Hot stand-by transmitter switching apparatus

Abstract: To provide a hot stand-by switching apparatus which is cheaper and more reliable than a conventional RF power switching device. Further, Output level and frequencies during rise and fall times are stabilized. The hot stand-by apparatus of the present invention comprises coupler for outputting either the active signal or the preparative signal, active and preparative transmitters, and switches which are connected with the input terminals of transmitters, respectively.

Description: BACKGROUND OF THE INVENTION 1 Technical Field of the Invention The present invention relates to a hot stand-by switching apparatus which comprises a signal output means for outputting an active signal, or a preparative signal, and switches connected with the input terminals of an active transmitter and a preparative transmitter, respectively. 2 Description of the Prior Art Conventionally, switching means for replacing an active power amplifier by an preparative power amplifier are connected with the output terminals of these amplifiers, as disclosed, for example, in JP 9-331275 A (1997). Further, one of the conventional hot stand-by switching apparatus as disclosed in JP 3-270515 A (1991) comprises a directional coupler, wherein local oscillators, power sources for the local oscillators, and variable attenuators for transmitters are controlled. However, the switching devices for RF power are expensive. Further, the conventional hot-stand-by switching apparatuses as mentioned above are poor in reliability, because only one switching device is employed commonly for both of the active and preparative circuits. Furthermore, the time required for switching becomes long and the switching control becomes complicated, because sequential controls for stabilization are required, when stability at the times of rise-up and fall-down in frequency and output level of the above-mentioned oscillators and variable attenuators is not sufficiently high. PATENT ABSTRACTS OF JAPAN, Vol. 015 no. 143, 11 April 1991 & JP 03 019530 discloses a transmission switching system for hot standby system. It is intended to reduce the forword insertion loss by tuming off an intermediate frequency switch of the other system, or a local oscillation switch and radio frequency switch and interrupting the output of the transmitter of the other system when a selection circulator selects the output of one system of a transmitter of the two systems. PATENT ABSTRACTS OF JAPAN, Vol. 1999, no. 13, 30 November 1999 & JP 11 239063 discloses a hot standby radio equipment for monitoring the normal state of an equipment in standby mode by monitoring the operation state of a transmission unit in standby operation by using the output voltage of a detecting means and suppressing the signal from the transmission unit in standby operation below a prescribed value by using a bandpass filter. PATENT ABSTRACTS OF JAPAN, Vol. 007, No. 107, 11 May 1983 & JP 58 029228 discloses a hot standby relay system for reducing the power consumption of a standby side by applying class "C" biasing to power amplifiers of an in-use and a standby system, and intermitting an input signal through a switch provided in series to the signal path of each system and thus performing in-use/standby switching. PATENT ABSTRACTS OF JAPAN, Vol. 1998, No. 04, 31 March 1998 JP 09 331275 discloses a radio equipment capable of controlling transmission output by adopting a hot standby system. It is intended to simplify the circuit configuration and control algorithm of radio equipment by combining control systems into one system by only supplying the control signal of an output control board to the transmitter of an operated system. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a hot stand-by switching apparatus which utilizes cheaper switching devices for high power RF signal. Further, another object of the present invention is to provide a hot stand-by switching apparatus which stabilizes the frequency and the output level at the rise and fall times. The hot stand-by switching apparatus of the present invention is defined in claim 1. The dependent claims define particular embodiments. In short, the hot stand-by switching apparatus of an embodiment of the present invention comprises a signal output means for outputting an active signal, or a preparative signal, and switches connected with the input terminals of an active transmitter and a preparative transmitter, respectively. According to an embodiment of the present invention, the hot stand-by switching apparatus is cheap and reliable, because a passive device such as a coupler or a directional coupler is employed as a switching means for turning off the active side and turning on the preparative side. Further, the switcing device is cheaper and more reliable than the RF power switch, because the switching is executed in an intermediate frequency range. Further, according to an embodiment of the present invention, the rise time and fall time for switching become shorter than in the conventional case wherein the oscillator or variable attenuator is controlled. Furthermore, any sequential control is not required at all, because the stability in frequency or output level is not irrelevant at all. BRIEF EXPLANATION OF THE DRAWINGS Figure 1 is a block diagram of the hot stand-by switching apparatus of the present invention. Figure 2 is a time chart for explaining the operation of the hot stand-by switching apparatus of the present invention. Figure 3 is a block diagram of the hot stand-by switching apparatus of the present invention which can detect a fall down in the output level in the active transmitter. Figure 4 is a block diagram of the hot stand-by switching apparatus of the present invention which is provided with a directional coupler. Figure 5 is a block diagram of the hot stand-by switching apparatus of the present invention wherein antennas are connected with the active and preparative transmitters. PREFERRED EMBODIMENT OF THE INVENTION Preferred embodiment of the present invention is explained, referring to the drawings. A block diagram of the hot stand-by switching apparatus of the present invention is shown in Figure 1. As shown in Figure 1, the input signal is branched into two signals by distributor (HYB) 1. One of the branched signals is modulated by modulator 2, is inputted into switch (SW) 4, and amplified by transmitter 6, while another branched signal is modulated by modulator 3, is inputted into switch (SW) 5, and amplified by transmitter 7. Further, the outputs from transmitters 6 and 7 are inputted into coupler (HYB) 9 which is connected with antenna 10. Controller (CONT) 8 controls SW 4 and SW 5 on the basis of the outputs from modulators 2 and 3 and transmitters 6 and 7. A time chart for explaining the operation of the hot stand-by switching apparatus of the present invention is illustrated in Figure 2. It is assumed that the active circuit comprises modulator 2, SW 4, and transmitter 6, while the preparative circuit comprises modulator 3, SW 5, and transmitter 7. When modulator 2 malfunctions, the normal state (NORM) of malfunction status information inputted into CONT 8 is changed into the alarm state (ALM). Then, CON 8 knows a trouble in modulator 2, ouutputs a control signals for switching off SW 4 and switching on SW 5. According to these control signals, the active transmitter 6 is switched off, while the preparative transmitter 7 is switched on. In place of the modulator status, the information that indicate the fall down in the output level of the active transmitter 6 may be inputted into CONT 8. As shown in Figure 3, two kinds of signals from transmitters 6 and 7 may be inputted into masks 12 and 13, respectively. One of the two kinds of signals is to indicate the fall down in the output level of transmitter 6, or 7, while the other is to indicate any other malfunction excluding the fall down in the output level. Mask 12 relays to determination means 14 a signal which indicates that the output level of the transmitter 6 falls down, while mask 13 relays also to determination means 14 a signal which indicates that the output level of the transmitter 7 falls down. Coupler (HYB) 9 may be replaced by directional coupler. As shown in Figure 4, directional coupler (DC) 9 connected with antenna 10 may has, for example, 0 dB port for the active side and 10 dB port in order to give the active side a priority over the preparative side. In this case, the active transmitter is higher than the preparative transmitter. Further, transmitters 6 and 7 may be connected with antennas 10 and 11, respectively. The outputs from both of transmitters 6 and 7 are radiated from antennas 10 and 11, respectively. Therefore, the intensity levels of transmitted waves become high. An embodiment of the invention can be summarized as follows. To provide a hot stand-by switching apparatus which is cheaper and more reliable than a conventional RF power switching device. Further, output level and frequencies during rise and fall times are stabilized. The hot stand-by apparatus of the present invention comprises coupler for outputting either the active signal or the preparative signal, active and preparative transmitters, and switches which are connected with the input terminals of transmitters, respectively.

