A double-tuned high-frequency (RF) circuit with balanced secondary

摘要

And a double-tuned oscillator 16 capable of band switching having an equilibrium second axis. A first tunable tank circuit having a plurality of first inductances 28,30 is tuned to a first frequency by a second capacitor 36,40 coupled in parallel with the first inductance 28,30. A secondary tank circuit having a plurality of second inductances (32, 34, 62) inductively coupled to one or both of the first inductances (28, 30) includes a second inductance (32, And second capacitors 38 and 42 coupled in parallel with the first and second capacitors 34 and 62, respectively. The DC reference potential 50 for the secondary circuit is coupled to the node junction of the second inductance 32, 34, 62 with the secondary tank circuit providing a balanced signal output. At least one of the plurality of first inductances 28 and second inductances 32, 34, 62 is switchable to band switching the tuning of the primary and secondary tank circuits to a second frequency. The output signal from the balanced secondary tank circuit is coupled to the input of the balanced mix via a constant bandwidth inductance (44a, 46a: 44b, 46b) without a mixer input balanced transformer.