JPH05218917A - In-phase synthesis system - Google Patents

Abstract

PURPOSE:To improve the frequency characteristic of a signal after synthesis by eliminating the effect of notch. CONSTITUTION:A voltage controlled attenuator 16 (17) is provided between an output terminal of an AGC amplifier 1 (2) and an input terminal of a synthesizer 18, and band pass filters 6, 8, 10, detectors 35, 36, 37, band pass filters 7, 9, 11 and detectors 38, 39, 40 are used to detect a signal level at three points of a low frequency, a medium frequency and a high frequency within a band of an output signal of each AGC amplifier. Then a differential amplifier 41 detects an output signal of a low level from an intermediate frequency signal level, and a level comparator at the output signal side of the low signal level in level comparators 12, 13 compares the level difference of signal levels at the three points within a band of the said output signal with a specified value. When the difference is larger than the specified value, a relevant attenuator in voltage controlled attenuators 16, 17 is controlled to attenuate an output signal of the low signal level. As a result, since a level of a signal receiving the effect of notch in the two inputs to a synthesizer 18 is negligibly low, the frequency characteristic of the signal after synthesis is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-phase combining system in a space diversity receiver.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional in-phase combining method. In FIG. 3, signals received by two receiving systems (not shown) are adjusted in phase to one another, one receiving signal is input to the AGC amplifier 1 via the input terminal M, and the other receiving signal is input to the input terminal S. It is input to the AGC amplifier 2 via.

The AGC amplifiers 1 and 2 have the same structure and have an input stage amplifier 19 (20) and an output stage amplifier 23 (2).
4) and the voltage control attenuator 21 (2
2) and amplifies the input signal with the same gain and outputs the amplified signal to the combiner 18 and the AGC circuit 29. At that time, the attenuation amounts of the voltage control attenuators 21 and 22 are controlled to be the same by the output voltage of the AGC circuit 29.

In the AGC circuit 29, the AGC amplifier 1
The output of the output stage amplifier 23 (24) of (2) is fed to the amplifier 30.
It is amplified at (31) and detected by the detector 32 (33). The detection outputs of the detectors 32 and 33 are respectively input to the control voltage generator 34, where the waveform is subjected to waveform shaping processing to become respective detection voltages, and the detection voltage of a large level is selected as the AGC control voltage, which is passed through the amplifier 35. Voltage control attenuators 21 and 22.

Then, in this way, the A
The output of the GC amplifier 1 (2) is combined by the combiner 18,
It is sent out of the figure through the GC amplifier 3. In addition, AGC
The amplifier 3 includes a voltage controlled attenuator 25, an amplifier 26 and a detector 2
7 and an amplifier 28.

[0006]

In the above-mentioned conventional in-phase combining method, A which is adapted to the higher one of the two input signal levels is used.
Since the attenuation amounts of the two AGC amplifiers are controlled to be the same by using the GC control voltage and combined, the effect of the notch cannot be eliminated when the fading is selective,
As a result, there is a problem that the frequency characteristics of the combined signal deteriorate.

An object of the present invention is to provide a common-mode combining method capable of eliminating the effect of notch of selective fading and improving the frequency characteristics of the combined signal.

[0008]

In order to achieve the above object, the in-phase synthesis system of the present invention has the following configuration. That is, the in-phase synthesis method of the present invention is a phase-adjusted 2
First and second AGC amplifiers for amplifying each of the two input signals with the same gain and receiving the same AGC control signal to form the same amount of attenuation; and outputs of the first and second AGC amplifiers. And a second variable attenuator provided between the output end of the first AGC amplifier and one input end of the combiner, and the second combiner A second variable attenuator provided between the output end of the AGC amplifier and the other input end of the combiner; and three bands in the output signal of the output of the first AGC amplifier, respectively. Three of the first output signals of the first band-pass filter for filtering and the output of the second AGC amplifier are received.
Three second bandpass filters each performing a filtering process in one band; three first detectors each performing a detection process on an output of each of the three first bandpass filters; and Three second detectors that perform detection processing on the outputs of the three second bandpass filters;
Among the outputs of the three first and second detectors, the output levels of the two detectors corresponding to the central band of the three bands are compared, and the AGC control signal is output based on the larger output level. A first level comparator; of the outputs of the three first and second detectors, the output level is set according to the magnitude relationship of the output levels of the two detectors corresponding to the central band of the three bands. An inverting differential amplifier; 3
When the output levels of the differential amplifiers are compared with each other, the output levels of the first differential detector are compared and the first variable attenuator performs the attenuation operation when the level difference between them exceeds a predetermined value. The output level of the second level comparator and the output level of the three second detectors which are performed at a certain time are compared, and when the level difference between them exceeds a predetermined value, the second variable attenuator is attenuated. And a third level comparator for performing the operation when the output level of the differential amplifier is the other level.

