JPH0760973B2 - Mixer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention utilizes the non-linear characteristic of a Schottky diode to generate an intermediate frequency signal from a local oscillation signal and a high frequency signal, and separates the intermediate frequency signal from each other to generate an intermediate frequency signal. The present invention relates to a mixer for outputting a signal, particularly to a technique for reducing the power level of an unnecessary signal output to an intermediate frequency signal terminal.

[Conventional technology]

FIG. 7 is a diagram showing a schematic configuration of a conventional single-ended harmonic mixer shown in P130 to P132 of IEEE MTT-S Digest 1983. In the figure, 1 is a harmonic signal (hereinafter abbreviated as RF signal) terminal, 2 is a local oscillator signal (hereinafter abbreviated as L0 signal) terminal, 3 is an intermediate frequency signal (hereinafter abbreviated as IF signal) terminal, 4 is a Band pass filter for RF signal (hereinafter abbreviated as BPF for RF signal), 5a and 5b are Schottky diodes (hereinafter abbreviated as SBD), 6 is a low pass filter for RF signal element (hereinafter LPF for RF signal blocking) Is abbreviated), 7 is a high-pass filter for LO signals (hereinafter abbreviated as HPF for LO signals), 8 is a low-pass filter for IF signals (hereinafter abbreviated as LPF for IF signals),
Reference numeral 9 is a duplexer composed of HPF7 for LO signal and LPF8 for IF signal. FIG. 8 is a detailed circuit diagram of the IF signal LPF 8, which includes an inductor 10 and a capacitor 11.

Next, the mixer configured in this way is connected to the RF signal frequency, LO
The case of operating under the conditions of signal frequency and IF signal frequency will be described. First, RF is applied to the RF signal terminal 1 of the harmonic mixer.
Apply a signal (frequency frf) and at the same time LO signal terminal 2 to LO
When a signal (frequency flo) is applied, a signal having a frequency component fout of the following equation is generated at both ends of SBDs 5a and 5b.

fout = lm.flo ± n · frfl (m, n are integers, m ± n is an odd number) (1) Here, in order to efficiently extract the required IF signal frequency fif from a large number of frequency components fout , Each filter 4 ~
Set the frequency characteristic of 8.

Here, the role of each filter is explained. BPF4 for RF signal
Prevents signals other than LO signal, IF signal and RF signal from leaking to the RF signal terminal 1, and protects SBD5a, 5B
Acts as a matching circuit for RF signals. Also, LP for RF signal blocking
F6 prevents the RF signal from leaking to the LO signal terminal 2 and the IF signal terminal 3. In addition, the HPF7 for LO signal has the required IF signal.
Prevents leakage to the LO signal terminal 2 as well as SBD5a, 5b
Acts as a matching circuit for the LO signal to. Further, the LO signal for IF signal 8 prevents the LO signal from leaking to the IF signal terminal 3 and also functions as a matching circuit for the IF signal for the SBDs 5a and 5b. As shown in FIG. 8, generally, the circuit configuration of the LPF 8 for IF signal is such that a series inductor 11 and a parallel capacitor 10 are provided.
And has a monotonous damping characteristic.

With such a configuration and operation, a desired IF signal can be taken out to the IF signal terminal 3 in the harmonic mixer.

[Problems to be Solved by the Invention]

By the way, in the above harmonic mixer, the LO signal frequency flo and the IF signal frequency fif may be close to each other. In the conventional mixer, the frequency characteristic of the LPF8 for IF signal is monotonous, so the isolation between the LO signal terminal 2 and the IF signal terminal 3 is not sufficient, and the LO signal becomes the IF signal terminal 3
There was a problem that was leaked to. Further, if the LPF8 for IF signal is multi-staged to enhance the isolation, there is a problem that the shape becomes large. Further, of the unnecessary spurious signals (frequency fout) output at the same time as the required IF signal, there is a problem that the spurious signal (referred to as frequency fsp) close to the IF signal cannot be sufficiently removed.

The present invention has been made to solve the above problems, and in a harmonic type mixer, it is possible to reduce the power level of the LO signal and the spurious signal leaking to the IF signal terminal with a simple configuration. The purpose is to provide a mixer.

[Means for Solving the Problems]

The mixer according to the present invention is a harmonic type mixer, wherein at least one resonance circuit (12a, 12b, or 13a, 13b) which resonates at a local oscillator signal and a spurious signal frequency is provided between the input / output terminals of the IF signal LPF (8). ) Is provided.

[Action]

In the mixer according to the present invention, when the resonance frequency of the resonance circuit (12a, 12b, or 13a, 13b) provided in the IF signal LPF (8) is set to the LO signal frequency flo or the spurious signal frequency fsp, SBD (5a, 5b ) To the IF signal terminal, a blocking characteristic occurs, and this blocking characteristic reduces the output power level of the LO signal and unnecessary signal leaking to the IF signal terminal (3).