Claims: A hot stand-by switching apparatus which comprises: a first transmitting means (2, 4, 6) including a first modulator (2), a first switch (4) for turning on and off the output from said first modulator (2), and a first transmitter (6) for amplifying the output from said first switch (4); a second transmitting means (3, 5, 7) including a second modulator (3), a second switch (5) for turning on and off the output from said second modulators (3), and a second transmitter (7) for amplifying the output from said second switch (5); a distributor (1) for distributing an input signal to said first and second modulators (2, 3); and a controller (8) which is connected to said first and second switches (4, 5) in order to control said first and second switches (4, 5), characterized in that said controller (8) is connected to said first modulator (2), said first transmitter (6), said second modulator (3) and said second transmitter (7) in order to detect malfunctions thereof, and said controller (8) selects an output from said second transmitting means (3, 5, 7) as an output of the hot stand-by switching apparatus by switching on said second switch (5) and switching off said first switch (4), when at least one of said first modulator (2) and said first transmitter (6) malfunctions, while said controller (8) selects an output from said first transmitting means (2, 4, 6) as the output of the hot stand-by switching apparatus by switching on said first switch (4) and switching off said second switch (5), when at least one of said second modulator (3) and said second transmitter (7) malfunctions. The hot stand-by switching apparatus according to Claim 1, which further comprises a coupler (9) for coupling the outputs from said first and second transmitters. The hot stand-by switching apparatus according to Claim 2, wherein said coupler (9) is a directional coupler. The hot stand-by switching apparatus according to Claim 1, which further comprises a first antenna (10) for propagating the output from said first transmitter, and a second antenna (11) for propagating the output from said second transmitter. The hot stand-by switching apparatus according to Claim 1, wherein said controller (8) further comprises a first mask (12) for relaying a signal indicating a fall-down in the output level of said first transmitter (6), a second mask (13) for relaying a signal indicating a fall-down in the output level of said second transmitter (7), and a determination means (14) for generating control signals for controlling said first and second switches on the basis of the outputs from said first and second masks in order to select either said first transmitter, or said second transmitter.

Inventors: NORO ATSUSHI, NORO, ATSUSHI, Noro, Atsushi, c/o NEC Fukushima, Ltd.
Applicants: NIPPON ELECTRIC CO, NEC CORPORATION
Application year: 1999
Main classification: H04B1
IPC codes: H04B1, H04L29