[0009]

Next, the operation of the in-phase synthesizing method of the present invention configured as described above will be described. In the present invention, the first (second) A
A first (second) variable attenuator is provided between the output end of the GC amplifier and the input end of the combiner, and the signal levels in three bands in the output signal of each AGC amplifier are detected (first and second). Operation of the second bandpass filter, the first and second detectors). Then, the attenuation amount of each AGC amplifier is controlled by the larger signal level in the central band of the three bands (operation of the first level comparator). On the other hand, which of the output of the first AGC amplifier and the output of the second AGC amplifier is at a low level is detected from the magnitude relationship of the signal level in the central band (operation of the differential amplifier), and the low level is detected. When the difference between the signal levels in the three output bands exceeds the predetermined value, the corresponding variable attenuator is controlled to attenuate the output signal (operations of the second and third level comparators) and combined. ..

As a result, the signal affected by the notch of the selective fading is synthesized in a negligible state, that is, the effect of the notch can be removed, so that the frequency characteristic of the synthesized signal can be improved.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an in-phase combining method according to an embodiment of the present invention. In the present invention, in the conventional configuration (FIG. 3), the voltage-controlled attenuator 1 which is the first variable attenuator is provided between the output end of the (first) AGC amplifier 1 and one input end of the combiner 18.
6 is provided, a voltage control attenuator 17 which is a second variable attenuator is provided between the output end of the (second) AGC amplifier 2 and the other input end of the combiner 18, and the AGC circuit 29 is provided. Instead, the bandpass filter (6-11) and the detector (35-4)
0), a level comparator (12-14), an amplifier 15 and a differential amplifier 41 are provided. Hereinafter, the description will focus on the part relating to the present invention.

Three (first) bandpass filters (6, 8, 10) provided on the output side of the AGC amplifier 1, and
Three (second) provided on the output side of the AGC amplifier 2
As shown in FIG. 2, the band pass filter (7, 9, 11) has three bands (a low band side predetermined band, a center band predetermined band, and a high band) in the output signal of the AGC amplifier 1 (2). (A predetermined band on the side). In the illustrated example, the band-pass filter 6 (7) is in a predetermined band on the low frequency side, the band-pass filter 8 (9) is in a predetermined band in the central region, and the band-pass filter 10 (11) is high. A filtering process is performed in each predetermined band of the region.

The output of the bandpass filter (6, 8, 10) is fed to the (second) level comparator 12 via three (first) detectors (35, 36, 37). The output of the band-pass filter (7, 9, 11) is given to the (third) level comparator 13 via the three (second) detectors (38, 39, 40). Further, the output of the band pass filter 8 (9) that performs the filtering process in the central predetermined band is the detector 36 (3
9) to the (first) level comparator 14 and the differential amplifier 41.

The level comparator 14 has the same detector 39 as the detector 36.
The output detection voltage levels are compared with each other, and the detection voltage having the higher level is sent to the amplifier 15 to form an AGC control voltage for simultaneously controlling the voltage controlled attenuator 21 (22) of the AGC amplifier 1 (2). That is, the AGC amplifier 1 (2) operates with a gain adjusted to the one having a larger input level as in the conventional case, and the output signal thereof is the voltage controlled attenuator 16 of the present invention.
It is input to the combiner 18 via (17) and combined. Here, the control of the voltage controlled attenuator 16 (17) of the present invention is performed as follows.

