JPH0337324B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a frequency doubling circuit that doubles the frequency of an input signal.

[Prior Art] For example, in a synthesizer, a signal with an extremely stable frequency obtained from a crystal oscillator or the like is converted into a signal with a stable desired frequency using a frequency synthesizer. There is. One such frequency synthesizer is a frequency doubling circuit that doubles the frequency of an input signal.

Conventionally, such a frequency doubling circuit is configured as shown in FIG. 5, for example. That is, an input signal having a frequency f (period T) inputted from the input terminal 1 is inputted to the full-wave rectification circuit 2 and subjected to full-wave rectification. The full-wave rectified signal output from the full-wave rectifier circuit 2 is input to the signal input terminal of the variable bandpass filter 3. On the other hand, the input signal input from the input terminal 1 is also input to the frequency-voltage conversion circuit 4. And this frequency voltage conversion circuit 4
From there, a voltage signal proportional to the frequency f of the input signal is input to the pass frequency control terminal of the variable bandpass filter 3. In this variable bandpass filter 3, the pass frequency of the signal input to the signal input terminal changes in response to changes in the voltage input to the pass frequency control terminal. Therefore, the frequency f' of the output signal of the variable bandpass filter 3 can be controlled by changing the voltage value input to the pass frequency control terminal.

In the frequency doubling circuit configured in this manner, when an input signal a having a sinusoidal waveform having a frequency f is input to the input terminal 1 as shown in FIG. The signal is full-wave rectified at , and becomes a full-wave rectified signal b. Therefore, this full-wave rectified signal b has, in addition to the frequency component of f, which is the fundamental frequency of the input signal a, a frequency component of twice the frequency 2f. This full-wave rectified signal b is then input to the signal input terminal of the variable bandpass filter 3.

In addition, since the input signal a is input to the frequency-voltage conversion circuit 4, the variable bandpass filter 3
The frequency f of the input signal a is input to the pass frequency control terminal of
A voltage signal c having a voltage E _F proportional to is applied. In this state, the output voltage E _F of the frequency-voltage conversion circuit 4 is adjusted so that the passing frequency of the variable bandpass filter 3 becomes the frequency 2f included in the full-wave rectified signal b. Therefore, if the bandwidth of the passing frequency of the variable bandpass filter 3 is narrow enough to eliminate adjacent frequency components (f, 3f, 4f,...), the output from the variable bandpass filter 3 to the output terminal 5 is output signal d
becomes a sine waveform with frequency 2f.

Therefore, the frequency of the output signal d output from the output terminal 5 is twice the frequency of the input signal input to the input terminal 1. When the frequency f of the input signal a changes, the voltage signal c of the frequency-voltage conversion circuit 4 also changes in proportion to the change in the frequency f, so that the passing frequency of the variable bandpass filter 3 also changes from the frequency f of the input signal a. Changes in proportion to change. As a result, the input signal a is always output from the output terminal 5.
An output signal d having twice the frequency is obtained.

[Problems to be Solved by the Invention] However, the frequency doubling circuit configured as described above has the following problems.
That is, the input signal a is subjected to full-wave rectification in order to extract from the input signal a a frequency component twice the frequency f of the input signal a. Therefore, the input signal a
If it is not a sine waveform but a rectangular waveform, it is necessary to convert this rectangular waveform into a sine wave signal and then input it to the input terminal 1. Therefore, a separate conversion circuit is required to convert the rectangular wave signal into a sine wave signal.

In addition, when the frequency f of the input signal a becomes a high frequency of about GHz, the waveform distortion that occurs after rectification,
In other words, for example, due to an unbalance in the full-wave rectified waveform caused by differences in the characteristics of bridge-connected rectifying elements, the ratio of the input signal frequency component to the double frequency component may increase in the output waveform, or the ratio of the fundamental frequency and the desired high frequency may increase. Because the frequencies of the components are close to each other, even if the band width of the passing frequency of the variable bandpass filter 3 is narrowed, there will be a large amount of the above input signal components and high frequency components in addition to the signal component with twice the frequency required for the output signal d. may be included. This is because it is difficult to obtain a variable bandpass filter 3 with a large ratio of passing/blocking characteristics in a frequency range of approximately the GHz band. Therefore, in the frequency doubling circuit shown in Fig. 5,
It does not operate as an accurate doubler circuit in the high frequency region of the GHz band.

The present invention has been made based on these circumstances, and its purpose is to detect a predetermined level of an input signal waveform and generate a rectangular wave, that is, to detect a predetermined level of an input signal waveform and generate a rectangular wave. ) and the π phase position. By extracting twice the frequency component in this way, we can create a frequency doubling circuit that can accurately obtain twice the frequency signal over a wide frequency range up to high frequencies of about GHz, regardless of the type of input signal waveform. It is about providing.