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of the present invention.
The same parts as those in the figure are designated by the same reference numerals, and the description thereof will be omitted.
In Fig. 1, the difference from the conventional one is that the LPF8 for IF signal is
The configuration is as shown in the figure. That is, in FIG. 2, 10a and 10b are inductors, 11a, 11b, 11c and 11d are capacitors, 12a is a first parallel resonant circuit including an inductor 10a and a capacitor 11a, and 12b is an inductor 1.
This is a second parallel resonance circuit composed of 0b and a capacitor 11b. Since these parallel resonant circuits 12a and 12b are connected in series between the input and output terminals of the IF signal LPF8, they have blocking characteristics at their resonant frequencies.

FIG. 3 is a diagram showing an example of the characteristics of the IF signal LPF 8 in this embodiment. Spurious signal frequency fsp and local signal frequency flo, respectively, for the resonant frequencies of the parallel strong circuits 12a and 12b.
When set to, the characteristic indicated by the solid line A is obtained. Comparing this characteristic with the characteristic of the conventional configuration shown by the solid line B, fSP and flo
A large insertion loss can be obtained at the frequency of.

FIG. 4 shows an example of a spectrum diagram showing the power level of the signal output to the IF signal terminal 3, and FIG. 4A shows the case where the IF signal LPF8 having the conventional configuration is used.
(B) is a spectrum diagram when the LPF8 for IF signals according to the present invention is used. As is clear from FIGS. 4 (a) and 4 (b), the power levels of the LO signal of frequency flo and the unnecessary spurious signal of frequency fsp leaking to the IF signal terminal 3 are not attenuated without attenuating the required IF signal. It can be seen that it can be reduced.

FIG. 5 is a circuit diagram showing another embodiment of the mixer according to the present invention, which is a detailed diagram of the IF signal LPF8. In FIG. 5, 13a is a first series resonant circuit including a capacitor 11a and an inductor 10a, and 13b is a second series resonant circuit including a capacitor 11b and an inductor 10b. These series resonance circuits 13a and 13b are connected in parallel between the input and output terminals of the LPF 8 for IF signal, and have the same blocking characteristics as the embodiment of FIG. 2 at the resonance frequency. Therefore, the same effect as that of the first embodiment shown in FIG. 2 is obtained.

FIG. 6 shows still another embodiment of the mixer according to the present invention, which is a detailed view of the IF signal LF8. In this embodiment, between the input / output terminals of the IF signal LPF,
Parallel co-advance circuit consisting of capacitor 11a and inductor 10a
Since 12 is connected in series and the series resonant circuit 13 including the capacitor 11b and the inductor 10b is connected in parallel, the blocking characteristic is provided at each resonant frequency. Therefore,
By setting each resonance frequency in the same manner as in the circuit shown in FIG. 2, the same effect as that of the embodiment shown in FIG. 2 can be obtained.

In the above embodiment, two stop frequencies flo and fsp are provided, but this is an arbitrary number, and the resonance circuit may be provided according to the required stop frequency.

Further, in the above embodiment, the high frequency mixer using the reverse polarity Schottky diodes connected in parallel has been described, but a single end mixer, a balanced mixer or a double balanced mixer using a single Schottky diode may be used. Well, it has the same effect.

〔The invention's effect〕

As described above, according to the present invention, in the harmonic type mixer, at least one resonance circuit that resonates at the frequencies of the local oscillation signal and the spurious signal is provided in the IF signal LPF. The power levels of the outgoing signal and the unwanted signal can be reduced with a simple configuration.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a mixer according to an embodiment of the present invention, FIG. 2 is a detailed configuration diagram of an IF signal LPF, and FIG. 3 is a characteristic diagram showing insertion loss of the IF signal LPF according to the present invention. FIG. 6 is a spectrum diagram showing the power level of the signal output to the IF signal terminal of the mixer according to the present invention, FIG. 5 is a diagram showing the configuration of the mixer according to another embodiment of the present invention, and FIG. 6 is the present invention. FIG. 7 is a diagram showing a configuration of a mixer according to still another embodiment, FIG. 7 is a diagram showing a configuration of a conventional mixer, and FIG. 8 is a detailed configuration diagram of an IF signal LPF of the conventional mixer. 1 ... RF signal terminal, 2 ... LO signal terminal, 3 ... IF signal terminal, 5a, 5b ... Schottky diode, 8 ... IF signal LPF, 12a, 12b ... Parallel resonant circuit, 13a, 13b …… Series resonance circuit. In the drawings, the same symbols indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A harmonic type which comprises a plurality of filter circuits for respectively separating a local oscillator signal, a high frequency signal and an intermediate frequency signal and a diode, and which outputs a mixed wave of a high frequency signal and a harmonic of the local oscillator signal. In the mixer, at least one resonance circuit that resonates at a local oscillation signal frequency or a spurious signal frequency is connected between an input terminal and an output terminal of a low-pass filter circuit that extracts an intermediate frequency signal of the filter circuit. Characteristic mixer.