JPS6324649Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an image recovery type MIC frequency converter with improved conversion loss and circuit configuration.

FIG. 1 is a circuit diagram of a conventional image recovery type frequency converter. The signal frequency enters the bandpass filter (BPF ₁ ) 1 from the waveguide 8 via the waveguide-MIC converter 7, and the bandpass filter 1 removes unnecessary waves. On the other hand, the local oscillation frequency also passes through the band pass filter (BPF ₂ ) 2, and unnecessary waves are similarly removed. Each frequency passes through transmission lines 5 and 6 each having a fixed electrical length, is mixed at a diode 3, and is converted into an intermediate frequency (F _IF ). A low pass filter (LPF) 4 reflects the signal frequency and the local frequency and passes the intermediate frequency, so that only the intermediate frequency is extracted from the output terminal. When the low-pass filter is viewed from point P in the figure, its impedance is open to the signal frequency and local oscillation frequency, and matched to the intermediate frequency. Therefore, so that the impedance when looking at bandpass filter 1 from point P is open to the local oscillation frequency (F _LO ), the impedance when looking at bandpass filter 2 from point P is Matching can be easily achieved by selecting the electrical lengths of the transmission lines 5 and 6 so that the impedance is also open to the signal frequency ( _FS ), and terminating the local oscillator input and signal input with the diode 3. . In a conventional frequency converter, the bandpass filter is configured by an MIC, and the transmission line has a small Q ₀ and therefore has a large passing loss.
Therefore, it had the disadvantage of large conversion loss.

The present invention was developed based on the above considerations. The purpose of this is to use the cutoff characteristics of the waveguide provided on the signal frequency side to eliminate the signal frequency bandpass filter, thereby obtaining low conversion loss characteristics and simplifying the circuit configuration. The objective is to provide a frequency converter that can

In order to achieve the above object, the image recovery type MIC frequency converter according to the present invention comprises: a signal frequency transmission waveguide; the waveguide-MIC converter;
a first transmission line with a constant electrical length connected to the waveguide-MIC converter; a bandpass filter having a local frequency smaller than the signal frequency; and a first transmission line connected to the bandpass filter. a second transmission line with a constant electrical length; a diode that generates an intermediate frequency by mixing a signal frequency from the first transmission line and a local frequency from the second transmission line; and a diode that generates an intermediate frequency, and extracts the intermediate frequency. The cutoff frequency of the waveguide section is selected such that the relationship of local oscillation frequency<cutoff frequency<signal frequency is satisfied.

According to the above configuration, the conversion loss is reduced and the circuit itself is simplified, so that the object of the present invention is completely achieved.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

Figure 2 shows the image recovery type according to this invention.
1 is a circuit block diagram showing an embodiment of a MIC frequency converter. FIG. In the figure, the circuit parts labeled with the same reference numerals as those used for each part in FIG.
It has the same configuration as the circuit section shown in the figure. The signal frequency bandpass filter (BPF ₁ ) shown in FIG. 1 has been removed. The impedance when looking at the low-pass filter 4 from point P is open to the signal frequency (F _SIG ) and local frequency (F _LO ), and matched to the intermediate frequency (F _IF ). Also, from point P (BPF ₂ )
The electrical length of the transmission line 6 is selected so that the impedance shown in the figure is open to the signal frequency, and the signal input is terminated with a diode for matching. In the waveguide-MIC section loaded on the signal frequency side, set the waveguide cutoff frequency (F _C ) to F _LO < F _C
The local oscillation frequency is reflected by selecting the relationship <F _SIG . However, as is clear from the above conditions, the signal frequency is greater than the cutoff frequency, so it is transmitted within the waveguide without any influence. Therefore, if the electrical length of the transmission line 5 is selected so that the impedance viewed from point P to the waveguide-MIC converter is open to the local frequency, the local input can be terminated with a diode, making it easy to can be matched. Also, the image frequency (F _IM = 2F _LO −F _SIG )
As for the component, F _IM < _FC and it is reflected by the waveguide, so it can be opened or shorted as seen from the diode. Therefore, if the F _IM is set to the above conditions, the F _IM component is reconverted by the diode, and good conversion loss frequency characteristics can be obtained.

FIG. 4 shows an example of the arrangement of these frequencies.

The frequency converter according to the present invention achieves the same operation as conventional band-pass filters by utilizing the blocking characteristics of the waveguide to reflect the local frequency, so there is no need for a band-pass filter. becomes. Therefore, the circuit configuration is simplified, and since the passing loss of the filter is not included in the conversion loss of the frequency converter, there is an advantage that the conversion loss characteristics can be reliably reduced.

FIG. 3 shows the embodiment of FIG. 2 on a MIC board. The bandpass filter 2 (BPF ₂ ) is realized by a parallel couple line, and the BPF ₂
The impedance viewed from above is open to the signal frequency, or the impedance viewed from point P to the waveguide-MIC converter is open to the local frequency and open or short-circuited to the image frequency. On the other hand, the impedance when looking at the low-pass filter from point P is open to the signal frequency and local frequency and matched to the intermediate frequency, so that only the intermediate frequency appears at the intermediate frequency terminal.

As explained in detail above, the frequency converter according to the present invention avoids reflection of the local frequency and image frequency by the cutoff characteristics of the waveguide provided on the signal frequency side, and appropriately selects the electrical length from the diode to the reflection point. This allows effective matching for each frequency component. Therefore, the conversion loss does not include the passing loss of the bandpass filter, and the conversion loss frequency characteristics of the frequency converter are significantly improved.

Although the reception frequency converter has been described above as an example, similar effects can be obtained by operating this as a transmission frequency converter.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional image recovery type frequency converter, and Figure 2 is a circuit diagram of a conventional image recovery type frequency converter.
The circuit diagram of the recovery type frequency converter, Figure 3 is the 2nd one.
FIG. 4 is a diagram showing a specific circuit for realizing the diagram, and FIG. 4 is a diagram showing the frequency arrangement of the frequency converter. 1... Signal band pass filter, 2... Local band pass filter, 3... Diode, 4... Low pass filter, 5, 6... Transmission line having a certain electrical length,
7...Waveguide-MIC conversion section, 8...Waveguide, 9
...MIC board.

Claims (1)

[Scope of utility model registration request] A waveguide for signal frequency transmission, and the waveguide
a MIC converter, a first transmission line of a constant electrical length connected to the waveguide-MIC converter, a bandpass filter with a local frequency smaller than the signal frequency, and the bandpass filter. a second transmission line of a constant electrical length connected to the device; a diode that generates an intermediate frequency by mixing the signal frequency from the first transmission line and the local frequency from the second transmission line; and a low-pass filter for extracting the intermediate frequency, and the cutoff frequency of the waveguide section is selected such that the relationship of local frequency<cutoff frequency<signal frequency is satisfied.・Recovery type MIC frequency converter.