JP2616812B2 - Wireless telephone equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION (Industrial Application Field) The present invention relates to a multi-channel switching wireless telephone device in which a master unit and a slave unit each search for an available channel and perform communication.

(Prior Art) FIG. 4 shows an example of a configuration of a receiving section of a conventional double superheterodyne type cordless telephone device.
In FIG. 4, 1, 3 and 7 are band-pass filters (BP
F), 2 is a high frequency amplifier (RF-AMP), 4 is a mixer (MI
X), 5 is an intermediate frequency amplifier (IF-AMP), 6 is an intermediate frequency detector (2nd-IF), 8 is a noise filter (N-FI)
L) and 9 are noise amplifiers (N-AMP), and 10 is a noise detector (N-DET), which constitutes a noise squelch circuit with N-FIL8, N-AMP9 and N-DET10.

Next, the operation of the above conventional example will be described. In FIG. 4, a desired frequency of a radio frequency signal received by an antenna (ANT) is selected by a BPF 1 and amplified by an RF-AMP 2. The amplified signal is band-limited by BPF3 and MIX4
Is input to In MIX4, the signal is mixed with the first local signal and converted to a first intermediate frequency. The converted signal is IF-AMP5
The amplified signal is input to the 2nd-IF 6, converted to a second intermediate frequency, passed through the BPF 7, and converted to an audio signal.

The noise squelch circuit is a circuit that detects the presence or absence of a carrier based on the presence or absence of noise outside the demodulated audio signal band.
The intermediate frequency component is removed by the N-FIL 8 of the noise squelch circuit, and a high-frequency portion of noise between the voice band and the intermediate frequency band is extracted. The level of the extracted noise is low, and if it is detected as it is, a large fluctuation of the detector appears.
Amplified by about 20 to 40 dB by -AMP. The amplified noise is N
-Detected by DET10 and used as a carrier sense signal.

As a method of changing the detection level of the electric field intensity of the carrier sense signal, the amplification degree of N-AMP9 is changed,
By changing the threshold value of the N-DET 10, the detection level of the electric field strength of the carrier sense signal can be changed by the noise squelch circuit even in the above-described conventional wireless telephone device.

(Problems to be Solved by the Invention) However, in the above-described conventional noise squelch circuit of the wireless telephone device, as is apparent from FIG. 5, the noise level is saturated when the electric field intensity is increased to some extent. It cannot be identified. Also, considering the level margin of the voice lock or the like, there is a problem that the detection level of the electric field strength cannot be set to be too high with respect to the reception sensitivity of the wireless telephone device.

SUMMARY OF THE INVENTION An object of the present invention is to solve such a conventional problem, and an object of the present invention is to provide an excellent wireless telephone device capable of distinguishing from a strong electric field to a weak electric field only with a noise squelch circuit.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a circuit capable of switching a signal level between a receiving antenna and a demodulator (an amplification adjustment circuit or an attenuator for each amplifier). Circuit) to switch the receiving sensitivity of the wireless telephone device.

(Operation) Therefore, according to the present invention, the noise curve can be changed by switching the reception sensitivity of the wireless telephone device (FIG. 3), and the stable electric field intensity from weak electric field to strong electric field can be identified. This can be done by a squelch circuit.

(Embodiment) FIG. 1 shows a configuration of an embodiment of the present invention. In FIG. 1, 1, 3 and 7 are band-pass filters (B.
PF), 2 is a high frequency amplifier (RF-AMP), 4 is a mixer (MI
X), 5 is an intermediate frequency amplifier (IF-AMP), 6 is an intermediate frequency detector (2nd-IF), 8 is a noise filter (N-FI)
L) and 9 are noise amplifiers (N-AMP), 10 is a noise detector (N-DET), and 11 is an amplification degree adjuster. Each of the blocks 1 to 10 in FIG. 1 is a circuit having the same function as each of the blocks of the same number in the conventional example.

FIG. 1 shows the configuration of a receiving section of a cordless telephone apparatus of the double superheterodyne system, and identifies whether the RF-AMP2 is searching for a free channel or talking during a call from a control section (not shown) of the wireless telephone apparatus. RF-AMP2 depending on the signal
A switching circuit (GAIN-C11) for controlling the degree of amplification is different from the conventional example. Thus, according to the above embodiment, GAIN
-C11 lowers the amplification sensitivity at the time of searching for an empty channel in response to the control signal from the control unit as compared with that at the time of talking, so that the reception sensitivity of the cordless telephone at the time of searching for an empty channel decreases, as shown in FIG. As described above, the detection of the strong electric field can be performed by the noise squelch circuit.

FIG. 2 shows the configuration of another embodiment of the present invention. In FIG. 2, blocks 1 to 10 are circuits having the same functions as the corresponding numbers in FIG. 1, and 12 is an attenuator.

In this embodiment, a switching circuit (RF-AMP2 and BPF3) for attenuating a wireless signal by a control signal from a control unit (not shown) of the wireless telephone device for identifying whether a free channel is being searched or a call is in progress. An attenuator 12) is provided.
However, the same operation as that of the embodiment shown in FIG. 1 can be performed by lowering the reception sensitivity of the cordless telephone device at the time of searching for an available channel in response to the control signal as compared with that at the time of talking.

(Effects of the Invention) The present invention has the following effects, as is clear from the above-described embodiments. That is, the conventional wireless telephone circuit device uses different circuits for detecting a strong electric field and detecting a weak electric field, respectively. Since the noise squelch circuit and the switching circuit of the receiving sensitivity can stably detect the electric field strength, there is an effect that the circuit can be simplified and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a cordless telephone device of a double superheterodyne system according to an embodiment of the present invention;
FIG. 2 is a schematic block diagram of another embodiment of the present invention, FIG. 3 is a characteristic diagram of reception sensitivity and noise level, FIG. 4 is a schematic block diagram of a conventional double superheterodyne cordless telephone, and FIG. The figure is a characteristic diagram of a noise level and an input electric field strength of a demodulated audio signal of a conventional receiver. 1,3,7 ... bandpass filter, 2 ... high frequency amplifier,
4 ... Mixer, 5 ... Intermediate frequency amplifier, 6 ... Intermediate frequency detector, 8 ... Noise filter, 9 ... Noise amplifier, 10 ... Noise detector, 11 ... Amplification degree adjuster, 12 ...
Attenuator.

Claims (1)

(57) [Claims] A control unit for outputting a control signal for discriminating whether an idle channel is being searched or a call is being made, in a multi-channel switching wireless telephone device in which a master unit and a slave unit each search for an empty channel and perform communication. A switching circuit that switches reception sensitivity according to a control signal from the control unit, and a noise squelch circuit that detects an electric field strength based on the noise level of the demodulated audio signal, wherein the switching circuit controls the control signal from the control unit. A radio telephone apparatus characterized in that the reception sensitivity at the time of searching for an available channel is made lower than that at the time of talking, and the electric field detection level of the noise squelch circuit is switched between at the time of searching for an available channel and at the time of talking.