LINEAR OPERATIONAL MODULE FOR AMPLITUDE MODULATED RF CARRIERS

MODEL 2A

Epoxy-encapsulated module for PC mounting

MODEL 2A-C

Same as 2A but connectorized in shielded housing with SMA connectors and feedthrough capacitors

APPLICATIONS

  • Replacement for expensive log-amps (the 2A can drive a DC-to-logarithmic-converter IC or module, or can drive an A-to-D converter with software conversion to log)

  • Highly linear wide-dynamic-range RF detection

  • High-speed low-distortion AM demodulation

  • Low-distortion data transmission/reception (eg, send thermal or strain-gauge or computer data information over coax cable where conventional baseband techniques would pick up interference and 60 Hz hum)

  • Radar STC (sensitivity-time control) and AGC (automatic gain control) detector

  • PIN diode attenuator linearizer (requires two PIN attenuator units)

  • Distortion-reduction and response-flattening of Shortwave broadcast transmitters

  • Automatic Test Equipment (ATE) test-fixture RF linear detection and/or demodulation.

  • Signal-generator levelling-loop detector with high linearity, allowing low-distortion generation of AM

  • Linear-scale RF voltmeter with built-in AM demodulation capability

  • Low -distortion AM Modulation - monitor

  • Phase-insensitive low-level AM demodulation (an advantage over synchronous detectors)

  • Add audio channel or data channel to an existing CCTV system without adding FM Bessel sidebands
  • Patented circuitry combined with proprietary diodes, matching networks and assembly techniques. (US Patent # 4,403,194)

    APPLICATION AS A ZERO-DISTORTION MODULATOR

    The model 2A should be driven by a single-ended baseband plus DC signal into pin 9. The DC term supplied sets the average carrier output level, and the AC baseband signal superimposed on this DC swings the carrier amplitude above and below this value. The maximum frequency of the AC signal is 200 kHz, and the total harmonic distortion is highest for higher AC baseband frequencies, rising above that specified for 1 kHz modulation.

    The RF output of the 2A in the modulator mode is very accurately controlled at 50 Ohms, and has an output RMS carrier amplitude of 1 Volt RMS at pin 7 (into 50 Ohms) per 1 Volt into pin 9, very accurately trimmed internally.

    The maximum instantaneous undistorted RF carrier output level in this mode is 1 Volt RMS into 50 Ohms. Additionally, twice this level is available into an open circuit load with the 2A remaining stable.

    No connections should be made to the pins not shown, except that pins 13 and 14 (the 10 MHz differential outputs) may be AC coupled into a type MC10116 or MC10216-style ECL line receiver using a 56 uH shielded inductor (eg, Nytronics WEE-56) between each ECL line receiver input pin and Vbb (pin 11 of the line recvr.). In this manner, the CW carrier, before modulation is impressed, can be used to synchronize other circuits as desired by the user, or can be used to furnish a system clock, since the 10 MHz signal is crystal-controlled and accurate to much better than 0.1%.

    The modulator in the model 2A and 2A-C is two-quadrant.


    Figure 1: The Model 2A as a zero-distortion modulator.

    APPLICATION AS A HIGHLY LINEAR RF DETECTOR

    Refer to the appropriate pin-interconnection diagram. The modulator output is connected to the RF feedback-detector input pin (6). In normal high-accuracy use, the RF signal to be detected and/or demodulated is capacitor-coupled into pin 1, the RF input-detector. This capacitor coupling, or "DC-block", must be supplied by the user, and is suggested in order to provide identical transient-response in both the RF input and RF feedback paths (the RF feedback path is already AC-coupled via 0.1 uF). However, the penalty for not AC-coupling is not severe, causing only about 0.2% error.

    The user-supplied trimpot zeroes the linearized-detector output baseline.


    Figure 2: The Model 2A as a highly linear RF detector.

    MODEL 2A-C CONFIGURATIONS

    The model 2A-C is available in two versions: (1) configured as a modulator; and (2) configured as a linearized ideal detector. The input and output ports are SMA connectors. (See specs.)

    USING THE 2A TO DETECT RF SIGNALS UNDER 10 MHZ

    In the event that operation must be obtained at less than 10 MHz for the LINEAR RF DETECTOR configuration, external matched capacitors must be supplied from pins 3 and 4 to ground. The value of these must be at least 100 pF times the ratio of 10 MHz to the lowest carrier frequency to be detected. For example, for detection of a 10 kHz carrier frequency, each external capacitor must be 0.1 uF. The maximum recoverable modulation frequency will also be reduced by the same ratio (1000 times). In addition, an external compensation capacitor must be added to keep the RF feedback loop stable (free of oscillations). This capacitor must be added from pin 10 to pin 11 and must have a value at least equal to the previously calculated ratio (of 10 MHz divided by lowest carrier frequency), times 220 pF.

    The internally-generated 10 MHz clock is available to the user on pins 13 and 14 as previously described in the description for configuring the 2A as a modulator.

