JPS60194810A - Frequency mixing circuit - Google Patents

Abstract

PURPOSE:To obtain a means improving the conversion gain and a ternary distortion at a constant current value by constituting the circuit that a current balance of double balance form is unbalanced so as to supply much power to an output terminal. CONSTITUTION:A resistor 17 is connected between a common collector of transistors (TR) 8, 10 of a double balance type mixing circuit and a power terminal and an intermediate frequency output is applied to an output terminal C from the common collector of the TRs 8, 10. A current of 1.7mA is obtained at the common collector of the TRs 8, 10 when a current value I of a constant current source 7 is 3mA, and improvement of 66dB of the ternary distortion and 6dB of the conversion gain is attained in comparison with a conventional circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a frequency mixing circuit using an integrated circuit in the high frequency range, which can be used in television tuner circuits, 0ATV converters, satellite broadcast receivers, etc. .

Conventional configuration and its problems An example of a conventional frequency mixing circuit is shown in FIG.

Terminal A in the figure is a local oscillator signal, terminal B is an input terminal for a high frequency signal, and terminal C is an output terminal for an intermediate frequency signal. A reference potential v1 is applied to the high frequency signal applied to the terminal B, which is supplied to the base of the transistor 1, and further applied to the base of the transistor 30 through the resistor 2. The base of the transistor 3 has a high frequency component reduced by the transistor 4, and a DC potential is applied to the base of the transistor 3.

The emitters of transistors 1 and 3 are connected via resistors 5 and 6,
They are coupled to each other, and a constant current source 7 is connected from the coupling point. The high frequency signals are each amplified by transistors 1.3. The collectors of transistors 1 and 3 are connected to the common emitters of transistors 8 and 9 and transistor 10, respectively.
．． 11 common emitters. transistor, 8
, 9, 10.11 are connected between the bases of transistors 8 and 11, and between the bases of transistors 9 and 1Q. Local oscillation is connected to the common base of transistors 8.11 from terminal A via capacitor 12. At the same time as the signal is applied, the reference potential v2 of the reference potential source 14 is applied through the resistor 13. Also, the common base of transistor 9゜1o is resistor 1
It is connected to a reference potential source 14 via a capacitor 5 and grounded via a capacitor 16. The common collectors of transistors 8 and 10 are connected to a power supply terminal. Further, the common collectors of the transistors 9 and 11 are connected to a power supply terminal via a resistor 17.

In this way, a double-balanced frequency mixing circuit is constructed, and a frequency mixing signal is supplied to the output terminal C from the common collector of the transistors 11 and 9.

By the way, in the configuration shown in Fig. 1, the potential of the common base of transistors 8 and 11 is VD, vEl, the potential of the common base of transistor 9゜1o is VF1, the base potential of transistor 1 is vGl, and the base potential of transistor 3 is vH, and the DC current at each point is Considering the potential drop due to resistor 2, vG>vH, and since the local oscillation signal is added, VD, v
E〉VF. This is a phenomenon that occurs because the capacitor 16 cannot be configured as a capacitor of several pFL at most in an integrated circuit, and therefore sufficient attenuation of high frequency components cannot be ensured.

VG) VH, VD, VE>VF (D) If such a potential difference occurs, the current flowing into the common collector of transistors 8 and 10 will be much smaller than the current flowing into the common collector of transistors 9 and 11. For example, if the resistance is 13.15, it will be 3.3Ω, and if the resistance is 5.6, it will be 100Ω.
Ω, resistor 2 and 6.6 Ω are used, and the power supply voltage Vcc
When I = 3 mA flows into constant current source 7 when voltage = 12 V, 1 is applied to the common collector of transistors 8゜10.
．． 7rnA,) A value of 1.3 mA was obtained in the common collector of transistor 9.11.

Therefore, the output terminal C can only secure the conversion gain and third-order distortion obtained with the load resistor 17 and 1.3 mA, and the conversion gain is 3 dB compared to when the circuit is perfectly balanced and 1.5 mA flows. , even the third-order distortion (intercept point) is 3.
It had the disadvantage of dB deterioration.

Purpose of the Invention The present invention provides conversion gain,
3. The purpose of this invention is to provide a means for improving second-order distortion.

