JPH04189025A - Signal changeover circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a signal switching circuit in a constant impedance signal transmission line.

[Conventional technology]

For example, in a multi-phenomenal oscilloscope, the target input signals span a wide range from DC signals to high frequency signals, and it is necessary to switch such input signals in accordance with the observation mode. When switching such a wideband signal in a constant impedance transmission line, a switching element that takes impedance matching into consideration is required, and relays, PIN diodes, and the like are used.

[Problem to be solved by the invention]

However, when a relay is used as a switching element, it has the disadvantages that the relay is physically large and has a poor space factor, cannot perform high-speed switching, and is expensive unless it can handle high-frequency signals. Further, when a PIN diode is used as a switching element, there are drawbacks such as being unable to switch only a DC signal and having a large insertion loss. The present invention aims to eliminate these drawbacks and provide a signal switching circuit capable of switching a plurality of input signals ranging from direct current to high frequency.

[Means to solve the problem]

For this reason, in this invention, if the reference numerals of each part correspond to the embodiments described later, the first
and a second preamplifier 11,]2, a constant impedance signal transmission line 3 whose both ends are connected to the output ends of these first and second preamplifiers 11 and 12, and this signal transmission line B. A main amplifier 4 whose input end is connected to one point inside the main amplifier 4 is provided, and the first and second preamplifiers 11 and 12 are switched between an operating state and a non-operating state by a control signal. The first or second human input signals Sl, S2 supplied to the preamplifiers 11 and 2 of the second preamplifier 11 and 12 are selectively taken out as outputs through the signal transmission line 3 and the main amplifier 4, and Among the amplifiers 11,]2,
The signal transmission line 3 is matched and terminated by the output impedance of the preamplifier in the non-operating state.

[Effect]

The input signal is selectively switched depending on the operating state and non-operating state of the preamplifiers 11 and 12, and this switched signal is taken out as an output through the signal transmission line 3 and the main amplifier 4, and at this time, the inactive state The signal transmission line 3 is matched terminated by the preamplifier located at the front end, thereby preventing deterioration of the output signal.

