KR950007835B1 - Quasi active bias circuit for balanced mixed - Google Patents

Abstract

The balanced mixer comprises two input ports for inputting a high frequency signal and a local oscillation frequency signal respectively, a phase adjusting means for distributing an electric power of the respective signal and adjusting its phase to receive the high frequency signal and the local oscillation frequency signal. The quasi active bias circuit comprises a middle frequency signal generator including two diodes which are connected to two output ports and generate the respective DC power supply with other polarity, for generating the middle frequency signal respectively provided from the phase adjusting means, a signal collector for collecting the generated middle frequency signal, and a common resistor arranged between the middle frequency signal generator and the signal collector to form a single closed circuit path of the DC power supply.

Description

Quasi active bias circuit of a balanced mixer

1 is a schematic diagram of a conventional rectangular waveguide balanced mixer.

2 is a block diagram of a conventional ultra-high frequency integrated circuit hybrid MIC hybrid balanced mixer.

3 is an equivalent circuit diagram of the nonlinear mixing part of FIG.

4 is a bias circuit diagram of a balanced mixer according to the present invention.

5 is a block diagram of an ultra-high frequency integrated circuit hybrid balanced mixer to which a bias circuit according to the present invention is applied.

6 is a block diagram of a rectangular waveguide type balanced mixer to which a bias circuit according to the present invention is applied.

* Explanation of symbols for main parts of the drawings

L21, L22: Inductor D11, D12: Mixing Diode

C21, C22, C23, C24: Capacitor R21: Resistor

The present invention relates to a balanced mixer used as a signal frequency converter in a wireless communication system. In particular, the present invention relates to a quasi-active bias circuit of a balanced horn mapper that automatically sets a direct current operating point of a balanced mixer.

It is well known that a balanced mixer, which is widely used as a signal frequency converter in a wireless communication system, optimizes the reception characteristics of a signal by varying the DC operating point of a mixing diode, which is a mixing nonlinear device.

Since the operation of optimizing the reception characteristics is performed after assembling the entire parts of the system due to the characteristics of the adjustment test, it is difficult to solve when a problem occurs.

Figure 1 shows a rectangular waveguide balanced mixer using an active bias circuit.

Techniques for such conventional mixers are described in "HANDBOOK of microwave techniques and equipment." by Harry E. Thomas. Prentice-Hall Inc., 1979. pp. 217.

The mixer includes a rectangular waveguide hybrid (1) for power distribution and phase control by inputting a radio frequency signal and a local oscillator frequency, two space portions 1a in the hybrid 1, Diodes D1 and D2 for generating an intermediate frequency signal (IF signal) of the two signals inputted to (1b), and a high frequency choke L1 for blocking high frequency signals leaking to the site coupled to the diode. DC bias is applied to (L2), (L3), (L4), intermediate frequency chokes (C1) and (C2), and the diodes (D1) and (D2), which are intended to prevent leakage of intermediate frequency signals. To the resistors R1 to R4 and R1'-R4 'for supplying and to the bias transistors T1 and T2 connected to the resistors R1 to R4 and R1' to R ⁺ '. It consists of a configured constant current circuit for active bias.

However, the mixer having the above-described structure must be provided with the choke (C1), (C2) for the intermediate frequency has been a factor to increase the complexity and manufacturing cost of this structure.

2 shows an ultra-high frequency integrated circuit hybrid balanced mixer using a passive bias circuit.

Techniques for such a conventional MIC hybrid balance mixer are described in C.P. Kurtis J.J. Taub, "Wide-Band X-Band Microstrip Image Rejection Balanced Mixer," IEEE Trans. Microwave Theory Tech., Vol. MTT-18, Dec 1970. pp, 1181-1182.

The mixer of FIG. 2 receives a high frequency signal (RF signal) and a local oscillation signal (LO frequency signal), and the MIC hybrid 5 for power distribution and phase control, and an intermediate frequency signal of the input signals. Diodes D3 and D4 for generating a signal, an ultrahigh frequency lowpass filter 2 and 2a for maintaining a DC grounding point (DC ground) of the diodes D3 and D4, and an ultrahigh frequency ground point of the diodes D3 and D4. Quarter wavelength transmission lines (4,4a) for setting RF ground, ultra-high frequency lowpass filters for manual bias setting (3,3a), and capacitors for lowpass filtering for intermediate frequency signal blocking (C13, C14) and inductors L11 and L12, load variable resistors R11 and R12 for setting the diode DC operating point, and bypass capacitors C11 and C12 for collecting intermediate frequency signals.

