JPS6112139A - Base band signal synthesizer - Google Patents

Abstract

PURPOSE:To prevent malfunction of a pilot alarm by providing a resonance circuit resonated in a pilot frequency to a base band signal synthesizer connected to plural pilot signal detectors to prevent the detour of a pilot signal. CONSTITUTION:A series resonance circuit 6 resonated in the frequency of a pilot signal inputted from input terminals (a), (b) is provided between a base band signal synthesis circuit 1 and an LPF2 of a base band signal synthesizer 5 connected to pilot signal detectors 3, 4 and in which a reception signal is synthesized in the base band zone. The pilot signal inputted from the terminal (a), (b) is sbsorbed by a resonance circuit 6 and not reflected by the LPF2, then the signal is not by-passed to other pilot signal detector and malfunction of the pilot alarm is prevented surely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a receiver for a transmitting/receiving device, and particularly to an improvement in a baseband signal synthesizer used in connection with a pilot signal detector.

[Prior art]

When the received signals are combined by the baseband signal combiner of the receiver of the transmitter/receiver, a problem arises in that the pilot signal from one pilot signal detector leaks into the other pilot signal detector, causing a malfunction of the pilot alarm. are doing. The details will be explained below.

Conventionally, a baseband signal synthesizer used in connection with this type of pilot signal detector has to be configured with passive circuit elements after detecting the pilot signal.
The configuration was as shown in the figure. Here, normally the input terminal a
The baseband signal S1 inputted from the input terminal and the baseband signal Sz inputted from the input terminal are combined by a baseband signal synthesis circuit 1, and a low-pass filter 2 for pilot signal removal and out-of-band noise removal is combined. It is output to output terminal C. Here, the pilot signal detector 8 has terminal d terminated with 75Ω, inputs the pilot signal from input terminal a, and is set to send out an alarm signal when the pilot signal falls to a certain level from the normal level. . Note that the same applies to the pilot signal detector 4. here,
Baseband signal combiner 5 and pilot signal detector 8.
4 are connected as shown in FIG. 1, and a pimit signal spI is input from the input terminal a, and a pilot signal Sp is input from the input terminal a, the pilot signal Spt is input to each terminal.

The signal is sent to the low-pass filter 2 via e, f, and g. Here, when the impedance of the frequency portion of the pilot signal of the low-pass filter 2 is in an oven state, the pilot signal sp undergoes total reflection and goes around to the pilot signal detector 8 via terminals g, f, and d.

Therefore, the pilot signal detector 8 detects the pilot signal S
p1 and the looped pilot signal Sp2 are detected simultaneously. That is, even if the level of the pilot signal Sp inputted from the input terminal a is lowered from the normal level, the pilot alarm signal is not sent out, resulting in a malfunction of the pilot alarm. Note that the pilot signal Spl
The same applies to the fact that the signal goes around to the pilot signal detector board.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a baseband signal synthesizer that can reliably prevent pilot alarm malfunctions by eliminating the above drawbacks and preventing pilot signals from looping around.

[Structure of the invention]

In order to achieve the above object, a baseband signal synthesizer according to the present invention includes a resonant circuit consisting of a coil, a capacitor, a resistor, etc., and makes the resonant frequency of the resonant circuit equal to the frequency of an input pilot signal. This setting prevents the pilot signal from going around to the input side.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

An embodiment of the present invention is shown in FIG. In this case, a series resonant circuit 6 consisting of a coil L, a capacitor C, and a resistor R is provided between the baseband signal synthesis circuit 1 and the low-pass filter 2 shown in FIG. Here, the resonant frequency of the resonant circuit 6 is equal to the frequency of the pilot signals input from the input terminals a and b. d terminal and C in Figure 1
Whereas the impedance of the pilot signal frequency portion from the terminal to the C terminal is in an open state, in this embodiment, the impedance of the pilot signal frequency portion from the d terminal and the C terminal to the C terminal is in a shorted state.

Here, in FIG. 2, the pilot signal S is input from the input terminal a.
When inputting p1 and pilot signal Sp2 from the input terminal, pilot signal 8pt is input to each terminal.
It is sent out via e f * g and absorbed at point n. Therefore, no pilot signal component is reflected by the low-pass filter 2 as described in FIG. The same applies to the case where the pilot signal CI)t is input from the input terminal a.

Therefore, the pilot signal input from one pilot signal detector is absorbed by the resonant circuit 6 and is not reflected by the low-pass filter 2, so that it is not passed around to the other pilot signal detector. It disappears.

〔Effect of the invention〕

From the above, if the baseband signal combiner according to the present invention is used, the pilot signal of one pilot signal detector will not go around to the other pilot signal detector, so there will be no influence from other pilot signals. , the pilot alarm point can be set using only the original pilot signal, and erroneous operation of the pilot alarm can be reliably prevented.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional example, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. 1...Baseband signal synthesis circuit. 2...Low pass filter. 8.4...Pilot signal detector. 5...Baseband signal synthesizer. 6...Resonant circuit.

Claims (1)

[Claims] A resonant circuit whose resonant frequency is the frequency of the pilot signal in a baseband signal synthesizer that is connected to a plurality of pilot signal detectors that detect pilot signals in the baseband band and synthesizes received signals in the baseband band. A baseband signal synthesizer characterized by comprising: