JPH0152924B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to television tuner circuits and
This invention relates to a frequency mixing circuit using an integrated circuit in the high frequency range, which can be used in CATV 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 high frequency signals, and terminal C is an output terminal for intermediate frequency signals. A reference potential V ₁ is applied to the high-frequency signal applied from terminal B, and this is supplied to the base of transistor 1 and further applied to the base of transistor 3 through resistor 2 . The base of the transistor 3 has its high frequency component reduced by the transistor 4 and is applied with a DC potential. The emitters of transistors 1 and 3 are coupled to each other via resistors 5 and 6, and a constant current source 7 is connected to the coupling point. The high frequency signals are amplified by transistors 1 and 3, respectively. Transistor 1, 3
The collectors of are connected to the common emitters of transistors 8 and 9 and to the common emitters of transistors 10 and 11, respectively. Transistors 8, 9, 10,
Reference numeral 11 is connected between the bases of transistors 8 and 11 and between the bases of transistors 9 and 10, respectively.

A local oscillation signal is applied from a terminal A via a capacitor 12 to the common base of the transistors 8 and 11, and a reference potential V ₂ from a reference potential source 14 is applied via a resistor 13. Also, the transistor 9,
The common base of 10 is connected to a reference potential source 14 via a resistor 15 and grounded via a capacitor 16. The common collectors of transistors 8 and 10 are connected to a power supply terminal. Further, 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, transistors 8 and 11
The potential of the common base of V _D , V _E , transistors 9,
10 common base potential V _F , transistor 1
Considering the DC potential at each point, assuming that the base potential of V _G is V _G and the base potential of transistor 3 is V H, V _G > V _H due to the potential drop due to resistor 2, and since the local oscillator signal is added, V _D , V _E ＞V _F. this is,
If the capacitance 16 is the capacitance in the integrated circuit, at most
This phenomenon occurs because sufficient attenuation of high frequency components cannot be ensured because only pF can be configured. V _G
> V _H , V _D , V _E > V _F , the current flowing into the common collectors of transistors 8 and 10 becomes larger than the current flowing into the common collectors of transistors 9 and 11, and now For example, if resistors 13 and 15 are 3.3KΩ, resistors 5 and 6 are 100Ω, and resistor 2 is 6.6KΩ, and when power supply voltage Vcc = 12V and constant current source 7 is supplied with I = 3mA, transistor 8, A value of 1.7 mA was obtained for the common collector of transistors 9 and 11, and a value of 1.3 mA was obtained for the common collector of transistors 9 and 11, respectively.

Therefore, the load resistor 17 is connected to the output terminal C.
The disadvantage is that the conversion gain obtained at 1.3 mA and only third-order distortion can be secured, and compared to when the circuit is perfectly balanced and flows 1.5 mA, the conversion gain is 3 dB and the third-order distortion (intercept point) is degraded by 3 dB. It was hot.

OBJECTS OF THE INVENTION It is an object of the present invention to provide means for improving conversion gain and third-order distortion when constant power sources have the same value.

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 one base of two high frequency amplification transistors forming a double-balanced circuit, and supplies the other to a first resistor. of the first to fourth transistors constituting the double-balanced circuit. The emitters of the first and second transistors are connected in common, the emitters of the third and fourth transistors are also connected in common, and the common emitter of the first and second transistors is connected to the collector of one of the high frequency amplification transistors. , the common emitters of the third and fourth transistors are respectively connected to the collectors of the other high frequency amplification transistor, a local oscillator signal is supplied to the common base of the first and fourth transistors, and this common base is connected to the common base of the second transistor. connected to a reference potential source via a resistor, a common base of the second and third transistors being grounded via a second capacitor, and connected to the reference potential source via a third resistor; , the collectors of the fourth transistor are commonly connected and connected to the power supply terminal, the collectors of the first and third transistors are commonly connected and connected to the power supply terminal via a load resistor, and this load resistor and The intermediate frequency output signal is obtained from the connection point of the common collector, and it is possible to obtain an intermediate frequency output signal with higher power, and the conversion gain,
Both third-order distortion can be significantly improved.

Description of examples FIG. 2 shows the configuration of an embodiment of the present invention.

In the figure, the structure is the same as that in FIG. 1 except for the position where the resistor 17 is inserted, so redundant explanations will be omitted. 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 between the common collector of the transistors 8 and 10 and the power supply terminal.
0 is supplied to the output terminal C from the common collector. As explained in Fig. 1, when the current value I of the constant current source 7 is 3 mA, 1.7 mA is obtained at the common collector of the transistors 8 and 10, and the conversion gain is 6 dB compared to the example shown in Fig. 1. , a 6dB improvement was also obtained in third-order distortion (intercept point).
This provides an improvement of 3 dB compared to when the circuit is perfectly balanced (when 1.5 mA flows), and is an especially effective method when it is necessary to limit the current as much as possible, such as in integrated circuits. It can be said that there is.

Effects of the Invention As described above, according to the present invention, by making the current balance of the double-balanced type unbalanced and configuring it to be able to supply more power 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]

FIG. 1 is a circuit diagram of a frequency mixing circuit in a conventional example, and FIG. 2 is a circuit diagram of a frequency mixing circuit in an 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...Transistors forming a double-balanced mixed circuit, 2, 5, 6, 1
3, 15, 17...Resistance constituting the double-balanced mixed circuit, 4, 16...Grounding capacitance, 7...
Constant current source, 14...Reference potential source.

Claims (1)

[Claims] 1. Divide the high-frequency input signal into two, supply one of them to the base of two high-frequency amplification transistors forming a double-balanced circuit, and supply the other to the base of the other high-frequency amplification transistor through the first resistor. and the base of the other high frequency amplification transistor is grounded via the first capacitor, and the first to
Among the fourth transistors, the emitters of the first and second transistors and the emitters of the third and fourth transistors are connected in common, respectively, and the common emitter of the first and second transistors is connected to the emitters of the first and second transistors. The common emitters of the third and fourth transistors are connected to the collectors of the other high-frequency amplification transistor, and a local oscillation signal is supplied to the common base of the first and fourth transistors, and the common base is connected to the collector of the third and fourth transistors. connected to a reference potential source via a second resistor, grounding the common base of the second and third transistors via a second capacitor, and connecting to the reference potential source via a third resistor; The collectors of the second and fourth transistors are commonly connected to the power supply terminal, the collectors of the first and third transistors are commonly connected and each connected to the power supply terminal via a load resistor, and the load A frequency mixing circuit characterized in that an intermediate frequency output signal is obtained from a connection point between a resistor and a common collector.