Agc Circuits; Analog Agc Circuits; Optimized Gain Distribution - Kenwood TS-990S In-Depth Manual

Hide thumbs Also See for TS-990S:

Table of Contents

AGC Circuits

To achieve high adjacent dynamic range characteristics, an analog AGC circuit is used together to make the A/D Converter

work to its performance limit. The AGC circuit is required to have low noise and a wide dynamic range, wide control range, and

linearity to the control. The TS‑990S implements high‑precision AGC response characteristics with an AGC circuit in which a

dual‑gate MOSFET is used (shown in the diagram "AGC Circuit with a Dual‑Gate MOSFET") and correction is made by DSP.

The graph below shows the AGC response characteristics to a control voltage in the circuit configuration with a dual‑

gate MOSFET. Sufficient control range, dynamic range, and linearity are secured.

The mixer, which is the key block in the main band receiver and is newly developed, has relatively larger conversion loss

than that of conventional mixers. Therefore, the circuit is structured to work in conjunction with a post‑amplifier, which

is placed in the mixer output, during operation of the pre‑amplifier. Pressing the [P.AMP] key improves the reception

sensitivity by approximately 14 dB by pre‑amplifier 1 and the post‑amplifier in a reception band below 21.5 MHz and

approximately 18 dB by pre‑amplifier 2 and the post‑amplifier in a reception band above 21.5 MHz.

The attenuation outside the band is fully obtained by the roofing filters with good selectivity. Therefore, the analog AGC circuit

and high‑gain IF amplifier are placed in a later stage so that undistorted IF signals are supplied as baseband signals to the DSP.

Fig. 19 AGC Circuit with a Dual‑Gate MOSFET

Fig. 20 AGC Response Characteristics to a Control Voltage

Dual Gate MOSFET

RECEPTION 03

Table of Contents