WO2002027953A1

WO2002027953A1 - Baseband front-end for multi standard receiver

Info

Publication number: WO2002027953A1
Application number: PCT/SE2001/002114
Authority: WO
Inventors: Håkan OLSSON; Xiaopeng Li
Original assignee: Spirea Ab
Priority date: 2000-09-29
Filing date: 2001-09-28
Publication date: 2002-04-04
Also published as: AU2001292490A1; SE0003520L; SE0003520D0

Abstract

The invention relates to a multi-standard receiver adopted to a plurality of wireless communication standards and comprising: receiving means; TDD switch means and a plurality of bandpass filter; a plurality of LNA means; mixer means; baseband analog processing means; analog-to-digital converter means, comprising a sigma-delta modulator, said converter means being hardware reconfigurable for different sampling frequency and different quantizing in dependence of different standard baseband signals; and a programmable decimation filter being programmable into different standard filtering modes for filtering different standard digital signals received from said analog-to-digital converter means, and comprising filter means being used in at least two different standard modes. The invention also relates to a baseband front-end device for a multi-standard receiver.

Description

BASEBAND FRONT-END FOR MULTI STANDARD RECEIVER

Technical field

The present invention relates generally to radio receiver architectures and analog-to-digital converters. More specifically, the invention concerns low power, high integration of radio frond-end for multi-standard and multi-mode communication systems.

Technical background The proliferation of 2^nd generation wireless and cellular standards and the imminent arrival of the 3^rd generation cellular and satellite standard, has resulted in the development of many terminal architectures to the support wireless the TDMA (GSM), WCDMA (UMTS) and DECT wireless access methods. To ensure widespread acceptance and usage, it is important for timeliness to be capable of multi-standard operation, yet meet the commercial constraints of cost, size and power-consumption. One of the most critical points to overcome in multi-standard terminals for mobile and personal communication systems is to find the maximum number of commonalties to allow the highest possible degree of integration, under the constraints of low voltage and low power consumption. The starting point for multi-standard timeliness is to setup a common radio architecture capable to afford the various standards.

The most popular architecture of a radio subsystem is the so called * superheterodyne receiver". However this will developed receiver architectures require lots of external bandpass filters, such as high performance image rejection filter and IF channel selection filer, which are not amenable to integration and not cost effective for future production. To overcome the above limitations, the obvious way is to develop an architecture which is more suitable for integration, in which the number of oscillators is reduced, and the IF functions (with associated passive filters) are suppressed, shifting the most important multi-standard operations to the baseband processing (preferable processed in low cost digital CMOS technology) , of channel filtering and analog-to-digital processing.

Several radio receiver architectures are employed in the modern mobile terminal. These are superheterodyne receiver, low-IF receiver, zero-IF receiver and wide-band double-IF receiver. Each of them has its own prons and cons. Wide-band double-IF receiver has been investigated to be used in GSM/DECT multi-band receiver. This part briefly describes the state-of-the-art multi-standard receiver research.

The superheterodyne receiver remains the architecture of choice for the vast majority of RF applications in the world today. Its perennial popularity is due to its ability to reproducibly pick out narrow-bandwith high-frequency signals from the surrounding background clutter of signals outside the frequency range of interest. The RF signal is applied to a low-noise amplifier (LNA) and subsequently an image-reject filter. The combination of extremely high performance and low power requirement result in the LNA being one of the most significant power drains in the system. The image reject (IR) filter is typically implemented with a physically large surface acoustic wave (SAW) filter. In addition to their size, these filters have extremely unforgiving sensitivities to variations in source impedance, ground loops, and so on. The resulted signal from the IR filter is mixed with the output of a local oscillator (LO) , thus producing the intermediate-frequency (IF) signal. The IF filter suppresses out-of-channel interferes, performing channel selection.

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Summary of the invention

The object of this invention is to enable a receiver to efficiently handle several different wireless communication standards. The object is achieved by a multi-standard receiver as well as a baseband front-end device according to the appended claims.

According to the invention a multi-standard receiver adopted to a plurality of wireless communication standards, comprises: receiving means arranged to receive RF signals having different bandwidths;

TDD switch means and a plurality of bandpass filter means each adopted to a different standard, said TDD switch means being arranged to switch an incoming signal to a respective one of said plurality of bandpass filter means in dependence of the standard according to which the signal is transmitted; a plurality of LNA means, each connected to a respective bandpass filter and adopted to a corresponding standard; mixer means arranged to provide a baseband signal by downconverting the received signal directly to baseband centered at DC; baseband analog processing means comprising filtering means for fixed standard specific filtering of the baseband signal and for standard specific automatic gain control; analog-to-digital converter means, comprising a sig a-delta modulator, for providing a digital signal, said converter means being hardware reconfigurable for different sampling frequency and different quantizing in dependence of different standard baseband signals; and a programmable decimation filter being programmable into different standard filtering modes for filtering different standard digital signals received from said analog-to-digital converter means, and comprising filter means being used in at least two different standard modes. . Further, according to the invention there is provided a baseband front-end device for a multi-standard receiver, the device comprising: baseband analog processing means comprising filter- ing means for receiving and fixed standard specific filtering of a baseband signal and for standard specific automatic gain control; analog-to-digital converter means connected to said baseband analog processing means, and comprising a sigma- delta modulator, for providing a digital signal, said converter means being hardware reconfigurable for different sampling frequency and different quantizing in dependence of different standard baseband signals; and a programmable decimation filter being programmable into different standard filtering modes for filtering said digital signal received from said analog-to-digital converter means, and comprising filter means being used in at least two different standard modes.

