JPS58170230A - Receiver - Google Patents

Abstract

PURPOSE:To operate a main PIF amplifier having an AGC function normally, by providing the AGC function for an intermediate frequency preamplifier, compressing the fluctuation of an input level and taking the maximum value of the input level of the main IF amplifier to a prescribed level or below. CONSTITUTION:The IF preamplifier 5' is provided between a reception mixer 4 and an IF BPF6, the amplifier 5' has a variable attenuation element 11 between amplifier elements 9 and 10, an output is obtained at the element 10 and a part of the output is sent to an output level detection circuit 12. In this case, the signal of the circuit 12 is applied to a control circuit 13, the output of which adjusts the bias current of PIN diode of the variable attenuation element 11 inserted in series between the amplifier element 9 and 10, for example, allowing to provide the AGC characteristics. As the range of the AGC, when the input level is higher than the standard level, the bias current of the PIN diode i s changed so that the output level is the same as that at the standard level.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a receiver of a single multiplex radio device, and even if a level diaphragm is configured to improve the noise figure, the main intermediate frequency is The present invention relates to a receiver that can reduce the input level of a neutralizer to a predetermined value or less.

(1+1 Prior Art and Problems Figure 1 is a block diagram of a receiver of a conventional multiplex radio device (
A) and a level diagram (B).

In the figure, 1 is an antenna, 2 is a high frequency amplifier, 3 is a high frequency bandpass filter (hereinafter referred to as high frequency BPF), 4 is a receiving mixer,
5 is a pre-intermediate frequency filter, and 6 is an intermediate frequency bandpass filter (hereinafter referred to as intermediate frequency BPF).

7 is a main intermediate frequency amplifier, and 8 is a local oscillator.

As shown in FIG. 1, when a radio wave is received by an antenna 1, a high frequency intermediate device 2. It becomes an intermediate frequency band at the reception mixer 4 via the high frequency BPF 3, and becomes a pre-intermediate frequency ring filter 5. intermediate frequency BP
It is input to the main intermediate frequency amplifier 7 via F6. Up to this point (
As shown in the level diagram shown in B), the standard level input to the high frequency amplifier 2. The maximum incoming call level changes linearly depending on the minimum incoming call level.

The main intermediate frequency amplifier 7 has an automatic gain control (hereinafter referred to as AGC) function, and controls the output level to be constant despite input fluctuations.

However, in order to improve the noise figure, on the level diagram,
The input level of the main intermediate frequency amplifier 7 cannot be configured unless it is set to a certain level 8 or higher in a state close to the maximum incoming call level.

When the input level of the main intermediate frequency amplifier 7 exceeds a certain level a, self-bias is applied to the variable gain element used for AGC, and the AGC operation becomes abnormal and the main intermediate frequency amplifier 7 There are drawbacks such as overload and increased harmonic distortion.

(C) Object of the Invention The object of the present invention is to solve the above-mentioned drawbacks. Even in a level diagram constructed to improve the noise figure, it is possible to calculate the maximum value of the input level of the main intermediate frequency amplifier.

The purpose of the present invention is to provide a receiver capable of transmitting signals below a predetermined level.

(d) Structure of the Invention In order to achieve the above object, the present invention provides a pre-intermediate frequency amplifier with an AGC function to compress input level fluctuations and reduce the maximum input level of the main intermediate frequency amplifier. The present invention is characterized in that the value is set below a predetermined level so that the main intermediate frequency amplifier having an AGC function can operate normally.

tel　Embodiments of the invention One embodiment of the present invention will be explained below with reference to the drawings. Ru.

FIG. 2 is a circuit block diagram of a pre-intermediate frequency amplifier according to an embodiment of the present invention, and FIG. 3 is a block diagram (A) and a level diagram (B) of a receiver of a multiplex radio device according to an embodiment of the present invention.
).

