JP2948386B2 - Demodulator and receiver using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a demodulator for demodulating an amplitude-modulated signal under a level fluctuation due to fading or the like, a receiver using the demodulator, or a method in which one carrier is angle-modulated by two kinds of information. The present invention relates to a demodulation device that receives a signal obtained by amplitude modulation (hereinafter, a multiplex modulation signal), separates and demodulates the signal, and obtains the two types of information, and a receiver using the same.

[0002]

2. Description of the Related Art For example, in a road-to-vehicle information system, an automobile technology Vol. 43, no. 2 (1989), page 6, a road-vehicle information signal obtained by performing AM modulation with information for detecting a position and a direction and simultaneously performing PSK modulation with various information at the position is used. When this road-to-vehicle information signal is received by the on-vehicle receiver, it is required to perform AM demodulation after receiving the signal under complicated fading. Also, the multiplex modulated PS
It is necessary to separate and demodulate the K · AM modulated signal to obtain each information.

In general, an AM receiver is well known as an amplitude modulation receiver, and an FM receiver is well known as an angle modulation receiver. When simultaneously receiving and demodulating an angle / amplitude modulated signal, a conventional FM receiver and an AM
A configuration in which each receiver is operated and demodulated is considered.

[0004]

In an on-vehicle receiver, the level of an input signal may fluctuate greatly due to fading during traveling. However, when a general AM receiver is used as the on-vehicle receiver, the input signal level is reduced. , The level of the output signal greatly changes in accordance with the level of the input signal.

FIG. 14 is a waveform diagram showing waveforms of an input signal and an output signal of an AM detector in a general AM receiver.
In FIG. 14, (a) shows the waveform when normal, and (b) shows the waveform when affected by fading. The left waveform is the waveform of the input signal, and the right waveform is the waveform of the output signal. .

When the level of the input signal of the AM detector is doubled, for example, from the state shown on the left side of FIG. 1A to the state shown on the left side of FIG. , The level of the output signal of the AM detector also doubles from the state shown on the right side of FIG. 2A to the state shown on the right side of FIG. 2B, and is greatly affected by fading. was there.

In a general AM receiver, an automatic gain control amplifier (hereinafter, an AGC amplifier) for removing a level fluctuation of an input signal and keeping it constant so that the level of the input signal falls within a dynamic range. There is). The time constant of the AGC amplifier is usually selected so as to follow only low-speed level fluctuations in order to accurately demodulate the AM modulation signal. For this reason, when the level fluctuation due to fading during traveling is a high-speed level fluctuation close to the frequency of the AM modulation signal, the AGC amplifier cannot accurately follow the level fluctuation. Therefore, since the high-speed level fluctuation as described above is not removed, the level of the input signal may exceed the dynamic range, and in such a case, non-linear distortion is generated in the demodulated output. There was a problem.

In the case where a conventional FM receiver and AM receiver are operated to receive an angle / amplitude modulated signal and separate and demodulate the signal, there are the following problems.

That is, the AGC in the AM receiver
When a signal from the amplifying unit is input to the limiter amplifier in the FM receiver, if the level of the input signal suddenly drops due to fading during traveling, such a high-speed level change includes the AGC amplification as described above. Since the unit cannot accurately follow, the level fluctuation is not removed, and therefore, the level of the signal input from the AGC amplifier to the limiter amplifier remains low for a while. As a result, the level of the input signal of the limiter amplifier may be lower than the limiter level.In such a case, the limiter amplifier cannot remove the amplitude change such as the amplitude modulation component, which is generated as noise in the demodulation output of the angle modulation. Then, there was a problem that accurate demodulation could not be performed.

Further, even if there is a slight inclination in the frequency characteristic of the signal path relating to the demodulation of the amplitude-modulated signal, the angle-modulated component is AM-demodulated and appears as an interference with the demodulated output of the AM receiver. . For example, as shown in FIG. 15, if the frequency characteristic of the signal path has a slope, the angle modulation component ± Δ
f is AM-demodulated, and the error component ΔA becomes a disturbance signal of the demodulated output of the AM receiver.

An object of the present invention is to eliminate the above-mentioned problems of the prior art, to minimize the deterioration of the AM demodulation output and the angle modulation demodulation output due to fading and the like, and to flatten the frequency characteristics of the signal path. And a receiver using the same.

[0012]

In order to achieve the above-mentioned object, according to the present invention, when demodulating an amplitude-modulated signal from a modulated wave, the modulated wave is input, amplified, and output. An AGC amplification unit whose gain is controlled in accordance with a separately input control signal, and a modulated wave input from the AGC amplification unit, which detects and outputs an amplitude change of the modulated wave.
An MGC detector, an output signal from the AM detector, an AGC signal generator for generating and outputting an AGC signal from the output signal, and an AGC signal from the AGC signal generator; A DC cutoff unit that cuts off a DC component in a signal and outputs the signal as the control signal, and an AGC signal output from the AGC signal generation unit or the DC cutoff unit,
Filtering means for filtering the amplitude modulated signal from the AGC signal and outputting the filtered signal as a demodulated output.

