Radio frequency uninterrupted on-load switcher

Abstract

The invention discloses a radio frequency uninterrupted on-load switcher, relates to the technical field of radio and television transmission, and is used for solving the problem that a traditional radio frequency coaxial switch cannot be switched on load. The radio frequency uninterrupted on-load switcher is mainly composed of two paths of radio frequency power couplers. The two-way radio frequency power coupler is composed of two 3dB electric bridges and two adjustable band-pass filters, and the two adjustable band-pass filters are connected between the two 3dB electric bridges. In order to facilitate regulation and control, the working frequencies of the two adjustable band-pass filters are adjusted through the controller, so that the adjustable band-pass filters are switched between a'conductive 'state and a'non-conductive' state, and different transmitters are selected to be connected to the antenna. The circuit is simple in structure and convenient to control, only one set of antenna is needed, a transmitter used at present does not need to be changed, the circuit can be achieved only by replacing an original main and standby machine switching coaxial switch, transformation is simple, and cost is low.

Description

Technical Field

[0001] This invention relates to the field of broadcast television transmission technology, specifically a radio frequency uninterrupted on-load switcher for switching between primary and backup units in a broadcast television transmission system. Background Technology

[0002] Ensuring safe broadcasting is a core task that the State Administration of Radio and Television has long prioritized. In recent years, with increasingly stringent requirements for safe broadcasting management, the State Administration of Radio and Television has further strengthened its regulatory standards for safe broadcasting in wireless coverage systems, explicitly stipulating that any broadcast interruption exceeding 3 seconds during important broadcast periods constitutes a safe broadcasting incident. This stringent time standard presents unprecedented challenges to the primary / backup switching technology of existing transmission systems.

[0003] In traditional broadcast television transmission systems, switching between primary and backup transmitters is typically achieved using an RF coaxial switch. When the primary transmitter malfunctions or requires maintenance, the system must first shut down the RF power output of the primary transmitter, then control the switching switch to switch the RF path from the primary to the backup transmitter, and finally turn the backup transmitter output back on. The overall switching time is relatively long, often reaching several seconds or even longer. This interruption-based switching method not only causes a brief interruption of the broadcast signal but also fails to meet the stringent "3-second" fault detection threshold.

[0004] Therefore, the industry urgently needs a technical solution that can achieve fast, smooth, and uninterrupted switching to completely overcome the inherent defects of traditional radio frequency coaxial switching switches in terms of switching time and switching mode, thereby providing a solid and reliable technical guarantee for achieving high-standard safe broadcasting tasks. Summary of the Invention

[0005] This invention aims to provide a radio frequency uninterrupted load-carrying switcher to directly replace traditional radio frequency coaxial switches, solving their inability to switch under load. Through this invention, rapid, smooth, and uninterrupted switching of the radio frequency output channels of both the primary and backup transmitters can be achieved when both are operating at normal output power. This ensures continuous and uninterrupted radio frequency signal throughout the switching process, and the switching action is completed in a very short time. This completely eliminates the potential for broadcast interruptions caused by switching operations, effectively extends equipment lifespan, and comprehensively enhances the ability to ensure safe broadcasting.

[0006] To solve the above problems, the present invention adopts the following technical solution:

[0007] The present invention discloses an uninterrupted radio frequency (RF) load switcher, comprising a first 3dB bridge, a second 3dB bridge, a first adjustable bandpass filter, and a second adjustable bandpass filter; the two ends of the first and second adjustable bandpass filters are respectively connected to the first and second 3dB bridges, one end of the first 3dB bridge is connected to a first transmitter, and the remaining end of the first 3dB bridge is connected to an antenna; one end of the second 3dB bridge is connected to a second transmitter, and the remaining end of the second 3dB bridge is connected to an absorption load.

[0008] The radio frequency uninterrupted load switcher also includes a controller, which receives a control signal to synchronously adjust the state of the two adjustable bandpass filters so that the two adjustable bandpass filters are in a conducting or non-conducting state.

[0009] The first adjustable bandpass filter and the second adjustable bandpass filter are radio frequency adjustable bandpass filters.

[0010] The controller performs calculations via a microcontroller; the control signals of the microcontroller come from the manual switching signal and the monitoring abnormal signal, which is issued by the monitoring device; the output signals of the microcontroller are connected to the first motor and the second motor; the first motor and the second motor drive the linear screw of the radio frequency adjustable bandpass filter to achieve the switching of the radio frequency uninterrupted load switch between the first transmitter and the second transmitter as the main and backup units.

