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Quadrature modulator with pulse-shaping

A technology of IQ modulator and modulation method, applied in modulation carrier system, baseband system, phase modulation carrier system, etc., can solve problems such as difficulty in meeting combination requirements

Inactive Publication Date: 2004-03-17
APPLE INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0013] However, it is difficult to meet this combination requirement

Method used

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  • Quadrature modulator with pulse-shaping
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  • Quadrature modulator with pulse-shaping

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Embodiment Construction

[0029] In a preferred IQ modulator implemented by a low-cost, programmable IC for portable cellular applications, a multi-accumulator polynomial generator is used. The use of a multi-accumulator polynomial generator allows any desired pulse-shaping filter to be obtained. The impulse response on each symbol period can be approximated by a fourth-order polynomial, where the coefficients of each of the fourth orders are expressed as X1d(i), X2d(i), X3(i), X4(i), where i is the sequence number of the corresponding symbol period. The finite impulse response filter (FIR) does not work at an oversampling rate, but at a symbol period of 1X.

[0030] figure 1 Shows the signal processing flow for generating filter coefficients such as the fourth-order FIR working with a symbol period of 1X.

[0031] For example, in EDGE mode, the impulse response spans 5 symbol periods. Therefore, each FIR only requires 5 taps. As a result, a complexity equal to 5×270.8333×4=5410 thousand operations per s...

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Abstract

An IQ modulator and method for modulating a signal in accordance with I and Q symbols using derivative FIR's operating at the symbol rate and programmable multi-accumulators for waveform generator. This provides advantages that reduced complexity is produced compared with traditional FIR's by a factor equal to the quotient of oversampling ratio and derivative order; programmability to Digital Very Low IF mode transmission is possible; the same circuit may perform interpolation for narrow band MA's; and reduced sets of coefficients enable implementation of two sets of coefficients for MA's, allowing fast handover between MA's such as EDGE and IS136.

Description

Technical field [0001] The present invention relates to IQ (in-phase component, quadrature phase component) modulation of a signal. Specifically (but not exclusively), it involves IQ modulation in a wireless transmitter used in a communication system such as a cellular communication system. [0002] IQ modulators can usually be seen in wireless transmitters that provide multi-mode modulation, that is, in devices such as EDGE (improved data rate GSM service), IS136 (second-generation TDMA air interface standard), IDEN (enhanced digital network) , ICO (Medium Circular Orbit System), IS95 (CDMA Air Interface), and other multi-modes that use linear modulation schemes to perform modulation. Background technique [0003] In the technical field of the present invention, it is well known that IQ modulation can be performed using a finite impulse response filter (FIR) that works at an oversampling ratio (of the sampling rate of I and Q samples), with A coefficient equal to the product of ...

Claims

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Application Information

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IPC IPC(8): H03H17/02H03H17/06H04L25/03H04L27/20H04L27/36
CPCH04L25/03834H04L27/00
Inventor 纳迪姆·哈拉特
Owner APPLE INC