JPS6187435A - antenna sharing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an antenna duplexer using a band-elimination P-wave device for high frequencies.

As shown in FIG. 1, multi-stage bandpass filters used in high frequency bands often have a configuration in which a plurality of series resonant circuits 13 are connected through a transmission line 14. 1 in the figure! , 12 indicate input and output terminals, respectively. Series resonant circuit] 3
may be a lumped constant resonator, but in order to improve the circuit characteristics, a distributed constant resonator with a high no-load Q is usually used. By the way, the transmission line 14 is 100100
Below O, a coaxial cable is used to reduce the size, and the line length t is approximately 1/4 wavelength at the center frequency to form a p-wave device.

The frequency characteristics of this platform insertion loss have symmetrical characteristics above and below the center frequency, as shown in the graph of Figure 2 (2).

However, although such conventional examples have good symmetrical characteristics, they cannot be said to be sufficient in terms of sharpness of frequency characteristics.

However, depending on the application, as will be described in detail later, it may be required to reduce insertion errors even if symmetry is ignored.

The antenna duplexer according to the present invention is different from the conventionally used λ
By setting the length of the y/4 coaxial couple to be about 5 to 20% shorter or longer than λy/4, the frequency characteristics of the insertion loss can be made asymmetrical with respect to the center frequency, and the insertion loss can be further reduced. +U for the band aimed at reducing
It uses a 5 wave device.

The basic configuration of the band-elimination P-wave device will be explained below.

When the length of the coaxial cable is longer than λp/4, as shown in FIG. 2, the characteristics become steep at higher frequencies than the center frequency and gentle at lower frequencies.

On the other hand, by making the cable length shorter than λ2/4, it is possible to obtain the opposite characteristics to 2, as shown in FIG.

By the way, when installing a cable as short as λy/4 (90° in terms of electrical length) or as long as possible, there are certain restrictions on the length. Figure 3 is an example of a custom-made passband for a three-stage band-stop wave transducer. The center frequency is fo, the detuning frequency from the center frequency is Δf, the horizontal axis is Δf/fo, and the vertical axis is the insertion loss. This is an example where the cable is located above the IO in the passband and the electrical length of the cable is 90° or more. In the figure, the electrical length is 90', 94.5°
(+5%), 99° (+10%), 108° (+20%)
), 117° (+30%), it can be seen that ripples occur in the characteristics of the passband as the line support increases. In normal applications, the passband ripple of the filter is preferably within IdB, so the line length is at most 2
It can only be increased by about 0%. On the other hand, it can be seen that if the line length is increased by less than 5%, the effect is small because the change in characteristics itself is small.

As a specific example, stopband center frequency 450MHz 1 passband 4
54±0. IMHz (Δf-=4.OMHz±100K
Consider the case of designing a filter of Hz). The insertion loss in the passband can be found from FIG. 3, and the relationship between this insertion loss and the line length increase is illustrated in FIG. 4. In order to keep the insertion loss within 1 dB, the line length must be increased by 5 to 2 dB.
It can be said that about 0% is appropriate, and it can be seen that 10 to 15% provides the lowest loss.

The above example describes a case where the line length is longer than λf;'/4, but the same applies when the line length is shorter.
% is a practical range.

As mentioned above, even if the cable length is shortened or lengthened by 5% or less, the symmetry of the characteristics does not change much, and even if the cable length is shortened or lengthened by 5%,
% or more changes passband insertion loss and VSW
Since the R characteristic deteriorates, it is appropriate for the cable length change to be within about 5 to 20% of λy/4. Further, in this state, the attenuation [I\] at the center frequency is almost the same as in the case of t-λ9/4.

By providing such asymmetric characteristics, insertion loss in the passband can be reduced without sacrificing the stopband characteristics. That is, in a normal circuit, if the scolding frequency is IO, the passband is more than fo + Δf, or fO - Δf
It is often the following.

For example, when receiving TV, a problem that often occurs on UHF channels is when there is an interference wave at a much higher level than the signal level of the desired signal in the adjacent channel of the desired signal, as shown in Figure 5. be. When such radio waves are received, the quality of the straight line of reception is significantly degraded due to cross-modulation interference. As a countermeasure to this problem, CATV receivers are designed to sufficiently attenuate the interfering waves with a band-elimination V-wave device, while allowing the desired waves to pass through as is. The reason for this is that since the interval between the band edges of the desired wave and the interference wave is as narrow as 6 MHz, the pass band loss becomes large in a band-pass p-wave converter.

Furthermore, the above-mentioned frequency characteristics are also required in the case of transmitting or receiving filters related to mobile radio having a narrow transmitting/receiving frequency interval, which will be described later.

In other words, if the stopband center frequency is fo, and the passband is greater than or equal to fo+Δf, the insertion loss in the passband is ■(1>λy/4) and ■(−λy/4), as shown in Figure 2.
) and ■(1<λy/4), so it can be seen that in this case, using ■(1<λy/4) is more effective in terms of insertion loss. Conversely, when the passband is fO-Δf, it can be seen that it is more effective to use ■(t>λy/4).

