Broadcast signal same-spectrum transmission technology was born!
People listen to radio, storytelling, and novels in cars, but after driving not far, they can no longer hear the radio; Traffic broadcast information and noise appeared before leaving the administrative area. The birth of broadcast signal co-spectrum transmission technology has completely solved the stubborn problem that affects the long-distance transmission of broadcast signals - co-channel interference. In the future, people can drive their cars on hundreds or even thousands of kilometers of roads without changing channels and listen to broadcast signals clearly and continuously.
The broadcast signal same-spectrum transmission system has been successfully developed by Shenzhen Same-Channel Technology Company. At the same time, this technology has applied for an invention patent to the State Intellectual Property Office and passed the preliminary review. The same-spectrum transmission technology completely breaks the existing theory of same-frequency synchronous transmission. It adopts the method of digital spectrum synthesis to truly realize the same frequency, same phase and same modulation of synchronous transmitter signals, so that the broadcast signal emitted by each transmitter can be The spectrum is exactly the same. This technology can not only be applied to the transmission of analog broadcast signals, but can also be applied to the same-frequency synchronous transmission of digital broadcast and digital TV signals in the future.
Radio and TV signal same-spectrum transmission technology and implementation method
1. Introduction to same-spectrum transmission technology
In the realization of radio and TV signal (analog, digital) In a multi-base station co-frequency synchronous transmission system, the previous technical solution is to generate a modulated carrier signal through each independent base station, and achieve co-frequency synchronization of network signals through a GPS synchronized clock. In practical applications, this technical solution can only achieve that the frequency error and phase error of the modulated carrier signal tend to be smaller, but cannot be zero. Because the previous solution has a delay error between the reference clock signal and the modulated carrier signal, the carrier spectrum emitted by each base station is not completely consistent. The carrier signals between adjacent base stations are within the equal field strength area (6db) Multipath signal interference will inevitably occur, causing serious fading of the carrier for analog signals, and causing a sharp deterioration of the bit error rate for digital signals.
2. Working principle of radio and television signal transmission in the same spectrum
In order to achieve synchronization of radio and television signals in the same frequency spectrum and interference-free remote signal coverage. It adopts the same-spectrum signal relay transmission method, that is, the spectrum of the radio and television carrier signal is copied so that the carrier signal waveforms emitted by adjacent base stations are completely consistent, thereby achieving interference-free signal coverage within the coherent area of ??adjacent base stations. Taking FM broadcast as an example, the explanation is as follows:
(1) Master station sending part
The FM broadcast carrier signal passes through the transmitter end monitoring port and is transmitted to the filter amplification unit of the spectrum synthesizer. It is pre-amplified and then sent to the AGC control amplification unit to perform automatic gain adjustment on the signal. The constant signal is sent to the spectrum sampling unit to further purify the signal. One channel is sent to the mixer through the bandpass amplifier, and the other channel The signal is frequency-selected and amplified by the digital frequency selection unit. The signal is sent to the high-speed analog-to-digital conversion unit, where it becomes a digital signal and sent to the digital encoding processing unit to encode various parameters of the signal (signal phase, time delay, frequency, etc.), the data code stream generated in the digital encoding processing unit marks the main spectrum parameters of the broadcast signal. The signal is sent to the data comparison unit, where the parameters are compared with the frequency synthesis signal to generate a digital phase-locked data signal. , the reference signal is generated in the phase-locking unit, and the signal is sent to the frequency synthesizer to produce an accurate and stable frequency synthesized signal. The signal is sent to the mixer to generate a new intermediate frequency signal, which is filtered and frequency multiplied before being emitted as a microwave signal. The reference clock signal is sent to the digital encoding processing unit through digital frequency multiplication. The digital encoding unit synthesizes a data code stream. After being sent to the data comparison unit for processing, a spectrum parameter data signal is generated, which is transmitted to each base station through the data conversion unit and GSM module.
