JPH04123527A - Fm or pm signal reception system - Google Patents

Abstract

PURPOSE:To improve a reception carrier versus noise ratio C/N of an FM signal itself and to improve the S/N of a demodulation output signal by adding an S/N enhancer employing a magnetostatic device to an FM receiver of an SHF band broadcast, for example. CONSTITUTION:A magnetostatic wave S/N enhancer acts like a level filter having a feature of a small insertion loss with respect to an input signal having a high level and a large insertion loss with respect to an input signal having a low level. When a level of the desired wave to be inputted is set to a level PH or over and a level of noise or a disturbing wave is set to a level PL or below, a ratio of the desired wave to the noise at the output side is improved by nearly a level Le. Then the S/N enhancer employing the magnetostatic device is introduced to a high frequency stage before a demodulator of the receiver so as to change the distribution of a noise spectrum before demodulation thereby reducing noise power in the vicinity of the desired wave. Thus, the C/N is improved and the S/N of the demodulation output signal is improved.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for improving the reception of FM or PM signals, and particularly relates to a method for improving the reception of FM or PM signals that can be processed in a high frequency stage before demodulation. It is something.

(Summary of the Invention) This invention relates to improving the reception of FM signals, such as satellite broadcasting, by introducing an S/N enhancer using a magnetostatic wave device into the high frequency stage before the FM signal demodulator. This makes it possible to improve the signal-to-noise ratio (C/N) and, in turn, the signal-to-noise ratio (S/N) of the demodulated output.

(Prior art) Conventionally, in order to improve the dark value of an FM signal, a narrow band filter is inserted into the high frequency transmission path to reduce the equivalent noise bandwidth, or a frequency locked loop (FLL) or a frequency locked loop (FLL) is used in the demodulator. Methods such as employing a feedback circuit such as a phase-locked loop (PLL) have been adopted.

(Problems to be Solved by the Invention) When the noise spectrum of the signal input to the FM receiver is uniform, the relationship between the received C/N and the S/N of the demodulated output signal is given by the following equation.

S/N = (3/2) (C/n0) (Δf”/fm
3)=(3/2) B (Δf”/fm') (C/N
) (1) Here, C: Input FM (word power (-) n
o: Noise spectrum of high frequency system (W/Hz) Δf: Maximum frequency deviation (H, □p) f i: Bandwidth of demodulated signal (Hz) B: Transmission bandwidth of high frequency system Δf, fffi and B are FM (It is a modulation specification of the transmission system and has a fixed value. Therefore, if 00 is a -like noise spectrum, the S/N of the demodulated output signal is as shown in the second term of equation (1). , is determined only by the relative value of C and 10, regardless of the transmission bandwidth B of the high frequency system, so even if a feedback demodulator is used, the S of the demodulated output signal at a high C/N above the threshold level is /N could not be improved any further.

On the other hand, there is a magnetostatic wave device used in the microwave band, and this device converts electromagnetic waves into magnetostatic waves with frequency-selective nonlinear amplitude limiting characteristics. If you use an N enhancer, you can reduce the noise near the desired signal by changing the no value or no distribution without changing the C value of the high-frequency signal input to the FM receiver. The inventor of the present application has focused on the possibility of improving this and, by extension, improving the S/N of the demodulated output signal.

For details of this magnetostatic S/N enhancer, please refer to "Microwave S/N Enhancer" and "Magnetic Static S/N Enhancer" filed on the same day as the present invention filed by the applicant.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an FM reception system that can improve the S/N of a demodulated output signal by applying the above-described magnetostatic S/N enhancer to the input high frequency section of an FM receiver.

(Means for Solving the Problems) In order to achieve this object, the FM reception system of the present invention uses a magnetostatic wave device having frequency-selective nonlinear amplitude limiting characteristics in a receiver that receives FM or PM signals. Introducing an S/N enhancer in the high frequency stage before the demodulator of the receiver to change the distribution of the noise spectrum before demodulation,
The present invention is characterized in that the C/N ratio is improved by reducing the noise power near the desired wave, and the S/N ratio of the demodulated output signal is further improved.

(Example) The main point of the present invention is to improve the reception C/N of the FM signal itself by adding an S/N enhancer using a magnetostatic wave device in front of an FM receiver for S-band broadcasting, for example. In this way, the S/N ratio of the demodulated output signal is improved.

