JPH07135427A - High frequency mixer circuit - Google Patents

Abstract

PURPOSE:To obtain a small sized high frequency mixer circuit from which the same conversion gain as the case with using a conventional microstrip line by inputting efficiently an RF signal input and an LO signal input to a base of a common emitter transistor(TR) of a mixer circuit as a matching circuit with respect to inputs. CONSTITUTION:Bases of a 1st TR1 and 2nd TR2 of common emitter connection receive an input local carrier signal LO and a radio signal RF respectively and each collector output is given to a base of a common emitter 3rd TR3. Then an emitter of the 1st TR1 and a collector of the 2nd TR2 are connected by an inductor 4 isolated in terms of high frequency and conducted directly in terms of DC thereby obtaining an output signal IF whose frequency is converted from a collector of the 3rd TR3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency mixer circuit for multiplying a radio signal RF input to a radio receiver or the like and a local carrier signal LO to obtain an intermediate frequency signal IF having a difference frequency.

[0002]

2. Description of the Related Art A conventional high frequency mixer circuit, as shown in FIG. 4, is in the form of a grounded emitter type transistor amplifier.
RF signal and L are added to the base of transistor Tr whose emitter is grounded.
O signal is input and the frequency converted IF from the collector
A circuit configuration for extracting a signal is known. The microstrip line in the figure is an impedance matching circuit that efficiently inputs the input RF and LO signals to the base of the Tr. The length of the microstrip line is such that the impedance at the RF frequency is open when the LO signal input filter LO FiL is seen from point A in the figure.
To be visible. For example, the output impedance of LO FiL is 50 ohms (center of Smith chart),
When there is a short circuit at the RF frequency (the left edge of the Smith chart),
If you connect a microstrip line of 1/4 wavelength of RF frequency (phase rotates 180 °) to LO FiL as shown in the figure, the impedance at that RF frequency seen from point A becomes open, and RF The LO FiL impedance cannot be seen from the input port (similar to no impedance), so the RF signal input is efficiently input to the Tr base. Similarly, the LO signal input is also efficiently input to the base of the Tr and a high frequency conversion gain is obtained.

[0003]

However, in this conventional method, the microstrip line requires two lines for inputting the RF signal and for inputting the LO signal, and in order to rotate the phase by 180 °, In the frequency band of 800 MHz, the microstrip line length (1/4 wavelength) is about 50 mm, so the mounting area is large. An object of the present invention is to enable RF signal input and LO signal input to be efficiently input to the base of an emitter-grounded transistor Tr for output, without using a microstrip line, and equivalent to a conventional circuit. It is to realize a small high-frequency mixer circuit that can obtain a conversion gain.

[0004]

To achieve this object, the basic concept of the high frequency mixer circuit of the present invention is that the collector of the grounded-emitter transistor Tr generally has a high output impedance (several hundred to several kilo Ω). Focusing on, the conventional circuit microstrip line is replaced by a grounded-emitter transistor Tr. As shown in the principle diagram of FIG. 1, the basic configuration is to input the input LO signal and the RF signal to the bases of the first transistor 1 and the second transistor 2, both of which have the emitters grounded. The collector output of the first transistor is input to the base of the third transistor 3 whose emitter is grounded, and
The emitter of 1 and the collector of the second transistor 2 are connected by an inductor 4 which is isolated in terms of high frequency and is directly connected in terms of direct current, and an output signal (IF) whose frequency is converted is output from the collector of the third transistor 3. Configure to get.

[0005]

In the present invention, referring to the principle diagram of FIG. 1, the input LO
The signal is amplified by the first transistor 1 whose emitter is grounded by the capacitor 6 at high frequency, and the RF signal input is amplified by the second transistor 2 whose emitter is grounded by the capacitor 7, and both collector outputs are The same grounded-emitter transistor 3 through the coupling capacitors 8 and 9, respectively.
Entered in the base of. The collector of transistor 2 is
Since the inductor 4 is insulated from the emitter of the transistor 1 in terms of high frequency, it exhibits a high impedance for a high frequency signal and prevents the collector output of the transistor 2 from leaking into the transistor 1. Therefore, the LO signal input is efficiently input to the base of the transistor 3, and the RF signal input is also efficiently input to the base of the transistor 3. Therefore, a high conversion gain output signal IF is obtained from the collector of the transistor 3, and the mounting area of the entire high-frequency mixer circuit is reduced.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The principle diagram of FIG. 1 is shown as it is, and the configuration of a high frequency mixer circuit according to an embodiment of the present invention is shown. 2 and 3 are configuration diagrams of a high frequency mixer circuit according to another embodiment of the present invention. (1) to (3) of FIG. 2 correspond to claims 2 to 4, and (1) to (3) of FIG. 1)
~ (3) corresponds to claims 5 to 7, respectively. In (1) of Figure 2,
The LO signal and RF signal are input to the bases of transistor 1 and transistor 2 whose emitters are individually grounded both in terms of high frequency and DC, and the collector outputs of these are input to the base of transistor 3 whose emitter is grounded. Input into the base and take out the frequency converted output signal IF from its collector. In (2) of Fig. 2, the emitter of transistor 1 is connected to resistor R
It is the same as (1) in FIG. 2 except that it is connected to the collector of the transistor 2 via. In (3) of Figure 2, the transistor
Connect the emitter of 1 and the emitter of transistor 2,
(1) in Fig. 2 except that it is grounded via a resistor R and a capacitor C
Is the same as. In (1) of FIG. 3, the emitter of the transistor 1 is connected to the collector of the transistor 2 via the resistor R1, and the emitter of the transistor 2 is connected to the collector of the transistor 3 via the resistor R2. Same as 1). 3 (2) is the same as FIG. 2 (2) except that the collector of the transistor 1 is connected to the base of the transistor 3 and the collector of the transistor 2 is connected to the emitter of the transistor 3. In (3) of FIG. 3, the RF signal and the LO signal are input to the collectors of the diode-connected transistors 1 and 2, respectively, and the emitter outputs of them are input to the base of the transistor 3, Connected to get the output signal IF from the collector of 3.

