Method and apparatus for measuring adjacent channel power using complex fourier transform

Claim 2

A measuring method of a leakage power of a transmitting signal from a transmitting channel to a channel adjacent thereto, the transmitting signal for the transmitting channel being produced from a tested objective, comprising the steps of: performing a frequency conversion to convert said transmitting signal to an intermediate frequency signal of a predetermined intermediate frequency; sampling said intermediate frequency signal with a predetermined sampling frequency to convert it to a digital signal; resolving said digital signal into an in-phase component and a quadrature component; removing a high frequency component from each of said in-phase and quadrature components; executing a complex Fourier transformation for said in-phase and quadrature components from which said high frequency components are removed, to obtain a frequency spectrum; and computing said leakage power to the adjacent channel from said frequency spectrum.

Claim 3

The measurement method according to claim 1, wherein said leakage power is computed after a noise floor of a measurement system is measured and a power value in the frequency spectrum is compensated based on said noise floor.

Claim 4

The measurement method according to claim 1, wherein a decimation processing is executed for said in-phase and quadrature components from which said high frequency component are removed, and the complex Fourier transformation is executed for said in-phase and quadrature components after having being subjected to the decimation processing.

Claim 5

The measurement method according to claim 1, wherein said predetermined intermediate frequency is lower than a frequency of said transmitting signal.

Claim 6

The measurement method according to claim 3, wherein said leakage power is computed after a noise floor of a measurement system is measured and a power value in the frequency spectrum is compensated based on said noise floor.

Claim 7

The measurement method according to claim 1, wherein an instantaneous value of a cosine function of a predetermined frequency and an instantaneous value of a sine function of said predetermined frequency are produced every sampling, and each of said instantaneous values is multiplied by said digital signal, thereby resolving said digital signal into said in-phase and quadrature components.

Claim 8

A measurement apparatus for a leakage power which measures the leakage power of a transmitting signal to a channel adjacent to a transmitting channel, said transmitting signal for said transmitting channel being produced from a tested objective, comprising: a frequency conversion means for converting said transmitting signal into an intermediate frequency signal of a predetermined intermediate frequency; an A/D conversion means for sampling said intermediate frequency signal with a predetermined sampling frequency to convert it into a digital signal; a quadrature detection means for resolving said digital signal into an in-phase component and a quadrature component; a Fourier transformation means for executing a complex Fourier transformation for said in-phase component and said quadrature component provided from said quadrature detection means to obtain a frequency spectrum; and a computing means for computing said leakage power from said frequency spectrum.

Claim 9

A measurement apparatus for a leakage power which measures the leakage power of a transmitting signal to a channel adjacent to a transmitting channel, said transmitting signal for said transmitting channel being produced from a tested objective, comprising: a frequency conversion means for converting said transmitting signal into an intermediate frequency signal of a predetermined intermediate frequency; an A/D conversion means for sampling said intermediate frequency signal with a predetermined sampling frequency to convert it into a digital signal; a quadrature detection means for resolving said digital signal into an in-phase component and a quadrature component; a Fourier transformation means for executing a complex Fourier transformation for said in-phase component and said quadrature component provided from said quadrature detection means to obtain a frequency spectrum; and a computing means for computing said leakage power from said frequency spectrum.

Claim 10

The measurement apparatus according to claim 7, wherein a low-pass filter means for removing a high frequency component from each of said in-phase and quadrature components is arranged between said quadrature detection means and said Fourier transformation means.

Claim 11

The measurement apparatus according to claim 8, wherein a decimation means for thinning out data of said in-phase and quadrature components at a predetermined rate is inserted between said low-pass filter means and said Fourier transformation means.

Claim 12

The measurement apparatus according to claim 7, wherein said quadrature detection means comprises a first signal generating means for generating an instantaneous value of a cosine function of a predetermined frequency every sampling; a first multiplication means for multiplying an output from said first signal generating means with said digital signal to output the multiplication result as a signal of the in-phase component; a second signal generating means for generating an instantaneous value of a sine function of said predetermined frequency every said sampling; and a second multiplication means for multiplying an output from said second signal generating means with said digital signal to output a multiplication result as a signal of the quadrature component signal.

Claim 13

The measurement apparatus according to claim 7, wherein said predetermined intermediate frequency is lower than a frequency of said transmitting signal.