JPS63135009A - Distributer - Google Patents

Abstract

PURPOSE:To improve the VSWR in the reduction of a transmission frequency region by setting a resonance frequency of a parallel resonance circuit comprising both capacitors and a choke coil in the vicinity of the lower limit of the transmission frequency band of the titled distribution circuit. CONSTITUTION:The distribution circuit 1 distributing an input signal to a couple of outputs, DC blocking capacitors C1, C2 inserted respectively to an input terminal and an output terminal of the distribution circuit 1 and a choke coil RFC for high frequency blocking connected between terminals at the opposite side of the distribution circuit 1 in the capacitors C1, C2 constitute the titled distributer. In this case, the resonance circuit comprising the choke coil RFC and the capacitors C1, C2 is used as the parallel resonance circuit and the resonance frequency is set in the vicinity of the lower limit of the transmission frequency band of the distribution circuit 1. Since the matching at the input terminal is taken well even near the lower limit of the transmission frequency band, the VSWR is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field J] The present invention relates to a distributor that distributes a high frequency input signal to a plurality of outputs.

[Background Art] Conventionally, this type of distributor has been provided with a current passing type configuration so that power can be supplied to the booster from the output side, and as shown in Fig. 1, the input signal is A distribution circuit 1 that distributes the output to a plurality of outputs, a pair of DC blocking capacitors C, C2, one end of which is connected to the input terminal and one output terminal of the distribution circuit 1, and both capacitors C.
, , and a high frequency blocking choke coil RFC connected between the other ends of C2. In other words, the direct current for feeding the booster is output terminal 01 and input terminal ■
The high frequency input signal from the input terminal I to the output terminal 01 is distributed through the distribution circuit 1.

By the way, the high frequency signal transmitted through the distribution circuit 1 has conventionally been set to include the FM broadcast or UHF broadcast band, that is, 76 to 770 MHz, but recently it has been set to include the HF band, 5 to 76 MHz. It has become necessary to also transmit signals such as This is because the output signals of surveillance cameras, intercoms, etc. are being converted into high-frequency signals and transmitted using the same line due to demands for so-called home automation systems.

However, when trying to extend the transmission band of the distribution circuit 1 to the lower frequency side, the impedance of the autotransformer T+ decreases, causing a problem that characteristics such as VSWR and distribution loss deteriorate. That is, when the impedance of the autotransformer T decreases, impedance conversion cannot be performed sufficiently, and the input impedance decreases, leading to deterioration of the performance characteristics. A possible solution to this problem is to increase the number of turns of the autotransformer T, but in that case, the problem arises that the distribution loss increases in the high frequency range. Generally, in the UHF band and VHF band, EI
According to the AJ standard, the characteristics shown in the table below are required, and the same performance is required in the HF band.

[Object of the Invention] The present invention has been made in a manner similar to the above points, and its object is to provide a distributor with improved VSWR in the low frequency range.

[Disclosure of the Invention] (Structure) A distributor according to the present invention includes a distribution circuit that distributes a high-frequency input signal to a plurality of outputs, and a pair of direct current channels each having one end connected to an input end and one output end of the distribution circuit. Consisting of a blocking capacitor and a high frequency blocking choke coil connected between the other ends of each capacitor, the resonant frequency of the parallel resonant circuit formed by both capacitors and the choke coil is divided into the transmission frequency band of the distribution circuit. The transmission frequency is set near the lower limit of v! This improves the VSWR in the low range of the L region.

(Example) The circuit configuration is basically the same as the conventional one, and as shown in FIG. It consists of capacitors C, , C2 for direct current blocking inserted in the capacitors C, , C2, respectively, and a choke coil RFC for blocking high frequency, connected between one end of the capacitors C, , C2 on the side opposite to the distribution circuit 1.

The distribution circuit 1 consists of an autotransformer T provided on the input side for impedance matching, a distribution transformer T2 with an intermediate tap connected to a tap installed on the autotransformer T, and in order to maintain isolation between the output. It is composed of a resistor R inserted between the output ends of the distribution transformer T2, and a phase compensation capacitor C7 connected in parallel between one end of the autotransformer T and the tap. Therefore, the high frequency signal inputted from the input terminal (2) is inputted to the distribution circuit 1 through the capacitor CI, and after its impedance is converted by the autotransformer T1, it is divided into two by the distribution transformer T2.

Here, choke coil RFC and capacitor C,
, C2 is regarded as a parallel resonant circuit, and its resonant frequency is set near the lower limit of the transmission frequency band of the distribution circuit 1. That is, capacitors C,,C2
Let the capacities of C, C2 be respectively, and choke coil RF
If the inductance of C is L, the resonance frequency f0 is given by: However, the inductance of the choke coil RFC is set to 2.8 μH, and the auto transformer T and distribution transformer T2 are equipped with cores (QMO manufactured by Nippon Ferrite Co., Ltd.).
51), and the winding tail of autotransformer T1 is 1.
:2, the distribution transformer T2 has a winding tail of 1:1, and is 5MH
When the VSWR and distribution loss were measured at 10 MHz and 10 MHz, the results shown in FIGS. 2 and 3 were obtained. As shown in Figures 4 and 5, the measurement method is to apply high frequency voltage to distributor A and measure its output voltage using network analyzer 2 (8505A manufactured by Hewlett Paracard). did. VS
WR is obtained by applying a high frequency voltage to the input terminal (2) of the distributor A and measuring the reflected voltage, and the input and output voltages are separated by the directional coupler 3. Also,
The distribution loss can be calculated by applying a high frequency voltage to the input terminals and applying a high frequency voltage to the output terminals 0, . The output voltage was taken out from 02 and measured. That is, when the input voltage is Eis and the output voltage is Eo, and Er'' l Eo/E i l, V
SWR=(1+Er)/(I Er) Distribution loss=-20
Calculated as 1oHER. As a result of the above, the knowledge that VSWR and distribution loss are minimized when the capacitance of capacitors C and C2 is around 1000 pF has been changed. In other words, according to the above equation, the resonant frequency WLf o is 2 MHz, and when the resonant frequency is set near the lower limit of the transmission frequency, the VSWR and distribution loss are almost minimum. It became.

[Effects of the Invention] As described above, the present invention includes a distribution circuit that distributes a high-frequency input signal to a plurality of outputs, and a pair of DC blocking circuits each having one end connected to the input end and 11 output ends of the distribution circuit. and a choke coil for high frequency blocking connected between the other ends of each capacitor, and the resonant frequency of the parallel resonant circuit formed by the above capacitors and the choke coil is set to the lower limit of the transmission frequency band of the distribution circuit. The VSWR is set close to
This has the advantage of being able to improve the

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIGS. 2 and 3 are characteristic diagrams of the same, and FIGS. 4 and 5 are conceptual diagrams showing a measuring method of the same. 1 is a distribution circuit, C3 and C2 are capacitors, and RFC is a choke coil. Agent Patent Attorney Ishi 1) Chief 71...Distribution circuit C,,C,...Capacitor Diagram 1 Funeral Diagram 2

Claims (1)

[Claims] (1) A distribution circuit that distributes a high-frequency input signal to multiple outputs, a pair of DC blocking capacitors with one end connected to the input terminal and one output terminal of the distribution circuit, and the other end of each capacitor. and a choke coil connected to the capacitor for high frequency blocking, and the resonant frequency of the parallel resonant circuit formed by the two capacitors and the choke coil is set near the lower limit of the transmission frequency band of the distribution circuit. Distributor.