04 LOCAL OSCILLATOR CIRCUIT
22
Local Oscillator
The local oscillator circuit in the TS-890S is configured to obtain the characteristics needed for each signal, such as
the VCO (Voltage Controlled Oscillator) division type for the first and second oscillator signals and DDS (Direct Digital
Synthesizer) direct system for the third local oscillator.
First Local Oscillator Signal
To obtain high-quality C/N (Carrier-to-Noise ratio) characteristics, the first local oscillator signal is configured by further
developing the VCO division type adopted on the TS-990S to achieve a VCO device with a high C/N in the gigahertz
band as well as a reference oscillator circuit that excels in adjacent C/N characteristics.
22.348 MHz
First Local Oscillator
Frequency
Fig. 25 Block Diagram of First Local Oscillator Signal (Reception of 14.1 MHz Signals)
19.2 MHz reference frequency is input as the reference signal of the PLL (Phase Locked Loop) device, and the PLL loop
is applied to the 100 MHz signal to generate signal with excellent C/N characteristics.
The 100 MHz signal that is generated is input to the VCO device (HMC829) to generate signal with a high C/N in the
gigahertz band within the device.
The generated is then divided and passed through the amplifier and bandpass filter before it is output as the first local
oscillator signal.
Theoretically, the C/N characteristics of gigahertz band signals generated inside the device are improved by the effect of
division at the ratio of 20*log (division ratio).
(1/10 division: 20*log (1/10) = -20dB)
Fig. 26 HMC829
Содержание TS-890S
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