JP2000236221A - Mixer circuit and its mixing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To actualize the mixer circuit and its mixing method which satisfactorily modulate an RF signal of the microwave band. SOLUTION: This mixer circuit is equipped with two single-balanced mixers, having nearly the same frequency conversion characteristics. In this case, one SBM1(single-balanced mixer) (4) modulates an RF signal according to a positive- phase modulating signal and the other SBM2 modulates the RF signal, which is delayed by a half wave through a λ/2 delay circuit 3, according to a modulating signal which is inverted in phase by a balun 2. The modulating signal outputted from the SBM1 and SBM2 (5) are mixed by a mixer 6, so that the leakage components of the RF signals included in the modulated signals cancel each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mixer circuit and a method of mixing the same, for example, to a mixer circuit for converting microwave band radio waves into a desired intermediate frequency signal and a method of mixing the same.

[0002]

2. Description of the Related Art Conventionally, in a transceiver for wireless communication, a mixer circuit for mixing an RF (radio frequency) signal and a modulation signal in order to generate an intermediate frequency signal which can be easily handled in a subsequent circuit. Frequency conversion circuit).

[0003] Such a mixer circuit includes a so-called single mixer and a single balanced mixer (hereinafter, referred to as SB).
M), and a double balanced mixer (hereinafter, DBM)
Is generally used, and among them, a balanced mixer capable of efficiently reducing the leakage of the modulation signal to the output side with a simple circuit configuration is widely used.

[0004]

In recent years, there has been an increasing demand for high-speed mobile wireless communication, that is, wireless communication capable of transmitting and receiving more information in a short time. In order to respond to such a demand, the above-mentioned conventional general balanced mixer uses, for example, 5.8 GHz.
When an RF signal in a microwave band such as the z band is converted using a wideband modulation signal of about several tens of MHz to about 1 GHz,
At the output stage of the mixer circuit, not only the desired intermediate frequency signal does not appear, but also the generation of unnecessary radiation waves and the leakage of the modulation signal appear remarkably, and a mixed output that faithfully represents the waveform of the original RF signal is provided. Difficult to obtain.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a mixer circuit for performing good modulation on an RF signal in a microwave band and a mixing method thereof.

[0006]

In order to achieve the above object, a mixer circuit according to the present invention has the following configuration.

That is, a mixer circuit for mixing an RF signal and a modulation signal, comprising a divider for splitting an RF signal into two RF signals, and an RF output from the divider.
Two single balances having substantially the same frequency conversion characteristics, a delay circuit that delays the signal by a half wavelength, a balun that outputs the modulated signal in the opposite phase while outputting the modulated signal in the opposite phase, and outputs the inverted modulated signal. A first mixer for modulating an RF signal supplied from the divider according to a positive-phase modulation signal supplied from the balun; and a half-wave delayed RF signal supplied from the delay circuit. By mixing a second mixer that modulates the signals according to opposite-phase modulation signals supplied from the balun, and modulation signals output from the first and second mixers, respectively. And a mixer for canceling a leakage component caused by the RF signal.

Alternatively, in order to achieve the above object, a mixing method of a mixer circuit according to the present invention has the following configuration.

That is, a method of mixing an RF signal and a modulation signal in a mixer circuit, wherein two single balanced mixers having substantially the same frequency conversion characteristics are prepared,
The first mixer, which is the single balanced mixer,
An RF signal is modulated according to a positive-phase modulation signal, and the second mixer, which is the single-balanced mixer, modulates the RF signal delayed by a half wavelength according to the modulation signal inverted to an opposite phase, and And the modulated signals output from the second mixers are mixed by a mixer, whereby the modulated signals are
It is characterized in that a leakage component caused by the RF signal is canceled.

In the above mixer circuit and its mixing method, for example, the RF signal is a microwave in a band of about 5.8 GHz, and the modulation signal is
It is suitable to be adopted when changing in the GHz range.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example of a mixer circuit according to the present invention will be described.
An embodiment in which conversion is performed using a wideband modulated signal from 0 MHz (about 20 MHz) to about 1 GHz will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a circuit configuration of a mixer circuit according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a general divider (divider) for dividing an RF signal in a 5.8 GHz band into two.
It is. One of the signals split by the divider 1 is
The other signal is input to the SBM 1 and the other signal is input to the λ / 2 delay circuit 3. The λ / 2 delay circuit 3 is a general delay circuit that inverts the phase of an input signal to delay the output of the signal by a half wavelength.

