JPH0342758Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a diversity receiving device for wireless communication. In particular, the present invention relates to a diversity receiving device that receives and demodulates frequency modulated waves. This invention is used for spatial diversity.

〔overview〕

The present invention improves the signal-to-noise ratio (hereinafter referred to as
It's called S/N. ), the S/N was noticeably lower than that of the other.
The control voltage of the voltage-controlled variable phase shift oscillator for local oscillation of channels with good S/N is automatically fixed when the local oscillation of channels with extremely low S/N is reduced to good S/N. By controlling the signal to be synchronized with the phase of the /N channel, a decrease in the S/N of the demodulated signal after synthesis is prevented, and the burden on the operator such as complicated operations and continuous monitoring of the reception status is eliminated. , to ensure stable operation.

[Conventional technology]

When receiving frequency modulated waves, conventional diversity receiving devices directly phase detect the signals of two channels (channel A and channel B) at an intermediate frequency stage, convert the phase difference information into voltage, and detect the signals in the same phase. For synthesis, a system that controls the phase of the output signal of a voltage-controlled variable phase shift oscillator or a voltage-controlled oscillator is mainly adopted. The frequency modulated wave is demodulated by using a frequency discriminator or other required method on the synthesized input signal.

[Problem that the invention attempts to solve]

However, in such a conventional diversity receiving device, the difference in S/N (difference in input level) between the input signals of channel A and channel B is, for example, 20 dB.
In the above case, the S/N of the phase detection output mentioned above is
is determined by the S/N of a channel with a low S/N, and the output signal phase of a voltage-controlled variable phase shift oscillator or a voltage-controlled oscillator of a channel with a good S/N is determined by the S/N.
Even though the signal was good, it was affected by the S/N of the channel with a low S/N, resulting in a phenomenon that resulted in deterioration of the S/N of the demodulated signal after synthesis. To prevent this, with conventional devices, the operator constantly monitors the reception status of both channels and manually disconnects the phase detector input of the channel with a low S/N, making the operation extremely complicated. There were flaws.

The present invention solves the above-mentioned drawbacks. It prevents deterioration of the S/N of the demodulated signal after synthesis, eliminates the burden on the operator such as complicated operations and continuous monitoring of the reception status, and provides stable operation. An object of the present invention is to provide a diversity receiving device that can obtain the following characteristics.

[Means for solving problems]

The present invention consists of two mixers 12, each inputting two channels of input signals and outputting an intermediate frequency signal.
32, and two voltage-controlled variable phase-shift oscillators 2 that supply local oscillation frequency signals to these two mixers so that the phases of their output signals are synchronized.
4, 44, a phase detector 51 that detects the phase difference between the output signals of the two mixers, and a phase detector 51 that determines the oscillation frequency of the two voltage-controlled variable phase shift oscillators based on the detection output of the phase detector. In a diversity receiving device comprising two control circuits each providing a control voltage to be controlled, and means for fixing the control voltages, the fixing means detects a difference in signal-to-noise ratio between the input signals of the two channels. and a comparison means for determining whether this difference exceeds a considerably large predetermined value, and a control voltage for the channel with a better signal-to-noise ratio of the input signals of the two channels based on the determination result of the comparison means. and switching means for fixing the.

[Effect]

The comparing means detects the S/N difference (difference in logarithmic value) between the input signals of the two channels, and determines whether or not this S/N difference exceeds a predetermined value. Based on the determination result of the comparing means, the switching means automatically fixes the control voltage of the voltage-controlled variable phase shift oscillator of the channel with a good S/N, and controls the local oscillation of the channel with a low S/N. To synchronize a channel with a low S/N to the phase of a channel with a good S/N. The above operation prevents a drop in the S/N of the demodulated signal after synthesis without losing data, and provides stable operation without burdening the operator with complicated operations and continuous monitoring of the reception status. .

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

The figure is a block diagram of a diversity receiving apparatus according to an embodiment of the present invention. Input signals of channels A and B from outside the figure are input to input terminals 11 and 31, respectively. Input signals from input terminals 11 and 31 are connected to inputs of mixers 12 and 32, respectively. First intermediate frequency signals whose phases are controlled to be synchronized from the mixers 12 and 32 are connected to inputs of automatic gain control amplifiers 13 and 33, respectively, and automatic gain control signals are connected to control inputs of the first intermediate frequency signals. The frequency signal is amplified. The outputs of automatic gain control amplifiers 13, 33 are connected to the inputs of mixers 14, 34, respectively. Further, a second local oscillation signal is connected to the local oscillation signal input of the mixers 14 and 34 from outside the figure. The second intermediate frequency signals from mixers 14 and 34 are passed through bandpass filters 15 and 35 to limiters 16 and 3, respectively.
6 and the input of synthesizer 52.

In the synthesizer 52, the second intermediate frequency signals of channels A and B are combined and connected to a demodulator 54 via a bandpass filter 53, and the signal demodulated by the demodulator 54 is connected to an output terminal 55 and output. A demodulated signal is sent from terminal 55.