In the case where the angle modulated signal and the amplitude modulated signal are separated and demodulated from the modulated wave obtained by the angle / amplitude modulation, the modulated wave from the AGC amplifying unit is further input to the above-mentioned configuration, An angle modulation demodulation unit for demodulating the angle modulation signal from the modulated wave and outputting the demodulated signal as a demodulated output is provided.

[0014]

By using the above configuration, a high-speed AC negative feedback loop is formed between the AGC amplifier, the AM detector, and the AGC signal generator, and the input level of the AM detector is suppressed by suppressing the fluctuation of the input level. Almost constant. The control signal of the AGC amplifier generates a signal in which an accurate amplitude modulation signal and a voltage corresponding to the level fluctuation due to fading are superimposed, and if the amplitude modulation signal is selected by a filtering means such as a bandpass filter, the fading occurs. , An amplitude-modulated signal which is not affected by level fluctuations can be taken out.

Here, the AG generated from the output of the AM detector is
The C signal includes a DC component, and when the AGC amplifier is controlled by the AGC signal including the DC component, the operating point of the AGC amplifier is determined by the input level of the AGC amplifier. It is difficult to set the operating point to a point having good linearity of the AGC amplifier or a point having a wide control range. Further, even if the input level is constant, it is difficult to uniquely determine the operating point due to the deviation of each element.

Therefore, by cutting off the DC component of the control signal of the high-speed operation AGC amplifying unit, negatively controlling the AGC amplifying unit in an AC negative feedback manner and arbitrarily setting the static operating point of the AGC amplifying unit. Excellent points such as linearity of amplifier, wide control range and noise resistance can be selected as operating points, demodulation operation can always be performed stably against fading level fluctuation, and deviation of the characteristics of the whole system Can be reduced.

In addition, for a gradual change in the input level, an additional AGC amplifying unit is connected to an AGC amplifier including a DC component.
By performing the negative feedback control with the signal,
The C amplifier can be stably controlled by the AC component of the AGC signal.

Further, when the angle modulated signal and the amplitude modulated signal are separated and demodulated from the modulated wave obtained by the angle / amplitude modulation, the AGC signal generation is performed by a negative feedback loop between the AGC amplifier and the AGC signal generator. The input level of the section becomes substantially constant, and it is possible to suppress the interference to the angle modulation component generated due to the inclination of the frequency characteristic of the signal path related to the AM detection.

The interference of the amplitude modulation demodulation output corresponding to the amplitude fluctuation is suppressed by the limiter amplifier in the angle modulation demodulation unit. However, when the gain of the limiter amplifier is not sufficient for the level change due to fading, the angle modulation demodulation output is suppressed. Interference due to the amplitude modulation component appears. According to the present invention, the input of the AM detection unit is an amplitude modulation signal and an angle modulation signal of almost constant amplitude in which level fluctuation due to fading is suppressed, so that it is not necessary to increase the gain of the limiter amplifier so much. This has the effect of reducing dependence on the limiter amplifier.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. In the following embodiment, AM is used as the amplitude modulation.
A description will be given of a case where is used. The angle modulation described later includes FM, PSK, FSK, MSK, and GMS.
K is known, but since angle modulation involves a frequency shift, the case of using FM will be described as a representative.

Next, as an embodiment of the present invention, a demodulator for demodulating an AM modulated signal from an AM modulated wave and a receiver using the same will be described. FIG. 1 is a block diagram showing a demodulation device as a first embodiment of the present invention. In FIG. 1, 1 is an AM modulated wave input terminal, 2 is an AM demodulated signal output terminal, 10 is an AGC amplifier, 20 is an AM detector, 30
Is a capacitor for cutting off the DC component and controlling the AGC amplifying section 10 in an AC manner, 40 is an AGC signal generating section, 41 is an inverting amplifier having a high gain, 50 is a BPF (passband in the frequency band of the AM modulation signal). Band pass filter),
It is.

It is assumed that an AM modulated wave whose level varies variously due to fading is input to an input terminal 1. The AM modulated wave is transmitted through the AGC amplifier 10 to the AM modulated wave.
The signal is input to the detection unit 20, where it is subjected to AM detection. A composite waveform of an AM demodulation component and a level fluctuation component due to fading is output to the output of the AM detection unit 20. The output of the AM detector 20 is output to the inverting amplifier 4 of the AGC signal generator 40.
The AGC signal is generated by being amplified by 1.

The AGC signal contains a DC component, and the DC component changes due to the deviation of each element. For example, if the AGC amplifier 10 is controlled using the AGC signal as it is as a control voltage, the AGC amplification The static operating point of the unit 10 changes, and the static operating point cannot be uniquely determined.

Therefore, the DC component of the AGC signal is cut off by the capacitor 30 and input to the AGC amplifier 10 as a control voltage, whereby the static operating point of the AGC amplifier 10 can be arbitrarily set. That is, AGC
By selecting an advantageous operating point in various characteristics such as the linearity of the gain-control voltage characteristic and the wide dynamic range in the amplifying unit 10, it is possible to easily realize the setting suitable for the system to be applied.

