JPH02177628A - Fm transmission system and reception system for wide band signal - Google Patents

Abstract

PURPOSE:To attain the signal transmission having satisfactory S/N by executing the balanced modulation of a carrier, in which an FM modulation signal is orthogonal with the 2 channel signal of a narrow band, and making the noise of the narrow band, which is generated at the time of FM demodulation in a reception side, into the 2 channel. CONSTITUTION:A signal (a) is passed through a low-pass filter 1 of fp/2 and made into signals (b) and (c) of maximum frequency fp/2(>=fm/2). Then, the carriers of cos(omegapt/2) and sin(omegapt/2) are balanced and modulated. Then, the FM modulation is executed by a sum signal (d) of a real line and broken line. A pilot signal pcosomegapt is separated by an FM demodulator 13 and an oscillator 15 of a frequency fp is driven. After that, the carrier of cosomegapt is obtained and with this carrier as reference, the pulses of cos(omegapt/2) and sin(omegapt/2) are generated. Then, FM modulation wave switch is executed by the cos(omegapt/2) and sin(omegapt/2) and an FM modulated wave (g) is obtained. The pilot signal of pcosomegapt multiplexed to this signal (d) when it is switched by the pulse of the cos(omegapt/2) and sin(omegapt/2) goes to be 0 averagely after the FM demodulation. Thus, the noise is made half.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for converting video signals, audio signals, or data signals into F
The present invention relates to an FM transmission system for wideband signals when transmitting M-modulated signals and a reception system thereof.

[Summary of the Invention] A wideband signal consisting only of components in phase with respect to the frequency axis is generated using a pilot signal (frequency fp) whose frequency is somewhat higher than the highest frequency, cosω,1 = 1, cosω,t
= -1 and narrowed the signal with an f9/2 low-pass filter, each with cos
(ω, t /2) and sin (ωD t /2) are balanced and modulated into a composite signal.

A pilot signal p cosωp1 is added, FM-modulated, and transmitted (including recording). On the receiving side, an FM demodulator first extracts a pilot signal cosω9t, and a stable oscillator generates cos (ω, t /2) and sin (ω
, t/2), switch the FM modulation wave,
The original signal is obtained by FM demodulating and adding each FMg harmonic.

[Prior Art] When a video signal, audio signal, or data signal is FM modulated and transmitted, the receiving system performs FM demodulation to restore the baseband signal. In an FM demodulator, a small receive input is proportional to the baseband frequency. So-called triangular noise occurs.

If Fig. 6 is a baseband signal, the noise during FM demodulation is shown in Fig. 7.

[Problems to be Solved by the Invention] Therefore, there is a drawback that the noise of the high frequency component is large and the S/N ratio deteriorates as the band becomes wider.

[Objective of the Invention] The object of the present invention is to provide a system for transmitting wideband signals by FM modulation, reducing the noise associated with FM demodulation and improving the transmission signal.
An object of the present invention is to provide an FM transmission system and its reception method that make it possible to improve the S/N ratio.

[Means for Solving the Problems] In order to achieve the above object, the FM transmission system for wideband signals according to the present invention transmits a wideband signal consisting of components in phase with respect to the frequency axis at a frequency (fp) higher than its highest frequency.
The signals are distributed into a first path and a second path, and only a predetermined band of each distributed signal is passed through, and one is balanced modulated with the first trigonometric function signal, and the other is balanced modulated with the second trigonometric function signal. Then, a second pilot signal of a predetermined frequency is added to the combined signal, and further FM modulation is performed.

Further, the FM reception method for a wideband signal according to the present invention demodulates an input signal using FM, and generates a first trigonometric function signal and a second trigonometric function signal therefrom.

On the other hand, the gist is to distribute the input signal to two routes based on the first and second trigonometric function signals, perform FM demodulation on each, and then add them.

[Function] The FM modulation signal is a narrowband 2-channel signal that performs balanced modulation on orthogonal carrier waves, and the noise generated during FM demodulation on the receiving side is the narrowband 2-channel signal, so the total noise is less than the original signal. The noise is approximately 1/2, making it possible to transmit signals with a good S/N ratio.

