Circuit Note

CN-0523

analog.com

Circuits from the Lab™ circuits from Analog Devices have been designed and built by Analog Devices

engineers. Standard engineering practices have been employed in the design and construction of each circuit,

and their function and performance have been tested and verified in a lab environment at room temperature.

However, you are solely responsible for testing the circuit and determining its suitability and applicability for

your use and application. Accordingly, in no event shall Analog Devices be liable for direct, indirect, special,

incidental, consequential or punitive damages due to any cause whatsoever connected to the use of any

Circuits from the Lab circuits. (Continued on last page)

Rev. 0 | 1 of 8

Circuits from the Lab

® reference designs are engi-

neered and tested for quick and easy system integra-

tion to help solve today’s analog, mixed-signal, and

RF design challenges. For more information and/or

support, visit www.analog.com/CN0523.

Devices Connected/Referenced

HMC407

5 GHz to 7 GHz RF Power Amplifier

ADT6401

2.7 V to 5.5 V, Pin-Selectable Temperature Switch

LT8364

Low IQ Boost/SEPIC/Inverting Converter with 4 A, 60 V Switch

ADM7150

800 mA, Ultralow Noise/High PSRR LDO

ADM7171

6.5 V, 1A, Ultralow Noise, High PSRR, CMOS LDO

USB-Powered, 5.8 GHz RF Power Amplifier with Overtemperature Management

EVALUATION AND DESIGN SUPPORT

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Circuit Evaluation Boards

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CN0523 Circuit Evaluation Board (EVAL-CN0523-EBZ)

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Design and Integration Files

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Schematics, Layout Files, Bill of Materials

CIRCUIT FUNCTIONS AND BENEFITS

The International Telecommunication Union allocates the unli-

censed 5.8 GHz industrial, scientific, and medical (ISM) radio

frequency band for worldwide use. Advancements in wireless tech-

nologies and standards, as well as minimal regulatory compliance

requirements, have made this frequency band popular for short

range, wireless communication systems.

One popular application for the 5.8 GHz frequency band is Wi-Fi,

where its 150 MHz channel bandwidth accommodates up to 24

non-overlapping Wi-Fi channels. While its transmission range is

shorter than that of the 2.4 GHz frequency band, its higher per

channel bandwidth makes it suitable for short distance, high data

rate communication applications.

Other common uses can be found in software defined radio,

wireless access points, public safety radio, wireless repeaters,

femtocells, wireless broadband communication such as in 4G long

term evolution (LTE) and worldwide interoperability for microwave

access (WiMAX), and base transceiver station infrastructures.

In any radio transmission application, a high gain amplifier is

required to drive the antenna. This can be implemented in one

or more stages depending on the application requirements, with

higher output power values extending the range of the RF transmis-

sion. To achieve the optimal performance, several factors must be

considered in the design, such as proper impedance matching,

noise figure, frequency response, power management, and thermal

management.

The circuit shown in Figure 1 is a two-stage, RF power amplifier

optimized for transmit signal chains operating in the 5.8 GHz ISM

band. The circuit has a gain of approximately 24 dB and an input

return loss of approximately 11 dB at the center frequency. The RF

input and output ports are designed with a 50 Ω impedance match,

enabling direct connection between the circuit and standard 50 Ω

systems.

To prevent overheating, a temperature monitoring switch circuit

disables the RF amplifier when the user-defined temperature trip

point is reached. This switch circuitry also automatically enables the

amplifier when the temperature falls below the hysteresis set point.

Figure 1. CN0523 Simplified Block Diagram