JPS6053962B2 - Aerial duplexer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an antenna duplexer that is extremely small and has excellent environmental resistance, and can be used, for example, in mobile radio equipment.

The configuration of a conventional antenna duplexer (hereinafter referred to as a duplexer) used in the VHF and UHF bands is shown in FIGS. 1A to 1C.

Here, A is a circulator type, B is a λ/4 coaxial line type,
C is a series circuit compensation type using a lumped constant. In the figure, 1 is a transmission filter, 2 is a reception filter, and 3 is a coupling circuit. A's server ^, comb bandpass band must be made sufficiently wider than the passband widths of the transmission bandpass filter (BPFI) and reception bandpass filter (BPF) 2.

A (BPF) 1 and a transmitting circuit are connected to a port 31 of the circulator 3, a (BPF) 2 and a receiving circuit are connected to a port 32, and an antenna circuit is connected to a port 33. This duplexer has the disadvantage that it has a large structure and is expensive because it includes a circulator. λ/ in Figure 1B
4 coaxial line type duplexer connects coaxial line branch 4 to one end of (BPF)1 and (BPF)2, and (BPF)1
)2 center frequency f.

The length 11 of the branch 4 is set to λ2/4 so that the impedance at (wavelength λ,) is open. Similarly, (BPF)
2 is the center frequency f of (BPF) 1, and the length 12 of the branch 4 is λ, so that the impedance of (wavelength λ2) is open.
Take /4. Then, connect the coaxial lines to form a combined circuit. Therefore, in order to compensate for variations in filter characteristics, it is necessary to adjust the branch lengths l, . The series resonant circuit compensation type using lumped constants shown in FIG. 1C has a series resonant circuit 5 connected in parallel to the coupling circuit 5.

Although this duplexer is small in size, since it uses lumped constants, the Q of the resonant circuit is low and loss increases, making it impractical for use in high-standard mobile radio equipment. Furthermore, a problem common to FIGS. 1A, B, and C is the cable terminal treatment of the high frequency lines of the coupling circuits 3, 4, and 5.

Due to the manufacturing procedure, the combined circuit adjustment is performed after each filter is adjusted individually, and each filter generally requires air-tight treatment to prevent moisture. Therefore, the coaxial cable terminal of the combined circuit is a coaxial connector and the end of each filter is The connector had to be airtight and was expensive. Of course, another method is to prepare all of these separately, but this requires at least three airtight connectors, which is disadvantageous in mass production. Furthermore, since the case is large, it is difficult and expensive to seal the entire case after adjusting the coupling circuit. Therefore, an object of the present invention is to improve the above-mentioned drawbacks of the prior art in terms of cost and manufacturing, and its main purpose is to use inexpensive airtight terminals (glass terminals) for the terminals of filters with high case tightness, and The coupling circuit is constituted by a strip line provided on a dielectric substrate and is housed in a simple coupler case.

According to the present invention, the airtightness of the case after adjustment only needs to be performed on the coupler case that does not require high airtightness, and adjustment can be easily performed using the adjustment pattern that is provided as necessary on the microstrip line. , and any distributed constant circuit other than a branch circuit can be inserted as a coupling circuit. Therefore, the present invention provides a compact duplexer that is small, inexpensive, lightweight, and suitable for mobile communications. Examples will be described below with reference to the drawings. FIG. 2 shows an embodiment of the present invention, in which 6 is the entire coupling circuit, 6-1 is a coupler case, 7 is a dielectric substrate, 8 is a strip line made on the dielectric substrate, and 9 is a strip line. The impedance adjustment strip line 10 is the center frequency F of (BPF)2.
The length of the line section 11 is selected so that the impedance of (BPF) 1 is maximized with respect to 2, and the length of 11 is selected so that the impedance of (BPF) 2 is maximized with respect to the center frequency f1 of (BPF) 1. This is the railway line part.

The strip line 10 passes through a hermetic terminal 12 (BPF) 1
The excitation line 12-1 is connected to the ground conductor 13 within the filter. Similarly, the strip line 11 passes through the hermetic terminal 12 to the excitation line 12 of (BPF) 2.
-1, and the excitation line 12-1 is grounded to the ground conductor 13 within the filter. Also, the ground conductor 1 of the dielectric substrate 7
6 is also grounded to the filter ground conductor 13. The strip lines 10 and 11 are combined as shown in FIG. 2, and connected to the connector 14 via the strip line 8. 15 is an excitation stage resonator on the duplexer side of the filters 1 and 2, 15a is a core, and 15b is a center conductor.

