Hewlett-packard Company

Agilent Technologies, Inc.

Hewlett-packard Corporation

Raymond A Birgenheier

Richard P Ryan

George Stennis Moore

David M Hoover

Michael T Wende

Robert R Collison

A system analyzer may generate an estimated frequency response of a device, system, communication medium, or combination thereof by utilizing a stimulus signal that is robust against IQ modulator impairments. A stimulus generator may be used to generate a plurality of discrete tones according to a frequency spacing and a frequency offset. The frequency spacing and the frequency offset cause spectrally inverted spurs (generated by impairments of the IQ modulator) to occur at frequencies other than frequencies of said modulated signal that are associated with said plurality of discrete tones. Additionally, by implementing a Discrete Fourier Transform (DFT) to possess a frequency resolution equal to the frequency offset, there is no leakage of power associated with the spectrally inverted spurs into frequency bins of the DFT associated with the desired frequency components. Likewise, leakage between the desired frequency components and leakage associated with the local oscillator may be avoided.

Systems and methods of using IQ modulation for calibration or measurement

A method and system characterizes an IF response of a receiver under test, such that an effect on the characterization by errors associated with uncertainties in knowledge of an RF stimulus signal used to perform the characterization is reduced. The method includes determining an estimate of an actual IF response of the receiver under test from IF responses of the receiver under test measured at overlapping frequency bands and a set of conversion coefficients computed therefrom, such that the estimate reduces the effect of the errors. The system includes a signal generator, an IF processor, a computer program, and a controller that controls the generator and the processor and executes the computer program. When a receiver under test is characterized, the receiver is connected between the signal generator, the IF processor and the controller. The computer program includes instructions that implement characterizing the receiver IF response.

IF frequency response characterization employing overlapping frequency bands

A method and apparatus for determining the phase and amplitude accuracy of continuous-phase-modulated signals is described. A modulated RF signal generated by a transmitter is down converted to a relatively low intermediate frequency which is filtered and sampled by a high sampling rate analog-to-digital converter. A digital signal processor processes the digital signals to produce a measured phase function corresponding to the modulated RF signal. From the measured amplitude and phase functions, an estimate of the ideal reference phase function corresponding to the modulated RF signal is calculated and synthesized. The reference phase function is compared to the measured phase function to determine the phase function from which the modulated RF signal phase error and frequency error are computed.

Method and apparatus for measuring modulation accuracy

In a conventional ROM-based digital filtering methodology, N past samples of M-bit input symbols are used to address a memory containing a desired filtered output signal. This memory must have an address space of 2.sup.M*N. According to the present invention, a desired filtered output signal is defined as a composition of signal terms, each of which is a function of less than M*N bits. Individual ROMs are provided for each of these component terms. Address bits for the ROMs are derived from the N past samples of the M-bit input symbols. The ROM outputs are combined to yield the desired filtered output signal.

Baseband modulation system with improved ROM-based digital filter

A method and apparatus for determining the phase and amplitude accuracy of continuous-phase-modulated signals is described. A modulated RF signal generated by a transmitter is down converted to a relatively low intermediate frequency which is filtered and sampled by a high sampling rate analog-to-digital convertor. A digital signal processor processes the digital signals to produce a measured amplitude function and a measured phase function corresponding to the modulated RF signal. From the measured amplitude and phase functions, an ideal phase function corresponding to the modulated RF signal is calculated and synthesized. The ideal phase function is compared to the measured phase function to determine the phase function from which the modulated RF signal phase error and frequency error are computed.

Method and apparatus for measuring phase accuracy and amplitude profile

A programmable premodulation filter having a finite impulse response to digitally filter a digital data signal to provide a modulation signal for modulating an RF carrier signal is described. A digital summer and accumulator are programmed to provide a finite impulse response to a bimodal impulse signal which represents the input digital data signal. Several impulse response functions g(t) are stored in a ROM (or RAM) and may be selected to reprogram the digital filter to provide a desired modulation format. When a RAM is used, additional impulse response functions may be input to the RAM and the stored impulse response functions may be dynamically modified to provide the desired modulation format.

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Spokane, WA, United States of America

Raymond A Birgenheier