JPH1132260A - Video signal transmission-reception system through fm radio wave - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a video signal transmission-reception system which uses FM radio waves for the transmission of video signals so as to narrow the frequency band. SOLUTION: A video signal transmission-reception system is composed of an FM radio wave video signal transmitter 1 which incorporates a video signal modulation circuit 3 which modulates the frequency of video signals, a primary oscillation circuit 4 which changes the oscillation frequency of the output signal of the circuit 3 by changing the voltage, so as to cause the output signal to make primary oscillation at a relatively high frequency, and a frequency dividing circuit 5 which obtains a desired output frequency and frequency deviation by dividing the output frequency of the circuit 4, and an FM wave video signal receiver 11 which incorporates an intermediate frequency circuit 15 converting the frequency of received radio waves into a constant intermediate frequency which is lower than the received frequency, and a demodulation circuit 16 which has a detecting characteristic suitable for the modulation of the output signal of the circuit 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a newly improved video signal transmitting and receiving system,
In particular, a frequency-modulated radio wave (hereinafter referred to as FM radio wave) which is less likely to be affected by noise and which can be expected to reach 10 times as long as an amplitude-modulated radio wave (hereinafter referred to as AM radio wave) with the same transmission output is used for video. The present invention relates to a video signal transmission / reception system using FM radio waves, which is intended to be used for signal transmission and requires a wide frequency band, which is a drawback of the frequency modulation method, and narrows the frequency band. .

[0002]

BACKGROUND ART As is well known, in the weak radio wave method, in terms of [do not require a license radio station], defines the following frequency 322MH _Z as weak radio waves. When transmitting a signal using frequency modulation using the feeble radio wave frequency specified by the feeble radio wave law, if an ideal high fidelity is desired, a frequency band about 10 times as large as the desired transmission signal is required. And The frequency band of the video signal is 4.
Since those requiring 5MH _Z, which to transmit a frequency modulated wave, it is necessary to frequency band 45MH _Z. In fact, satellite broadcasting in each country is, 36MH _Z, 24MH
_Z, has been employed as 17MH _Z. Satellite broadcasting is 12
Since a GH _Z (12000MH _Z), the channel and the band can also be freely set, there is no interference with other radio or air noise. It is said that FM radio waves are not easily affected by noise, and that the same transmission output can reach 10 times the reach of AM radio waves. Despite such advantageous characteristics, there is a disadvantage that a wide band is required as described above.

[0003] In particular, when an attempt is made to transmit and receive video by frequency modulation using the above-mentioned weak radio waves, for example,
The suppression phenomenon by interference and contamination with other radio even taking frequency bandwidth of ± 10 MHz _Z, were those it is difficult to obtain an excellent reception sensitivity.

[0004] From these facts, narrowband viewed from the receiver side, i.e., as long as it can transmit the characteristic of ± 3MH _Z about AM broadcast, filters for preventing contamination and mixing of noise other radio Is not so difficult to provide. Therefore, a problem is raised only on whether or not the transmitter can transmit a frequency-modulated video signal with a narrow band.

[0005] As shown in FIG. 5, in an ordinary frequency modulation type transmitter, the original oscillation circuit is operated at a low frequency.
The circuit obtains a shallow modulation signal, and by multiplying the signal, the degree of frequency shift is also multiplied. As shown in FIG. 5, a first multiplication circuit 23 and a second multiplication circuit 24 are connected to an original oscillation and modulation circuit 22 including a crystal 21, and a transmission output circuit 25 and a transmission antenna 26 are configured. In this way, if each of the multiplication circuits 23 and 24 is twice, the frequency shift is twice × 2 times the original oscillation and quadruples. Also, the original oscillation frequency is usually set to a frequency which is 1 / multiple of the desired transmission output frequency.

[0006] Therefore, in transmitting a video signal, the following method has succeeded as a method of narrowing the transmission frequency band on the transmitter side. 1. Focusing on a frequency dividing circuit for converting a frequency, for example, a method of using a prescaler integrated circuit usually used on a receiving circuit side for a transmitting circuit side to thereby perform frequency division. In the case of the converter system, only the frequency is converted, and the frequency deviation (deviation) remains unchanged. In the case of frequency division, both frequency and frequency shift are reduced at the same frequency division ratio. That is, the occupied bandwidth of the transmission radio wave is compressed. The division ratio is obtained by performing digital signal processing on an input signal once in the integrated circuit.

[0007]

In the present invention, contrary to the usual practice, the original oscillation is performed at a relatively high frequency, and by dividing this frequency, the desired maximum frequency shift, that is, the transmission radio wave is obtained. It is an object of the present invention to provide a video signal transmitting / receiving system using FM radio waves, which uses FM radio waves for video signal transmission and narrows the frequency band.