The processing means operating at baseband frequency and being arranged for fixed standard filtering in combination with the programmable decimation filter provides for a simplified and efficient filtering operation for all standards involved. The use of a sigma-delta modulator arranged for different quantizing in dependence of the presently used standard additionally provides for an increased efficiency since different standards require differently advanced quantizing.

In an embodiment of the multi standard receiver according to this invention the programmable decimation filter comprises a multi-stage digital filter, with hardware sharing among different standards. This sharing simplifies the structure of the receiver and facilitates integration thereof.

Further objects and advantages of the present inven- tion will be discussed below by means of exemplary embodiments . Brief description of the drawing

Exemplifying embodiments of the invention will be described below with reference to the accompanying drawings, in which: Fig. 1 is a schematic block diagram of a prior art superheterodyne receiver;

Fig. 2 is a schematic block diagram of a prior art direct-conversion receiver;

Fig. 3 is a schematic block diagram of a prior art low-IF receiver;

Fig. 4 is a schematic block diagram of a prior art wideband dobuble-IF receiver;

Fig. 5 is a schematic block diagram of an embodiment of a receiver according to the present invention; Fig. 6-9 show different portions of the receiver embodiment of Fig. 5 in more detail.

Description of embodiments

Referring now to Fig. 5-9 an embodiment of the receiver according to the present invention constitutes a zero-IF radio architecture for a TDD UMTS (WCDMA/GSM) with DECT-supportive terminal. Because of the TDD operation mode the terminal does not require simultaneous transmission and reception, thus a TDD switch can be used at the front-end instead of a duplexer. For a FDD UMTS terminal, the TDD switch should be replaced by a duplexer for WCDMA while the TDD switch is still needed for GSM and DECT.

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Claims

1. A multi-standard receiver adopted to a plurality of wireless communication standards, and comprising: receiving means arranged to receive RF signals having different bandwidths;

TDD switch means and a plurality of bandpass filter means each adopted to a different standard, said TDD switch means being arranged to switch an incoming signal to a respective one of said plurality of bandpass filter means in dependence of the standard according to which the signal is transmitted; a plurality of LNA means, each connected to a respective bandpass filter and adopted to a corresponding standard; mixer means arranged to provide a baseband signal by downconverting the received signal directly to baseband centered at DC- baseband analog processing means comprising filter- ing means for fixed standard specific filtering of the baseband signal and for standard specific automatic gain control; analog-to-digital converter means, comprising a sigma-delta modulator, for providing a digital signal, said converter means being hardware reconfigurable for different sampling frequency and different quantizing in dependence of different standard baseband signals; and a programmable decimation filter being programmable into different standard filtering modes for filtering different standard digital signals received from said analog-to-digital converter means, and comprising filter means being used in at least two different standard modes .

2. A multi-standard receiver according to claim 1, said filtering means of said baseband analog processing means comprising a filter structure having an at least 6- order filtering characteristic and a variable gain ampli- fier, wherein said filtering characteristic is fixed for the standard with widest signal bandwidth.

3. A multi-standard receiver according to claim 1 or 2, said plurality of wireless communication standards comprising at least one of GSM, DECT and WCDMA standard.

4. A multi-standard receiver according to anyone of the preceding claims, wherein said sigma-delta modulator is arranged as a 2-2 cascaded architecture, constituted by a first and a second stage, and comprises, at the second stage, a 1-bit quantizer, a 3-bit quantizer and a switching mechanism connected to said quantizers, said switching mechanism being operable for switching between said quantizers for obtaining said different quantizing.

5. A multi-standard receiver according to anyone of the preceding claims, wherein said programmable decimation filter comprises a multi-stage digital filter, with hardware sharing among different standards.

6. A baseband front-end device for a multi-standard receiver, the device comprising: baseband analog processing means comprising filtering means for receiving and fixed standard specific filtering of a baseband signal and for standard specific automatic gain control; analog-to-digital converter means connected to said baseband analog processing means, and comprising a sigma- delta modulator, for providing a digital signal, said converter means being hardware reconfigurable for different sampling frequency and different quantizing in dependence of different standard baseband signals; and a programmable decimation filter being programmable into different standard filtering modes for filtering said digital signal received from said analog-to-digital converter means, and comprising filter means being used in at least two different standard modes.