first end and is connected to the second capacitor at the second end.

24. The wireless communications device of claim 16, wherein the coupling circuit couples with the second resonator circuit at the first end of the second transmission line.

25. The wireless communications device of claim 16, wherein the layout of first transmission line or the second transmission line includes a folded hairpin geometry.

26. The wireless communications device of claim 16, wherein the layout of the first transmission line and the second transmission line include substantially symmetric folded hairpin geometries.

27. The wireless communications device of claim 16, wherein the length of the first transmission line is substantially one quarter of the wavelength of the resonant frequency of the first resonator circuit.

28. The wireless communications device of claim 16, further comprising:

input electric signals provided to the first resonator circuit; and

output electric signals received from the second resonator circuit in response to the input electric signals, wherein the frequency performance function of the output electric signals includes at least one downward notch at a frequency adjacent to one side the pass band.

29. The wireless communications device of claim 28, wherein the frequency performance function of the output electric signals forms a pass band around a peak frequency.

30. The wireless communications device of claim 29, wherein the peak frequency is about 2 GHz or 5 GHz.

31. The wireless communications device of claim 16, wherein the frequency performance function of the output electric signals forms a low-pass band.

32. The wireless communications device of claim 16, wherein the frequency performance function of the output electric signals forms a high-pass band.