KR20050101064A - Time diversity method and system - Google Patents

Abstract

The present invention relates to a time diversity technique for improving call quality of service coverage in a mobile communication transmission and reception system. The present invention includes a main path gain correction and path selector for terminating or gaining a signal received through a main antenna and terminating or gaining a time delayed signal by receiving a time delayed signal received through a diversity antenna. Diversity path gain correction and path selector for adjustment, combiner for combining outputs of gain correction and path selector, gain detector for monitoring the combined signal to detect gain of selected path, diversity path gain in adjustment period And a controller for controlling the main path gain correction and path selection unit so as to terminate the diversity path by controlling the correction and path selection unit, and compare the gain of the detection signal received from the gain detection unit with the reference gain. Therefore, the present invention automatically compensates for gain imbalance that may occur in each path (main path, diversity path) according to the change of the internal and external environment of the transmitter and receiver, thereby minimizing the gain difference of each path. In addition, by monitoring the gain difference, an abnormal state of the path can be monitored.

Description

Time Diversity Method And System

The present invention relates to a diversity system of a wireless transceiver, and more particularly, to a time diversity method and system capable of improving reception characteristics in a fading environment by combining signals of two paths with the same gain.

Currently, there are many cases of using a repeater for coverage extension and handoff of shadow area in CDMA mobile communication. The repeater receives the weak signal transmitted from the base station through the base station counter antenna and transmits the signal to the appropriate output within the service coverage through the filter process to increase the desired band selectivity, and similarly receives the signal of the mobile station through the mobile station counter antenna. It passes through the process to the base station with the proper output. At this time, the call quality within the repeater coverage is very sensitive to the installation location and the surrounding environment. Generally, the installation location is not located at the line of sight (LOS) of the base station antenna or the base station, the repeater, and the repeater. When a mobile object or a radio wave obstacle exists between mobile stations, signals are received through various paths, and attenuation of the received signal occurs due to the phase difference between the signals received at the base station and the mobile station. This phenomenon is called 'multipath fading'.

In general, various techniques such as frequency diversity, spatial diversity, and time diversity are used as a method for reducing the call quality deterioration due to fading. A representative method is a time diversity method.

As shown in FIG. 1, a mobile communication system to which time diversity is applied includes a base station 10 connected to the mobile communication network 1, a repeater 20 for eliminating a shadow area, and a mobile station 30. At this time, the repeater 20 divides each of the two receiving paths into two in order to use a rake receiver having a demodulation function of a multipath signal according to a time delay in the system of the base station 10 and the mobile station 30. After using a time-delay element in one path, the signals of the two paths are combined to give a certain time difference in both paths.

As shown in FIG. 2, the time diversity system applied to the conventional repeater 20 amplifies a forward signal received from the base station 10 and transmits it through the main antenna 29-1 on the mobile station side. And a forward diversity path for delaying the signal received from the base station 10 through the diversity antenna 21-2 and transmitting it to the forward main path to improve the gain of the forward path, and received from the mobile station 30. Delaying the signal received through the diversity antenna 29-2 from the mobile station 30 to improve the gain of the reverse path and amplifying the reverse signal to the base station side antenna 21-1. It consists of a reverse diversity path that provides the reverse main path.

Referring to FIG. 2, the mobile station signal received from the main antenna 29-1 using two mobile station opposing antennas passes through a signal processor 25R for high selectivity through low noise amplification and a filter, and then a high power amplifier 26R. Amplified to the appropriate output from the radiation to the base station opposing main antenna (21-1) and transmitted to the base station (10). The mobile station signal received from the diversity antenna 29-2 is passed through an element 28M which delays a predetermined time (a few chips) after low noise amplification, and has the same gain as the signal received from the main antenna 29-1. After summed at 24R and passing through the signal processing unit 25R, the high output amplifier 26R amplifies to a proper output, radiates it to the base station counter antenna 21-1, and demodulates a multipath signal to the rake receiver of the base station 10. Improve call quality.

Since the process of transmitting the signal from the base station 10 to the mobile station 30 through the repeater 20 is also implemented in the same manner as described above, further description thereof will be omitted.

However, in the conventional diversity system described above, a gain imbalance occurs between a main path through which a signal received through the main antenna is transmitted, and a time delay path through which a signal delayed after being received through the diversity antenna is transmitted. There is a problem that is lowered. In other words, the time diversity method is best when the combination of two paths is combined with the same gain, so that a diversity effect of 3 dB improvement in reception sensitivity can be obtained. Will fall.

