Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
  • H03F3/189—High-frequency amplifiers, e.g. radio frequency amplifiers
  • H03F3/19—High-frequency amplifiers, e.g. radio frequency amplifiers with semiconductor devices only
  • H03F3/193—High-frequency amplifiers, e.g. radio frequency amplifiers with semiconductor devices only with field-effect devices
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03G—CONTROL OF AMPLIFICATION
  • H03G1/00—Details of arrangements for controlling amplification
  • H03G1/0005—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal
  • H03G1/0035—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal using continuously variable impedance elements
  • H03G1/0052—Circuits characterised by the type of controlling devices operated by a controlling current or voltage signal using continuously variable impedance elements using diodes
  • H03G1/0058—PIN-diodes

Definitions

• the invention relates to a radio receiver comprising a controllable amplifier circuit for amplifying radio signals, which amplifier circuit includes an amplifier element with an input electrode and, coupled thereto, a voltage divider with an impedance and a control element.
• the invention also relates to a controllable amplifier circuit for amplifying radio signals, and to the use of a three-layer semiconductor element as a control element in amplifier circuits.
• Radio receivers often comprise an automatic gain control circuit (AGC-circuit) for amplifying radio signals.
• AGC-circuit automatic gain control circuit
• the object of such an AGC-circuit is to ensure that the amplitude of a signal fed to the output is more or less independent of the amplitude of the input signal supplied by an aerial, since the amplitude of the input signal is very variable and governed, inter alia, by the distance between the radio receiver and the radio transmitter.
• An AGC-circuit generally comprises an amplifier circuit including an amplifier element and a control element which is connected thereto.
• the gain of the amplifier circuit is selected, via the control element, to be such that a signal of constant amplitude is present at the output of the amplifier circuit.
• the control element is an indirectly heated thermistor comprising a combination of a temperature-sensitive resistor and a heating element.
• the resistance value of the temperature-sensitive resistor can be controlled indirectly by varying the current through the heating element.
• the use of such a thermistor has the disadvantage that relatively much power is necessary to control this thermistor.
• the known radio receiver is less suitable for use in embodiments where the supply voltage originates from, for example, a battery or an accumulator.
• Another disadvantage of the known radio receiver is the slowness of the thermistor which, during controlling the resistance value, may cause a substantial delay.
• the radio receiver in accordance with the invention is characterized in that the amplifier circuit can suitably be used to amplify signals having frequencies of approximately 200 kHz, and in that the control element includes a PIN diode.
• the control element includes a PIN diode.
• the use of a PIN diode as the control element has the advantage that relatively little power is necessary to control the resistance value.
• An additional advantage is that in such a configuration the resistance value of a PIN diode can be rapidly controlled.
• PIN diodes behave as control elements with a substantially linear transfer characteristic.
• the resistance value is inversely proportional to the current flowing forward through the PIN diode.
• hp associates application note 904 (15 Feb 66) a description is given of the use of a PIN diode as a control element.
• a PIN diode only behaves like a linear control element if the minority carrier lifetime of the PIN diode substantially exceeds the reciprocal value of the frequency of the applied signal.
• PIN diodes can only suitably be used as variable resistors in microwave applications. In this case, the frequency of the signals to be processed must be at least 10 MHz.
• Fig. 1 shows a block diagram of a radio receiver in accordance with the invention.
• Fig. 2 shows an electrical circuit diagram of an embodiment of an amplifier circuit in accordance with the invention.
• Fig. 3 shows an electrical circuit diagram of an alternative embodiment of an amplifier circuit in accordance with the invention.
• Fig. 4 shows the manufacture and construction of a three-layer semiconductor element for use in a radio receiver in accordance with the invention.
• the signals amplified by the first amplifier circuit 7 are supplied to a second band-pass filter 13 via an output 11 of this first amplifier circuit 7.
• This second bandpass filter 13 has a pass-range between 100 kHz and 1.7 MHz, and it ensures that the so- called image frequencies are suppressed.
• the signals filtered by the second band-pass filter 13 are mixed in a mixer
• the resultant mixed signal has a frequency of 10.7 MHz.
• This mixed signal is supplied to a second amplifier circuit 25 via a third band-pass filter 23.
• Said third band-pass filter 23 has a pass-range between 10.55 and 10.85 MHz (10 dB).
• the signals amplified by the second amplifier circuit 25 are first mixed-down to a frequency of 450 kHz, whereafter they are filtered (pass- range between 445 and 455 kHz, 10 dB) and subsequently demodulated.
• the demodulated signals are amplified once more by a third amplifier circuit 29 and are finally supplied to a loudspeaker 31.
• the AGC detector 15 only becomes operative when the amplitude of the output signal 17 has reached a specific threshold value. If the amplitude of the output signal 17 is above this threshold value, said amplitude of the output signal 17 is maintained at a constant value by means of the AGC detector 15 and the amplifier circuit 7. If, however, the amplitude of the output signal 17 is below said threshold value, the amplifier circuit 7 is not influenced by the AGC detector 15.
• the above-mentioned concept can also suitably be used to realize a radio receiver having a frequency range from 150 kHz to 30 MHz, without tunable input filters being required.
• the first intermediate frequency is selected to be considerably higher than 10.7 MHz as used in the above- described radio receiver.
• a first intermediate frequency for example, of 70 MHz could be used.
• Fig. 2 shows the electrical circuit diagram of an example of the amplifier circuit 7 shown in Fig. 1. Apart from this amplifier circuit 7, the aerial 1 and an electrical circuit diagram of the first band-pass filter 3 are also shown in this Figure.
• the amplifier element is formed by an inverting amplifier 67.
• An impedance 65 and a PIN diode 49 constitute the voltage divider.
• An input electrode 57 of the amplifier element 67 is connected to this voltage divider.
• the PIN diode 49 forms the control element, and the resistance value of the PIN diode can be controlled via a variable current source 51. Said current source 51 is controlled by the output 9 of the AGC detector.
• Fig. 4 shows the manufacture and construction of a three-layer semiconductor element.
• a 380 ⁇ m thick boron-doped silicon wafer having a resistivity of 1100 ⁇ cm (P " material). Boron is diffused onto one side of the wafer. This results in the formation of a P + layer 69 having a C s ( surface concentration) which exceeds 10 19 cm “3 . Phosphorus is diffused to a depth of 30 ⁇ m onto the other side of the wafer. This results in the formation of a N-layer 73, with a C s which exceeds 2.10 19 cm '3 .
• the P " layer 71 of the starting material remaining between the P + layer 69 and the N-layer 73 is also referred to as an I-layer. It is alternatively possible to use an N " layer instead of the P " layer 71.
• the wafer is divided into crystals having a diameter of approximately 1 mm. The use of a suitable etching process causes the upper side to be smaller than the bottom side. The upper side and the lower side of the crystal are both metalized on account of electric connections.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Amplifiers (AREA)
• Circuits Of Receivers In General (AREA)

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• 1998
  • 1998-03-02 EP EP98903248A patent/EP0908007A2/de not_active Withdrawn
  • 1998-03-02 WO PCT/IB1998/000263 patent/WO1998043348A2/en not_active Application Discontinuation

Non-Patent Citations (1)

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