[0008]

In order to achieve the above object, the present invention specifically relates to a video signal transmitting / receiving system for transmitting a video signal using FM radio waves, wherein the original oscillation frequency is relatively low. An FM radio video signal transmitter that outputs at a high frequency, divides the relatively high frequency to obtain a desired frequency and a degree of deviation, and outputs a frequency-modulated video signal, and a demodulation of the FM radio video signal FM for receiving and demodulating by demodulation circuit with suitable detection characteristics
It comprises a radio video signal receiver and constitutes a video signal transmission / reception system using FM radio waves in which the frequency of the FM radio video signal is narrowed.

In the present invention, the FM radio wave video signal transmitter includes a video signal modulation circuit for frequency-modulating a video signal, and a voltage for causing an output signal from the video signal modulation circuit to oscillate at a relatively high frequency. And a frequency dividing circuit that divides an output frequency from the original oscillating circuit to obtain a desired output frequency and a degree of frequency shift. Radio wave video signal receiver, an intermediate frequency circuit that converts the frequency of the received radio wave to a constant intermediate frequency lower than the reception frequency, and a demodulation circuit having a detection characteristic suitable for demodulating an output signal from the intermediate frequency circuit. And a video signal transmitting / receiving system using FM radio waves.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a video signal transmitting / receiving system using FM radio waves according to the present invention will be described in detail based on a specific embodiment shown in the drawings. FIG. 1 shows a video signal transmission / reception system using FM radio waves according to the present invention. FIG. 1A is a block circuit diagram showing a specific circuit configuration example on the transmitter side, and FIG. FIG. 6 is a block circuit diagram showing a specific example of a circuit configuration on the side.

First, a specific example of a circuit configuration on the transmitter side in the video signal transmitting / receiving system using FM radio waves according to the present invention will be described in detail based on a block circuit diagram shown in FIG. 1A. According to a specific circuit configuration example on the transmitter side in the video signal transmission / reception system according to the present invention, the video signal transmitter 1 includes: a video signal modulation circuit 3 for frequency-modulating a video signal from a video camera 2; An original oscillation circuit 4 that changes the oscillation frequency by changing the voltage so that an output signal from the signal modulation circuit 3 oscillates at a relatively high frequency, and an output frequency from the original oscillation circuit 4 that A frequency dividing circuit 5 for obtaining an output frequency and a frequency deviation, a transmission output circuit 6, and a transmission antenna 7 are included.

According to the configuration of the video signal transmitter 1,
The original oscillation is performed at a relatively high frequency, and by dividing this frequency, a desired maximum frequency shift is obtained. Since the amount of change in capacitance with respect to the voltage of the varicap diode used for modulation is constant, when the frequency of the original oscillation increases, the change in frequency, that is, the frequency shift increases. For example, the original oscillation and 1.2GH _Z, and, VCO circuit oscillation circuit (Voltage Controlled Oscillator
circuit), modulate with a video signal, and
Frequency division to the 300MH _Z next, and, so that the occupied frequency bandwidth is compressed to 1/4.

The VCO circuit is a circuit that can change the oscillation frequency by changing the voltage for operating the oscillation circuit. The standard VCO circuit is shown in FIG.
It is as shown in. In the VCO circuit shown in FIG. 2A, when a signal voltage to be modulated is applied to the control voltage application terminal P, the frequency is modulated. However, the standard circuit shown in FIG. 2A includes a bypass capacitor CP. In this bypass capacitor CP, all high-frequency components of the video signal flow to the ground side, and the signal disappears.

Therefore, in the present invention, the VC shown in FIG.
The configuration is such that the bypass capacitor CP in the O circuit is removed and a signal is corrected by incorporating a choke CH as shown in FIG. 2B. In the FM transmitter according to the present invention, the frequency of the original oscillation is varied, and the circuit is slightly changed to perform modulation by a video signal.

[0015] In this way, by receiving and demodulating the transmitted signal (signal compressed to 1/4) by a circuit having a detection characteristic suitable for demodulating the signal, the frequency modulation video signal transmission band can be narrowed. Is achieved.

Next, an example of a specific circuit configuration on the receiver side in the video signal transmission / reception system using FM radio waves according to the present invention will be described in detail based on a block circuit diagram shown in FIG. 1B. According to the specific example of the circuit configuration on the receiver side in the video signal transmission / reception system according to the present invention, the video signal receiver 11 includes the receiving antenna 12
, A high-frequency amplifier circuit 13, a converter circuit 14,
The circuit includes an intermediate frequency circuit (IF circuit) 15 and a demodulation circuit 16.

According to the configuration of the video signal receiver 11, the said converter circuit 14, the input frequency of the 300MH _Z, for example, as low as 40MH _Z, and outputs the intermediate frequency circuit 15. The intermediate frequency circuit 15
Since the frequency is low, it is easy to narrowing of ± 3.0MH _Z, and also easily obtained high sensitivity. Normal, BS
Receiver intermediate frequency is of about 400MH _Z about as high.

Generally, regardless of amplitude modulation (AM) or frequency modulation (FM), if the modulation on the transmitting side is shallow, a sufficient demodulation output level cannot be obtained. Further, the characteristics of the demodulator itself are also important, and are designed in accordance with the modulation level on the transmission side. Even only frequency modulation, wideband FM transmission of the satellite broadcast video: from (the frequency band 36MH _Z, etc.) as PHS and data transmission narrowband (± 1.5K
_HZ ), and even if a demodulation circuit of the present invention uses a conventional demodulation circuit for video FM transmission, that is, a satellite broadcasting demodulation circuit, the demodulation circuit is narrowed (compressed). And cannot be demodulated.

