JPS63108807A - Frequency synthesizer - Google Patents

Abstract

PURPOSE:To enable an element to be used even when it is the element whose speed of response is not so high, by taking out a signal having a prescribed high-order frequency spectrum out of generated frequency spectra. CONSTITUTION:A prescribed waveform data is stored in a memory device 2, and when a data is set at a data setting unit 4, an address signal generator 3 reads out the waveform data stored at a prescribed address from the memory device 2. The waveform data is supplied to a voltage controlled band-pass filter (VCF)6 via a D/A converter 5. The VCF6 passes only a signal of prescribed frequency band area set at an output frequency setting unit 9. The signal is amplified again, and is outputted from a frequency synthesizer 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a frequency synthesizer that directly generates waveforms using digital signals.

[Conventional technology]

Conventionally, for this type of purpose, a method has been used in which the waveform data is directly read out at a high sampling speed from a memory device that stores the waveform data, and then converted to an analog signal using a D/A converter to obtain a signal at the desired frequency. Ta.

[Problem that the invention seeks to solve]

In the above conventional method, two of the target frequencies to be obtained are
Since it is necessary to sample waveform data at twice the frequency or more, there is a problem in that if the desired frequency is high, the response speed of the constituent elements must also be increased.

In addition, if there are multiple target frequencies to be obtained, it is necessary to use multiple sampling frequencies when reading the waveform data from the storage device, or to store the waveform data as multiple waveform data. There was a problem in that capacity was required.

[Technical means to solve the problem]

The present invention has been made in view of the above-mentioned problems, and is based on a frequency synthesizer that directly generates a waveform using a digital signal. We took measures to extract the signal.

[Effect]

That is, when waveform data of frequency fc is input as a digital signal to a D/A converter in synchronization with a sampling signal of frequency fs, fundamental waves fc and n-f are generated as shown in Fig. 1.
A frequency spectrum of sffc (n is a natural number) is generated. In principle, each spectral component contains information about the wave number.

Here, in order to obtain a predetermined frequency spectrum component, for example, when passing through a voltage-controlled bandpass filter (V CF), a control signal to the voltage-controlled band-pass filter (VCF) controls the predetermined frequency band. Since only the spectral components can be passed through, a signal of a predetermined high-order spectral component can be obtained.

In other words, even if the waveform data is processed at a low frequency, a signal with a sufficiently high frequency can be obtained.

〔Example〕

An embodiment of the present invention will be described below based on FIG. 2.

In FIG. 2, the frequency synthesizer 1 includes a memory device R2 and a memory device 2 for storing predetermined waveform data.
The address signal for reading out the predetermined waveform data (frequency fc (Hz)) is converted into a sampling signal (frequency fs (Hz)).
Hz)), a data setter 4 for setting the initial value of the address signal generator 3, and converting the waveform data read from the memory device F2 into an analog signal. D/A controller 5,
A voltage-controlled bandpass filter (VCF) 6 that passes only a predetermined frequency spectrum component according to a voltage control signal, and an output frequency setter 7 that outputs a predetermined control signal to the voltage-controlled bandpass filter (VCF) 6. , and an amplifier 7.

Here, addresses M1, M2, M3, .
Since the waveform data of Dl, D2, D3, . . . are stored respectively from . Since the address signal starting from is repeatedly sent to the memory device 2, the digital signal representing the waveform data of D2 is input to the D/A converter 5 and converted into the original analog signal. However, in addition to the fundamental wave, this analog signal has nXf s! : f c (k
Hz) (n is a natural number), so it is input to a voltage-controlled bandpass filter (VCF) 6. Here, if the output frequency setter 9 is set to select n-7 and the upper side wave, the voltage controlled bandpass filter (
VCF) 6 passes only a signal with a frequency of 7×f3+fc (kHz). This signal is amplified again and output from the frequency synthesizer 1. Also, if you set the output frequency setter 7 to select n-8 and upper side wave, 8
A signal with a frequency of Xf s+f c (kHz) is obtained.

In this way, signals of a plurality of frequencies can be obtained from the same waveform data by changing the setting value of the output frequency setter 7.

At this time, a signal with a frequency higher than the operating frequency of the memory device 2 can be obtained.

Note that a normal bandpass filter may be used instead of the voltage controlled bandpass filter (VCF) 6 described above.

〔effect〕

As described above, the frequency synthesizer according to the present invention can obtain a sufficiently high frequency signal even if it processes waveform data at a low frequency, so it has the advantage that it can use elements that do not have particularly fast response speeds. be.

Another advantage is that signals of various frequencies can be obtained based on the same waveform data.

[Brief explanation of the drawing]

FIG. 1 is a frequency spectrum distribution diagram, and FIG. 2 is a block diagram of an embodiment of a frequency synthesizer according to the present invention. 1... Frequency synthesizer 2... Memory device 3... Address signal generator 4... Data setter 5... D/A converter 6... Voltage controlled bandpass filter (VCF) 7 ...Output frequency setter fc...Waveform data fs...Sampling frequency

Claims (1)

[Claims] In a frequency synthesizer that directly generates a waveform using a digital signal, a frequency synthesizer extracts a signal of a predetermined higher-order frequency spectrum from among the generated frequency spectrum components.