Vertex Standard FT-1000MP manual Advanced Features

Advanced Features

EDSP

Enhanced Digital Signal Processing uses A/D (Ana- log to Digital) and D/A (Digital to Analog) conversion techniques under microprocessor control to achieve significant enhancement of signals at the audio and low-frequency IF levels. The major capabilities offered by EDSP lie in the area of heterodyne/random noise reduction and audio bandpass filtering. Digital filters have many advantages over their analog counterparts in that they can meet tighter specifications on param- eters such as voltage and temperature drift and noise problems. And the hybrid filter architecture of the MARK-VFT-1000MP, utilizing extensive analog IF fil- tering to protect the DSP circuitry which follows, guar- antees superior strong-signal performance under crowded band conditions.

The MARK-VFT-1000MPuses a 16-bit NEC µPD77016 CMOS digital signal processor chip featur- ing a 30-nS Instructions Cycle, 33 MHz Clock fre- quency, a 16 x 16-bit and 40-bit multiply accumulator, 40-bit Barrel Shifter, and 64 K Bytes Program ROM.

DSP enhancement is basically a four-step process. Audio (or EDSP IF) input is sampled several thousands of times per second, then the frequency and ampli- tude of the audio are converted into a digital represen- tation of the analog waveform that resembles ascend- ing and descending “staircases” by the A/D (analog- to-digital) converter. This is later changed into digital serial bitstream as raw data for analysis and process- ing.

Information is extracted from digital data, and the EDSP chip performs complex mathematical calcula- tions according to pre-programmed routines known as algorithms. Algorithms are processed then compared against a set of parameters (or threshold if you will) based on a phenomenon known as “correlation.” The degree of correlation depends on the incoming signal’s characteristics: random noise has relatively little cor- relation, speech contains moderate correlation, with heterodynes (and QRM) being highly correlated. The EDSP microprocessor is programmed with various parameters corresponding to different known audio phenomena.

EDSP allows the frequency spectrum of a received signal to be modified according to a specific set of pa- rameters for the desired effect (QRM reduction, audio tailoring, etc.). Certain types of audio interference leave

adistinctive signature or “footprint,” which can be rec- ognized, and “processed out” of the digitally-recon- structed audio from the EDSP chip. Also, digital filters are constructed which emulate traditional low-pass, high-pass, band-pass, and band-stop filters, except with steep skirt shaping and performance possible with digi- tal technology. EDSP also allows direct “digital” de- modulation of audio for receive, as well as direct modu- lation of audio for transmit.

page 72 MARK-V FT-1000MP Operating Manual