2 is a balun that outputs a wide-band modulated signal of about several tens of MHz to about 1 GHz to the SBM 1 while maintaining the same phase with respect to the SBM 1, and outputs an inverted phase signal of the modulated signal to the SBM 2. (balun: balanced / unbalanced circuit).

SBM1 and SBM2 are single-balanced mixers having a so-called rat race configuration.
B is also a general one that does not include an output port isolation mechanism with respect to an input port, and has substantially the same frequency conversion characteristics. The SBM 1 modulates an RF signal input from the divider 1 according to a positive-phase modulation signal input from the balun 2, and inputs the modulated signal to the mixer 6. The SBM 2 modulates the delayed RF signal input from the λ / 2 delay circuit 3 in accordance with the opposite-phase modulation signal input from the balun 2, and modulates the modulated signal into a mixer 6.
To enter.

Reference numeral 6 denotes a mixer (combiner) for mixing the signals output from the SBM 1 and SBM 2 respectively. A desired intermediate frequency signal is output as a mixed output from an output port (not shown) of the mixer 6. You.

In an actual mixer circuit, each block described above and a wiring pattern (copper foil) connecting the blocks are mounted in a multilayer structure with the best arrangement and length experimentally and empirically obtained. It is arranged on the substrate.

FIG. 2 is a diagram showing signal waveforms at various parts of the mixer circuit according to one embodiment of the present invention.

As shown in FIG. 1, the RF signal input to the mixer circuit shown in FIG.
It is a pulse signal that can take a wide frequency range from about Hz to 1 GHz. In addition, SBM1 and SBM2 include:
Since a general single-balanced mixer that does not include an isolation mechanism is used, the modulated signal output from those mixers leaks the modulated signal, and the reference level of the signal is affected by the leak component. Is SBM1
It can be seen that there is a shift to the + side and to the-side in SBM2. However, in the present embodiment, as described above, SBM1 and SBM2 have substantially the same frequency conversion characteristics, and the modulation signal output from SBM2 is half the modulation signal output from SBM1. Since the signals have the opposite phases delayed by the wavelength, the modulated signals having the normal phase and the opposite phase are mixed by the mixer 6, so that the leakage components included in the modulated signals are cancelled. For this reason,
From an output port (not shown) of the mixer 6, as shown in FIG. 2, an RF signal input to the divider 1 is output as a faithful waveform converted (modulated) by a modulation signal input to the balun 2. Can be.

FIG. 3 is a diagram showing the characteristics of the modulation frequency and the isolation by the mixer circuit according to one embodiment of the present invention, wherein the carrier wave of the RF signal is 0 dBm / 5.
Under the conditions of 888 GHz and the level of the modulated wave of +6 dBm, the mounting conditions on the substrate are slightly different.
It shows the isolation characteristic with respect to the modulation frequency measured for three samples (samples A, B, and C), that is, the degree of reduction of the leakage of the modulation signal in the output stage.

When a general SBM is used alone, the isolation characteristic with respect to the modulation frequency is approximately −15.
dB to about −25 dB, whereas the mixer circuit samples A, B, and
C shows good isolation characteristics over a wide band from about 5 MHz to about 1 GHz, as shown in FIG.
It realizes −40 dB over about z, and has a better isolation characteristic of about −28 dB than the case where a general SBM is used alone even in a frequency range around 500 MHz where the isolation characteristic is the lowest. It turns out that there is.

FIG. 4 is a diagram showing the signal characteristics of the lower first sideband with respect to the carrier input to the mixer circuit according to the embodiment of the present invention, wherein the carrier wave of the RF signal is 5.88.
The measurement was performed for the lower first sideband under the conditions of 8 GHz and a modulated wave of +6 dB / 150 MHz (the upper first sideband has almost the same isolation as the characteristics of the lower first sideband). The description is omitted because it is a characteristic).

