Direct conversion radio receiver using combined down-converting and energy spreading mixing signal

• US 6,445,726 B1
• Filed: 04/30/1999
• Issued: 09/03/2002
• Est. Priority Date: 04/30/1999
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Gharpurey, Ranjit
• Primary Examiner(s): Corrielus, Jean
• Assistant Examiner(s): Bayard, Emmanuel
• Application Number:
  US09/302,604
• Time in Patent Office: 1,222 Days
• Field of Search: 375/316, 375/319, 375/324, 375/326, 375/338, 375/340, 375/137, 375/214, 455/131, 455/189.1, 455/207, 455/209, 455/314, 455/313, 455/311, 455/323, 455/304, 455/324, 455/236.1, 329/346, 329/304, 329/306, 329/323, 329/324
• US Class Current: 375/136
• CPC Class Codes: H03D 1/00 Demodulation of amplitude-modulated oscillations H03D5/00, H03D9/00, H03D11/00 take precedence
• CPC Class Codes: H03D 2200/0047 Offset of DC voltage or frequency
• CPC Class Codes: H03D 3/001 Details of arrangements applicable to more than one type of frequency demodulator H03D3/28 takes precedence
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22
• CPC Class Codes: H04B 1/69 Spread spectrum techniques

Abstract

A receiver (54) comprising an input for receiving an RF signal (FIG. 7) centered at a first frequency and having a bandwidth. The receiver also comprises a first mixer (62) for producing a first output signal. The first output signal results from mixing the RF signal with a signal having an energy spreading portion (p(t)) and a down-converting portion (c(t)). Moreover, this first output signal comprises a self-mixing DC signal (c(t)p(t) self-mixing DC component) and a down-converted and energy spread RF signal (FIG. 11). The receiver further comprises a second mixer (70) for producing a second output signal by mixing a signal responsive to the first output signal with the energy spreading portion of the signal. The second output signal comprises two signals, namely: (1) a baseband signal (down-converted RFA₁) responsive to the down-converted and energy spread RF signal; and (2) a portion of the spread DC signal (spread DC).

Claims

1. A receiver, comprising:

an input for receiving an RF signal centered at a first frequency and having a bandwidth;

a first mixer for producing a first output signal by mixing the RF signal with a signal having an energy spreading portion and a down-converting portion, wherein the first output signal comprises a self-mixing DC signal and a down-converted and energy spread RF signal; and

a second mixer for producing a second output signal by mixing a signal responsive to the first output signal with the energy spreading portion of the signal, such that the second output signal comprises;

a baseband signal responsive to the down-converted; and

an energy spread RF signal and a spread DC signal responsive to the self-mixing DC signal.

2. The receiver of claim 1 and further comprising an amplifier, wherein the RF signal is output by the amplifier to the input and represents an amplified signal corresponding to a lower amplitude input RF signal that is input to the amplifier.

3. The receiver of claim 2 and further comprising an antenna for receiving a radio signal and in response for providing the lower amplitude input RF signal in response to the radio signal.

4. The receiver of claim 2 and further comprising a first low pass filter coupled to the output of the second mixer, wherein the first low pass filter is for producing an output which comprises only a portion of the spread DC signal.

5. The receiver of claim 4 wherein each of the amplifier, first mixer, first low pass filter, and second mixer are formed using a single integrated circuit.

6. The receiver of claim 1 wherein the energy spreading portion of the signal has a frequency greater than or equal to the bandwidth.

7. The receiver of claim 6 wherein the down-converting portion of the signal has a frequency approximately equal to the first frequency.

8. The receiver of claim 1 wherein the energy spreading portion of the signal comprises a square wave.

9. The receiver of claim 1 wherein the energy spreading portion of the signal comprises a signal having an amplitude change between a value of +M and a value of −

M.

10. The receiver of claim 9 wherein the signal having an amplitude change between a value of +M and a value of −

M switches randomly from a first frequency to a second frequency, wherein each of the first frequency and the second frequency is greater than or equal to the bandwidth.

11. The receiver of claim 9:

wherein the signal having an amplitude change between a value of +M and a value of −

M switches randomly with respect to each transition time relative to a preceding transition; and

wherein each transition is such that the energy spreading portion of the signal is at substantially a frequency greater than or equal to the bandwidth.

12. The receiver of claim 1 wherein the baseband signal has a magnitude approximately equal to the RF signal.

13. The receiver of claim 1 and further comprising:

an amplifier, wherein the RF signal is output by the amplifier to the input and represents an amplified signal corresponding to a lower amplitude input RF signal that is input to the amplifier;

a first low pass filter coupled to the output of the second mixer, wherein the first low pass filter is for producing an output which comprises only a portion of the spread DC signal;

wherein each of the amplifier, first mixer, first low pass filter, and second mixer are formed using a single integrated circuit; and

wherein the energy spreading portion of the signal has a frequency approximately equal to the bandwidth.

14. The receiver of claim 13 wherein the down-converting portion of the signal has a frequency approximately equal to the first frequency.

15. The receiver of claim 1 wherein the RF signal comprises a cellular telephone RF signal.

16. The receiver of claim 1 wherein the RF signal comprises a slot selected among a plurality of slots in a channel.

17. The receiver of claim 1 wherein the first output signal is connected directly to an input of the second mixer.

20. The method of claim 17 wherein the energy spreading portion of the signal has a frequency approximately equal to the bandwidth.

21. The method of claim 20 wherein the down-converting portion of the signal has a frequency approximately equal to the first frequency.

18. A method of signal processing, comprising:

receiving an RF signal centered at a first frequency and having a bandwidth;

forming a first output signal by mixing the RF signal with a signal having an energy spreading portion and a down-converting portion, wherein the formed first output signal comprises a self-mixing DC signal and a down-converted and energy spread RF signal; and

forming a second output signal by mixing a signal responsive to the first output signal with the energy spreading portion of the signal, such that the second output signal comprises;

a signal responsive to the down-converted and energy spread RF signal; and

a spread DC signal responsive to the self-mixing DC signal.

19. The method of claim 18 wherein the signal responsive to the down-converted and energy spread RF signal comprises a baseband signal having a magnitude approximately equal to the RF signal.

22. The method of claim 18 wherein the energy spreading portion of the signal comprises a square wave.

23. The method of claim 18 wherein the energy spreading portion of the signal comprises a signal having a random amplitude change between a value of +M and a value of −

M.

24. The method of claim 23 wherein the signal having an amplitude change between a value of +M and a value of −

M switches randomly from a first frequency to a second frequency, wherein each of the first frequency and the second frequency is greater than or equal to the bandwidth.

25. The method of claim 23:

wherein the signal having an amplitude change between a value of +M and a value of −

M switches between the value of +M and the value of −

M at random transition times; and

wherein each transition time is such that the energy spreading portion of the signal is at substantially a frequency greater than or equal to the bandwidth.