The above operation point will be described in detail with reference to FIG. FIG. 2 shows the gain of the AGC amplifier 10 in FIG.
FIG. 4 is a characteristic diagram illustrating an example of a control voltage characteristic. Now, FIG.
Is a static operating point, the input signal changes and instantaneously
When the gain increases by 0 dB, the control voltage of the AGC amplifying unit 10 instantaneously becomes a voltage that reduces the gain by 10 dB. I will. The case where the static operating point is set to c in FIG. 2 is the reverse of the case of a, but similarly, the demodulated output is distorted.

Therefore, in order to provide the same level of dynamic range with respect to the level fluctuation of the input signal and to enable good reception, it is easy to set the point b in FIG. 2 as a static operating point. Guessed. However, AGC amplification unit 1
Since the operating point of 0 is determined by the level of the input signal, it greatly changes according to the level of the input signal. Moreover, since there is a gain deviation of each element constituting the demodulation device, etc., FIG.
It is generally difficult to set b in FIG.

However, in this embodiment, as described above,
The static operating point can be arbitrarily set by cutting off the DC component of the AGC signal and setting the control voltage. Since the AGC amplifier 10 is negatively feedback-controlled in an alternating manner by the AGC signal in this manner, the output of the AGC amplifier 10 is a signal of almost constant amplitude with little level fluctuation.

On the other hand, the AGC signal whose DC component has been cut off by the capacitor 30 is input to a BPF 50 having a pass band in the frequency band of the AM modulation signal, and a level fluctuation component due to fading is removed therefrom, thereby enabling a necessary AM modulation. A signal can be obtained. At this time, BPF5
Since a high Q filter can be used for 0,
Disturbance due to fading can be largely removed.

Next, the operation of this embodiment will be described more specifically with reference to FIG. FIG. 3 is a waveform diagram for explaining the operation of the demodulation device of FIG. To simplify the explanation, the AM modulated wave input to the input terminal 1 is shown in FIG.
It is assumed that the signal includes a sine wave AM modulation signal having a frequency of 1 kHz as shown in FIG. 3A and a level fluctuation which fluctuates sinusoidally at a frequency of 500 Hz as shown in FIG. 3B due to fading. Therefore, the AM modulated wave is shown in FIG.
The waveform is as shown in FIG.

As described above, the AM modulated wave input to the input terminal 1 is input to the AM detection unit 20 via the AGC amplification unit 10 and is subjected to AM detection there. The AGC signal is generated by being amplified by the inverting amplifier 41. Therefore, this AGC
The signal is a signal obtained by inverting a composite signal of the 1 kHz AM modulation signal shown in FIG. 3A and the 500 Hz level fluctuation due to fading shown in FIG. 3B.

The DC component of the AGC signal is cut off by the capacitor 30 and input to the AGC amplifier 10.
Therefore, since the AGC amplifier 10 is negatively feedback-controlled in an alternating manner by the AGC signal, the AM modulated wave is transmitted from the AGC amplifier 10 to the AGC amplifier 10 as shown in FIGS.
As shown in (1), the carrier signal has a substantially constant amplitude with little level fluctuation. Also, by inputting the above-mentioned AGC signal to the BPF 50 including 1 kHz in a pass band, an accurate AM demodulated signal can be obtained from the output.

According to the present embodiment, the AGC amplifier 10, A
The AGC loop composed of the M detector 20 and the inverting amplifier 41 can operate at high speed, can efficiently remove the level fluctuation component due to fading, and has an AC negative feedback. Since it has excellent linearity and is used at an operating point in a wide control range, it can stably cope with a large level fluctuation.

In the conventional AM demodulator, the following problem occurs, but this embodiment can solve it. That is, in the conventional demodulator, when performing accurate demodulation, an LPF (low-pass filter) having a high Q such that the signal passes 500 Hz which is the frequency of the level fluctuation due to fading and blocks 1 kHz which is the frequency of the AM modulation signal. ) Must be inserted into the AGC loop, but if such a high-Q filter is inserted into the AGC loop which is a feedback loop, the operation becomes unstable.

Therefore, in order to operate stably, it is conceivable to lower the Q of the above-mentioned LPF. However, in such a case, the effect of fading cannot be completely removed by the AGC amplifying section, and the input to the AM detecting section can be reduced. Since the signal level greatly changes, the detection output of 1 kHz changes in amplitude in accordance with fading. Even if the signal passes through a BPF including 1 kHz in the pass band, the output changes in amplitude at a frequency of 500 Hz, and accurate demodulation cannot be performed. In addition, since the input to the AM detector changes greatly with fading, it is necessary to greatly improve the noise resistance of the demodulator and the dynamic range of detection of the AM detector, which is not practical.

However, according to the present embodiment, the AM detector 2
Since the input of 0 is set to a substantially constant amplitude, accurate detection can be performed even in a system in which the dynamic range of detection of the AM detection unit 20 is narrow. In this detection output, since a level fluctuation due to fading is also detected in addition to the AM modulation signal, it is necessary to filter the AM modulation signal by the BPF 50. However, since a high Q filter can be used for the BPF 50, the fading is Interference caused by level fluctuation can be largely suppressed.

