CN1111419A - High-frequency singlepole multi-throw switch with gain function - Google Patents

Abstract

The said switch includes several signal input terminals, each of which has a corresponding transistor and an input matching network, one signal output terminal with output matching network and one DC bias network. The present invention uses transistors as switch component with gain function and by means of changing the bias voltage of DC bias network, one transistor is in the linear amplification region and the others are in cutoff region so as to change over HF signals.

Description

High-frequency singlepole multi-throw switch with gain function

The present invention relates to a kind of high-frequency singlepole multi-throw switch of forming by transistor, particularly a kind of single pole multiple throw that constitutes with transistor with gain function.

The present invention is applicable to the switch of vertical, the horizontal polarization satellite signals of switching after frequency reducing.Select in the switch element of high-frequency signals at suitching type at present, a kind of is relay, and another kind is a PIN diode, all can form the characteristic of path or open circuit to a plurality of signal sources, but, when using relay (single pole multiple throw), because relay is a kind of mechanical organ as selector switch, compare with electronic component, when temperature was too high or too low, its failure rate was higher, and the life-span is shorter again, and belong to passive device, signal there is not gain function.When utilizing PIN diode as this type of switch, though can solve the higher and short problem of life-span of relay failure rate, but want to reach the signal isolation identical with relay switch, required component number more (generally needing 4 to 8 PIN diode just can reach the isolation of 20dB when the BHF frequency range), and lossy to signal.

The purpose of this invention is to provide a kind of reliability height, the life-span is long, component number is few, simple in structure high-frequency singlepole multi-throw switch with gain function.

The present invention adopts transistor as switch element, and utilizes the mode of switching its operating voltage to determine transistor to enter linear amplification district or cut-off region, with the gating of controlling signal.

The present invention includes a plurality of signal input ends, it is characterized in that also comprising: with the transistor of signal input end similar number, this transistor constitutes the switch element with gain function; With the input matching network of transistor similar number, each input matching network is connected between corresponding signal input end and the transistor input; A signal output end; An output matching network, this output matching network is connected between above-mentioned all crystals triode output and the above-mentioned signal output end; A Dc bias network, this Dc bias network make that the transistor corresponding with it is in the linear amplification district when switching certain input signal, and other transistor are in cut-off region for above-mentioned each transistor provides bias voltage.

Because the present invention has only adopted an output matching network, make the structure of whole switch more simple, switch element owing to employing is the low transistor that gain is arranged of a cost again, thereby does not need to establish in addition the loss of amplifier with compensating signature, has further reduced cost.

Fig. 1 is the circuit theory diagrams of transistor as the high-frequency signals booster element.

Fig. 2 is the circuit theory diagrams of single-pole double-throw switch (SPDT) of the present invention.

Fig. 3 is the equivalent circuit diagram of circuit shown in Figure 2.

Fig. 4 is one embodiment of the present of invention circuit diagrams.

Fig. 5 is an alternative embodiment of the invention circuit diagram.

Fig. 6 is the circuit diagram of the active pull-down circuit in the Dc bias network that inserts of A among Fig. 5, B, C, D point.

Fig. 7 is the state table of input voltage and each output point among Fig. 6.

Fig. 8 is a kind of circuit diagram of input matching network.

Fig. 9 is a kind of circuit diagram of exporting matching network.

In Fig. 1, transistor BG1 is connected into an amplifier, as seen from the figure for make signal source 10 and transistor BG1 input and make transistor BG1 output and load 14 between match each other, need are connected with output at the input of transistor BG1 and connect respectively an input matching network 11 and an output matching networking 12, so just can make amplifier have better performance. Capacitor C wherein_B、C _CBe respectively the input of BG1, output capacitance is to prevent that substrate, collector voltage are transfused to, output network is affected. Choke coil L_B、L _CBe used for preventing that AC signal from being affected by DC circuit, Zin, Zout represent respectively the input, output-resistor of BG1, resistance R_B、R _CBe respectively biasing resistor and collector resistance.

When the bias voltage of transistor BG1 makes it be operated in linear amplification region, high-frequency signals is had amplification, have specific input and output impedance. But when BG1 enters cut-off region, then lose amplification, the input, output-resistor approach infinity.

Suitably select capacitor C_B、C _CWith choke coil L_B、L _CNumerical value or adopt other bias circuits to make it to become part or all of input, output matching circuit, can reduce the used element of match circuit.

The present invention utilizes transistor to have amplification just when linear amplification region, and characteristic that input when cut-off region, output have a high impedance realizes the invention task.

The present invention with a plurality of transistors as switch element, only adopt an output matching network (element 36 of Fig. 2) at each transistor output, be another main feature of the present invention, if each transistor each has it and independently exports matching network, then can produce between each matching network and influence each other, can make that the numerical computations of interior each element of each matching network is quite difficult, when the present invention utilizes transistor to end, the characteristic that output impedance is high, have only a transistor to be in the linear amplification district in the control at one time, and make the output of each transistor be connected on same contact (as Fig. 2, Fig. 4, the symbol A of Fig. 5 ₁The point) on, and make switching circuit be in close proximity to the output impedance of one-transistor in the output impedance of same contact, so only need to use the parameter of a transistor just can design the output matching network, thereby reduced and designed the required element of a plurality of output matching networks, further reduced cost.

Fig. 2 shows single-pole double-throw switch (SPDT) circuit (a kind of circuit of single pole multiple throw circuit), this circuit utilizes bias voltage switch unit 35 to make transistor BG1 be in the linear amplification district, transistor BG2 is in cut-off region, equivalent electric circuit as shown in Figure 3, as seen from the figure, signal is exaggerated through behind the input matching network 31 to BG1 from signal source 33, is coupled to load 37 by output matching network 36 again.Because BG2 is in cut-off region at this moment, its input can not be coupled to output matching network with this signal near opening a way, reflecting the signal from signal source 34.Like this, side's signal is exaggerated, and the opposing party's signal is reflected, and has just obtained a high frequency single-pole double-throw switch (SPDT) that the signal isolation is high.

