[Discuss-gnuradio] AOR JT2000 wide band DSP FFT receiver

[Dave Emery]

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     The JT2000 receiver from AOR provides a fresh look at wide range 
receivers. Using the latest DSP technology (Digital-Signal-Processing) in the 
i.f. stage (not just audio DSP), the receiver allows very fast FFT analysis 
(Fast-Fourier-Transform) of the radio spectrum enabling active radio channels 
to be detected and monitored very quickly. 
      Fundamentally, FFT uses spectral analysis in the time domain to evaluate 
which frequencies are active, sections of the radio spectrum are ‘grabbed’ 
within a few tens of milliseconds and a list of active frequencies prioritised 
automatically. If compared in conventional terms to a scanning receiver, JT2000 
is capable of scanning several thousand channels per second! Put in to 
practice, this means that it is possible to monitor a frequency on the VHF 
airband while simultaneously checking the whole band (every frequency) for new 
transmissions several times per second, clearly no activity will be missed with 
the most elusive, infrequent and brief transmissions captured. Spectral 
analysis can continue during monitoring.

      Sensitivity, selectivity and dynamic range will challenge the very best 
wide band receivers. A conventional RF stage uses double or triple conversion 
(depending on the receive frequency) to provide good image rejection over a 
wide reception range from a few kHz to over 2.5 GHz. A wide bandwidth is 
maintained throughout both the RF and IF stages and coupled with a fast, high 
resolution analogue-to-digital converter provides the RF signal analysis 
facilities. Digital filtering with 22-bit accuracy provides reception 
bandwidths from a few Hz up to 250 kHz enabling the DSP to demodulate a wide 
range of signals. Standard reception modes include SSB, AM, synchronous AM, FM 
and wideband (broadcast) FM, all with selectable IF bandwidths. New features 
like ‘dynamic squelch’ (with manual override) add to the capabilities and ease 
of use.
     

The standard JT2000 is presented in a rugged cabinet (‘black box’) with 
internal design to high standards employing six-layer PCBs and custom parts, 
control is via a host computer. Connection to a host computer is via a standard 
RS232 serial connection and for higher transfer speeds, via USB (Universal 
Serial Bus), transfer speed is largely dependant upon the host computer, the 
faster the computer, the greater the data - and better the analysis results. 
JT2000 provides an extra serial port which allows direct connection to, and 
control of an additional, separate monitoring receiver for hand-off 
applications. The receiver’s design is intended to allow for future functions 
to be added. 

All internal control software and DSP routines are stored in flash memory which 
can be re-programmed from the host computer. New signal analysis methods and 
different signal demodulation can be implemented with a simple software 
download. If new circuitry is required to handle special signals then there is 
a spare module slot within the receiver; both analogue IF signals and a 
high-speed serial interface to the DSP are available to support it. A front 
panel controller is planned with display and keypad which will provide 
stand-alone reception and operation in addition to computer control.

Windows based control software is supplied with the receiver and includes a 
database processor and function applets to control receiver settings. The heart 
of the control software is a database system that contains scanning and 
searching channel information. Unlike other fixed databases, JT2000 can quickly 
and dynamically build brand new ‘real-time’ databases (from a blank start). The 
database content is a mixture of signal information from the user (frequency 
and identification) and reception information from the receiver (signal 
strengths and durations). From this data the software can produce signal logs 
and band occupancy information and the receiver can be controlled to monitor 
channels based on criteria of priority, signal strength or signal duration as 
decided by the user.

Additionally the receiver can automatically produce database entries of active 
channels during a period of observation of sections of the radio spectrum. All 
database content is in a transportable format so that further data analysis can 
be carried out with standard Microsoft Office applications. Similarly databases 
of spectrum allocation can be imported from other formats through these 
programs.

JT2000 was displayed at the Dayton Hamvention in May'2000 for the first time in 
'proto-concept' format (part way between concept, prototype and 
pre-production). The new model is the result of another successful joint 
development between AOR and internationally acclaimed UK designer John Thorpe 
(design engineer of the award winning AR7030). JT2000 is designed and built in 
the UK, production is expected to start at the end of 2001.

Acrobat PDF leaflet (153kB), click here.



Price £ T.B.A. but primarily targeted at the commercial and government market, 
possibly around GBP 2.5k


-- 
        Dave Emery N1PRE,  address@hidden  DIE Consulting, Weston, Mass. 
PGP fingerprint = 2047/4D7B08D1 DE 6E E1 CC 1F 1D 96 E2  5D 27 BD B0 24 88 C3 18