JPS62241Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is used by being inserted into a transmission line to compensate for distortions in the amplitude frequency characteristics that occur in wideband microwave communication equipment, signal transmission lines, etc. and make the amplitude frequency characteristics flat. Concerning a microband variable amplitude equalizer.

In broadband microwave communication equipment, transmission lines, or microwave band circuit elements used in millimeter wave waveguide transmission systems, losses generally increase as the frequency increases due to the skin effect of the conductor, so the loss is Amplitude distortion with loss slope occurs. Since this amplitude distortion causes deterioration of communication quality, it is necessary to equalize it by some method.

Conventionally, such amplitude distortion has been equalized by using a bandpass waveform device or a bandstop waveform device, and utilized the sloped portion of the pass or reflection frequency characteristic.

However, since there are variations in transmission distortion in communication devices that are actually manufactured, it is desirable that the characteristics of the amplitude equalizer can also be varied to some extent. For this reason, in the case of an amplitude equalizer using a wave generator, it is necessary to change the resonant frequency and the amount of coupling. A wave generator type amplitude equalizer using a rip line has the disadvantage that the resonant frequency and the amount of coupling, that is, the conductor pattern cannot be easily changed. For this reason, a coaxial stub type wave circuit using capacitive coupling has been used as a variable amplitude equalizer. However, the variable mechanism was complicated and electrical adjustment was difficult. Furthermore, since equalizers using wave circuits have poor input/output impedance, it is common to use isolators connected to the input/output terminals of the equalizer, which has the disadvantage of increasing the size.

In order to eliminate the above drawbacks, the present invention combines a microstrip line with a variable attenuator or a variable capacitance element without changing the conductor pattern of the microstrip line, thereby improving the amplitude of the amplitude equalizer. An object of the present invention is to provide a variable amplitude equalizer whose frequency characteristics can be changed.

According to the present invention, there is provided an amplitude compensation circuit having a first terminal and a second terminal to which a terminator is connected; a signal transmission line coupled between the first and second terminals, and a signal transmission line connected between the first and second terminals, and a circuit from the first position of the signal transmission path to the second terminal side. an attenuator provided between the ground and a position separated by a length corresponding to a quarter wavelength of the center frequency of the transmission signal; and an attenuator provided between the first position and the ground and the center A variable amplitude equalizer is obtained that includes a resonator having a branch line that transmits signals near the center frequency toward the attenuator and reflects signals away from the center frequency toward the first terminal.

The present invention will be explained below with reference to the drawings.

FIG. 1 shows a variable amplitude equalizer according to a first embodiment of the present invention. A branch line 3 having a length that resonates at a desired frequency is connected in parallel to a signal transmission line 1 in which one end a of the signal transmission line 1 is used as an input/output terminal and a non-reflection terminator 2 is connected to the other terminal. The other terminal of this branch line 3 that is not connected to the signal transmission line is grounded, and a quarter of the center transmission signal wave is connected from the connection point b of this branch line to the terminal side to which the non-reflection terminator 2 is connected. An amplitude compensation circuit in which a variable attenuator 4 capable of attenuating and reflecting a transmission signal is connected in parallel to a point c at a position separated by a length corresponding to one wavelength (λ/4), and a terminal of the amplitude compensation circuit. A circuit 5 which applies a transmission signal to terminal a and extracts an amplitude-compensated signal from terminal a is connected thereto. In this equalizer, when a signal with a flat amplitude in the used frequency band is input to the terminal 14, the branch line 3, which is a resonator, directs the signal near the resonance frequency, including the resonance frequency, to the variable attenuator 4. transmitted to
At the same time, signals far from the vicinity of the resonant frequency are reflected back to the input side. The signal transmitted to the variable attenuator side is attenuated by the variable attenuator 4, reflected, and returned to the terminal a side. The signal transmitted without being reflected by the variable attenuator 4 is completely absorbed by the non-reflection terminator and is not reflected. The line length of the branch line 3 is determined so as to have such characteristics. Therefore, terminal 15
The same amplitude frequency characteristics as when passing through a band-stop filter are obtained.

