Wideband data conversion and signal processing
Data conversion has existed since the early days of electronics.
Data conversion refers to the process of transforming data from one format, structure, or representation into another. This can involve converting data between different types, such as analog to digital or vice versa, or changing the format of digital data from one encoding or file type to another. The goal of data conversion is often to enable compatibility between systems, enhance data usability, or facilitate efficient storage and transmission.
Serving as a crucial link between the analog and digital worlds, converters are now widely present in most applications, playing a significant role in digitizing an increasing number of fields such as audio, video, communications, measurement, and industrial control.
Along with resolution, the sampling rate is one of the key characteristics of conversion components.
By defining the number of samples per second, the sampling rate determines a converter’s ability to observe high frequencies, directly influencing its bandwidth.
This principle is expressed in the well-known Nyquist-Shannon sampling theorem, as noted below: 
Where B is the bandwidth and fs is the sampling rate in Hz.
Improvements in conversion techniques have led to an increase in bandwidth, with the capability to reach several tens of gigahertz for the most advanced ADC and DAC components.
These advancements offer new opportunities for system architecture, benefiting both wideband applications, which can leverage the enhanced bandwidth, and narrowband applications through the adoption of direct sampling.
Wideband applications
Several applications have their performance closely tied to the width of the bandwidth. For instance:
- Telecommunication systems’ data rates and quality of service
- Primary radar resolution and sensitivity
- Analysis and detection capabilities of electronic warfare systems
In this context, increasing the sampling rate can expand the system’s bandwidth, directly enhancing overall performance.
Moreover, in wideband applications, it’s common to use multiple converters covering distinct frequency ranges. Expanding each converter’s band can reduce the number of channels needed while maintaining equivalent performance. This directly impacts the size, weight, power, and cost (SWaP-C) of equipment.
Figure 2: Reducing the number of channels using wideband ADCs
Direct Sampling vs. Intermediate Frequency Sampling
The analog frequencies used depend on the applications. One example is the HF band from 3 to 30 MHz, allowing long-distance communications beyond the horizon, commonly used in maritime communications and over-the-horizon radars. Another example is the X band from 8 to 12 GHz provides a good balance between beam resolution and atmospheric penetration, making it widely used in embedded radars.
For many applications, the conventional method involves converting the analog signal to a lower intermediate frequency before being sampled by a converter. This method is known as Intermediate Frequency (IF) sampling.
Increasing sampling rates allows for direct sampling of the RF signal without the need for additional RF conversion stages, even for signals in the tens of GHz range. This approach is known as direct sampling.
Figure 3 : Removing RF conversion stages using direct sampling
The advantages of direct sampling include:
- Simplification of the system architecture by removing RF conversion stages.
- Flexibility through the use of digital signal processing, which can easily adapt to various missions.
- Scalability through software updates without the need for hardware modifications.
FPGAs: Optimal Solution to Growing Demand for Processing Power
An increase in digital bandwidth results in a higher flow of information, leading to an increased demand for computing power to process larger and larger data streams in real time.
Massively parallel architectures, such as multi-core processors, GPUs or FPGAs, become essential in addressing these challenges.
Excelling in handling analog signals and multiple ADCs within systems, FPGAs ensure real time processing with precision. Their adaptability to diverse input types, efficient noise and error management, and dynamic circuitry make FPGAs a technology of choice for optimizing speed rates and processing. In the ever-evolving landscape, FPGAs emerge as a transformative circuitry type, providing unparalleled processing power and versatility.
In this context, FPGAs emerge as an optimal solution, particularly in the field of embedded applications. Their processing capability, flexibility, high level of integration, and energy efficiency make them key components in current wideband analog-to-digital conversion systems.
apissys Expertise
The design of embedded solutions combining wideband data conversion capabilities and processing power is at the core of apissys’ expertise for the past 15 years.
By combining recognized expertise in complex board design, implementation of high-end FPGAs, and a deep understanding of wideband converters, apissys is able to provide optimal data conversion and processing solutions, consistently at the leading-edge of innovation.
In the field of signal processing and converters, precision is crucial. Our advanced technologies include FPGA-driven architectures for direct sampling and high-speed data conversion. We use sophisticated ADCs to ensure excellent dynamic range, frequency response, and minimal noise interference in processing digital signals. Our focus is on creating circuits that are both high-speed and accurate. Whether you’re dealing with transformative signal processing or implementing cutting-edge converters, our solutions showcase top-notch technical expertise. Explore how we navigate the complexities of signal processing and conversion with a blend of innovation and technical know-how.