FIG. 3 is an equivalent circuit diagram of the nonlinear mixed portion of FIG. 2 (i.e., except for the microwave integrated circuit hybrid 5). The inductor L13 and diode D3 corresponding to the ultrahigh frequency low pass filter 2 of FIG. The intermediate frequency blocking choke (L11) and the load variable resistor (R11) shows that the path of the bias DC current is formed.

However, the mixer of FIG. 2 has a DC bias of the diodes D3 and D4 because the bias current generated by the rectified voltage of the local oscillation signal applied to the diodes D3 and D4 flows through different paths. It is difficult to keep the same.

In addition, since the physical size of the intermediate frequency chokes L11 and L12 is large, there is a problem in integrating the semiconductor. Accordingly, an object of the present invention is to provide a quasi-active bias circuit of a balanced mixer to obtain a DC operating point of an optimized mixing diode.

It is another object of the present invention to provide a similarly active bias circuit of a balanced mixer which can increase the integration of a circuit by implementing a balanced mixer without providing a bias circuit.

According to a feature of the present invention, an active bias circuit of a balance mixer includes two input terminals for inputting a high frequency (RF) signal and a locally generated frequency (LO) signal each having a constant phase difference from each other, and receiving the two input signals, 17. A balance mixer having means for distributing power and adjusting phase, said balance mixer comprising: means for generating an increased frequency signal contained in a signal provided by said phase adjusting means, comprising two diodes for generating a DC power source having a different polarity; And collecting means for collecting the intermediate frequency signal and outputting the collected signal, and resistance means for load disposed between the intermediate frequency signal generating means and the collecting means to form a single closed circuit path of the DC power. The single closed loop path of the DC power source is in turn a high frequency input terminal, a phase adjusting means, and one DC Diode source occurs, the resistance means and the other of the diodes, wherein the phase adjusting means, and is characterized in that formed in the input end of the local power frequency signal.

Means for maintaining the DC operation ground point of the intermediate frequency signal generating means may be added to the bias circuit. Means for bypassing some of the intermediate frequency signals generated from the intermediate frequency generating means may be added to the bias circuit.

The phase adjusting means in the bias circuit may be composed of an ultra-high frequency integrated circuit hybrid.

Referring to the present invention in detail based on the accompanying drawings as follows. 4 shows an equivalent circuit of the nonlinear mixing portion of the balanced mixer according to the invention shown in FIGS. 5 and 6.

That is, FIG. 4 shows an equivalent circuit of a portion excluding the high frequency integrated circuit hybrid 10 of FIG. 5 or the rectangular waveguide hybrid 15 of FIG.

In FIG. 4, an intermediate frequency signal bypass capacitor C21 is connected to one input port pory 1 via an inductor L21 of an ultrahigh frequency low pass filter and a mixing diode D11.

The intermediate terminal bypass capacitor C24 is connected to the output port port2 of the other side or the hybrid 10 via the inductor L22 of the ultra high frequency low pass filter and the mixing diode D12. A resistor R21 is connected between the rear ends of the two mixing diodes D11 and D12, and two capacitors C22 and C23 that receive the intermediate frequency output from the diodes D11 and D12 are connected in series. An intermediate frequency output terminal (IF output) is connected to the connection point of the capacitors C22 and C23.

Therefore, a constant phase difference from one side and the other (or an output terminal port of the hybrid 15) (Port 1), (Port 2) from a high frequency integrated circuit hybrid (not shown) or a linear waveguide hybrid (not shown) The high frequency (RF) and the local oscillation frequency (L0) signals inputted with are rectified by two mixing diodes D11 and D12, respectively.

At this time, the diodes D11 and D12 are generated with opposite (opposite) DC voltages, and the generated DC power supplies include the inductor L21, the mixing diode D11, the resistor R21, Only through the path of the only closed circuit consisting of the mixing diode (D12) and the inductor (L22).

The amount of current flowing through the path is a voltage value generated by the resistance value of the resistor R21 and the local oscillation frequency signal applied to the non-grounding terminals 4 and 5 of the two mixing diodes D11 and D12. Determined by

That is, since the bias currents of the two mixing diodes for determining the operating characteristics of the mixer are the same in any case, the amount of current flowing on the path by adjusting the strength of the local oscillation frequency signal and the resistance value of the resistor R21. This is determined.

Accordingly, the present invention can obtain the optimized DC operating point of the diode without using an external power source or an intermediate frequency band inductor for adjusting the mixer diode DC operating point, and additionally, the performance of the balanced mixer that is different from the manufacturing and design errors. It has a function to automatically compensate for degradation. Also, since it does not use the medium frequency choke inductor or bypass capacitor, which is a problem that is difficult to realize in the integrated circuit of the mixer, it is advantageous to the integrated circuit, so it is applied to the receiving circuit of the mobile communication or direct phase broadcasting system, which is a large demand field of the mixer. Can be.