FIG. 2 shows the amplitude frequency characteristics of this amplitude equalizer. The horizontal axis is frequency and the vertical axis is attenuation. The resonance frequency ₀ is determined by the electrical length of the branch line 3 which is a resonator, and the amount of attenuation is determined by the variable attenuator 4. Further, by changing the variable attenuator, the characteristics can be changed as indicated by 11, 12, and 13 in FIG. When used as a primary slope amplitude equalizer, this slope portion is used.

FIG. 3 shows a variable amplitude equalizer according to a second embodiment of the present invention. In this circuit, the variable attenuator 4 in Figure 1
Instead, a diode-type variable attenuator 6 (using a PIN diode, for example) whose attenuation amount changes depending on the bias current is used. Capacitor 7 is for DC cut. In this case, even if the amplitude equalizer is built into the device, if the bias terminal is brought out externally, the advantage is that you can freely select characteristics with different attenuation amounts as shown in Figure 2 by simply changing the bias current. There is.

FIG. 4 shows a third embodiment in which the branch line 3 is grounded via a variable capacitance element 9 in the first embodiment shown in FIG. In this case, the amplitude equalizer can change the resonance frequency using the variable capacitance element 9 and the attenuation amount using the variable attenuator 4. Therefore, there is an advantage that the attenuation amount and resonance frequency can be freely selected.

FIG. 5 shows a variable capacitance diode 10 whose capacitance changes with a bias voltage as the variable capacitance element 9 in FIG.
This is the fourth embodiment using the above, and has a circuit configuration that can be controlled from the outside like the above.

FIG. 6 shows a fifth embodiment in which a diode-type variable attenuator 6 whose attenuation amount changes depending on the bias current is used in place of the variable attenuator 4 shown in FIG. 5, similar to the second embodiment shown in FIG. It is. This circuit is capable of changing the resonant frequency and the amount of attenuation by changing the bias voltage and current. Therefore, even if it is incorporated into a device, if the bias terminal is provided externally, the amplitude frequency characteristics can be freely changed just by changing the bias.

As explained above, the present invention can freely change the amplitude characteristics by combining a branch line that can be easily constructed with a microstrip line with a variable attenuator and a variable capacitance element, so that the amplitude characteristics can be easily adjusted. In particular, using these elements that use diodes has the advantage that they can be easily adjusted while installed in the device.

Further, although a non-reflection terminator is used in the above embodiment, a terminator that can attenuate the signal may be used.

Note that these amplitude compensation circuits can be easily constructed on a microstrip substrate, making it possible to reduce the size and weight.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a circuit configuration showing a first embodiment of the present invention, FIG. 2 is an amplitude frequency characteristic diagram for explaining the embodiment of FIG. 1, and FIG. 3 is a diagram showing a second embodiment of the present invention. An explanatory diagram of a circuit configuration showing an example, FIG. 4 is an explanatory diagram of a circuit configuration showing a third embodiment of the present invention, FIG. 5 is an explanatory diagram of a circuit configuration showing a fourth embodiment of the invention, and FIG. It is a circuit configuration explanatory diagram showing a fifth embodiment of the present invention. 1...Signal transmission line, 2...Reflection-free terminator, 3
...branch line which is a resonator, 4...variable attenuator,
5...Circuit for giving a transmission signal and taking out an output signal, 6...Diode-type variable attenuator whose attenuation changes with bias current, 7, 8...DC
Cutting capacitor, 9...Variable capacitance element, 10
...Variable capacitance diode, 11, 12, 13...
Amplitude characteristic curve, 14... Signal input terminal, 15...
Signal output terminal.

Claims (1)

[Claims for Utility Model Registration] (1) An amplitude compensation circuit having a first terminal and a second terminal connected to a terminator, and a signal which applies a transmission signal to the first terminal and whose amplitude has been compensated. from the first terminal, and the amplitude compensation circuit includes a signal transmission line coupled between the first and second terminals; an attenuator provided between the ground and a position separated by a length corresponding to a quarter wavelength of the center frequency of the transmission signal toward the second terminal side; and between the first position and the ground. a resonator having a branch line that transmits signals near the center frequency toward the attenuator and reflects signals away from the center frequency toward the first terminal. (2) The variable amplitude equalizer according to claim 1, wherein the resonator includes a variable capacitance element connected in series with the branch line.