FIG. 4 is a block diagram showing a demodulator according to a second embodiment of the present invention. In FIG. 4, 60 is A
An LPF having a cutoff frequency higher than that of the M-modulated signal, and other components having the same reference numerals as those in FIG. 1 indicate the same or equivalent components.
Hereinafter, points different from the first embodiment will be described.

In the first embodiment, if the AGC signal contains high-frequency noise, the AGC loop may be unstable. However, in this embodiment,
Since high frequency noise can be suppressed by the LPF 60, the operation of the AGC loop can be operated at high speed and stably.

FIG. 5 is a block diagram showing a demodulator according to a third embodiment of the present invention. In FIG. 5, 70 is A
The GC amplifying unit 42 is an LPF having a cutoff frequency lower than the frequency of the AM modulation signal, and other components having the same reference numerals as those in FIGS. 1 and 4 indicate the same or equivalent components. Hereinafter, points different from the first and second embodiments will be described.

When the signal is received by the on-vehicle receiver, the reception power also changes due to a change in the distance from the transmitting station or a change in various conditions. Therefore, in this embodiment, the AGC amplifier 70 is provided before the AGC amplifier 10 and the AGC amplifier 7
By controlling 0 with an AGC signal that also includes a DC component, this change in power can be absorbed.

At this time, by setting the cutoff number wave number of the LPF 42 for determining the time constant lower than the frequency of the AM modulation signal, the AM modulation signal component in the AM modulated wave input to the AGC amplifier 10 is changed. Without this, it is possible to absorb low-speed amplitude fluctuations such as a part of fading having a lower frequency than the AM modulation signal and a slow level fluctuation due to a change in distance from the transmitting station. The AM modulated wave becomes a signal in which the influence of fading is suppressed as compared with the case of the first and second embodiments, and more excellent demodulation can be performed.

FIG. 6 is a block diagram showing a demodulator as a fourth embodiment of the present invention. In FIG. 6, 90, 10
0 is an AGC amplifier, 80 is a capacitor for cutting off the DC component of the AGC signal and controlling the AGC amplifier 100 in an AC manner, 43 is an LPF having a cutoff frequency lower than the frequency of the AM modulation signal. 1 and 4 and 5 indicate the same or equivalent. Hereinafter, differences from the first, second, and third embodiments will be described.

In this embodiment, the AGC amplifying unit 90
It is controlled by an AGC signal including a DC component via the LPF 43 having a cutoff frequency lower than the frequency of the modulation signal. Therefore, among the level fluctuations of the AM modulated wave input from the input terminal 1, the AGC amplification section 90 absorbs a fluctuation of a frequency lower than the cutoff frequency of the LPF 43, and outputs a more stable AM modulated wave. .

Therefore, in this embodiment, an AGC amplifier controlled by an AGC signal containing a DC component at a lower frequency than the AM modulation signal as described above is further added appropriately, so that the AM modulated wave can be reduced. Level fluctuation can be made more stable.

In this embodiment, the first, second, and third
Instead of the demodulation by the high-speed AGC loop using only the AGC amplifier 10 as in the embodiment of the present invention, the change of the gain of the AGC amplifier with respect to the change of the AGC signal is reduced by adding the AGC amplifier 100 of high-speed response. I'm making it big. That is, the dynamic range of demodulation for the level fluctuation of the input signal by the AGC amplifiers 100 and 10, the AM detector 20, and the AGC signal generator 40 is expanded.
For this reason, it is possible to cope with a level fluctuation due to fading larger than in the first, second and third embodiments.

Accordingly, in the present embodiment, the dynamic range can be further expanded by adding an AGC amplifier controlled by an AGC signal having substantially the same frequency as the frequency of the AM modulation signal as described above. Can be.

Since the AGC amplifier 100 is controlled by the AGC signal from which the DC component has been removed, an arbitrary operating point is set as described in the first embodiment as a control method of the AGC amplifier 10. And stable control can be performed.

In this embodiment, the case where separate capacitors 30 and 80 are used as means for cutting off the DC component of the AGC signal has been described. However, the output of the capacitor 30 is used to control the AGC amplifier 100. Obviously, the same effect can be obtained even if the above-mentioned conditions are satisfied.

In this embodiment, the LPF 42 and the LPF 43 are used as LPFs for passing the low frequency components of the AGC signal.
However, when the LPF 42 and the LPF 43 are the same LPF, the output of the LPF 42 is
It is clear that the same effect can be obtained even if the GC amplification section 90 is controlled.

FIG. 7 is a block diagram showing a demodulation device as a fifth embodiment of the present invention. In FIG. 7, 110 is A
A GC amplification unit, 120 is a local oscillator, 130 is a frequency conversion unit, and the same reference numerals as those in FIGS. 1, 4, 5, and 6 denote the same or equivalent components. The following is the first
The differences from the fourth embodiment will be described.