[0011] The beneficial effects obtained by this invention are:

[0012] The radio frequency uninterrupted load switcher provided by this invention can achieve full power output of either the main unit or the standby unit. The entire switching process does not require shutting down the transmitter and is completed in about 1 second.

[0013] During peak broadcast periods, both transmitters operate at full power simultaneously, with the RF power output to the antenna being the main transmitter's output. If the main transmitter malfunctions during broadcast, the uninterrupted RF switch can switch to the backup transmitter to continue operating. During the switching process, the total output power is converted from the main transmitter's transmission power to the backup transmitter's transmission power. The entire process does not require shutting down the main transmitter; instead, it directly switches to the backup transmitter's output.

[0014] The uninterrupted radio frequency load switch provided by this invention is suitable for retrofitting currently used transmitters. It does not require modification of the current transmitter; it can be achieved simply by replacing the original main / backup coaxial switch with the uninterrupted radio frequency load switch provided by this invention. The retrofit is simple and low-cost.

[0015] This invention is applicable not only to digital television transmitters but also to FM transmitters. By simply changing the center frequency of the adjustable bandpass filter, the purpose of switching between the main and backup transmitters can be achieved.

[0016] When one transmitter is working, the other transmitter can be turned on or off for maintenance, replacement, or other operations, greatly facilitating the work of the station.

[0017] Compared to the DTMB single-frequency network backup system, this system has only one transmitting antenna, which does not affect the waveform characteristics of the space wave coverage and has no adverse effects on the user's received signal. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the radio frequency uninterrupted load switcher of the present invention.

[0019] Figure 2 This is the equivalent circuit of the adjustable bandpass filter of the radio frequency uninterrupted load switcher of the present invention when it is turned on.

[0020] Figure 3 This is the equivalent circuit of the RF uninterrupted load switcher when the adjustable bandpass filter is not conducting.

[0021] Figure 4 This is a schematic diagram of the connection structure between the radio frequency uninterrupted load switcher and the controller of the present invention.

[0022] Figure 5 This is a simplified diagram of the network structure using the radio frequency uninterrupted on-load switch of the present invention.

[0023] Figure 6 This is the test result when both transmitters are turned on simultaneously, and the broadcast is done using the first transmitter.

[0024] Figure 7 It is the worst test result that the instrument can capture when the first transmitter switches to the second transmitter.

[0025] Figure 8 This is the test result when both transmitters are turned on simultaneously, and the broadcast is switched to the second transmitter.

[0026] Figure 9 This is the test result when the second transmitter is turned off and the first transmitter is used for broadcasting.

[0027] Figure 10 This is a control principle diagram of the radio frequency uninterrupted load switcher and controller of the present invention.

[0028] Figure 11 This is a physical diagram of the radio frequency uninterrupted load switcher and controller of the present invention.

[0029] The components in the diagram are labeled as follows: First 3dB bridge 1, Second 3dB bridge 2, First adjustable bandpass filter 3, and Second adjustable bandpass filter 4. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings.

[0031] A schematic diagram of the overall structure of the radio frequency uninterrupted load switcher described in this invention is shown below. Figure 1 As shown, the load switcher consists of two RF power couplers and a controller. The two RF power couplers each consist of two 3dB bridges and two adjustable bandpass filters. Their connection method is as follows:

[0032] A first transmitter is connected to one end of a first 3dB bridge 1, and the other end of the first 3dB bridge 1 is connected to an antenna. The remaining two ends of the first 3dB bridge 1 are connected to a first adjustable bandpass filter 3 and a second adjustable bandpass filter 4, respectively. The other ends of the first adjustable bandpass filter 3 and the second adjustable bandpass filter 4 are connected to the two ends of a second 3dB bridge 2, respectively. A second transmitter is connected to one end of the second 3dB bridge 2, and the remaining end of the second 3dB bridge 2 is connected to an absorption load.

[0033] Based on the characteristics of the 3dB bridge, in this invention, it is not necessary to distinguish between individual pins; it is only necessary to follow the... Figure 1 You can connect using that method.

[0034] The controller primarily receives control signals and adjusts the operating frequencies of the two adjustable bandpass filters based on the current state, switching the filters from an "on" state to a "off" state, or vice versa. The controller can employ both automatic and manual control adjustments.

[0035] This device utilizes the directional coupling and combining characteristics of a 3dB bridge combined with an adjustable bandpass filter to replace the traditional RF coaxial switch. When both transmitters are simultaneously powered on and outputting rated power, the adjustable bandpass filter can be controlled to determine whether the output power is fed to the antenna or absorbed by the load, thus achieving seamless "load switching".