Hereinafter, the present invention will be described in detail by way of examples with reference to the accompanying drawings.

FIG. 1 shows a schematic diagram of the basic configuration of a receiver according to the receiving system of the present invention.

It is assumed that the magnetostatic S/N enhancer 2 shown in FIG. 1 has input/output characteristics and spectrum characteristics shown in FIGS. 2 and 3 when not modulated. Note that the present invention does not specify the demodulation method within the FM receiver.

In the input/output characteristics of the magnetostatic S/N enhancer shown in the second diagram, the straight line 11 is the characteristic when there is no conversion from electromagnetic waves to magnetostatic waves, and the curve 12 shown in the figure is the characteristic of a typical magnetostatic S/N enhancer. Level PL is the minimum input signal level at which S/N improvement begins, and level P is the input level required to saturate the degree of improvement.

As is clear from the characteristics shown in the second diagram, the magnetostatic S/N enhancer is a level filter that has the characteristics of a small insertion loss for high-level input signals and a large insertion loss for low-level input signals. Since it works as
If the level of the input desired wave is set above the level P□ and the level of the noise or interference wave is set below the level PL, the ratio of the desired wave to the noise on the output side will be improved by approximately the level Le as shown in the figure. become.

However, as shown in Figure 3, noise components near high-level signals are difficult to attenuate, so strictly speaking, this enhancer is equivalent to changing the distribution of the noise spectrum, and the noise component near the desired signal This will reduce the

An S/N enhancer with such characteristics when no modulation is used is F.
If we follow the instantaneous frequency of the M signal and operate like a tracking filter as shown in Figure 4, the power of the noise near the desired wave will always be reduced, and considering the spectrum of the FM signal, As shown in Figure 5, the noise near the spectrum including the sideband of the desired signal is attenuated, so the C/N of the receiver input itself can be improved, and the S/N of the demodulated output signal can also be improved. .

(Effects of the Invention) As explained above, according to the receiving method of the present invention, noise power near the instantaneous frequency of an FM or PM signal can be reduced by using an S/N enhancer using a magnetostatic wave device. , to improve the C/N itself at the receiver input. Therefore, it is possible to simplify and reduce the cost of the receiver, and for example, it is possible to reduce the size of the receiving antenna for receiving satellite broadcasting.

Also, FM or P with a low C/N that is below the darkness value level.
Regarding the M signal, in particular, the "microwave S/N enhancer" and "magnetic wave S/N enhancer" filed on the same day as the present invention filed by the applicant
/N Enhancer J By using the S/N enhancer having the configuration described in J, more effective S/N enhancer of the demodulated output signal can be achieved.
/N improvement is possible.

[Brief explanation of drawings]

Fig. 1 shows the basic configuration diagram of the receiving system of the present invention, Figs. 2 and 3 show the input/output characteristics and its spectral characteristics of the magnetostatic S/N enhancer used in the invention, respectively, and Fig. 4 Similarly, Fig. 5 shows a spectrum diagram showing the tracking filter-like operation of the magnetostatic S/N enhancer that follows the instantaneous frequency of the FM signal, and Fig. 5 shows the input and output cass vector characteristics of the desired wave sideband of the magnetostatic S/N enhancer. show. 1...High frequency manual power 2...Magnetic wave S/N enhancer 3...FM receiver 4...Demodulation output 1st figure R11+ = FM to hear ＼,
Fig. 2 Enhanced TF input main direction Hayabusa medium raw input scale Fig. 3 Enhanced ridge cass vector characteristics (a) Input smoothness J and circumference 'J* (b) Muscle vector characteristics Figure 4 Transport/G't! 1 layer fI vY table sube'gutle ρ number of times

Claims (1)

[Claims] 1. In a receiver that receives FM or PM signals, an S/N enhancer using a magnetostatic wave device having frequency-selectively nonlinear amplitude limiting characteristics is introduced into the high frequency stage before the demodulator of the receiver, and FM or PM signal reception characterized by improving the C/N by changing the distribution of the noise spectrum and reducing the noise power near the desired signal, thereby improving the S/N of the demodulated output signal. method.