GB1493592A - Frequency shift keying data transmission systems - Google Patents
Frequency shift keying data transmission systemsInfo
- Publication number
- GB1493592A GB1493592A GB350274A GB350274A GB1493592A GB 1493592 A GB1493592 A GB 1493592A GB 350274 A GB350274 A GB 350274A GB 350274 A GB350274 A GB 350274A GB 1493592 A GB1493592 A GB 1493592A
- Authority
- GB
- United Kingdom
- Prior art keywords
- input
- filter
- output
- receiver
- cycles
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
Landscapes
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
Abstract
1493592 Data transmission; FSK systems SERCK INDUSTRIES Ltd 21 Jan 1975 [25 Jan 1974 8 Nov 1974] 03502/74 and 48389/74 Heading H4P In an FSK system, marks are represented by a half cycle of one frequency and space by another, both of approximately sinusoidal waveform in which phase is continuous and slope of the waves is rectilinear at cross-over points, the time lengths of mark and space symbols being matched to half periods of respective keying frequencies. Areas embraced by mark and space half cycles may be equalized by reducing the amplitude of lower frequency half cycles which may be achieved by passing the signals to a gated attenuator which may be a potentiometer element switched by a transistor. D.C. restoration and/or clamping may be performed at receiver and/or transmitter positions. In one transmitter embodiment, Fig. 6, a generator 21 provides a rectangular waveform dependent on data input equal to a half period of corresponding frequency, this being passed through a digital filter 22 which converts it to a wave with continuous phase and constant slope at cross-overs which is passed to a driver unit 23. The generator 21 and filter 22 are described in greater detail in Figs. 7 and 9 (not shown) the latter including a clocked shift register arrangement having output resistors (R1-Rp) providing an ascending/decending linear staircase output through an amplifier (28) to a smoothing network. The receiver Fig. 11 may include a Gaussian low pass filter providing an input to a zero crossing detector 32 giving a square output corresponding to detected zero crossings, marks and spaces being detected by measuring time duration of the respective excursions. This may be achieved by counting the number of cycles of receiver clock pulses each duration and compared with a threshold number exactly midway between expected number of cycles in marks/spaces such that an excess above the threshold may be a space and deficiency a mark. A logical arrangement is described in connection with Fig. 13 (not shown). The zero crossing detector may be as given in Fig. 12 (not shown) and comprise a balanced differential input operational amplifier (35) with a negative feedback resistor (36) to limit the gain, with a resistor (Ro) providing initial setting, and to compensate for non zero triggering level of a following comparator (37). A CR network (38) forms a high pass filter and sends one input of comparator (37) is earthed, its output switches from a high to low level when input from the filter becomes positive hence the arrangement acts as a zero crossing detector and produces a half cycle per bit rectangular waveform. A feedback resistor (Rf) ensures that any slow rising input causes a sharp transition the output but is made large enough to prevent any significant hysteresis effect. In conditions of high noise level, a zero D.C. restoration circuit such as is given in Fig. 17 (also not shown) may be used having input peak detecting arrangements (117-119) for positive polarity and (120-122) for negative polarity, peak outputs from which are added algebraically by resistors (123, 124) and applied through an amplifier and further summing resistors (125, 126) to restore the D.C. level to a determined value. A simple form of clock pulse generator may comprise NAND gates (111-114) with feedback capacitor (115) and resistor (116) forming a CR circuit of appropriate time constant. Several other forms of transmitter and receiver are described in the Specification. The filter to convert from square to approximately sinusoidal waveform may be of the "Butterworth" type.
Priority Applications (7)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB350274A GB1493592A (en) | 1974-01-25 | 1974-01-25 | Frequency shift keying data transmission systems |
CA218,467A CA1053583A (en) | 1974-01-25 | 1975-01-23 | Data transmission systems |
AU77576/75A AU7757675A (en) | 1974-01-25 | 1975-01-23 | Data transmission systems |
SE7500802A SE7500802L (en) | 1974-01-25 | 1975-01-24 | |
NL7500887A NL7500887A (en) | 1974-01-25 | 1975-01-24 | DATA TRANSMISSION SYSTEM. |
DE19752503468 DE2503468A1 (en) | 1974-01-25 | 1975-01-24 | Data transmission system with frequency keying - is for binary signal bits and spacings represented by half-periods of two frequencies |
US05/726,323 US4066841A (en) | 1974-01-25 | 1976-09-24 | Data transmitting systems |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB350274A GB1493592A (en) | 1974-01-25 | 1974-01-25 | Frequency shift keying data transmission systems |
Publications (1)
Publication Number | Publication Date |
---|---|
GB1493592A true GB1493592A (en) | 1977-11-30 |
Family
ID=9759555
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB350274A Expired GB1493592A (en) | 1974-01-25 | 1974-01-25 | Frequency shift keying data transmission systems |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB1493592A (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN111600583A (en) * | 2020-06-02 | 2020-08-28 | 中北大学 | Random frequency triangular wave generator based on diffusion memristor and current transmitter |
-
1974
- 1974-01-25 GB GB350274A patent/GB1493592A/en not_active Expired
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN111600583A (en) * | 2020-06-02 | 2020-08-28 | 中北大学 | Random frequency triangular wave generator based on diffusion memristor and current transmitter |
CN111600583B (en) * | 2020-06-02 | 2023-03-14 | 中北大学 | Random frequency triangular wave generator based on diffusion memristor and current transmitter |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
PS | Patent sealed | ||
PCNP | Patent ceased through non-payment of renewal fee |