JPH04286207A - Optional waveform generator - Google Patents

Abstract

PURPOSE:To generate a continuous modulated wave within minimum memory length by preserving previously waveform data in a waveform memory, and reading and analog-converting repeatedly the waveform data. CONSTITUTION:Two systems of the waveform memories 1, 2 and DA converters 3, 4 are provided, and a data converter 8 to generate the waveform data in orthogonal relation with each other to be preserved in the waveform memories 1, 2 on the basis of the information of a modulating system and a carrier wave, and gain changers 5, 6 of two systems 5, 6 to change each gain in order to change the mixing ratio of analog signals outputted from DA converters 3, 4 of two systems, and an adder 7 to synthesize one analog signal by summing the outputs of the gain changers 5, 6 of two systems are provided. In this case, at the time of generating the waveform, the gains of the gain changers 5, 6 are changed by a control circuit 9 in conformity to a read-out period from the waveform memories 1, 2. Then, the necessary change of the gain is determined at the time of the generation of the waveform by the data converter 8.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an arbitrary waveform generator.
In particular, the present invention relates to improvements in functions for increasing the degree of freedom in generating modulated signals.

0002

2. Description of the Related Art The principle of an arbitrary waveform generator that generates arbitrary waveforms is shown in FIG. In the figure, WM is a waveform memory that stores arbitrary waveform data, DA is a digital-to-analog converter (hereinafter referred to as a DA converter) that converts the waveform data read from waveform memory 1 into analog, and CG is a waveform data readout and DA converter. A clock generator that generates a clock for conversion. When generating analog continuous signals in such a configuration, data on the waveform memory WM is repeatedly used.

[Problems to be Solved by the Invention] By the way, such conventional arbitrary waveform generators can only generate periodic signals whose maximum period is determined by the memory size, and cannot generate modulated waves such as arbitrary AM modulated waves or FM modulated waves. If you try to do this, the following problems will occur. When the modulation signal and the carrier wave are asynchronous with each other, there is generally only one point in time in the entire time axis of the modulation signal when the modulation signal and the carrier wave have a specific phase relationship. This is because the phase of the carrier wave is indefinite when the phase of the modulation signal is zero. Therefore, even if the modulation signal is a periodic signal such as a sine wave signal, the sampled modulation wave is not strictly a periodic signal, so it is understood that it is impossible to generate such a modulation wave. If such a modulated wave were to be generated, a memory of infinite length would be required, which would be unrealizable. In reality, this can be generated by assuming a synchronous relationship between the modulated signal and the carrier wave and converting the modulated wave into a periodic signal. At this time, if the relationship between the frequency ratio of the modulated wave and the carrier wave is not simple, an enormous memory size is required to generate a periodic signal. On the other hand, especially AM modulated waves can be generated by adding a multiplier to the digital or analog part of the configuration of FIG. However, whether it is an analog multiplier or a digital multiplier, its speed is generally slow, more than an order of magnitude slower than other components such as waveform memory and DA converters, and it is less practical in terms of balance with other components. . In addition, in order to continuously generate arbitrary FM modulated waves, it is necessary to further control the sampling clock, or to provide a configuration immediately before the DA converter in which the output frequency can be controlled by frequency data. Therefore, the configuration becomes complicated, and the circuit inevitably increases in size and the upper limit frequency decreases. An object of the present invention is to create a modulated wave with continuous phase for the carrier wave even if the modulated signal and the carrier waveform are asynchronous with each other by simply storing one period of the modulated signal in a waveform memory regardless of the period of the carrier wave. The object of the present invention is to provide an arbitrary waveform generator that can perform the following functions and is no different from conventional waveform generators in terms of speed.

0003

[Means for Solving the Problem] In order to achieve such an object, the present invention stores waveform data in a waveform memory, repeatedly reads out the waveform data, and converts it into analog to generate a periodic signal. The arbitrary waveform generator is equipped with two systems of waveform memories and DA converters, and is a data converter that generates mutually orthogonal waveform data stored in the two waveform memories based on modulation method and carrier wave information. and two gain switchers that switch the respective gains in order to change the mixing ratio of the analog signals output from the two DA converters, and the outputs of these two gain switchers are added to 1. It is characterized by being equipped with an adder for combining into two analog signals.

0004

[Operation] By switching the gain in two gain switchers and changing the mixing ratio when adding the outputs of each DA converter, discontinuity in each cycle when reading from the waveform memory is eliminated, and the analog signal Continuous output.