[Example] The present invention will be explained in more detail using examples below with reference to one drawing, but these are merely illustrative, and various modifications and improvements can be made without going beyond the scope of the present invention. Of course it is possible.

FIG. 1 is a block diagram showing the configuration of a device for realizing the wideband signal FM transmission system and its reception system according to the present invention. In the figure, 1 is a low-pass filter (f, 11).
, 2 is an electronic switch, 3 is a fixed oscillator (f3), 4
, 5 is a low-pass filter, 6.7 is a balanced modulator, 8.2
1 is an adder circuit, 9°16.22 is a flip-flop, 10 is a 90" phase shift circuit, 11 is an FM modulator, 1
2 is the transmission system, 13, 19.20 is the FM demodulator.

14 represents a 2fp separation bandpass filter, 15 represents a phase-coupled oscillator, 17.18 represents an electronic switch or multiplier, and 23 represents an output signal.

The operation of the above embodiment will be explained below with reference to FIG.

(1) As shown in Fig. 6, the original signals of bands f and n are converted to T = using the pilot signal frequency fp≧fl.
Sample at 1/2fl) intervals.

(Figure 3 (a)) Figure 3 (a) (In Figure 3, the horizontal axis represents time, the vertical axis represents amplitude or frequency, and the pilot p
cos CIJ, l t are omitted. ), the solid line is cosω2t = 1, and the dashed line is −CoSω,t
= 1 sampling output.

(2) The signal of the solid line (or broken line) in Figure 3(a) is f
Through a p/2 low-pass filter, the highest frequency f
The signal is p/2 (≧ f, /2). (Figure 3(b)
, (c) )(3) The carrier waves of cos (ω, t /2) and sin (ωpt /2) are expressed as (b
) and (Q) for balanced modulation. The waveforms are shown by the solid line and broken line in FIG. 3(d).

(4) FM modulation is performed using the sum signal of the solid line and the broken line in FIG. 3 (, U).

(5) In the FM demodulation system, the FM demodulator 13 separates the pilot signal p cosωp1 and drives an oscillator with one frequency f2 to obtain a continuous wave of cosωp1 (yQ transmission wave), and based on this, cos (ωpt/2 ), sun (ω, t
/2) pulses are generated, as shown in FIGS. 3(e) and (f).

(6) cos (ω, t/2), sin (ωp
t, /2), the FM modulated wave (Fig. 3(d)) is switched (
(or multiplication) to obtain the FM of the solid and broken lines in Figure 3(g).
Obtain a modulated wave.

(7) FM modulate each of the signals shown in FIG. 3(g) and output the sum thereof. pCo5(11
1) The pilot signal at t is cos(ωpt/2
).

If switching is performed with a pulse of sin (ωpt/2), the average value will be O after FM demodulation.

In the FM transmission system, steps (1) and (2) result in a signal with a band of fp/2 (≧fm/2) (Figure 2 (a)).
). Therefore, the distribution of the orthogonal modulation signal of eos (ωpt /2) and 5in (ωpt /2) is as shown in Fig. 4, and fp /2
The frequency spread is ± f1/2.

Therefore, as for the noise of FM demodulation, there are two noises up to the bands f and u/2, as shown in FIG. 2(b). When this is adjusted to the normal time axis, the distribution shown in Fig. 2(c) is obtained, and the noise is reduced to 1/2 compared to the conventional method.

In Fig. 1, 1 is a low-pass filter (maXf+m) that limits the band of the input signal, and the electronic switch 2 is l/2
Distributes signals upward and downward for each fp.

The control signal is the output of the oscillator 3 at frequency ω. c.
The output of osωpt = 1 is connected to a low-pass filter 4, and the output of cosω,t = -1 is connected to a low-pass filter 5.
) to obtain the sample signal. Low pass filter 4.5
to make the bandwidth about fp/2.

Signals shown by broken lines in FIGS. 3(b) and 3(c) are obtained.