Fig. 4 is one embodiment of the present of invention, in this example, adopts N channel junction field-effect pipe as amplifier element, and as control circuit, bias voltage Vss is a negative voltage and less than two N channel junction field-effect pipe JFET with switch 41 ₁, JFET ₂Pinch-off voltage VP ₁, VP ₂, when switch 41 was in the upper end, bias voltage Vss met JFET ₁Grid, make JFET ₁Enter cut-off region, lost from input I/P ₁The signal amplification, and since technotron by the time its input, output impedance very high, with input signal reflected back signal source, and don't influence the characteristic of output circuit.And JFET ₂Be in the automatic bias state this moment, to from input I/P ₂Signal amplification is arranged, in the drawings, IMN ₁, IMN ₂Be input matching network, OMN is the output matching network.

Fig. 5 shows with transistor and makes the circuit that hilted broadsword four is thrown (it is a kind of that hilted broadsword is thrown) switch more, and in the drawings, A, B, 4 of C, D are respectively the base stage Dc bias insertion point that switch element is transistor BG1-BG4, choke LB ₁, LB ₂, LB ₃, LB ₄Be connected on each transistor biasing resistor R respectively ₁₁, R ₂₁, R _B1, R ₁₂, R _B2, R ₁₃, R ₂₃, R _B3, R ₁₄, R ₂₄, R _B4Between the base stage of exit (being A, B, C, D point) and each transistor, to intercept high-frequency signals, C ₆₁, C ₆₂, C ₆₃, C ₆₄Be input capacitance, the Lc output choke, to intercept high-frequency signal, Rc is a dropping resistor, I/P ₁, I/P ₂, I/P ₃, I/P ₄Be signal input end, IMN ₁, IMN ₂, IMN ₃, IMN ₄Be input matching network, Cc is an output capacitance, and OMN is the output matching network, and O/P is an output.On A, B, C, D, connect four outputs of active pull-down circuit as shown in Figure 6 at 4 respectively.Transistor BG1, BG2, BG3, BG4 and peripheral cell are connected into the common emitter amplifying circuit.

Initiatively pull-down circuit is by voltage comparator Q ₁, Q ₂, Q ₃, Q ₄, Q ₅, Q ₆Constitute (model is LM339), have four outputs, each output joins (promptly joining by the base stage of a choke and transistor) with the direct-flow input end of 4 transistors respectively.Reference voltage of one of each comparator input termination, another input of each comparator and connect after connect control signal.Comparator Q ₁Output termination A point, Q ₂, Q ₃Output termination B point, Q ₄, Q ₅Output termination C point, Q ₆Output termination D point, the voltage of each output and the voltage relationship of control signal are as shown in Figure 7, " 1 " expression voltage is 0.7V in Fig. 7, " 0 " expression voltage 0.2V, when control voltage is 0-4.5V, the voltage that D is ordered is 0.7V, and BG4 enters the amplification region, BG1, BG2, BG3 is in cut-off region, when in like manner controlling voltage and being 4.5V-7.5V, BG3 enters the amplification region, BG1, BG2, BG4 is in cut-off region, and BG2 enters the amplification region when control voltage is 7.5V-10.5V, BG1, BG3, BG4 is in cut-off region, when control voltage was 10.5V-Vcc, BG1 entered the amplification region, BG2, BG3, BG4 is in cut-off region.For transistor BG1, BG2, BG3, BG4, biasing resistor and active pull-down circuit have constituted the Dc bias network, initiatively pull-down circuit has guaranteed that switch element is that transistor BG1, BG2, BG3, BG4 have only a transistor to be in the amplification region, and other crystal three utmost points and be in cut-off region.So just realized selecting different high frequency input signals and the purpose that this signal is amplified by the voltage that changes control signal.

Fig. 8 shows a kind of structure of input matching circuit.

Fig. 9 shows a kind of structure of output matching circuit.

Input, output matching circuit can also adopt other circuit structure, but its circuit structure does not belong to scope of the present invention.

Control signal shown in Fig. 6 can also can be passed through the different voltages on the change over switch input resistance voltage divider from the signal of receiver of remote-control sytem output.

Hilted broadsword four throw switches shown in Figure 5 are specially adapted to the switch satellite TV signal, compare with existing technological means, have following characteristics:

1., have gain and isolation height.

2., reliability height, life-span are long.

3., circuit structure is simple.

4., cost is low.

5., can match with various control signals.

Claims (4)

1, a kind of high-frequency singlepole multi-throw switch with gain function comprises a plurality of signal input ends, it is characterized in that also comprising: with the transistor of signal input end similar number, this transistor constitutes the switch element with gain function; With the input matching network of transistor similar number, each input matching network is connected between corresponding signal input end and the transistor input; A signal output end; An output matching network, this output matching network is connected between above-mentioned all crystals triode output and the above-mentioned signal output end; A Dc bias network, this Dc bias network provides bias voltage for above-mentioned each transistor.

2, high-frequency singlepole multi-throw switch according to claim 1 is characterized in that: above-mentioned transistor and peripheral cell are connected into common emitter circuit.

3, high-frequency singlepole multi-throw switch according to claim 1 is characterized in that: the Dc bias network comprises biasing resistor that is connected with each transistor and the active pull-down circuit that is connected the transistor direct-flow input end.

4, high-frequency singlepole multi-throw switch according to claim 1 is characterized in that: initiatively pull-down circuit is made of voltage comparator.

Images