As is clear from FIG. 2, the mixer circuit according to the present embodiment has a linear first-order lower sideband with respect to the input of the carrier wave (here, +5 dBm).
The dashed lines in the vicinity are due to the characteristics of the standard signal generator used to create the carrier signal in the experiment), which means that the mixed output signal generated by such a circuit can be easily handled in subsequent circuits. ing.

In the above-described embodiment, 5.
Although the description has been made assuming an RF signal in an 8 GHz band, the present invention is not limited to this band, and the circuit configuration of the mixer circuit in FIG. 1 according to the present embodiment is applicable to an RF signal in another band such as a 2.4 GHz band. It is also applicable, and in this case, the arrangement and the length and arrangement of the wiring patterns for connecting the blocks of the mixer circuit on the mounting substrate and connecting the blocks,
What is necessary is just to design beforehand so that the modulation signal does not leak to the mixed output from the circuit.

In this embodiment, the case where the RF signal in the microwave band is modulated by the configuration of the mixer circuit shown in FIG. 1 has been described. However, the mixer circuit may be used for the demodulation circuit.

[0026]

As described above, according to the present invention,
It is possible to provide a mixer circuit that performs good modulation on an RF signal in a microwave band and a mixing method thereof. If such a mixer circuit is employed in a mobile radio communication system, more information can be transmitted and received accurately in a short time.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a circuit configuration of a mixer circuit according to an embodiment of the present invention.

FIG. 2 is a diagram showing signal waveforms at various parts of a mixer circuit according to one embodiment of the present invention.

FIG. 3 is a diagram illustrating characteristics of a modulation frequency and isolation by a mixer circuit according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating signal characteristics of a lower first sideband with respect to a carrier input to a mixer circuit according to an embodiment of the present invention.

[Explanation of symbols]

 1: Divider, 2: Balun, 3: λ / 2 delay circuit, 4: Single balanced mixer (SBM) 1, 5: Single balanced mixer (SBM) 2, 6: Mixer,

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaaki Toyama 1-2-23 Kiyosumi, Koto-ku, Tokyo Inside the Research Unit of Pacific Cement Co., Ltd. (72) Inventor Kama ▲ hachi ▼ Hiromichi 2-chome, Kitashinjuku, Shinjuku-ku, Tokyo No. 1-16 Hertz Engineering Co., Ltd.

Claims (5)

[Claims] 1. A mixer circuit for mixing an RF signal and a modulation signal, comprising: a divider for splitting the RF signal into two RF signals; and a delay circuit for delaying the RF signal output from the divider by a half wavelength. A balun that outputs the modulated signal as it is in the normal phase, inverts the signal to the opposite phase, and outputs the inverted modulated signal, and two single-balanced mixers having substantially the same frequency conversion characteristics; A first mixer that modulates the supplied RF signal according to a positive-phase modulation signal supplied from the balun; and a half-wave delayed RF signal supplied from the delay circuit, and a reverse mixer supplied from the balun. A second mixer that modulates according to a phase modulation signal; and a modulation signal that is output from each of the first and second mixers. Mixer circuit, characterized in that it comprises at which are contained in the modulated signal, and a mixer for canceling the leakage component due to the RF signal. 2. The mixer circuit according to claim 1, wherein said RF signal is a microwave in a band of about 5.8 GHz. 3. The modulation signal has a frequency of approximately 20 MHz to 1 G
2. A frequency range of 1 Hz.
The mixer circuit as described. 4. A method for mixing an RF signal and a modulation signal in a mixer circuit, wherein two single-balanced mixers having substantially the same frequency conversion characteristics are prepared, and the first mixer as the single-balanced mixer is provided. Is
The RF signal is modulated according to a positive-phase modulation signal, and the second mixer, which is the single-balanced mixer,
The RF signal delayed by a half wavelength is modulated according to the modulation signal inverted to the opposite phase, and the modulation signals output from the first and second mixers are mixed by a mixer, whereby the modulation signals are mixed. Wherein the leakage component caused by the RF signal is cancelled. 5. The mixing method according to claim 4, wherein the RF signal is a microwave in a band of about 5.8 GHz.