This gain imbalance can also be caused by system internal factors, such as operator inadvertence and changes in part gain with temperature, and by the external environment. In the conventional time diversity method, there is no active gain compensation device. There is a problem in that it is not possible to maximize the effect, and that service can be performed using only one of the two paths, so that significant gain deterioration of the remaining paths cannot be properly monitored.

An object of the present invention is to provide a time diversity method and system that can maximize the diversity effect by correcting the gains of two paths of a receiving end to combine the same gain in order to solve the above problems. .

Another object of the present invention is to provide a time diversity that can improve performance by correcting a case where a gain is changed due to a component inside the system due to a temperature change or other causes inside the system or due to a propagation environment. It is to provide a method and system.

Another object of the present invention is to provide a repeater of a mobile communication system that can increase the reliability of call quality in coverage and improve diversity performance by simultaneously monitoring the state of two paths.

The present invention can be directly applied to all systems using the same gain coupled diversity scheme among CDMA and IMT-2000 repeaters and transmitters and receivers currently being serviced.

In order to achieve the above object, the method of the present invention, in the time diversity method for increasing the immunity to fading by combining the main path and the diversity path of the radio transceiver with the same gain, to set the reference gain step; Detecting a gain of the main path and comparing the gain with the reference gain; Adjusting the gain of the main path such that the gain of the main path matches the reference gain; Detecting a gain of the diversity path and comparing the gain with the reference gain; Adjusting the gain of the diversity path such that the gain of the diversity path matches the reference gain; And combining and transmitting the signal of the main path and the signal of the diversity path with the adjusted gain.

In addition, in order to achieve the above objects, the system of the present invention synthesizes the main path and the diversity path of the radio transceiver with the same gain in the time diversity system for strengthening immunity to fading, received through the main antenna Main path gain correction and path selection means for terminating or gain-adjusting the received signal; Diversity path gain correction and path selection means for terminating or gain-adjusting the time-delayed signal received through a diversity antenna and receiving a predetermined time-delayed signal; A combiner for combining the outputs of the gain correction and path selection means; Gain detection means for monitoring the combined signal to detect gain of a selected path; The predetermined reference gain is stored, and the diversity path gain correction and path selection means are terminated at an adjustment period to terminate the diversity path, and the gain of the detection signal received from the gain detection means is compared with the reference gain. The main path gain correction and path selection means are controlled to coincide with each other, the main path gain correction and path selection means are controlled to terminate the main path, and the gain of the detection signal received from the gain detection means is equal to the reference gain. And a controller for controlling the diversity path gain correction and path selection means so as to coincide with each other.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, a mobile communication system to which time diversity is applied according to the present invention is connected to a mobile communication network 1 and provides a service signal to a corresponding cell through a plurality of antennas 12-1 to 12 -N. The base station 10, the repeater 200 for eliminating the shadow area, and the mobile station 30 may be made. The repeater 200 to which the present invention is applied includes a main antenna 21-1 for transmitting and receiving a service signal to a base station, a diversity antenna 21-2 for receiving a service signal from a base station, and a service signal to a mobile station. The main antenna 29-1 for performing the operation and the diversity antenna 29-2 for receiving the service signal from the mobile station side are relayed.

3 is a block diagram showing a configuration of a repeater to which time diversity is applied according to the present invention. The repeater 200 according to the present invention amplifies a forward signal received from the main antenna 21-1 toward the base station 10. The forward main path F transmitted through the main antenna 29-1 in the direction of the mobile station 30, and the signal received through the base station direction diversity antenna 21-2 in order to improve the gain of the forward path are predetermined. The base station direction antenna 21 is amplified by a forward diversity path B that is delayed in time (for example, several chips) and transmitted to the forward main path F, and a reverse signal received from the mobile station direction antenna 29-1. Reverse path (R) to transmit to -1) and reverse diversity to provide a reverse main path by delaying a signal received through the mobile station direction diversity antenna 29-2 in order to improve the gain of the reverse path. Consisting of paths (M) .

