JPH0720966Y2 - Microwave mixer - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention requires a direct current return path on the IF output side, and a microwave of a microstrip line configuration using a diode whose IF frequency band is higher than the UHF band. Regarding obi mixer.

[Prior Art] Conventionally, a microwave band mixer of this type uses a tip short-circuit stub having a microstrip line configuration in which the line length is equal to 1/4 wavelength of the center frequency of the intermediate frequency band as a DC return path, or Techniques such as using a choke coil to short-circuit to ground have been used. On the other hand, the first means for preventing the leakage of the local oscillation frequency to the signal output side is
For example, connect a low-pass filter to the output side of the mixer and use its high-frequency cutoff characteristic, or, secondly, use a mixer with a method that allows sufficient isolation to the IF side with respect to the local oscillation frequency. Means were taken.

[Problems to be Solved] However, in the above-mentioned conventional microwave band mixer, the first means has drawbacks of increased required space and increased cost, and the second means has a circuit configuration of the mixer. Due to the complexity, the design and development required a lot of time, and required space and the number of parts were increased.

[Means for Solving Problems] It is an object of the present invention to solve the above problems and provide a microwave band mixer having a downsized and simplified structure.

In order to achieve the above object, the microwave band mixer according to the present invention requires a DC return path on the signal output side, and the IF band is a microwave band of a microstrip line configuration using a diode whose frequency is higher than the UHF band. In the mixer, a tip short-circuit stub composed of a microstrip line having a high characteristic impedance is used as the DC return path, and the line table of the tip short-circuit stub is used to set the high-order anti-resonance frequency to the oscillation frequency of the local oscillator of the microwave band mixer. It was chosen to match the length.

[Embodiment] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 (a) is a block diagram showing a circuit configuration of a microwave band mixer when an embodiment of the present invention is applied to a frequency converter. In the figure, the output of the high frequency amplifier 1 is applied to the microwave band mixer 3 according to the present embodiment through the image blocking filter 2, and the output thereof is the local oscillator 4.
Is converted into an IF signal by and added to the IF amplifier 5.

FIG. 1 (b) is a diagram showing a frequency arrangement of the frequency conversion device. In the figure Is the low and high frequencies of the input signal to the frequency converter, Is the oscillation frequency of the local oscillator, Indicates the low frequency and high frequency of the IF frequency, respectively. Also, the values shown in the figure are used in the trial calculation described later.
Represents a frequency in GHz.

FIG. 1 (c) is a block diagram showing the circuit configuration of the microwave band mixer 3 of FIG. 1 (a), and 31, 33, 34 and 35 are
They are an input matching circuit, a local oscillation signal input circuit, an output matching circuit, and a DC return path short-circuit stub of the mixer diode 32, each of which has a microstrip line configuration, and are actually formed in a printed pattern on a dielectric substrate.

Here, the tip short-circuit stub of the microstrip line configuration shows resonance characteristics at a frequency where the line length is equal to an odd multiple of 1/4 wavelength, and conversely an even multiple of 1/4 wavelength (an integer of 1/2 wavelength). 2) shows an anti-resonance characteristic at a frequency that is equal to the above. In this embodiment, by utilizing this property, the line length of the tip short-circuited slab is equal to 1/4 wavelength in the vicinity of the IF frequency band in the IF frequency band, and its high-order anti-resonance frequency becomes the local oscillation frequency. They are selected so that they match, and the local radiation to the IF output side is suppressed.

FIG. 2 is a diagram showing the frequency characteristics of the pass loss of a single tip short-circuited stub having an ideal microstrip line configuration when the present embodiment is implemented for the frequency arrangement of FIG. 1 (b). In the example in the figure, the high-order anti-resonance frequency is the local frequency.
1.35 GHz is selected as a frequency that matches 10.8 GHz and is equivalent to 1/4 wavelength near the center frequency of the IF band (0.9 to 1.4 GHz). That is, suppression of local radiation is measured at the fourth anti-resonance frequency.

Next, FIG. 3 shows the reflection characteristics in the IF frequency band when the above-described trial calculation model is used. As can be seen from the figure, VSWR in the IF frequency band is suppressed to a relatively low value.

In the above calculation, the characteristic impedance of the tip short-circuit stub is selected to be 150Ω, and the loss of the printed board is not taken into consideration.

FIG. 4 is a diagram showing the relationship between the frequency equivalent to 1/4 wavelength of the tip short-circuited stub and the high-order anti-resonance frequency with the order (n) as a parameter.

[Effects of the Invention] As described above, the present invention uses a microstrip line configuration short-circuited stub as a DC return path on the IF output side of a mixer diode, and the line length is set to a high-order anti-resonance frequency of a local oscillator. By selecting a length that matches the oscillation frequency, a steep attenuation characteristic can be obtained with a simple configuration, which is effective in suppressing the local oscillation signal to the IF output side.
This is effective in simplifying and downsizing the circuit configuration of the mixer.

Also, when a low-pass filter is connected in the latter stage of the mixer for the purpose of suppressing local radiation, applying the present invention to the mixer makes it possible to reduce the attenuation characteristics of the filter, simplifying the filter and reducing the size of the filter. It is also effective for conversion.

[Brief description of drawings]

FIG. 1 (a) is a block diagram showing a circuit configuration of a microwave band mixer when an embodiment of the present invention is applied to a frequency conversion device, and FIG. 1 (b) shows a frequency arrangement of the frequency conversion device. FIG. 1 (c) is a block diagram showing the circuit configuration of the microwave band mixer of FIG. 1 (a), and FIG. 2 is the embodiment of the present invention for the frequency arrangement of FIG. 1 (b). FIG. 3 is a diagram showing a frequency characteristic of a passage loss of a tip short-circuited stub having an ideal microstrip line configuration in the case, FIG. 3 is a diagram showing a reflection characteristic in an IF frequency band when a trial calculation model according to the present embodiment is used, FIG. 4 is a diagram showing the relationship between the frequency equivalent to 1/4 wavelength of the tip short-circuit stub and the high-order anti-resonance frequency with the order (n) as a parameter. 1: High frequency amplifier 2: Image blocking filter 3: Microwave band mixer 4: Local oscillator 5: IF amplifier

Claims (1)

[Scope of utility model registration request] 1. A microwave band mixer having a microstrip line structure using a diode having a direct current return path on the signal output side and having an IF frequency band of a frequency higher than the UHF band, wherein the direct current return path has a characteristic impedance of A tip short-circuit stub composed of a high microstrip line is used, and a line table of the tip short-circuit stub is selected to have a length such that a high-order anti-resonance frequency matches the oscillation frequency of the local oscillator of the microwave band mixer. Microwave band mixer.