Analysis of building module strategy based on implementing faster RF design

Driven by the growing popularity of the Internet of Things (IoT), we live in an increasingly connected world where electronic design needs to provide ubiquitous wireless communications. From wearables to smart appliances, the range of integrated RF applications is rapidly expanding. Therefore, the standard number of such radio links (airborne wireless interfaces) is also rapidly increasing. In addition, there are traditional RF markets such as wireless data, satellite communications, aerospace and maritime, as well as other applications in science, medical and industrial.

Even for ubiquitous 2.4 GHz wireless applications such as Wi-Fi and Bluetooth, the lower radio spectrum is still very active due to the diversity of HF, VHF and UHF systems, some of which occupy the frequency bands previously used for terrestrial broadcasting. In the face of the need to integrate RF functions in new product designs, and taking into account the increasing time-to-market pressures, many engineers are finding this task increasingly daunting. Traditional methods of designing with discrete solutions will soon be abandoned, but electronic design still needs to meet the strong demand for connectivity.

To help solve this problem, RF designers need to find help from silicon radio suppliers who design, develop and deliver low-power analog, digital and mixed-signal semiconductor solutions for global telecommunications systems. In addition, they offer a range of modular building blocks that can be used as part or all of the "wireless front end".

In summary, these devices are high-flexibility, high-performance ICs for HF / VHF / UHF designs, enabling engineers to build RF designs using a modular approach that uses versatility, low power, and good support. RF IC devices to speed up the design process.

RF design and application challenges

Designing RF circuits can be very challenging. Some engineers prefer to use discrete devices to create designs. However, this approach is not appropriate given the rapid commercial pressures that require the lead in bringing products to market ahead of the competition. These factors are driving major changes in wireless applications.

Wireless networks are evolving toward higher data rates and higher capacities, and applications such as Wi-Fi and Bluetooth are among them, and this is one of the main driving forces in the semiconductor industry. This kind of performance presents many challenges to current design techniques, especially the demanding requirements for (super) low power consumption. The rapid growth of wireless services has led to an increasing demand for highly integrated and low-cost solutions, and the fast-growing market and fierce competition require very short system development cycles. In response to this trend, the adoption of new design methods for wireless systems has become a top priority.

Based on a platform-based design, the industry has developed a new design approach that is better than traditional approaches using discrete RF devices. It uses a higher level of abstraction, building blocks, better reusability, and system Early consideration of performance.


A good example of this is the wireless receiver design, a complex system of RF, analog, and mixed-signal components. Traditionally, system design and discrete circuit design have been performed separately. However, with the building block design approach, several challenges in wireless receiver design have been well coordinated.

Headquartered in the UK, CML Microcircuits is a global leader in providing RF building block solutions that are ideally suited for a wide range of systems. The following figure (Figure 2) shows an example of a typical system architecture with a highly integrated implementation: Digital/Analog Two-Way Radio (TWR), Wireless Data (WD) Telemetry, and Software Defined Radio (SDR).

The building blocks in these designs usually include the following elements:

Receiver (Rx) - Design considerations include the distribution of RF, intermediate frequency (IF), and baseband (BB) electronics gain.

Transmitter (Tx) - An RF transmitter performs modulation, upconversion, and power amplification.

Transceiver (XCVR) - a combination of the two.

Power Amplifier (PA) - RF power amplifiers are a key factor in achieving performance, reliability and acceptable cost.

Mixer - A frequency conversion device with two main functions:

Convert the RF frequency to an intermediate frequency (IF) or baseband.

Convert the BB or IF signal to a higher IF or RF for transmission.

Local Oscillator (LO) - Oscillation occurs when the amplifier has a feedback path that satisfies the amplitude and phase conditions. A voltage controlled oscillator (VCO) can be used as part of a programmable phase-locked loop (PLL) to tune the LO in a given frequency range.


CML Microcircuits' building block approach to RF design

It would be advantageous to be able to implement an RF design solution using existing commercial devices. CML's CM97x and CM99x family of devices includes an integrated receiver, transmitter, transceiver, modulator/demodulator and PLL capabilities to speed design and reduce time-to-market. The main performance summary of the device is as follows:

CMX971 - This is a high performance quadrature modulator with a wide frequency operating range. Control of the CMX971 can be implemented via a serial bus or direct control. Programmable features include the LO divider divider ratio (2 or 4) and optimized operation (for noise or linearity).


Figure 3: Typical system application using the CMX971 quadrature demodulator, CMX970 IF/RF quadrature demodulator, and CMX983 programmable baseband interface IC.

CMX975 - This is an IC that extends the frequency range of CML RF building blocks with multiple functions: RF PLL/VCO, IF PLL/VCO, transmit upconverting mixer, receive downconverting mixer and low noise amplifier (LNA). The RF HF synthesizer features a fractional-N design with a fully integrated internal VCO or an external VCO up to 6 GHz operating at up to 3.6 GHz. The IF synthesizer features an integer-N design with an operating frequency of up to 1 GHz. It has an integrated VCO that requires only one external inductor to set the frequency. The Rx mixer can be configured for image rejection or normal mode, while the Tx mixer can be configured for sideband suppression or normal mode. The integrated LNA provides a gain reduction of 18 dB in three steps.


Figure 4: The CMX975 is designed to work with CML's CMX973 quadrature modulator/demodulator to provide a simple, cost-effective, high-frequency super transceiver operating from 1 to 2.7 GHz.

CMX99x – Includes CMX991 Quadrature Transceiver, CMX992 Quadrature Receiver, CMX993/993W Quadrature Modulator, CMX994A/E Direct Conversion Receiver and CMX998 Cartesian Feedback Loop Transmitter. Operating over the RF frequency range of 100 MHz to 1 GHz, the CMX993/993W and CMX998 operate at frequencies as low as 30 MHz for maximum flexibility. These ICs can be used alone or in combination to meet the constant-envelope and many wireless format requirements in data and coded voice operations in linear modulation systems. To save on PCB costs, these products require a minimum of external circuitry and are available in a compact VQFN package. To achieve the shortest design integration time, the CMX99x family of products has off-the-shelf evaluation and demonstration aids and a range of application information support.


Figure 5: Application example for a combined design using the CMX971 and CMX994A/E.

in conclusion

The use of building blocks or modular methods for RF design has the following key advantages and benefits compared to solutions using discrete components and circuits:

Short design cycle.

Faster time-to-market and shorter product profitability.

A simpler test is required to complete the design.

Fewer components are required to complete the design.

Achieve higher reliability.

With higher performance.

Better control of tolerance redundancy.

Achieve lower cost end products.

While the use of discrete components in most cases can provide a higher degree of flexibility for certain applications, the integrated building blocks can achieve some (or all) of the advantages listed above. The technologies and products offered by CML are well suited for this RF design approach.