The forward path F includes a duplexer 22B for separating transmission and reception signals of the base antenna 21-1, a low noise amplifier (LNA) 23F, a gain compensation and path selection unit 32F, and a combiner 24F. And a forward signal processor (25F) and a high power amplifier (HPA) 26F, the reverse path (R) is a duplexer (22M) for separating transmission and reception signals of the main antenna (29-1) in the mobile station, and a low noise amplifier ( 23R), gain correction and path selection section 32R, combiner 24R, reverse signal processing section 25R, and high output amplifier 26R.

The forward diversity path B is composed of a base station direction diversity antenna 21-2, a reception filter 27B, a low noise amplifier 23B, a delayer 28B, a gain correction and a path selector 32B, The reverse diversity path (M) is composed of a mobile station direction diversity antenna (29-1), a reception filter (27M), a low noise amplifier (23M), a delay (28M), a gain correction, and a path selector (32M). . Here, the delay units 28B and 28M are time delay elements for delaying a predetermined time and usually delay several chips.

Referring to FIG. 3, the forward high frequency signal received from the base antenna 21-1 is transferred from the duplexer 22B to the forward path, amplified by the low noise amplifier 23F, and the gain correction and path selector 32F. By the gain is corrected and passed to the combiner 24F. In addition, the forward high frequency signal received by the base station direction diversity antenna 21-2 is filtered by the reception filter 27B and then amplified by the low noise amplifier 23B and delayed by the delay unit 28B. The gain is corrected at 32B and passed to combiner 24F. The combiner 24F combines the two forward signals with the same gain and transfers them to the forward signal processor 25F. The combined signal filtered by the forward signal processor 25F is amplified with high gain in the high output amplifier 26F and then duplexer ( 22M) from the main antenna 29-1 toward the mobile station to the service area. Therefore, the rake receiver of the mobile station 30 can demodulate the signal of the multipath to improve the call quality.

The reverse high frequency signal received from the mobile station direction antenna 29-1 is transferred from the duplexer 22M to the reverse path, amplified by the low noise amplifier 23R, and the gain is corrected by the gain correction and path selection unit 32R. And then to a combiner 24R. In addition, the reverse high frequency signal received by the mobile station direction diversity antenna 29-2 is filtered by the reception filter 27M and then amplified by the low noise amplifier 23M and delayed by the delay unit 28M, followed by a gain correction and path selector ( The gain is corrected at 32M) and passed to combiner 24R. The combiner 24R combines the two reverse signals with the same gain and transfers them to the reverse signal processor 25R. The combined signal filtered by the reverse signal processor 25R is amplified with high gain in the high output amplifier 26R and then duplexer ( Radiates from the base station direction main antenna 21-1 to the base station side via 22B). Therefore, it is possible to demodulate the signal of the multipath to the rake receiver of the base station 10 to improve the call quality.

Meanwhile, in the diversity system according to the present invention, when combining two signals, a gain correction and path selector 32F for selecting the corresponding path and adjusting the gain of the corresponding path to combine the signals of both paths with the same gain. 32R, 32B, 32M, gain detectors 34F, 34R for detecting the gain of the selected path, and a controller 30 for executing the gain adjustment algorithm.

As shown in Fig. 4, the gain detectors 34F and 34R include an amplifier 41 for monitoring and amplifying high frequency signals in each path, a band pass filter 42, and a synthesizer 43 for generating a predetermined frequency. Composed of a mixer 44, an intermediate frequency amplifier 45, a band pass filter 46, and a detector 47 for mixing the monitored high frequency signal with the output of the synthesizer 43 and converting it into an intermediate frequency (IF) signal. Output a signal for detecting the gain of the monitored signal of the selected path.

The gain correction and path selection units 32F, 32R, 32B, and 32M are RF switches 52 for terminating or connecting the corresponding paths according to the path selection signal CS1 of the controller 30, as shown in FIG. And a gain adjusting unit 54 for adjusting the gain of the corresponding path in accordance with the gain control signal CS2 of the controller 30. The RF switch 52 has a 50 ohm termination resistor for terminating a signal of a corresponding path, and the gain adjusting unit 54 may be implemented as a variable step attenuator.

In the diversity system of the present invention configured as described above, a procedure of adjusting gain by the controller will be described with reference to FIG. 6.

First, the diversity system according to the present invention sets a reference gain when the system is initially set up, and adjusts the gain of the two paths according to the reference gain, or the gain of one of the two paths (normally, the main path). It is possible to adapt the gain of another path (eg, a diversity path) to one path as a reference.

