Expanding Synthesized Signal Generation

Here are.two broadband, programmable, high-spectral-purity microwave signal sources, a 2-to-1 8-GHz synthesized signal generator and a 2-to-6.2-GHz synthesizer. Both are single, compact, 13-cm-high instruments. tr REQUENCY SYNTHESIZERS are signal sources l' that produce a selected output frequency by some type of arithmetic operation on a stable reference signal, which is usually derived from a quartz crystal oscillator. The synthesizer's major advantages are the accuracy and stability of its output frequencies. A signal generator, on the other hand, is a signal source that produces a selected output frequency directly from a tunable oscillator. It usually has a calibrated output level and flexible modulation capabilities, and these are its major advantages. The synthesized signal generator, a combination of these two types of signal sources, offers many of the advantages of both. Broadband frequency synthesizers have been available in the VHF/UHF range since 19641.In 1971 the HP aOOO family of instruments introduced the concept of a synthesized signal generator with modulation and output level contol.2 In 1975 the maximum frequency range of the 8660 family was raised to 2.6 GHz and phase modulation was included.3 In the microwave range, frequency sources have generally been narrow-band instruments, often covering one communication band or one octave. Wider frequency coverage has been obtained by means of collections of oscillators that can be switched on and off. In tgZS the broadband HP 862904 Sweeper Plug-In was the first to cover the entire 2-to-18-GHz range with a single YlG-tuned oscillator followed by a YIG-tuned harmonic multiplier.4 The new 8671A Synthesizer and 8672A Synthesized Signal Generator, Fig. 1, combine frequency synthesis techniques with improved versions of the 86290A components to provide extremely accurate frequency coverage in the 2-to-18.6-GHz range. The two instruments share a common 2-to-6.2-GHz frequency synthesizer and differ only in their frequency coverage and output signal level control capabilities. The 8671A spans 2 to 6.2 GHz with 1-kHz resolution, can be frequency modulated, and provides more than +8 dBm of unleveled power. The 8672A has an inter-Pilnted nUSA. nal YIG-tuned multiplier and provides 2-to-18.6-GHz frequency coverage. 8672A RF output power is internally leveled and calibrated from *3 dBm to-120 dBm. It may also be externally leveled. Six metered frequency modulation ranges and two metered Cover: Model 86724 Synthesized Signal Generator works like a well rehearsed orchestra: fou r phase-locked loops (1-4) and an RF output assemb/y (5) are conducted by a digital control unit (6). The four …