JPS6149858B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for compressing and transmitting the bandwidth of a modulated signal band.

An object of the present invention is to provide a novel bandwidth compression transmission method that has not been previously known.

The present invention includes a signal generator, a balanced modulator, a separator, and a transmitter as transmitting side devices, and a receiver, two balanced modulators, two 90°
゜It consists of a transmission system equipped with a phase shifter, a signal generator, and a synthesizer.

Hereinafter, one preferred embodiment of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. In the figure, reference number 14 indicates a transmitting device, and the transmitting device 14 has a modulated signal input terminal 1.
, a balanced modulator 2, a carrier wave (modulated wave) signal generator 3, a separator 4, and an FM modulation type transmitter 5
It is equipped with. Reference numeral 15 indicates a receiving device, and the receiving device 15 includes an FM receiver 6, a phase shifter 7, a balanced modulator 8, and a carrier wave (modulated wave) signal generator 9.
, a phase shifter 10, a balanced modulator 11, and a combiner 1
2 and a demodulation output terminal 13.

First, the principle and operation of the present invention will be explained with reference to the drawings.

When the bandwidth of the modulated signal is B _p and the lowest frequency is _L , the frequency _C of the carrier wave (modulated wave) signal generator 3 is determined by the following equation.

_C = _L +B _p /2 (1) Here, if the carrier wave (modulated wave) signal _e 1 of the signal generator 3 is balanced-modulated by the modulation signal a ₁ , the following equation is obtained.

e ₂ = EmE ₁ {cos(P−ω _C )t
+cos (P+ω _C )t} ...(2) However, a ₁ =EmcosPt ...(3) e ₁ =E ₁ cosω _c t ...(4). Here, Em and P represent the maximum amplitude value and angular frequency of the modulated signal a ₁ , and E ₁ and ω _C represent the maximum amplitude value and angular frequency of the carrier wave (modulated wave) signal, respectively. When the output e ₂ of the balanced modulator 2 is passed through the separator 4 to extract only the lower sideband component, e ₂ ′=EmE ₁ cos(P−ω _C )t ……(5), and the transmission band is It is sufficient if it is 0 to B _p /2.

When this signal e ₂ ' is transmitted through a transmission system and the phase of e ₂ ' is shifted by 90 degrees by a 90 degree phase shifter 7 on the demodulation side, the following equation is obtained.

e ₃ =EmE ₁ sin(P−ω _C )t (6) Next, the signals e ₂ ′ and e ₃ are each subjected to balanced modulation. At this time, if the output signal of the signal generator 9 is e ₄ and the output signal of the 90° phase shifter 10 is e ₅ as the carrier wave (modulated wave) signal, these signals e ₄ and e ₅ are expressed by the following equation. It can be done.

e ₄ = E ₁ cosω _C t (= e ₁ ) ...(7) e ₅ = E ₁ cos (ω _C t + π/2) = E ₁ sinω _C t ... (8) Therefore, the balance modulator 8 Assuming that the output is e ₆ and the output of the balanced modulator 11 is e ₇ , the outputs are expressed by the following equation.

e ₆ =2E ₁ e ₂ ′cosω _C t=EmE ² ₁ {cos(ω _C −P+ω _C )t +cos(ω _C +P−ω _C )t} ……(9) e ₇ =2E ₁ e ₃ sinω _c t=EmE ² ₁ {cos(ω _C −P+ω _C )t −cos(ω _C +P−ω _C )t} ...(10) Furthermore, when these signals are added in phase by the synthesizer 12, the synthesizer The output e ₃ of 12 becomes a signal expressed by the following equation.

e ₈ =e ₆ −e ₇ =2EmE ² ₁ cos(ω _C +P−ω _C )t = 2EmE ² ₁ cosPt (11) Next, an embodiment of the present invention will be described with reference to the drawings.

The drawing shows an embodiment of a system according to the present invention in which a modulated signal bandwidth B _P is FM modulated with approximately 1/2 the bandwidth and transmitted over a wireless line. In the figure, one embodiment of the present invention includes a balanced modulator 2, a carrier wave (modulated wave) signal generator 3, a separator 4,
A transmitter 14 consisting of an FM modulation transmitter 5, an FM receiver 6, 90° phase shifters 7, 10, balanced modulators 8, 11, a combiner 12, and a carrier wave (modulated wave) signal generator. and a receiving device 15 constituted by a receiver 9.

