CN211457088U - Triode mixing experimental device adopting local oscillator multi-injection mode - Google Patents

Abstract

The utility model relates to a mixing technical field, concretely relates to triode mixing experimental apparatus of many injection modes of local oscillator, including the local oscillator signal generator module that connects gradually, emitter follower module and mixer module. This triode mixing experimental apparatus of many injection modes accessible change over switch selects the injection mode of local oscillator signal, and has the effect that the frequency mixing gain is enlargied, the harmonic is little.

Description

A Triode Mixing Experiment Device Using Local Oscillator Multi-injection Mode

technical field

The utility model belongs to the technical field of frequency mixing, in particular to a triode frequency mixing experiment device with a local oscillator multi-injection mode.

Background technique

The frequency mixing circuit is a spectrum shifting circuit, which refers to the frequency conversion of the high-frequency carrier signal or the modulated wave signal, and converts it into a signal of a specific fixed frequency, and the converted signal, its internal spectrum structure and frequency. The modulation type remains the same, only the carrier frequency of the signal changes. There are many types of mixer circuits, commonly used are analog multiplying mixers, diode balanced mixers, ring mixers, triode mixers, etc., among which triode mixers are the most commonly used. Both mixer circuits and frequency conversion circuits belong to this type of circuit. The frequency conversion circuit and the frequency mixing circuit are exactly the same in circuit function, and both belong to the spectrum shifting circuit, and the difference is only in the circuit structure. The mixer circuit is equipped with an independent local oscillator signal generating circuit, in which the mixer tube and the local oscillator tube work independently.

The frequency conversion circuit is mostly "local oscillator" and "mixing" sharing one-stage transistor. It has the advantages of simple circuit and fewer components, but it also has disadvantages such as low mixing gain and poor stability. It is often used for circuit index requirements. low equipment. For example, most radios use frequency conversion circuits, and mixing circuits are often used in equipment with high electrical requirements due to their good working stability, such as TV circuits, radio communication circuits, etc.

According to the different injection points of the "local oscillator" signal, the triode mixing circuit is divided into two circuit forms: "base injection" and "emitter injection". According to the different models of the triode, the injected local oscillator voltage requirements are also different, generally should be selected between 200 ~ 400mV _PP . Whether the DC bias voltage of the mixer tube is appropriate is also an important condition that affects the mixing gain of the circuit. The mixer should have an optimal static DC operating point. If the collector current IC is too large or too small, the mixing gain of the mixer will be reduced. Under normal circumstances, it is more appropriate to control the quiescent current IC of the mixer tube between 0.2 and 1 mA.

The main technical indicators of the mixing circuit are the mixing voltage gain and the mixing noise and interference. The mixing gain refers to the ratio of the voltage amplitude Vgm of the intermediate frequency signal output by the mixing circuit to the input signal Vsm of the mixing circuit, and is often expressed in decibels dB. During the operation of the mixer circuit, many new combined frequency components will be generated, and noise signals will also be generated when the transistor is working. There are other interference factors outside the circuit, which will cause interference to the mixer, which is called mixing interference. A mixing circuit with good performance should have performance indicators such as high mixing gain, low distortion, and low noise figure.

Utility model content

The purpose of the present invention is to provide a device capable of realizing frequency mixing by selecting the base electrode to inject the local oscillator or the emitter to inject the local oscillator signal.

In order to achieve the above purpose, the technical scheme adopted by the present invention is: a local oscillator multi-injection triode mixing experiment device, comprising a local oscillator signal generator module, an emitter follower module and a mixer module connected in sequence.

In the above-mentioned local oscillator multi-injection mode triode mixing experiment device, the local oscillator signal generator module includes a BG1 crystal and peripheral components.

In the above-mentioned local oscillator multi-injection triode mixing experiment device, the emitter follower module includes BG2, which is used to adjust the position of the center point of the BG2 emitter potentiometer W1, thereby adjusting the output voltage amplitude of the local oscillator.

