JP2570987B2 - FM high frequency transmitter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FM radio frequency transmitter, and more particularly to an FM radio frequency transmitter having an FM modulation circuit using a voltage controlled oscillator.

[0002]

2. Description of the Related Art A voltage-controlled oscillator (hereinafter, referred to as a VCO) capable of changing an oscillation frequency in accordance with an applied control voltage is known, and a variable capacitance diode is used for this type of VCO. Things are often used.

FIG. 4 shows a control voltage-oscillation frequency characteristic of a VCO. The horizontal axis represents the control voltage, and the vertical axis represents the oscillation frequency.

[0004] The control voltage applied to the VCO and the oscillation frequency at that time are not proportional and non-linear, and have a curve as shown in FIG.

[0005]

FIG. 5 shows a time-oscillation frequency characteristic when a voltage having a sawtooth waveform is applied as a control voltage of the VCO. The horizontal axis represents time, and the vertical axis represents oscillation frequency.

FIG. 4 shows a control voltage-oscillation frequency characteristic of a VCO.
For example, when it is desired to obtain an oscillation frequency having a saw-tooth waveform as shown by a broken line in FIG. 5 also becomes as shown by the solid line in FIG. 5, and the oscillation frequency as shown by the broken line in FIG. 5 cannot be obtained.

This problem is not limited to the case where the oscillation frequency of the VCO is a sawtooth waveform, but can be applied to any repetitive waveform.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and is directed to an FM high-frequency transmitting apparatus for transmitting an FM repetitive waveform by a voltage-controlled oscillator using a variable capacitance diode. The purpose is to correct the gender.

[0009]

In order to achieve the above object, the present invention has a voltage-controlled oscillator that oscillates a frequency according to a control voltage using a variable capacitance diode.
In an FM high-frequency transmitting apparatus for transmitting an FM modulated wave having an arbitrary repetitive waveform, a sine wave having the same frequency as the fundamental frequency of the repetitive waveform is input, and the fundamental wave of the sine wave and the frequency are integers of the fundamental wave. A frequency multiplier that outputs a voltage having a frequency component of a double harmonic, a separating unit that separates the voltage output from the frequency multiplier for each frequency component, and a voltage divider for each frequency component from the separating unit. Attenuating means for attenuating the amplitude by a predetermined amount of attenuation, shifting means for shifting the phase of the voltage for each frequency component from the attenuating means by a predetermined amount of shifting, and Superimposing means for superimposing and outputting a voltage for each frequency component, and applying an FM high frequency so that the voltage from the superimposing means is applied as a control voltage to the voltage controlled oscillator. You configure the communication apparatus.

[0010]

According to the present invention, the frequency multiplier to which the sine wave is input outputs a voltage composed of a fundamental wave and a harmonic, the separating means separates this voltage for each frequency component, and the attenuating means has the above structure. The amplitude of the voltage for each frequency component is attenuated by a predetermined attenuation amount, and the shifting means shifts the phase of the voltage for each frequency component by the predetermined shifting amount. This superimposed voltage is applied as a control voltage to the voltage controlled oscillator.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of an FM modulation circuit in an FM radio frequency transmitting apparatus according to the present invention.

Reference numeral 6 denotes a sine wave input terminal. The frequency of the sine wave voltage input to this terminal is selected as the fundamental frequency f ₀ of the repetitive sawtooth waveform transmitted by the FM high-frequency transmitting device.
Reference numeral 1 denotes a frequency multiplier, which is a fundamental wave of a sine wave input from the terminal 6 and a harmonic whose frequency is an integral multiple, that is, f
A voltage having frequency components of ₀ , 2f ₀ , 3f ₀ , 4f ₀ , 5f ₀ ... Is generated and output. 21, 22, 23,
Reference numeral 24 denotes a band-pass filter, 21 passes only the fundamental wave of the frequency f ₀ , 22 passes only the harmonic of the frequency 2f ₀ , 23 passes only the harmonic of the frequency 3f ₀ , and 24 denotes the frequency. Only the harmonic of 4f ₀ is passed. 3
Reference numerals 1, 32, 33, and 34 denote variable attenuators, which attenuate input fundamental waves and harmonics at a predetermined ratio. 42, 4
Variable phase shifters 3 and 44 shift the phase of the input harmonic. Reference numeral 7 denotes a control voltage application terminal to which the outputs of the variable attenuator 31 and the variable phase shifters 42, 43, and 44 are superimposed and applied. 5 is a VCO using a variable capacitance diode
(Voltage-controlled oscillator), and the control voltage −
Has oscillation frequency characteristics. An oscillation frequency output terminal 8 outputs the oscillation frequency from the VCO 5.

Next, the principle of the FM modulation circuit shown in FIG. 1 will be described.

[0015]

(Equation 1) Equation 1 is a Fourier expansion formula of the sawtooth wave. Therefore, VC
When a sawtooth waveform voltage is applied to the control voltage O5, the voltage may be applied through a circuit that realizes Equation 1. The FM modulation circuit shown in FIG. 1 is configured based on such a concept, and the variable attenuators 31, 32, 33, and 34 are represented by Equation (1).
/ M), and the variable phase shifters 42, 43, and 44 realize (-1) ^m-1 of Expression 1 (where m = 1 to 4).

