ADJUSTABLE CIRCUIT AND RFID READER DEVICE

• US 20090224887A1
• Filed: 03/09/2009
• Published: 09/10/2009
• Est. Priority Date: 03/10/2008
• Status: Active Grant

• Current Assignee: Pepperl + Fuchs GmbH
• Original Assignee: Pepperl + Fuchs GmbH
• Inventors: Heuermann, Holger, Sadeghfam, Arash
• Granted Patent: US 8,285,214 B2
• Time in Patent Office: Days
• US Class Current: 340/10.200
• CPC Class Codes: G01S 7/038 Feedthrough nulling circuits
• CPC Class Codes: G06K 7/10009 sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver
• CPC Class Codes: H04B 5/77 for interrogation

Abstract

The present invention relates to an adjustable circuit for filtering a transmission channel of an RFID signal and for suppressing a carrier signal in the reception path between an input gate and an output gate, including at least one adjustable oscillator for generating an oscillator signal, at least one input mixing stage cooperating with the oscillator for mixing an input signal by means of the oscillator signal to an intermediate frequency and a blocking device arranged downstream of the input mixing stage or the input mixing stages for suppressing the carrier signal at the intermediate frequency.

Claims

1. Adjustable circuit for filtering of a transmission channel of an RFID signal and for suppression of a carrier signal in a reception path between an input gate and an output gate,

with at least one adjustable oscillator for generation of an oscillator signal,

with at least one input mixing stage cooperating with the oscillator for mixing of an input signal by the oscillator signal to an intermediate frequency and with a blocking device which is arranged downstream of the at least one input mixing stage for suppression of the carrier signal at the intermediate frequency.

2. Circuit according to claim 1,

wherein

the blocking device has a band-stop filter.

3. Circuit according to claim 2,

wherein

for the filtering of the transmission channel at the intermediate frequency a band-pass filter is present.

4. Circuit according to claim 3,

wherein

for the band-pass filter is arranged downstream of the band-stop filter.

5. Circuit according to claim 2,

wherein

at least one output mixing stage is arranged downstream of the band-stop filter.

6. Circuit according to claim 1,

wherein

the blocking device has a first band-pass filter for filtering of a first sideband of the input signal and a second sideband for filtering of a second sideband of the input signal.

7. Circuit according to claim 6,

wherein

a power divider is provided for division of an input signal between a first path and a second path,

that at least one first adjustable oscillator is provided for generation of a first oscillator signal,

that in the first path a first input mixing stage cooperating with the first oscillator is provided for mixing of the input signal by the first oscillator signal to a first intermediate frequency,

that the first band-pass filter is arranged downstream of the first input mixing stage for filtering of the first sideband of the input signal at the first intermediate frequency,

that in the second path a second input mixing stage cooperating with the first oscillator or a second oscillator for mixing of the input signal by the oscillator signal to a second intermediate frequency and

that the second band-pass filter is arranged downstream of the second input mixing stage for filtering of the second sideband of the input signal at the second intermediate frequency.

8. Circuit according to claim 6,

wherein

a first output mixing stage is arranged downstream of the first band-pass filter and

a second output mixing stage is arranged downstream of the second band-pass filter.

9. Circuit according to claim 6,

wherein

the first band-pass filter and the second band-pass filter are identical in construction.

10. Circuit according to claim 1,

wherein

between the at least one input mixing stage and the blocking device at least one amplifying element is provided.

11. Circuit according to claim 1,

wherein

between the at least one input mixing stage and the blocking device at least one separate amplifier is provided.

12. Circuit according to claim 1,

wherein

the at least one input mixing stage is a downconversion mixing stage.

13. Circuit according to claim 5,

wherein

the at least one output mixing stage is an upconversion mixing stage.

14. Circuit according to claim 10,

wherein

at least one input filter is provided in each case upstream of the at least one amplifying element for filtering out the carrier signal.

15. Circuit according to claim 10,

wherein

at least one quartz is provided in each case upstream of the at least one amplifying element for filtering out the carrier signal.

16. Circuit according to claim 5,

wherein

the at least one output mixing stage cooperates with the same oscillator as the at least one input mixing stage arranged in the same path.

17. RFID reader device with a circuit according to claim 1.

18. RFID-reader device according to claim 17,

wherein

a compensation circuit is provided for suppressing the crosstalk between a transmission path and a reception path of an RFID-reader unit comprising

a device for coupling out a signal portion of a carrier signal from the transmission path into a compensation path,

the compensation path having at least one variable phase shifter and at least one variable attenuator for varying the signal portion in phase and in amplitude, respectively,

a device for coupling in the signal portion varied in the phase and in the amplitude from the compensation path onto the reception path,

a unit for determining the crosstalk existing in the reception path,

and a control unit for the variable phase shifter and the variable attenuator, which is in signal connection with the unit for determining the existing crosstalk.

19. RFID-reader device according to claim 18,

wherein

between the transmission path and the reception path a circulator is provided that leads to at least one transmission/reception antenna, the transmission path being given between a transmission connection and the circulator and the reception path being given between the circulator and a receiving connection.

20. RFID-reader device according to claim 18,

wherein

on the transmission path at least one transmission antenna and on the reception path at least one reception antenna is provided, the transmission path being given between a transmission connection and the transmission antenna and the reception path being given between the reception antenna and a receiving connection.

21. RFID-reader device according to claim 18,

wherein

the device for coupling out a signal portion is a coupler and wherein the device for coupling in the signal portion varied in the phase and in the amplitude is a coupler.

22. RFID-reader device according to claim 18,

wherein

the device for coupling out a signal portion is an unsymmetrical power divider and

wherein the device for coupling in the signal portion varied in the phase and in the amplitude is an unsymmetrical power divider.

23. RFID-reader device according to claim 18,

wherein

the unit for determining the crosstalk existing in the reception path has a further coupler and a power detector.

24. RFID-reader device according to claim 18,

wherein

the unit for determining the crosstalk existing in the reception path has a further unsymmetrical power divider and a power detector.

25. RFID-reader device according to claim 18,

wherein

in the compensation path at least one of a fixed phase shifter and a fixed attenuator is arranged.

26. RFID-reader device according to claim 18,

wherein

in the compensation path at least one amplifier unit is arranged.

27. RFID-reader device according to claim 23,

wherein

an amplifier unit is employed before the power detector.

28. RFID-reader device according to claim 23,

wherein

an amplifier unit having an integrated regulation of the amplification is employed before the power detector.

29. RFID-reader device according to claim 18,

wherein

the control unit is adapted such that it adjusts the compensation path in-between individual read operations of the RFID-reader unit and

in that the control unit is adapted such that the variable phase shifter and the variable attenuator iteratively run through different combinations of attenuation and phase values, and after a run-through the range of values of attenuation and phase is restricted around a best value determined in the run-through for the crosstalk and a discretization of the attenuation and phase values is refined.