Many countries around the world attach great importance to the value of broadcast emergency communication: India (2023), Brazil (2021), Mexico (2017), and others have mandated that mobile phones be equipped with FM radios and have them enabled by default; the EU (2018) and Germany (2019) have legislated that new cars be equipped with DAB digital broadcasting; the International Telecommunication Union and other organizations have also continuously called on mobile phone manufacturers to retain and enable FM functionality. Against this backdrop, China's GB mandatory national standard for "In-Vehicle Wireless Broadcast Receiving Systems" was officially project initiated at the end of April 2025. It is expected to be released by the end of February 2027 and planned for mandatory implementation by the end of February 2029, clearly stating that:
In extreme disaster scenarios, mobile communication base stations are highly susceptible to paralysis. FM/DAB broadcasting, which consumes no data and does not rely on base stations, serves as a critical safety net for emergency communication. Traditional mobile phone FM has obvious shortcomings. Due to frequency band characteristics, it relies on earphones to function as an antenna, resulting in inconvenient use and limited experience. Addressing this industry pain point, AWINIC Technology took the lead in 2011 by self-developing a dedicated FM LNA chip. By achieving signal gain to share the built-in antenna, it eliminates the dependence on an earphone antenna, supports native FM loudspeaker playback, optimizes internal space design, and comprehensively improves the shortcomings of traditional FM, earning widespread market recognition.
AWINIC has newly iterated an automotive-grade broadcast LNA product that is compatible with AM/FM/DAB multi-standard reception, providing a high-performance, high-reliability domestic hardware solution for daily in-vehicle radio and emergency broadcasting. Below is AWINIC's recommended LNA selection table:
Table 1 AWINIC Recommended LNA Selection Table
Implementing FM functionality is not complex, but achieving outstanding sound quality and reception experience is quite challenging. To achieve high-performance built-in FM, this functionality must be given high priority during the product definition stage.
The reference design for EASY FM mobile phone applications is as follows:
Figure 1 EASY FM Mobile Phone Application Reference Diagram
01 Core FM Design Considerations
I. To ensure excellent performance of the FM receiving antenna, focus on the following key design aspects:
Case Examples (Antenna Plane):
II. FM has many co-channel interference sources and needs to be kept away from all interference sources, especially LCDs and audio PAs.
1. LCD Interference Issues and Optimization Solutions
FM signal lines should maintain a straight-line distance of more than 6mm from the LCD. Current mobile phones mostly use full-screen designs, which shortens the distance between the LCD and the antenna. LCDs (whether TFT or OLED) generate a large amount of spurious interference signals during operation, which can easily interfere with the main RF and FM reception, thereby reducing reception performance. To effectively reduce LCD interference with the antenna, the following measures should be taken during design:
2. Audio PA Interference Issues and Optimization Solutions
Mobile phones typically use Class D/K audio PAs. Their output signal is a PWM square wave, which generates a large number of harmonic interferences. Therefore, it is recommended to keep the FM antenna more than 15mm away from the audio PA and add EMI filtering components (such as beads or LC inductors/capacitors) at the interference source to suppress the spread of interference (e.g., the FB position in Figure 2). When selecting EMI components, pay attention to the following points:
Figure 2 AW8155B Functional Block Diagram
3. Other Interference: NFC, etc.
When NFC operates, a large portion of its harmonics fall within the FM band, causing interference across the entire FM band. It is recommended to keep the NFC antenna away from the FM antenna.
02 Application Scenarios
III. Typical Application Scenarios: Mobile Phone EASY FM and In-Vehicle Antenna
1. EASY FM in Mobile Phone Applications
AWINIC recommends the following two LC filter circuits as shown below:
Figure 3 Two LC Filter Circuit Diagrams
Table 2 Two LC Filter Solution Tables
a) Recommended priority: 120nH + 22pF parallel LC solution
Because 120nH has a relatively high inductance value, small-package inductors have higher DCR. It is recommended to use large-package, high-Q wire-wound inductors. In practical applications, 0402 package inductors perform better than 0201. This circuit has an insertion loss of only 0.03~0.05dB in the main mobile phone RF band, which is negligible, while presenting high impedance characteristics in the FM band (isolation: -11.5~-18dB), providing excellent isolation.
b) Alternative solution: 68nH + 39pF
If structural packaging limitations prevent the use of 0402 components and the 0201 package lacks a 120nH inductor with low DCR, the 68nH+39pF solution can be substituted. By reducing the inductance value and increasing the capacitance value, the impact of inductor DCR is effectively minimized. This circuit has an insertion loss of only 0.02~0.09dB in the main mobile phone RF band. FM isolation: -7.8~-14.2dB, which is slightly attenuated but sufficient for constrained scenarios.
2. Compatible Earphone Antenna Design
Some customers want to maximize the performance of both the built-in antenna and the earphone antenna. To reduce signal attenuation caused by directly connecting the built-in antenna and the earphone antenna in parallel, AWINIC's AW13412H switch is used to switch the connection between the two antennas and the platform. For differential configurations, a double-pole double-throw (DPDT) switch (AW35742) can be used for switching, as shown in the figure below.
Figure 4 Differential Configuration Diagram
The following shows the measured differences with and without the AW13412 for built-in and earphone antennas:
Figure 5 Difference Comparison Line Chart
2. FM-LNA In-Vehicle Antenna Application
Factors such as natural disasters and geopolitical conflicts can easily cause network disruptions. Countries around the world are increasingly emphasizing the construction of emergency broadcasting, and market demand for in-vehicle antennas and receiving systems continues to grow. Current in-vehicle antenna designs generally require compatibility with AM/FM/DAB multi-standard reception. Following this industry trend, AWINIC has launched the automotive-grade chip AWR15007STR-Q1, which fully supports AM, FM, and DAB all-format broadcast reception, deeply adapting to the digital transformation needs of in-vehicle broadcasting. A typical application scheme is shown in the figure below.
Figure 6 AWR15007STR-Q1 Application Schematic
The overall operating frequency of AM/FM/DAB is relatively low, and the frequency bands are densely arranged. System design needs to balance two core indicators: efficiently suppressing out-of-band interference and improving band isolation, while strictly controlling in-band insertion loss to ensure reception sensitivity. Traditional LC filter circuits are difficult to tune. AWINIC's automotive-grade high-gain broadcast LNA chip AWR15007STR-Q1 can effectively compensate for signal loss caused by LC filtering and optimize reception performance.
In summary, AWINIC's broadcast reception products comprehensively cover two major scenarios: mobile phones and in-vehicle systems. With high integration, excellent RF performance, multi-scenario adaptability, and end-side AI technology, then targetedly resolve industry design pain points. From LNA device selection and electromagnetic interference suppression to filter matching and antenna switching management, AWINIC provides a complete one-stop RF solution. Whether for miniaturized built-in FM design in terminal devices or for AM/FM/DAB digital broadcast upgrade needs in vehicles, AWINIC, with its mature technical expertise and comprehensive product portfolio, ensures stable and reliable broadcast signal reception, helps implement and improve emergency broadcasting systems, fortifies public information communication links in extreme scenarios, and safeguards the critical "lifeline radio waves."
沪ICP备10011954号 |
沪公网安备 31011202011955号
