High-performance FM built-in antenna solution
With the continuous advancement of technology, electronic components are becoming more and more integrated, which greatly stimulates the versatility and miniaturization of portable products. The use of FM radio function in portable products has been very common, especially in mobile phone products is basically a standard.
Generally speaking, the FM antennas of these products are mostly made with earplugs ground wire. People have a disadvantage during use, that is, the earplug antenna is very inconvenient to carry, so many people are unwilling to carry it, so that the benefits of FM radio cannot be fully exerted. It is for this reason that the built-in antenna in the product must become the future development direction.
Built-in FM antenna is a technical problem
Technically speaking, it is very difficult to internalize the FM radio antenna. The earplugs generally have a length of more than 1m, which just meets the needs of the radio frequency band. Even if the short antenna is resonated by loading, it will bring the disadvantage of degraded performance. Not to mention the limited effective length that portable products can provide due to size. Therefore, the following problems are difficult to avoid:
1. Because the effective length of the antenna is too short and the gain is too small, the radio effect will be unacceptably bad;
2. After the resonance is added, it becomes a narrow-band resonance, and its bandwidth is far from meeting the requirements of the FM frequency band.
Most of the existing FM internal antenna products on the market now use short-line or ceramic antennas to directly replace the original earbud antennas, and the above-mentioned problems have not been solved well, so there are generally the following deficiencies:
1. The system has poor receiving sensitivity and few receiving stations;
2. The direction is very strong, and the reception is unstable during movement;
3. Easily affected by the human body;
4. Insufficient effective bandwidth leads to a wide gap between different frequency effects.
solution
In response to the shortcomings of the current scheme, Shiqiang Telecom has launched a carefully designed high-performance built-in antenna FM system scheme.
The program uses tracking and tuning, bandwidth widening technology and other unique signal processing methods, based on a small volume and small square antenna, the overall effect is greatly improved. Its directivity, human hand feeling effect, movement interference, performance flatness of each frequency point in the band have extraordinary performance. Almost comparable to the effect of earplug antennas. And because of the regular shape of the antenna, compared with some special-shaped wire antenna solutions on the market, the requirements for the structural design of the Shiqiang Telecom solution are greatly reduced, and the development time is also greatly reduced. Its main features are:
1. Adopt tracking tuning function, aiming at the reality that the bandwidth of short antenna is narrow, using tracking tuning to improve the flatness can greatly improve the overall effect. As shown in Table 1
2. Under the premise of selecting an appropriate antenna, special treatment is used to seek adjustments to widen the bandwidth of the antenna itself. Reduce the loss of antenna gain.
3. A good signal processing circuit greatly improves the sensitivity of the system.
4. A variety of system design techniques to improve problems such as human interference and directionality.
5. Use regular small-volume antennas with a minimum size of 23 * 4 * 2mm, which is conducive to design and assembly and low cost.
From the theoretical analysis and test results, compared with the current market plan, the effective sensitivity of the Shiqiang Telecommunications Plan has been increased by 10 ~ 15dB at most frequency points, and it can receive more stations with better results. It can be seen from Table 2 that the performance of Shiqiang's telecommunications solution is much better than that of the corresponding mobile phones of N company and M company, so it is highly praised in the industry.
It is reported that this program has been verified by actual mass production, and customers have responded well. For customers who adopt this solution, Shiqiang Telecom will provide relevant circuit diagrams and other materials, related component design opinions and follow-up technical support services.
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