JPH02306728A - Antenna sensitivity adjustment equipment - Google Patents

Abstract

PURPOSE:To prevent noise amplification while no circuit component is required by adjusting the antenna sensitivity and suppressing the input signal within a limit at all times even when the gain control range of an AGC circuit is limited. CONSTITUTION:When the output level of automatic gain control(AGC) circuit detected by a level detection circuit 16 exceeds a level within the gain control range, a comparator 17 outputs a 1st control signal to a motor control circuit 13, and when the AGC level is lower than the level of the gain control range, the control circuit 17 outputs a 2nd control signal to the motor control circuit 13. When a 1st control signal is received, the motor control circuit 13 controls an antenna lifting motor 12 to control the antenna lifting motor 12, thereby elevating the antenna 1 to a desired height. Even when the gain control range of the AGC circuit 2 is insufficiently limited to a prescribed level depending on the relation of noise production of the circuit competent but exceeds the range, the antenna sensitivity is adjusted to limit the level within the limit. Thus, the production of undesired noise is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an antenna sensitivity adjustment device equipped with AGC means.

(Prior art) A radio receiver is equipped with an AGC (automatic gain control) circuit that amplifies the input signal and outputs a signal at a constant level even if the level of the input signal received by the antenna fluctuates. . This AGC is particularly useful for receivers such as FM receivers whose reception sensitivity tends to vary greatly depending on the reception location.
The operation of the circuit is important.

FIG. 2 is a block diagram showing an example of the configuration of an FM receiver equipped with such an AGC circuit. An input signal received by antenna 1 is applied to AGC circuit 2. As shown in FIG. The AGC circuit 2 includes, for example, a high frequency amplification circuit 3, a frequency conversion circuit 4, a local oscillation circuit 5, an intermediate frequency amplification circuit 6, and an output level detection circuit 7. The output level of the intermediate frequency amplifier circuit 6 is always detected by the output level detection circuit 7, and the output detection circuit 7 rectifies the output signal into a DC control voltage and feeds it back to the high frequency amplifier circuit 3 to control the amplification gain. This control operation reduces the gain when the output level is high, increases the gain when the output level is low,
As a result, automatic control is performed so that a signal at a constant level is always output regardless of the input level. The gain control range of this AGC circuit 2 is set in advance, and for example, about 30 [dB] is selected.

The output signal of the intermediate frequency amplification circuit 6, which has been controlled to a constant level by the AGC circuit 2, is applied to the FM detection circuit 8, where it is detected and an audio signal is extracted. and the speaker 11 after being amplified to a predetermined level by the power amplification circuit 10.
is output as audio.

By the way, when using an FM receiver for car use, after selecting broadcast station A, move to another location and place it near the transmitting antenna of broadcast station B, which has a frequency very adjacent to broadcast station A. When passing through the area, the selection of station A may be lost due to the influence of the high-level input signal of station B received by the antenna.For this reason, the gain control range of the AGC circuit 2 is expanded to, for example, 50 Measures have been taken to improve the sensitivity of this receiver by selecting about [dB].

(Problem to be Solved by the Invention) By the way, if you try to improve the sensitivity of the receiver by expanding the gain control range of the AGC circuit 2, noise will be generated from the circuit elements themselves such as transistors and diodes that make up the AGC circuit 2. Since noise is also amplified, there is a problem in that there is a limit to the expansion of the gain control range of the AGC circuit 2.

The present invention has been made in response to the above-mentioned problems.
It is an object of the present invention to provide an antenna sensitivity adjustment device that adjusts antenna sensitivity when the gain control range of an AGC circuit is exceeded.

[Structure of the Invention (Means for Solving the Problems)] In order to achieve the above object, the present invention provides an AGC means for outputting a constant signal to a channel regardless of the level of an input signal received by an antenna, and a preset The present invention is characterized by comprising: AGC level detection means for detecting the output level within the gain control range of the AGC means; and antenna adjustment means for adjusting the antenna height in accordance with the detection result of the AGC level.

(Function) The gain control range of the AGC means is set in advance, and the AGC level detection means always detects whether the AGC output level is within the gain control range.

If the AGC output level exceeds the gain control range,
The GC level detection means controls the antenna adjustment means to adjust the height of the antenna. For example, when the AGC output level exceeds the level of the gain control range, the antenna height is controlled to be lowered, and when it is below the level, the antenna height is controlled to be increased. This adjusts the antenna sensitivity, so the AGC circuit is always controlled to be suppressed to a gain control box/concave circle.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the antenna sensitivity adjustment device of the present invention, in which 1 is an antenna, 2 is an AGC circuit, 3 is a high frequency amplification circuit, 4 is a frequency conversion circuit, 5 is a local oscillation circuit, and 6 is an intermediate Frequency amplification circuit, 7 is output level detection circuit, 8
9 is a low frequency amplification circuit, 10 is a power amplification circuit, and 11 is a speaker.

Reference numeral 12 represents an antenna lifting motor for adjusting the height of the antenna 1, and reference numeral 13 represents a motor control circuit. The antenna lifting motor 12 and the motor control circuit 13 constitute an antenna adjusting means.

14 is an AGC level detection circuit for detecting whether or not the AGC level is within a preset gain control range of the AGC circuit 2; a level setting circuit 15 for setting the level of the gain control range; AG output from 2
Level detection circuit 16 for detecting C level. It is comprised of a comparison circuit 17 that compares each output level of a level setting circuit 15 and a level detection circuit 16.

When the AGC output level detected by the level detection circuit 16 exceeds the level within the gain control range, the comparison circuit 1
7 outputs a first control signal to the motor control circuit 13, and when the AGC level falls below the level of the gain control range, the comparison circuit 17 outputs a second control signal to the motor control circuit 13. When a first control signal is applied, the motor control circuit 13 controls the antenna lifting motor 12 to lower the antenna 1 to a desired height, and when a second control signal is applied, it controls the antenna lifting motor 12 to lower the antenna 1 to a desired height. The antenna 1 is raised to a desired height by controlling the motor 12. When the antenna 1 is lowered, the reception sensitivity of the antenna decreases, and therefore the level of the gain control range also decreases. Furthermore, as the antenna rises, the receiving sensitivity improves, so the level of the gain control range also improves. The height to which the antenna 1 is lowered or raised is set in advance.

Next, the operation of this embodiment will be explained.

For example, if the level of the gain control range of the AGC circuit 2 is 30 [d
B], and the FM receiver starts reception. Here, if the AGC output level of AGC circuit 2 exceeds the preset 30 [dB],
This output level is detected by the level detection circuit 16 and applied to the comparison circuit 17. On the other hand, since the level of 30 [dB] preset in the level setting circuit 15 is added to the comparison circuit 17, the comparison circuit 17 compares both levels and indicates that the detected level is higher than the set level. A first control signal is output to the motor control circuit 13. As a result, the motor control circuit 13 controls the antenna lifting motor 12 to lower the antenna from its previous height to a desired height. As a result, the reception sensitivity of the antenna decreases, so the output level within the gain control range of the AGC circuit 2 also decreases and can be suppressed to 30rdB or less.

On the other hand, the output level of the AGC circuit 2 is set to 30
[dB], the comparator circuit 17 compares the detected level with the set level and sends a second control signal to the motor control circuit 13, which means that the detected level is smaller than the set level. Output to. As a result, the motor control circuit 13 controls the antenna lifting motor 12 to raise the antenna 1 from its previous height to a desired height. As a result, the reception sensitivity of the antenna is improved, and the output level of the gain control range of the AGC circuit 2 is also improved to approach 30 [dB].

Thereafter, similar control operations are repeated according to the detection result of the output level of the AGC circuit 2, and by adjusting the antenna sensitivity, the AGC circuit 2 is controlled so as to always fall within the gain control range. Note that when the detection level is equal to the set level, the antenna 1 is controlled to maintain the same height.

According to this embodiment, even if the gain control range of the AGC circuit is limited to a certain level due to noise generation in the circuit elements, if this limit range is exceeded, the antenna sensitivity is adjusted to limit the gain control range. Since the noise is suppressed within the range of 100 to 100%, it is possible to prevent unnecessary noise from occurring.

The present invention is particularly effective when applied to areas where many FM broadcast stations are adjacent to each other, such as in Europe and America.

In addition, although this embodiment has been explained using an FM receiver as an example,
It can be similarly applied to AM receivers. Also AG
The C control voltage is not limited to the output level of the intermediate frequency amplifier circuit;
It may be obtained by detecting the output level of the detection circuit. Furthermore, if the antenna is raised more than necessary regardless of the driver's intention, it is possible that the antenna will come into contact with an obstacle, but this can be solved by setting the upper limit amount in advance.

[Effects of the Invention] As described above, according to the present invention, even if the gain control range of the AGC circuit is limited, the antenna sensitivity is adjusted to always be suppressed within the limit, thereby eliminating unnecessary noise from the circuit elements. Amplification can be prevented and proper AGC operation can be performed.

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating an embodiment of the antenna sensitivity adjustment device of the present invention, and FIG. 2 is a block diagram of a conventional example. 1... Antenna, 2... AGC circuit, 12
... Antenna lifting/lowering motor, 13... Motor control circuit, 14... AGC output level detection circuit, 15... Level setting circuit, 17... Comparison circuit. Figure 2

Claims (1)

[Claims] AGC means that always outputs a signal at a constant level regardless of the input signal level received by the antenna, and an AG that detects the output level within a preset gain control range of the AGC means.
An antenna sensitivity adjustment device comprising a C level detection means and an antenna adjustment means for adjusting the antenna height according to the detection result of the AGC level.