JP2861877B2 - Receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver, and more particularly to a receiver suitable for receiving a weak signal having an unstable frequency.

[0002]

2. Description of the Related Art Conventionally, when an attempt is made to receive a radio wave whose reception frequency fluctuates, it is required to increase the frequency bandwidth of the receiving apparatus within the fluctuating range so as to always fall within the reception band. In this case, even if the received signal is a signal having a narrow occupied bandwidth, it is necessary to receive noise in an originally unnecessary frequency band in order to provide a receiving device having a bandwidth including the frequency width of the variation. As a result, the noise of the receiving apparatus relatively increases.

[0003]

In particular, when a weak signal is received, the effect of noise due to the wide frequency bandwidth increases, and the received signal is buried in the noise, making clear reception difficult. . Usually, when a weak signal is received, it is preferable to reduce the reception bandwidth to increase the reception sensitivity within that band, but this makes it difficult to deal with the above-mentioned frequency fluctuation. Therefore, conventionally, there is no other way than to increase the transmission output or to limit the use to a short distance, which hinders the effective use of the receiving device. An object of the present invention is to provide a receiving device capable of obtaining reception sensitivity equivalent to that of a narrow-band receiving device while widening the band.

[0004]

A receiving apparatus according to the present invention comprises a distributor for dividing a frequency band to be received into a plurality of narrow frequency bandwidths , and a system for each frequency bandwidth.
A band-pass filter provided for filtering signals of each system,
Amplifier that amplifies the amplified signal and detects the amplified signal
Detector that suppresses noise from the detected signal
Combines the output of each system of each frequency bandwidth with the noise cutter
And a noise cutter for each system.
The level is set uniformly.

[0005] A receiving apparatus according to the present invention further comprises a distributor for dividing a frequency band to be received into a plurality of narrow frequency bandwidths, and a signal provided for each system of each frequency bandwidth. A bandpass filter for filtering, a variable gain amplifier for amplifying the filtered signal, a detector for detecting the amplified signal, a noise cutter for suppressing noise from the detected signal, A synthesizer that combines the outputs of the respective systems of the frequency bandwidth, an AGC controller that integrally controls the gains of the variable gain amplifiers of the respective systems based on the output level of the combiner, and a noise cutter of the respective systems. Are set uniformly.

[0006]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of the present invention. The receiving antenna 1 has an RF amplifier 2
Are connected, and the received signal is RF-amplified. The output side of the RF amplifier 2 is connected to a mixer 3 which receives the local signal LOCAL and converts the frequency of the received signal. The mixer 4 distributes the frequency-converted signal to n (n is an integer of 2 or more). Is connected. The bandpass filters 51 to 5n are connected to the distributor 4 in parallel corresponding to the n signals distributed. Each of the band filters 51 to 5n is set to a frequency bandwidth corresponding to the received signal, and the bandwidth of each of the band filters 51 to 5n is configured to be continuous over the entire reception frequency region.

The bandpass filters 51 to 5n have variable gain amplifiers 61 to 6n and amplifiers 61 to 6n, respectively.
Detectors 71 to 7n for detecting the outputs of the detectors, and noise cutters 81 to 8n for removing low-level signals included in the outputs of the detectors, that is, noises at a set level, are cascaded. The outputs of the noise cutters 81 to 8n are combined in the combiner 9 and output to the output terminal. The level of the signal at the output terminal is detected by the AGC controller 10, and the gains of the variable gain amplifiers 61 to 6n are simultaneously controlled so that the output level becomes constant in accordance with the detected level. Is done.

According to this configuration, the radio wave arriving at the antenna 1 is amplified by the RF amplifier 2 and the local signal LO is amplified by the mixer 3.
The frequency is converted by the CAL, and the entire receiving frequency region is distributed in the distributor 4 in units of the receiving bandwidth. Now, FIG.
As shown in FIG. 7, if a signal in the frequency band corresponding to the bandpass filter 51 is received, the received signal is amplified by the variable gain amplifier 61, detected by the detector 71,
The noise is output to the synthesizer 9 through the noise cutter 81. The other bandpass filters 52-5n do not have signal components, so that only noise is amplified by the variable gain amplifiers 62-6n, and detectors 72-7n and noise cutters 82-8n
Is output to the synthesizer 9 through.