    As before, the recovered baseband signal is obtained at pin 9, and will have the instantaneous value of 1 Volt per each 1 Volt RMS instantaneous carrier level at pin 1. Maximum undistorted signal level is 1 Volt at both pins 1 and 9.

    EXTERNALLY-SUPPLIED 10 MHZ CARRIER

    The model 2A carrier pins 13 and 14 can accept an external 10 MHz Ac-coupled ECL-swing differential signal (must be 50% duty factor within 3%) only if specially modified in manufacture by T-Tech. The modified version omits the quartz crystal, however, and therefore can be used ONLY in the external-carrier mode. Order part number 2A/002A-E.

    PIN KEYING & ORIENTATION

    Note that all pins are spaced 0.2 inches apart except for the closer spacing of 0.1 inch for pins 9, 10, 11. This assures correct insertion into the PC board, and eliminates need for special markings.


    Figure 3: Outline and pin designations.

    MOUNTING

    The 2A must be soldered directly into a master PC board if full carrier frequency range is desired. Teflon-fiberglass material is preferable if operation above 500 MHz is desired, although G10 fiberglass of 0.062 inch thickness may be usable. No ground plane should be provided directly under the 2A bottom surface, but microstripline and ground plane techniques are recommended for the main RF signal path.

    MOUNTING MODEL 2A-C

    Threaded mounting holes are provided in the 2A-C unit along the surface to which the SMA connectors are mounted. (see specs.)

    SPECIFICATIONS
    Power Supplies: + 15 V ~ 150 mA; -15 V ~ 130 mA
    Modulator Transfer Function: 1 Volt RMS carrier @ 50 Ohms per 1 Volt into pin 9 (positive polarity only) Tolerance: 1.5% (or 0.15 dB)
    Detector Feedback Loop
    Bandwidth:
    200 kHz
    Closed-loop Detector Dynamic Range: 1 Volt RMS @ 50 Ohms, down to - 40 dBV for 1 % linearity; Offset variation = - 43 dBV DC
    Modulator Distortion: 0.15% THD at 1 kHz baseband and 95% modulation and RF envelope crests at 1 Volt RMS into 50 Ohms
    Modulator SNR: 70 dB or better after demodulation by a perfect AM detector in a 20 kHz post-detection band, relative to full-scale RF crest output
    Operating Temperature: + 5 to + 50 degrees C for specified performance; usable from - 25 to + 125 C
    Modulator Input Impedance: Resistive (primarily), 1 megOhm within 30% shunted by less than 15pF
    Baseband Output Impedance of Closed Loop Detector Config.: Less than 250 Ohms
    Load Resistance at pin 10 for Detector Configuration: Greater than 1 k Ohm allowable
    Modulator Output Impedance: 50 Ohms, within 9 %
    RF Detector Input Impedance: 50 Ohms nominal; return loss less than 12 dB to 350 MHz, 15 dB to 100 MHz
    RF Detector Response: 10 kHz to 100 MHz within 0.3 dB, to 500 MHz flat within 0.5 dB; 1.5 dB to 1 GHz
    Housing (model 2A): Flame-resistant black encapsulated module
    Housing (model 2A-C): Nickel-plated RF sealed enclosure
    Power dissipated: Approximately 4.2 Watts
    Maximum Detector RF Input Voltages: 2 Volts RMS into 50 Ohms (about 20 dBm)
    Maximum Power Supply: + 16 and -16 V, absolute max.
    Power Supply Immunity: All specs met for supply noise less than 10 mV RMS
    Model 2A-C Dimensions: Metal box = 6" long x 3" high x 1.5" thk Mounting holes (4 each) spaced 1" apart in groups of 2; 5.5" distance between groups; each hole threaded for #6-32 screw; threaded to 1/8" depth
    Model 2A-C SMA Spacing: SMA Connectors spaced 5.375" apart

    Note:
    Specify whether SMA connectors should be dedicated for modulator configuration or for detector configuration. SPECIFY LOWEST CARRIER FREQ. TO BE ENCOUNTERED IF UNIT IS TO BE CONFIGURED AS A DETECTOR. MODEL 2A-C COMES WITH FURTHER INSTRUCTIONS SHOWING CONNECTOR AND FEEDTHROUGH LOCATIONS, ETC.

    Model 2A-C Feedthroughs: Feedthrough connectors for power & GND

    NOTE: All specifications are subject to change. T-TECH reserves the right to make improvements to the product without being obliged to install those improvements in previously sold units. No guarantee of suitability for any given application is implied, n or is the suitability of the unit outside the temperature range specified, or outside the specified voltages, both DC and AC.

    This product contains both patented circuitry and block-diagram approach. Infringement will not be tolerated. However, non-exclusive licensing is available for qualifying O.E.M.'s in the event that they wish to package the product in a different form, or merge the packaging with their own PC boards, hybrids, etc. Contact T-TECH via email, fax, or telephone for details.


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