In the figure, parts with the same functions as those in FIG. 1 are indicated by the same symbols. 5 is a pre-intermediate frequency amplifier, 9.10 is an amplifying element, 11 is a variable attenuation element, 12 is an output level detection circuit, and 13 is a control circuit.

The conditions required for the receiver to have a good noise figure and operate normally are the input level f) of the main intermediate frequency amplifier 7.
When the Nk large incoming call level is below a certain level a (same as the standard level) and the 9 incoming call level is low, the same level as in the conventional example may be used. Therefore, when the input level is higher than the standard level, A
It may be one that performs GC operation, or one that has a simple AGC function.

A pre-intermediate frequency amplifier is generally composed of two stages of amplifier elements. Therefore, the embodiment shown in FIG. 2 is applicable to the case of two stages of amplifying elements.

The operation is performed by the output level detection circuit 12.

The output level is detected and detected and added to the control circuit 13.

At this output, add an amplifying element 9, for example a PIN diode.
AGC characteristics are obtained by varying the bias current of a PIN diode of a variable attenuation element 11 inserted in series between 10 and 10. Of course, within the AGC range.

When the input level is higher than the standard level, the bias current of the PIN diode may be varied so that the output level is the same as that at the standard level.

As shown in FIG. 3(A), a receiver using such a prefix intermediate frequency amplifier 5 having an AGC function is different from the conventional receiver except that the prefix intermediate frequency amplifier 5 is changed. are the same. The level diagram of this receiver is shown in FIG. 3(B).

The input level up to the pre-intermediate frequency amplifier 5 is made equal to that of the conventional system. When the input level is below the standard level, there is no AGC operation, the level diagram is the same as before, and there is no change in the operation of the receiver.

Therefore, the input level of the main intermediate frequency amplifier 7 will not be higher than the standard level even if the noise figure is improved.
It is below a certain level a. Therefore, the variable gain element will not be self-biased and the AGC operation will not become abnormal.
There will be no overload and no increase in modulated wave distortion.

<f) Effects of the Invention As described in detail above, according to the present invention, the noise figure of the receiver of a multiplex radio device is improved.

Even at the maximum incoming call level, the AGC of the main intermediate frequency amplifier
There is an advantage that the operation will not become abnormal, and the modulated wave distortion will not increase due to overload.

[Brief explanation of the drawing]

FIG. 1 is a block diagram and level diagram of a receiver of a conventional multiplex radio device, FIG. 2 is a block diagram of a circuit of a pre-intermediate frequency amplifier according to an embodiment of the present invention, and FIG. 2 is a block diagram and a level diagram of a receiver of a multiplex radio device according to an embodiment; FIG. In the figure, 1 is the antenna, 2 is the high frequency terminator, and 3 is the high frequency BP.
F, 4 is a receiving mixer, 5.5 is a pre-intermediate frequency term intermediater, 6
is an intermediate frequency BPF, 7 is a main intermediate frequency term intermediate device, 8 is a local oscillator, and 9.10 is a term intermediate element. 11 is a variable attenuation element, and 12 is an output level detection circuit. 13 indicates a control circuit. Procedural amendment (formality) - Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office 1. Indication of 1.A'1 1989 Patent application No. Address 1015 Naka Elementary School, Nakahara Ward, Yozaki City, Kanagawa Prefecture (
522) Name Fujitsu Ltd. 8 Supplement 11 Contents: Engraving of the description (no change in content) Procedural amendment (voluntary), 8. Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office!, Indication of the case, 1939 Patent Application No. 3oof, No. 2, Title of the invention: ``OI''. 3. Relationship with the case by the person making the amendment. Address of the patent applicant, Kanagawa Prefecture. Nakahara Ward, Yozaki City” - 1015 Koennaka (
522) Name Fujitsu Limited

Claims (1)

[Claims] In a receiver of a multiplex radio device having a front intermediate frequency tank intermediate unit and a main intermediate frequency amplifier having an automatic gain adjustment function,
A receiver characterized in that the front intermediate frequency tank intermediate unit also has an automatic gain adjustment function.