JPS58186230A - Ghost signal eliminating device of frequency modulation signal wave - Google Patents

Abstract

PURPOSE:To adjust automatically a ghost eliminating signal delivered from a holding circuit, by controlling the holding circuit of an FM intermediate frequency signal with a distorted level and the level detection output in an FM signal circuit for an FM relay broadcast device. CONSTITUTION:When an FM intermediate wave signal is supplied from an input 21 to a distributor 22, one output is subjected to phase adjustment via a phase circuit 23 and inputted to a synthesis circuit 24, the other output is amplified at an amplifier circuit 25 and a decoding signal C comprising a desired signal A and an unnecessary signal B is obtained from the output, and when the signal C is inputted to a holding circuit 26, the desired signal level A is controlled at a control circuit 30. Since the unnecessary signal delivered from the circuit 26 is inverted and applied to the synthesis circuit 24, the unnecessary signal is eliminated from a main signal as the output and outputted to an output terminal 28 via a distributor 27 and inputted to a distortion level detecting circuit 29, where the phase of the unnecessary signal and the level are detected, and the entire level of the output is detected at a level detecting circuit 31 to control the holding circuit 26 with a control circuit using the output of both the circuits 29 and 31.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a ghost signal removal device for frequency modulated signal waves used in FM signal circuits such as FM relay broadcasters, television broadcasters, and relay broadcasters.

[Technical background of the invention]

Generally, a relay broadcaster for FM broadcast waves or television broadcast waves receives radio waves emitted from a broadcasting device that serves as a master station.
It converts the frequency, amplifies it to the required level, and re-emits it as a radio wave. When such a radio wave is received by a receiver, the desired radio wave often becomes a composite radio wave because of the complicated propagation changes that occur in the radio wave propagation path. Composite radio waves are synthesized waves that are a combination of direct waves, reflected waves, and diffracted waves.

FIG. 1 is a propagation system diagram showing an overview of the generation of composite radio waves. In FIG. 1, reference numeral 11 indicates a transmitter, and reference numeral 12 indicates a receiver. In the reception @12, the desired radio wave EWI will be referred to as a direct wave, and the undesired radio wave reflected by the reflecting object 13 will be referred to as a reflected wave EW2. If the level relationship and phase relationship between the direct wave and the reflected wave are fixed, investigate the lumpiness and improve the receiving antenna for multiple receptions (
This problem has been addressed through improvements such as space dipersity, etc.) and correction circuits.

FIG. 2 shows an antenna improvement measure for dealing with complex waves. The antenna 15 at @l is a direct wave antenna, the antenna 16 at @2 is a reflected wave antenna, and the output of the reflected wave antenna 1- is transmitted through a phase shifter 17 and a novel adjuster i.
gt- to the combiner 19. In this combiner 19, the outputs of the first and second antennas 15, 16 are combined and output to the output end 20.

This device has a level of reflected waves between the output signal of the first antenna 15 and the output signal of the second antenna 16.
The phase is adjusted to a semi-fixed state, and the output of the reflected wave component is made zero by combining in the combiner 19. That is, as shown in FIG. 3(&)K, the 11 wave vector trunks) are synthesized by the direct wave vector (4) and the reflected wave vector (4). 1st, @2 antenna 1
The direct wave vector (4) and reflected wave vector (B) at 5°16 are expressed by K as shown in Figure 3 (b) (,).

The received signal of the second antenna 1c is corrected in gain and phase by a substantially constant amount, inverted, and applied to the combiner 19, so that vector combination as shown in FIG. 3(d) is performed.

[Problems with background technology]

However, according to the above means, when installed and operated, it is effective only when the set level and phase relationship between the direct wave and the reflected wave are established at the same time, and stable correction cannot be obtained at all times.

This is because radio waves are influenced by the season, weather, time, ionosphere changes, etc. on the propagation path, causing changes in transmission gain and transmission phase, and the level and phase relationship between direct waves and reflected waves is not always constant. It's for a reason. When such a composite signal is received and listened to, the quality of the sound is low due to deterioration of signal characteristics (sA decrease). Particularly when the signal is relayed multiple times using a relay broadcaster, the deterioration is significant, and the quality of the radio wave is subject to rapid deterioration. Furthermore, if the signal content sent by radio waves is based on audio multiplex broadcasting, the purpose of multiplexing will be lost. If the reflected wave becomes one or more radio waves, a problem arises in that a large number of antennas are required. In addition, the level and phase relationship of direct waves and reflected waves are automatically detected, and the antenna
It is conceivable to switch to phase a', but this would be expensive and not suitable for the actual situation.

[Purpose of the invention]

This invention was made in view of the above-mentioned circumstances, and it is possible to remove multiple frequency modulated signal waves whose levels and phase relationships occur in the wave propagation path. An object of the present invention is to provide a device for removing the Gose H signal from a modulated signal wave.

[Overview of the invention]

In this invention, as shown in FIG.
t provided, a level detection circuit 29, a level detection circuit 31,
A control signal for the holding circuit 26 is generated by the control circuit SO, and the cost removal signal of the holding circuit 2- is automatically adjusted.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 4 to 9.

The device shown in FIG. 4 is used in the intermediate frequency band of an FM relay broadcaster, and 21 is an input terminal to which an FM intermediate frequency signal is added, and the signal added here is input to a distributor 22. be done.

One output of this divider 22 is applied to one input terminal of a combining circuit 24 via a phase circuit 23.
The other output of 2 is amplified by an amplifier circuit 25 and supplied to a holding circuit 26 that suppresses the desired signal level. The output of this holding circuit 2- is applied to the other input terminal of the combining circuit 24. The output of this combining circuit 24 is applied to a distributor 21. One output of this distributor 21 is output terminal Z
J', and the second output is applied to a level detection circuit 31 that detects the overall level. Also, this distributor 2
The third output of 1 is applied to the distortion level detection circuit 29. This distortion level detection circuit 29 detects an unnecessary signal (lower level signal) due to reflected waves and obtains an output corresponding to the level. The outputs of the level detection circuit 31 and distortion level detection circuit 29 are applied to @1 and @2 input terminals of the control circuit 30.

This control circuit 30 controls the level of the holding circuit 250 in response to the output of the distortion level detection circuit 29. However, when the output of the level detection circuit 3 meets a certain condition, the output of the holding circuit 26 is fixed at a constant value.

One embodiment of the present invention is constructed as described above, and its effects will now be explained. The FM intermediate frequency signal derived from one output end of the distributor XX0 undergoes phase adjustment via the phase circuit 23 and is applied to the 10,000 input ends of the combining circuit 24. The FM intermediate frequency signal derived from the other output terminal of the distributor 22 is amplified by the amplifier circuit 2j and then sent to the holding circuit 26.
added to. This holding circuit 26 suppresses the desired signal level, and can amplify the lower level of the unwanted signal @total center. That is, the distributor 22,
The FM intermediate frequency signal outputted through the amplifier circuit 25 is a composite signal (C) of the desired signal (4) and the unnecessary signal (C) as shown in FIG. 5, and is input to the holding circuit 26. Then, the desired signal (4) level is suppressed as shown in FIG. 6(a). Since this holding circuit 2C has a function of changing the holding level, it can undergo changes as shown by the broken line in FIG. This is based on a control signal from the control circuit 30. The holding circuit 21 that received the V-pel system in this way
The output of i, the unnecessary signal 9, is applied to the synthesis circuit 24. In this case, a main signal as shown in FIG. 7(a)K is applied to the synthesis circuit z4 from the main line. and,
The output signal from the holding circuit 2σ is introduced with its phase inverted as shown in FIG. 7(b). In the output of the fed rice combining circuit 24, the unnecessary signal becomes zero and only the desired signal (mu4) is output as shown in FIG. 8fC. Furthermore, the output of this combining circuit 24 is passed through a distributor 27 to an output terminal 2J.
However, if this output contains an unnecessary signal, it is detected by the distortion level detection circuit 29. This distortion level detection circuit 29 performs phase detection on the intermediate #L value signal having a lower level, for example, and outputs the output from the loop i4.
It is derived through a filter and detects the phase and level of the construction cost threshold. The output of the distortion level detection circuit 29 is then applied to the 4-J control circuit 30, and is used as an element for determining the level in the holding circuit 26. Note that the distortion level detection times %29 can be carried out by other means, for example, by phase-detecting the desired signal and detecting the signal when it deviates from the figure-8 curve characteristic and leaves the so-called pull-in range.
! Alternatively, the level of this signal may be detected.