In the illustrated example, the differential amplifier 41 is provided with the output detection voltage of the detector 36 at the + (plus) side input terminal,
Since the output detection voltage of the detector 39 is applied to the- (minus) side input terminal, when the output detection voltage of the detector 36 is smaller, the output level is set to a negative level and the output detection voltage of the detector 39 If it is smaller, set the output level to the positive level. In other words, which of the output signal level of the AGC amplifier 1 and the output signal level of the same 2 is smaller is detected.

The level comparator 12 operates as follows when the output level of the differential amplifier 41 is a negative level, and the level comparator 13 operates as follows when the output level of the differential amplifier 41 is a positive level. Comparator 13 is voltage controlled attenuator 1
6, the level comparator 13 controls the voltage control attenuator 17, respectively.

That is, the level comparator 12 is a detector (35,
36, 37), the level comparator 13 receives the output detection voltages of the detectors (38, 39, 40), compares the levels, and determines the level difference between the output detection voltages. When the value exceeds the value, a control voltage for increasing the amount of detection of the voltage controlled attenuator 16 (17) is output.

In summary, the signal levels at three points in the band of the output signal of the AGC amplifier 1 (2), that is, the low band, the middle band, and the high band are detected, and the output signal of the low signal level is output from the mid band signal level. If the level difference between the signal levels at the three points within the band of the output signal of the low signal level is large, it is judged that the influence of the notch is large, and the output signal is greatly attenuated. As a result, of the two inputs of the combiner 18, the signal affected by the notch becomes a negligibly low level, and the frequency characteristics of the combined signal are improved.

[0019]

As described above, according to the in-phase combining method of the present invention, the first (second) part is provided between the output end of the first (second) AGC amplifier and the input end of the combiner. A variable attenuator is provided and the signal level in three bands in the output signal of each AGC amplifier is detected. While the attenuation amount of each AGC amplifier is controlled by the one having the higher signal level in the central band of the three bands, the output of the first AGC amplifier and the second AG are controlled from the magnitude relationship of the signal levels in the central band.
Detect which of the output of C amplifier is low level,
When the difference between the signal levels in the three bands in the low level output signal exceeds a predetermined value, the corresponding variable attenuator is controlled to attenuate and synthesize the output signal. Signals affected by are combined in a negligible state, that is, the effects of notches can be removed, and the frequency characteristics of the combined signals can be improved.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of an in-phase combining system according to an embodiment of the present invention.

FIG. 2 is a relational diagram between the band of the output signal of the AGC amplifier 1 (2) and three (first and second) band pass filters.

FIG. 3 is a configuration block diagram of a conventional in-phase combining method.

[Explanation of symbols]

 1-3 AGC amplifier 6-11 Band pass filter 12-14 Level comparator 15 Amplifier 16 Voltage control attenuator 17 Voltage control attenuator

Claims (1)

[Claims] 1. Amplifying each of two input signals whose phases are adjusted to the same phase with the same gain, and the same AGC.
First and second receiving the control signal and forming the same attenuation amount
An AGC amplifier; and a combiner for combining the outputs of the first and second AGC amplifiers; and an in-phase combining method, wherein: an output end of the first AGC amplifier and one input end of the combiner; A first variable attenuator provided between the second AGC amplifier and a second variable attenuator provided between the output end of the second AGC amplifier and the other input end of the combiner; Receives the output of the amplifier and performs filtering processing in each of the three bands in the output signal 3
Two first band-pass filters, and three second band-pass filters that receive the output of the second AGC amplifier and perform filtering processing in each of the three bands in the output signal; Three first detectors that perform detection processing on the outputs of the three first band-pass filters, and three detection units that perform detection processing on the outputs of the three second band-pass filters. A second detector; comparing the output levels of the two detectors corresponding to the central band of the three bands among the outputs of the three first and second detectors, and based on the larger output level A first level comparator for outputting the AGC control signal; and a level of output levels of two detectors corresponding to a central band of the three bands among outputs of the three first and second detectors. Differential that inverts the output level according to the relationship An output of the differential amplifier for comparing the output levels of the three first detectors and causing the first variable attenuator to perform an attenuation operation when the level difference between the three first detectors exceeds a predetermined value. A second level comparator which is operated when the level is one level, and the second variable when the output levels of the three second detectors are compared and the level difference between them exceeds a predetermined value A third level comparator for causing the attenuator to perform the attenuation operation when the output level of the differential amplifier is the other level;