Code division multiple access transmitter and receiver

• US 6,327,257 B1
• Filed: 04/26/1999
• Issued: 12/04/2001
• Est. Priority Date: 04/30/1998
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Khalifa, Nabil
• Primary Examiner(s): CORRIELUS, JEAN B
• Application Number:
  US09/299,527
• Time in Patent Office: 953 Days
• Field of Search: 370/204, 370/335, 370/342, 370/441, 370/479, 370/206, 370/208, 370/209, 375/130, 375/131, 375/132, 375/133, 375/135, 375/136, 375/138, 375/140, 375/141, 375/142, 375/146, 375/147, 375/150, 375/367
• US Class Current: 370/342
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/709 Correlator structure

Abstract

The input data to a CDMA transmitter is used to introduce a slight frequency offset to the clock that is used to generate the CDMA code. At the receiver, the frequency-offset CDMA signal proportionately affects the magnitude of output signals from one or more CDMA correlators. A composite signal that is based on the magnitudes of the output signals is compared to a set of predefined threshold levels to provide the demodulated output data.

Claims

1. A code division multiple access transmitter comprising

a modulation stage followed by an up-converter,

characterized in that

the modulation stage comprises in series at least a data-to-frequency offset converter, a frequency synthesizer controlled by the data to frequency offset converter and a code generator, and

the code generator is periodically initialized by an initialization module by means of which at least one code period without any frequency offset is provided each P code periods.

2. A code division multiple access transmitter according to claim 1, wherein, in the modulation stage, multi-code with different frequency offsets is used.

3. A code division multiple access receiver comprising

a down converter followed by a demodulation stage,

characterized in that

the demodulation stage receives a modulated signal that has been modulated by a modulation stage, comprising at least a data-to-frequency offset converter, a frequency synthesizer controlled by said converter and a code generator, and

the demodulation stage comprises a demodulation branch and calibration branch,

the demodulation branch comprises

one or more correlators that are configured to detect frequency offsets in the modulated signal, and

a decoder that is configured to provide corresponding demodulated data based on the detected frequency offsets, and

the calibration branch is configured to provide a periodic frequency control to a reference code generator of the receiver before data demodulation.

4. A code division multiple access receiver according to claim 3, characterized in that, for frequency offsets f_m and 2f_m in the modulated signal, demodulated data are obtained according to a corresponding phase and amplitude of output signals of the one or more correlators.