JPS6038883B2 - notsuchi filter - Google Patents

Description

[Detailed description of the invention] The present invention relates to a notch filter.

In a color television transmitter, power amplification is performed on a video carrier wave and a video color subcarrier wave (hereinafter, the frequency of both carrier waves will be collectively referred to as fv, and the frequency of only the video color subcarrier wave will be referred to as $), and a separate amplifier is used to amplify the power of the video carrier wave and video color subcarrier wave. Power amplifies the carrier wave (hereinafter referred to as its frequency),
A constant impedance notch diplexer (hereinafter abbreviated as CIN diplexer) absorbs spurious signals and combines fv and fa.

And conventional CIN evening, . The duplexer is a notch filter (VHF) consisting of a semi-coaxial resonator depending on the frequency used.
) or a notch filter consisting of a rectangular waveguide (UH
In the case of F), two sets of cascade-connected notch filters, for a total of four notch filters, are inserted between the combined output terminals of the two hybrid circuits, making the whole structure large and complicated, resulting in high costs. It cannot be avoided.

An object of the present invention is to realize a notch filter suitable as a component of a CIN diplexer, for example.

FIG. 1 is a side view showing one embodiment of the present invention, and FIG. 2 is a side view showing an embodiment of the present invention.
Its front view, FIG. 3 is a sectional view of the A-A section in FIG. 1,
FIG. 4 is a cross-sectional view of the section BB in FIG. 2, and in each figure, 1 is a cavity resonator made of a circular waveguide, 2 is a coupling hole,
Reference numeral 3 denotes a coupling line, which is provided facing the coupling hole 2.

A main line 4 forms a T-branch circuit together with the coupled line 3.

Reference numeral 5 denotes a shade provided outside the T-branch circuit, one end of the coupled line 3 is connected to this weight body 5, and the end thereof is connected to the T-branch point.

Coaxial terminals 6 and 7 connect each internal conductor to the end of the main line 4.

Reference numeral 8 designates a resonant frequency fine adjustment element, and although the figure shows an example in which four elements are attached, two mutually orthogonal elements may be attached.

9 is a mode coupling fine adjustment element.

Incidentally, the coupled line 3 and the main line 4 are formed using strip lines or ordinary conducting wires.

If the inner diameter of the resonator 1 is D, then TE, . The cutoff wavelength input c in the mode is input C 1.708D TMo, the cutoff wavelength input c in the case of the input C31-3
08D If the operating frequency is f and the cutoff frequency is fc, then TE, .
The unloaded Q (Qu) in the mode is also TE, . The maximum power capacity Pmax (Fukuzume N) in the case of mode is Pmax
x=2.7in (in) ^g Here, input is the wavelength used, input g is the wavelength within the tube, and Figure 5 (horizontal axis is the waveguide, vertical axis is Q) is a resonator made of a rectangular waveguide. TE of
, the unloaded Q (a curve) in the o mode' and the TE of the resonator made of a circular waveguide, . No-load Q in mode (
As is clear from the figure, the unloaded load Q of the circular waveguide is much higher than that of the rectangular waveguide. Therefore, the notch filter of the present invention is combined with a hybrid circuit to create a CIN diplexer. When configuring the notch filter, the amount of attenuation at the attenuation frequency of the notch filter is large, and it is possible to reduce the insertion loss of the equivalent bandpass waveform when combined with a hybrid circuit.

Now, by appropriately selecting the inner diameter D of the cavity resonator 1 and adjusting the fine adjustment elements 8 and 9, the frequencies fa and fv-Q: fss
(Q will be explained later), and if you introduce a signal and fss to one of the connectors, for example 6,
Excitation is performed by magnetic coupling via the main line 4, coupling line 3, and coupling hole 2, and the electric field vector in the resonator 1 is
As shown in the figure, the electric field Ea for fa and the electric field Ess for fss coexist orthogonally.

Note that Has is an excitation magnetic field. When the notch filter of the present invention is used for general communications, the total length of the coupled line 3, that is, the length from the T-branch point to the short-circuit point, should be made to approximately match the wavelength table of the signal introduced from the connector 6 or 7. , it is necessary to form it so that the transmission characteristics are symmetrical and the reflection characteristics in the passband are good. However, when using it as a component of a Cm diplexer for color television, it is necessary to form the connector 6 or 7.
The video carrier wave and video color subwave are slightly shorter than the respective wavelengths of the signals fa and fSS (fss = fv-Q, and Q = 3.59 MHz in the current color television transmitter in Japan) introduced into the video carrier. The carrier wave is formed so that its transmission characteristics satisfy standard values.

