Browse Prior Art Database

METHOD FOR GENERATING MULTI-PHASE OUTPUTS FROM A DDS

IP.com Disclosure Number: IPCOM000006709D
Original Publication Date: 1992-Dec-01
Included in the Prior Art Database: 2002-Jan-24
Document File: 2 page(s) / 93K

Publishing Venue

Motorola

Related People

Bob Stengel: AUTHOR [+2]

Abstract

Direct Digital Synthesis (DDS) systems can be source systems are an image rejection mixer and a lii- expanded to provide integrated multiple signal sources ear power amplifier using a phase power combination. with independent phase offset relative to a given refer- The image rejection (IR) in the mixer example is deter- exe. Two application examples of multi-phase signal mined by the following relation: IR = -1Olog l+A'-2Acost3 1 +A2+2Acos8 -& Where: A = 10 0 = phase offset For a phase offset of 5' with &B = 0 the IR = A multi-phase signal source with integrated independ- -27.2dB, where the phase offset is a combination of all ent phase adjustment can reduce system cost, complex- the phase imbalance difference in the multiple signal ity, and size by achieving high performance phase com- source and the paths. A similar result occurs in a phase bination with path and component phase imbalance combinational linear power amplifier, where the phase compensation. offset becomes an error in the desired signal power level.

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0 M MO-LA

INC. Technical Developments Volume 17 December 1992

METHOD FOR GENERATING MULTI-PHASE OUTPUTS FROM A DDS

by Bob Stengel and Wayne Shepherd

  Direct Digital Synthesis (DDS) systems can be source systems are an image rejection mixer and a lii- expanded to provide integrated multiple signal sources ear power amplifier using a phase power combination. with independent phase offset relative to a given refer- The image rejection (IR) in the mixer example is deter- exe. Two application examples of multi-phase signal mined by the following relation:

IR = -1Olog

l+A'-2Acost3

1 +A2+2Acos8

-&

Where: A = 10

0 = phase offset

  For a phase offset of 5' with &B = 0 the IR = A multi-phase signal source with integrated independ- -27.2dB, where the phase offset is a combination of all ent phase adjustment can reduce system cost, complex- the phase imbalance difference in the multiple signal ity, and size by achieving high performance phase com- source and the paths. A similar result occurs in a phase bination with path and component phase imbalance combinational linear power amplifier, where the phase compensation.
offset becomes an error in the desired signal power level.

Clock

I

Computation

= amplitude offset

-

@(n)

Sinewave output

Modulation -

Figure 1. Tiemey er al. architecture for DDFS.

  Figure 1, is an example of a direct digital synthesizer using phase computation and a DAC convertor. The phase computation, DAC converter, and low-pass falter can be replaced with a ROM look up table plus DAC and filter

or an analog memory storage system.' The multi-phase output system is shown in Figure 2, with the use of a ROM look-up and DAC for the output signal generation.

"'Direct Digital Synthesis using Analog EEPROM" Motorola Publication.

117

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