The AM modulated wave supplied to the input terminal 1 is
The signal is supplied to the AGC amplifier 110 controlled by the AGC signal from the AGC signal generator 40, and is amplified or attenuated. The output of the AGC amplifier 110 is the local oscillator 120
After being frequency-converted by the frequency conversion unit 130 using the output of the AGC signal, the signal is supplied to the AGC amplification unit 70 controlled by the AGC signal from the AGC signal generation unit 40, and is amplified or attenuated. The output of the AGC amplifier 70 is
Supplied to

Here, the AGC amplifier 110 and the AGC amplifier 70 have low-frequency amplitudes, such as a low-frequency amplitude lower than the AM modulation signal, and a slow level fluctuation such as a slow level change due to a part of fading or a change in the distance from the transmitting station. It has a similar function in that it absorbs fluctuations, but the carrier frequencies of the signals to be amplified are different from each other.

Therefore, in the present embodiment, even when frequency conversion is performed, the same effects as those of the above-described embodiments can be obtained, that is, the present embodiment can be made independent of the carrier frequency.

In the above first to fifth embodiments, AM modulation has been described as an example of amplitude modulation, and the case of demodulating the signal has been described. However, the present invention is not limited to the demodulation of the AM modulation signal. By using a means for demodulating other amplitude modulations in place of the AM detector, the above-described first to fifth embodiments can also be used.
It is clear that the same effect as that of the embodiment can be obtained.

In each of the first to fifth embodiments, a demodulator has been described. However, by using each of these demodulators in a receiver, a simple configuration can be achieved.
A receiver excellent in fading resistance can be realized. Also, by using a plurality of AGC amplifiers, it is possible to realize control suitable for each of the realized receivers.

Next, as an embodiment of the present invention, FM / AM
A demodulator and a receiver for separating and demodulating an FM modulation signal and an AM modulation signal from a modulated wave will be described. FIG. 8 is a block diagram showing a demodulation device as a sixth embodiment of the present invention. In FIG. 8, reference numeral 140 denotes an FM demodulator, and 3 denotes an FM · A
M signal input terminals and 4 are FM demodulation signal output terminals, and those having the same reference numerals as in FIGS. 1 and 4 to 7 indicate the same or equivalent.

Hereinafter, differences from the first embodiment will be described. It is assumed that an FM / AM modulated wave whose input level changes variously due to fading or the like is input to the input terminal 3.

Although an angle modulation receiver such as an FM receiver usually uses a limiter amplifier, as described above, a conventional FM receiver and an AM receiver are operated,
When an angle / amplitude modulated signal is received and the signal is separated and demodulated, the AGC in the AM receiver is used.
When the level of the input signal suddenly drops due to fading when the signal from the amplifying unit is input to the limiter amplifier of the FM receiver, such a high-speed level fluctuation close to the frequency of the AM modulation signal is caused by AGC. Since the amplifying unit cannot accurately follow, the level fluctuation is not removed, and therefore, the level of the signal input from the AGC amplifying unit to the limiter amplifier remains low for a while. As a result, the level of the input signal of the limiter amplifier may be lower than the limiter level.In such a case, the limiter amplifier cannot remove the amplitude change such as the amplitude modulation component, which is generated as noise in the demodulation output of the angle modulation. Then, there was a problem that accurate demodulation could not be performed.

However, in this embodiment, as described in detail in the first embodiment, the output of the AGC amplifying unit 10 has almost no level fluctuation component due to fading, and thus the output of the AGC amplifier 10 depends on the capability of the limiter amplifier. , Good FM demodulation can be realized without increasing.

As described above, conventionally, even if the frequency characteristic of the signal path of the FM / AM modulated wave from the AGC amplifying unit 10 to the AM detecting unit 20 has a slight slope, the FM modulated signal component has an AM component. In this embodiment, the frequency characteristic of the signal path of the FM / AM modulated wave from the AGC amplifier 10 to the AM detector 20 is flattened by the negative feedback loop. Therefore, the above-described interference can be reduced.

Generally, when demodulation of angle modulation and demodulation of amplitude modulation are simultaneously performed by one IC, if an angle / amplitude modulated wave is to be demodulated at the same time, the signal from the angle modulation demodulation circuit is converted to amplitude modulation. It leaks to the demodulation circuit and disturbs the band characteristic of the amplitude modulation demodulation, so that accurate amplitude modulation demodulation cannot be performed. However, in this embodiment, since the influence of the demodulation of the angle modulation on the demodulation of the amplitude modulation can be reduced, the demodulation of the angle modulation and the demodulation of the amplitude modulation can be simultaneously performed by one IC.

FIG. 9 is a block diagram showing a demodulator according to a seventh embodiment of the present invention. 9, the same reference numerals as those in FIGS. 1, 4 to 8 denote the same or equivalent components. Hereinafter, points different from the sixth embodiment will be described.

In the sixth embodiment, when the AGC signal contains high-frequency noise, the AGC loop may become unstable. However, in the present embodiment, since the high-frequency noise can be suppressed by the LPF 60, the operation of the AGC loop can be operated at high speed and stably.

FIG. 10 is a block diagram showing a demodulator according to an eighth embodiment of the present invention. 10, the same reference numerals as those in FIGS. 1, 4 to 9 denote the same or equivalent components. Hereinafter, points different from the sixth and seventh embodiments will be described.