At this time, in the noise cutters 81 to 8n, in order to suppress the noise set by the noise cut signal, almost only the reception signal component is output from the noise cutter 81, and almost all of the other noise cutters 82 to 8n output. No signal is output. Therefore, by combining the outputs of the noise cutters 81 to 8n with the combiner 9, it is possible to clearly receive only the received signal with almost no noise. At this time, the AGC controller 10 controls each variable gain amplifier 6 based on the output level.
By controlling the gains of 1 to 6n, the degree of amplification in each frequency band is made equal, the noise level in each frequency band is made equal, and noise can be suppressed at the same level in the noise cutters 81 to 8n. .

Therefore, in this embodiment, the receivable frequency region can be widened, and this frequency region is divided into a plurality of narrow frequency bands, and reception is performed in any one of the frequency bands. In this frequency band, noise can be suppressed, so that a wider band can be realized as a whole of the receiving apparatus, but reception with the same sensitivity as that of a narrow band receiver is possible.

FIG. 3 is a block diagram of a reference example of the present invention. In this reference example , the configuration is substantially the same as that of the first embodiment, but the noise cutter provided in the first embodiment is removed . That is, if the gain of each of the variable gain amplifiers 61 to 6n is controlled so that the noise in each frequency band is at a low level, a result equivalent to noise reduction by a noise cutter can be obtained. Variable gain amplifiers 61 to 6
The amplification level of n is set appropriately.

In this reference example , for example, as shown in FIG. 2, when a received signal is received by the band filter 51, the AGC controller 10
Operates to control the variable gain amplifier 51 and simultaneously controls the gains of the variable gain amplifiers 52 to 5n of the other frequency band systems, so that noise in all frequency bands is suppressed. . Therefore, it is considered that the noise output at the output of the synthesizer 9 is reduced, and the function of the narrow band receiving device can be obtained while the band is widened.
Is expected to have remarkable effects as in the first embodiment.
Is difficult.

FIG. 4 is a block diagram showing a second embodiment of the present invention. In this embodiment, the amplifiers 61 to 6n provided in the systems of the respective frequency bands are configured as amplifiers having fixed gains and do not perform the AGC control, and only the noise cutters 81 to 8n provided in the systems of the respective frequency bands are used. A configuration for suppressing noise of each system is adopted. As described above, it is clear from the description in the first embodiment that the function as the narrowband receiving apparatus can be obtained by suppressing the noise only by the noise cutter. In this embodiment, an IF amplifier 11 is inserted.

FIG. 5 is a block diagram showing a third embodiment of the present invention. Also in this embodiment, in each system, noise is suppressed only by the noise cutters 81 to 8n.
This embodiment is an example in which the present invention is applied not to the superheterodyne system but to the direct reception system. Even with such a configuration, the function as a narrowband receiver can be obtained.

[0015]

As described above, the present invention divides a frequency band to be received into a plurality of narrow frequency bandwidths, amplifies and outputs a signal in a system of any of the frequency bandwidths, and noise suppressed in each Te system odor all frequency bandwidths after performing detection in a system, since the output by synthesizing the output of the system of the frequency bandwidth over which accordingly, receivable frequency band Can be widened, and on the other hand, signals can be received in a narrow band, and there is an effect that it is possible to cope with frequency fluctuations of a received signal and to receive a weak signal clearly.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a noise suppressing operation in the receiving device of FIG. 1;

FIG. 3 is a block diagram of a reference example of the present invention.

FIG. 4 is a block diagram of a second embodiment of the present invention.

FIG. 5 is a block diagram of a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Antenna 2 RF amplifier 3 Mixer 4 Distributor 51-5n Band filter 61-6n Amplifier (variable gain amplifier) 71-7n Detector 81-8n Noise cutter 9 Combiner 10 AGC controller

Claims (2)

(57) [Claims] 1. A divider that divides a frequency band to be received into a plurality of narrow frequency bandwidths, a band-pass filter provided in each system of each frequency bandwidth and filtering signals of each system, An amplifier for amplifying the filtered signal, a detector for detecting the amplified signal, a noise cutter for suppressing noise from the detected signal, and a combiner for combining outputs of the respective systems of the respective frequency bandwidths Wherein the setting levels of the noise cutters of the respective systems are set uniformly. 2. A divider for dividing a frequency band to be received into a plurality of narrow frequency bandwidths, a band-pass filter provided in each system of each frequency bandwidth and filtering signals of each system, A variable gain amplifier for amplifying the filtered signal, a detector for detecting the amplified signal, a noise cutter for suppressing noise from the detected signal, and combining the outputs of the respective systems of the respective frequency bandwidths. and combiner, that on the basis of the output level of the synthesizer and an AGC controller for integrally controlling the gain of the variable gain amplifier of each system, said uniformly set the setting level of the system noise cutter A receiving device characterized by the above-mentioned.