System and method for receiving a multiple format wireless signal

• US 7,693,191 B2
• Filed: 03/26/2007
• Issued: 04/06/2010
• Est. Priority Date: 03/26/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: McLaughlin, Kevin, Rahman, Mahibur, Gorday, Robert Mark, Ivonnet, Jorge
• Primary Examiner(s): Ngo; Ricky
• Assistant Examiner(s): Gidado; Rasheed
• Application Number:
  US11/691,301
• Publication Number:
  US 20080240166A1
• Time in Patent Office: 1,107 Days
• Field of Search: 370/509, 370/514, 375/131, 375/140, 375/130, 375/141
• US Class Current: 370/515
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04L 1/0027 Scheduling of signalling, e.g. occurrence thereof
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453
• CPC Class Codes: H04L 27/0012 arrangements for identifying the type of modulation

Abstract

An apparatus (200) and method (300) for receiving a communications signal. A spread spectrum signal demodulator (210) is adapted to demodulate a packet header (110) of a data packet (102) that is communicated by a wireless communications signal. The packet header (110) is modulated with a spread spectrum technique and the spread spectrum signal demodulator (210) produces a packet header detection signal (220) representing a successful detection of a predefined packet header value. A non-spread spectrum signal demodulator (212) is communicatively coupled to the spread spectrum signal demodulator (210) and demodulates, in response to the packet header detection signal (220), a non-spread spectrum modulated data payload within the data packet. A data output select (234) produces demodulated data produced by either one or both the spread spectrum signal demodulator (210) and the non-spread spectrum signal demodulator (212).

Claims

1. A communications signal receiver, comprising:

a spread spectrum signal demodulator for demodulating a packet header of a data packet communicated by a wireless communications signal, the packet header being modulated with a spread spectrum technique, the spread spectrum signal demodulator producing a packet header detection signal representing a successful detection of a predefined packet header value;

a non-spread spectrum signal demodulator, communicatively coupled to the spread spectrum signal demodulator, the non-spread spectrum signal demodulator for demodulating, in response to the packet header detection signal, a non-spread spectrum modulated data payload within the data packet; and

a data output selector for selecting demodulated data produced by either one or both the spread spectrum signal demodulator and the non-spread spectrum signal demodulator.

2. The communications signal receiver of claim 1,

wherein the spread spectrum demodulator further produces a frequency correction signal indicating a received frequency offset for the wireless communications signal, and

wherein the non-spread spectrum signal demodulator receives the frequency correction signal and adjusts a communications signal frequency offset based upon the frequency correction signal.

3. The communications signal receiver of claim 1,

wherein the spread spectrum demodulator further produces a channel symbol time synchronization signal indicating a chip transition time for the wireless communications signal, and

wherein the non-spread spectrum signal demodulator receives the chip transition time synchronization signal and synchronizes demodulation of the non-spread spectrum modulated data payload based upon the chip transition time synchronization signal.

4. The communications signal receiver of claim 3, wherein the channel symbol time synchronization signal comprises a first payload bit synchronization signal indicating a start of a bit transition for a first bit within the non-spread spectrum modulated data payload.

5. The communications signal receiver of claim 1, wherein the non-spread spectrum signal demodulator further comprises a complex signal correction stage for applying complex magnitude and phase corrections to the wireless communications signal prior to demodulation by the non-spread spectrum signal demodulator.

6. The communications signal receiver of claim 1,

wherein the data packet comprises a data frame structure,

wherein the spread spectrum signal demodulator produces a frame synchronization signal indicating a start of a data frame within the data frame structure, and

wherein the non-spread spectrum signal demodulator receives the frame synchronization signal and produces the demodulated data based upon the frame synchronization signal.

7. The communications signal receiver of claim 1,

wherein the non-spread spectrum signal demodulator further performs a second packet header value detection by correlating a start of frame delimiter portion of the packet header with the predefined packet header value, and

wherein the non-spread spectrum signal demodulator demodulates in response to the second packet header value detection.

8. The communications signal receiver of claim 1, further comprising:

a radio frequency signal processor, communicatively coupled to the spread spectrum signal demodulator and the non-spread spectrum signal demodulator, for producing a complex value baseband signal representing the wireless communications signal, the radio frequency signal processor having a phase noise characteristic, and

wherein the non-spread spectrum signal demodulator comprises at least one of a frequency modulation discriminator and a differential phase detector, the at least one of the frequency modulation discriminator and the differential phase detector having a high pass frequency response for phase noise sensitivity that compensates for the phase noise characteristic.

9. The communications signal receiver of claim 8, wherein the non-spread spectrum signal demodulator further comprises a complex signal correction stage for applying complex magnitude and phase corrections to the wireless communications signal prior to demodulation by the non-spread spectrum signal demodulator, and wherein the complex magnitude and phase corrections are individually applied to each communications signal receiver unit.

