Direct-conversion receiver for a communication system using a modulation with non-constant envelope

• US 20030087625A1
• Filed: 10/25/2002
• Published: 05/08/2003
• Est. Priority Date: 10/26/2001
• Status: Active Grant

• Current Assignee: Microelectronic Innovations LLC
• Original Assignee: STMicroelectronics NV
• Inventors: Conti, Patrick
• Granted Patent: US 7,095,997 B2
• Time in Patent Office: Days
• US Class Current: 455/323
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22
• CPC Class Codes: H04L 25/062 Setting decision thresholds using feedforward techniques only
• CPC Class Codes: H04L 27/22 Demodulator circuits; Receiver circuits

Abstract

A direct-conversion receiver includes an analog stage for receiving an incident signal from a transmission channel, mixers and programmable-gain amplifiers. The receiver further includes at least one compensation module having input and output terminals respectively connected between the output of the mixers and the input of the programmable-gain amplifiers. The compensation module compensates for both a static DC voltage offset and a possible dynamic DC voltage offset of the analog stage.

Claims

1. Direct-conversion receiver for a communication system using modulation with non-constant envelope, comprising an analog stage for receiving an incident signal of a transmission channel and comprising transposition means (Mx) and programmable-gain amplification means (PGA), characterized in that it furthermore comprises at least one compensation module (MDM, STR) possessing an input terminal (BE) and an output terminal (STR) which are connected between the output of the transposition means (Mx) and the input of the amplification means (PGA), and which is able to compensate both for a static DC voltage offset and a possible dynamic DC voltage offset of the analog stage.

2. Receiver according to claim 1, characterized in that the compensation module comprises

first means (MPF, PD1) able to determine the envelope of the AC component of the signal present at the input terminal of the module,

second means (PD2) able to determine the envelope of the signal present at the input terminal of the module,

first subtraction means (CMP) connected to the output of the first means and to the output of the second means,

a sample-and-hold facility (SAH) connected to the output of the first subtraction means, and

second subtraction means (STR) forming the output terminal of the module, and possessing a first input connected to the transposition means, and a second input connected to the output of the sample-and-hold facility.

3. Receiver according to claim 2, characterized in that the first means comprise a high-pass filter (HPF) whose cut-off frequency lies between a quarter of the frequency of the modulation and a half of the frequency of the modulation.

4. Receiver according to one of the preceding claims, characterized in that the analog stage furthermore comprises low-pass filtering means (LPF) situated downstream of the transposition means, and in that the input terminal (BE) of the compensation module is connected downstream of the low-pass filtering means.

5. Receiver according to one of the preceding claims, characterized in that the analog stage comprises two processing pathways (I, Q) processing quadrature signals, and in that the receiver comprises a single compensation module whose input terminal is connected to one of the processing pathways and whose output terminal is connected to each of the processing pathways.

6. Remote terminal of a communication system using modulation with non-constant envelope, characterized in that it comprises a receiver according to one of claims 1 to 5.

7. Terminal according to claim 6, characterized in that it forms a cellular mobile telephone.

8. Method of processing an incident signal within a direct-conversion receiver for a communication system using modulation with non-constant envelope, comprising a reception of the incident signal of a transmission channel, a frequency transposition and a programmable-gain amplification, characterized in that a compensation signal (SCP) representative of a static DC voltage offset and a possible dynamic DC voltage offset of the analog stage is furthermore formulated from a signal tapped off after transposition, and this compensation signal is subtracted before amplification from the signal emanating from the transposed signal.

9. Method according to claim 8, characterized in that the formulation of the compensation signal (SCP) comprises

a determination of the envelope of the AC component of the signal tapped off,

a determination of the envelope of the signal tapped off,

a subtraction between the two envelopes,

a sampling-and-holding of the subtracted signal.

10. Method according to claim 9, characterized in that the determination of the envelope of the AC component of the signal tapped off comprises a high-pass filtering whose cut-off frequency lies between a quarter of the frequency of the modulation and a half of the frequency of the modulation.

11. Method according to one of claims 8 to 10, characterized in that it furthermore comprises a low-pass filtering after transposition, and in that the compensation signal is formulated from the signal tapped off after this low-pass filtering.

12. Method according to one of claims 8 to 11, in which the analog stage of the receiver comprises two processing pathways processing quadrature signals, characterized in that the compensation signal is formulated from a signal tapped off from one of the processing pathways, and it is delivered to both processing pathways.