JPH04344721A - In-phase synthesizer receiver - Google Patents

Abstract

PURPOSE:To improve the S/N after in-phase synthesizing by providing a means increasing the attenuation when an input signal is small and decreasing the attenuation when the input signal is large on the other hand to the pre-stage of a synthesizer. CONSTITUTION:Both a main and a subsignal are amplified by a gain ' matching a high input level and mixers 4,5, an oscillator 6, an endless phase shifter 7 and an endless phase shifter control circuit 19 convert the main and the subsignals into a signal at an intermediate frequency band in-phase. Then a voltage controlled amplifier composed of an amplifier 8 (9), a voltage controlled attenuator 12 (13) and an amplifier 10 (11) is provided to a pre-stage of a synthesizer 18 at which the main and the sub signals are synthesized as the main and the subside. Moreover, an output level of the amplifiers 8,9 is detected by a detector 14 (15) and a limiter amplifier 16 (17) is provided, which outputs a control signal to decrease the attenuation of the attenuator 12 (13) within a prescribed range when the level is larger and to increase the attenuation of the attenuator 12 (13) within a prescribed range when the level is smaller. The synthesis signal is amplified up to a prescribed level by an automatic gain controlled intermediate frequency amplifier circuit 20.

Description

[Detailed description of the invention]

0001

FIELD OF INDUSTRIAL APPLICATION The present invention is utilized in a space diversity receiver for microwave wireless communication equipment. In particular, it relates to its in-phase synthesis means.

0002

[Prior Art] As shown in FIG. 2, in a conventional example, a radio frequency amplifier control circuit 3 detects the levels on the main side and the sub side, outputs a control signal to match the high level signal, and outputs a control signal to match the high level signal. Depending on the control signal, the automatic gain control type radio frequency amplifiers 1 and 2 amplify the main side and sub side signals with the same gain, and the main side is converted into an intermediate frequency band signal by the oscillator 6 and mixer 4. On the sub side, an infinite phase shifter control circuit 19 detects the phase difference between the main side and the sub side, and the output signal controls the infinite phase shifter 7, and the mixer 5 detects the phase difference between the main side and the sub side. The signal is converted into a signal, subjected to in-phase synthesis by a synthesizer 18, and amplified to a certain level by an automatic gain control type intermediate frequency amplification circuit 20.

0003

As described above, in the conventional example, since amplification is performed with the same gain regardless of the difference between the inputs on the main side and the sub-side, there is a risk that the S/N ratio will deteriorate.

SUMMARY OF THE INVENTION The present invention aims to eliminate such drawbacks and provides an in-phase combining receiver having means for improving the SN ratio after in-phase combining.

[0005]

[Means for Solving the Problems] The present invention provides two antennas that receive the same microwave at different positions, two radio frequency amplifiers provided corresponding to the antennas and having the same gain, and two radio frequency amplifiers that receive the same microwave at different positions. An in-phase synthesis receiver comprising a conversion means that generates two intermediate frequency signals in the same phase corresponding to a signal output from a frequency amplifier, and a synthesizer that synthesizes signals related to the two intermediate frequency signals generated by the conversion means. The apparatus includes a detector for detecting the input level of each of the two intermediate frequency signals generated by the converting means, an amplifier for converting the signal output from the detector into a control signal, each of the converting means and the above. The present invention is characterized in that it includes a voltage-controlled attenuator that is provided in a path between the synthesizer and the synthesizer and whose attenuation amount changes according to a control signal generated by the amplifier.

[0006]

[Operation] Converts the radio frequency signals arriving at the two antennas into in-phase intermediate frequency signals, detects the level of this intermediate frequency signal, and controls the amount of attenuation so that the smaller the level, the smaller the gain. Perform synthesis. Thereby, the SN ratio after in-phase synthesis can be improved.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of this embodiment. As shown in FIG. 1, this embodiment includes two antennas that receive the same microwave at different positions, and automatic gain control type radio frequency amplifiers 1 and 2 that are provided corresponding to the antennas and have the same gain. a mixer 4 which is a conversion means for generating two intermediate frequency signals in phase corresponding to the signals output from the two automatic gain control type radio frequency amplifiers 1 and 2;
5. The present invention further comprises an oscillator 6, an infinite phase shifter 7, an infinite phase shifter control circuit 19, and a synthesizer 18 for synthesizing signals related to two intermediate frequency signals generated by the converting means. The features include detectors 14 and 15 for detecting the input levels of the two intermediate frequency signals generated by the converting means, and converting the signals output from the detectors 14 and 15 into control signals. Voltage controlled attenuation provided in the path between the limiter-equipped amplifiers 16 and 17, each of the conversion means and the combiner 18, and whose attenuation amount changes according to the control signal generated by the limiter-equipped amplifiers 16 and 17. 12 and 13.

Next, the operation of this embodiment will be explained. Signals between the main side and the sub-side are transmitted by automatic gain control type radio frequency amplifiers 1 and 2.
The radio frequency amplifier control circuit 3 amplifies both the main side and the sub side with a gain suitable for the higher input level, and the mixers 4 and 5, the oscillator 6, the infinite phase shifter 7, and the infinite phase shifter The control circuit 19 converts the main side and the sub side into in-phase intermediate frequency band signals. Next, the main-side and sub-side signals are combined by a combiner 18. Before the combiner 18, both the main-side and sub-side signals are voltage controlled by an amplifier 8, a voltage-controlled attenuator 12, and an amplifier 10. Place the amplifier, amplifier 8
The output level of the voltage control attenuator 12 is detected by the detector 14, and when the detected level is large, the attenuation of the voltage-controlled attenuator 12 is controlled to be small within a certain range, whereas when the level is small, the attenuation is large. Amplifier 1 with limiter that outputs the signal
6 will be provided. The signal synthesized by the synthesizer 18 is amplified to a certain level by an automatic gain control type intermediate frequency amplification circuit 20.

[0009]

[Effects of the Invention] As explained above, the present invention increases the amount of attenuation when the input signal is small, and decreases the amount of attenuation when the input signal is large, at the front stage of the synthesizer that performs in-phase synthesis on both the main side and the sub side. Since the means is provided, there is an effect that the SN ratio is improved.

[Brief explanation of drawings]

FIG. 1 is a block configuration diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a block configuration diagram showing the configuration of a conventional example.

[Explanation of symbols]

1, 2 Automatic gain control radio frequency amplifier 3 Radio frequency amplifier control circuit 4, 5 Mixer 6 Transmitter 7 Infinite phase shifters 8 to 11 Amplifiers 12, 13 Voltage controlled attenuators 14, 15 Detectors 16, 17 Amplifier with limiter 18 Combiner 19 Infinite phase shifter control circuit

Claims (1)

[Claims] [Claim 1] Two antennas that receive the same microwave at different positions, two radio frequency amplifiers provided corresponding to these antennas and having the same gain, and corresponding to signals output from these two radio frequency amplifiers. an in-phase synthesis receiver comprising a converting means for generating two in-phase intermediate frequency signals generated by the converting means, and a synthesizer for synthesizing signals related to the two intermediate frequency signals generated by the converting means; a detector for detecting the input level of each of the two intermediate frequency signals, an amplifier for converting the signal output from the detector into a control signal, and a path between each of the converting means and the synthesizer. and a voltage controlled attenuator whose attenuation amount changes according to a control signal generated by the amplifier.