JPS6238884B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mixer used for signal processing in a repeater or the like in wireless communication, and in particular, to a mixer used for signal processing in a repeater or the like in wireless communication, and in particular, to a mixer in which harmonics generated in the mixer flow into a signal processing system connected to the mixer. This invention relates to a mixer that prevents harmful effects.

In wireless communication, a high frequency signal from a transmitting side is converted into an intermediate frequency signal on a receiving side for signal processing, and it is well known that a mixer is used for frequency conversion. FIG. 1 is a diagram showing the configuration of a conventional mixer, in which 1 is a signal input terminal, 2 is a local oscillator, 3 is a hybrid circuit, 4 and 5 are mixer diodes connected in antiparallel, and 6 and 7 are low frequency A pass-through device (hereinafter simply referred to as a filter) 8 is an output terminal of the mixer, and is connected to a signal processing system, such as a preamplifier. If the frequency of the input signal applied to the signal input terminal 1 is f ₁ .The oscillation frequency of the local oscillator 2 is f ₂ , then the output terminal 8 has the following equation as well known: f ₃ = |f ₁ − _{f 2}
A signal with a frequency of ｜ appears. The filters 6 and 7 are used to remove harmonic components generated in the mixer diodes 4 and 5, and prevent the harmonics from being output. However, the harmonics are reflected by the filter section and are used as input signals and It is mixed with the signal from the local oscillator and output from the mixer as a signal having a frequency near the frequency _f3 of the output signal.
For this reason, the frequency characteristics and phase characteristics of the mixer are not flat, and there are convex portions in some parts, resulting in poor playback quality.
The problem was that the playback quality deteriorated.

The present invention was made in view of the above points, and an object of the present invention is to remove harmonic components generated in a mixer using a harmonic blocking filter and a harmonic absorber.

Preferred embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a diagram showing the configuration of an embodiment of the mixer according to the present invention. Parts equivalent to those in FIG. 1 are given the same symbols. In this embodiment, the hybrid circuit 3
An open stub 9 having a wavelength of 1/4 of the harmonic wave is provided between the hybrid circuit 3 and the mixer diode 4 as a harmonic blocking filter. An open stub 10 of the same configuration, ie, a length of 1/4 of the harmonic wavelength, is provided. 11 and 12 are band rejection filters (hereinafter simply referred to as filters), which remove the input signal of frequency f ₁ and the signal from the local oscillator of frequency f ₂ ;
It has a passband for intermediate frequency signals of frequency f ₃ and harmonics. 13 and 14 are microwave absorbers that absorb harmonic components.

Next, the operation of this mixer will be explained. As mentioned above, the input signal of frequency f ₁ and the signal from the local oscillator of frequency f ₂ are mixed and harmonics are generated from the mixer diodes 4 and 5, but the harmonics propagating to the hybrid circuit 3 side is reflected by the open stubs 9,10. Therefore, the harmonics generated by the mixer diodes 4 and 55 are not input to the hybrid circuit 3, but are input to the filters 11 and 12.
It passes through and is absorbed by the microwave absorbers 13 and 14. Therefore, no harmonic signal appears at the output terminal 8, and since the harmonics are blocked by the open stubs 9 and 10 and do not enter the hybrid circuit 3, an intermediate signal is generated by mixing with the input signal and the signal from the local oscillator. No frequency signal is generated.

The above-mentioned open stub and microwave absorber are well known, and the open stub has a structure as shown in FIGS. 3a and 3b, for example. Figure a is a top view of the open stub, Figure b is Figure 3A.
FIG. 2 is a sectional view taken along cutting line A-A'. S denotes an insulating substrate, and L denotes a signal transmission line, both ends of which are connected to a hybrid circuit 3 and a diode mixer 4, respectively. 9 is an open stub whose line length l is 1/1 of the harmonic wavelength as mentioned above.
It is 4. E is a ground wire provided on the surface of the substrate S on the opposite side from the open stub 9 and the signal transmission line L.

Furthermore, the above-mentioned microwave absorber is made of carbonyl iron hardened with epoxy resin, and is shown in Fig. 4a,
It is placed on the signal transmission line as shown in b. Fourth
Figure a is a top view, and figure b is a section line B- in Figure 4 a.
A cross-sectional view along B′ is shown. Parts equivalent to those in Fig. 3 are given the same reference numerals. In FIG. 4a, a diode mixer 4 and an output terminal 8 are provided at both ends of the transmission line L, respectively. K is the microwave absorber mentioned above, and is placed on the signal transmission line L.

In the above embodiment, only one pair of open stubs was provided, but two pairs may be provided depending on the wavelength of the generated harmonic signal.
More than one pair may be provided.

As is clear from the above explanation, the mixer according to the present invention absorbs and removes harmonic signals generated by non-linear elements such as diode mixers, so its frequency characteristics and phase characteristics become flat, which is useful in wireless communication, etc. Extremely useful for signal processing.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a conventional mixer, FIG. 2 is a configuration diagram of an embodiment of the mixer according to the present invention, FIGS. 3 a and b are diagrams showing the configuration of an open stub, and FIGS. 4 a and b FIG. 2 is a diagram showing a state in which a microwave absorber is placed. 1: Signal input terminal, 2: Local oscillator, 3: Hybrid circuit, 4, 5: Mixer diode, 6,
7: Low pass filter, 8: Output terminal, 9,1
0: Open stub, 11, 12: Band removal filter, 13, 14: Microwave absorber, S: Substrate, L: Signal transmission line, K: Microwave absorber.

Claims (1)

[Claims] 1. A hybrid circuit which inputs a high frequency input signal and a signal from a local oscillator, and a non-linear element connected to an output terminal of the hybrid circuit, converts the high frequency input signal into an intermediate frequency signal. In the mixer for converting the hybrid circuit into A band elimination filter is provided on the output side of the band elimination filter to pass intermediate frequency signals and harmonics and remove the input signal and signals from the local oscillator, and a microwave absorber is provided on the output side of the band elimination filter to absorb harmonics and remove the A mixer characterized in that harmonic signals are prevented from being output.