Microtelecom_Perseus_broch.pdf

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1、- - - - - - NSARC - Perseus SDR Receiver115-Sep-11 PerseusPerseus DirectDirect- -Sampling SDR HF ReceiverSampling SDR HF Receiver Adam Farson VA7OJAdam Farson VA7OJ - - - - - - NSARC - Perseus SDR Receiver215-Sep-11 Why Why “ “PerseusPerseus” ”? ? !Manufactured by Microtelecom s.a.r.l., Pavia di Udi

2、ne, Italy !One interpretation (from a Microtelecom brochure): “Pretty Excellent Receiver for Software-Eager Unperceivable Signals” - - - - - - NSARC - Perseus SDR Receiver315-Sep-11 What the Perseus doesWhat the Perseus does ! The Perseus is: a “radio” ! a high-performance LF/MF/HF receiver a test i

3、nstrument ! an affordable spectrum analyzer ! an accurate selective RF power meter ! It is not: a transceiver ! it has no transmit capability - - - - - - NSARC - Perseus SDR Receiver415-Sep-11 Front PanelFront Panel !Clip: ADC clipping (full-scale, 0 dBFS) !WB: Wideband (preselector out) !-10, -20:

4、Attenuator value in dB - - - - - - NSARC - Perseus SDR Receiver515-Sep-11 Rear PanelRear Panel The Perseus must be powered only with the supplied PSU. - - - - - - NSARC - Perseus SDR Receiver615-Sep-11 Interior ViewInterior View Preselector ADC DDC USB Controller - - - - - - NSARC - Perseus SDR Rece

5、iver715-Sep-11 Block DiagramBlock Diagram - - - - - - NSARC - Perseus SDR Receiver815-Sep-11 Perseus Spec SheetPerseus Spec Sheet !Frequency range: 10 KHz - 30 MHz !Modes: USB, LSB, CW, AM, FMN, FSK, DRM, etc. as defined by software !Sensitivity: 0.39 V SSB (S+N)/N= 10 dB* !MDS: -124 dBm (SSB, 2.4Kh

6、z BW)* !Selectivity: Defined by the PC software !Rejection: 90 dB* !IP3: 31 dBm* !Dynamic Range: 103 dB (SSB, 2.4 kHz BW)*, 107 dB (CW, 500 Hz BW)* !Blocking: 125 dB* -131 dBm (CW, 500Hz BW)* !ADC clipping level: -3 dBm (preamp off), -6 dBm (preamp on) !Output sampling rate: 100/200/400kHz I 9 x 6-p

7、ole BPF (1,7 - 30 MHz) !Attenuator: 0, 10, 20, 30 dB !ADC: LTC 2206-14, 14-bit, 80Ms/s !DDC: XC3S250E FPGA !PC interface: USB 2.0 480 Mbit/s (cable included) !Power supply: +5Vdc +/-5% 1 A (120 240V PSU included) !Cabinet: Aluminum, 110 x 36 x 185 mm (W x H x D) !*Typical at. 14.2 MHz - - - - - - NS

8、ARC - Perseus SDR Receiver915-Sep-11 Definition of an SDRDefinition of an SDR ! A software-defined radio system, or SDR, is a radio communication system in which components previously implemented in hardware are now implemented by means of software on an external computer or on embedded computing de

9、vices. Such components include mixers, filters, amplifiers, modulators/demodulators, detectors, etc. ! The PERSEUS meets this definition, as all its functions except RF signal management (preselector, preamplifier and attenuator) are implemented in on-board firmware and in software running on an ass

10、ociated PC. - - - - - - NSARC - Perseus SDR Receiver1015-Sep-11 Why direct sampling?Why direct sampling? ! In a direct sampling SDR, the ADC (analogue to digital converter) samples the incident RF directly. ! The RF front end presents the entire HF range, or a portion thereof, to the ADC. The presel

11、ector band-limits the RF signal to increase the usable dynamic range of the ADC. ! The digitized RF signal is digitally down-converted to a baseband (“zero IF”) which is presented to the PC via a USB link. ! The PERSEUS software performs all subsequent signal- processing and demodulation functions;

