As countries mandate in-car wireless radio, these chips still have a place in in-car AM and FM

Recently, the U.S. House of Representatives Energy and Commerce Committee passed the AM Radio for Every Vehicle Act of 2024, which requires automakers to retain AM (amplitude modulation) functions in vehicles manufactured and sold in the United States. The bill was passed by the committee with a vote of 45 to 2 and is currently awaiting final approval by the full House of Representatives.

Earlier, China's Ministry of Industry and Information Technology also publicly solicited opinions on the mandatory national standard formulation and revision plan project for the "In-vehicle Wireless Broadcast Reception System", and emphasized that the in-vehicle wireless broadcast reception system is an important infrastructure to ensure that the public can quickly and effectively receive authoritative emergency information in an emergency state.

Why do we need in-vehicle wireless broadcasting?

As an important tool for in-car entertainment and receiving information, the in-vehicle wireless broadcast reception system has been a standard feature of cars for a long time. However, in recent years, with the rapid development of Internet of Vehicles technology, new energy vehicles and smart cars have gradually adopted large-screen connected car machines as standard, and wireless broadcasting has gradually faded out of the public's view.

According to foreign media reports, many car companies, including emerging brands such as Tesla, Polestar, and Rivian, as well as traditional brands such as Ford, Mazda, and BMW, have launched new models without AM radio functions in recent years. For example, Tesla removed the AM radio from its vehicles in 2018, and Ford's 2024 Mustang also does not have AM radio functions.

In China, automobile intelligence is more developed, and FM and AM are being eliminated by some car brands, replaced by radio software, which transmits audio content through data streams. It actually uses car network traffic, which is not a car-mounted wireless broadcast receiving system. Some models of brands such as Tesla, BYD, and Xiaopeng have cancelled the in-car physical radio.

Not only the United States and China, but also the European Union, Japan, and the Middle East have previously issued relevant standards and mandatory measures for in-vehicle radio equipment. Among them, the European Union issued the Radio Equipment Directive (RED) 2014/53/EU in 2014. After June 13, 2017, only radio equipment that meets the RED directive and obtains the CE-mark is allowed to be sold in the EU market. Car radios, car digital audio broadcasts, car wireless communication terminals, etc. are all within the scope of the RED directive.

Why do all countries emphasize the need for car radio equipment? Ed Markey, Democratic Senator from Massachusetts and co-drafter of the U.S. "2024 Car AM Broadcasting Act", said in a statement that the slow demise of AM radio may prevent people from obtaining information during natural disasters or other emergencies. With the arrival of hurricane season, it is more important than ever to pass the bill and ensure that this life-saving communication tool remains in the car.

In fact, as early as August 14, 2023, the State Administration of Radio, Film and Television of China and other departments issued the "Notice on Further Strengthening the Management of Car Audio and Video", deploying and promoting the installation of wireless broadcast receiving systems in the automotive field. Wireless broadcast receiving systems have unique advantages in receiving sudden natural disasters (such as earthquakes, floods, etc.).

The coverage radius of FM radio transmitters exceeds 100 kilometers, and the coverage distance of medium wave radio stations can reach thousands of kilometers. The transmitters are far away from car drivers and passengers, and are less likely to be affected by the same disaster. The wireless transmission distance from 2G/3G/4G/5G cellular receiving terminals to base stations is from a few hundred meters to thousands of meters, and there is a great possibility that car drivers and base stations will suffer disasters at the same time. Therefore, when cellular base stations are damaged due to sudden emergencies such as earthquakes, floods, and typhoons, the wireless broadcast receiving system on the vehicle will play a key role.

What chips are needed for in-vehicle AM ​​and FM?

AM (amplitude modulation) broadcasting and FM (frequency modulation) broadcasting are two different radio signal transmission methods. AM's modulation method is to transmit information by changing the amplitude of radio waves, and its signal amplitude will change with the strength of the sound; while FM transmits information by changing the frequency of radio waves, and the signal frequency will change with the strength of the sound.

In terms of anti-interference ability, FM is stronger because its signal changes are based on frequency and are not easily affected by noise and interference; AM is relatively weak and is easily interfered by lightning, electrical equipment, etc., resulting in reduced sound quality. But the important thing is that AM has a longer transmission distance and can cover a larger range; while FM has a relatively short transmission distance and is only suitable for broadcasting in local areas such as cities.

AM and FM broadcasting require different types of radio reception. Although many modern radios can receive both AM and FM signals, dedicated AM radios are usually simpler, while FM radios may offer more features and better sound quality.

Therefore, the requirements for the two in terms of chips are also different. AM chips mainly support medium wave (MW) and short wave (SW) bands, which usually have lower broadcast frequency ranges, such as 5251610KHz for medium wave and 3.226.1MHz for short wave. AM stands for Amplitude Modulation, which modulates the audio signal onto the "amplitude" of a high-frequency carrier. This modulation method makes AM broadcasts susceptible to interference during transmission and has relatively poor sound quality.

Due to the characteristics of AM signals, on-board AM chips need to have strong anti-interference capabilities and stable reception performance to ensure that broadcast signals can still be clearly received in complex environments.

FM chips mainly support frequency modulation (FM) broadcast bands, which have a higher broadcast frequency range, usually 87.5~108MHz. FM stands for Frequency Modulation, which modulates the audio signal onto the "frequency" of a high-frequency carrier. This modulation method makes FM radio have higher anti-interference ability and better sound quality.

Car FM chips usually use more advanced reception processing technology, such as digital signal processing technology (DSP), to improve reception sensitivity and sound quality. At the same time, some high-end car FM chips also support RDS (Radio Data System) function, which can display information such as radio station name and playlist.

Many manufacturers can provide chips required for car AM and FM, such as Silicon Labs. The company's Si4792x series and Si4730_31-D60 chips not only support AM but also FM, and integrate audio processors to provide high-performance broadcast reception functions. Its Si4731-C40-GUR supports AM, FM and RDS functions, has a high degree of integration and flexibility, and is widely used in car radios, portable radios and consumer electronics.

For example, NXP's TEF6686 is usually used in car radios with multiple functions, supporting frequency bands such as AM. Its TEF6621 chip integrates all key RF components, including voltage-controlled oscillators, ceramic filters, intermediate frequency transformer coils, low-noise amplifiers and automatic gain control, etc. It has perfect weak signal processing, FM noise blanking, multi-path suppression of environmental interference noise and other functions, and is an ideal radio solution.

Manufacturers such as Texas Instruments and STMicroelectronics can also provide a variety of chip products suitable for car AM radios, including high-frequency tuners, audio processing chips, microcontrollers, etc. For example, STMicroelectronics' TDA7388 is a new technology Class AB audio power amplifier with high output power capability, low distortion and low output noise, suitable for high-end car radios.

Written in the end

With the rapid development of car networking technology, new energy vehicles and smart cars have gradually made large-screen connected car machines as standard. The wireless broadcast receiving system has been impacted to a certain extent, but it can be seen that its unique emergency information receiving function still makes it irreplaceable. In the future, with the introduction and implementation of relevant mandatory national standards, the utilization rate of car wireless broadcast receiving systems will be very high, which is undoubtedly good news for many manufacturers who provide related chips.