Referring to FIG. 6, reference gain is set at system initialization (601, 602). When the gain adjustment period is reached, the controller 30 selects one of two reception paths at the base station using the path selection signal CS1 (603, 604). Next, the gain of the selected path is detected by the gain detector 34F, and the detected gain is compared with a preset reference gain (605 and 606).

If the detected gain and reference gain do not coincide within the error range as a result of the comparison, the gain compensation signal paths 32F and 32B are controlled using the gain control signal CS2 so that the gain of the corresponding path becomes the reference gain ( 607,608). After the gain adjustment, the gain adjustment process is repeated while checking whether the gain of the corresponding path matches the reference gain (608).

If the detected gain and the reference gain coincide within the error range, another path is selected and the process is repeated. When the base station side adjustment is completed, the mobile station side performs the adjustment process (609, 610).

The controller 30 selects one of the two reception paths on the mobile station side using the path selection signal CS1 (611). Next, the gain of the selected path is detected by the gain detector 34R, and the detected gain is compared with a preset reference gain (612 and 613).

If the gain and the reference gain detected as a result of the comparison do not coincide within the error range, the gain compensation signal paths 32R and 32M are controlled using the gain control signal CS2 so that the gain of the corresponding path becomes the reference gain ( 614,615). After the gain adjustment, the gain adjustment process is repeated, checking whether the gain of the corresponding path is consistent with the reference gain (615).

If the detected gain and the reference gain coincide within the error range, another path is selected and the process is repeated. When the entire adjustment is completed, the process waits until the next adjustment period (616, 617).

In the above description, the adjustment period can be arbitrarily set according to the situation. In general, the adjustment period is preferably performed while the channel is idle, and the path on the base station side is adjusted first, but it can also be adjusted from the mobile station side. In the case where the gain of one of the two paths is used as a reference, the gain of the reference path is compared with the gain of the other path by comparing the gain of the reference path in the adjusting process, and then adjusted to coincide with each other. In addition, during the calibration process, it is possible to monitor a path requiring correction above a certain correction value.

7 is a block diagram of a repeater according to another embodiment of the present invention, in which the monitoring signal of the gain detection unit is detected at the output terminals of the combiners 24F and 24R. Since the configuration of the other embodiment is different only from the detection position of the monitoring signal, the overall configuration and operation are the same, and thus the detailed description thereof will be omitted. Although not shown in the drawing, the monitoring signal of the gain detection unit may be detected at the output terminal of the forward or reverse signal processors 25F and 25R.

8 is a block diagram illustrating a repeater according to another embodiment of the present invention, in which a monitoring signal of a gain detection unit is detected at an output terminal of each gain correction and path selection unit 32F, 32R, 32B, and 32M. Since the configuration of the other embodiment is different only from the detection position of the monitoring signal, the overall configuration and operation are the same, and thus the detailed description thereof will be omitted.

As described above, the present invention can continuously improve the reliability and the call quality of the system by correcting the gains of the two paths in the same gain combining diversity method in real time, and the diversity function by the corrected gain value. You can monitor the degradation of performance.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the present invention without departing from the spirit and scope of the invention described in the claims below. I can understand that you can.

1 is a schematic diagram of a general repeater system implemented with a diversity function,

2 is a block diagram illustrating a conventional repeater in which a diversity function is implemented;

3 is a block diagram illustrating a repeater in which time diversity is implemented according to the present invention;

4 is a block diagram illustrating a detailed configuration of a gain detector shown in FIG. 3;

5 is a detailed block diagram of the gain correction and path selection unit shown in FIG. 3;

6 is a flowchart illustrating a control algorithm of a repeater according to the present invention;

7 is a block diagram illustrating a repeater according to another embodiment of the present invention;

8 is a block diagram of a repeater according to another embodiment of the present invention.

