U N D E R S T A N D I N G T H E B B 6 0 A H A R D W A R E
8 Understanding the BB60C Hardware
Front End Architecture 8.1
Description 8.2
The BB60C is a two-stage superheterodyne receiver, using two independent intermediate
frequencies (IF), selected based on RF input frequency. Each IF has a corresponding distributed
element notch filter in the RF section to reduce spurious responses from input signals at the IF
frequency. Each RF band also has a distributed element filter buried in the multilayer PCB
laminate, engineered to reject that band’s image frequencies and reduce LO feed-through.
Wherever possible, RF band pass filters were used to reject signals which could result in spurious
mixer products, such as ½ of the tuned RF frequency, or image frequencies. To reduce spurious
signals from second-order intermodulation where filtering was not practical, push-pull amplifiers
were used in both the preamplifier and mixer stages, effectively canceling even-order mixing
products. Direct conversion was used below 10 MHz, completely avoiding the intermodulation
products associated with mixing.
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