JPH0112401Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a double-pass type band-removal filter having passband characteristics on both the low-frequency side and the high-frequency side of the removal frequency.

Conventionally, there is a wave transmitter of this type in the VHF band and UHF band, as shown in FIG. 1, for example. This circuit has a capacitance C between input terminal 1 and output terminal 2.
A plurality of (four in this case) series resonant circuits 3 each having an inductance L and an inductance L are connected. Second
The figure shows its frequency characteristics, where _PL is the low-pass frequency, _C is the removal frequency, and _PH is the high-pass frequency.

By the way, in this circuit, if the frequency interval between the rejection frequency and the pass frequency (low-frequency side and high-frequency side) is narrow, the Q per resonator stage must be made very large. Both do not fit well into the pass range. However, in order to increase Q,
The drawbacks are that the size of each stage of the resonator becomes very large, and at the same time, the manufacturing cost increases. or,
If the attenuation amount per resonator stage is increased, it becomes difficult to obtain both-side passband characteristics when the frequency interval between the removal frequency and the pass frequency is narrow, so the attenuation amount per resonator stage cannot be increased very much. Therefore, if a large amount of attenuation at the removal frequency is required, a large number of resonator stages is required.

Furthermore, since the standing wave ratio characteristics in the low-pass band and the standing wave ratio characteristics in the high-pass band cannot be adjusted independently of each other, adjustment is extremely difficult. .

This idea was made in view of the above circumstances,
The purpose is to provide a band-reject waver with both sides passing, which is small, inexpensive to manufacture, and easy to adjust.

This idea is to obtain a double-sided passband characteristic by combining a conventionally known band-removal filter with a passband characteristic on one side only, which is relatively small and has a steep rise characteristic. Even when the distance between the low-frequency side and the high-frequency side is narrow, the device is compact and can easily obtain both-side passband characteristics.

In other words, in the demultiplexing and mixing filters, a low-pass band-removal filter and a high-pass band-removal filter are connected from each branching point of the demultiplexing and mixing filters through approximately 1/4 wavelength lines, respectively. For example, if we consider a high-frequency signal, if we look at the low-pass band-elimination filter from each branch point for splitting or mixing, it will be in the cutoff range of the low-pass band-elimination filter, and it will be very high-frequency. It becomes an impedance, and the high-pass side is not interfered with by the low-pass side. The same principle applies to low-pass signals as well, so that the low-pass side is not interfered with by the high-pass side. Therefore, a low-pass band-removal filter having a steep rise characteristic and passing only on the low-frequency side is inserted between the low-pass terminals of the branching filter and the mixing filter, and By inserting a high-pass band-removal filter with a steep rise characteristic that passes only the high-frequency side between the high-frequency side pass terminal of the mixing filter and the high-frequency side pass terminal of the mixing filter, the low-frequency side and high-frequency side can be adjusted individually. At the same time, it is possible to obtain both-side passing characteristics with a small size and a steep rise characteristic.

An embodiment of this invention will be described below with reference to the drawings. FIG. 3 shows a known band-removal waveform (hereinafter referred to as a low-pass waveform) 11 having a passband characteristic only on the low frequency side as shown in FIG. In this low-pass transducer 11, a series resonant circuit consisting of a capacitor C and an inductance L is a circuit for obtaining an attenuation pole (removal characteristic), and an inductance L connected in parallel to this series resonant circuit is an attenuation pole. This is a reactance correction element for obtaining a passband on the low frequency side of the . FIG. 5 shows a known band-removal waveform (hereinafter referred to as a high-pass waveform) 12 having a passband characteristic only on the high-frequency side as shown in FIG. In this high-pass transducer 12, the LC series resonant circuit is a circuit for obtaining an attenuation pole, and the capacitor C connected in parallel with this series resonant circuit is for obtaining a pass band on the high frequency side of the attenuation pole. This is a reactance correction element.

In FIG. 7, a first line 23 and a second line 24 are provided between the input terminal 21 and the output terminal 22, and the high-pass wave generator 12 is connected to the first line 23 at λ/2.
The low-pass waveform 22 is connected to the second line 24 in four stages with an interval of λ/4 (λ: wavelength).
They are connected in four stages with an interval of 4.