When the signal is received by the on-vehicle receiver, the reception power also changes due to changes in the distance from the transmitting station and changes in various conditions. Therefore, in this embodiment, the AGC amplifier 70 is provided before the AGC amplifier 10 and the AGC amplifier 7
By controlling 0 with an AGC signal that also includes a DC component, this change in power can be absorbed.

At this time, by setting the cutoff frequency of the LPF 42 for determining the time constant to be lower than the frequency of the AM modulation signal, the FM / AM input to the AGC amplifier 10 is set.
Without changing the AM modulated signal component in the modulated wave,
Since it is possible to absorb low-speed amplitude fluctuations, such as a part of fading having a lower frequency than the modulation signal and a slow level fluctuation due to a change in the distance to the transmitting station, AG
The FM / AM modulated wave input to the C amplifying unit 10 is a signal in which the effect of fading is suppressed as compared with the case of the sixth and seventh embodiments, and more excellent demodulation can be performed.

FIG. 11 is a block diagram showing a demodulator according to a ninth embodiment of the present invention. 11, the same reference numerals as in FIGS. 1, 4 to 10 indicate the same or equivalent. Hereinafter, differences from the above-described sixth to eighth embodiments will be described.

In this embodiment, the AGC amplifying section 90
It is controlled by an AGC signal including a DC component via the LPF 43 having a cutoff frequency lower than the frequency of the modulation signal. Therefore, the AGC amplification unit 90 outputs the LPF 4 out of the level fluctuations of the FM / AM modulated wave input from the input terminal 3.
Fluctuations lower in frequency than the cutoff frequency of No. 3 are absorbed, and a more stable AM modulated wave is output.

Therefore, in this embodiment, the FM / AM modulated signal is added by appropriately adding an AGC amplifying unit controlled by an AGC signal containing a DC component at a lower frequency than the AM modulated signal as described above. Wave level fluctuations can be made more stable.

In this embodiment, the sixth, seventh, and eighth
Instead of the demodulation by the high-speed AGC loop using only the AGC amplifier 10 as in the embodiment of the present invention, the change of the gain of the AGC amplifier with respect to the change of the AGC signal can be reduced by adding the AGC amplifier 100 of high-speed response. I'm making it big. That is, the dynamic range of demodulation for the level fluctuation of the input signal by the AGC amplifiers 100 and 10, the AM detector 20, and the AGC signal generator 40 is expanded.
For this reason, it is possible to cope with a level fluctuation due to fading larger than in the sixth, seventh and eighth embodiments.

Therefore, in this embodiment, the dynamic range can be further expanded by adding an AGC amplifier controlled by an AGC signal having substantially the same frequency as that of the AM modulation signal as described above. Can be.

Since the AGC amplifier 100 is controlled by the AGC signal from which the DC component has been removed, an arbitrary operating point can be set as described as the control method of the AGC amplifier 10 in the first embodiment. And stable control can be performed.

Therefore, the output of the AGC amplifier 10 is an FM / AM modulated wave having almost no amplitude fluctuation. By taking out this signal and inputting it to the FM demodulator 140, the limiter in the FM demodulator 140 is output. There is no need to increase the gain of the amplifier too much.

In this embodiment, the case where separate capacitors 30 and 80 are used as means for cutting off the DC component of the AGC signal has been described. However, the output of the capacitor 30 is used to control the AGC amplifier 100. Obviously, the same effect can be obtained even if the above-mentioned conditions are satisfied.

In this embodiment, the LPF 42 and the LPF 43 are used as LPFs for passing the low frequency components of the AGC signal.
However, when the LPF 42 and the LPF 43 are the same LPF, the output of the LPF 42 is
It is clear that the same effect can be obtained even if the GC amplification section 90 is controlled.

FIG. 12 is a block diagram showing a demodulator according to a tenth embodiment of the present invention. In FIG. 12, 1
50 is an AGC amplifying unit, and 160 is an AGC
A capacitor for controlling the amplifying unit 150 in an alternating current manner. In addition, the same reference numerals as those in FIGS. 1 and 4 to 11 denote the same or equivalent components. Hereinafter, points different from the above-described sixth to ninth embodiments will be described.

In the present embodiment, an AGC amplifier 150 is provided in a stage preceding the FM demodulator 140, and a capacitor 160
The AGC signal whose DC component is cut off by
By controlling the gain of the C amplifying unit 150, a signal more suitable as an input to the FM demodulation unit 140 can be obtained, and good FM demodulation is enabled. FIG. 13 is a block diagram showing a demodulation device as an eleventh embodiment of the present invention. 13, the same reference numerals as those in FIGS. 1, 4 to 12 denote the same or equivalent components. Hereinafter, the sixth to the above-mentioned
The differences from the tenth embodiment will be described.

The FM / AM modulated wave supplied to the input terminal 3 is supplied to the AGC amplifier 110 controlled by the AGC signal from the AGC signal generator 40, and is amplified or attenuated. The output of the AGC amplifier 110 is frequency-converted by the frequency converter 130 using the output of the local oscillator 120, and is then supplied to the AGC amplifier 70 controlled by the AGC signal from the AGC signal generator 40, and amplified or attenuated. Is done. The output of the AGC amplifier 70 is supplied to the AGC amplifier 10.

