SU1053268A1 - Balanced mixer - Google Patents

Abstract

BALANCE MIXER containing the input transformer. Completed with two output windings, the connection point of which is a heterodyne input, two field-effect transistors connected according to a common gate circuit, and an output transformer connected to field-effect transistors, characterized in that, in order to reduce the schum coefficient and the necessary the local oscillator, inductances are connected between the outputs of the input transformer and the sources of the field-effect transistors, and capacitors are connected in parallel with the output windings of the input transformer.

Description

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O // The invention relates to radio engineering and can be used in radio-frequency technology and communication technology in frequency conversion devices. A high-frequency balanced mixer is known, containing two field-effect transistors connected according to a circuit with a common gate, input and output balancing transformers connected, respectively, to the sources and outlets of field-effect transistors. The input transformer splits the input signal into two, which are in antiphase at the source of the field effect transistors. The heterodyne signal is fed to the midpoint of the secondary winding of the input transfer of the mator And through this winding enters the sources of field-effect transistors in-phase. On the 1-phase primary winding of the output transformer, the common mode local oscillator signal is suppressed, and the components with 15 opposite phases, containing the difference and total frequencies of the input signals, are added Medostat 9M of this balanced mixture of bodies is a poor matching. circuits of the input signal and the local oscillator, which leads to a deterioration of the noise figure and the need for the local oscillator power. Closest to the proposed technical entity is a balanced mixer containing an input transformer, filled with two output windings, the junction point of which is a heterodyne input, two field-effect transistors, 1X with a common gate, and an output transformer connected to the drains of field-effect transistors, while the sources of field-effect transistors are connected to the outputs of the input transformer. 2. A disadvantage of the known balance mixer is the deterioration of matching with the signal source at high frequencies, due to the influence of the input capacitance of the field-effect transistors, which worsens the noise ratio of the balanced mixer. The disadvantage is also poor coordination with the local oscillator, the signal of which is supplied to the sources of the field-effect transistors through the inductances connected in series to the output of the inverter. This leads to an increase in the required heterodyne power. The purpose of the invention is to reduce the noise figure and the necessary local oscillator power. The goal is achieved by the fact that in a balanced mixer containing an input transformer made with two output windings, the connection point of which is a heterodyne input, two field-effect transistors connected in a circuit with a common gate, and an output transformer connected to the drains of field-effect transistors, inductances are connected between the outputs of the input transformer and the sources of the field-effect transistors, and capacitors are connected in parallel with the output windings of the input transformer. FIG. 1 shows the basic electrical circuit of the proposed balanced mixer; in fig. 2 - the equivalent circuit of the balanced mixer on the input signal; in fig. 3 - equivalent circuit balanced mixer signal of the local oscillator. The balanced mixer contains an input transformer 1 with two output windings 2 and 3, a capacitor 4 and 5, inductance 6 and 7, field-effect transistors 8 and 9, an output transformer 10, an input AND signal source, a local oscillator input 12, a power source 13. Balanced mixer works as follows. The input signal 0 (4 from input 11 is fed to the input transformer. 1. The local oscillator signal, from input 12 enters the connection point of capacitors 4 and 5. From the output windings 2 and 3 signals through inductance 6 and 7i, field-effect transistors 8 and 9 pass to output transformer 10. The values of inductances 6 and 7 of inductors are chosen in such a way that they, together with the input capacitances 14 and 15 (Fig. 2) of field rangers 8 and 9, form polynomial low-pass filters with cut-off frequencies equal to or exceeding the highest frequency of the range in single frequencies, and characteristic resistances 16 and 17 (Fig. 2) equal to R 1 (5, where 5 is the steepness of the field-effect transistors 8 and 9. The fact that the Input capacitors 14 and 15 of the field-effect transistors 8 and 9 are included in the polynomial low-pass filters, matching of field-effect transistors 8 and 9 with a source, the signal with a higher frequency does not deteriorate and remains good up to the cut-off frequency of polynomial low-pass filters. Capacitors 4 and 5 shunting the conductors of the input transformer 1 are compatible with distribution capacitors 18 (FIG .3) and inductances 19 you suitable winding 2 (H) of the input transformer 1, inductance mn 6 and 7 inductors and input capacitances 14 and 15 of the field-effect transistors 8 and 9, form a P1-1 low-pass filter (1). 3), the cut-off frequency of which iqjeBbi is the cut-off frequency of the polynomial low-pass filters, and the characteristic impedances 2O, co) they are one and close to the input resistances of the field-effect transistors 8 and 9, are equivalent. A diagram of one of these filters (for the upper arm of the circuit in FIG. 1) is shown in FIG. 3. Since the inputs of both ETUs of the filters are connected in parallel, good field matching of the fanzistors 8 and 9 with the heterodyne of the cut-off frequency of the t-derived filters is ensured. low frequencies. Thus, a positive effect is achieved due to a significant improvement in the matching of the field transistors with the signal source and heterodyne. significantly reduces the noise ratio of the mixer and the necessary local oscillator power. The noise coefficient of the proposed balanced mixer in tests in the frequency range of 1–2 OUT MGP is 4.5 dB (known 6.5 dB), and the local oscillator power 1O is 2O mW (the known one has 150 mW).

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Claims (1)

A BALANCE MIXER containing an input transformer made with two output windings, the connection point of which is a heterodyne input, two field-effect transistors connected according to a common-gate circuit, and an output transformer connected to the drains of field-effect transistors, characterized in that, in order to reduce noise figure and the required local oscillator power, inductors are connected between the outputs of the input transformer and the sources of field-effect transistors, and parallel to the output windings of the input transformer capacitors. SU „„ 1053268