Vector signal generator aimed at mid-range RF T&M tasks

March 04, 2015 // By Graham Prophet
Tektronix’ TSG4100A series of signal generators are positioned as vector signal generators (VSG) at the affordable price of a basic signal generator: Tek says the instrument is the first vector RF signal generator from a tier-one vendor with a price point of less €13,000 / £10,000.

The TSG4100A series includes three models with carrier frequencies from DC to 2.0 GHz, 4.0 GHz and 6.0 GHz respectively. The instruments provide spur-free outputs with low phase noise (–113 dBc/Hz at 1 GHz), amplitude accuracy (< ± 0.4 dB at 1 GHz, 0 dBm CW signal from +16 dBm to -100 dBm level range) and frequency resolution (1 μHz at any frequency).  An oven-controlled crystal oscillator time-base provides <±0.002 ppm temperature stability and <±0.05 ppm ageing stability, claimed as the most accurate and stable available for a mid-range signal generator.

The generators offer a wide variety of modulation capabilities. Modes include amplitude modulation (AM), frequency modulation (FM), phase modulation (ΦM), and pulse modulation. There is an internal modulation source as well as an external modulation input. Unlike most analogue signal generators, the TSG4100A can sweep continuously from DC to 62.5 MHz. And for frequencies above 62.5 MHz, each sweep range covers more than an octave.

Units can be software upgraded to support VSG applications. With the vector upgrade, TSG4100A series offers full support for vector signal modulation on RF carriers between 400 MHz and 6.0 GHz. It features a dual, arbitrary waveform generator operating at 125 MHz for baseband signal generation. The generator has built-in support for the most common vector modulation schemes: ASK, QPSK, DQPSK, π/4 DQPSK, 8PSK, FSK, CPM, QAM (4 to 256), 8VSB, and 16VSB. It also includes the standard pulse shaping filters used in digital communications: raised cosine, root-raised cosine, Gaussian, rectangular, triangular, and more. For additional flexibility, the rear-panel BNC I/Q modulation inputs support arbitrary vector modulation from an external source.

Until now, Tek says, RF engineers have had to choose between basic RF signal generators or far more expensive vector signal generators (VSG). The TSG4100A offers a VSG at an affordable RF signal generator price. The TSG4100A can be upgraded in the field to deliver more advanced vector and digital modulation capabilities.

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