Here, the AGC amplifier 110 and the AGC amplifier 70 have an amplitude of a low-speed cycle such as a lower frequency than the AM modulated signal, a slow level fluctuation due to a part of fading or a change in the distance from the transmitting station. It has a similar function in that it absorbs fluctuations, but the carrier frequencies of the signals to be amplified are different from each other.

Therefore, in the present embodiment, even when the frequency is converted, the same effects as those of the above-described embodiments can be obtained, that is, it is possible to make the frequency independent of the carrier frequency.

Now, in the sixth to eleventh embodiments,
FM / AM modulation is taken as an example of angle / amplitude modulation, and the case where the signal is demodulated has been described.
The present invention is not limited to the demodulation of the modulated signal, but may be performed by using another angle modulation demodulation means in place of the FM demodulation section and using another amplitude modulation demodulation means in place of the AM detection section. It is clear that the same effects as those of the eleventh embodiment can be obtained.

In each of the sixth to eleventh embodiments, a demodulator has been described. By using each of these demodulators in a receiver, a receiver having a simple configuration and excellent fading resistance can be obtained. Can be realized. Also, by using a plurality of AGC amplifiers, it is possible to realize control suitable for each of the realized receivers.

In each of the above embodiments, the AGC
Although a capacitor has been described as a means for blocking the DC component of a signal, the present invention is not limited to this capacitor.
It is apparent that the same effect can be obtained by using an HPF (High Pass Filter), a BPF, or the like that passes an M-modulated signal and blocks a DC component.

Further, in each of the above-described embodiments, the AGC extracted from the output side of the capacitor as the DC cutoff means is used.
BPF whose signal is the pass band of the frequency of the AM modulation signal
Although the input is 50, it is apparent that the same effect can be obtained by using the AGC signal taken out from the input side of the capacitor.

Further, in each of the above-described embodiments, the AM
Although the description has been made using the BPF as a means for extracting the modulation signal, when the fading frequency is closer to the frequency of the AM modulation signal, the same effect can be obtained by using the HPF through which the AM modulation signal passes. Is clear.

As described above, the receiver using the demodulator according to the present invention can be used for demodulation of signals multiplex-modulated by narrow-band angle modulation and amplitude modulation, and can be used for mobile communication systems such as road-to-vehicle information systems. Used for high-precision communication.

[0086]

As described above in detail, according to the present invention, when demodulating an amplitude-modulated signal, or simultaneously separating and demodulating an angle-amplitude-modulated signal, a high-speed response is provided before the AM detector. The AGC amplifier is disposed, an AGC signal is generated from the output of the AM detector, the DC component of the AGC signal is cut off, and the static operating point of the AGC amplifier is arbitrarily set, so that the noise resistance characteristics and the like are improved. AGC operation with excellent control amount-control signal characteristics (for example, gain-control voltage characteristics) can be easily realized.

Further, by performing high speed negative feedback control of the AGC amplifier, the output of the AM detector becomes almost DC,
Even if the dynamic range of the AM detector is not widened, detection can be performed without increasing non-linear distortion during high-speed level changes of the input signal.

In order to obtain an amplitude-modulated demodulated signal from the feedback control signal of the AGC amplifier, even if the frequency characteristic of the signal path for demodulating the amplitude-modulated wave is not flat, the frequency is controlled by the negative feedback by the AGC loop. The characteristics are flat. Accordingly, there is an effect that interference of the angle modulation component with the amplitude modulation demodulation output can be reduced.

Further, there is an effect that the dependence on the limiting ability of the amplitude limiting means in the angle modulation demodulating means can be reduced.

Further, even if there is a level fluctuation such as fading, accurate amplitude modulation demodulation can be performed, and there is an effect that an amplitude modulation component and an angle modulation component can be separated and demodulated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a demodulation device as a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing an example of a gain-control voltage characteristic of the AGC amplifier in FIG.

FIG. 3 is a waveform chart for explaining the operation of the demodulation device in FIG. 1;

FIG. 4 is a block diagram showing a demodulation device as a second embodiment of the present invention.

FIG. 5 is a block diagram showing a demodulation device as a third embodiment of the present invention.

FIG. 6 is a block diagram showing a demodulation device as a fourth embodiment of the present invention.

FIG. 7 is a block diagram showing a demodulation device as a fifth embodiment of the present invention.

FIG. 8 is a block diagram showing a demodulation device as a sixth embodiment of the present invention.

FIG. 9 is a block diagram showing a demodulation device as a seventh embodiment of the present invention.

FIG. 10 is a block diagram showing a demodulation device as an eighth embodiment of the present invention.

FIG. 11 is a block diagram showing a demodulation device as a ninth embodiment of the present invention.

FIG. 12 is a block diagram showing a demodulation device as a tenth embodiment of the present invention.

FIG. 13 is a block diagram showing a demodulation device as an eleventh embodiment of the present invention.

FIG. 14 is a waveform diagram showing waveforms of an input signal and an output signal of an AM detector in a general AM receiver.