5 shows an ultra-high frequency integrated circuit hybrid parallel mixer to which the quasi-active bias circuit of the present invention is applied. Although not shown in FIG. 4, the mixer of FIG. 5 receives a high frequency signal (RF input) and a local oscillation signal (L0 input), and is a means for power distribution and phase control. And diodes D11 and D12, which are means for generating an intermediate frequency signal of the input signals, and self-corresponding to portions indicated by inductors L21 and L22 in FIG. 4, and direct current operation of the diodes D11 and D12. Ultra high frequency low pass filter (11,12), means for maintaining the ground point (DC sound), and the capacitor consisting of the capacitor (C21, C24) and ground in Fig. 4 and sets the RF ground point (RF ground) of the diode A quarter wavelength transmission line (13, 14), a load variable resistor (R21) and a medium frequency signal, which are means for setting the DC operating point of the diode using the present invention, Means of passing It consists of a capacitor (C22, C23). The balanced mixer according to the present aspect as well as the bias circuits (L11, R11, C13, L12, R12, C12 in FIG. 2 or 3) connected to the rear ends of the two mixing diodes D11 and D12 are provided. Since the structure is simple, the integrated circuit can be realized because of the removal, and of course, the DC operating point is self-adjusted by the resistor R21 and the two mixing diodes D11 and D12.

6 shows a rectangular waveguide type balanced mixer to which the quasi-active bias circuit of the present invention is applied.

Although the mixer of FIG. 6 is not shown in FIG. 4, the rectangular waveguide hybrid 15 and the two spaces l5a, which are means for power distribution and phase control by receiving a high frequency signal (RF signal) and a local oscillation signal (L0 signal). 15b) diodes D11 and D12, which are means for generating an intermediate frequency signal (IF signal) of the signals input to the input signal, and a high frequency choke, which is a means for setting an ultra-high frequency ground point to block a high frequency signal leaked to the diode mounting portion 16 and 17, the load resistor R21 which is a means for setting the DC bias (direct current operating point) of the diodes D11 and D12, and the capacitor C22 which is a means for collecting and bypassing a part of the intermediate frequency signal. C23).

6 is a cross-sectional view of an exemplary circuit in which the bias method according to the present invention is applied to a rectangular waveguide hybrid balance mixer. As shown in FIG. 6, the mechanical structure of the waveguide is simpler than that of FIG. It has its own balanced diode direct current operating point.

Therefore, according to the bias circuit of the present invention, the mixing diode optimized by adjusting the DC operating point by itself without using an external power source or an inductor in the two mixing diodes D11 and D12 commonly connected by the resistor R21. DC operating point can be obtained, and it is additionally compensated for performance deterioration due to manufacturing or design error, and the number of parts is small and its structure is simple, which is advantageous for integrated circuit. It can be seen that it is applicable.

Claims (4)

Two input terminals for inputting a high frequency (RF) signal and a local oscillation frequency (L0) signal having a constant phase difference from each other, and receiving the high frequency signal and the local oscillation frequency signal to distribute the power of each signal and to adjust the phase In a balanced mixer having means (10 or 15), it is provided with two diodes (D11, D12) connected to two output terminals (Portl, Port2) of the phase adjusting means, respectively, for generating a DC power source having a different polarity. An intermediate frequency signal generating means for generating an intermediate frequency signal contained in the signals provided from the phase adjusting means, and a signal for collecting the intermediate frequency signal generated by the intermediate frequency signal generating means and outputting the collected signal; The intermediate frequency signal generating means and the number of signals to form a collecting means, and a single closed loop path of the DC power source. Including the load resistance means disposed between the collecting means, the single closed circuit path of the DC power source in turn is the input terminal of the high frequency, the phase adjusting means, the one diode (D11), the resistance means, the other And a diode (D12), the phase adjusting means and the input terminal of the local oscillation frequency signal. 2. A similarly active bias circuit according to claim 1, further comprising means (11, 12) for maintaining a DC operating ground point of said intermediate frequency signal generating means. 2. The similarly active bias circuit according to claim 1, further comprising means (C22, C23) for bypassing some intermediate frequency signals generated from said intermediate frequency generating means. 2. A pseudo-active bias circuit according to claim 1, wherein said phase control means is an ultra-high frequency integrated circuit hybrid (10).