In this case, as shown in Figure 7 (the frequency f of the horizontal koji is expressed in MHz, and the vertical axis indicates the attenuation amount ATT in dB), the reflection characteristics at the passing castle deteriorate somewhat, but the reflection loss is almost 0.
．． 1dB is hardly a problem.

In the figure, fs:fv13.58MH2 is a video color subcarrier. In addition, in this case, as shown in Figure 8 (both machine axis and vertical axis are the same as Figure 7), fa and fss
A resonance frequency fm due to unnecessary resonance exists in a higher frequency range.

Next, FIG. 9 is a block diagram showing an example of a CIN diplexer used in a color television transmitter etc. by combining the notch filter of the present invention with a hybrid circuit, in which HYBI and HYB2 are hybrid circuits, respectively. Each coupling coefficient is used to form a two-way Kawamura Momohiro Hatehata combiner. Ru.

TI and T2 are input terminals of HYBI and HYB2, T3
and T4 are isolation terminals for HYB2 and HYBI, RET is a non-reflection terminator, NFI and NF2 are the above-mentioned notch filters of the present invention, and are inserted and connected between coupling terminals T5 and T6 and between T7 and T8 of HYBI and HYB2. In addition, they are made to resonate at two frequencies, fa and fv-Q (when used in a current color television transmitter, Q=3.58 MHZ), respectively. When a signal consisting of two frequency components fv and fv-Q is applied to the input terminal TI and a fa signal is applied to the input terminal T2, the frequency component of fv-Q is reflected by NFI and NF2 and passed through the terminal T4 without reflection. Absorbed by the terminator RET, the frequency component of fv becomes NF
It appears at terminal T3 via I and NF2.

Also, the signal fa applied to the terminal T2 is NFI and NF2.
It is reflected at the terminal T3 and is combined with the signal fv.
Figure 10 shows the transmission characteristics between terminals TI and T3, Figure 11 shows the transmission characteristics between terminals T2 and T3, and Figure 12 shows the transmission characteristics between terminals TI and T3.
These are curve diagrams showing the transmission characteristics between T2, and as is clear from each diagram, the transmission characteristics are extremely good.

Note that the horizontal and vertical axes in FIGS. 10 to 12 are the same as in FIG. 7. CI using the notch filter of the present invention
When configuring an N diplexer, various transmission characteristics can be made good as described above, and the number of notch filters can be halved compared to the conventional type, so the configuration is extremely simple, the characteristics are stabilized, and , it is possible to reduce costs.

[Brief explanation of the drawing]

1 to 4 are diagrams showing one embodiment of the present invention, FIG. 5 is a characteristic curve diagram thereof, FIG. 6 is an electromagnetic field vector diagram for explaining the operation, and FIGS. 7 and 8 are diagrams showing an embodiment of the present invention. Characteristic curve diagrams. Figure 9 is a diagram showing an example of a CIN diplexer constructed using the notch filter of the present invention. Figures 10 to 12 are characteristic curve diagrams thereof. 1...Cavity resonator , 2...
...Joining hole, 3...Connecting line, 4...Main line, 5...Sparrow body, 6 and 7...Coaxial terminal, 8... ...Fine adjustment element for resonance frequency, 9...
...Mode coupling tuning element, HYBI and HYB2...
...hybrid circuit, RET...non-reflection terminator, NFI and NF2...notch filter of the present invention, TI and T2...input terminal, T3 and T
4...Isolation terminal, T5 to T8
......It is a coupling terminal. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 9 Figure 8 Figure 10 Figure 11 Figure 12

Claims (1)

[Claims] 1. A coupling line provided opposite to a coupling hole drilled in one end wall of a cavity resonator made of a circular waveguide, a main line that forms a T-branch circuit together with this coupling line, and a line approximately opposite to the coupling line. A notch filter comprising a plurality of resonant frequency fine adjustment elements attached to the peripheral wall of the cavity resonator with an angular difference of 45 degrees.