JPS6027238A - Receiver - Google Patents

Abstract

PURPOSE:To reduce noise due to switching by stopping switching operation to fix to the preceding output from a receiving circuit when no output from plural receiving circuits receiving a signal from an individual antenna respectively reach a prescribed level. CONSTITUTION:Respective FM intermediate frequency signals SA, SB from the receiving circuits 1A, 1B receiving a current from the antennas 2A, 2B respectively are inputted to a changeover switch SW4 and a receiving level comparator 10. The circuit 10 compares the input levels, sets up a high output and a low output out of the compared outputs XA, XB to ''1'' and ''0'' respectively and outputs signals ZA, ZB through an FF31 in a switching signal output circuit 30. The switch SW4 selects a high level out of the signals SA, SB. The detecting voltages VA, VB of the circuit 10 are inputted to a receiving level discriminating circuit 20. The circuit 20 compares the voltages VA, VB with a reference voltage VR, and when both voltages are less than the voltage VR, outputs a signal Wc of ''1'' level to a circuit 30 to set both outputs ZA, ZB of the FF31 to ''0''. When both output voltages of the circuits 1A, 1B are less than the prescribed value, the SW4 is fixed to the preceding outputs of the receiving circuits.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention has a plurality of receiving circuits each receiving signals using separate antennas, and the electric field strength of the signals received by the plurality of receiving circuits is This invention relates to a so-called diversity receiver in which the strongest one is selected and the audio output is obtained.

BACKGROUND TECHNOLOGY AND PROBLEMS A diversity receiver is provided with two receiving circuits that receive signals using separate antennas.
The electric field strengths of the signals received by the two receiving circuits are compared with each other, and the one with the stronger electric field strength among the signals received by the two receiving circuits is selected based on the ratio output. Although audio output is obtained, spike-like noise is generated in the audio output due to switching of the signals received by the two receiving circuits. In particular, this receiver is installed in a car or the like and receives signals while moving, so the electric field strength in each receiving circuit changes constantly and the received signals are switched frequently, so there is no noise. appear frequently.

Particularly, when the electric field strength in each receiving circuit is weak and the S/N of the audio signal is originally poor, the noise becomes noticeable. Is this noise due to switching of the received signal? In order to reduce this, it is also possible to consider, for example, supplying the demodulated audio signal to a previous value hold circuit and holding the demodulated audio signal at the previous value during the transient response period of the switch that switches all signals that have been received. However, in this case, high frequency components in the audio signal are also lost, making the noise more noticeable.

Purpose of the Invention In view of this point, the present invention reduces the noise caused by switching of signals that have been completely received, and reduces the S of the output audio signal as a whole.
/N is improved.

SUMMARY OF THE INVENTION As described above, when the electric field strength in each receiving circuit is weak and the S/N of the audio signal is originally poor, noise due to switching of received signals becomes noticeable. Moreover, the electric field strength is S/N in any of the multiple receiving circuits.
When it does not reach a certain level of strength that becomes the limit in terms of
Izuno 1. Even if the signal received by the receiving circuit is selected, a satisfactory audio output can no longer be obtained.

In the present invention, focusing on this point, when the electric field strength does not reach a certain level in any of the plurality of receiving circuits, regardless of which receiving circuit has relatively strong electric field strength, the received Switching of signals is completely stopped and fixed to the state immediately before the point when the electric field strength no longer reached a certain level in any of the plurality of receiving circuits, or to the state in which the signal received by a specific receiving circuit is selected.

