JPH04262628A - Space diversity reception system - Google Patents

Abstract

PURPOSE:To eliminate switching noise of a changeover device in the space diversity reception system in which reception levels from two systems of antennas are compared by a comparator and the reception signal with a higher reception level is selected by the changeover device. CONSTITUTION:An ON/OFF output signal of a comparator 1 from the result of comparison of levels of reception signals is inverted and used for level adjustment or either of the two same DC levels is selected by other changeover device 6 by using the ON/OFF output signal and added to the reception signal selected by a changeover device 2 to cancel switching noise of the changeover device 2 itself.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a space diversity reception system, and more particularly to a space diversity reception system in which a received signal having a higher reception level from two antenna systems is selected.

[0002] Space diversity reception methods can be roughly divided into two types: (1) a method in which the received signal from the two antenna systems is detected with a higher reception level and the received signal is selected; and (2) a method in which the received signals from the two antenna systems are in the same phase. There are two methods of controlled synthesis, and various research is being carried out on each method. However, from the point of view of simplicity of configuration, method (2), which does not require in-phase synthesis, is better than method (2). preferable.

0003

2. Description of the Related Art FIG. 5 shows the configuration of a conventional space diversity reception system, and FIG. 6 shows its operating waveform diagram. In these figures, the reception levels of the reception signals A and B of antennas ■ and antenna ■ are detected by receivers RX1 and RX2, and these are compared by comparator 1 to provide waveform C in FIG. 6 to switch 2. . This waveform C is “
When the level of the received signal B of the antenna (■) is higher, the level becomes "L".As a result of this comparison, the switch 2 selects the received signal A or B according to the waveform C, and the bandpass It is output from the filter (BPF) 10.

0004

[Problems to be Solved by the Invention] In the case of such a conventional example, the switching operation of the switch 2 is caused by fading, so it is not known when it will be needed, and even at the time of switching, the received signal is continuous. , waveform D output from switch 2
is the received signal A with the same modulation signal as shown in FIG.
, B, there is a problem in that even if the reception levels are the same, they fluctuate up and down at the time of switching due to switching noise caused by the switch.

[0005] Therefore, the present invention solves the switching noise of the switch in a space diversity reception system in which the reception levels from two antenna systems are compared by a comparator and the received signal with the higher reception level is selected by the switch. The purpose is to remove.

[0006]

[Means for Solving the Problems] In order to achieve the above object, a space diversity reception system according to the present invention has the following features:
As conceptually shown in FIG. 1, there is an inverter 3 that inverts the on/off output signal of the comparator 1, and a level adjustment section that generates a signal at a level that cancels out the switching noise of the switch 2 at the timing of the inverter 3. 4, and an adder 5 that adds the output signal of the level adjuster 4 and the received signal selected by the switch 2 to cancel the switching noise of the switch 2.

Furthermore, in the present invention, as shown by the dotted line in FIG. 1, one of the two same DC levels is selected by the on/off output signal of the comparator 1 instead of the inverter 4 and the level adjustment section 4. A second switch 6 may also be provided.

[0008]

[Operation] The operation of the space diversity reception system according to the present invention shown in FIG. 1 will be explained with reference to the waveform diagram in FIG. 4, the signal c is level-adjusted according to the on/off timing of the signal b and is applied to the adder 5. The level adjustment in the level adjustment section 4 is adjusted so that a signal c is generated that cancels out the switching noise (switching fluctuation amount) generated in the switch 2, so the addition or subtraction is performed in the addition section 5 to switch. An output signal e from which time fluctuation components have been removed is obtained as a received signal.

On the other hand, in such an output signal e, although the fluctuation component at the time of switching is removed, there is a "whisker" as shown in the figure.
remains.

Therefore, in the present invention, another switch 6 shown by a dotted line in FIG.
Output. In this case, since the two DC levels of the switch 6 are both the same level (a), if the switching operation is performed at the on/off timing of the output signal a of the comparator 1, the result will be as shown in FIG. A signal c' consisting only of switching noise and whiskers is given to the adder 5.

By adding or subtracting the output signal c' from the switch 6 with the signal d from the switch 2, the whiskers of the signal d are also canceled, resulting in a smooth signal e'.
will be output as a received signal.

