Benchtop and USB-Powered Amplifiers Serve Measurement Applications

by Tim Galla, Product Manager, Active RF/Microwave Components, Pasternack Enterprises

Among the broad array of tools used by designers for stimulating and measuring the performance of their creations, benchtop amplifiers are some of the most basic and useful. Over the last few years, they’ve been joined by very small amplifiers that take advantage of USB for both DC power and connectivity. This makes them well suited for use in the field when a simple stimulus source rather than a full-featured and more expensive amplifier is all that’s needed. Pasternack recently added a quartet of benchtop amplifiers and two USB amplifiers that combine extremely broad bandwidths with high gain and low noise figures along with rugged construction. The USB powered amplifiers are complemented by attenuators and switches that cover more or less the same frequency ranges. High-Performance Benchtop Amplifiers Benchtop amplifiers for measurement applications must maintain the characteristics of the input signal, adding or subtracting nothing from it to ensure the integrity of the output. Benchtop amplifiers are hardly unique among amplifiers in this regard, but in a measurement environment in which performance benchmarks are set, it is essential.

The new benchtop amplifiers include the PE15A3500 (1 to 20 GHz), PE15A3501 and PE15A3502 (20 to 40 GHz), and the PE15A3595 (1 to 40 GHz) shown in Figure 1. They have different levels of gain and P1dB RF output power of +10 dBm (+22 dBm for the PE15A3595). Detailed specifications for all models are shown in Table 1. The amplifiers dispense with external control interfaces and other accoutrements, providing only an on-off switch and power cord. All but the PE15A3500 have 2.92-mm input and output connectors; the PE15A3500 employs SMA female connectors.

The broad bandwidths of the amplifiers allow them to be used in almost any measurement environment, and the PE15A3595 extends this frequency range to cover virtually all frequencies likely to be encountered when testing systems designed for defense applications as well as microwave radios cellular backhaul applications, and many other systems as well. The plot in Figure 2, which shows small-signal gain versus frequency over the full range of the PE15A3595 from 1 to 40 GHz, is typical of the performance of all four amplifiers. Gain varies no more than +/-1.85 dB over the range with average gain of 38.1 dB. The PE15A3595 operates from a 120-VAC supply while the PE15A3595 operates from both 120 VAC or 12 VDC for portable operation. Operating temperature range is -40° to +85°C, which makes the amplifiers usable in places other than the stable conditions of a laboratory. USB Components Shave Size and Cost The ubiquitous USB standard has significant advantages for measurement applications as USB-powered components can operate from anywhere a 5-VDC power supply is available, whether a laptop or benchtop computer, tablet, or wall-mounted charger. They are also extremely small and inexpensive considering their performance, measuring in the case of Pasternack’s amplifiers, attenuators, and switches, only 2.25 x 0.33 x 1 in.

The simplicity of these devices belies their potential, as they can be combined to produce a modest yet effective solution for making measurements in the field on deployed systems, during R&D and other stages of development, and even in production. As Pasternack provides free Windows software for the attenuators and switches they can be controlled remotely and even incorporated in a larger ATE system with benchtop instruments and other components. Based on inquiries Pasternack has received from current and potential customers, designers have found intriguing ways to use the products either singly or in combination to perform measurement tasks in a fraction of the space and at lower cost than their larger feature-laden counterparts. Pasternack’s USB-powered amplifiers (Figure 3) combine extremely small size with high RF output power and good overall performance and include the PE15A3900 that covers 50 MHz to 18 GHz and the PE15A3901 that covers 50 MHz to 40 GHz. Both amplifiers have P1dB RF output power of +10 dBm, along with 12 dB of gain (+/-2.5 dB), and a noise figure of 4.5 dB. The PE15A3900 has SMA female connectors and the PE15A3901 has 2.92-mm connectors. They have 50-ohm matched inputs and outputs for optimum performance over a broad frequency range, and a voltage regulator is integrated as well.

Complementing the amplifiers are two other families of components: 30-dB programmable PIN diode attenuators and switches that are often used in conjunction with amplifiers on the bench. The two attenuators, the PE70A3900 and PE70A3901, operate from 100 MHz to 18 and 40 GHz respectively with a step size of 1 dB, attenuation accuracy of +/-2.5 dB, insertion loss of 5 dB and 5 to 8 dB respectively, and input/output VSWR of 2.5:1. Pasternack offers free Windows software that provides control of the attenuators via any Windows PC or tablet.

The SPDT switches are the PE71S3900 and PE71S3901 that operate from 500 MHz to 18 and 40 GHz respectively with 3 to 5 dB of insertion loss, very high isolation of at least 60 dB, and fast switching speed of 6 µs. Like the attenuators, Pasternak offers free Windows control software that can be downloaded from company’s Web site. All of the USB products operate over a temperature range of -40°C to +85°C.The PE71S3900 uses SMA female connectors and the PE71S3901 2.92-mm connectors. Like all Pasternack products, the benchtop amplifiers and USB amplifiers, attenuators, and switches are available for same-day shipping. More information is available at our website.

Pasternack Enterprises