The 10,000 level detection circuit 31 detects the overall level of the output. This means that when the signals shown in FIG. 7 (1) are equal in opposite directions, and when the levels of the ghost signal due to the reflected wave and the desired signal due to the direct wave are equal, the output of the combining circuit 24 is is zero, so this is 11! This is an attempt to prevent I. This level detection circuit 31, control circuit 30, holding circuit 26, and synthesis circuit 2
The loop characteristics formed by 4 are as shown in Figure @9. In other words, the ratio between the desired signal (G) and the unnecessary signal (B) is expressed by the horizontal axis, the input or output terminal 2 of the level detection circuit 31.
When the output of # is shown on the vertical axis, the east line is the desired signal level due to the direct wave, and the broken line is the unwanted signal level due to the reflected wave. Therefore, the Lebel detection circuit 3 performs AM detection on the output to determine the output level. It is possible to detect whether or not the limit detection level (E+) is exceeded. If the output exceeds the detection level (El), this means that the level ratio between the desired signal and the unnecessary signal is large, and the distortion level detection circuit 2#'s loop! On the other hand, if the output is below the detection level 31, the level ratio between the desired signal and the unnecessary signal is small, and both are at the same level, so the output of the combining circuit 24 becomes zero. There is a danger. In such a case, even if an unnecessary signal is included, the output of the holding circuit 26 is stopped or fixed at a constant level so as not to perform variable compensation for the unnecessary signal.

Note that this invention is not limited to the above embodiments,
Not only FM relay broadcasters, but also telepino, n relay broadcasters,
It can be applied to FM receivers, telepianos, digital image reception, etc., and has a frequency of 1I14fI1. It can be used in all circuits with intervening circuits.

Further, in the case of a circuit in which different frequencies are mixed as input signals, the present device can be applied by providing a frequency selection circuit at a necessary location. For example, in the case of television broadcast waves, between the distributor 22 and the amplifier circuit 25,
Between the distributor 27 and the distortion level detection circuit 29, between the distributor 2r and the level detection circuit w! This is possible by providing an audio intermediate frequency selection filter between 31 and 31. Furthermore, the amplifier circuit 25 with Kt may be omitted, and the holding circuit 26 and the combining circuit 24
An amplifier circuit may be provided in between. An automatic gain control loop may be provided in the amplifier circuit 26, and the phase circuit 2J is for phase adjustment and is not necessarily provided between the distributor 22 and the combining circuit 24. Amplifying circuits may be provided at various locations, and output level compensation may be performed by providing a rounding compensation circuit subsequent to the synthesis circuit 24 for correcting a decrease in the output signal level.

As explained above, the present invention effectively suppresses ghost signal waves of frequency modulated signal waves whose level and phase relationship occur in a radio wave propagation path using extremely simple and lightweight means compared to conventional ones. It is an object of the present invention to provide a device for removing ghost signals from frequency modulated signal waves, which can remove ghost signals from frequency modulated signal waves, obtain high quality frequency modulated waves, and enable high quality signal demodulation.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the M point where composite radio waves occur, Figure 2
3(a) to 3(d) are signal vector diagrams shown to explain the operation of the device shown in FIG. Configuration i! showing one implementation of a signal wave ghost signal removal device! −
Figure 5 is a signal vector diagram due to a complex wave, Figure 6 (a
) 传) is a signal vector diagram showing the input signal and output signal of the holding circuit in Fig. 4, ＠Fig. 7 (, ｽ) is an input signal vector diagram of the combining circuit in Fig. 4 is an output signal vector diagram of the combining circuit, and FIG. 9 is a diagram showing an example of the dynamic characteristic due to the loop of the level detection circuit of FIG. 4. 22P2'l...Distributor, 23...Phase shift circuit, 24
... Synthesis circuit, 26 ... Holding circuit, 2g ... Gold level detection circuit, 30 ... Control circuit, 31 ... Level detection circuit. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 3 (a) (b) (C) (d),
4

Claims (1)

[Claims] It has a holding circuit which suppresses the desired remark level on the input side of the synthesis circuit and whose level is controlled by the 1tIII lil signal, and outputs a corresponding signal having an opposite phase to the signal on the input side of the synthesis circuit into the synthesis circuit. circuit means for supplying a predetermined frequency variable v; sg to the other input end of the synthesis circuit; a distortion level detection circuit that obtains an output according to the level; a control circuit that can derive a control signal '@ in response to the output of the distortion level detection circuit and control the level of the holding circuit; and a control circuit that can control the level of the holding circuit; A frequency carrier W4 signal wave that is equipped with a level detection circuit that detects the overall level of a predetermined frequency modulation signal on the output side and makes the level of the holding circuit constant when this level is below a predetermined level. boost signal removal device.