JPH0322713A - Receiver with c/n display - Google Patents

Abstract

PURPOSE:To easily display the ratio of C/N(carrier/noise) indicating an actual reception state even by a receiver which includes an LNA and a booster amplifying a fine signal by comparing the level of a target frequency with the level of a no-signal frequency and displaying the result. CONSTITUTION:When the power source is turned on, the frequency is varied and a noise level is detected at the no-signal frequency and stored on a memory. Then the received signal level (intermediate frequency level) at the current reception frequency (normally the target frequency) is inputted and stored on the memory in a control circuit 5. Then the target signal reception level and noise level are compared and the result is displayed on a display device 9. Consequently, even the receiver with the C/N display which has the low-noise amplifier(LNA) and booster can easily display the actual reception state is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a receiver having an added function of displaying a C/N (carrier/noise) ratio of a reception band.

[Conventional technology]

As shown in Figure 3, in a receiver that receives FM, AM, TV, etc. broadcasts using a normal antenna such as a Yagi antenna, the noise within the reception band is small, so the input electric field strength (intermediate frequency signal level) Even if it is displayed as is, it can be put to practical use. [Problem to be solved by the invention] However, the converter is equipped with an LNA (low noise amplifier).
In satellite broadcasting receivers that use , and community receivers that use booths, the signal and noise components are greatly amplified within the passband of the LNA and booster, so the characteristics shown in Figure 4 are obtained. When the input electric field strength detected at a subsequent stage is displayed, it contains a considerable amount of noise, and there is a problem that the relationship between the actual reception state and the displayed input electric field strength does not match.

The present invention has been made in view of the above points, and its purpose is to provide a receiver with an LNA or a booster.
To provide a receiver with a C/N display that can easily display the actual reception state.

[Means to solve the problem]

To this end, the present invention provides means for storing the signal level of the target frequency, means for storing the level of the no-signal frequency distant from the target frequency, means for comparing both levels, and displaying the output of the comparing means. C/N display means is provided.

The comparison means may compare the two levels when the power is turned on and when the target frequency changes, and update the display contents of the C/N display means.

〔Example〕

Examples of the present invention will be described below. FIG. 1 is a diagram showing a receiving circuit of a receiver according to one embodiment. An input voltage applied to an input terminal 1 is tuned in a tuner 2 by a frequency signal from a local oscillation circuit 4 controlled by a PLL circuit 3. Note that the PLL circuit 3 is controlled by a control circuit 5 consisting of a microcomputer. Then, the intermediate frequency signal obtained by the tuner 2 is detected by the detection circuit 6,
It is output to the audio/video circuit 7.

In addition to this basic structure, this embodiment also includes an IF level detection/A/D circuit 8 to detect the intermediate frequency level, convert it into a digital signal, and control the digital signal. In addition to the circuit 5, processing is performed by the program shown in FIG. 2, and the C/N is displayed on the C/N display 9.

In FIG. 2, first, when the power is turned on, the frequency is changed, the noise level is detected at the no-signal frequency, and the level N is similarly stored in the memory. Next, the received signal level (intermediate frequency level ) is taken in, and the control circuit 5
The level C is stored in the internal memory. Next, the target signal reception level C and the noise level N are compared and calculated, and the result is displayed on the display 9.

As this display 9, a display element consisting of, for example, a 7-segment element is used, and displays, for example, rcN14 dBJ.

In Figure 2 above, we explained the case when the power is turned on, but the same process is performed when the frequency changes (channel changes), and the level of the reception frequency (target frequency) and the no-signal frequency (preset dummy channel, etc.) separated from it are processed in the same way. are compared and a C/N display is performed.

In other words, each time the target frequency changes, the comparison result between the target signal reception level C and the noise level N is updated, and based on this, the
/N The display content on the display 9 is updated.

Note that the detection of a no-signal frequency (or dummy channel) is not limited to one, but a plurality of detections, and the noise level N can be obtained by averaging the reception levels of the detection.

Further, noise detection is performed quickly so that noise does not appear in the video output, or the video is muted during that time.

〔Effect of the invention〕

As described above, according to the present invention, the levels of the target frequency and the no-signal frequency are compared and displayed, so that even in a receiver including an LNA or a booster that amplifies weak signals, the actual reception status is displayed. This has the advantage that an appropriate C/N ratio can be displayed. Further, by using this signal for C/N display, it is possible to apply it to a mechanism for seeking the reception frequency and perform good reception frequency tuning.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a receiver according to an embodiment of the present invention, and FIG.
The figure is a flowchart of the operation program of the control circuit of the receiver, and Figure 3 is a diagram of received signal characteristics of a general receiver.
FIG. 4 is a received signal characteristic diagram of a receiver equipped with an LNA and a booster.

Claims (2)

[Claims] (1) means for storing a signal level of a target frequency, means for storing a level of a no-signal frequency distant from the target frequency, means for comparing both levels, and a C/C/ 1. A receiver with a C/N display, comprising: N display means. (2) The first aspect of the present invention is characterized in that the comparison means compares the two levels when the power is turned on and when the target frequency changes and updates the display contents of the C/N display means.
Receiver with C/N display as described in section.