* Brief description of symbols for the main parts of the drawing

20,200 repeater 21-1,29-1

21-2, 29-2: diversity antenna 22B, 22M: duplexer

23F, 23R, 23B, 23M: low noise amplifier 24F, 24R: coupler

25F, 25R: Signal Processing Unit 26F, 26R: High Power Amplifier

32F, 32R, 32B, 32M: gain compensation and path selector 34F, 34R: gain detector

27B, 27M: Receive filter 28B, 28M: Delay

Claims (9)

In the time diversity method for enhancing the immunity to fading by combining the main path and the diversity path of the radio transceiver with the same gain, Setting a reference gain; Detecting a gain of the main path and comparing the gain with the reference gain; Adjusting the gain of the main path such that the gain of the main path matches the reference gain; Detecting a gain of the diversity path and comparing the gain with the reference gain; Adjusting the gain of the diversity path such that the gain of the diversity path matches the reference gain; And And combining and transmitting a signal of a main path and a signal of a diversity path with the adjusted gain. In the time diversity method for enhancing the immunity to fading by combining the main path and the diversity path of the radio transceiver with the same gain, Determining a reference path; Detecting a gain of the reference path and storing the gain of the reference path as a reference gain; Detecting gain of another path and comparing the gain of the reference path with the gain of the reference path; Adjusting the gain of the other path so that the gain of the other path matches the gain of the reference path; And And combining and transmitting a signal of a main path and a signal of a diversity path with the adjusted gain. A time diversity method for strengthening immunity to fading by synthesizing a main path and a diversity path of a repeater for transmitting a signal of a base station to a mobile station and a signal of the mobile station to a base station with equal gain, Setting a reference gain; Detecting a gain of the main path of the base station and comparing the gain with the reference gain; Adjusting a gain of the base station side main path such that the gain of the base station side main path coincides with the reference gain; Detecting a gain of the base station-side diversity path and comparing the gain with the reference gain; Adjusting a gain of the base station-side diversity path such that the gain of the base station-side diversity path matches the reference gain; Combining a signal of a base station side main path and a base station side diversity path with the adjusted gain and transmitting it to a mobile station; Detecting and comparing a gain of a mobile station main path with the reference gain; Adjusting a gain of the mobile station main path such that the gain of the mobile station main path matches the reference gain; Detecting a gain of the mobile station side diversity path and comparing the gain with the reference gain; Adjusting the gain of the mobile station side diversity path such that the gain of the mobile station side diversity path matches the reference gain; And combining the signal of the main path of the mobile station and the signal of the diversity path with the adjusted gain, and transmitting the combined signal to the base station. In the time diversity system for combining the main path and the diversity path of the radio transceiver with the same gain to enhance the immunity to fading, Main path gain correction and path selection means for receiving the signal received through the main antenna and terminating or adjusting the gain; Diversity path gain correction and path selection means for terminating or gain-adjusting the time-delayed signal received through a diversity antenna and receiving a predetermined time-delayed signal; A combiner for combining the outputs of the gain correction and path selection means; Gain detection means for monitoring the combined signal to detect gain of a selected path; The predetermined reference gain is stored, and the diversity path gain correction and path selection means are terminated at an adjustment period to terminate the diversity path, and the gain of the detection signal received from the gain detection means is compared with the reference gain. The main path gain correction and path selection means are controlled to coincide with each other, the main path gain correction and path selection means are controlled to terminate the main path, and the gain of the detection signal received from the gain detection means is equal to the reference gain. And a controller for controlling said diversity path gain correction and path selection means so as to coincide with each other. In the time diversity system for combining the main path and the diversity path of the radio transceiver with the same gain to enhance the immunity to fading, Main path gain correction and path selection means for receiving the signal received through the main antenna and terminating or adjusting the gain; Diversity path gain correction and path selection means for terminating or gain-adjusting the time-delayed signal received through a diversity antenna and receiving a predetermined time-delayed signal; A combiner for combining the outputs of the gain correction and path selection means; Gain detection means for monitoring the combined signal to detect gain of a selected path; The diversity path gain correction and path selection means are controlled at an adjustment period to terminate the diversity path, and the gain of the detection signal received from the gain detection means is stored as a reference gain of the main path, and the main path gain correction and Controlling the path selection means to terminate the main path, and comparing the gain of the detection signal received from the gain detection means with the reference gain of the stored main path to control the diversity path gain correction and path selection means A time diversity system of a wireless transmitting and receiving device, comprising a controller. A time diversity system for strengthening immunity to fading by synthesizing a main path and a diversity path of a repeater for transmitting a signal of a base station to a mobile station and a signal of the mobile station to a base station with equal gain, A forward main path gain correction and path selecting means for receiving