JP2745523B2 - Frequency converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] For example, the present invention relates to a frequency converter used for converting a high-frequency signal into an intermediate frequency signal or converting an intermediate frequency signal into a high-frequency signal. - with the aim of promoting the reduction of influence on the frequency characteristics, plus the signals of the signal and the frequency f ₂ frequency f ₁ at one end of the diode, the frequency converter to take out a signal of a frequency f ₃ from the one end, the the other end of the diode, becomes short-circuited at the frequency f _1, constructed as to ground via a multiplier signal suppression circuit according to a predetermined impedance at the frequency nf _1.

[Industrial applications]

The present invention relates to a frequency converter used for converting, for example, a high-frequency signal to an intermediate-frequency signal or converting an intermediate-frequency signal to a high-frequency signal.

2. Description of the Related Art In recent years, microwave digital communication has been widely performed, and accordingly, a quadrature amplitude modulation method has been used in order to improve frequency use efficiency.

Therefore, the transmitting side of the digital wireless device generates a quadrature amplitude modulated wave of, for example, 70 MHz band using a digital signal to be transmitted, converts this to a frequency converter, for example, to a 6 GHz band, and transmits it to the opposite station. However, it is necessary for the frequency converter to perform frequency conversion without affecting the amplitude characteristics of the quadrature amplitude modulated wave.

[Conventional technology]

FIG. 4 shows a block diagram of a conventional example, which is a case of a single-balanced frequency converter (up-converter) in the microwave band. Hereinafter, the operation of the figure will be described on the assumption that the frequency of the local signal is 6 GHz and the intermediate frequency signal is 70 MHz.

First, after the local signal 6GHz input from terminal LO-IN is passed through the capacitor C _1, some high-frequency 90 degree hybrid terminal →, through a matching unit 12, for example, shot diode (hereinafter, abbreviated as diodes) D ₁
Rest terminal →→, applied to the diode D ₂ via a matching unit 13.

On the other hand, the 70 MHz intermediate frequency signal input from the terminal IF-IN is applied to the diodes D ₁ and D ₂ via the capacitor C ₃ , the high frequency chokes ch ₁ and ch ₂ , and the matching devices 12 and 13, A 6.07 GHz signal is generated due to the nonlinear characteristics.

The 6.07 GHz signal generated by the diode D ₁ is passed through the matching device 12 and the high frequency 90 ° hybrid terminal →→, and the 6.07 GHz signal generated by the diode D ₂ is passed through the matching device 13 and the high frequency 90
° is synthesized via the hybrid terminal →, is output to the load from the terminal RF-OUT through the capacitor C _2.

Here, the matching devices 12 and 13 are for ensuring that the local signal of 6 GHz is sufficiently applied to the diodes D ₁ and D _{2 and} that the signal of 6.07 GHz is supplied to the load without loss.
For example, it is composed of a microstrip line open stub or the like.

Further, ch ₃ and the resistor R ₁ is an element of the DC bias supply to the diode D _1, D _2. Further, the terminal of the high-frequency 90 ° hybrid 11 is an isolation port for a 6.0 GHz signal input from the terminal, and the terminal is an isolation port for a 6.07 GHz signal output from the terminal.

[Problems to be solved by the invention]

Here, since the frequency converter uses the non-linearity of the diode, there are many intermodulation components such as a converted desired signal, a multiplied wave of the signal input to the diode, and a converted signal of the multiplied wave and the input signal. Not only does this signal generate spurious signals, but the signal of the intermodulation component causes a deviation in the frequency characteristics of the desired signal. As a result, when the desired wave includes an amplitude modulation component such as a multilevel quadrature amplitude modulation wave, the error rate of the demodulated digital signal deteriorates.

That is, there is a problem that the frequency characteristics of the desired signal are affected.

An object of the present invention is to reduce the influence on the frequency characteristics of a frequency-converted desired signal.

[Means for solving the problem]

 FIG. 1 is a block diagram showing the principle of the present invention.

