How to achieve the system-level goals of low BER (bit error rate), low spurious output, and low phase noise

Combining low phase noise, advanced functionality, and ultra-small size, ADI’s PLL products with integrated VCOs are ideal for many small form factor applications such as microwave/millimeter wave radios, test equipment, microwave sensors, fiber optic communications, and defense communications and sensors. Ideal.

Emerging PLL + VCO (Phase Locked Loop Integrated Voltage Controlled Oscillator) technology enables rapid development of low phase noise frequency synthesizers for cellular/4G, microwave radio defense and other applications, ADI’s integrated frequency synthesizer products cover frequencies from 25 MHz to 13.6 GHz.

Radio designers in cellular/4G, microwave radio, test equipment, and defense subsystem applications rely on high-quality local oscillators (LOs) to achieve system-level goals of low BER (bit error rate), low spurious output, and low phase noise. All RF and microwave communication and sensor systems, whether based on analog or digital modulation, require a clean LO signal source; the higher the capacity of the radio, the higher the LO signal requirements.

There are many different architectures available, but one of the most common ways to generate a stable LO source is to combine a low phase noise voltage controlled oscillator (VCO) with a stable reference and phase locked loop (PLL) to form a frequency synthesizer. However, designers seeking optimal LO performance are bound to face the many challenges associated with the interaction between the PLL/frequency synthesizer, VCO, charge pump, and loop filter, not to mention those due to board layout and poor power supply noise. The problem.

ADI’s core expertise is in frequency generation components such as MMIC VCOs, phase locked oscillators (PLOs), low noise prescalers, phase frequency detectors (PFDs) and a range of dual-mode RF input frequencies up to 13.6 GHz (fractional/integer) PLL/frequency synthesizer ICs.

As shown in the functional block diagram of Figure 1, these products implement advanced fractional-N frequency synthesizers and ultralow noise VCOs in standard 5 mm × 5 mm and 6 mm × 6 mm QFN plastic packages; this high level of integration maximizes ground to reduce external component count. Designed for ultra-low phase noise commercial and defense applications, it includes a very low noise phase frequency detector (PFD), a precision-controlled charge pump, and an advanced modulator design that provides ultra-fine frequency stepping.

Figure 1. Functional block diagram and typical application circuit of ADI’s PLL product with integrated VCO

Architecture has ultra-low close-in phase noise and low spurs for wider loop bandwidth and faster frequency hopping and low microphonic; spurious outputs are low enough to eliminate the need for expensive direct digital in many applications Frequency Synthesis (DDS) Reference Reference.

PLL with integrated VCO for RF market applications

The HMC830LP6GE is one of eight integrated VCO wideband PLL products for cellular/4G, microwave backhaul IF, and test and measurement applications. Each product in the family combines a high-performance fractional-N PLL/frequency synthesizer with a low-noise VCO. The PLL architecture of the integrated VCO for RF applications enables high-performance VCOs to be tuned below five volts (see Figure 2).

Figure 2. Tuning Voltage vs. Frequency for PLL HMC830LP6GE with Integrated VCO

Op amps are no longer required in the loop filter, saving cost and board space while improving performance. PLL with integrated VCO can lock to one extreme temperature and then operate over the full temperature range without relocking or recalibration; a feature required in high reliability applications but not available in some other competitors this function.

As shown in Figure 3, these devices have excellent phase noise performance, typically 10 dB better than the competition in both in-band and far-end noise floors, all without the need to choose between low-spurious or low-noise modes. The integrated noise from 100 Hz to 1 MHz is typically –55 ​​dBc, equivalent to 0.1° of rms jitter, or 278 fs rms at FOUT = 1 GHz.

Figure 3. SSB Phase Noise vs Offset Frequency for PLL HMC830LP6GE with Integrated VCO

As shown in Figure 4, the HMC830LP6GE offers a clear improvement over alternative integrated solutions.

Figure 4. Worst Spur, Fixed 50 Mhz Reference, Output Frequency = 2 GHz

The temperature range performance of the HMC830LP6GE at the edge of the band is stable, ensuring that there is no “dropout”.

For example, the HMC830LP6GE produces about 5 dB close-in phase noise and 7 dB phase noise floor at offset frequencies greater than 20 MHz, both of which are low compared to the TI LMX2581. In addition, HMC830LP6GE also provides superior spurious performance, with much lower fractional spurs in the entire frequency band, and the entire spectrum output is cleaner.

The ADF5355’s integrated VCO’s PLL covers the widest spectrum in its class from 55 MHz to 13.6 GHz, while the ADF4355-2’s frequency range is 55 MHz to 4.4 GHz. Both devices integrate an ultra-low phase noise VCO, producing –138 dBc/Hz (1 MHz offset) phase noise at 3.4 GHz for the ADF4355-2 and –132 dBc/Hz (1 MHz offset) at 6.8 GHz for the ADF5355. MHz offset) phase noise.

