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COVER FEATURE
Modern frequency synthesis uses a combination of frequency multiplication and frequency division to generate the required data and carrier signals for microwave radio and radar applications. Frequency multiplication increases the carrier frequency while increasing the phase noise of the carrier by 20log(N), where N is the multiplication factor. Conversely, frequency division decreases the carrier frequency and changes the phase noise of the carrier by 20log(1/M), where M is the division ratio.
For the most part, frequency dividers are used in a phase-locked loop (PLL) to divide the voltage-controlled oscillator (VCO) output frequency down to the reference frequency in order to achieve phase/frequency locking. These devices are traditionally digital circuits and for high divide ratios (greater than 16) operate at input frequencies less than -2 GHz. At higher frequencies, digital frequency dividers are available in binary division ratios (/2, /4, /8... ) up to approximately 14 GHz. A new class of GaAs/InGaP heterojunction bipolar transistor (HBT) active frequency dividers offering odd division ratios (/3 and /5), high input frequency (up to 8 GHz) and wide input power range (-15 to +10 dBm) are now available in low cost plastic packages providing the designer with more flexibility in synthesizer architecture.
Frequency multipliers, on the other hand, are most commonly used after the VCO to increase the carrier frequency to the radio or radar transmit/receive frequency. Various devices are utilized to achieve frequency multiplication, including Schottky diodes, step recovery diodes, balanced rectifiers (frequency doublers) and saturated amplifiers. The advantages and drawbacks of each approach are well known. A new class of GaAs/InGaP HBT active multipliers offering conversion gain, wide input power range (-15 to +10 dBm), high output frequency (up to 16 GHz) and high multiplication factors (x 4, x 8 and x 16) are now available in low cost plastic packages that will dramatically simplify the design and implementation of X- and Ku-band synthesizers.
STANDARD FREQUENCY MULTIPLIER PRODUCTS
Four new active frequency multipliers have been added to the company's family of surface-mount frequency doubters. Figure 1 depicts the frequency coverage of the passive and active frequency multiplier line. The models HMC370LP4 and HMC443LP4 are active x4 frequency multipliers...