This resonator is tuned as follows.

As explained above, the strip lines 10 and 11 are each selected at a distance that maximizes its impedance with respect to the center frequency of the filter on the other side. At this time (BPF)
1 and (BPF)2 are shown in the Smith charts of FIGS. 3A and 3B. In Figure 3A, the center frequency of (BPF)1 is matched with f1, and the center frequency of (BPF)2 is F2.
Figure 3B shows that the impedance becomes infinite.
indicates that the center frequency of (BPF)2 is f1 and the impedance becomes infinite. This (BPF)1, (
By connecting BPF) 2, the characteristics of a duplexer can be obtained. However, in general, the impedance seen from the coupling circuit of the transmitting and receiving filters varies, and fine adjustment may be required in the case of a high-standard duplexer.

To compensate for this, the strip lines 10 and 1 in FIG.
Solder the switch line 9 near 1 to 1.
Selectively connect to strip lines 0 and 11. The duplexer using the microstrip line according to the present invention has the following advantages.

(1) Connection between the airtight terminal and the strip line is easy, does not impair the airtightness of the filter itself, is economical, and has good electrical characteristics.

(2) Variations in the impedance of a single filter can be easily adjusted using a coupling circuit.

(3) Any functional circuit other than branching can be easily formed as a coupling circuit, and it is small.

Compared to the circulator type, this has a simpler coupling circuit configuration, leading to lower prices. Compared to the λ/4 coaxial line type, compensation adjustment due to variations in filter characteristics is easier.

Compared to the series resonant circuit compensation type using lumped constants, this has the advantage of lower loss. In addition, by choosing a large dielectric constant of the dielectric substrate of the microstrip line,
Compared to conventional duplexers, it is extremely small and provides good characteristics. In Fig. 2, the coupler case is installed at right angles to the filter for the sake of explanation, but in reality, by providing this case on the top, bottom, and end sides of the filter, the overall volume of the duplexer can be made smaller. Something will happen.

Further, the airtight terminal and the conductor pattern on the board can be easily connected by making a hole in the board, inserting the lead of the airtight terminal, and soldering. An example of this is shown in FIGS. 4A and 4B. Here, FIG. 4A is a plan view corresponding to FIG. 2A, and FIG. 4B is a cross section taken along line A-A in FIG. 4A (7). In the present invention, the coupling circuit of the transmitting filter and the receiving filter of the duplexer is composed of a microstrip line, and various functional circuits can be used as the coupling circuit, adjustment is easy, and an airtight terminal is used as the terminal on the filter side. This makes it easy to make the entire shared unit airtight.

These features make it ideal for use as a compact antenna duplexer for car telephones and the like, from the standpoint of compactness and mass production.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1A, 1B, and 1C are configuration examples of a conventional duplexer, and FIGS. 2A and 2B are configuration examples of a resonator according to the present invention. 3A and 3B are Smith charts showing the relationship between the impedances of the transmitting and receiving filters of the duplexer according to the present invention, and FIGS. 4A and 4B are other configuration examples of the duplexer according to the present invention. 6... Coupling circuit, 7... Dielectric substrate, 9... Strip line for impedance adjustment, 10, 11... Strip line, 12... Airtight terminal, 12-1... Filter excitation line , 13...filter ground conductor, 14...
Connect. Evening, 15...excitation stage resonator.

Claims (1)

[Claims] 1. In an antenna duplexer that has a transmission filter, a reception filter, and a coupling circuit for these two filters, the coupling circuit is configured by a Y-branch made of strip lines on a dielectric substrate, and the filter is connected from the intersection of the Y-branches. Determine the electrical line lengths of the arms of the Y branch so that the impedance seen at one becomes an open impedance at the passing center frequency of the other filter, and connect strip pieces parallel to the arms to the arms as necessary. An antenna duplexer characterized in that a circuit case is provided separately from the transmission filter case and the reception filter case, and the coupling circuit and each filter are connected through airtight terminals provided on the filter side.