JPH0432831Y2 - - Google Patents

Description

[Detailed description of the invention] (Technical field) This invention relates to the improvement of voltage controlled oscillators (VCOs) used in radio equipment and the like. (Prior art and its problems) FIG. 2 shows a conventional embodiment. 2 is a voltage controlled oscillator (hereinafter referred to as VCO) for transmission, and 3 is for reception.
VCO, 1 is the input control terminal for VCOs 2 and 3, 4,
5 is the output coupling capacitance of VCO2 and 3, 8 is a buffer amplifier (transistor) formed by an emitter follower, 6 and 7 are DC bias resistors, 9 is a coupling capacitor,
14 is an amplifier (transistor), 10 and 12 are DC bias resistors, 11 and 13 are high frequency bypass capacitors, 15, 16 and 17 are output matching circuit elements, 18 is an output terminal, 19 and 22 are switching for transmission and reception switching The transistors 20 and 21 are DC limiting resistors, 24 is a control terminal of a switching transistor 19 and 22, and 23 is a voltage application terminal.

An example of operation is shown in FIG.

Now, when the terminal 24 is set to LOW level, the transistor 22 becomes conductive and a voltage is applied to the receiving VCO 3. At this time, the transistor 19 becomes non-conductive, and no voltage is applied to the transmission VCO 2.

That is, only the receiving VCO 3 operates, and its oscillation output is injected into the amplifier 14 via the coupling capacitor 5 and the buffer amplifier 8. It appears at the output end 18 through. Next, the control terminal 24
When the signal is set to High level, the transistor 22 becomes non-conductive and the transistor 19 becomes conductive. For reception
Since the voltage of VCO3 is passed through the DC limiting high resistance 20, it is very low and VCO3 does not operate. The voltage of VCO2 is applied through the transistor 19, and only VCO2 operates. The oscillation output appears at the output terminal 18 in the same manner as described above. However, in the conventional technology, a direct current bias is applied to each of the transistors 8 and 14 independently, resulting in a large amount of current consumption. This is especially fatal for receiving VCOs such as receivers that require low current consumption. Furthermore, since the gains of the transistors 8 and 14 are almost constant during transmission and reception, the output level appearing at the output terminal 18 is approximately the same level during transmission and reception, and generally the output level is set high during transmission. This has become a drawback if you want to.

(Purpose) In order to solve these drawbacks, this invention uses an emitter follower amplifier and an amplifier in direct current cascade connection to reduce the current consumption of the voltage controlled oscillator circuit during reception. A second purpose is to increase the base current of the amplifier only during transmission, increase the collector current, increase the high frequency gain of the amplifier, and increase the oscillation output during transmission compared to during reception.

(Example) An example of this invention will be described below with reference to FIG. In FIG. 1, the same numbers as in FIG. 2 indicate the same functions. 27 is a high frequency bypass capacitor, 25
is a DC control resistor, and 26 is a diode. This operation will be explained below. Control terminal 24
When set to LOW level, the transistor 22 becomes conductive and a voltage is applied to the receiving VCO 3, so that the VCO operates. The output of VCO3 is the coupling capacitor 5 and the coupling capacitor 9 of the emitter follower amplifier 8.
is injected into the input of amplifier 10 via
A receiving VCO output is obtained at the output terminal 18. On the other hand, transistor 19 becomes non-conductive and is used for transmission.
The voltage of VCO2 is applied through the DC control resistors 6-2, 6-1, 25 and the diode 26, but since the voltage applied to VCO 2 is extremely low, the transmitting VCO 2 is Do not work. Now, focusing on the DC bias of transistors 8 and 10, the base potential V _8b of transistor 8 is V _8b = (Vcc - V _10b / r _6-1 + r _6-2 ) × (r _6-1 ) + V _10b ( where Vcc; 23 power supply voltage, V _10b ; for receiving
Base potential of transistor 10 during VCO operation,
r _6-1 , r _6-2 ; Indicates the DC resistance value of 6-1 and 6-2.
Next, when the control terminal 24 is at a high level, the transistor 19 becomes conductive and only the transmission VCO 2 operates. Here, similarly to the above, focusing on the DC bias of transistors 8 and 10, diode 26 is reverse biased and becomes non-conductive. The base potential V′ _8b of transistor 8 is V′ _8b = (Vcc−V′ _10b /r _6-2
+r _6-1 ) (r _6-1 )+V′ _10b (where
V _10b ; Indicates the base potential of the transistor 10 during transmission VCO operation. ), the difference between both equations (V′ _8b ′−V _8b ) is V _8b ′−V _8b = (V _10b −V′ _10b / r _6-1 + r _6-2 )×(r _6-1
) + (V′ _10b −V _10b ) = (V′ _10b −V _10b ) (1−r _6-1 / r _6-1 + r _6-2 ) = (
V′ _10b −V _10b ) (r _6-2 / r _6-1 + r _6-2 ).

Here, the resistance value is set to 25 so that V′ _10b −V _10b > 0.
When designing, V _8b ′> V _8b . In other words, the transmitting VCO
In operation, the base currents of transistors 8 and 10 increase, and thus the collector currents increase, and the high frequency gain of transistor 10 increases. As a result, the transmission VCO operation is better than the reception VCO operation.
The output level becomes higher.

On the other hand, if we focus on direct current,
During VCO operation, the base potential of the transistor becomes lower than when transmitting VCO operates, and the collector current becomes smaller. In addition, since two transistors are used in a cascade connection using direct current, the current can be reduced by half compared to the conventional circuit system.

[Brief explanation of the drawing]

Figure 2 shows an example of a conventional voltage controlled oscillator (VCO) circuit, and Figure 1 shows an example of the present invention. 1...Input control terminal, 2...VCO for transmission, 3
...Receiving VCO, 4, 5, 9...Coupling capacitance, 6
-1, 6-2, 7, 12, 25... DC bias resistance, 11, 13, 27... High frequency bypass capacitor, 16, 17... Matching element capacitance, 8, 10
... High frequency amplification transistor, 15 ... Matching element inductance, 19, 22 ... Switching transistor, 20, 21 ... DC limiting resistor, 2
3...Power terminal, 24...Transmission/reception switching terminal, 18
...Output terminal.

Claims (1)

[Scope of utility model registration request] A synthesizer-type electronic device consisting of two voltage controlled oscillators, a transmitting voltage controlled oscillator and a receiving voltage controlled oscillator, includes a high frequency amplifier for amplifying the output of the voltage controlled oscillator and an emitter follower for the output of the voltage controlled oscillator. In a circuit in which amplifiers are continuously connected in a DC manner to share the collector current of the two amplifiers, a diode is inserted in series with a fixed bias resistor in the base bias circuit of the high frequency amplifier, and the diode is reverse biased during transmission. The voltage is applied to make the diode non-conducting, and the base fixed bias resistance values of the amplifier and high-frequency amplifier are reduced to increase the base current, increasing the collector current, and during reception, the diode is biased in the forward direction to make the diode conductive. A voltage controlled oscillation device characterized in that the collector current is decreased by increasing the base fixed bias resistance value of the amplifier to decrease the base current.