JPH0424661Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention expands the fade margin of the receiver and eliminates interference noise that falls near the transmission band.
Concerning a receiver that prevents SQL malfunctions.

[Prior Art] Conventionally, this type of receiver has had a configuration as shown in FIG. 3 or FIG. 4.

That is, the receiver shown in FIG. 3 includes a receiving frequency conversion circuit section 31 for converting a high frequency signal into an intermediate frequency signal, a power divider 32, an intermediate frequency band pass filter 33, and an intermediate frequency band pass filter. Vessel 33
It has a narrow band pass filter 34 having a narrower pass band characteristic, a high speed switch 35, and an AGC function,
and a main intermediate frequency amplifier 3 having two output terminals.
6, a controller 37 that detects the AGC voltage and sends a signal to control the high-speed switch 35, and a demodulator 38.
It is composed of a passband filter 39 having a narrowband characteristic for removing interference noise that falls near the signal band, and an SQL detection circuit 40 that detects the signal power and sends out an SQL alarm signal. Note that a indicates a receiver input terminal, B a receiver output terminal, c an SQL alarm signal output terminal, and d a control signal for controlling the high-speed switching device 35.

Furthermore, the receiver shown in FIG. 4 has a narrow passband filter 34 on the output side of the main intermediate frequency amplifier.

Conventional receiver C/C with these circuit configurations
N improvement is the control signal d that detected the receiver input electric field.
When the input electric field reaches a certain level, the high-speed switch 35 is controlled and the narrow band passband filter 3 is switched on.
This was done by selecting 4.

[Problems to be solved by the invention] In the conventional receiver described above, when trying to satisfy both the functions of improving the C/N of the receiver and preventing SQL malfunction, narrowband filtering for improving the C/N is necessary. Because it is necessary to separately install a receiver and a narrowband filter to prevent SQL malfunctions, the receiver has a complicated configuration, a large size, and a high price.

The present invention was made in view of the above problems, and in addition to the intermediate frequency band pass filter, a narrow band pass filter having a narrower pass band width than that filter is provided, and its characteristics are as follows. In addition to removing interference noise that falls near the signal band, the receiver C/
By improving N and choosing a low threshold level, one bandpass filter can
The purpose is to provide a receiver that can prevent SQL malfunctions and increase the fade margin.

[Means for Solving the Problems] In order to achieve the above object, the receiver of the present invention includes a reception frequency conversion means for converting a reception signal into an intermediate frequency signal, and an intermediate frequency conversion means for removing out-of-band noise from the intermediate frequency signal. a frequency band-pass filtering means; an intermediate-frequency amplifying means for amplifying the output signal of the intermediate-frequency band-pass filtering means to a predetermined value; narrow band pass filtering means for band-limiting one signal amplified by the means; the other signal amplified by the intermediate frequency amplifying means and the output signal of the narrow band pass filtering means; Alternatively, control means selects and outputs according to the received input electric field, demodulation means demodulates the output signal of the control means, and detects signal power from the output signal of the narrow band pass filter means and outputs an SQL alarm signal. The configuration includes a means for

[Example] Hereinafter, an example of the present invention will be described based on the drawings.

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

In the drawing, 1 is a receiving frequency conversion circuit section for converting a high frequency signal into an intermediate frequency signal, which includes a pre-frequency amplifier, a frequency converter, a local oscillator, a pre-intermediate frequency amplifier, etc., and 2 is an intermediate frequency band-pass filter. , 3 is a main intermediate frequency amplifier that has an AGC function and has two output terminals, 4 is a controller that detects the AGC voltage and sends out a signal to control the high-speed switch 7, and 5 is near the transmission signal band. A narrow band pass filter 6 has a narrower pass band characteristic than the intermediate frequency band pass filter 2 to remove interference noise that falls into the filter and improve the C/N of the receiver. 6 is a fixed filter for correcting loss. 8 is a resistive attenuator, 8 is a power divider, 9 is an alarm control signal circuit for detecting signal power and sending out an SQL alarm signal, and 10 is a demodulator. a is the receiver input terminal, b is the receiver output terminal,
c is SQL alarm signal output terminal, b is high-speed switch 7
shows the control signal that controls the

In the receiver configured as described above, the reception input electric field input to the receiver input terminal a is converted to an intermediate frequency by the reception frequency conversion circuit section 1, and then removed by the intermediate frequency bandpass filter 2 to eliminate out-of-band noise. is removed, and in the main intermediate frequency amplifier 3,
The power is amplified to a certain level by the AGC function.
The intermediate frequency signal power of the main intermediate frequency amplifier 3 is outputted in two branches, and one signal power A is inputted to the high speed switch 7 through the fixed resistance attenuator 6. The other signal power B is input to the narrow band pass filter 5.