[0036] In this embodiment, the adjustable bandpass filter is an RF adjustable bandpass filter. This type of adjustable bandpass filter adjusts the resonant cavity length or capacitor plate position via a linear screw. The controller is essentially a two-way motor control circuit; the adjustable bandpass filter is adjusted by rotating the motor to control the linear screw.

[0037] Furthermore, the controller employs a microcontroller, and its control principle is as follows: Figure 10As shown. The control signals come from the manual switching signal and the abnormal detection signal, which is provided by the monitoring equipment. When the microcontroller receives the control signal, it controls the first motor and the second motor. The purpose of the first motor and the second motor is to switch the operating frequencies of the first adjustable bandpass filter and the second adjustable bandpass filter, so that the signals from the first generator and the second transmitter can switch between being unable to pass and being able to pass.

[0038] Mode 1: Second transmitter broadcasts, first transmitter is in hot standby (normal operating state).

[0039] In this state, all tunable bandpass filters are tuned to the system's transmit frequency.

[0040] Second transmitter (primary) path: The rated RF signal output by the second transmitter is split into two paths after entering the second 3dB bridge. These two signals pass through corresponding adjustable bandpass filters (since the filter center frequency is f0, the signal can pass through smoothly), and then enter the first 3dB bridge for synthesis. Due to the network design, the signals are synthesized in phase here and fed to the antenna port for radiation.

[0041] First transmitter (backup) path: The first transmitter also outputs a rated RF signal, which is split into two paths after entering the first 3dB bridge. These two signals also pass through corresponding adjustable bandpass filters (center frequency f0) before entering the second 3dB bridge for synthesis. Due to network design, the signal is guided to the absorption load port at the second 3dB bridge for synthesis and dissipation, without radiating effective power to the antenna.

[0042] Mode 2: The process of switching from the second transmitter to the first transmitter

[0043] When it is necessary to switch from the second transmitter to the first transmitter for broadcast, the operating frequency of the two adjustable bandpass filters can be quickly adjusted by the controller.

[0044] At the moment of switching onset: The adjustable bandpass filter begins to tune from its original center frequency (f0) to a new frequency point deviating from f0.

[0045] During the switching process: For the second transmitter path, as the center frequency of the adjustable bandpass filter on its path deviates from f0, the attenuation of the transmitter frequency (f0) signal by the adjustable bandpass filter gradually increases, resulting in a gradual weakening of the signal components that can reach the first 3dB bridge and be synthesized to the antenna.

[0046] For the first transmitter path, as the center frequency of the adjustable bandpass filter in its path is tuned to a new state, the signal path previously directed to the load is altered. The signal gradually passes through the adjusted network, is synthesized at the first 3dB bridge, and fed to the antenna, with its strength gradually increasing.

[0047] Switching key features:

[0048] 1. Load and uninterrupted operation: During the entire switching process, neither transmitter needs to be turned off or its power reduced, and both maintain their rated power output at all times.

[0049] 2. Output continuity: At the antenna port, the synthesized RF signal is always output, with no power interruption.

[0050] 3. Switching time: The entire frequency tuning and signal rerouting process can be completed quickly.

[0051] 4. Impact on the receiver: If the two transmitters are synchronized or in single-frequency network mode, the receiver can switch seamlessly. If they are only asynchronous signals on the same frequency and do not form a single-frequency network, during the handover transition, some energy from the signals of the two transmitters may reach the antenna simultaneously, creating brief co-channel interference. The receiver will experience a short-term pause, which will recover immediately after the handover is completed.

[0052] Mode 3: Switching complete (first transmitter broadcasting, second transmitter hot backup)

[0053] After the switching action is completed, the adjustable bandpass filter stabilizes at the new operating frequency setting.

[0054] First transmitter (primary) path: The signal output by the first transmitter can now be in-phase synthesized at the first 3dB bridge through the filters and networks on its path and effectively fed to the antenna port for broadcast.

[0055] Second transmitter (backup) path: The signal output by the second transmitter is effectively blocked or rerouted due to the influence of the new operating frequency of the filter on its path. It is then directed to the absorption load at the second 3dB bridge and consumed, thus stopping radiation to the antenna.

[0056] Status Summary: The main broadcaster has been seamlessly switched from the second transmitter to the first transmitter, and the second transmitter has entered hot backup mode. The system has returned to a stable state similar to Mode 1, but with the main and backup roles reversed.

[0057] After the switchover is complete, the backup transmitter can be shut down, and the offline transmitter can be inspected and maintained.