As mentioned above, in a bandstop p-wave device, when the passband exists either above or below the center frequency fO of the stopband, and the frequency interval between the passband and the stopband is narrow, the insertion loss in the stopband is It can be seen that this method is extremely effective in reducing

Next, an antenna duplexer according to an embodiment of the present invention will be described. FIG. 6 is a conceptual diagram showing an antenna duplexer according to an embodiment of the present invention, which is used in mobile radio equipment, etc., and uses the above-mentioned band-elimination P-wave device. In Fig. 6, 31 is an antenna duplexer, terminals 32.33.3
4 indicates a receiving terminal Rx, a transmitting terminal Tx, and an antenna terminal Ant, respectively.

The function of the antenna duplexer is that the received signal of frequency fr that enters from the antenna does not propagate to the transmission terminal Tx33 and is all transmitted to Rx3.
2, and the transmission signal of frequency f□ that enters from the transmission terminal Tx33 does not propagate to the reception terminal Rx82 and is all transmitted to Ant 8.
It has the characteristic of propagating to 4.

When configuring a duplexer with a transmission/reception interval of 10 MHz or less and a signal band of 5 MHz or less in several hundred MHz bands, band rejection P is required.
A system using two wavers is often used.

As an example, consider the case where the center frequency of the received signal band is fRo, the center frequency of the transmitted signal band is fTo, and fRO>fTo. FIG. 7 shows the circuit configuration of the duplexer in the case that both of the two band-elimination P-wave devices used in the duplexer can be realized in a three-stage configuration. Terminals 41, 42, and 43 are respectively a transmitting terminal Tx, a receiving terminal Rx, and an antenna terminal Ant.
shows. 44.45 is the series resonator, 46.47 is the coaxial cable used for the F wave generator, and 118.49 is the cable for signal synthesis. The band-stop transducer connected to the transmission terminal Tx41 includes a series resonant circuit 44 and a coaxial cable 46, and the series resonator 44 is tuned at a center frequency fRo. The coaxial cable length 46 is λy/4 at fRo.
Design to be 5 to 20% shorter. Also, the coupling cable 48 is λ
By selecting fZ/4, the impedance seen from the antenna terminal Ant48 to the transmission terminal Tx41 side is the frequency fR.
Since it becomes infinite at o, the received signal does not propagate to the transmission terminal Tx41 side. Also, since the transmission signal uses the F-wave device of the present invention, the transmission terminal Tx41 may also be the antenna terminal Ant.
43 with low loss.

Similarly, on the receiving terminal Rx42 side, the series resonator 45 is fT.
The length of the cable 47 is designed to be 5 to 20% longer than the quarter summer wavelength λy/4 at fTo, and the cable 49 for signal synthesis is designed to be equal to λ2/4. By doing so, the received signal propagates from the antenna terminal Ant43 to the receiving terminal Rx42 with low loss, and it is possible to design the design so that the wraparound of the transmitted signal to the receiving terminal Rx42 side is extremely small.

FIG. 8 shows an example of the characteristics that can be achieved by this method.

Curve 2 in the figure shows the propagation characteristics between the receiving terminal Rx and the transmitting terminal Tx, and a sufficient amount of attenuation can be ensured in the signal band. Also,
■ and ■ show the transmission 49 characteristics between the transmitting terminal Tx and the antenna terminal Ant, and between the antenna terminal Ant and the receiving terminal Rx, respectively, which are extremely effective characteristics because the method reduces the insertion loss in the passband. becomes.

As described above, the present invention uses a band-elimination P-wave device having a configuration in which a plurality of series resonant circuits are connected via coaxial cables.
This product provides an antenna duplexer that uses two band-stopping P-wave devices with a coaxial cable length longer or shorter than a quarter wavelength, and the frequency characteristics of the P-wave devices are asymmetric above and below the center frequency. Insertion loss can be reduced.

[Brief explanation of drawings]

Figure 1 is a wiring diagram showing the configuration of a multi-stage band-stop P-wave device;
Figure 3 is a characteristic diagram showing the frequency characteristics of insertion loss of the present invention and conventionally used band-stopping F-band filters; Figure 4 is a relationship diagram showing the relationship between insertion loss and line length increase, Figure 5 is a relationship diagram showing the relative relationship between interference waves and desired waves during VHF reception, and Figure 6 is a conceptual diagram of an antenna duplexer. , FIG. 7 is a wiring diagram showing the configuration of the antenna duplexer in one embodiment of the present invention, and FIG. 8 is a diagram showing the characteristics of the antenna duplexer shown in FIG. 7. 11...Input terminal, 12...Output terminal, 13...
Series resonant circuit, 14...transmission line (coaxial cable). Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 4 Figure 5 Obstruction friend Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] It has two band-elimination filters in which multiple series resonant circuits are connected via coaxial cables, and the length of the coaxial cable used for one of the band-elimination filters is shorter than a quarter wavelength, and the length of the coaxial cable used for the other band-elimination filter is shorter than a quarter wavelength. Reduce the length of the coaxial cable used for band-stop filters to one quarter
An antenna duplexer characterized by being longer than the wavelength.