The outputs of limiters 16 and 36 are connected to the inputs of phase detector 51, respectively. The phase detector 51 detects the phase difference between the second intermediate frequency signals of channels A and B. The phase difference detected from the phase detector 51 is detected by the non-inverting amplifier 21 and the inverting amplifier 4, respectively.
1 input, respectively.

Here, the feature of the present invention is the switch opening/closing control portion surrounded by a dashed line. That is,
The outputs of non-inverting amplifier 21 and inverting amplifier 41 are connected to inputs of voltage-controlled variable phase shift oscillators 24 and 44 via switches 22 and 42, respectively. Voltage controlled variable phase shift oscillator 24, 4
The output of No. 4 (first local oscillation signal) is sent to mixer 12, 3.
mixer 12,
32 is phase controlled.

The S/N ratios of the input signals of channels A and B are connected to the inputs of comparators 25 and 45, respectively. In comparators 25 and 45, channel A,
The S/N difference of the B signal is detected, and the detection results are sent from the comparators 25 and 45 to the converters 26 and 45, respectively.
46 inputs. The outputs of the converters 26 and 46 control the "on" and "off" states of the switches 22, 23, 42, and 43, respectively. That is, if the difference in S/N between the two channels exceeds a predetermined value, and the channel with the better S/N is channel A, the switch 22 is opened and the voltage-controlled variable phase shift oscillator 24 is turned on. The inputs are connected via switch 23 to a common potential. The switch 42 of channel B with a low S/N remains closed and the switch 43 remains open. When the channel with good S/N is channel B, the switch 42 is opened and the input of the voltage controlled variable phase shift oscillator 44 is connected to the switch 43.
connected to a common potential via. The switch 22 of channel A with a low S/N remains closed and the switch 23 remains open.

The operation of the diversity receiving device having such a configuration will be explained. In the figure, when the signals of channel A and channel B, which have different S/N ratios, are input, the comparators 25 and 45
(difference in input level), and if the value obtained by subtracting the S/N of the input signal of channel B from the S/N of the input signal of channel A exceeds a predetermined value,
Control signals are output from the comparators 25 and 45, and the converters 26 and 46 open the switches 22 and 43, close the switches 23 and 42, and control the voltage of the voltage-controlled variable phase shift oscillator 24 of channel A. is set to zero, and the voltage controlled variable phase shift oscillator 44 of channel B is set to zero, and the voltage controlled variable phase shift oscillator 44 of channel B is set to
synchronize to the phase of Therefore, the phase detector 5
1 becomes zero, the phases of each input channel of the combiner 52 become in-phase, and deterioration of the S/N after combining is automatically prevented according to the difference in S/N of the input signals.

Next, if the value obtained by subtracting the S/N of the input signal of channel A from the S/N of the input signal of channel B exceeds a predetermined value, the comparators 25 and 45
A control signal is output from the converters 26 and 46 to close the switch 22 and the switch 43,
Switch 23 and switch 42 are opened to set the control voltage of channel B voltage-controlled variable phase-shift oscillator 44 to zero, and channel A voltage-controlled variable phase-shift oscillator 24 is synchronized with the channel B phase.

[Effect of idea]

As explained above, the present invention enables the demodulated signal to be synchronized to the phase of the channel with good S/N even when the S/N of one of the input signals of both channels is significantly degraded. This has the excellent effect of preventing a drop in the S/N of the receiver, eliminating the burden on the operator such as complicated operations and continuous monitoring of the reception status, and providing stable operation.

[Brief explanation of the drawing]

The figure is a block diagram of a diversity receiving device according to an embodiment of the present invention. 11, 31...input terminal, 12, 14, 32,
34... Mixer, 13, 33... Automatic gain control amplifier, 15, 35, 53... Bandwidth wave generator, 16,
36... Limiter, 21... Non-inverting amplifier, 41
... Inverting amplifier, 24, 44 ... Voltage controlled variable phase shift oscillator, 25, 45 ... Comparator, 2
6, 46...Converter, 51...Phase detector, 52
...Synthesizer, 54...Demodulator, 55...Output terminal.

Claims (1)

[Claims for Utility Model Registration] Two mixers 12 and 32 which each input two channels of input signals and output an intermediate frequency signal, and a local oscillation device so that the phases of the output signals of these two mixers are synchronized. Two voltage-controlled variable phase shift oscillators 24, 44 each providing a frequency signal.
and a phase detector 51 that detects the phase difference between the output signals of the two mixers, and control that controls the oscillation frequency of the two voltage-controlled variable phase shift oscillators based on the detection output of the phase detector. In a diversity receiving device comprising two control circuits that respectively apply voltages, and means for fixing the control voltages, the fixing means detects the difference in signal-to-noise ratio of the input signals of the two channels, and detects the difference in signal-to-noise ratio of the input signals of the two channels. a comparison means for determining whether the difference exceeds a predetermined value which is considerably large; and a control voltage for the channel having a better signal-to-noise ratio of the input signals of the two channels is fixed based on the determination result of the comparison means. 1. A diversity receiving device comprising: switching means.