Jitter generation apparatus, device test system using the same, and jitter generation method

A jitter generation apparatus including an arrangement for applying phase modulation to a phase locked loop, which comprises:

• voltage controlled oscillator means;
• frequency divider means for frequency-dividing a frequency of a signal output from the voltage controlled oscillator means at a predetermined frequency division ratio;
• phase comparator means for receiving an output from the frequency divider means at one input terminal, receiving a reference clock signal at the other input terminal, comparing the output from the frequency divider means with a phase of the reference clock signal, and outputting a signal corresponding to a phase difference between the output and the reference clock signal;
• filter means for removing a predetermined frequency component from an output signal from the phase comparator means;
• jitter addition means for outputting a signal filtered through the filter means by adding a predetermined jitter corresponding to an amplitude of a first modulation signal to that signal upon reception of the externally supplied first modulation signal, and controlling a frequency of the signal output from the voltage controlled oscillator means by the output signal added with the jitter;
• and
• frequency division ratio varying means for varying the frequency division ratio of the frequency divider means according to the amplitude of the first modulation signal upon reception of the first modulation signal, so as to vary the predetermined jitter added by the jitter addition means;
• wherein the apparatus further comprises:
• first level control means for performing level control of the first modulation signal and applying a level-controlled first modulation signal to the jitter addition means;
• second level control means for performing level control of first modulation signal and applying a level-controlled modulation signal to the frequency division ratio varying means;
• parameter setting means for setting parameters associated with a desired jitter to be generated by the jitter generation apparatus;
• a quadrature modulator which has a local signal input terminal and two modulation signal input terminals, allows a local signal which is input to the local signal input terminal and is output with the jitter added from the voltage controlled oscillator means to pass through the quadrature modulator, and quadrature-modulates a non-modulated local signal which is input to the local signal input terminal and is output without the jitter added from the voltage controlled oscillator means, based on a second modulation signal and outputs quadrature-modulated local signal, in accordance with input states to the two modulation signal input terminals;
• amplitude limiting means for limiting an amplitude of the output signal from the quadrature modulator to a constant amplitude;
• switching means configured to switch an input state to the two modulation signal input terminals of the quadrature modulator between a first state in which zero is input to one of the two modulation signal input terminals and a nonzero fixed value is input to the other, and a second state in which the second modulation signal is input to at least one of the two modulation signal input terminals;
• and
• a control unit which controls the jitter generation apparatus having the arrangement for applying the phase modulation to the PLL to finally output a signal added with the desired jitter based on the parameters set by the parameter setting means from the amplitude limiting means, respectively controls, when the switching means is switched to the first state as a result of switching control of the switching means to the first state or the second state, the first level control means and the second level control means so that the local signal, which is obtained by adding the desired jitter in which an amplitude of the first modulation signal matches the parameter set by the parameter setting means to the output signal from the voltage controlled oscillator means, passes through the quadrature modulator and is input to the amplitude limiting means, and respectively controls, when the switching means is switched to the second state, the first level control means and the second level control means so that an output, which is obtained by applying quadrature modulation to the non-modulated local signal which is input to the quadrature modulator without adding any jitter to the output signal from the voltage controlled oscillator means based on the second modulation signal, is input to the amplitude limiting means.