【Example】

FIG. 1 shows an example in which the present invention is applied to a circuit that selectively switches between two signals. That is, in FIG. 1, 1] indicates a first preamplifier, and in this example, the final stage of this amplifier 11 is:
A cascode amplifier is formed by a common emitter transistor Q1 and a common base transistor Q2. A load resistor R1 is connected to the collector of transistor Q2.
is connected, and its collector is used as the output terminal of the amplifier 11. Further, 12 indicates a second preamplifier, and this amplifier 12 is configured similarly to the first amplifier 11. Furthermore, 21 and 22 indicate first and second signal sources or input terminals, from which the preamplifier 1 is connected.
1.12 are supplied with first and second input signals SL, S2, respectively. Further, a constant impedance signal transmission path 3 is connected between the output end of the amplifier 11 and the output end of the amplifier 12, and one point PO in this transmission path 3 is connected to the main amplifier 4. Furthermore, the emitters of transistors Q2 and Q2 of amplifier 11.12 are connected to control terminal 61.62 through switching diodes D1 and DI. Note that the values of the resistors R1 and R1 of the amplifiers 11 and 12 are made equal to or approximately equal to the characteristic impedance of the transmission line 3. Further, the input impedance of the amplifier 4 is made sufficiently larger than the characteristic impedance of the transmission line 3. In such a configuration, if Vl is the control voltage V2 of the control terminal 61 and the control voltage VB2 of the control terminal 62:) the base voltage of the Lannostar Q2, then if Vl<VB2 V2>VB2, the amplifier 12 is controlled by the voltage V2. Diode D
1 is forward biased and turns on, so transistor Q
2 is turned off, and the amplifier 12 becomes inactive. Therefore, the second inlet J supplied to the amplifier 12
The signal S2 is blocked by the transistor Q2 and is not supplied to the transmission line 3. Furthermore, Vl<VB2, and whether this voltage V1 or the amplifier]
1 diode - 1” DI, so amplifier 1
1, tie auto DI is reverse biased off and transistor Q2 is in the operating chain and amplifier 1 is turned off.
1 is in the operating state. Also, at this time, in the amplifier 12, the transistor Q2 is turned off and its output impedance is sufficiently large, so that the end P2 of the transmission line 3 on the amplifier 12 side is connected to the amplifier 12.
Match termination is provided by two resistors R1. Therefore, the first input signal S1 supplied to the amplifier 1 is transmitted through the amplifier 1 - the end P1 of the transmission line 3 on the amplifier 11 side - the transmission line 3 - the point P - the signal line of the amplifier 4 to the terminal 5. is output to. On the other hand, contrary to the above, in the case of Vl>VB2 v2<vB2, the relationship between the diode DI and transistor Q2 of amplifier 1 and the diode DI and transistor Q2 of amplifier 2 is opposite to the above. Become. Therefore, in this case, the amplifier 12 is in the operating state, and the second signal S2 supplied to the second amplifier 12 is transmitted to the terminal 5 through the points P2 to PO of the transmission line 3 and the amplifier 4.
It is taken out. Also, at this time, since the amplifier 11 is in an inactive state, the first input signal S1 supplied to the amplifier 11
is not supplied to the transmission line 3. Therefore, by changing the control voltages V1 and V2 of the terminals 61 and 62, the first human input signal Sl and the second input signal S2 can be selectively switched and outputted to the terminal 5. Thus, according to the present invention, it is possible to selectively switch and output the first and second input signals SJ and S2. The switching preamplifiers ]U, ]2 select the first and second input signals Sl and S2, and the output impedance of the amplifiers ]1, ]2 in the non-operating state or the characteristic impedance of the transmission line 3 is selected. have been equalized. Therefore, the first and second human input signals S1 and S2 can be reliably switched, and the ends of the constant impedance transmission line can be matched terminated, and the signals St and S
Even if 2 is a broadband signal ranging from direct current to high frequency, it can be switched without deteriorating the characteristics. Furthermore, since it is not necessary to use a relay as a switching element, the space factor can be reduced and high-speed switching can be performed. Or there is no need to use expensive high-frequency relays. Furthermore, when a PIN diode is used as a switching element, it may not be possible to switch a DC signal or an insertion loss may occur, but according to the present invention,
There is no such thing. FIG. 2 shows another example of the amplifier 11, ]2. In the example of FIG. 1, the preamplifier ]1.12 is a current output type, whereas the example of FIG. Regarding odor, this is the case when a voltage output type is used. That is, in this example, the collector of the transistor Q2 is connected to the transmission line 3 through the emitter follower transistor Q3 and the resistor R2. In addition, the resistor R
The value of 2 is made equal to or approximately equal to the characteristic impedance of the transmission line 3. According to such a configuration, when the diode DI is on due to the control voltage V1 or v2, the transistor Q2 is turned off and the amplifier 11 or 12 is put into a non-operating state. However, at this time, the transistor Q3 is in an operating state and its output impedance is sufficiently low, so that the end P1 or P2 of the transmission line 3 is matched and terminated by the resistor R2. In addition, the diode D1 is controlled by the control voltage V1 or ■2.
Since transistor Q2 is in an active state when the amplifier is off, the amplifier 1] or 12 is in an active state. Therefore, in this example as well, the first and second human power signals Sl and S2 can be selectively switched and output to the terminal 5 using the control voltages V1 and 2. FIG. 3 shows an example in which the present invention is applied to a circuit that selectively switches three signals. That is, in FIG. 3, 11 to 13 indicate the first to third preamplifiers, and in this example, these amplifiers 1
1 to 13 are constructed similarly to that of FIG. 1, or resistor R1 is not connected. Further, 21 to 23 indicate first to third signal sources or input terminals, and the terminals 21 to 23 are connected to the preamplifiers 11 to 23.
] 3 are supplied with first to third input signals 5l-33, respectively. Resistors R11 and R12 for matching termination are connected to both ends PI and P2 of the transmission line 3, and each point P1 . I-P]3, amplifier 11~]
The three output terminals are connected to each other. Further, one point PO in the transmission line 3 is connected to the main amplifier 4. Furthermore, the emitters of the transistors Q2-Q2 of the amplifiers]]-]3 are connected to control terminals 61-63 through switching diodes DI-Di. In such a configuration, if Vl - control voltage V2 of control terminal 61 - control voltage V3 of control terminal 62 : control voltage of control terminal 63 VB2+1 - base voltage of Lancistor Q2, then Vl<VB2 V2>VB2 V3>VB2 In this case, the diode DI of the amplifier 11 is turned off by the voltage V1 in FIG. It passes through an amplifier 4 and is taken out to a terminal 5. Note that at this time, the characteristic impedance of the transmission line 3 acts as a load impedance of the amplifier 11. Furthermore, since V2>Vl2 and V3>Vl32, both diodes DI and DI of amplifier 12.13 are on, and amplifier 12.13 is inactive. The second and third input signals S2, S3, which are supplied to these amplifiers 12.13, are therefore supplied to the amplifiers 12.1.
3 and is not output to terminal 5. Note that at this time, since the transistors Q2 and Q2 of the amplifier 12.13 are off, their output impedance is sufficiently high and the transmission line 3
2.13 is equivalent to not being connected. Therefore, in this case, the first human power signal S is selected and output to the terminal 5. Similarly, in the case of Vl>VB2 V2<VB2 V3>VB2, only the second input 1M number S2 is selected and output to the terminal 5, and in the case of Vl>VB2 V2>VB2 V3<Vt32, Only the third human power signal S3 is selected and output to the terminal 5. Therefore, by changing the control voltages v1 to V3 of the terminals 61 to 63, the first to third human power signals S1 to S3
can be selectively switched and taken out to the terminal 5. In addition, in the above, the output terminal pH of the amplifiers 11 to 13 is
If P1.3 coincides with the end P] or P2 of the constant innovidance transmission line, it is also possible to use an amplifier with a predetermined output impedance by means of indirect feedback or an emitter follower. Furthermore, if an impedance mismatch occurs due to the human power capacity of the main amplifier 4 or the output capacity of the preamplifiers 11 to 13, it can be compensated for by using a bridging T-type bridge.