On the other hand, from cosω9t of the fixed oscillator 3, the flip-flop 9 and the 90' phase shift circuit 10 generate C05(ω, t
/2) and sin (ω, t /2) carrier waves are created. When the output of the fixed oscillator 3 -cosω,1 is used, a flip-flop output may be used instead of the 90° phase shift circuit 10. The balanced modulator 6°7 converts the original signal into
The band of e(t) is reduced to 1/2 e' (shi)
+ e ” (t).

e'(t)eos(ω, t/2) e''(t) sin(ωI, t/2) is obtained. Adder circuit 8 adds a pilot of pcosω9t to the sum of both.

e'(t)cos (ωpt/2) +e''(t)sin (ωpt/2)+pcos
ωpt.

This drives the FM modulator 11 to obtain an FM modulated wave. It reaches the receiver via the transmission system (including recording) 12. In the receiver, an FM demodulator 13 converts it into a baseband signal, and a pilot signal separation filter 14 converts it into a p co
Take out sω,1.

This drives the phase coupled oscillator (frequency fp) 15 to obtain stable cos ω2t (PLL may be used). Flip-flop with COS ωp1 and -COS ω,1 of the output of the oscillator 15 16.
22 to obtain cos (ωpt /2) and sin (ωpt /2). Flip-flop Electronic switch or multiplier with output of 16°22 17
18 to obtain the FM modulated wave shown in Fig. 3(g). Demodulate with FM demodulator 19.20 and e''(1)
and e II (t), and the output is added to the addition circuit 21
In addition to , we obtain the output signal e(t)23.

Figure 5 shows the state of switch pulse generation on the receiving side.
That is, cos ω2t in FIG. 5(a) and −co in opposite phase.
(b), (c) with flip-flop from sωp1
cos ((IJ p t /2) * sin (
If we create ωpt /2) and switch the FM modulation wave, we get the result shown in Figure 3 (g), but with cos(, Jpt
The phase of (c, +pt/2) cannot be determined uniquely, and the phases (d) and (e) are opposite, and -cos (ω, t/
2), −sin (ω, t/2) in some cases.

In this case, the output becomes as shown in FIG. 5(f), and has negative polarity.

Therefore, in this method, audio signals and data signals are
Suitable for transmitting information where polarity does not affect the final output, such as when transmitting with S.

[Effects of the Invention] As explained above, the present invention has the advantage that transmission and reception can be performed with less noise and a high S/N ratio.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a device for realizing the FM transmission system and reception system for wideband signals according to the present invention, FIG. 2 is a noise distribution diagram when the system according to the present invention is used, and FIG. Figure 1 shows the waveform diagrams of various parts of the device, Figure 4 shows the relationship between the original signal and the pilot signal, Figure 5 explains the generation of switching pulses from the pilot signal, and Figure 6 shows the baseband. FIG. 7 is a diagram of the frequency distribution of the signal and a diagram of the noise distribution during FM demodulation. 1...Low pass filter (f,), 2.
・・・・・・・・・Electronic switch, 3・・・・・・・・・
Fixed oscillator (f,), 4°5...Low pass filter, 6,7...Balanced modulator, 8
, 21...Addition circuit, 9, 16, 22...
・・・・・・Flip-flop, 10・・・・・・
...90° phase shift circuit, 11...FM
Modulator, 12...Transmission system, 13, 19.
20...FM demodulator, 14...
... 2f, separation bandpass filter, 15...
...Phase-shifted coupled oscillator, 17, 18...
・Electronic switch or multiplier, 23...
output signal. Patent applicant Clarion Co., Ltd.

Claims (2)

[Claims] (1) A wideband signal consisting of components in phase with respect to the frequency axis is distributed to the first path and the second path at a frequency (f_p) higher than its highest frequency, and only a predetermined band of each distributed signal is passed through. , one is balanced modulated with a first trigonometric function signal, the other is balanced modulated with a second trigonometric function signal, a second pilot signal of a predetermined frequency is added to the combined signal, and further FM modulation is performed. A characteristic FM transmission method for wideband signals. (2) FM demodulating the input signal and generating a first trigonometric function signal and a second trigonometric function signal therefrom; An FM reception method for a wideband signal, which is characterized in that the signals are divided into two, each of which is FM demodulated, and the signals are further added.