However, when a voltage having a simple sawtooth waveform is applied as the control voltage of the VCO 5, the waveform becomes as shown by a solid line in FIG. 5, and an oscillation frequency having a sawtooth waveform cannot be obtained. Therefore, in the present invention, the variable attenuator 3
By adjusting the amplitude attenuation at 1, 32, 33 and 34 and the phase shift at variable phase shifters 42, 43 and 44, when a high frequency oscillation is desired, a voltage larger than a voltage having a simple sawtooth waveform is applied to VCO 5. The voltage was applied as a control voltage.

FIG. 2 shows a time-voltage characteristic applied to the terminal 7 as a control voltage of the VCO 5 shown in FIG. 1, wherein the horizontal axis represents time and the vertical axis represents voltage.

The voltage applied to the terminal 7 as the control voltage of the VCO 5 is higher than the voltage having a simple sawtooth waveform as shown by the solid line in FIG. In FIG. 2, the voltage shown by the broken line is a saw-tooth waveform voltage having the same oscillation frequency as the conventional one as shown by the solid line in FIG.

FIG. 3 shows a time-oscillation frequency characteristic at the output terminal 8 of the VCO 5 shown in FIG.

FIG. 1 shows an embodiment in which m in Equation 1 is set to 4 (that is, the fundamental wave to the fourth harmonic are superimposed), so that the time-oscillation frequency characteristic at the terminal 8 is perfect. It does not become a straight line but becomes a solid line in FIG. However, when compared with the conventional waveform shown by the solid line in FIG.

Further, in the embodiment shown in FIG. 1, the circuit is constructed by setting m in Equation 1 to 4, but the present invention is not limited to this, and a band-pass filter and a variable By providing five or more attenuators and five or more variable phase shifters, it is possible to obtain an oscillation frequency of the VCO with more excellent linearity.

Further, according to the present invention, not only is it possible to obtain a sawtooth waveform oscillation frequency by a VCO using a variable capacitance diode, but also by adjusting an amplitude attenuation amount in a variable attenuator and a phase shift amount in a variable phase shifter. An arbitrary repetitive waveform frequency can be oscillated.

Further, in the embodiment shown in FIG. 1, the variable attenuators 31, 32, 33, 34 and the variable phase shifters 42,
Although 43 and 44 are used, the present invention is not limited to this, and may be an attenuator and a phase shifter having appropriate fixed amplitude attenuation and fixed phase shift, respectively.

[0024]

As described above, according to the present invention,
A voltage having a waveform that corrects the non-linearity of the control voltage-oscillation frequency characteristic of a voltage-controlled oscillator using a variable capacitance diode is generated by superimposing harmonics with appropriate amplitude and phase, and this voltage is applied to the voltage. Since the control voltage is applied as a control voltage to the control type oscillator, F is used to transmit the FM repetitive waveform by the voltage control type oscillator using the variable capacitance diode.
In the M high-frequency transmission device, the non-linearity of the modulation characteristic of the voltage controlled oscillator can be corrected.

[Brief description of the drawings]

FIG. 1 shows an FM in an FM radio frequency transmitting apparatus according to the present invention.
FIG. 3 is a block diagram of one embodiment of a modulation circuit.

FIG. 2 is a diagram illustrating a time characteristic of a voltage applied as a control voltage of the VCO illustrated in FIG. 1;

FIG. 3 is a diagram illustrating a time characteristic of an oscillation frequency which is an output of the VCO illustrated in FIG. 1;

FIG. 4 is a diagram showing a control voltage-oscillation frequency characteristic of a VCO.

FIG. 5 is a diagram showing a time-oscillation frequency characteristic when a voltage having a sawtooth waveform is applied as a control voltage of a VCO.

[Explanation of symbols]

 Reference Signs List 1 frequency multiplier 21, 22, 23, 24 bandpass filter 31, 32, 33, 34 variable attenuator 42, 43, 44 variable phase shifter 5 VCO 6, 7, 8 terminal

Claims (3)

(57) [Claims] A voltage-controlled oscillator that oscillates a frequency according to a control voltage using a variable capacitance diode;
An FM high-frequency transmitting apparatus for transmitting an FM modulated wave having an arbitrary repetitive waveform, wherein a sine wave having the same frequency as the fundamental frequency of the repetitive waveform is input, and the fundamental wave and the frequency of the sine wave are integers of the fundamental wave. A frequency multiplier that outputs a voltage having a frequency component of a double harmonic; a separating unit that separates a voltage output from the frequency multiplier for each frequency component; and a voltage divider for each frequency component from the separating unit. Attenuating means for attenuating the amplitude by a predetermined amount of attenuation, shifting means for shifting the phase of the voltage for each frequency component from the attenuating means by a predetermined amount of shifting, and Superimposing means for superimposing and outputting a voltage for each frequency component, and applying a voltage from the superimposing means as a control voltage to the voltage-controlled oscillator. Wave transmitting device. 2. The apparatus of claim 1, wherein said separating means comprises a plurality of bandpass filters, said attenuating means comprises a plurality of attenuators, and said shifting means comprises a plurality of phase shifters. FM high frequency transmitter. 3. The FM radio frequency transmission device according to claim 2, wherein the attenuator is a variable attenuator, and the phase shifter is a variable phase shifter.