In the figure, D in the diode, 2 becomes short-circuited at the frequency f _1, is a multiplication signal suppression circuit according to a predetermined impedance at the frequency nf _1.

[Action]

Generally, signals input to the frequency converter are a local signal and a high-frequency signal when the frequency converter operates as a down converter, and are a local signal and an intermediate frequency signal when the frequency converter operates as an up converter. Even in this case, the level of the local signal is much higher than the level of the high frequency signal or the intermediate frequency signal.

Therefore, the multiplied component of the local signal and the high-frequency signal or the intermediate frequency signal cause intermodulation, and fall as spurious in the band of the desired signal, thereby causing an amplitude deviation in the frequency characteristics of the desired signal.

For this reason, in the present invention, the other end of the diode is grounded via the multiplication wave suppressing circuit 2 so that the multiplication component having the highest level (usually a multiplication component) among the multiplication components of the local signal is consumed by a predetermined impedance. Thus, the occurrence of spurious signals is suppressed so that the frequency characteristics of the desired signal are not affected.

Since the multiplication suppressing circuit is short-circuited for the basic component of the local signal, the frequency conversion operation of the diode is performed normally.

〔Example〕

FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 is an explanatory diagram of the operation of the harmonic wave suppression circuit.

Here, the 21 wavelength lines 21 and 22 and the resistor R _2, and the / 4 wavelength lines 23 and 24 and the resistor R ₃ are components of the multiple wave suppression circuit 2. Note that the same reference numerals indicate the same objects throughout the drawings. Hereinafter, the operation of FIG. 2 will be described with reference to FIG. 3 with n = 2.

First, as shown in FIG.
Characteristic impedance Z _{0 in} the middle of short stub of λ _1/2
Which was inserted into equal resistance R _2, a 21, 22 is a line of λ _1/4. Here, λ ₁ indicates the wavelength of the local signal.

Frequency f ₁ of the local signal as shown in the high-frequency current distribution drawing of the circuit becomes zero at a position (hereinafter, f ₁ and omitted), the R _2, since the maximum in 2f _1, with respect to f ₁ It is not influence on the high frequency current due to the insertion of R _2, a high-frequency current is consumed by R ₂ with respect to 2f _1.

Further, the impedance viewed from a point relative to 2f ₁ is in short-circuit state with respect to f ₁ as shown in FIG. 3 (b) is terminated by R _2.

Next, in the 21 to 24 second view is a line of lambda _1/4, becomes 0.4 times when the consideration of the alumina substrate a wavelength shorting ratio. Further, since R ₂ and R ₃ act as DC bias resistors for the diodes D ₁ and D ₂ , R ₁ can be omitted.

That is, lines 21 and 22 to the diode D _1, the multiplication signal suppression circuit including a resistor R _2, a diode D ₂ lines 23 and 24, also frequency conversion by connecting a multiplier suppression circuit including a resistor R ₃ Although operation is performed normally, 2f ₁ components generated output is consumed by the resistor R ₂ and R ₃ is attenuated approximately 10~20dB compared with the conventional example.

As a result, the influence on the frequency characteristics of the desired signal can be reduced.

〔The invention's effect〕

As described above in detail, according to the present invention, there is an effect that the influence on the amplitude-frequency characteristics of the frequency-converted desired signal is reduced.

[Brief description of the drawings]

 FIG. 1 is a block diagram showing the principle of the present invention, FIG. 2 is a block diagram of an embodiment of the present invention, FIG. In the figure, D indicates a diode, and 2 indicates a harmonic wave suppression circuit.

Claims (1)

(57) [Claims] [Claim 1] In addition to the one end of the frequency f ₁ of the signal and the frequency f ₂ of the signal and a diode (D), in the frequency converter to take out a signal of a frequency f ₃ from the one end, the other end of the diode (D) Is short-circuited at a frequency f ₁ and grounded via a harmonic suppression circuit (2) having a predetermined impedance at a frequency nf ₁ (n is a positive integer greater than 1). Frequency converter.