In the above-mentioned local oscillator multi-injection triode mixing experiment device, the mixer module includes triode mixing tube BG3 and peripheral element mid-cycle filter B2.

The beneficial effects of the utility model are as follows: 1. Selecting the base injection into the local oscillator or the emitter injection by switching the switch; 2. Amplifying the mixing gain; 3. Small harmonics.

Description of drawings

Fig. 1 is the system composition block diagram of an embodiment of the present utility model;

FIG. 2 is a system circuit diagram of an embodiment of the present invention.

Detailed ways

The embodiments of the present utility model will be described in detail below with reference to the accompanying drawings.

In the mixing experiment, the selectivity of the local oscillator signal injection of the triode mixing device is limited. The multi-injection triode mixing experimental device can solve the above problems well, and realizes the choice of the base injection local oscillator or the emitter injection by switching the switch.

As shown in Figure 1, a local oscillator multi-injection triode mixing experimental device includes the following modules: a mixer module, a local oscillator signal generator module, and an emitter follower module. The local oscillator signal generator module, the emitter follower module, and the mixer module are connected in sequence. The emitter follower module selects base injection LO or emitter injection by switching the switch.

As shown in Figure 2, the triode mixing tube and the mid-cycle filter of the peripheral components together form a frequency mixing and frequency selection circuit. The local oscillator circuit that provides the carrier signal for the mixing stage consists of a BG1 crystal and peripheral components. BG2 is a first-order emitter follower circuit, which is set up to facilitate the adjustment of the output voltage amplitude of the local oscillator.

In addition, the mixer module is composed of a triode mixer BG3 and a mid-cycle filter B2 of peripheral components. The EC1 port is the power supply port of the triode mixing circuit. The F0 port is the input end of the carrier signal, and the signal is coupled to the triode mixer and the integrated mixer respectively through the capacitor C10.

In addition, the local oscillator signal generator module is composed of BG1 crystal and peripheral components, and provides carrier signal for the mixing stage. The voltage input of the local oscillator signal generator module is 12V. The local oscillator frequency is determined by the natural oscillation frequency of the crystal, and its frequency value is generally printed directly on the crystal element. The band-pass filter is composed of a high-frequency mid-cycle transformer, which already contains an IF resonant capacitor C0, which resonates in parallel with the mid-cycle inductor L at the 455kHz frequency point, and the selected IF frequency signal is passed through the IF transformer (middle frequency). cycle) secondary coil coupling output.

In addition, the emitter follower module is mainly composed of BG2, which is set for the convenience of adjusting the output voltage amplitude of the local oscillator. Adjusting the position of the center point of the BG2 emitter potentiometer W1 can easily control the strength of the local oscillator signal injected into the mixing stage. The switch K1 is an injection mode switch. Through it, you can choose whether the local oscillator signal is injected from the base or injected from the emitter into two local oscillator injection modes. Turn switch K1 to gear 1 to select the working mode of emitter LO injection; switch K1 to gear 2 to select the working mode of base LO injection.

It should be understood that the parts not described in detail in this specification belong to the prior art.

Although the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, those of ordinary skill in the art should understand that these are only examples, and various changes or modifications may be made to these embodiments without departing from the scope of the present invention. principle and substance. The scope of the present invention is limited only by the appended claims.

Claims (4)

1. a triode frequency mixing experiment device of a local oscillator multi-injection mode, is characterized in that, comprises the local oscillator signal generator module connected successively, emitter follower module and mixer module. 2 . The triode mixing experiment device of the local oscillator multi-injection mode according to claim 1 , wherein the local oscillator signal generator module comprises a BG1 crystal and peripheral components. 3 . 3. the triode mixing experiment device of local oscillator multi-injection mode as claimed in claim 1, is characterized in that, emitter follower module comprises BG2, is used for adjusting the position of BG2 emitter potentiometer W1 center point, thereby adjusts this. Vibration output voltage amplitude. 4. The local oscillator multi-injection triode mixing experiment device according to claim 1, wherein the mixer module comprises a triode mixer BG3 and a peripheral element mid-cycle filter B2.

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