Embodiment FIG. 1 shows an example of a receiver according to the present invention, which is an FM stereo receiver and has - receiving circuits /A and XBk, and these receiving circuits /A and /B each have an antenna, 2A, 2
FM broadcast signals received by antenna 2 and 2B are supplied to front ends 3A and 3B, respectively, and FM intermediate frequency signals S
It is converted into A + S B, and this receiving circuit /A, /B
The output signals SA and SB are the input terminals of the switching switch A.

switching control terminal 1l-C2
Depending on the switching signal, which will be described later, that is generated by the switching circuit, one of the signals SA and SB is selected and taken out from the switching output terminal G, and the selected signal is sent to the FM through the intermediate frequency amplification circuit 11. The signal is supplied to the detection circuit B and subjected to FM detection, and the detected signal is supplied to the stereo demodulation circuit 7 to demodulate the left and right channel audio signals, which are led to output terminals 9A and 9B through the audio amplification circuits gA and gB. be done.

Signals SA and S B i'j of the outputs of /A and , it is determined which of the signals SA and SB has a relatively higher level. Specifically, the signal SA,
SB is supplied to amplitude detection circuits //A and //H, respectively, for amplitude detection, and the detected voltage ■A.

VB is supplied to voltage comparator circuit/2 and compared with each other,
As shown in FIG. 2, when the signal SA is higher in level than the signal SB and the voltage VA is higher than the voltage VB, the two signals XA and XB output from the voltage comparator circuit 7.2 are High level of XA.

When the signal XB is at a low level, the signal SB is at a higher level than the signal SA, and the voltage VB is higher than the voltage VA, the signal XA is at a low level and the signal XB is at a high level. Then, the signal S of the output of the receiving circuit /A, /B
A reception level discriminating circuit flood θ is provided to determine whether either A or SH reaches a certain reference level that reaches the limit in terms of S/H, or whether neither of them reaches this reference level. In the example of FIG. 1, the reception level comparison circuit 10
The output signal XAIXB is applied as a switching signal to the switching control terminals KC and LLD, and the 'signal XA+XB is supplied to a special switching signal output circuit 30. The output signal ZAIZB of the switching signal output circuit 3θ is used as a switching switching signal to be applied to the switching switching control terminal C2/11. ), and this switching signal output circuit 30 is a reception level discrimination circuit, and the signal Wc of the output of 20 causes the 11th river t111
σreru.

Specifically, in the reception level discrimination circuit 20, the output of the amplitude detection circuit //A, //B of the reception level comparison circuit 10 (r wave meter 1 voltage V A + V B is the voltage comparison circuit 2/
A.

2/I3 and are compared with a constant reference voltage VR, respectively, and the signal WA+Wn of the output of the voltage comparator circuit 2/A, 27H is supplied to the NOR gate circuit 22.

Therefore, as shown in FIG. 1, the receiving circuit/A.

When one of the output signals S A I S B of /B reaches a certain reference level, the amplitude detection circuit //A', //B
Detection voltage of the output ■ Either A or VB is the reference voltage VR
When the voltage is higher than 2/A, 27
Either of the output signals W A I W B of B becomes high level, and the NOR gate circuit outputs the signal Wc&'' of the output of 22.
Although the i level becomes low, neither of the signals S A T S n output from the receiving circuits /A and 7B reach the reference level\
Detection voltage V of output of amplitude detection circuit //A, //B
When both A 1vB are less than the reference voltage VR, the output signal WA of the voltage comparator circuit, 2/A, 2/B
, WB become low level, and the NOR gate circuit 2
The output signal Wc of No. 2 becomes high level.

Furthermore, the switching signal output circuit 30 has, for example, a JK-flip-flop circuit 3/, and the output side from which the signal XA+Xn of the voltage comparison circuit/2 of the reception level comparison circuit 10 is obtained is a resistor, ? , 2A, 3.2B'c via J
K-Flip-flop circuit 3/preset terminal PR,
Each is connected to the clear terminal CL, and the output side of the NOR gate circuit of the reception level discrimination circuit 20 and 2.2 is a resistor of 33A.
, 33B to the transistor 311A.

