Electronic apparatus and signal processing method

1 . An electronic apparatus comprising:

a signal generating circuitry configured to generate a first signal and a second signal;

a first characteristic circuitry configured to acquire a first distorted signal by giving a first distortion characteristic to the first signal, and acquire a second distorted signal by giving the first distortion characteristic to the second signal;

a first time-characteristic circuitry configured to acquire a third distorted signal by giving a first time-characteristic, which is a distortion characteristic that changes with time, to the first distorted signal and acquire a fourth distorted signal by giving a second time-characteristic, which is different from the first time-characteristic and is a distortion characteristic that changes with time, to the second distorted signal;

a second characteristic circuitry configured to acquire a fifth distorted signal by giving a second distortion characteristic to the third distorted signal, and acquire a sixth distorted signal by giving the second distortion characteristic to the fourth distorted signal; and

a processing circuitry configured to estimate at least one of the first distortion characteristic and the second distortion characteristic based on the first signal, the second signal, the fifth distorted signal, and the sixth distorted signal.

2 . The electronic apparatus according to claim 1 , wherein the processing circuitry at least either:

estimates the first distortion characteristic by canceling the second distortion characteristic through a first arithmetic operation based on the first signal, the second signal, the fifth distorted signal, and the sixth distorted signal; or

estimates the second distortion characteristic by canceling the first distortion characteristic through a second arithmetic operation based on the first signal, the second signal, the fifth distorted signal, and the sixth distorted signal.

3 . The electronic apparatus according to claim 2 , wherein the processing circuitry:

estimates the first distortion characteristic based on an eigenvector of a signal, of which the second distortion characteristic is canceled; or

estimates the second distortion characteristic based on an eigenvector of a signal, of which the first distortion characteristic is canceled.

4 . The electronic apparatus according to claim 1 , wherein:

the first distortion characteristic causes linear distortion on a frequency axis to the first signal and the second signal; and

the second distortion characteristic causes linear distortion on the frequency axis to the third distorted signal and the fourth distorted signal.

5 . The electronic apparatus according to claim 4 , wherein:

the first distortion characteristic applies an affine transformation to the first signal and the second signal on the frequency axis; and

the second distortion characteristic applies an affine transformation to the third distorted signal and the fourth distorted signal on the frequency axis.

6 . The electronic apparatus according to claim 1 , wherein at least one of the first distortion characteristic and the second distortion characteristic includes an IQ imbalance.

7 . The electronic apparatus according to claim 1 , wherein:

the first time-characteristic changes, with time, at least one of a phase, an amplitude, a frequency, and an impulse response of the first distorted signal; and

the second time-characteristic changes, with time, at least one of a phase, an amplitude, a frequency, and an impulse response of the second distorted signal.

8 . The electronic apparatus according to claim 1 , wherein:

the first distortion characteristic and the second distortion characteristic change with time; and

amounts of change in the first distortion characteristic and the second distortion characteristic per unit time are smaller than amounts of change in the first time-characteristic and the second time-characteristic per unit time.

9 . The electronic apparatus according to claim 1 , wherein:

the first time-characteristic circuitry includes a plurality of pieces of equipment each of which changes at least one of a phase, an amplitude, a frequency, and an impulse response of a signal inputted to the first time-characteristic circuitry; and

the first time-characteristic circuitry switches among the plurality of pieces of equipment with time, thereby giving the first time-characteristic to the first distorted signal and giving the second time-characteristic to the second distorted signal.

10 . The electronic apparatus according to claim 1 , wherein:

the first time-characteristic circuitry includes a frequency converter;

the frequency converter changes, with time, a frequency shift amount given to the first distorted signal, thereby giving the first time-characteristic to the first distorted signal, and changes, with time, a frequency shift amount given to the second distorted signal, thereby giving the second time-characteristic to the second distorted signal; and

the frequency converter is part of the second characteristic circuitry.

11 . The electronic apparatus according to claim 10 , wherein the frequency converter is a mixer.

12 . The electronic apparatus according to claim 11 , wherein the mixer frequency-converts a radio signal from an RF band to a BB band.

13 . The electronic apparatus according to claim 11 , wherein the first time-characteristic circuitry includes a local oscillator configured to generate a local oscillation signal used by the mixer for frequency conversion, and noise changing with time is added to the local oscillation signal generated by the local oscillator, thereby giving the first time-characteristic to the first distorted signal and giving the second time-characteristic to the second distorted signal.