12、the PC sound-card passes the demodulated audio to the speakers. - - - - - - NSARC - Perseus SDR Receiver1115-Sep-11 Digital downDigital down- -converter (DDC)converter (DDC) ( NCO) (from ADC, 10 kHz 30 MHz) Baseband to USB port (100/200/400 kHz) - - - - - - NSARC - Perseus SDR Receiver1215-Sep-11 Th

13、e magic of processing gain:The magic of processing gain: “ “dynamic range from thin airdynamic range from thin air” ” !Processing Gain Gp= 10 log10 (fs/ 2B) where fs= sampling frequency and B = user channel bandwidth !If fs= 80 MHz and B = 2.4 kHz (SSB), then Gp= 10 log10 (80*103/ 4.8) 42 dB !For 14

14、-bit ADC, theoretical dynamic range = (14*6)+1.76 86 dB !Thus, theoretical system dynamic range = 86 + 42 = 128 dB fs/2 f Pn B - - - - - - NSARC - Perseus SDR Receiver1315-Sep-11 ENOB ENOB (Equivalent Number of Bits)(Equivalent Number of Bits) and Noise Floorand Noise Floor ! Theoretical dynamic ran

15、ge of ADC = 20 log 2n where n = number of bits ! For LTC2206-14 ADC in Perseus, 20 log 214 84 dB ! But nothing is perfect! From data sheet, ADC S/N ratio 76 dB This equates to 12.7 bits, i.e. ENOB 13 ! So now our system dynamic range is 76 + 42 = 118 dB ! ADC clipping point (0 dBFS) is absolute inpu

16、t power limit ADC “crashes” if driven above 0 dBFS ! Typically, 0 dBFS -6 dBm ADC noise floor = -6-76 = -82 dBm (B = 0.5fs= 40 MHz) ! For B = 2.4 kHz (SSB), noise floor = -82 + 42 = -124 dBm MDS (minimum discernible signal) = -124 dBm - - - - - - NSARC - Perseus SDR Receiver1415-Sep-11 The preselect

17、or and its roleThe preselector and its role IN from ATT OUT to LPF2 !The preselector narrows the RF bandwidth presented to the ADC. !In wideband mode, e.g. for spectral analysis of entire HF range, the preselector is bypassed. This degrades IMD3 dynamic range by 3 dB, with a 2 dB improvement in MDS.

18、 !IMD2 dynamic range is degraded in wideband mode. This is significant in areas (e.g. Europe) where HF broadcasters can drop IMD products into amateur bands. - - - - - - NSARC - Perseus SDR Receiver1515-Sep-11 RF preamp design considerationsRF preamp design considerations ! Even the best ADCs have a

19、 modest noise figure (NF). LTC2206-14 in Perseus: NF = 16 dB. This is acceptable in HF range per CCIR-670. ! A preamplifier is desirable for weak-signal reception, or when using limited antennas. The preamp should have a somewhat lower NF than the ADC, together with moderate gain. Enabling the pream

20、p should not degrade the blocking dynamic range (0 dBFS MDS) by more than 4 dB. ! The preamps 3rd-order intercept point (IP3)should be as high as possible, to minimize degradation of overall IMD3 dynamic range. - - - - - - NSARC - Perseus SDR Receiver1615-Sep-11 “ “RealReal- -World NumbersWorld Numb

21、ers” ” ! From my lab: -123 dBm MDS 3.6 MHz, 2.4 kHz SSB, preselector off ! Calculated value: -124 dBm -121 dBm MDS 3.6 MHz, 2.4 kHz SSB, preselector on AM sensitivity 3.9 MHz, 5 kHz filter: 1.3 V ! For 10 dB (S+N/N), preselector on Reciprocal mixing noise RM 107 dB ! ! RM = 113 dB 1 kHz offset (500

22、Hz CW filter) RM is due mainly to ADC clock phase noise (slight contribution from ADC jitter) Filter shape factor (-6/-60 dB): 1.09 IMD3 dynamic range 2 kHz spacing 100 dB ! ! Blocking dynamic range (500 Hz CW) 125 dB ! Typical IMD2 dynamic range 110 dB ! This outperforms most legacy receivers. - -

