FM broadcast coverage system for underground parking lot

1. Overview

The system adopts the method of "digital FM broadcast repeater + indoor passive distribution system", which can introduce aerial FM broadcast signals (up to 16 channels of broadcast frequencies) into all corners of the underground parking lot; and in an emergency, through these 16 channels frequency broadcasts the traffic regulation instructions of the parking lot management department to make the vehicles evacuate quickly and orderly.

2. System features

●The system equipment is simple: only one active device (repeater) can realize all forwarding functions, and the engineering installation is simple;

●Multiple forwarding programs: up to 16 channels of FM radio programs can be forwarded on the same frequency, which can meet the broadcasting needs of most cities;

●High-fidelity sound quality: broadcast-level technical indicators, beautiful sound quality, and clear voice.

●Low interference in the same frequency at entrances and exits: Using digital co-channel forwarding technology, there is almost no interference at the entrance and exit of the parking lot;

●Traffic diversion: In case of emergency, the parking lot management department can use the 16 channels of broadcasts to divert traffic.

●Stable and reliable: using software radio technology, fully sealed wall-mounted chassis, small in size and extremely safe.

●Remote monitoring: The remote monitoring and control of the system can be realized through network cable, optical cable or 4G network.

3. System composition and working principle

A. System composition

A complete underground parking lot FM broadcast coverage system consists of the following parts:

1) FM full-band receiving antenna

2) FM broadcast repeater (digital technology)

3) Broadcast signal passive distribution and transmission system equipment (distributor, coupler, transmitting antenna, etc.)

4) Emergency broadcast processor (optional, optional when traffic diversion is required)

5) Remote monitoring and monitoring system software and hardware (optional, select when remote monitoring is required)

The system composition diagram is as follows:

B. Working principle

FM broadcasting (87-108MHz) radio waves are mainly linear transmission and have a certain degree of diffraction ability. The underground parking lot is covered by car radios, and the coverage field strength can reach 35dBuV/m, which can be well received.

In view of the transmission characteristics and coverage field strength requirements of FM broadcasting, and considering the system construction cost and cost-effectiveness, it is appropriate to adopt "digital FM broadcasting repeater + indoor passive distribution system", and adopt a wideband miniaturized transmitting antenna at the end for coverage. For the general parking structure, a set of underground parking lot broadcast coverage system can achieve the coverage of 16 channels of FM broadcast programs with a construction area of about 20,000 square meters.

The core equipment of the system is the "digital FM broadcast repeater". The main function of this equipment is to perform low-noise amplification (LNA), 16-channel digital frequency selection, and emergency broadcast on the full-band FM broadcast signal received by the FM broadcast receiving antenna. Signal switching, radio frequency broadband linear amplification, band-pass filter output; and integrated 4G router, which can realize remote monitoring and monitoring of equipment.

The FM broadcast signal output by the digital FM broadcast repeater is transmitted to each small transmitting antenna for wireless transmission through a passive distribution system composed of several power distributors, power couplers, coaxial cables, etc., according to the different plane structure of the basement. The basement is covered seamlessly.

In order to give full play to the functions of the system, the system can be used to command underground vehicles and divert traffic in emergency situations. At this point, you only need to turn on the "emergency broadcast processor" and switch the "digital FM broadcast repeater" to the emergency broadcast mode, and you can hear the content of the emergency broadcast in the 16 channels of FM broadcast signals. The emergency broadcast processor has a variety of audio signal source inputs: microphone input for voice broadcast, SD card playback to achieve recorded programs, or emergency audio signals sent by other audio playback devices.

In order to facilitate the management, the repeater can be remotely monitored and monitored. The working status of the repeater can be observed on the monitoring server of the monitoring center, and the repeater can be remotely controlled to switch the working mode (normal mode and emergency mode). The data communication method between the monitoring server and the repeater can be through 4G network, optical fiber, network cable, etc.