10. The communications signal receiver of claim 1,

wherein the wireless communications signal comprises a packet header corresponding to a packet header format defined pursuant to IEEE 802.15.4,

wherein the predefined packet header value comprises one of a start of frame delimiter value defined pursuant to IEEE 802.15.4 which indicates that the data packet conforms to a format defined pursuant to IEEE 802.15.4, and a start of frame delimiter value not defined by IEEE 802.15.4 which indicates that the data payload comprises a payload data length portion and a data payload portion and that the data payload is modulated with a non-spread spectrum technique, and

wherein the spread spectrum signal demodulator demodulates, in response to detecting the start of frame delimiter defined by IEEE 802.15.4, the data payload.

11. The communications signal receiver of claim 10, wherein the payload data length portion that is modulated with a non-spread spectrum technique has a larger number of bits than a payload data length portion conforming to the format defined pursuant to IEEE 802.15.4.

12. A method for receiving a wireless data packet, the method comprising:

demodulating, in a communications receiver, a packet header of a data packet communicated by a wireless communications signal, the packet header being modulated with a spread spectrum technique;

producing, in response to the demodulating, a packet header detection signal representing a successful detection of a predefined packet header value;

demodulating, in response to the producing, a non-spread spectrum modulated data payload within the data packet; and

producing, in response to demodulating the non-spread spectrum modulated data payload, demodulated data contained within the non-spread spectrum modulated data payload.

13. The method of claim 12, further comprising:

producing, in response to the demodulating the packet header, a frequency correction signal indicating a received frequency offset for the wireless communications signal, and wherein the demodulating the non-spread spectrum modulated data payload adjusts a communications signal frequency offset based upon the frequency correction signal.

14. The method of claim 12, further comprising:

producing, in response to demodulating the packet header, a channel symbol time synchronization signal indicating a chip transition time for the communications signal, and

wherein the demodulating the non-spread spectrum modulated data payload synchronizes demodulation of the non-spread spectrum modulated data payload based upon the chip transition time synchronization signal.

15. The method of claim 12, further comprising applying, prior to the demodulating the non-spread spectrum modulated data payload, a complex magnitude and phase corrections to the wireless communications signal.

16. The method of claim 12, wherein the data packet comprises a data frame structure, the method further comprising:

producing, in response to demodulating the packet header, a frame synchronization signal indicating a start of a data frame within the data frame structure, and

wherein the producing demodulated data is based upon the frame synchronization signal.

17. The method of claim 12,

wherein the wireless communications signal is represented by a complex value baseband signal received from a radio frequency signal processor, the radio frequency signal processor having a phase noise characteristic, and

wherein the demodulating the non-spread spectrum modulated signal further comprises detecting channel symbols with at least one of a frequency modulation discriminator and a differential phase detector, wherein the at least one of the frequency modulation discriminator and the differential phase detector have a high pass frequency response for phase noise sensitivity that compensates for the phase noise characteristic.

18. The method of claim 12,

wherein the predefined packet header value comprises one of

a start of frame delimiter value defined pursuant to IEEE 802.15.4 which indicates that the data packet conforms to a format defined pursuant to IEEE 802.15.4, and

a start of frame delimiter value not defined by IEEE 802.15.4 which indicates that a payload data length portion and a data payload portion of the data packet are the non-spread spectrum modulated data payload that are modulated with a non-spread spectrum technique.

19. The method of claim 18, wherein the data payload length portion and the data payload portion of the data packet that are modulated with a non-spread spectrum technique are modulated in a phase coherent, offset quadrature phase shift keying technique defined for spreading chips pursuant to IEEE 802.15.4.

20. An IEEE 802.15.4 receiver processing circuit, comprising:

a spread spectrum signal demodulator for demodulating a packet header of a data packet communicated through a wireless communications signal,

the packet header being modulated with a spread spectrum technique and corresponding to a packet header format defined pursuant to IEEE 802.15.4,

the spread spectrum signal demodulator producing at least a packet header detection signal representing a successful detection of one of two predefined packet header values that comprise a start of frame delimiter value defined pursuant to IEEE 802.15.4 and a start of frame delimiter value not defined by IEEE 802.15.4;

a non-spread spectrum signal demodulator, communicatively coupled to the spread spectrum signal demodulator, the non-spread spectrum signal demodulator for demodulating, in response to the successful detection of the predefined packet header value comprising the start of frame delimiter value not defined by IEEE 802.15.4, a non-spread spectrum modulated data payload encoded onto the wireless communications signal as part of the data packet; and

a data output selector for selecting demodulated data produced by either one of both the spread spectrum signal demodulator and the non-spread spectrum signal demodulator.