3'lB, respectively connected to the base of transistor 3
The collectors of 11A and 3'lB are connected to the preset terminal PR and clear terminal CL of the JK-flip-flop circuit 3/, respectively, and the transistors 34'A and 3'lB
The emitters of B are grounded, and the J terminal, clock terminal CP, and terminal of the JK flip-flop circuit 3/3 are grounded, and the Q terminal is connected to the switching control terminals C and ID of the Q terminal. be made into

Therefore, the signal 5AIS11 of the output of the receiving circuit /A, /B
When either of them reaches the reference level, the signal WC output from the reception level discrimination circuit 20 becomes low level.
Transistors 3IIA and 3GB are both turned off,
Signals XA and XB output from the reception level comparison circuit 10 are applied to the preset terminal PR and clear terminal CL of the -E-tJK-flip-flop circuit 3/, respectively, that is, the preset terminal PR.

The signal YAIYB of the clear terminal CL becomes the same as the signal X A I X n of the output of the reception level comparison circuit 10, and at this time, the Q
The switching signal ZA obtained at the +Zoo terminal and Q terminal is the same as the signals YA and YB of the preset terminal PR and clear terminal CL, respectively, so in the end, the -) switching signal ZA r
Zn is the signal XA output from the reception level comparison circuit 10
They are the same as I x B. Therefore, at point 1 in FIG. As shown before and after time t2, the signal SA
If the level is thicker than the signal SB, the diode DA is turned on and the diode DB is turned off during switching, the signal SA is taken out to the output terminal G, and the signal SB
If the level is higher than that of signal SA, diode DA is turned off and diode DB is turned on during switching, and signal SB is taken out to output terminal G, and signal SA
and SB with a higher level is selected, and an audio output is obtained based on the signal with the higher level.

When neither of the signals S A I S B output from the receiving circuits /A and /B reaches the reference level, the signal Wc output from the receiving level discriminating circuit 20 becomes the quotient level.
Transistors 3LA and 3GB are both turned on,
JK-Flip-flop circuit 3/preset terminal PR
, the potentials of the clear terminal CLh both become the ground potential. Therefore, at point 1 in FIG. As shown between and time t2,
Relatively output signals of receiving circuits /A and /B S A I
Regardless of which level of S n is greater, that is, the signal X A I X B of the output of the reception level comparison circuit 10
Regardless of the state of
In the case of FIG. 2, the state just before the point L/ when both B and B no longer reach the reference level, the signal ZA is at a low level and the signal Z
B is fixed at a high level. Therefore, the switching is stopped and the switching is also stopped at time 1. In the case of Fig. 2, the state immediately before is fixed to the state in which diode DA is off, diode DB is on, and signal SB is taken out to output terminal LLE, and the sound due to one signal is unrelated to the magnitude of the level. I get the output.

The example in Figure 1 shows the signal SA of the output of the receiving circuits /A and /B.
If none of the ISBs reach the standard level,
Switching changeover signals ZA and ZB are signals S A I S
This is a case where f signals SA and SB are both fixed at the state before iσ when they no longer reach the reference level, and switching is fixed at the state immediately before the time when both f signals SA and SB no longer reach the reference level. switching signal ZA
IZB is fixed in a specific state, for example, signal ZA is fixed at high level and signal ZB is fixed at low level, and switching is a state in which the output signal of a specific receiving circuit is taken out to output terminal LLE, for example, diode DA is turned on. , diode D
When B is off, the signal SA from the receiving circuit/A is output to the output terminal/
It may be fixed in a state where it is taken out to IE.

In addition, as in the example of FIG. 1, a special switching signal output circuit 30
is not provided, the output signals XA and XB of the reception level comparator circuit 10 are given to the switching control terminals C and 4tD as switching signals for the same period of time, and the reception level 'I'-1] The voltage ratio axis circuit 7.2 of the reception level comparison circuit 10 is controlled 1111 by the signal W C output from the separate circuit 20, and either of the signals S A + S H output from the output 7B is sent to the reception circuit 7 at the reference level. When reaching , the signal Wc becomes low level.
Amplitude detection circuit with voltage comparison circuit 7.2 //A, //B
The detected voltages V A + V n of the outputs of the voltage comparator circuit 7.2 are compared with each other, and the switching signals XA' and XB of the outputs of the voltage comparison circuit 7.2 indicate which of the signals S A I S B has a relatively higher level. When none of the signals SA I S n reaches the reference level, the signal WC becomes high level, and the voltage ratio axis operation of the voltage comparator circuit 7.2 is blocked, and the amplitude detection circuit Regardless of which of the detected voltages VAIVB of the outputs of A and //H is relatively high, the switching signal XAIXB of the output of voltage comparator circuit /2
It may be configured such that the signal XA is forced to a specific state, for example, the signal XA is at the city level and the signal 'iXn is set to a low level.

Application example Receiving circuit/A of the output of the above-mentioned receiving level discriminating circuit 20
, /H output signal Wct indicating whether the signal SA or SH reaches the reference level or neither reaches the reference level.If the signal Wct is supplied to an appropriate display circuit, , /B, when the electric field strength of -.force t is not reached, a message to that effect can be displayed.

In addition, in a type of receiver in which the local oscillation frequency is automatically scanned to select a station, a reception level determination circuit,!
0 output signal WCff: Used as a scanning start signal. When a certain electric field strength is not reached in either receiving circuit /A or /B, another broadcasting station with a good electric field condition is automatically searched. You can also make it so that

Furthermore, in a receiver having a memory card for setting all broadcast stations, a reception level discrimination circuit, one word Wck of the output of 20
Using it as a memory read signal, the receiving circuit/A,
/H, when the electric field strength does not reach a certain level, a preset broadcasting station may be read out from the memory and the system may be automatically switched to that broadcasting station.

Effects of the Invention According to the present invention, when the electric field strength in each receiving circuit is weak and the S/N of the audio signal is originally poor, noise due to switching of received signals becomes noticeable, and multiple In any of the receiving circuits, the electric field strength is S
If the signal strength that reaches the limit at point /H is not reached, no matter which receiving circuit selects the received signal, a satisfactory volume power is no longer achieved. By focusing on The state immediately before a certain electric field strength is no longer reached in any of the multiple receiving circuits,
Alternatively, since the signal received by a specific receiving circuit is fixed in a selected state, noise due to switching of the received signal is reduced, and the overall S/N ratio of the output audio signal can be improved.

[Brief explanation of drawings]

FIG. 1 is a connection diagram of an example of the receiver of the present invention, and FIG. 1 is a waveform diagram for explaining its operation. In the figure, /A and /B are receiving circuits, 2A and 2B are their antennas, 3A and 3B are their front ends, ll
Lotus J conversion switch, 10 is reception level comparison circuit, //A
and//I3 is its amplitude detection circuit, 7.2 is its voltage comparison circuit 1.20 is its reception level discrimination circuit 2.2/A, and
27B is the 1'' valley of the voltage ratio axis, and 30 is a switching signal output circuit.

Claims (1)

[Claims] A plurality of receiving circuits each receiving signals through separate antennas, a J exchange switch for selecting seven of the signals received by the plurality of receiving circuits and outputting them, and the above-mentioned J exchange switch. a reception level comparison circuit that compares the levels of the signals received by the plurality of reception circuits and determines which reception 1δ circuit has the highest level of the signal;
and a reception level determination circuit that determines which of the signals received by the plurality of receiver 1a circuits reaches a certain reference level, and which of the signals does not reach this reference level,
When any of the signals received by the plurality of receiving circuits reaches the reference level, the selector switch selects the signal with the highest level among the signals received by the plurality of receiving circuits. If the signal received by the plurality of receiving circuits does not reach the reference level, the selector switch switches the signal to output the signal received by the plurality of receiving circuits. A receiver that is fixed to a state immediately before the point at which the reference level is no longer reached, or a state in which a signal received by a specific receiving circuit is selected and output.