Further, in a narrowband demodulation IC suitable for applications such as PHS, an overmodulated signal is generated, and only distortion is largely prevented from being used. Therefore, it is necessary to newly develop a demodulation circuit, and a quadrature detection circuit as shown in FIG. 3 is configured. In the present invention, the constants of each component in the quadrature detection circuit are determined and used as optimal values for the demodulation of the device of the present invention. The quadrature detection circuit has (1) linearity of demodulation, depending on the input frequency and debut (modulation depth) to the circuit.
Parts specifications must be designed to obtain characteristics such as (2) frequency characteristics, (3) S / N ratio, and (4) output magnitude.

On the other hand, an appropriate band-pass filter (BPF) used for the intermediate frequency circuit on the receiver side accompanying the band narrowing must be newly designed. FIG. 4 shows a specific circuit configuration of a band-pass filter as an intermediate frequency circuit on the receiver side in the frequency modulation video signal transmission / reception system according to the present invention.

[0021]

According to the above construction, F
The video signal transmission / reception system using M radio waves works effectively in that the occupied bandwidth can be compressed according to the frequency division ratio by dividing the transmission output to narrow the band.

Furthermore, in the video signal transmission and reception system according to FM radio waves becomes the present invention, the narrow band receiving circuit (generally suitable for demodulating compressed narrowed signal is ± 17MH _Z
While requiring more by are the ± 3.0MH _Z), suppression of the receiving sensitivity due to other radio wave, as well as to act very effectively even in that interference such as noise is reduced.

Further, in the video signal transmitting / receiving system using FM radio waves according to the present invention, the receiving sensitivity is improved by narrowing the band of the receiver, and the narrowing of the band of the receiver is improved.
It can be said that the present invention is also extremely effective in reducing reflection of radio waves during air transmission and phase disturbance of radio waves due to multipath and the like.

[Brief description of the drawings]

FIG. 1 shows a specific embodiment of a video signal transmission / reception system using FM radio waves according to the present invention. FIG. 1A is a block circuit showing a specific circuit configuration example on a transmitter side. FIG. 1B is a block circuit diagram showing a specific circuit configuration example on the receiver side.

FIG. 2 shows a VCO circuit as an original oscillation circuit in a configuration example on a transmitter side in a video signal transmission / reception system according to the present invention, and FIG. 2A shows a standard VCO circuit; FIG. 2 is a circuit diagram showing a circuit configuration example of FIG.
B is a circuit diagram showing a VCO circuit which is a preferred configuration example of the present invention.

FIG. 3 is a circuit diagram showing an example of a quadrature detection circuit configured as a new demodulation circuit in the configuration example on the receiver side in the video signal transmission / reception system according to the present invention.

FIG. 4 is a circuit diagram showing a specific circuit configuration of a band-pass filter as an intermediate frequency circuit on the receiver side in the video signal transmission / reception system using FM radio waves according to the present invention.

FIG. 5 shows an example of a conventional frequency modulation type transmitter in which an original oscillation circuit is operated at a low frequency, a shallow modulation signal is obtained by the circuit, and the signal is multiplied. FIG. 3 is a block circuit diagram illustrating an example of a configured transmitter.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 video signal transmitter 2 video camera 3 video signal modulation circuit 4 original oscillation circuit 5 divider circuit 6 transmission output circuit 7 transmission antenna 11 video signal receiver 12 reception antenna 13 high frequency amplification circuit 14 converter circuit 15 intermediate frequency circuit 16 demodulation circuit

Claims (2)

[Claims] 1. A video signal transmitting and receiving system for transmitting a video signal using FM radio waves, comprising: outputting an original oscillation frequency at a relatively high frequency; dividing the relatively high frequency to a desired frequency and polarization; An FM radio wave video signal transmitter for obtaining a mobility and outputting a frequency modulated video signal, and an FM radio wave video signal receiver for receiving and demodulating by a demodulation circuit having a detection characteristic suitable for demodulating the FM radio video signal. A video signal transmission / reception system using FM radio waves, wherein the frequency band of the FM radio wave video signal is narrowed. 2. An FM radio wave video signal transmitter, comprising: a video signal modulation circuit for frequency-modulating a video signal; and changing a voltage to cause an output signal from the video signal modulation circuit to oscillate at a relatively high frequency. And a frequency dividing circuit that divides an output frequency from the original oscillation circuit to obtain a desired output frequency and a degree of frequency deviation. The FM radio wave video signal A receiver including an intermediate frequency circuit that converts a frequency of a received radio wave into a constant intermediate frequency lower than a reception frequency; and a demodulation circuit having a detection characteristic suitable for demodulating an output signal from the intermediate frequency circuit. The video signal transmission / reception system using FM radio waves according to claim 1, comprising: