Re: Kneisner and Doering KWZ30-2

Also up now is the oncept page:

The Concept

Overview

The DSP-Receiver KWZ-30/2 is like its predecessor a receiver for the
frequency range 10 kHz to 30 MHz (optional to 60 MHz) using digital signal
processing.

It was predicted for a long time that the analog/digital converter moves closer
to the antenna. This is the case too in the KWZ-30/2. The first intermediate
frequency is 75 MHz as before. From there the signal is converted to 30 kHz
using quadrature mixers. This second intermediate frequency is fed to the
A/D-converters. Then follows the DSP-unit, which is equipped with a high
performance DSP (32 bits).

The Controls

The controls of the KWZ-30/2 are much more comfortable than the controls of
the predecessor, which intentionally were designed thrifty. The display is a
colour display (quarter VGA) with a resolution of 320 x 240 pixels. On either
side of the display are 5 programmable keys. So the current function of the
key can be shown on the display. Besides the main encoder for the frequency
tuning there are three more encoders with smaller resolution. One is
dedicated for the volume control while the other two can be programmed for
other functions. Of course there too is a key pad with the numerical block and
other keys for the menue control and also for dedicated functions.

The Circuitry

The analog part of the set is a double conversion superhet with the first IF of
75 MHz and the second IF of 30 kHz. In front of the first mixer the signal is
passed though a low pass filter, a switchable high pass filter and an
amplifier/attenuator stage.

The conversion from the first IF to the second IF is performed using
quadrature mixers which secures a high mirror frequency attenuation. The
mixers are followed by two A/D-converters with a dynamic range of 120 dB.
From the A/D-converters the signal is passed to the DSP. It is a 32-bit DSP
from Analog Devices. So there is an almost unlimited dynamic range available
for the signal processing. In the DSP the selection and demodulation of the
signal is performed as well as the other processing like notch filter, noise
reduction, squelch and others.

For the alimentation a switching power supply is used which accepts voltages
from 90 to 240 Vac. With this unit no voltage selection is necessary
worldwide. The set can also be run with 12 to 15 Vdc.

Optional Equipment

The frequency range can be extended to 30 - 60 MHz. This extension is
performed using an additional front end module with filters and its own VCO.

The spectrum display allows the display of the frequency spectrum in a range
of +/-100 kHz from the current frequency with a dynamic range of 80 dB. The
visible frequency range can be selected as well as the attenuation.

DRM: it is our intention to use a module from Texas Instruments for the
demodulation. At this time a sample unit is not yet available. In any case it
will
be a solution which will not need an external PC.

dxAce
Michigan
USA

sdaniel13@xxxxxxxxxx wrote:

Interesting. It says:

What can be improved in a device that can do everything? The main RF
properties like intercept values, dynamic range and sensitivity can
hardly be improved substantially. Also the filters for the narrow band
selection can not be improved.

What is remaining? At first it is the comfortable control which can be
improved. The controls of the KWZ-30 were designbed very thrifty and
the use was therefore partly complicated. On the other side there are
now new components available which allow a different topology of the
receiver with a higher performance. The technical equipment can be
improved substantially. With this new performance level the receiver
can also be used by professional users.

.

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