14 . The electronic apparatus according to claim 7 , wherein the first time-characteristic circuitry includes an amplifier and changes at least one of the phase, the amplitude, the frequency, and the impulse response with time using the amplifier.

15 . The electronic apparatus according to claim 1 , wherein:

between the first time-characteristic circuitry and the second characteristic circuitry, one or more different Mth characteristic circuitries (M is an integer equal to or larger than 3) and one or more different Pth time-characteristic circuitries (P is an integer equal to or larger than 2) are at least partially provided alternately;

the first characteristic circuitry outputs two signals, namely the first distorted signal and the second distorted signal, to the first time-characteristic circuitry, and the first time-characteristic circuitry outputs two signals, namely the third distorted signal and the fourth distorted signal, to the Mth characteristic circuitry on an output side of the first time-characteristic circuitry;

the Mth characteristic circuitry gives an Mth distortion characteristic to the two distorted signals inputted from the first time-characteristic circuitry on an input side of the Mth characteristic circuitry or from the Pth time-characteristic circuitry and thereby outputs the two distorted signals to the Pth time-characteristic circuitry on an output side of the Mth characteristic circuitry, and the Pth time-characteristic circuitry gives time characteristic, which are distortion characteristic differing from each other and changing with time, to two distorted signals inputted from the Mth characteristic circuitry on a input side of the Pth time-characteristic circuitry and outputs the two distorted signals to the Mth characteristic circuitry on the output side or to the second characteristic circuitry; and

the processing circuitry switches a time-characteristic circuitry whose function is to be stopped among the one or more different Pth time-characteristic circuitry and the first time-characteristic circuitry and thereby estimates the Mth distortion characteristic of at least one of the one or more different Mth characteristic circuitries.

16 . The electronic apparatus according to claim 1 , wherein at least one of the first characteristic circuitry and the second characteristic circuitry includes one or more filters configured to attenuate a signal having any frequency component, and the filters give the first distortion characteristic and the second distortion characteristic.

17 . The electronic apparatus according to claim 1 , wherein:

the first signal differs in frequency band from the fifth distorted signal; and

the second signal differs in frequency band from the sixth distorted signal.

18 . The electronic apparatus according to claim 1 , further comprising:

an amplifier circuitry connected to an output of the first characteristic circuitry and configured to amplify a signal; and

a selecting circuitry configured to connect an input of the first time-characteristic circuitry selectively to any one of an input and an output of the amplifier circuitry,

wherein the processing circuitry:

estimates the first distortion characteristic by connecting the selecting circuitry to the input of the amplifier circuitry, and

connects the selecting circuitry to the output of the amplifier circuitry, inputs a seventh distorted signal and an eighth distorted signal to the first time-characteristic circuitry, the seventh distorted signal resulting from giving the first distortion characteristic and a characteristic of the amplifier circuitry to the first signal, the eighth distorted signal resulting from giving the first distortion characteristic and the characteristic of the amplifier circuitry to the second signal, thereby estimates a product of the first distortion characteristic and the characteristic of the amplifier circuitry, and estimates the characteristic of the amplifier circuitry based on the estimated product and the estimated first distortion characteristic.

19 . The electronic apparatus according to claim 18 , further comprising:

a distortion compensating circuitry configured to compensate a third signal generated by the signal generating circuitry for distortion, based on the first distortion characteristic and the characteristic of the amplifier circuitry, the first distortion characteristic and the amplifier circuitry characteristic being estimated by the processing circuitry; and

an output circuitry configured to output a signal resulting from the third signal compensated by the distortion compensation circuitry, then given the first distortion characteristic by the first characteristic circuitry, and amplified by the amplifier circuitry.

20 . The electronic apparatus according to claim 19 , wherein the output circuitry includes an antenna configured to transmit a radio wave based on the signal.

21 . A signal processing method comprising:

generating a first signal and a second signal;

acquiring a first distorted signal by giving a first distortion characteristic to the first signal, and acquiring a second distorted signal by giving the first distortion characteristic to the second signal;

acquiring a third distorted signal by giving a first time-characteristic, which is a distortion characteristic that changes with time, to the first distorted signal and acquiring a fourth distorted signal by giving a second time-characteristic, which is different from the first time-characteristic and is a distortion characteristic that changes with time, to the second distorted signal;

acquiring a fifth distorted signal by giving a second distortion characteristic to the third distorted signal, and acquiring a sixth distorted signal by giving the second distortion characteristic to the fourth distorted signal; and

estimating at least one of the first distortion characteristic and the second distortion characteristic based on the first signal, the second signal, the fifth distorted signal, and the sixth distorted signal.