Modulated input signal _a1 is input from input terminal 1,
The carrier wave (modulated wave) signal _a1 , which is the output of the carrier wave signal generator 3 at a frequency of _C = B _P /2 + _L ( _L : the lowest frequency of the modulated signal), is balanced-modulated by the balanced modulator 2, and the upper side wave and The lower side wave is output. At this time,
The lower sideband e ₂ ′ is given by the modulated signal bandwidth B _P
It becomes 1/2 and is taken out by separator 4. The signal e ₂ ' is wirelessly transmitted by a transmitter 5 with an FM modulator.

The wirelessly transmitted lower sideband signal e ₂ ' is demodulated by the FM receiver 6 of the receiving device 15. A part of the demodulated output is phase-shifted by a 90° phase shifter 7, and the signal is obtained by shifting the carrier (modulated wave) signal output of the frequency _C output from the carrier signal generator 9 by 90°. The phase shifter 10 performs balanced modulation on the phase-shifted signal. On the other hand, a part of the demodulated output is balanced-modulated by the balanced modulator 8 on the output (carrier wave, that is, the modulated signal) of the carrier signal generator 9 . The balanced modulator 8 outputs a lower side wave+upper side wave component, and the balanced modulator 11 outputs a lower side wave−upper side wave component. Therefore, when the two output signals are added in opposite phases by the combiner 12, the lower sideband component, that is, the modulation signal, is demodulated at the output terminal 13 of the combiner 12. The detailed formula principle is as described above.

As described above, according to the present invention, it is possible to perform transmission while compressing the used bandwidth.

Next, to explain this embodiment using a specific numerical example, when transmitting FM using arbitrary radio frequencies for telephone channel 1 with a modulation frequency of 0.3 to 3.4 KHz and telephone channel 2 with a modulation frequency of 4.3 to 7.4 KHz, the required bandwidth is Width = 2 x {maximum modulation frequency + maximum frequency deviation (D =
}, 14.8KHz + 2D is required, but in this example, the highest modulation frequency is (7.4KHz).
-0.3)/2=3.55KHz, so the required bandwidth is
It will be 7.1KHz + 2D, which means that the band will be compressed by about 1/2 compared to the original transmission method.

As described above, by configuring the present invention as shown in the attached drawings, the bandwidth is compressed and high-density multiplex transmission is possible. Particularly, in FM modulation transmission, it is effective in improving S/Z.

[Brief explanation of the drawing]

The drawing is a schematic system diagram showing one embodiment of the present invention. 1... Modulation signal input terminal, 2, 8, 11... Balanced modulator, 3, 9... Carrier wave signal generator, 4... Separator,
5...FM modulation transmitter, 6...FM receiver,
7, 10... 90° phase shifter, 12... Combiner, 13... Demodulation output terminal, 14... Transmitting device, 15... Receiving device.

Claims (1)

[Claims] 1. A signal generator A that generates a modulated signal having a frequency that is approximately 1/2 of the bandwidth of the modulated signal, a balanced modulator B that balancedly modulates the modulated signal with the modulated signal, and the balanced modulation. A transmission system comprising a separator that extracts a lower sideband component from the output of the device B, a transmitter that transmits the output of the separator, a receiver that receives the output of the transmitter, and a receiver that receives the modulated signal. a signal generator C that generates a modulated signal of the same frequency;
a balanced modulator D that balancedly modulates the output signal of the signal generator C with the output signal of the receiver; a 90° phase shifter E that shifts the phase of the received output signal by 90°;
a 90° phase shifter F that shifts the phase of the output signal of the signal generator C by 90°; and a balance that modulates the output signal of the 90° phase shifter E with the output signal of the 90° phase shifter F. It has a receiving system including a modulator G and a combiner that combines the output of the balanced modulator G and the output of the balanced modulator D, and is compressed to approximately 1/2 of the modulation signal band in practical use. A band compression transmission system comprising a transmission system for transmitting and receiving signals, and a demodulated signal is extracted by the synthesizer.