(2) Spectrum signal restoration of each base station
Each base station receives the microwave signal of the base station through the antenna, amplifies and down-converts it to generate the first intermediate frequency signal, which is filtered and sent all the way to the The bandpass amplifier, the other channel is sent to the frequency selection amplifier, which generates a pure spectrum analog signal through digital frequency selection, and is sent to the high-speed analog-to-digital conversion unit. It is converted into a digital signal and sent to the digital encoding processing unit. In the digital processing unit, it is compared with the reference clock The signal is encoded and data processed to generate a specific data code stream containing parameters such as frequency, phase, delay, etc. After the comparison processing unit compares the data with the data parameters from GSM, it is sent to the digital phase locking unit, where Generate a parameter control signal, which is sent to the frequency synthesizer, where a local oscillator frequency with the same spectrum as the base station is generated. This signal is mixed with the first intermediate frequency signal from the base station to restore the FM broadcast carrier signal, and is filtered and linearly amplified. , emitted through the transmitter. In the first debugging, the GSM reference data signal from the central station can automatically and accurately calibrate the frequency, phase, delay and other parameters of the system. Short-term stability is guaranteed by the stability factor of the reference clock. Within a period of less than 24 hours, the system will automatically perform accurate synchronization.
(3) Technical key to the solution
This project uses the digital spectrum replication and restoration method to enable adjacent radio and television transmitters to emit exactly the same spectrum signals. This is a key technological breakthrough. The system uses a local oscillator signal source to restore the carrier signal, and the frequency, phase, delay and relative error of the restored carrier signal reach the minimum value. Since each base station emits exactly the same spectrum signal, co-channel interference in the intersection area is minimized. All indicators of the system far exceed the national ministry standards.
(4) Simple test method for technical effects
Place two radio and television transmitters A and B with the same spectrum in a room, use the same frequency to broadcast a set of programs, and use standard When the receiving terminal (radio or TV) moves from the A transmitting area to the B transmitting area, and then moves from the B transmitting area to the A transmitting area, there should be no obvious noise or noise in the receiving terminal. This test clearly demonstrated the unique technical effects of the same-spectrum transmission system, and also highlighted the obvious advantages of the same-spectrum transmission technology in the simultaneous transmission of radio and television.
3. Co-spectrum transmission technology has the following advantages:
(1) The first domestic and foreign co-frequency multi-base station radio and television signal transmission with approximately interference-free synchronous transmission. It can achieve simultaneous transmission coverage of FM radio, analog TV, and digital TV signals on the same frequency.
(2) Clock synchronization does not need to rely on the GPS satellite clock system, and the system reliability is greatly improved, which has far-reaching political significance for the security of my country’s radio and television signal transmission coverage.
(3) The base station is flexible to set up, does not need to lay optical cables, is convenient for networking, and shortens the construction period.
(4) The cost of base station construction is greatly reduced, and the comprehensive construction cost of a unit base station is only one-half of that of existing technology.
(5) Realize fully transparent transmission of radio and television signals, and can be applied to signal transmission of any modulation standard of analog radio and digital radio and television.
(6) The effective coverage power per 10,000 square kilometers is only one-quarter of the existing technology, which greatly reduces electromagnetic environmental pollution and has obvious power energy saving effects.
(7) Effectively save spectrum resources and achieve simultaneous coverage of radio and television signals in provincial administrative regions with a single frequency.
(8) The same spectrum transmission uses high-band microwave digital spectrum synthesis technology. The signal transmission has the characteristics of safety, confidentiality, anti-interference, etc., and meets the national security requirements for radio and television signal transmission.
4. The same spectrum transmission technology is the first of its kind in China.
After searching international information through the Intellectual Property Center, no similar inventions were found. The implementation method of same-spectrum transmission technology is the first of its kind in China. This technology has applied for an invention patent to the State Intellectual Property Office.
At the same time, the core technology modules under this technical solution, including digital radio and television same-spectrum relay modules, analog broadcasting same-spectrum relay modules, etc., have been jointly developed by many domestic research institutions.