[0005]

EXAMPLES The present invention will be explained in detail below. FIG. 1 is a block diagram showing an embodiment of an arbitrary waveform generator according to the present invention. In the figure, 1 is a first waveform memory that stores arbitrary waveform data such as a modulated wave, 2 is a second waveform memory that stores waveform data that has a component orthogonal to the waveform stored in waveform memory 1, and 3 and 4 are DA converters that convert the data in waveform memories 1 and 2 into analogs, respectively; 5 and 6 are gain switchers for changing the mixing ratio of two series of analog signals output from the DA converters. 7 is an adder that adds the outputs of the gain switchers 5 and 6, and 8 is a data converter, which provides information such as arbitrary waveforms, modulation signals, carrier waves, etc., and generates mutually orthogonal components. Various methods can be applied depending on the modulation method and the type of modulation signal. Reference numeral 9 denotes a control circuit which switches the gain of the gain switch every cycle according to the reading cycle from the waveform memory when a waveform is generated. The necessary gain change is obtained when the data converter 8 generates the waveform. Reference numeral 10 denotes a sampling clock generator that generates a common sampling clock to be applied to each part when generating a waveform. The operation in such a configuration will be explained next. Here, we will take as an example a case where an AM modulated wave with a modulation depth of 100% is generated. The modulation signal is a sine wave with a frequency of 21 MHz, and the carrier wave frequency is 106 MHz. The sampling frequency may be selected appropriately. (1) Generation of waveform data The length of the data stored in the waveform memory is one period of the modulation signal, the frequency of the modulation signal is fm, and the frequency of the carrier wave is fc.
shall be. The data converter 8 calculates the data to be written into the waveform memories 1 and 2 for each of the A and B series using the following equations. Note that the maximum amplitude of the waveform was set to 2. A series: (1+sin (2πfm ・t))・c
os (2πfc ・t) B series: (1+sin
(2πfm·t))·sin (2πfc·t) Waveform data based on this formula is stored in the waveform memories 1 and 2. (2) The size of data (number of data) given to the phase difference waveform memory at the discontinuous point is equal to one period of the modulation signal. Therefore, the phase of the carrier wave of the data in the waveform memory becomes discontinuous between the beginning and the end of the waveform memory. The amount of discontinuity can be determined as follows. 106 (MHz) x (1/21 (MHz)) x 36
0 (deg) = 17.14, +5 x 360 (deg
) Therefore, approximately 17 degrees (d
eg) The phase will shift. (3) Waveform generation The operation of reading waveform data from the waveform memories 1 and 2 and converting it into analog data using a DA converter is similar to the conventional operation. However, it is necessary to switch the gain using the gain switchers 5 and 6 every cycle of the waveform memory. The mixing ratio should be the value obtained by the following formula. First, if the initial phase in the Nth period when a waveform is generated is PN, then the next initial phase PN+
1 is as follows. PN+1=PN+D Here, D is the phase difference of the carrier wave in one period of the modulation signal, and is the value obtained in the above (2). Since PN is obtained as described above, the mixing ratio in each period is as follows. A series: cos (PN) B series: sin (PN) The gain is switched by the gain switchers 5 and 6 so that this mixture ratio is achieved. The outputs of the gain switchers are added together by an adder 7 and output as one analog signal. As described above, even if the modulation signal and carrier waveform are asynchronous with each other, it is possible to generate a modulated wave with continuous phase for the carrier wave by simply storing data for one period of the modulation signal in the waveform memory. can. Although the embodiments have been described using AM modulation as an example, the present invention is not limited to this and can also be applied to other modulation methods.

[0006]

[Effects of the Invention] As explained above, according to the present invention,
In particular, when generating an arbitrary modulated signal, by adding not only amplitude information but also phase information as data to be written to the waveform memory, a continuous modulated wave can be generated with the minimum memory length without worrying about the phase continuity of the carrier wave. It can be used in practice and has great effects.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of an arbitrary waveform generator according to the present invention.

FIG. 2 is a configuration diagram showing an example of a conventional arbitrary waveform generator.

[Explanation of symbols]

1, 2 Waveform memory 3,4 DA converter 5, 6 Gain switcher 7 Adder 8 Data converter 9 Control circuit

Claims (1)

[Claims] [Claim 1] Waveform data is stored in a waveform memory,
An arbitrary waveform generator that generates a periodic signal by repeatedly reading out the waveform data and converting it into analog, and is equipped with two systems of waveform memories and DA converters, and the two waveform memories are stored in a mutually orthogonal relationship. A data converter that generates waveform data based on modulation method and carrier wave information, and two-system gain switching that switches the gain of each to change the mixing ratio of analog signals output from the two DA converters. When generating a periodic signal by repeatedly using the data in the waveform memory, the end of the waveform memory An arbitrary waveform generator characterized in that an analog output waveform is made continuous by switching the gain using a gain switcher when moving from the first data to the first data.