Radio transmitter incorporating digital modulator and circuitry to accommodate baseband processor with analog interface

Abstract: A circuit provides a digital signal at optimal times to a digital processor of a transmitter. The circuit includes a complex analog-to-digital converter (ADC), a demodulator and a timing recovery circuit. The complex ADC is connected to receive an analog complex modulated baseband signal and to convert the analog complex modulated baseband signal to a digital complex modulated baseband signal. The demodulator operates to demodulate the digital signal to produce a demodulated digital signal for input to the digital processor. The timing recovery circuit receives a control signal and activates the digital processor based on a fixed timing relationship between receipt of the control signal at the timing recovery circuit and receipt of the analog complex modulated baseband signal at the complex ADC. (end of abstract)

Radio transmitter incorporating digital modulator and circuitry to accommodate baseband processor with analog interface description/claims

Brief Patent Description

Full Patent Description

Patent Application Claims

CROSS-REFERENCE TO RELATED APPLICATIONS

The present U.S. Utility patent application claims priority pursuant to 35 U.S.C. § 120, as a divisional, to U.S. Utility patent application Ser. No. 10/992,570, entitled “Radio Transmitter Incorporating Digital Modulator and Circuitry to Accommodate Baseband Processor with Analog Interface,” (Attorney Docket No. BP4079), filed Nov. 18, 2004 pending, which is hereby incorporated herein by reference in its entirety and made part of the present U.S. Utility patent application for all purposes:

BACKGROUND

1. Technical Field

The present invention relates to wireless communications and, more particularly, wideband wireless communication systems.

2. Related Art

Communication systems are known to support wireless and wire lined communications between wireless and/or wire lined communication devices. Such communication systems range from national and/or international cellular telephone systems to the Internet to point-to-point in-home wireless networks. Each type of communication system is constructed, and hence operates, in accordance with one or more communication standards. For instance, wireless communication systems may operate in accordance with one or more standards, including, but not limited to, IEEE 802.11, Bluetooth, advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), multi-channel-multi-point distribution systems (MMDS), and/or variations thereof.

Depending on the type of wireless communication system, a wireless communication device, such as a cellular telephone, two-way radio, personal digital assistant (PDA), personal computer (PC), laptop computer, home entertainment equipment, etc., communicates directly or indirectly with other wireless communication devices. For direct communications (also known as point-to-point communications), the participating wireless communication devices tune their receivers and transmitters to the same channel or channels (e.g., one of a plurality of radio frequency (RF) carriers of the wireless communication system) and communicate over that channel(s). For indirect wireless communications, each wireless communication device communicates directly with an associated base station (e.g., for cellular services) and/or an associated access point (e.g., for an in-home or in-building wireless network) via an assigned channel. To complete a communication connection between the wireless communication devices, the associated base stations and/or associated access points communicate with each other directly, via a system controller, via a public switch telephone network (PSTN), via the Internet, and/or via some other wide area network.

Each wireless communication device includes a built-in radio transceiver (i.e., receiver and transmitter) or is coupled to an associated radio transceiver (e.g., a station for in-home and/or in-building wireless communication networks, RF modem, etc.). As is known, the transmitter includes a data modulation stage, one or more intermediate frequency stages, and a power amplifier stage. The data modulation stage converts raw data into baseband signals in accordance with the particular wireless communication standard. The one or more intermediate frequency stages mix the baseband signals with one or more local oscillations to produce RF signals. The power amplifier stage amplifies the RF signals prior to transmission via an antenna.

Typically, the data modulation stage is implemented on a baseband processor chip, while the intermediate frequency (IF) stages and power amplifier stage are implemented on a separate radio processor chip. Historically, radio integrated circuits have been designed using bi-polar circuitry, allowing for large signal swings and linear transmitter component behavior. Therefore, many legacy baseband processors employ analog interfaces that communicate analog signals to and from the radio processor.

However, with the emergence of low-power, low-voltage CMOS radio processors, imperfections in the CMOS analog transmitter circuitry have required the addition of one or more digital signal pre-processing stages to mitigate the effects of such analog imperfections. The digital signal processing required is usually specific to the particular analog radio transmitter architecture, and therefore, is best implemented as part of the radio processor chip. Since the analog signals output from the baseband processor, which typically include modulated in-phase and quadrature phase components at zero IF, are not well suited for interfacing with a digital processing stage, the optimal baseband processor interface to a CMOS radio processor with substantial digital processing is an all-digital interface. However, until next-generation baseband processors are designed with digital interfaces to the radio processor, digital CMOS radio processors must be able to accommodate analog interfaces.

SUMMARY OF THE INVENTION

The present invention is directed to apparatus and methods of operation that are further described in the following Brief Description of the Drawings, the Detailed Description of the Invention, and the claims. Other features and advantages of the present invention will become apparent from the following detailed description of the invention made with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention can be obtained when the following detailed description of the preferred embodiment is considered with the following drawings, in which:

FIG. 1 is a functional block diagram illustrating a communication system that includes a plurality of base stations or access points (APs), a plurality of wireless communication devices and a network hardware component;

FIG. 2 is a schematic block diagram illustrating a radio frequency (RF) transmitter architecture including a baseband processor and a radio processor according to one embodiment of the present invention;

FIG. 3 is a circuit schematic illustrating various components of a radio processor according to one embodiment of the present invention;

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