[Means for Solving the Problems] The frequency doubling circuit of the present invention shapes an input signal into a rectangular waveform signal whose signal level is inverted between the 0 phase position and the π phase position of the input signal waveform. a waveform shaping circuit; and a pulse shaping circuit that outputs a pulse having a predetermined time width shorter than a high level period or a low level period of the rectangular wave signal when the rectangular wave signal changes from a high (H) level to a low (L) level. a second pulse generating circuit that outputs a pulse having substantially the same width as the predetermined time width when the rectangular wave signal changes from a low level to a high level; an OR circuit that ORs the pulse signals output from the pulse generation circuit and outputs a signal having twice the frequency component of the input signal; and a frequency-voltage conversion circuit that outputs a voltage corresponding to the frequency of the input signal. A variable band pass that is connected to the OR circuit and the frequency-voltage conversion circuit and is controlled by the output voltage of the frequency-voltage conversion circuit so as to pass a signal with twice the frequency of the input signal output by the OR circuit. It is equipped with a filter.

[Operation] With the frequency doubling circuit configured in this way, the input signal input from the input terminal is converted by the waveform shaping circuit into a pulse signal whose signal level changes at a predetermined level of the input waveform. . Then, the first and second pulse generation circuits obtain a pulse signal that cycles at the signal level change time. As a result, the OR circuit outputs two pulses that are synchronized at the times when the signal waveform rises and falls at a predetermined level within one cycle of the input signal, and a signal with twice the frequency component of the input signal is output from the variable band. Input to path filter. Since a voltage proportional to the frequency of the input signal output from the frequency-voltage conversion circuit is applied to the passing frequency control terminal of this variable bandpass filter, the output voltage level of the frequency-voltage conversion circuit can be adjusted. Then, the variable bandpass filter outputs an output signal having twice the frequency of the input signal.

[Example] An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a frequency doubling circuit according to an embodiment. In the figure, reference numeral 11 denotes an input terminal to which an AC input signal is input, and this input terminal 11 is connected to an input terminal of a waveform shaping circuit 12. This waveform shaping circuit 12 outputs a pulse signal whose signal level is inverted between the 0 phase position and the π phase position in one cycle of the signal waveform of the AC input signal. Specifically, the signal level is inverted when the waveform crosses the 0V voltage line. This waveform shaping circuit 12
The non-inverting output terminal Q of is connected to the first pulse generating circuit 13 formed by a one-shot multivibrator.
The inverted output terminal is connected to the trigger input terminal T of a second pulse generation circuit 14 having the same configuration as the first pulse generation circuit 13 . These first and second pulse generation circuits 1
3 and 14 are pulse signals that cycle at the rising time of the signal input to the trigger terminal T from the L level to the H level and remain at the H level for a predetermined time _T0 determined by the time constant of the resistor and capacitor from this rising time. Output from output terminal Q. Note that the value of the predetermined time T ₀ is set to a value of approximately 1/2 of the period corresponding to the maximum frequency of the input signal input to the input terminal 11.

Each output terminal Q of the first and second pulse generation circuits 13 and 14 is connected to each input terminal of an OR circuit 15, and the output terminal of this OR circuit 15 is connected to a signal input terminal of a variable bandpass filter 16. It is connected.

Further, the input terminal 11 is connected to an input terminal of a frequency-voltage conversion circuit 17, and an output terminal of the frequency-voltage conversion circuit 17 is connected to a passing frequency control terminal of the variable bandpass filter 16. This variable bandpass filter 16 outputs from the signal output terminal only the frequency component corresponding to the voltage input to the pass frequency control terminal among the frequency components of the signal input from the signal input terminal. A signal output terminal of this variable bandpass filter 16 is connected to an output terminal 18 of this frequency doubling circuit.

The operation of the frequency doubling circuit configured as described above will be explained using the time chart shown in FIG. That is, the frequency f (period T) is input to the input terminal 11.
When a sine wave input signal g of The signal is waveform-shaped. Then, pulse signals h and i whose signal levels are symmetrical to each other are output from Q and the terminal. Therefore, the pulse signal h output from the Q terminal rises from L level to H level at the 0 (2π) phase position of input signal g, and the pulse signal output from the terminal rises to L level at the π phase position of input signal g. Rising from level to H level.

The first and second pulse generation circuits 13 and 14 to which the pulse signals h and i are input to the trigger terminal T,
The rise time (0
A pulse signal j that rises in synchronization with the phase position (phase position, π phase position) and continues at the H level for a predetermined time _T0 ,
k is output from each output terminal Q. These pulse signals j and k are combined in an OR circuit 15 and inputted to a signal input terminal of a variable bandpass filter 16 as an OR signal l. Therefore, as shown in the figure, the signal waveform of this OR signal l includes two pulse waveforms each having a predetermined time _T0 width from the 0 phase position and the π phase position within one cycle T of the input signal g. It will be done. In other words, this OR signal l
contains a frequency 2f component that is twice the frequency f of the input signal g.