The ADF5355 and ADF4355-2 feature a new VCO topology and architecture and utilize ADI’s patented advanced SiGe-BiCMOS process during development, resulting in excellent VCO phase noise performance. In ultra-wide bandwidth RF and microwave communication applications, this ultra-low phase noise has the advantage of improving the overall system bit error rate and data throughput rate, providing better noise immunity and wider dynamic range.

ADI’s cost-effective, ultra-wide bandwidth PLL frequency synthesizer ICs also feature up to 125 MHz phase comparator frequencies and 38-bit resolution to reduce jitter and allow for extremely fine step sizes, compared to discrete GaAs deployments using Integrated PLLs and VCOs in advanced BiCMOS process dramatically reduce package size and power consumption. Additionally, because a single PLL frequency synthesizer can be configured from 55 MHz to 13.6 GHz, designers can reconfigure their system designs more quickly and reduce device inventory while still supporting multiple bands.

PLL with integrated VCO for microwave market applications

The PLL HMC764LP6CE with integrated VCO has been optimized for narrowband, high performance microwave communication applications. Analog Devices is the first in the industry to offer integrated PLLs and VCOs at frequencies above 6 GHz. These products add the capabilities of an integrated advanced fractional frequency synthesizer to ADI’s outstanding microwave VCO performance. Typical applications include microwave and millimeter-wave radios, industrial/medical test equipment, defense communications, and Electronic countermeasures (ECM) subsystems.

As shown in Figure 5, the HMC764LP6CE has stable tuning sensitivity and up to 16 dBm output power over its bandwidth, making it ideal for directly driving many ADI high linearity, double-balanced and I/Q mixers as well as upconversion and downconversion The LO part of the inverter product.

Figure 5. Tuning Sensitivity and RF Output Power vs. Output Frequency for PLL HMC764LP6CE with Integrated VCO

Figure 6 shows the excellent single-sideband (SSB) phase noise performance of the HMC764LP6CE versus offset frequency for the low, mid, and high frequency ranges. This data was measured with a reference frequency of 50 MHz, a loop bandwidth of 100 kHz, and a comparison frequency of 50 MHz for the PFD. Due to the monolithic structure, phase noise performance is stable over temperature and under mechanical shock conditions. In addition, the built-in FSK mode allows the device to be used as a simple low-cost direct FM emission source.

Figure 6. SSB Phase Noise vs Offset Frequency for PLL HMC764LP6CE with Integrated VCO

Even with such advanced features and high level of integration, developing a high-performance programmable LO still requires significant design time. Therefore, ADI has developed a PLL reference designer kit with integrated VCO, allowing immediate measurement of the design at hand.

The typical evaluation PCB shown in Figure 7 is part of an easy-to-use, general-purpose evaluation kit that minimizes design time and facilitates rapid prototyping. The reference designer kit includes an on-board reference oscillator and voltage regulators, and supports common loop filter configurations.

Figure 7. PLL evaluation PCB with integrated VCO, included in each designer kit

Using the included software, users can program the PLL and access its advanced features. The full how-to guide provides step-by-step instructions for the user to quickly power up and initialize the evaluation board. This guide provides a comprehensive discussion of the components used within the evaluation board, covering topics such as reconfiguring the evaluation board for an external reference voltage, and implementing an on-board selectable sequential passive or active loop filter.

Each reference designer kit includes ADI’s proprietary ADIsimPLL design tool, allowing users to evaluate PCB loop filters according to their own application-specific custom criteria. Comprehensive PC-based PLL control software is provided, and the PLL can be programmed with a PC-compatible register file via the USB interface. The user can evaluate a fully locked LO in a very short time with just a PC, a signal analyzer, and a few DC power supplies. ADI’s team of skilled application engineers can also help customers quickly become familiar with this unique product.

ADI’s PLL products with integrated VCOs combine low phase noise, advanced functionality, and ultra-small size, making them ideal for many small form factor applications such as microwave/millimeter wave radios, test equipment, microwave sensors, fiber optic communications, and defense communications and sensors .

Hybrid frequency synthesizers typically use a fiberglass substrate material with a discrete VCO, a large resonator, and a stamped metal cover. This assembly technique can cause RF grounding-related problems in the user’s system, as well as nuisance electrical and microphonic coupling effects.

Compared to discrete hybrid synthesizer/VCO configurations, ADI’s integrated frequency generation solutions help designers achieve stable performance, high reliability, and small size.

The resonators of ADI’s integrated VCO PLLs are also much smaller compared to larger hybrid designs, resulting in excellent microphonic performance.

These PLL products with integrated VCOs are available in RoHS-compliant QFN leadless packages, ideal for high-speed, high-volume SMT assembly lines.

The Links:   ACS755LCB-050-PFF BSM300GB60DLC