Receiver filtering devices, systems, and methods

• US 8,781,430 B2
• Filed: 06/29/2009
• Issued: 07/15/2014
• Est. Priority Date: 06/29/2009
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Fagg, Russell J.
• Primary Examiner(s): Pham, Tuan
• Application Number:
  US12/494,109
• Publication Number:
  US 20100327965A1
• Time in Patent Office: 1,842 Days
• Field of Search: 455/424, 455/425, 455/456.5, 455/561, 455/550.1, 455/303, 455/501, 455/63.1, 455/412.1, 455/67.13, 455/278.1, 455/286, 455/339, 455/307, 455/306, 455/296, 375/350, 375/316, 375/346, 708/300, 708/301, 708/314, 700/94, 330/284, 330/305, 330/9, 341/150, 341/155, 327/355, 327/552, 327/352
• US Class Current: 455/307
• CPC Class Codes: H03H 15/00 Transversal filters electromechanical filters H03H9/46, H03H9/70

Abstract

Exemplary embodiments of the invention disclose receiver baseband filtering. In an exemplary embodiment, the filter device may comprise a continuous-time filter and a discrete-time filter operably coupled to the continuous time-filter. The discrete-time filter may include a passive infinite impulse response filter operably coupled between the continuous-time filter and an amplifier. The discrete-time filter may also include an active infinite impulse response filter operably coupled between an output of the amplifier and an input of the amplifier. The discrete-time filter may be configured to combine an output of the active infinite impulse response filter and an output of the passive infinite impulse response filter to form a composite signal. Furthermore, the amplifier may be configured to receive and amplify the composite signal.

Claims

1. A filter device, comprising:

a continuous-time filter; and

a discrete-time filter operably coupled to the continuous-time filter, the discrete-time filter comprising;

a passive infinite impulse response filter operably coupled to the continuous-time filter;

an amplifier operably coupled to the passive infinite impulse response filter and configured to receive and amplify a composite signal; and

an active infinite impulse response filter operably coupled between an output of the amplifier and an input of the amplifier;

wherein the discrete-time filter is configured to combine an output of the active infinite impulse response filter and an output of the passive infinite impulse response filter to produce the composite signal, wherein the active infinite impulse response filter is configured to generate from an amplified composite signal a frequency response having a gain at frequencies in a passband of a received signal.

2. The filter device of claim 1, further comprising a decimating finite impulse response filter operably coupled between the passive infinite impulse response filter and the amplifier and configured to reduce a sampling rate of a signal received from the passive infinite impulse response filter.

3. The filter device of claim 2, the decimating finite impulse response filter is reduces the sampling rate of the signal received from the passive infinite impulse response filter from 640 Ms/s to 160 Ms/s.

4. The filter device of claim 1, further comprising a voltage doubler operably coupled between the continuous-time filter and the passive infinite impulse response filter and to sample a differential input voltage signal and output a differential voltage signal having a voltage substantially twice the amount of the sampled differential input voltage.

5. The filter device of claim 1, wherein the continuous-time filter comprises a transimpedance amplifier operably coupled to a RC pole generator.

6. The filter device of claim 5, wherein the RC pole generator generates two RC poles.

7. The filter device of claim 5, wherein a capacitance at an output of the transimpedance amplifier generates a pole at 12.5 MHz for a received signal having a bandwidth of 10 MHz at baseband.

8. The filter device of claim 1, wherein the passive infinite impulse response filter generates a pole within the passband of the received signal.

9. The filter device of claim 1, wherein the discrete-time filter combines an output of the active infinite impulse response filter and an output of the passive infinite impulse response filter by coupling the output of the active infinite impulse response filter and the output of the passive infinite impulse response filter in parallel.

10. The filter device of claim 2, wherein the transfer function of the active infinite impulse response filter is defined by:

H(s)=b/(1+aZ<sup>−

n</sup>);

wherein “

a”

is the ratio of the value of the capacitors within active infinite impulse response filter to the value of the capacitors within the decimating finite response filter, “

z”

is a unit delay operator, “

b”

is a gain of the amplifier, and “

n”

is the number of samples delayed.

11. The filter device of claim 1, wherein the passive infinite impulse response filter is configured to generate a frequency response that attenuates in a passband of a received signal.

12. The filter device of claim 1, wherein the amplifier comprises a switched capacitor amplifier.

13. A method of filtering a signal, comprising:

transmitting a signal through a continuous-time filter;

transmitting the signal through a passive infinite impulse response filter and outputting a filtered signal;

amplifying the filtered signal with an amplifier;

transmitting the amplified signal through an active infinite impulse response filter coupled between an output of the amplifier and an input of the amplifier;

combining the filtered signal with a signal output from the active infinite impulse response filter to create a composite signal; and

amplifying the composite signal, wherein the active infinite impulse response filter is configured to generate from an amplified composite signal a frequency response having a gain at frequencies in a passband of a received signal.

14. The method of claim 13, further comprising substantially doubling a voltage of the signal after transmitting the signal through the continuous-time filter.

15. The method of claim 13, wherein combining the filtered signal with a signal output from the active infinite impulse response filter to create a composite signal at least partially compensates for at least some passband loss due to transmission of the signal through the passive infinite impulse response filter.

