Patent ID: 8355884
Filing Date: 2013-01-15
Classification: G01R,H04B

Abstract:
1. A signal quality measurement device that includes a transmitter and a receiver that are objects of testing; a waveform attenuator for, after having attenuated a measured signal supplied as output from said transmitter, applying said measured signal as input to said receiver; and a spectrum measurement circuit for measuring the signal strength of said measured signal that was supplied as output from said transmitter; said spectrum measurement circuit comprising: an N-(where N is an integer equal to or greater than 4) phase clock generation circuit for supplying phase-modulated signals obtained by shifting the phase of a clock signal by a phase modulation amount each time the settings of the phase modulation amount are switched; a mixer circuit for taking the products of said measured signal that was supplied from said transmitter and said phase-modulated signals supplied from said N-phase clock generation circuit; an average value output circuit for supplying an average voltage value of the output signal of said mixer circuit; a memory for storing said average voltage value supplied from said average value output circuit for each said phase modulation amount of said N-phase clock generation circuit; an arithmetic unit for using said average voltage value for each said phase modulation amount of said N-phase clock generation circuit stored in said memory to calculate signal strength of said measured signal; a comparator for determining the sizes of said average voltage value that is supplied from said average value output circuit and a reference voltage value; a counter for increasing or decreasing a counter value in accordance with the determination result realized by said comparator; and a digital-analog converter for converting the counter value of said counter from a digital value to an analog value and supplying to said comparator said reference voltage value that accords with the converted analog value, wherein said N-phase clock generation circuit, in the measurement of the signal strength of the carrier frequency component of said measured signal, supplies said phase-modulated signals whose phases differ from each other, whose frequency is identical, and further, the values of the phases of each are known, and wherein said memory stores, as said average voltage value, the counter value of said counter at the time that said average voltage value supplied from said average value output circuit and said reference voltage value become equal.