Kinghelm RF Filter KH-SAWF259A: 2595 MHz SAW Bandpass Filter for Band 41 Mobile Communication

1. Product Background and Functional Positioning

As mobile broadband usage continues to grow, radio-frequency front-end components play an increasingly important role in ensuring stable and efficient wireless communication. In high-frequency and wide-band systems such as TD-LTE Band 41, the performance of the filter directly affects the signal quality, emission compliance, and overall device behavior. The KH-SAWF259A, developed by Kinghelm, is a compact surface acoustic wave (SAW) bandpass filter engineered specifically for this operating band. It is designed for the post-PA (power amplifier) stage, where suppression of unwanted signals is essential.

The device relies on SAW technology, which converts electrical energy into surface acoustic waves on a piezoelectric substrate. By precisely controlling the acoustic path and electrode structure, the filter achieves a specific passband response within a very compact physical footprint. Its stable temperature characteristics, consistent batch performance, and small size make it suitable for radio-frequency designs where both space and electrical performance are critical.

Kinghelm KH-SAWF259A Specification

2. Key Electrical Characteristics

The Kinghelm KH-SAWF259A provides a center frequency of 2.595 GHz and an effective passband of 120 MHz, covering the common operating needs of Band 41 communication equipment. With 50 Ω impedance at both input and output, the filter integrates easily with power amplifiers, front-end modules, and antenna interfaces, simplifying RF matching and reducing system debugging time.

Its insertion loss of approximately 1.8 dB helps maintain signal strength across the passband, supporting good system sensitivity and reliable transmission. The 1 dB passband ripple ensures signal flatness and minimizes distortion. Strong out-of-band attenuation reduces harmonic content and spurious emissions, enabling devices to meet regulatory requirements for wireless transmission.

The device operates reliably from –30 °C to +85 °C, ensuring stable behavior across varied environmental conditions. In addition, KH-SAWF259A complies with RoHS environmental standards, making it suitable for global manufacturing and export.

3. Compact SMD-5P Structure and Design Advantages

The filter is packaged in a 1.1 × 0.9 mm SMD-5P surface-mount form factor, one of the smallest standard sizes for SAW filters. This compact design greatly reduces PCB area requirements and is particularly advantageous for slim and highly integrated devices such as smartphones, wireless modules, and portable terminals.

The lightweight construction—only 0.01191 g per piece—supports products that require strict weight control. The filter is supplied in tape-and-reel packaging (10K/TR) for high-speed SMT assembly, improving production efficiency and mechanical reliability.

Internally, the device uses tightly controlled SAW structures with high consistency in electrode spacing, acoustic path geometry, and material thickness. This precision ensures stable center frequency characteristics and consistent temperature behavior across production batches, which is important for mass-market communication devices.

4. Application Areas and Practical Use

The primary use scenario for the KH-SAWF259A is as a post-PA filter in Band 41 cellular systems, where it removes unwanted harmonics and adjacent-band interference generated after power amplification. In modern RF designs, PA output stages often exhibit strong out-of-band components, and the performance of the filter determines the emission purity and whether the final product meets communication standards.

Typical applications include:

• Mobile phones operating on TD-LTE Band 41

• RF front-end modules (FEM) requiring Band 41 filtering

• CPE (Customer Premises Equipment) and MiFi devices

• Wireless broadband terminals

• 4G/TD-LTE communication modules

• Portable Internet devices and handheld communication terminals

• Other RF systems requiring a compact 2.5–2.7 GHz bandpass SAW filter

Because of its stability and small footprint, the KH-SAWF259A may also be used in IoT terminals, wireless modems, and custom RF modules requiring wideband filtering in the 2.6 GHz range.

5. Performance Strengths and Manufacturing Reliability

Kinghelm ensures that the KH-SAWF259A is produced with strict process control to maintain consistency across all electrical parameters. Its SAW architecture is optimized to reduce frequency drift, improve mechanical durability, and maintain the integrity of the acoustic structure under thermal cycling.

The filter demonstrates:

• Stable center frequency performance

• Controlled temperature coefficient for reliable operation

• Uniform insertion loss characteristics across production batches

• Solid mechanical resistance to vibration and thermal stress

• Compliance with global environmental regulations

These capabilities make the filter suitable for long-term deployment in mass-market communication products, where consistency and reliability are essential.

Kinghelm KH-SAWF259A Product Image

6. Summary

The Kinghelm KH-SAWF259A is a compact and stable 2595 MHz SAW bandpass filter designed for Band 41 mobile communication systems. Its combination of small form factor, stable passband response, low insertion loss, 120 MHz usable bandwidth, and robust environmental characteristics makes it well-suited for smartphones, wireless modules, broadband terminals, and various RF front-end designs. By providing effective suppression of unwanted PA output components, it helps ensure clean transmission and reliable system performance in demanding wireless environments.

About Kinghelm

Shenzhen Kinghelm Electronics Co., Ltd.（www.kinghelm.net）has technical backbones from Tsinghua University and UESTC, and has introduced overseas returnee professionals. Kinghelm is able to develop highly reliable and high-performance antenna and connector products.KH series products of "Kinghelm" brand include Beidou/GPS antennas, RF adapter connectors, plug connector, electrical data connectors, terminals, and customized vehicle harnesses, industrial / medical connectors, and special antenna connectors."Kinghelm connects world", Kinghelm has grown with the development of China's Beidou industry. Starting from supplying Beidou/GPS dual mode antennas, IPEX terminals, and RF adapter cables for automotive manufacturers, Kinghelm has continuously developed products. Currently, it has a series of WiFi, Bluetooth, NB-loT, LoRa, Zigbee, UWB, and GSM antennas, RFID tags, RF adapter cables, standard microwave antennas, vehicle grade SMA, SMB, FAKRA holders, coaxial cables, and can customize non-standard antenna connectors based on customer drawings or samples.