KR900002450B1 - Block-type frequency transition device - Google Patents

Abstract

The converter utilizes a bandpass impeding filter comprising two symmetric "L" shaped spur lines depositing in the micro strip line. The filter is deposited in the former stage of a mixer for mixing the RF signal from an antenna and local oscillation signal from an oscillator. The center of the impeding band can be varied by the width, length, and gap of spur lines.

Description

Band Rejection Filter Using Spurline and Block Type Frequency Converter

1 is a schematic diagram showing the configuration of an outdoor portion of a conventional satellite reception system.

2 is a diagram showing an embodiment of a band reject filter according to the present invention.

3 is a diagram showing the frequency characteristics of the band reject filter according to an embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

1: antenna 2: low noise amplifier

3: block type frequency converter A: filter

B: Mixer C: Fixed Local Oscillator

D: Low pass filter E: Medium frequency amplifier

SP: Spurline MS: Micro Strip Line

a: length of spurline b: spacing of open ends of spurline

d: spacing between spurline and microstrip line

l: spacing between spurline and spurline

s: width of spurline w: width of microstrip line

The present invention relates to a band reject filter using a sper line in a micro strip line and a block type frequency converter using the same.

As shown in FIG. 1, the outdoor unit of the satellite TV receiving system includes an antenna 1 installed outdoors and receiving a satellite signal, and a low noise amplifier amplifying the satellite signal received by the antenna 1; 2) and a frequency converter 3 for converting the RF signal of the 4 GHz band to the intermediate frequency IF of the 1 GHz band in order to reduce the attenuation of the signal in the diagram leading to the indoor equipment. The output of the frequency converter 3 is It is input to an indoor receiver (not shown), and the receiver selects a satellite signal to watch and outputs audio and video signals to a TV monitor.

The satellite reception system is generally classified into a single conversion method and a block type double conversion method according to a frequency conversion method. The former selectively converts only one desired channel among the RF signals received through the antenna to an intermediate frequency. The latter refers to a method of converting all RF signals of all channels received through an antenna to a predetermined intermediate frequency.

However, in the single conversion system, there is a problem in that the reception state is not good because the unwanted video signal is mixed with the desired channel. Therefore, in recent years, a block-type double conversion scheme has been generally adopted. The reason for this is that the above-described interference between the channels is small, and even in selecting a predetermined channel, the RF signal (RF) in the 4 GHz band is simply used as in the first diagram. It can be achieved by MIXING a fixed local oscillation signal (LOC) of 5.15 GHz and 5.15 GHz.

The configuration of such a block type frequency converter is as follows. That is, after the satellite signal input through the antenna (1) through the filter unit (A), the local oscillator (C) using a mixer (MIXER) (B) to convert this signal into a 1 GHz primary intermediate frequency signal In this case, the fixed local oscillation signal (usually 5.15 GHz) (LOC) outputted from the RF signal and the 4 GHz band RF signal are mixed to convert the entire channel band to the intermediate frequency of the 1 GHz band. In addition, the local oscillator C is configured to supply about +10 dBm of power to the mixer B for the smooth operation of the mixer B. The first intermediate frequency signal is amplified by the low pass filter (D) and the intermediate frequency amplifier (E), and then applied to an indoor receiver so that a signal of a desired channel is tuned and applied to the TV monitor.

By the way, the filter A in the block type frequency converter 3 serves to prevent the local oscillation signal LOC of the local oscillator C from flowing back to the low noise amplifier 2 side.

As the filter (A), a band pass filter, a low pass filter, a high pass filter, and the like have been conventionally used, and they usually constitute a small block type frequency converter because of the large occupied area ratio in the block type frequency converter 3. Not only does it cause a problem, but there is a big disadvantage of loss of a signal in a pass band.

Accordingly, an object of the present invention is to provide a block type frequency converter having a band stop filter having a small size and a small loss of a signal in a pass band.

Another object of the present invention is to provide a band reject filter formed by forming a plurality of spur lines in a micro strip line.

In the ultra-high frequency band of several GHz or more, passive devices cannot be used as in the low frequency band. Therefore, also in the structure of a filter, it cannot be made using the coil and capacitor used at low frequency.

In contrast, in the present invention, by forming a spur line in a micro strip line, an inductance of a coil and a capacitance of a capacitor are equivalently provided to provide a band reject filter having a predetermined band stop width.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The band reject filter according to the present invention is constructed by using a plurality of spur lines in the micro strip line MS, as shown in FIG.

In this embodiment, two "b" shaped spurlines are formed symmetrically with each other, where the important points are the width (w) of the microstrip line, the width (s) of the spurline, the length of the spurline (a), and the spurs. The open end spacing (b) of the line, the spacing (d) of the spurline and the microstrip line, and the spacing (l) of the spurline and the spurline.

In order to configure the band reject filter using the micro strip line, the following procedure is performed.

(A) Calculate the Chebycheff Coefficient of the low pass filter that meets the filter specification. The equation for calculating Chebyshev coefficients, such as the lowpass filter above, is:

r = 1 for n: odd (odd)

r = tanh ² (β / 4) for n: even

g ₁ = 2a ₁ / α

Where, r: Ripple in the pass band: section number, g _k: Chebyshev _{coefficients, a k, b k: g} k a parameter for determining a variable, Am.

(B) When the characteristics of the low pass filter are obtained and the Chebyshev coefficients are obtained, they are frequency shifted to the band reject filter, and the impedance of the open circuit stub of the band reject filter corresponding to the frequency characteristics is obtained. To convert the lowpass filter of paragraph (A) into a band stop filter, use the following formula.

Where W 'is the frequency of the low pass filter, W is the frequency of the band reject filter, and Wo is the center frequency of the band reject filter.

Find the impedance of an opencircuited stub for the band-stop filter above. The open circuit impedance can be obtained by the following equation.

for n = 2

Where n: number of stubs, Z _A , Z _B : termination impedance, Z _j : impedance of the open circuit stub, Z _j-1 , j: connection line impedance, g _j : Chebyshev coefficient, A = W'iaW'i Is the cutoff frequency of the low pass filter,

(C) Change the impedance of the band reject filter to the combined impedance. The formula for calculating the coupling impedance is as follows.

Where Zoe: excellent impedance, Zoo: odd impedance.

(D) Find the value of the spurline at the coupling impedance. The formula for obtaining each value of a spurline is as follows.

here,

(E) Find the length a of the spur line.

Where fo is the center frequency of the band-stop filter, εeffo is the permittivity of the effect.

(F) Find the spacing l of the spur line.

l = a

The following is the specification of spurline according to the above formula to form a bandstop filter on a 0.8 mm high glass epoxy dielectric substrate.

d = 0.68mm, s = 0.02mm, a = 8mm, l = 8mm

The frequency characteristics of the band reject filter produced with the above results are as shown in FIG.

As described above, in the configuration of the present invention, the center frequency of the stopband also changes as the width, length, and spacing of the spur lines in the micro strip line change.

In addition, according to the present invention, since the spurline is formed in the micro strip line, the occupancy area is smaller than that of other filters, whereby a small block type frequency converter can be obtained, which can be greatly utilized in the field of high frequency communication including the above-mentioned communication. Can be.

Claims (2)

A bandstop filter using a spur line, characterized by forming two "b" shaped spur lines symmetrically in a micro strip line. A block type frequency converter comprising a band stop filter using a spur line in a micro strip line, which is installed in front of a mixer for mixing an RF signal from an antenna and a local oscillation signal from a local oscillator.

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