8a, b, and c show the frequency characteristics of each block portion of the circuit of FIG. 7, respectively. Figure 8a shows block A (low-pass waver 11 and high-pass waver 12 in the first stage) and block D (low-pass waver 11 and high-pass waver in the fourth stage). This shows the frequency characteristics of the waveform generator 12), which separates and combines the low-pass frequency _PL and the high-pass frequency _PH , respectively. 8th
In figure a, the solid line shows the characteristics between the input terminal 21←→X (or The characteristics between the output terminals 22) are shown.

FIG. 8b shows the frequency characteristics of the block B (second and third stage low-pass transducer 11), which ensures the amount of attenuation at the removal frequency _C. Furthermore, FIG. 8c shows block C (second,
This shows the frequency characteristics of the third-stage high-pass transducer 12), which ensures the amount of attenuation at the removal frequency _C.

In the circuit of this invention, after demultiplexing _PL and _PH , the attenuation of _C is ensured in each path, and the circuit is configured to mix _PL and _PH again, so both resonators have good single-pass characteristics. , if the interval between the removal frequency and the passing frequency is considered to be the same, the circuit structure can be made smaller than that of the conventional circuit configuration. Furthermore, if the outer shapes are considered to be the same, a steep attenuation characteristic with a narrow frequency interval between rejection and passage can be obtained. FIG. 9 shows a comparison of the characteristics of a conventional circuit and a circuit of this invention, assuming the same external size.

In the figure, the solid line shows an example of the characteristics of the conventional circuit, and the dotted line shows an example of the characteristics of the circuit of this invention, in which the rise characteristics are greatly improved.

When this idea was implemented in a 150MHz band band-rejection waveform, it was found that the frequency interval Δ' between the low-pass frequency _PL ' and the high-pass frequency _PH ' could be reduced with the same external size as a conventional waveform. We were able to make it approximately 1/2 (Δ'≒1/2Δ).

In addition, in the case of the circuit of this invention, since the propagation paths of the high-pass frequency and the low-pass frequency are separated like the first line 23 and the second line 24, the respective pass bands are different from each other. It is now possible to independently adjust the standing wave ratio in the 200°C, making the adjustment very easy.

As described above, according to this invention, by separating the propagation paths of the low pass frequency and the high pass frequency, the frequency interval between the rejection frequency and the pass frequency (low pass frequency and high pass frequency) is greatly reduced. Even in a narrow case, it is possible to easily realize band elimination characteristics having both-side pass characteristics. Furthermore, it becomes very easy to adjust the standing wave ratio in the passband, and it is possible to manufacture inexpensive products.

[Brief explanation of the drawing]

Figure 1 is a circuit configuration diagram of a conventional band-elimination filter having both-side passband characteristics, Figure 2 is a characteristic diagram of the circuit in Figure 1, and Figure 3 is a conventional band-elimination waveform having lower-side passband characteristics. 4 is a characteristic diagram of the circuit shown in FIG. 3, FIG. 5 is a circuit diagram of a conventional band-elimination waver having high-pass band characteristics, and FIG. FIG. 7 is a circuit configuration diagram of a band-removal filter according to an embodiment of this invention.
Figures a to c are characteristic diagrams for each block of the circuit of Figure 7, respectively, and Figure 9 is a diagram comparing the characteristics of the conventional circuit and the circuit of this invention. DESCRIPTION OF SYMBOLS 11...Low-pass wave generator, 12...High-pass wave generator, 21...Input terminal, 22...Output terminal, 23...First line, 24...Second line.

Claims (1)

[Scope of utility model registration request] a duplexer comprising a low-pass band-removal filter and a high-pass band-removal filter; a mixer comprising a low-pass band-removal filter and a high-pass band-removal filter; A band-removal filter having a low-pass characteristic is provided between the output terminal of the low-pass band-removal filter of the splitter and the input terminal of the low-pass band-removal filter of the mixer, and the A band-removal filter having a high-pass characteristic is provided between an output terminal of a high-pass band-removal filter of the mixer and an input terminal of the high-pass band-removal filter of the mixer. wave removal device.