FIG. 15 is a characteristic diagram showing a frequency characteristic of a signal path relating to demodulation of an amplitude-modulated signal in a case where an angle / amplitude-modulated signal is separated and demodulated.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... AM modulated wave input terminal, 2 ... AM demodulated signal output terminal, 3 ... FM / AM modulated wave input terminal, 4 ... FM demodulated signal output terminal, 10 ... AGC amplifier, 20 ... AM detector,
30: DC blocking capacitor, 40: AGC signal generator, 41: Amplifier, 42: LPF2, 43: LPF3,
50 BPF, 60 LPF, 70 AGC amplifier, 8
0: DC blocking capacitor, 90: AGC amplifier, 10
0: AGC amplifier, 110: AGC amplifier, 120: Local oscillator, 130: Frequency converter, 140: FM demodulator, 150: AGC amplifier, 160: DC blocking capacitor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-332221 (JP, A) JP-A-54-75975 (JP, A) JP-A-61-261904 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) H03D 1/00-5/00 H03G 3/10-3/20

Claims (7)

(57) [Claims] 1. A demodulation device for demodulating an amplitude-modulated signal from a modulated wave obtained by amplitude-modulating a carrier with an amplitude-modulated signal, comprising the steps of: receiving the modulated wave; amplifying and outputting the modulated wave; Is controlled in response to a separately input control signal.
An automatic gain control (hereinafter, referred to as AGC) amplifier, an AM detector that receives a modulated wave from the first AGC amplifier, detects an amplitude change of the modulated wave, and outputs the AM. An AGC signal generation unit that receives an output signal from the detection unit, generates and outputs an AGC signal from the output signal, and receives an AGC signal from the AGC signal generation unit and cuts off a DC component in the AGC signal And a DC cutoff unit that outputs the control signal, and an AGC signal that is output from the AGC signal generation unit or the DC cutoff unit, and filters the amplitude modulation signal from the AGC signal to generate a demodulated output. And a filtering means for outputting. 2. A demodulation device for performing angle modulation on a carrier wave with an angle modulation signal and separating and demodulating the angle modulation signal and the amplitude modulation signal from a modulation wave obtained by amplitude modulation with an amplitude modulation signal. A wave is input, amplified and output, and the gain is controlled according to a separately input control signal.
An AGC amplification unit, an AM detection unit that receives a modulated wave from the first AGC amplification unit, detects and outputs an amplitude change of the modulated wave, and receives a modulated wave from the first AGC amplification unit. An angle modulation demodulation unit for receiving a modulated wave, demodulating the angle modulated signal from the modulated wave, and outputting the demodulated output as a demodulated output;
An output signal from the M detector is input, and
An AGC signal generator for generating and outputting a C signal;
An AGC signal from a C signal generator, a DC interrupter that interrupts a DC component in the AGC signal and outputs the AGC signal as the control signal, and an AGC signal output from the AGC signal generator or the DC interrupter And a filtering unit for filtering the amplitude modulated signal from the AGC signal and outputting the filtered signal as a demodulated output. 3. A demodulation device for performing angle modulation of a carrier wave with an angle modulation signal and separating and demodulating the angle modulation signal and the amplitude modulation signal from a modulated wave obtained by amplitude modulation with an amplitude modulation signal. Two first AGC amplifying sections, each of which receives the modulated wave, amplifies and outputs the modulated wave, and whose gain is controlled in accordance with a separately input control signal; A modulated wave output from one of the amplifiers is input, and an AM detector that detects and outputs a change in the amplitude of the modulated wave and is output from the other of the first AGC amplifier. A modulated wave is input, the angle modulated signal is demodulated from the modulated wave, and an angle modulation demodulation unit for outputting as a demodulated output, and an output signal from the AM detection unit are input, and an AGC signal A that generates and outputs A C signal generator, AGC from the AGC signal generating section
Input a signal, cut off the DC component in the AGC signal,
A DC cut-off unit for outputting the control signal;
Filtering means for receiving an AGC signal output from a signal generation unit or a DC cutoff unit, filtering the amplitude modulation signal from the AGC signal, and outputting the filtered signal as a demodulated output. . 4. The demodulation device according to claim 1, wherein the signal path from the AM detector to the first AGC amplifier via an AGC signal generator and a DC cutoff unit includes: A demodulator, comprising: a low-pass filter having a cutoff frequency higher than a frequency of the amplitude modulation signal, and removing noise of a signal passing through the low-pass filter. 5. The demodulation device according to claim 1, wherein the modulated wave is inputted, amplified and outputted, and the gain thereof is controlled according to a separately inputted control signal. At least one second AGC amplifying unit is provided in front of the first AGC amplifying unit, and all or a part of the second AGC amplifying unit is provided with an AGC signal from the AGC signal generating unit.
A demodulation device for inputting a GC signal as the control signal. 6. The demodulation device according to claim 1, wherein the modulated wave is input, and the frequency of the modulated wave is converted to another frequency and output. Is provided before the first AGC amplifying section. 7. A receiver using the demodulation device according to claim 1, 2, 3, 4, 5, or 6.