[0007]

As described above, according to the present invention, a compact high frequency mixer which can obtain a conversion gain equivalent to that of a mixer circuit using a conventional microstrip line without using a microstrip line having a large mounting area. The effect that the circuit can be realized is obtained.

[Brief description of drawings]

FIG. 1 is a principle diagram showing a basic configuration of a high-frequency mixer circuit according to claim 1 of the present invention.

FIG. 2 is a configuration diagram of an embodiment corresponding to claims 2 to 4 of the present invention.

FIG. 3 is a configuration diagram of an embodiment corresponding to claims 5 to 7 of the present invention.

FIG. 4 is a configuration diagram of a conventional high frequency mixer circuit.

[Explanation of symbols]

1 is the first grounded emitter which receives the local carrier signal LO
Transistor 2 is a second transistor with a grounded emitter that receives a radio signal RF, and 3 is an output LO of the first transistor
And an output RF of the second transistor to output an intermediate frequency signal IF having a difference frequency, and the third transistor having a grounded emitter.

Front page continuation (72) Inventor Mitsuhiko Mitsuho 2-1-1 Kita-Ichijo Nishi, Chuo-ku, Sapporo, Hokkaido Fujitsu Hokkaido Digital Technology Co., Ltd. No. 1 Fujitsu Hokkaido Digital Technology Co., Ltd. (72) Inventor Takafumi Mimuro 2-1-1 Kitaichijo Nishi, Chuo-ku, Sapporo-shi, Hokkaido Fujitsu Hokkaido Digital Technology Co., Ltd.

Claims (7)

[Claims] 1. An input radio signal (RF) and a local carrier signal (L)
O) and a high frequency mixer circuit that outputs an intermediate frequency signal (IF) of the difference frequency, both are connected to the bases of the first transistor (1) and the second transistor (2), both of which have their emitters grounded. , The input local carrier wave signal (LO) and the radio signal (RF) are input respectively, and the respective collector outputs are input to the base of the third transistor (3) having a grounded emitter, and at the same time, of the first transistor (1). The emitter and the collector of the second transistor (2) are isolated from each other in terms of high frequency and connected by a direct inductor (4) in terms of direct current, and the frequency-converted output signal (IF ) Is a high-frequency mixer circuit. 2. The high frequency mixer circuit according to claim 1, wherein the emitters of the first transistor (1) and the second transistor (2) are grounded both in terms of high frequency and in terms of direct current. . 3. The high-frequency mixer circuit according to claim 1, wherein the emitter of the first transistor (1) is connected to the collector of the second transistor (2) via a resistor (R). 4. The emitter of the first transistor (1) and the emitter of the second transistor 2 are connected to each other, and a resistor is connected.
The high frequency mixer circuit according to claim 1, wherein the high frequency mixer circuit is grounded through (R) and a capacitor (C). 5. The emitter of the first transistor (1) is connected to the collector of the second transistor (2) via the first resistor (R1), and the emitter of the second transistor (2) is connected to the collector of the second transistor (2). The high-frequency mixer circuit according to claim 1, wherein the high-frequency mixer circuit is connected to the collector of the third transistor (3) through the second resistor (R2). 6. The collector of the first transistor (1) is connected to the base of the third transistor (3), and the collector of the second transistor (2) is connected to the emitter of the third transistor (3). The high frequency mixer circuit according to claim 1, wherein 7. The first and second transistors (1) and (2) are diode-connected with their collectors and bases connected to each other, and the collectors of the first and second transistors are connected to each other by input radio signals. Inputting a signal (RF) and a local carrier signal (LO), inputting each emitter output to the base of the third transistor (3), and obtaining an output signal (IF) from the collector of the transistor (3). The high frequency mixer circuit according to claim 1, wherein: