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 functions in portable products has become very common, especially in mobile phones, which is basically a standard.
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In general, the FM antennas of these products are mostly made with the ground wire of the earplugs. One of the shortcomings in the use of people is that the earplug antenna is very inconvenient to carry, and many people are reluctant to carry it, so that the benefits of FM radio are not fully utilized. Because of this, the built-in antenna inside the product is bound to 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 are generally more than 1m in length, which is about to meet the needs of the radio frequency band. A very short antenna, even if it is resonated by loading, has the disadvantage of degrading performance. Not to mention that portable products are extremely limited in length due to size. Therefore the following problems are difficult to avoid:
1. The antenna will be too unacceptable due to the effective length being too short and the gain being too small;
2. After adding the sense of resonance, it becomes a narrow-band resonance, and its bandwidth is far from meeting the demand of the FM band.
Most of the existing FM internal antenna products on the market use short-circuit or ceramic antennas to directly replace the original ear-plug antennas. The above mentioned problems are not well solved, so the following shortcomings are common:
1. The system receiving sensitivity is poor and the station is rarely received;
2, the direction is very strong, the reception is unstable during the movement;
3, susceptible to human influence;
4. The effective bandwidth is not enough, resulting in a wide gap between different frequency points.
solution
In response to the shortcomings of the current program, Shiqiang Telecom has introduced a well-designed high-performance built-in antenna FM system solution.
The scheme applies a number of unique signal processing methods such as tracking tuning and bandwidth widening technology, and based on a small and small square antenna, the overall effect is greatly improved. Its directionality, human hand effect, mobile interference, and performance flatness of each frequency point in the band have made extraordinary achievements. It can almost match the effect of the earbud antenna. And because the antenna uses a regular shape, compared with some special-shaped wire antenna solutions on the market, the requirements of the structural design of the Shiqiang telecommunications solution are greatly reduced, and the development time is greatly reduced. Its main features are:
1. Tracking and tuning function is adopted. For the narrow bandwidth of the short antenna, tracking tuning is used to improve the flatness, which can greatly improve the overall effect. As shown in Table 1
Figure 3 tracking tuning effect diagram
Table 1 Comparison of tracking tuning effects
2. Under the premise of selecting the appropriate antenna, use special processing to seek adjustment to broaden the bandwidth of the antenna itself. Reduce the loss of antenna gain.
3. Good signal processing circuit, greatly improving the sensitivity of the system.
4, a variety of system design skills to improve human body interference, directional and other issues.
5, the use of small-sized antennas, the smallest size to 23 * 4 * 2mm, is conducive to design and assembly, low cost.
From the theoretical analysis and test results, compared with the current market plan, the effective sensitivity of Shiqiang Telecom's solution has 10~15dB improvement at most frequency points, and can receive more effective stations. It can be seen from Table 2 that the performance of Shiqiang Telecom's solution is far superior to that of N and M companies, so it is highly praised in the industry.
Table 2 Qualitative comparison with current programs
It is reported that this program has been verified by actual mass production, and the customer response is very good. For customers adopting this solution, Shiqiang Telecom will provide relevant circuit diagrams and other related materials, design suggestions and technical support services for follow-up.
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