Structure of the Invention The frequency mixing circuit according to the present invention divides a high frequency input signal into two, supplies one of them to the base of two high frequency amplification transistors forming a double-balanced circuit, and supplies the other to the base of the first resistor. is supplied to the base of the other high-frequency amplification transistor through the first capacitor, and the base of the other high-frequency amplification transistor is grounded through the first capacitor. The first of these. The emitters of the second transistors are connected in common, and the third . The emitters of the fourth transistor are also connected in common, and the emitters of the fourth transistor are also connected in common. The common emitter of the second transistor is connected to the collector of one of the high frequency amplification transistors, and the third. The common emitter of the fourth transistor is connected to the collector of the other high frequency amplification transistor, respectively, and the local oscillation signal is transmitted to the first... A common base of a fourth transistor is connected to a reference potential source through a second resistor, and a common base of a fourth transistor is connected to a reference potential source through a second resistor. The common bases of the third transistors are grounded via a second capacitor and connected to the reference potential source via a third resistor, and the common bases of the third transistors are connected to the reference potential source via a third resistor. The collectors of the fourth transistors are connected in common and connected to the power supply terminal, and the collectors of the fourth transistors are connected in common to the power supply terminal. The collectors of the third transistors are connected in common and connected to the above power supply terminal via a load resistor, and an intermediate frequency output signal is obtained from the connection point between the load resistor and the common collector, which provides greater power. It is possible to obtain an intermediate frequency output signal of 1,000,000, and significantly improve both conversion gain and third-order distortion.

Description of examples The configuration of one embodiment of the present invention is shown in FIG.

In the figure, the configuration is the same as that in FIG. 1 except for the position where the resistor 17 is inserted, so redundant explanations will be omitted. 4 The resistor 17 is connected between the common collector of the transistors 8 and 10 and the power supply terminal, and the intermediate frequency output is connected from the common collector of the transistors 8 and 1 to the output terminal C.
It is supplied to As explained in Fig. 1, the common collector of the transistors 8 and 100 obtains 1.7 mA when the current value of the constant current source 7 is 3 mA, and the conversion gain is 6 dB compared to the example shown in Fig. 1. , an improvement in edB was also obtained for third-order distortion (intercept point). This is an improvement of 3 dB compared to when the circuit is completely balanced (when 1.5 mA flows), and is an especially effective method when it is necessary to limit the current as much as possible in integrated circuits, etc. You can say that.

Effects of the Invention As described above, according to the present invention, by making the current balance of the double-balanced type unbalanced so that more power can be supplied to the output terminal, the conversion gain and third-order distortion can be reduced at a constant current value. This means that favorable conditions can be secured.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a conventional frequency mixing circuit;
The figure is a circuit diagram of a frequency mixing circuit in one embodiment of the present invention. A: Local oscillation signal input terminal, B: High frequency signal input terminal, C: Frequency mixing output terminal,
1, 3゜8.9, 10.11... Transistor constituting a double balanced mixed circuit, 2, 5, 6, 1
3゜15.1γ...Resistance configuring the double-balanced mixed circuit, 4,16...Grounding capacitance, 7.
... Constant current source, 14... Reference potential source. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (1)

[Claims] The high-frequency input signal is divided into two parts, one of which is supplied to the base of two high-frequency amplification transistors forming a double-balanced circuit, and the other is supplied to the base of the other high-frequency amplification transistor via the first resistor. and the base of the other high-frequency amplification transistor is grounded via the first capacitor, and the first to fourth transistors constituting the double-balanced circuit are connected to the base of the other high-frequency amplification transistor. the emitter of the second transistor, the third . The emitters of the fourth transistors are connected in common, and the emitters of the first and second transistors are connected in common. The common emitter of the second transistor is connected to the collector of one of the high frequency amplification transistors, and the third. The common emitter of the fourth transistor is connected to the collector of the other high frequency amplification transistor, respectively, and the local oscillation signal is transmitted to the first... a common base of a fourth transistor, the common base being connected to a reference potential source via a second resistor; The common bases of the third transistors are grounded via a second capacitor and connected to the reference potential source via a third resistor, and the common bases of the third transistors are grounded via a second capacitor and connected to the reference potential source via a third resistor.
The collectors of the fourth transistors are commonly connected to the power supply terminal. A frequency characterized in that the collectors of the third transistors are connected in common and each is connected to the power supply terminal through a load resistor, and an intermediate frequency output signal is obtained from a connection point between the load resistor and the common collector. Mixed circuit 0