the signal received through the base antenna side antenna and terminating or gain adjustment; Forward diversity path gain correction and path selection means for terminating or gain-adjusting the time-delayed signal received through a base station-side diversity antenna and receiving a predetermined time-delayed signal; A forward coupler for coupling the outputs of said forward gain correction and path selection means; Forward gain detection means for monitoring the combined signal to detect gain of a selected path; Reverse main path gain correction and path selection means for receiving the signal received through the mobile station side antenna and terminating or gain adjustment; Reverse diversity path gain correction and path selection means for terminating or gain-adjusting the time delayed signal received through the mobile station side diversity antenna and receiving a predetermined time delayed signal; A reverse coupler for coupling the outputs of the reverse gain correction and path selection means; Reverse gain detection means for monitoring the combined signal to detect gain of a selected path; The reference gain is stored, and then the forward diversity path gain correction and path selection means is terminated at an adjustment period to terminate the forward diversity path, and the gain of the detection signal received from the forward gain detection means is used as the reference gain. And controlling the forward main path gain correction and path selection means to match each other, and controlling the forward main path gain correction and path selection means to terminate the forward main path, and the detection signal received from the forward gain detection means. Controlling the forward diversity path gain correction and path selection means to compare the gain of the reference gain with the reference gain, Controlling the reverse diversity path gain correction and path selection means to terminate the reverse diversity path, and comparing the gain of the detection signal received from the reverse gain detection means with the reference gain to match the reverse primary path gain correction. And controlling the path selecting means, terminating the reverse main path by controlling the reverse main path gain correction and the path selecting means, and comparing the gains of the detection signal received from the reverse gain detecting means with the reference gain to coincide with each other. And a controller for controlling said reverse diversity path gain correction and path selection means. A time diversity system for strengthening immunity to fading by synthesizing a main path and a diversity path of a repeater for transmitting a signal of a base station to a mobile station and a signal of the mobile station to a base station with equal gain, A forward main path gain correction and path selecting means for receiving the signal received through the base antenna side antenna and terminating or gain adjustment; Forward diversity path gain correction and path selection means for terminating or gain-adjusting the time-delayed signal received through a base station-side diversity antenna and receiving a predetermined time-delayed signal; A forward coupler for coupling the outputs of said forward gain correction and path selection means; Forward gain detection means for monitoring the combined signal to detect gain of a selected path; Reverse main path gain correction and path selection means for receiving the signal received through the mobile station side antenna and terminating or gain adjustment; Reverse diversity path gain correction and path selection means for terminating or gain-adjusting the time delayed signal received through the mobile station side diversity antenna and receiving a predetermined time delayed signal; A reverse coupler for coupling the outputs of the reverse gain correction and path selection means; Reverse gain detection means for monitoring the combined signal to detect gain of a selected path; Controlling the forward diversity path gain correction and path selection means at an adjustment period to terminate the forward diversity path, storing the gain of the detection signal received from the forward gain detection means as a reference gain of the forward main path, and forward Main path gain correction and path selection means are controlled to terminate the forward main path, and the forward diversity path is matched with each other by comparing the gain of the detection signal received from the forward gain detection means with the reference gain of the stored forward main path. Control gain correction and path selection means, Controlling the reverse diversity path gain correction and path selection means to terminate the reverse diversity path, storing the gain of the detection signal received from the reverse gain detection means as a reference gain of the reverse main path, and performing the reverse main path. Controlling the gain correction and path selection means to terminate the reverse main path, and comparing the gain of the detection signal received from the reverse gain detection means with the reference gain of the stored reverse main path to match the reverse diversity path gain correction. And a controller for controlling the route selection means. 8. The method according to any one of claims 4 to 7, wherein the gain correction and path selection means An RF switch for terminating or connecting the corresponding path according to the path selection signal of the controller, and a gain adjusting unit for adjusting the gain of the signal connected through the RF switch according to the gain control signal of the controller. Diversity System. 8. A gain detection means according to any one of claims 4 to 7, An amplifier for monitoring and amplifying a high frequency signal of a corresponding path, a band pass filter for filtering the output of the amplifier, a synthesizer for generating a predetermined frequency, and a high frequency output signal of the band pass filter by mixing with the output of the synthesizer A time diver comprising a mixer for converting to a frequency signal, an intermediate frequency amplifier for amplifying the output of the mixer, a bandpass filter for filtering the output of the intermediate frequency amplifier, and a detector for detecting the level of the filtered signal Sticky system.