Tinned Copper Clad Copper TCCC Corrosion-Resistant Copper-Clad Tinned Wire,Copper-Clad Copper Tinned Wire Production,Copper-Clad Copper Tinned Wire Processing,Copper-Clad Tinned Wire changzhou yuzisenhan electronic co.,ltd , https://www.ccs-yzsh.com
An adaptive fundamental frequency filter for RFID readers
Radio Frequency Identification (RFID) is an automatic identification technology that allows the recognition of objects equipped with a coded tag. In UHF RFID systems, a reader sends out an RF signal in the 860MHz to 960MHz range and communicates with a passive tag. The tag draws all its power from the continuous wave (CW) signal sent by the reader and responds by modulating the reflection coefficient of its antenna, backscattering the data signal back to the reader.
To detect the volume signal, the system measures the time interval between signal transitions, where a "1" symbol has a longer duration than a "0". The reader initiates the process by sending a signal specifying the backscatter data rate and encoding format of the tag. RFID readers are designed to function in noisy environments where multiple readers operate in close proximity. Depending on the setup, they can operate in single, multi, or dense interrogator modes, each affecting the spectral characteristics of the signals.
The programmable RFID reader includes advanced components such as a high linearity direct conversion I and Q demodulator, low noise amplifiers, a dual-channel fundamental frequency filter with variable gain and bandwidth, and a dual-channel ADC. These features ensure reliable performance and efficient data processing.
The LTC6602 is a dual-channel bandpass filter that offers matched gain control and precise frequency tuning. Each channel maintains a phase shift within ±1 degree, ensuring accurate signal processing. The internal or external frequency determines the passband, while the corner frequencies and bandwidth are set through scaling ratios. For example, with an internal frequency of 90MHz and scaling ratios of 6000 and 600, the filter provides a fourth-order elliptical response that suppresses out-of-band noise effectively.
This programmable filter is ideal for software-defined UHF RFID readers, offering flexibility in adjusting gain and bandwidth via SPI control. It supports backscatter links ranging from 40kHz to 640kHz and data rates from 5kbps to 640kbps. The internal frequency is set using an 8-bit DAC, allowing precise control over the operating frequency range. Software algorithms further optimize the filter settings based on data rate, encoding, and environmental conditions.
In practical applications, the filter’s low-pass cutoff frequency must be set to match the shortest pulse interval, while the high-pass cutoff should remain below the longest interval to avoid distortion. Adjusting these settings helps maintain signal integrity while minimizing noise. For instance, a 10kHz high-pass setting may provide sufficient signal resolution for detecting symbol sequences, even in the presence of background noise.
Overall, the LTC6602 is a compact, high-performance IC housed in a 4mm x 4mm QFN package. It can be controlled via parallel or serial interfaces, making it suitable for a wide range of RFID applications. Whether used in single or multi-interrogator setups, the LTC6602 ensures optimal signal detection and reliable data transmission in complex environments.