Radio-frequency signal frequency conversion device for a low power rf receiver

• US 20040248537A1
• Filed: 02/10/2004
• Published: 12/09/2004
• Est. Priority Date: 08/10/2001
• Status: Active Grant

• Current Assignee: Asulab SA (The Swatch Group AG)
• Original Assignee: Asulab SA (The Swatch Group AG)
• Inventors: Farine, Pierre, Zellweger, Emil, Imfeld, Kilian, Oesch, Yves
• Granted Patent: US 7,321,754 B2
• Time in Patent Office: Days
• US Class Current: 455/260
• CPC Class Codes: H03D 3/007 by converting the oscillations into two quadrature related signals H03D3/245 takes precedence
• CPC Class Codes: H03D 7/163 the local oscillations of at least two of the frequency changers being derived from a single oscillator

Abstract

The radio-frequency signal frequency conversion device generates intermediate complex signals (IF) for a correlation stage of a low power RF receiver. In order to do this, the device includes a first selective pass-band filter for filtering radio-frequency signals picked up by an antenna. A frequency synthesiser generates first and second high frequency signals, wherein the frequency of the first signals is higher than the frequency of the second signals. This synthesiser receives reference signals from an oscillator unit. A first mixer unit mixes the radio-frequency signals with the first signals in order to generate frequency-converted signals. A second pass-band filter filters the signals from the first mixer unit, and provides signals to a second mixer unit to mix them with the second high frequency signals. Finally, shaping means for the signals provided by the second mixer unit generate the intermediate signals. The second filter is a not very selective active filter, which is integrated, in an RF/IF integrated circuit with the first and second mixer units, the signal shaping means, and certain parts of the synthesiser and the oscillator unit.

Claims

1-13. -13. (Cancelled)

14. A radio-frequency signal frequency conversion device for generating intermediate signals intended to be processed in a correlation stage of a low power RF receiver, the device including:

a first pass-band filter for filtering radio-frequency signals picked up by an antenna of the receiver, said first filter being a passive selective filter for eliminating the image frequencies during a first frequency conversion;

oscillating signal generating means for generating first and second high frequency signals, the frequency of the first signals being higher than the frequency of the second signals;

a first mixer unit for mixing the filtered radio-frequency signals with the first high frequency signals in order to generate signals whose frequency is equal to the result of a subtraction of the frequency of the first signals from a carrier frequency of the radio-frequency signals;

a second pass-band filter for filtering the signals originating from the first mixer unit;

a second mixer unit for mixing the signals filtered by the second filter with the second high frequency signals in order to generate signals whose frequency is equal to the result of a subtraction of the frequency of the second signals from the frequency of the signals originating from the first mixer unit; and

shaping means for the signals provided by the second mixer unit for generating the intermediate signals;

wherein the second filter is a not very selective filter.

15. The device according to claim 14, wherein the second filter is integrated in an RF/IF integrated circuit with the first and second mixer units, the signal shaping means, and certain parts of the oscillating signal generating means.

16. The device according to claim 14, wherein the second filter is an active filter in which the signals generated by the first mixer unit are filtered and amplified.

17. The device according to claim 14 for a low power GPS receiver, wherein the frequency of the signals generated by the first mixer unit is within a margin of 50 to 100 times less than a carrier frequency of the radio-frequency signals.

18. The device according to claim 14, wherein the frequency of the first high frequency signals is n times higher than the frequency of the second high frequency signals, n being an integer number selected from the range of 50 to 100.

19. The device according to claim 14, wherein the oscillating signal generating means include a reference oscillator unit and a frequency synthesiser connected to the reference oscillator unit, said synthesiser providing the first and second high frequency signals on the basis of reference signals provided by the reference oscillator unit.

20. The device according to claim 14, wherein the oscillating signal generating means include a reference oscillator unit and a frequency synthesiser connected to the reference oscillator unit, said synthesiser providing the first high frequency signals on the basis of reference signals provided by the reference oscillator unit and the reference oscillator unit providing the second high frequency signals.

21. The device according to claim 19, wherein all the frequency synthesiser elements, which includes a phase lock loop, are integrated in the RF/IF integrated circuit with the exception of a control signal filtering low-pass filter for a voltage controlled oscillator, the oscillator being intended to generate the first high frequency signals.

22. The device according to claim 14, wherein the second high frequency signals are formed of second in-phase signals and second quarter-phase signals, and wherein the second mixer unit includes a first mixer for mixing the signals originating from the first mixer unit with the second in-phase signals and a second mixer for mixing the signals originating from the first mixer unit with the second quarter-phase signals, the shaping means receiving the signals from the first and second mixers to provide intermediate complex signals formed of in-phase signals and quarter-phase signals.

23. The device according to claim 22, wherein the shaping means include, after each mixer of the second mixer unit, a low-pass filter followed by a controlled gain amplifier and an analogue/digital converter clocked by clock signals provided by the oscillator unit, one of the converters providing the in-phase signals of the sampled and quantified intermediate signals, and the other converter providing the quarter-phase signals of the sampled and quantified intermediate signals.

24. The device according to claim 19, wherein the oscillator unit provides reference signals whose frequency is determined by a quartz crystal, said frequency being preferably situated between 10 and 20 MHz, and wherein all the oscillator unit elements are integrated in the RF/IF integrated circuit with the exception of the quartz crystal.

25. An RF/IF integrated circuit for a device according to claim 14, wherein it includes the first mixer unit, the second pass-band filter, the second mixer unit, the shaping means and the majority of the oscillating signal generating means.

26. The RF/IF integrated circuit according to claim 25, wherein it is made in a semiconductor material, for example silicon, and in a CMOS technology of 0.25 μ

m or less.

27. The device according to claim 14 for a low power GPS receiver, wherein the frequency of the signals generated by the first mixer unit is 64 times less than a carrier frequency of the radio-frequency signals.

28. The device according to claim 14, wherein the frequency of the first high frequency signals is n times higher than the frequency of the second high frequency signals, n being an integer number equal to 64.

29. The device according to claim 14, wherein the second filter is an active pass-band filter in which the signals generated by the first mixer unit are filtered and amplified.