This narrow band pass filter 5 satisfies the characteristics of the pass band width that can eliminate interference noise that falls near the signal band and improve the receiver C/N. One of the outputs is applied to the alarm control circuit 9. The alarm control circuit 9 detects the signal power from which interference noise has been removed, makes the SQL alarm accurate, and sends out the SQL alarm signal.

The signal power output from the other output terminal of the power divider 8 is input to the high speed switch 7. The high-speed switch 7 to which the two signal powers A and B are input selects one of the signal powers in accordance with a control signal sent from the controller 4 that has detected the received input electric field. The selected signal power is input to the demodulator 10 and output as baseband signal power to the receiver output terminal b. Here, since the passband width of the intermediate frequency bandpass filter 2 is a function that determines the threshold level of the receiver, the narrow bandpass filter 5 is more important than the intermediate frequency bandpass filter 2. A low threshold level is obtained.

That is, when the signal is passed through the narrow band pass filter 5, an improvement in C/N can be obtained. Therefore, the received input electric field decreases from the standard value, and a certain electric field,
That is, when only the intermediate frequency bandpass filter 2 is used, the electric field immediately before the threshold starts to occur is used as a reference, and when the electric field becomes lower than that electric field, the high speed switch 7 is controlled by the control signal d. If the narrow band pass filter 5 is selected, the C/N ratio can be improved and the threshold level can be lowered.

Normally, from the standard input electric field to the reference input electric field, deterioration of receiver distortion is eliminated by passing only the intermediate frequency bandpass filter 2, and the input electric field is reduced to a certain constant value. At this time, the signal is also passed through a narrow band pass filter 5 to improve the C/N and expand the threshold level of the receiver.

FIG. 2 is a block diagram of a second embodiment of the present invention, showing an example of a structure in which a noise detector is used and a high-speed switch is controlled according to the amount of noise in the receiver. That is, the circuit configuration is such that a control signal is sent from the noise signal controller 12 using a signal from the noise detector 11, and the high speed switch 7 is controlled by this control signal.

[Effects of the invention] As explained above, according to the receiver of the invention,
By using a single bandpass filter, it is possible to increase the fade margin and prevent SQL malfunctions at the same time, which has the effect of making the receiver smaller and cheaper. .

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are examples of the present invention,
FIG. 1 shows a block diagram of a first embodiment, FIG. 2 shows a block diagram of a second embodiment, and FIGS. 3 and 4 show block diagrams of a conventional example. DESCRIPTION OF SYMBOLS 1... Reception frequency conversion circuit section, 2... Intermediate frequency band pass filter, 3... Main intermediate frequency amplifier, 4...
... Controller, 5 ... Narrow band pass filter, 6 ... Fixed resistance attenuator, 7 ... High speed switch, 8 ... Power divider, 9 ... Alarm control circuit, 10 ... Demodulator, 11
... Noise detector, 12 ... Noise signal controller.

Claims (1)

[Claims for Utility Model Registration] Reception frequency conversion means for converting a received signal into an intermediate frequency signal; intermediate frequency bandpass filtering means for removing out-of-band noise from the intermediate frequency signal; and the intermediate frequency bandpass filtering means. intermediate frequency amplifying means for amplifying an output signal to a predetermined value; and narrow band pass having a narrower passband characteristic than the intermediate frequency band pass filtering means and band limiting one signal amplified by the intermediate frequency amplifying means. a filtering means; and a control means for selecting and outputting one of the other signal amplified by the intermediate frequency amplifying means and the output signal of the narrow band pass filtering means according to the noise or the received input electric field. A receiver comprising: demodulating means for demodulating the output signal of the control means; and means for detecting signal power from the output signal of the narrow band pass filtering means and outputting an SQL alarm signal.