0012

[Embodiment] FIG. 3 shows an embodiment of the space diversity reception method according to the present invention.
A bias consisting of a capacitor c1 that cuts DC components between the receiver RX1 and the switch 2, and series resistors r1 and r2 that eliminate rising and falling of the capacitor c1 by constantly applying a bias voltage to the capacitor c1. The circuit is inserted in series, and
Similarly, a bias circuit consisting of a capacitor c2 for cutting DC components and series resistors r3 and r4 is inserted in series between the receiver RX2 and the switch 2. Furthermore, switch 2
A bias circuit consisting of series resistors r5 and r6 and a capacitor c for cutting the DC component are also connected between the and the adder 5.
1 are inserted in series. Further, the level adjustment section 4 is composed of a variable resistor r7 that makes the output signal of the inverter 3 variable and a capacitor c4 that cuts the DC component, and the addition section 5 includes capacitors c3 and c4, respectively. The connected input resistors r8 and r9, an operational amplifier 50 which commonly inputs each output signal of these resistors r8 and r9 to an inverting input terminal, a feedback resistor r9 of this operational amplifier 50, and a reference voltage Vr are calculated. It is configured with an input resistor r10 for inputting to the non-inverting input terminal of the amplifier 50.

In such a configuration, the comparator 1 inputs the demodulation levels of the receivers RX1 and RX2, compares which level is higher, and outputs the resulting signal a (FIG. 2).
) is inverted by the inverter 3 and becomes the signal b. The level of this signal b is adjusted by a variable resistor r4, and the DC component is cut by a capacitor c2, and then the operational amplifier 50
is sent to the inverting input terminal of

On the other hand, the output signal d of the switch 2 generates switching noise as shown in FIG. When applied to the operational amplifier 50 via r8 and applied to the inverting input terminal of the operational amplifier 50 together with the output signal c of the level adjustment section 4 via the resistor r9,
Since the output signal c of the level adjustment unit 4 is initially set so as to cancel out the level fluctuation at the time of switching of the output signal d by adjusting the variable resistor r4, the operational amplifier 50 outputs a signal based on the reference voltage Vr. An output signal e shown in 2 will be generated.

FIG. 4 shows another embodiment of the space diversity reception system according to the present invention. In this embodiment, a circuit portion (inverter 3 in FIG. 3 and Only the portion corresponding to the level adjustment unit 4) is shown, and the two input signals of another switch 6, which is switched and controlled by the output signal a of the comparator 1, are composed of resistors r11 and r12. Power supply voltage Vc
The signal output from the switch 6 as a result of switching control is as shown in FIG. The signal c' is obtained by adding a whisker to the signal c shown in FIG. That is, the levels of the two DC signals from the switch 6 of the same type as the switch 2 are the same level (a), and therefore the output signal c' of the switch 6 includes the switching noise of the switch 6 itself. Become.

The signal c' outputted from the switch 6 in this manner is applied to the non-inverting input terminal of the operational amplifier 50 after cutting off the DC component of the power supply voltage Vcc by resistors r15, r16 and capacitor c5. The output signal of this capacitor c5 is combined with the reference voltage Vr, so that the component of the signal c' is superimposed on this reference voltage, and as shown in FIG.
Similarly to the above case, the level fluctuation of the output signal d of the switch 2 can be canceled out by the operational amplifier 50. At this time, furthermore, as shown in FIG. 2, there is a whisker in the canceled signal c' itself based on the switching operation of the switch 6, so that not only the level fluctuation but also the whisker in the output signal d can be canceled at the same time. .

[0017]

As described above, according to the space diversity reception system according to the present invention, the level is adjusted by inverting the on/off output signal of the comparator based on the level comparison result of the received signal, or the level is adjusted by inverting the on/off output signal of the comparator based on the level comparison result of the received signal The output signal is used to select one of the two same DC levels using another switch, and the switch is added to the received signal selected by the switch to cancel out the switching noise of the switch itself. It is possible to remove the switching noise due to this, and the distortion rate as a system is also improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram conceptually showing a space diversity reception method according to the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the space diversity reception system according to the present invention.

FIG. 3 is a circuit diagram showing an embodiment of the space diversity reception method according to the present invention.

FIG. 4 is a circuit diagram showing another embodiment of the space diversity reception system according to the present invention.

FIG. 5 is a block diagram showing the configuration of a conventional example.

FIG. 6 is a waveform diagram for explaining the operation of a conventional example.

[Explanation of symbols]

1 Comparator 2,6 Switcher 3 Inverter 4 Level adjustment section 5 Addition section In the figures, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] Claim 1: In a space diversity reception system in which a comparator (1) compares reception levels from two antenna systems and a switch (2) selects a reception signal with a higher reception level, the comparator ( an inverter (3) that inverts the on/off output signal of the inverter (3);
), which generates a signal at a level that cancels out the switching noise of the switch (2) at the timing of the output signal of the switch (2), and the output signal of the level adjuster (4) and the switch (2). A space diversity reception system characterized by comprising: an adder (5) that adds the selected received signal and cancels the switching noise of the switch (2). 2. In place of the inverter (3) and the level adjustment section (4), a second switch that selects one of the two same DC levels according to the on/off output signal of the comparator (1). (6) The space diversity reception system according to claim 1, further comprising: (6).