Since the frequency of the output signal output from the variable bandpass filter 16 is varied by the voltage value E _F of the voltage signal m output from the frequency-voltage conversion circuit 17, the output voltage level of the frequency-voltage conversion circuit 17 is of the OR signal l input to the input terminal
Adjust so that the 2f frequency component is output. Therefore, an output signal n having a frequency 2f twice that of the input signal g is obtained from the output terminal 18. Note that the DC voltage signal m output from the frequency-voltage conversion circuit 17 has a voltage value E _F proportional to the frequency f of the input signal g, so once the output signal level is adjusted as described above, even if the input signal g Even if the frequency f changes, there is no need to readjust it.

Figure 3 shows that the frequency of input signal g is f/2 (period
2T), and shows the signal waveforms of each part when the frequency of the input signal g becomes 1/2.
The frequency component included in the logical sum signal l input to the signal input terminal of the variable bandpass filter 16 is also (1/2)×2f, that is, f, and the voltage of the voltage signal m output from the frequency-voltage conversion circuit 17 is also The value also becomes a voltage value corresponding to the frequency f. Therefore, the variable bandpass filter 16 passes the signal with the frequency f, and as a result, the frequency of the output signal n at the output terminal 18 also becomes f.

In this way, an output signal n having a frequency 2f twice the frequency f of the input signal g input to the input terminal 11 is always outputted to the output terminal 18. When the frequency f of the input signal g changes, the frequency of the output signal n also changes in proportion to the change in the frequency of the input signal g.

With the frequency doubling circuit configured as in the present invention, the waveform of the input signal g may not be a sine wave waveform as shown in FIG. It may be other points. Also, for example, as shown in FIG. 4, the period T
Even if the signal waveform is a rectangular one having a frequency f, each output terminal Q of the waveform shaping circuit 12 outputs each pulse signal h whose signal level is inverted at the 0 phase position and the π phase position as shown in the figure. i is obtained. Therefore, it is possible to apply not only sine wave signals but also various signal waveforms.

Further, even if the amplitude value of the input signal g input to the input terminal 11 changes midway, the 0 phase position and the π phase position of the input signal waveform do not change.
Therefore, the inversion position of the signal level of the rectangular wave pulse signals h and i output from the waveform shaping circuit 12 does not change. Further, each pulse signal j output from the first and second pulse generation circuits 13 and 14,
Since the duty ratio of k does not change, the amplitude value of the output signal n output from the variable bandpass filter 16 does not change. That is, it is possible to obtain a stable output signal that always has a constant amplitude.

In addition, since the full-wave rectifier circuit used in conventional circuits is not used, there is no need to consider the adverse effects of the aforementioned waveform distortion and unbalance of the full-wave rectified waveform due to full-wave rectification processing, so high frequencies of about GHz Accurately double frequency signals can be obtained over a wide frequency range up to

[Effects of the Invention] As explained above, according to the frequency doubling circuit of the present invention, the 0 phase position and π in the input signal waveform
The phase position is detected and twice the frequency component is extracted. Therefore, regardless of the type of input signal waveform, a signal with twice the frequency can be obtained accurately over a wide frequency range up to high frequencies on the order of GHz.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram showing a frequency doubling circuit according to an embodiment of the present invention, FIGS. 2 to 4 are time charts showing the operation, and FIG. 5 is a block configuration diagram showing a conventional frequency doubling circuit. , FIG. 6 is a time chart showing the operation of the conventional circuit. 11...Input terminal, 12...Waveform shaping circuit, 1
3...First pulse generation circuit, 14...Second pulse generation circuit, 15...OR circuit, 16...Variable band pass filter, 17...Frequency voltage conversion circuit.

Claims (1)

[Claims] 1. A waveform shaping circuit 12 that shapes an input signal into a rectangular waveform signal whose signal level is inverted at the 0 phase position and the π phase position of the waveform of the input signal, Low (L)
A first pulse generating circuit 1 that outputs a pulse having a predetermined time width shorter than the high level period or low level period of the rectangular wave signal when the signal changes to the high level.
3, and a second pulse generating circuit 14 that outputs a pulse having a width substantially the same as the predetermined time width when the rectangular wave signal changes from a low level to a high level.
and an OR circuit 15 that ORs the pulse signals output from the first and second pulse generation circuits to output a signal having twice the frequency component of the input signal; A frequency-voltage conversion circuit 17 that outputs a corresponding voltage is connected to the OR circuit and the frequency-voltage conversion circuit, and is configured to pass a signal having a frequency twice that of the input signal output by the OR circuit. , and a variable bandpass filter 16 controlled by the output voltage of the frequency-voltage conversion circuit.