[0058] The uninterruptible radio frequency (RF) load switcher of this invention differs significantly from a coaxial switch, specifically as follows: A coaxial switch is a contact-based switch; during power switching, the VSWR is very high before contact occurs, and arcing can cause it to burn out when contact is made. The load switcher, unlike a coaxial switch, uses power coupling instead of contact switching, eliminating the arcing and increased VSWR problems associated with coaxial switches.

[0059] Installation test

[0060] The invention was applied to the Tiandong County Microwave Station and tested on December 2, 2025. The main purposes were as follows:

[0061] 1. Simultaneously power on both the primary and backup transmitters to normal operating conditions and test whether there is any interference between the primary and backup transmitters that affects the user's digital television reception and viewing experience;

[0062] 2. The impact of the uninterrupted radio frequency (RF) on user reception during the switching process between the main and backup transmitters.

[0063] The main unit of the Tiandong County Microwave Station uses the existing Dexin 300W digital TV transmitter, and the backup unit uses the existing full-wave 300W digital TV transmitter. The main and backup units are connected to the A and B input terminals of the RF uninterruptible load switcher, respectively. The antenna output terminal of the load switcher is connected to the station's transmitting antenna, and the load port of the load switcher is connected to a dummy load. The equipment connection diagram is shown below. Figure 5 As shown. The switching process is done manually.

[0064] The testing steps are as follows:

[0065] 1. Test by turning on the main transmitter separately;

[0066] 2. Test the backup transmitter separately;

[0067] 3. The main and backup transmitters are turned on simultaneously and a switching test is performed.

[0068] The test content included: open-circuit reception tests with different transmitters powered on; and reception performance tests during the switching between primary and backup units using an uninterrupted RF load switcher. At a far-field test point approximately 15 kilometers from the transmitting station, the Baoying Technology MA969 portable broadcast television integrated tester was used for testing.

[0069] Test Results

[0070] 1. With both transmitters running simultaneously, the far-field reception performance and specifications were measured using transmitter 1. The received signal level was 47.5 dBuV, and the MER (Mean Interval) was 22.9 dB. The picture was clear and smooth. The test results are as follows: Figure 6 As shown.

[0071] 2. When switching from transmitter 1 to transmitter 2, the switching process was so rapid that the worst result the instrument could capture was a received signal level of 47.5 dBuV and a MER of 15.1 dB. The image froze almost instantly, easily missed without close observation. The test results are as follows. Figure 7 As shown.

[0072] 3. With both transmitters powered on simultaneously, the far-field reception effect and specifications were tested when switching to transmitter 2 for broadcasting. The received signal level was 48.5 dBuV, and the MER (Mean Interval) was 23.7 dB, resulting in a clear and smooth picture. The test results are as follows: Figure 8 As shown.

[0073] 4. With transmitter 2 turned off, the far-field reception effect and specifications were tested using transmitter 1 during broadcasting. The received signal level was 48.0 dBuV, the MER was 23.0 dB, and the picture was clear and smooth. The test results are as follows: Figure 9 As shown.

Claims

1. A radio frequency uninterrupted load switcher, characterized in that, It includes a first 3dB bridge, a second 3dB bridge, a first adjustable bandpass filter, and a second adjustable bandpass filter; the two ends of the first and second adjustable bandpass filters are respectively connected to the first 3dB bridge and the second 3dB bridge; one end of the first 3dB bridge is connected to a first transmitter, and the remaining end of the first 3dB bridge is connected to an antenna; one end of the second 3dB bridge is connected to a second transmitter, and the remaining end of the second 3dB bridge is connected to an absorption load.

2. The radio frequency uninterrupted load switcher according to claim 1, characterized in that, It also includes a controller, which receives a control signal to synchronously adjust the state of the two adjustable bandpass filters so that the two adjustable bandpass filters are in a conducting or non-conducting state.

3. The radio frequency uninterrupted load switcher according to claim 1, characterized in that, The first adjustable bandpass filter and the second adjustable bandpass filter are radio frequency adjustable bandpass filters.

4. The radio frequency uninterrupted load switcher according to claim 3, characterized in that, The controller performs calculations via a microcontroller; the control signals of the microcontroller come from the manual switching signal and the monitoring abnormal signal, which is issued by the monitoring device; the output signals of the microcontroller are connected to the first motor and the second motor; the first motor and the second motor drive the linear screw of the radio frequency adjustable bandpass filter to achieve the switching of the radio frequency uninterrupted load switch between the first transmitter and the second transmitter as the main and backup units.

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