【Effect of the invention】

According to the invention, the first and second input ports J
Selecting signals Sl, S2 and amplifiers 11.12
The output impedance in the non-operating state is equal to the characteristic impedance of the transmission line 3. I want to do it, part]
It is possible to reliably switch the second input signals 51 and S2, and also to achieve matching with the output signal S1 or S2, so that the signals St and S2 are broadband signals ranging from direct current to high frequency. However, it can be switched without deteriorating the characteristics. Further, since there is no need to use a relay as a switching element, the space factor is good and high-speed switching can be performed. Or there is no need to use expensive high-frequency relays. Furthermore, if a PIN diode is used as a switching element, it may not be possible to switch the DC signal, or an insertion loss may occur.According to the second invention,
There is no such thing.

[Brief explanation of drawings]

1 to 3 are connection diagrams showing an example of the present invention. 11-13. preamplifier 21-23: Signal source or input terminal 3; Transmission line 4; Main amplifier 5: Output terminal 61-63; control terminal 81-S3, input signal ■1~V3, control voltage Agent: Patent Attorney Masami Sato 63' Iotgo 4 Kuware Tsukio Rashi times 2 list Figure 3 4δ No. cut time 1 doji 6 Figure 1 Bango seven swords month center nine words

Claims (2)

[Claims] (1) First and second preamplifiers that have a predetermined output impedance in a non-operating state, and a constant impedance signal transmission line that is connected at both ends to the output ends of these first and second preamplifiers. and a main amplifier whose input end is connected to one point in the signal transmission path, and the first and second preamplifiers are switched between an operating state and a non-operating state by a control signal, and by this switching, A first or second input signal supplied to the first and second preamplifiers is selectively taken out as an output through the signal transmission path and the main amplifier, and A signal switching circuit that matches and terminates the signal transmission path using the output impedance of a preamplifier in an inactive state among the amplifiers. (2) A plurality of preamplifiers each having a predetermined output impedance in a non-operating state, a constant impedance signal transmission line with matching termination at both ends, and a main amplifier whose input end is connected to one point on this signal transmission line. and the output ends of the plurality of preamplifiers are connected to any point on the signal transmission path, and one of the plurality of preamplifiers is activated by a control signal. At the same time, the remaining preamplifiers are switched to a non-operating state, and by this switching, a plurality of input signals respectively supplied to the plurality of preamplifiers are selectively taken out as outputs through the signal transmission path and the main amplifier. signal switching circuit.