Mobile terminal test device and mobile terminal test method
A first shift unit ( 14 ) that shifts an amplitude value of the I baseband signal and an amplitude value of the Q baseband signal in a lower direction by the predetermined number of bits so that the predetermined number of lower bits thereof have a value after a decimal point, a first rounding unit ( 15 ) that rounds-to-even the amplitude value of the I baseband signal and the amplitude value of the Q baseband signal shifted by the first shift unit ( 14 ) with a rounding width of 1 in decimal notation, and a first averaging unit ( 16 ) that respectively calculates a time average of the amplitude value of the I baseband signal and the amplitude value of the Q baseband signal rounded by the first rounding unit ( 15 ) are included.
1. A mobile terminal test device, comprising:
a frequency conversion unit that converts frequency of an analog signal to be measured;
an A/D converter that samples the signal to be measured which has been converted frequency by the frequency conversion unit, and converts the sampled signal to be measured into a binary digital data having a predetermined number of bits;
an orthogonal demodulator that orthogonal-demodulates the digital data outputted from the A/D converter and generates an I baseband signal and a Q baseband signal that are orthogonal to each other;
a shift unit that shifts a numerical information of the I baseband signal and a numerical information of the Q baseband signal in a lower direction by a predetermined number of bits so that the predetermined number of lower bits have a value after a decimal point;
a rounding unit that rounds-to-even the numerical information of the I baseband signal and the numerical information of the Q baseband signal shifted by the shift unit to with a rounding width of 1 in decimal notation; and
an averaging unit that respectively calculates a time average of the numerical information of the I baseband signal and the numerical information of the Q baseband signal rounded by the rounding unit.
2. The mobile terminal test device according to claim 1 , wherein
the numerical information of the I baseband signal is an amplitude value of the I baseband signal,
the numerical information of the Q baseband signal is an amplitude value of the Q baseband signal,
the shift unit shifts the amplitude value of the I baseband signal and the amplitude value of the Q baseband signal in a lower direction by a predetermined number of bits so that the predetermined number of lower bits have a value after a decimal point.
3. The mobile terminal test device according to claim 2 , further comprising
a first signal processing unit that, when the signal to be measured is a signal based on the time division duplex system, performs signal processing for extracting the time average values in the non-transmission time of the time division duplex system from among the time average values calculated by the averaging unit.
4. The mobile terminal test device according to claim 1 , wherein
the signal to be measured is an analog modulation signal,
the numerical information of the I baseband signal is an amplitude value of an I symbol data,
the numerical information of the Q baseband signal is an amplitude value of a Q symbol data,
the mobile terminal test device further comprises a constellation calculation unit that calculates the I symbol data and the Q symbol data for expressing the I baseband signal and the Q baseband signal as a constellation on an IQ plane, per each modulation symbol of the signal to be measured,
the shift unit shifts the amplitude values of the I symbol data and the Q symbol data corresponding to each of the modulation symbols on the constellation in lower direction by the predetermined number of bits so that the predetermined number of lower bits have a value after a decimal point.
5. The mobile terminal test device according to claim 4 , further comprising:
a normalization factor calculation unit that calculates a normalization factor for converting the amplitude value of the I symbol data and the amplitude value of the Q symbol data rounded by the rounding unit to measurement points on the constellation, using the time average value calculated by the averaging unit;
a normalization unit that calculates the measurement points on the constellation by normalizing the amplitude value of the I symbol data and the amplitude value of the Q symbol data rounded by the rounding unit, by the normalization factor calculated by the normalization factor calculation unit; and
an EVM average value calculation unit that calculates an absolute value of an amplitude of an error vector between an ideal point on the constellation and a measurement point obtained by the normalization unit and calculates a time average value of the absolute value.
6. A mobile terminal test method, comprising:
a frequency conversion step to convert frequency of an analog signal to be measured;
an A/D conversion step to sample the signal to be measured which has been converted frequency by the frequency conversion step, and convert the sampled signal to be measured into a binary digital data having a predetermined number of bits;
an orthogonal demodulation step to orthogonal-demodulate the digital data outputted from the A/D conversion step and generate an I baseband signal and a Q baseband signal that are orthogonal to each other;
a shift step to shift a numerical information of the I baseband signal and a numerical information of the Q baseband signal in a lower direction by a predetermined number of bits so that the predetermined number of lower bits thereof have a value after a decimal point;
a rounding step to round-to even the numerical information of the I baseband signal and the numerical information of the Q baseband signal shifted by the shift step with a rounding width of 1 in decimal notation; and
an averaging step to respectively calculate a time average of the numerical information of the I baseband signal and the numerical information of the Q baseband signal rounded by the rounding step.
7. The mobile terminal test method according to claim 6 , wherein
the numerical information of the I baseband signal is an amplitude value of the I baseband signal,
the numerical information of the Q baseband signal is an amplitude value of the Q baseband signal.
8. The mobile terminal test method according to claim 6 , wherein
the signal to be measured is an analog modulation signal,
the numerical information of the I baseband signal is an amplitude value of an I symbol data of the I baseband signal,
the numerical information of the Q baseband signal is an amplitude value of a Q symbol data of the Q baseband signal,
the mobile terminal test method further comprises a constellation calculation step to calculate the I symbol data and the Q symbol data for expressing the I baseband signal and the Q baseband signal as a constellation on an IQ plane, per each modulation symbol of the signal to be measured.
9. The mobile terminal test device according to claim 8 , further comprising: a normalization factor calculation step to calculate a normalization factor for converting the amplitude value of the I symbol data and the amplitude value of the Q symbol data rounded by the rounding step to measurement points on the constellation, using the time average value calculated by the averaging step;
a normalization step to calculate the measurement points on the constellation by normalizing the amplitude value of the I symbol data and the amplitude value of the Q symbol data rounded by the rounding step, by the normalization factor calculated by the normalization factor calculation step; and
an EVM average value calculation step to calculate an absolute value of an amplitude of an error vector between an ideal point on the constellation and a measurement point obtained by the normalization step and calculate a time average value of the absolute value.