16. The method of claim 13, wherein combining the filtered signal with the signal output from the active infinite impulse response filter comprises coupling the filtering signal in parallel with the signal output from the active infinite impulse response filter.

17. The method of claim 13, further comprising reducing a sampling rate of the filtered signal prior to amplifying the filtered signal.

18. A device that facilitates receiver baseband filtering, comprising:

means for transmitting a signal through a continuous-time filter;

means for transmitting the signal through a passive infinite impulse response filter and outputting a filtered signal;

means for amplifying the filtered signal with an amplifier;

means for transmitting the amplified signal through an active infinite impulse response filter coupled between an output of the amplifier and an input of the amplifier;

means for combining the filtered signal with a signal output from the active infinite impulse response filter to create a composite signal; and

means for amplifying the composite signal, wherein the active infinite impulse response filter is configured to generate from an amplified composite signal a frequency response having a gain at frequencies in a passband of a received signal.

19. A method of filtering a signal, comprising:

filtering a signal with a passive infinite impulse response filter;

filtering the signal with an active infinite impulse response filter;

combining an output of the passive infinite impulse response filter with an output of the active infinite impulse response filter to produce a composite signal; and

amplifying the composite signal, wherein the active infinite impulse response filter is configured to generate from an amplified composite signal a frequency response having a gain at frequencies in a passband of a received signal.

20. The method of claim 19, wherein combining comprises connecting the output of the passive infinite impulse response filter and the output of the active infinite impulse response filter in parallel to produce the composite signal.

21. The method of claim 19, wherein filtering a signal with a passive infinite impulse response filter comprises positioning a pole within the passband of the signal.

22. A device that facilitates receiver baseband filtering, comprising:

means for filtering a signal with a passive infinite impulse response filter;

means for filtering the signal with an active infinite impulse response filter;

means for combining an output of the passive infinite impulse response filter with an output of the active infinite impulse response filter to produce a composite signal; and

means for amplifying the composite signal, wherein the active infinite impulse response filter is configured to generate from an amplified composite signal a frequency response having a gain at frequencies in a passband of a received signal.

23. A discrete-time filter, comprising:

a passive infinite impulse response filter configured to generate a pole within a passband of a received signal;

a switched capacitor amplifier having an input operably coupled to an output of the passive infinite impulse response filter; and

a feedback loop operably coupled between an output of the amplifier and the input of the amplifier and comprising an active infinite impulse response filter, wherein the discrete-time filter is configured to combine the output of the passive infinite impulse response filter and an output of the active infinite impulse response filter, wherein the active infinite impulse response filter is configured to generate from an amplified composite signal a frequency response having a gain at frequencies in a passband of a received signal.

24. The discrete-time filter of claim 23, further comprising a decimating finite impulse response filter operably coupled between the passive infinite impulse response filter and the amplifier.

25. The discrete-time filter of claim 23, further comprising a voltage doubler having an output operably coupled to the passive infinite impulse response filter.

26. The discrete-time filter of claim 23, wherein the active infinite impulse response filter is configured to sample an input signal with an array of capacitors, initiate a delay of a number of samples, and convey an output signal.

27. A receiver filtering system, comprising:

a front-end receiver including an antenna, a low-noise amplifier, and a mixer; and

a filter device coupled to the front-end receiver, the filter device comprising;

a discrete-time filter operably coupled to a continuous-time filter, wherein the discrete-time filter comprises;

a passive infinite impulse response filter operably coupled between an output of the continuous-time filter and an input of a switched capacitor amplifier; and

an active infinite impulse response filter having an input operably coupled to an output of the switched capacitor amplifier and an output operably coupled to an input of the switched capacitor amplifier;

wherein the discrete-time filter is configured to form a composite signal from the output of the active infinite impulse response filter and the output of the passive infinite impulse response filter, wherein the active infinite impulse response filter is configured to generate from an amplified composite signal a frequency response having a gain at frequencies in a passband of a received signal.

28. The receiver filtering system of claim 27, wherein the front-end receiver comprises one of a continuous-time front-end receiver and a discrete-time front-end receiver.

29. The receiver filtering system of claim 27, wherein the continuous-time filter is configured to receive a differential signal from the front-end receiver and provide alias filtering before transmitting the differential signal to the discrete-time filter.

30. A non-transitory computer-readable medium comprising program codes for causing a processor to:

filter a signal with a passive infinite impulse response filter;

filter the signal with an active infinite impulse response filter; and

combine an output of the passive infinite impulse response filter with an output of the active infinite impulse response filter to produce a composite signal, wherein the active infinite impulse response filter is configured to generate from an amplified composite signal a frequency response having a gain at frequencies in a passband of a received signal.

31. The non-transitory computer-readable medium of claim 30, wherein the codes for causing the processor to combine an output of the passive infinite impulse response filter with an output of the active infinite impulse response filter further cause the processor to:

connect the output of the passive infinite impulse response filter and the output of the active infinite impulse response filter in parallel to produce the composite signal.

32. The non-transitory computer-readable medium of claim 30, wherein the codes for causing the processor to filter a signal with a passive infinite impulse response filter further cause the processor to:

position a pole within the passband of the signal.