1. Field of the Invention
The present invention relates to a pulse generator for generating pulses with a desired pulse width, a timing generator for generating signals with a desired frequency, and a pulse width adjustment method for adjusting the pulse width of pulses generated by a pulse generator.
2. Related Art
A conventional pulser is known for generating pulses with a desired pulse width. Such a pulser includes a delay circuit for delaying an input pulse, and a logic computation circuit for creating a pulse with a desired pulse width by performing logic computation based upon the input pulse and the delayed signal, as disclosed in FIG. 3 of Japanese Patent No. 3499051, for example.
In some cases, multiple pulsers having such a configuration are connected with one another. Such an arrangement is employed in order to prevent pulses from decaying and disappearing due to their being transmitted through a long transmission path.
Also, in some cases, a pulser is provided to the input of each of circuits connected in series, in order to adjust the pulse width of the input pulse for each input with high precision.
In such a case, there is a need to adjust the pulse width output from each pulser with high precision.
FIG. 4 is a diagram which shows an example of the configuration of a conventional pulse generator 400 including multiple pulsers. As shown in FIG. 4, in the conventional pulse generator 400 having a configuration in which multiple pulsers are connected in series, the pulse width of the pulses output from a final-stage pulser 430 is measured, and the delay amount is adjusted for each pulser. Next, description will be made regarding conventional pulse width measurement.
Upon receiving a trigger pulse, an OR circuit 470 creates a pulse. The pulse thus created is input to a pulser 410 through a fixed pulser 480 and a delay circuit 490.
Each of the pulsers 410, 420, and 430 has a function of outputting a pulse with a predetermined pulse width adjusted on the basis of the input pulse.
The output pulse output from the pulser 430 is input to the pulser 410 as a feedback signal via an exclusive OR circuit 440, a flip-flop 450, a counter 460, an OR circuit 470, the fixed pulser 480, and the delay circuit 490.
The flip-flop 450 outputs the logic high signal in response to either the rising edge or the falling edge of the input pulse. This signal thus output is supplied to the reset terminal of the flip-flop 450 via the OR circuit 470 and the fixed pulser 480, thereby setting the output of the flip-flop 450 to the logic low state. As a result, the flip-flop 450 outputs a pulse, and the pulse thus output is input to the pulser 410 as a feedback signal.
The exclusive OR circuit 440 controls whether or not the output pulse of the pulser 430 is inverted before being input to the flip-flop 450. In a case of receiving an inverted output pulse, the operation of the flip-flop 450 is delayed by a period of time corresponding to the pulse width of the output pulse thus received compared to a case of receiving a non-inverted output pulse. This allows the pulse width of the output pulse to be measured based upon the difference between the loop cycle time of an inverted output pulse and the loop cycle time of a non-inverted output pulse. Each pulse is adjusted based upon the pulse width thus measured.
However, with the conventional pulse generator 400, pulses also pass through multiple pulsers (410, 420, 430) in a case of using a pulse loop method to measure the pulse width. Such an arrangement leads to irregularities among these pulsers with respect to the delay time of the pulse rising edge and the pulse falling edge.
This leads to an error in the pulse width of the output pulse obtained based upon the difference between the loop cycle time of an inverted output pulse and the loop cycle time of a non-inverted output pulse.
In some cases, various kinds of devices may be provided between the multiple pulsers (410, 420, 430) corresponding to the usage of the pulse generator 400. Such an arrangement increases irregularities in the delay time described above, leading to a problem that the pulse width cannot be measured with high precision.