23、- - - - NSARC - Perseus SDR Receiver1715-Sep-11 IMD IMD behaviourbehaviour of ADCof ADC: : there is no true there is no true “ “3 3 rdrd- -order intercept point order intercept point” ” !In an ADC, the IMD3 product does not follow the 3rd-order law, and is essentially independent of signal amplitude

24、. IMD degrades severely at 0 dBFS (ADC clipping point). Note that input power and IMD curves diverge, so there is no true intercept point. IP3 of typical ADC -60 -40 -20 0 20 40 -60-40-2002040 Pin dBFS Pin dB -40 -30 -20 -10 0 10 20 30 40 50 60 IP3 dBm Pin IP3 - - - - - - NSARC - Perseus SDR Receive

25、r1815-Sep-11 The magic of dithering:The magic of dithering: a feature unique to the directa feature unique to the direct- -sampling SDRsampling SDR !Dithering is a very small amount of random noise (white noise), which is added to the ADCs analogue input before conversion. It randomly toggles the le

26、ast significant bit, and has the effect of reducing IMD at the expense of a slight (1 2 dB) increase in noise floor. Measurement of IMD3 product with and without dithering -130 -120 -110 -100 -90 -80 -45-40-35-30-25-20-15 Input Power dBm IM3 dBm w/o Dith. with Dith. - - - - - - NSARC - Perseus SDR R

27、eceiver1915-Sep-11 PC interfacePC interface and baseband characteristicsand baseband characteristics ! A USB 2.0 cable (480 Mbit/s) connects the Perseus to the PC. ! The Perseus output is a digital baseband with I and Q channels 90 apart, with zero frequency offset (“zero IF”). ! Output baseband wid

28、th is selectable: 100, 200, 400, 800 or 1600 kHz ! The PERSEUS software running on the PC performs all subsequent signal-processing and demodulation functions. ! The PC sound-card provides the DAC (digital/analogue converter) and audio amplifier driving the speakers. ! Thus, the choice of sound-card

29、 (integral, PCI or external) is not critical for Perseus performance. - - - - - - NSARC - Perseus SDR Receiver2015-Sep-11 Perseus softwarePerseus software ! Downloadable from Perseus website: http:/www.microtelecom.it/perseus/ Current version: 4.0b. ! Perseus drivers also on website. ! Perseus also

30、supports Winrad. with ExtIO.dll for Winrad (also on website). ! 4.0b includes HFspan (wideband spectrum analyzer) and Perseus Server for remote operation. 4.0b also includes user documentation & installation notes. ! Perseus software allows recording and playback of baseband streams. Playback displa

31、ys entire screen live with audio, and allows “tuning” to select desired signal from recording. - - - - - - NSARC - Perseus SDR Receiver2115-Sep-11 Operational examples:Operational examples: Perseus in the labPerseus in the lab Perseus as a spectrum analyzer/power meter, displaying a notch filter sto

32、pband - - - - - - NSARC - Perseus SDR Receiver2215-Sep-11 Perseus on the MW AM bandPerseus on the MW AM band On the MW broadcast band: listening to AM 680 kHz, displaying a 400 kHz span centred on 680 kHz. Span range: 400 Hz to 1.6 MHz. Minimum resolution bandwidth (RBW): 0.5 Hz. - - - - - - NSARC -

33、 Perseus SDR Receiver2315-Sep-11 On the ham bandsOn the ham bands Playing back a recording made on 18.125 MHz USB. The entire screen, and the audio, are played back live. - - - - - - NSARC - Perseus SDR Receiver2415-Sep-11 HFSpanHFSpan: : a wideband spectrum scopea wideband spectrum scope HFspan is

34、a simple wideband spectrum analyzer program for observation of the entire frequency range (0.1 kHz 30 MHz). RETURN - - - - - - NSARC - Perseus SDR Receiver2515-Sep-11 Now for a live demo!Now for a live demo! ! The Perseus display will be projected onto the auditorium screen. - - - - - - NSARC - Perseus SDR Receiver2615-Sep-11 Thanks for watching!Thanks for watching! ! Links for further study: Perseus site: http:/www.microtelecom.it/perseus/ Comparison of SDR and superhet RX Perseus with Linrad by SM5BSZ