JPH0336323B2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Technical Field of the Invention The present invention relates to a reflective frequency converter, and in particular to a reflection type frequency converter that mixes a high frequency carrier signal and a predetermined intermediate frequency IF signal to generate a modulated radio transmission signal. Regarding the so-called up converter.

(2) Prior art and problems Figure 1 shows the configuration of a conventional general reflection type frequency converter. Here, the carrier signal input terminal
The high frequency signal of frequency ₀ input from In is passed through a circulator and a band pass filter BPF ₁ whose pass band is set to a predetermined high frequency band.
It is input to varactor diode D. on the other hand,
A signal of frequency ₁ inputted from the IF signal input terminal IF•In is inputted to the varactor diode D via the bandpass filter _BPF2 . The modulated wave signal having a frequency of { ₀ ± ₁ } generated by mixing the two input signals is taken out from the modulated wave output terminal Out via the filter BPF ₁ and the circulator again. Thereafter, the signal is passed through a narrow band pass filter (not shown) to obtain only a predetermined transmission signal.

When attempting to form the circuit shown in FIG. 1 using a MIC circuit, it is difficult to manufacture a good bandpass filter using a microstrip line, so the configuration shown in FIG. 2 is obtained.

In Figure 2, C is a DC component blocking capacitor, 1
0 is an impedance conversion element, and LPF is a low-pass filter formed by a microstrip circuit. That is, BPF ₁ of FIG. 1 is realized by the impedance conversion element 10, and BPF ₂ is realized by the filter LPF.

Here, since the IF signal output terminal IF・In needs to be separated from the diode D in terms of high frequency, a filter LPF is provided.
Since the termination conditions of the LPF are generally considered only within the IF signal band, the impedance on the filter LPF side seen from the diode D side cannot necessarily be said to be good.

Therefore, with the above-mentioned conventional frequency converter, when the input conditions at the IF signal input terminal are changed, the surrounding conditions of the diode change, causing problems such as fluctuations in conversion efficiency or oscillation of the circuit. It was hot.

(3) Purpose of the Invention The present invention has been made in view of the problems of the prior art described above, and an object of the present invention is to provide a frequency converter that can operate stably.

(4) Structure of the Invention The object of the present invention is to provide a reflection frequency converter that mixes a carrier wave signal input through a circulator with a predetermined intermediate frequency signal using a diode, and outputs it as a modulated wave through the same circulator again. The input of the intermediate frequency signal is superimposed on a forward bias and is passed through a low-pass filter that matches the intermediate frequency signal, and the intermediate frequency signal input terminal of the low-pass filter is connected to a carrier frequency signal. This is achieved by connecting open type terminators.

(5) Embodiments of the invention Examples of the invention will be described below with reference to the drawings.

FIG. 3 is a diagram for explaining the basic operation of the present invention. In the figure, reference numeral 11 is an open type terminator (dummy), and other components are the same as those in FIG. 2.

Here, in order to improve the termination conditions of the filter LPF, an open type dummy 11 that can be used in a high frequency band is connected to the IF signal input terminal of the filter LPF. This design also satisfies the termination conditions in the high frequency band. Further, the IF signal is input to the filter LPF through the input end of this open type dummy 11, and drives the diode D.

Normally, as an IF signal, a frequency of several tenths to several hundredths of the modulated wave signal frequency is used.
After adding open type dummy 11, IF
It only has an effect on the signal to the extent that a small susceptance is added.

Furthermore, in the present invention, by superimposing and inputting a DC bias on the IF signal, the operating point can be forcibly determined, and the operation can be kept even more stable.

FIG. 4 shows an embodiment of the present invention. In the figure, L is a chiyoke coil and VR is a variable resistor, which constitutes a DC bias input circuit.

Here, it is necessary to select a value for the DC bias that will keep the modulated wave output stable. Figure 5 is a diagram showing the relationship between diode drive current and modulated wave output.As is clear from the figure, stable operation is generally possible in the forward bias region;
Conversion efficiency as a frequency converter decreases. On the contrary, in the reverse bias region, although high conversion efficiency can be obtained, the characteristics are not stable. still,
The output characteristics of the modulated wave due to the diode drive current vary slightly depending on the selection of the diode itself, matching circuit conditions, etc.

Therefore, although it sacrifices some conversion efficiency, it is most preferable from the viewpoint of circuit operation to place emphasis on operational stability and to superimpose a low forward bias shown at point a in the figure to drive the diode. It is.

(6) Effects of the Invention As described above, according to the present invention, the impedance characteristic of the filter LPF viewed from the diode D side can be made good even in a high frequency band, and stable frequency conversion operation can be performed. Also,
It is possible to relax the input conditions of the IF signal, making it easier to manufacture the circuit.

[Brief explanation of drawings]

Figure 1 shows the basic configuration of a conventional reflective frequency converter, Figure 2 shows a conventional reflective frequency converter realized using a MIC circuit, Figure 3 explains the basic operation of the present invention, and Figure 4 shows the basic configuration of a conventional reflective frequency converter. 5 shows an embodiment of the present invention, and FIG. 5 shows the relationship between diode drive current and modulated wave output. In the figure, BPF ₁ and BPF ₂ are band pass filters, D
is a paractor diode, C is a DC component blocking capacitor, 10 is an impedance conversion element,
LPF is a low-pass filter, 11 is an open terminator, L is a chiyoke coil, and VR is a variable resistor.

Claims (1)

[Scope of Claims] 1. In a reflection frequency converter that mixes a carrier wave signal inputted through a circulator with a predetermined intermediate frequency signal using a diode and outputs it as a modulated wave through the same circulator, the intermediate frequency A signal is input through a low-pass filter that superimposes a forward bias and matches the intermediate frequency signal, and an open terminator for the carrier frequency is connected to the intermediate frequency signal input terminal of the low-pass filter. A reflection type frequency converter characterized in that: 2. The carrier wave signal and the intermediate frequency signal are mixed using a diode, and the input of the intermediate frequency signal is superimposed on a forward bias voltage. Reflective frequency converter.